Ammonia separation method and zeolite

Abstract

To provide a method for separating ammonia gas using a zeolite film which is excellent in such separation stability at high temperature as to highly selectively separate ammonia gas from mixed gas composed of a plurality of components containing ammonia gas, hydrogen gas and nitrogen gas and to separate the ammonia gas to a permeation side with high permeability.SOLUTION: There is provided a method for separating ammonia for selectively permeating ammonia gas from mixed gas containing at least ammonia gas, hydrogen gas and nitrogen gas using a zeolite film, and separating the ammonia, in which ammonia gas concentration in the mixed gas is 1.0 vol.% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for separating ammonia from a mixed gas containing multiple components, including ammonia gas, hydrogen gas, and / or nitrogen gas, by selectively allowing ammonia gas to permeate through a zeolite membrane.The present invention also relates to a zeolite membrane that effectively separates ammonia from a mixed gas containing multiple components, including ammonia gas, hydrogen gas, and / or nitrogen gas, even under high-temperature conditions. [Background technology]

[0002] BACKGROUND ART In recent years, membrane separation and concentration methods using membranes such as polymer membranes and zeolite membranes have been proposed as methods for separating gas mixtures. While polymer membranes have the advantage of being easily processable into, for example, flat membranes and hollow fiber membranes, they still have the technical problems of being prone to swelling and having low heat resistance. Furthermore, polymer membranes also have low resistance to reactive chemicals and are prone to degradation by adsorptive components such as sulfides. Furthermore, polymer membranes are prone to deformation under pressure, which reduces their separation performance, making them impractical for ammonia separation under high-temperature conditions, which is one of the objectives of the present invention.

[0003] In response to this, various inorganic membranes have been proposed in recent years, boasting excellent chemical resistance, oxidation resistance, thermal stability, and pressure resistance. Among these, zeolite membranes have been proposed. Zeolite membranes, with their regularly spaced subnanometer pores and molecular sieve properties, are expected to be highly durable separation membranes capable of selectively transmitting specific molecules and separating and concentrating molecules over a wider temperature range than polymer membranes. These zeolite membranes are typically used as zeolite membrane composites, in which zeolite is formed in a membrane-like form on an inorganic support. For example, it has been found that using a reaction mixture with a specific composition to form a zeolite membrane on a porous support by hydrothermal synthesis improves the crystal orientation of the zeolite crystallized on the support, resulting in the formation of a dense zeolite membrane that combines practically sufficient throughput and separation performance in the separation of a mixture of organic compounds and water (Patent Documents 1 to 3).

[0004] Generally, zeolite membranes for gas separation are known, such as A-type membranes, FAU membranes, MFI membranes, SAPO-34 membranes, and DDR membranes. Zeolite membrane composites for gas separation that exhibit high throughput and separation performance have been proposed for separating gases emitted from thermal power plants, the petrochemical industry, and the like, such as carbon dioxide and nitrogen, carbon dioxide and methane, hydrogen and hydrocarbons, hydrogen and oxygen, hydrogen and carbon dioxide, nitrogen and oxygen, and paraffins and olefins (e.g., Patent Document 4).

[0005] Meanwhile, membrane separation has also been expected to be applied to the separation of ammonia gas from hydrogen gas and nitrogen gas in the present invention. For example, membrane separation has been expected to be applied to the ammonia production process by the Haber-Bosch process, an industrially important process. A characteristic of the Haber-Bosch process is that the ammonia production reaction is an equilibrium reaction. Although high-pressure, low-temperature conditions are thermodynamically favorable, high-pressure, high-temperature production conditions are generally required to ensure catalytic reaction rates. Furthermore, because unreacted hydrogen and nitrogen gases coexist with ammonia gas in the resulting mixed gas, the process of recovering the product ammonia gas from the resulting mixed gas requires cooling the mixed gas to approximately -20°C to -5°C to condense and separate the ammonia (Non-Patent Documents 1 and 2). In particular, due to the constraints of the reaction equilibrium, the ammonia gas concentration in the resulting mixed gas is inevitably low. This means that the ammonia cooling and separation process from the resulting mixed gas is characterized by poor cooling efficiency and significant energy consumption. Furthermore, in this process, it is necessary to separate a large amount of mixed gas of hydrogen gas and nitrogen gas from the produced mixed gas and recycle it to the reactor as a raw material gas, and it is also necessary to pressurize a large amount of cooled, unreacted mixed gas to a predetermined pressure and to heat it to the reaction temperature, which further increases energy consumption during production.

[0006] In order to avoid such an energy-intensive process, a process has been proposed in which the cooling condensation separation method used in the purification process is replaced with a separation method using an inorganic membrane to efficiently recover high-concentration ammonia gas (Patent Documents 7 and 8). Methods for separating a mixed gas containing a high concentration of ammonia gas from a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas include: 1) a method using a separation membrane to selectively allow hydrogen gas and / or nitrogen gas to permeate from the mixed gas; and 2) a method using a separation membrane to selectively allow ammonia gas to permeate from the mixed gas. As methods for selectively permeating hydrogen gas and / or nitrogen gas, methods using polycrystalline layers of various zeolites (Patent Document 5) and methods using molecular sieve films (Patent Document 6) have been proposed. Patent Document 7 also describes methods for selectively permeating hydrogen gas and / or nitrogen gas and methods for selectively permeating ammonia gas, proposing a separation method in which at least one of hydrogen gas, nitrogen gas, and ammonia gas is separated from a product gas, which is a mixture of hydrogen gas, nitrogen gas, and ammonia gas, using a separation membrane in which a silica-containing layer is laminated on a ceramic substrate. Specifically, Patent Document 7 shows a schematic flowchart of ammonia production using a separation membrane. Because hydrogen gas selectively permeates silica membranes under high-temperature conditions, the separation membranes are installed in two stages, with hydrogen gas separated into the permeate side by the first-stage separation membrane, and ammonia gas separated into the permeate side by the second-stage separation membrane from the nitrogen gas and ammonia gas that did not permeate the first-stage separation membrane. On the other hand, it has been shown that the conditions for separating ammonia gas from a mixed gas of hydrogen gas and ammonia gas require a low temperature condition of, for example, 50°C, and that the ammonia gas concentration in the mixed gas must exceed 60 mol%.

[0007] On the other hand, as a method for selectively permeating ammonia gas, in addition to Patent Document 7, an efficient ammonia separation method has been proposed in which a specific zeolite having an 8-membered oxygen ring is used to separate ammonia gas from a mixture of ammonia gas and hydrogen gas and / or nitrogen gas (Patent Document 8). This method proposes a technique for separating ammonia gas by the molecular sieving effect of a specific zeolite membrane composite designed using the pore size of the zeolite. Generally, ammonia is used as a probe molecule adsorbed to acid sites in the temperature-programmed desorption method to measure the acidity of zeolites. Although the peak top temperature reaches approximately 480°C, the adsorbed ammonia desorbs upon heating (Non-Patent Document 3). However, Patent Document 8 discloses that the ammonia gas permeability can be controlled by controlling the ammonia adsorption capacity of zeolites through ion exchange. Patent Document 8 cites the blockage of zeolite pores by ammonia during ammonia gas permeation as a problem, and discloses a technology to avoid this problem in the examples. Therefore, the separation technology of Patent Document 8 proposes that a method of using zeolite that suppresses the adsorption of ammonia to prevent clogging of the pores by ammonia while allowing ammonia gas to permeate by the molecular sieve action utilizing the pore size of the zeolite is effective.

[0008] On the other hand, in recent years, a groundbreaking manufacturing process has been developed for ammonia synthesis. Specifically, a manufacturing process that uses an electride catalyst carrying ruthenium metal and exhibits extremely high catalytic activity even under low-temperature conditions (340 to 400°C) has been reported (Patent Document 9). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-121040 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-121045 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-121854 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-066242 [Patent Document 5] Special Publication No. 10-506363 [Patent Document 6] Special Publication No. 2000-507909 [Patent Document 7] Japanese Patent Application Laid-Open No. 2008-247654 [Patent Document 8] Japanese Patent Application Laid-Open No. 2014-058433 [Patent Document 9] International Publication No. 2015 / 129471 [Non-patent literature]

[0010] [Non-Patent Document 1] Chemical Society of Japan, 6th Edition, Chemical Handbook, Applied Chemistry, Vol. I, Maruzen Co., Ltd. (2003), p. 581 [Non-patent document 2] Chemical Engineering Society, Chemical Process Collection 1st Edition, Tokyo Kagaku Dojin, p153 [Non-patent document 3] Naonobu Katada, Miki Niwa, Zeolite Vol.21 No.2, Zeolite Society (2004), p45-52 Summary of the Invention [Problem to be solved by the invention]

[0011] However, in the method of selectively permeating hydrogen gas and / or nitrogen gas from a mixed gas containing hydrogen gas, nitrogen gas, and ammonia gas, only hydrogen gas and / or nitrogen gas are recovered through the separation membrane. The essential problem with this method is that it first separates hydrogen gas and / or nitrogen gas from the mixed gas containing a relatively high concentration of ammonia gas. In other words, in the process of separating hydrogen gas and / or nitrogen gas, a considerable amount of ammonia gas also permeates along with the permeating hydrogen gas and / or nitrogen gas. Therefore, an economical process cannot be realized unless a considerable amount of the permeating ammonia is recovered. For example, when adopting the technology of Patent Document 7, in order to complete an economical process, a step of separating ammonia gas from the high-concentration hydrogen mixed gas containing ammonia gas that permeates through the first-stage separation membrane and from the mixed gas of nitrogen gas and ammonia gas that does not permeate is essential. That is, this method is not only a complicated process in which ammonia gas must be separated from a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas in at least two stages, but also requires a step of recovering ammonia from both the mixed gas that has permeated in the first stage and the mixed gas that has not permeated, making the process even more complicated. To essentially solve these problems, it becomes necessary to separate hydrogen gas and nitrogen gas from a mixed gas containing relatively high concentrations of hydrogen gas and nitrogen gas and / or a mixed gas containing relatively low concentrations of ammonia gas, but such a process cannot be a productive ammonia production process and is not realistic. Furthermore, the process proposed in Patent Document 7 for recycling hydrogen gas separated to the permeate side through a first-stage membrane under high-temperature conditions has the problem of requiring energy to pressurize the hydrogen gas. Furthermore, the separation of nitrogen gas and ammonia gas through a second-stage membrane does not provide sufficient ammonia gas permeability, which may result in a large membrane area. Furthermore, in the method of Patent Document 7 for separating hydrogen gas, which serves as a feed gas, from a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas under high-temperature conditions, for example, when a separation membrane according to one embodiment of the present invention is directly attached to an ammonia synthesis reactor to synthesize ammonia, the feed gas permeates, which makes the reaction unfavorable due to the above-mentioned reaction equilibrium constraints, and it is therefore impossible to produce high-concentration ammonia gas. From these perspectives, the method of selectively permeating hydrogen gas and / or nitrogen gas from a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas using such a separation membrane increases energy costs during production and makes the process more complicated, making it difficult to find any advantage in introducing a separation membrane into an ammonia production process. In contrast, a method for selectively permeating ammonia gas from a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas using a separation membrane is effective in solving the above-mentioned various problems. However, the ammonia gas separation method using a separation membrane laminated with a silica-containing layer proposed in Public Document 7 requires the use of a mixed gas with an ammonia gas concentration of more than 60 mol% and cooling the mixed gas to 50°C to exhibit the blocking effect of ammonia. Furthermore, the ammonia gas separation ability is such that ammonia gas is somewhat more permeable than hydrogen gas. In such a process, there is a problem of how to obtain a mixed gas with an ammonia gas concentration of more than 60 mol%. Even if such a mixed gas could be obtained, the cooling requires a large amount of energy, making it difficult to complete an economical process. On the other hand, the method proposed in Patent Document 8 for separating ammonia gas from a mixture of ammonia gas and hydrogen gas and / or nitrogen gas using a specific zeolite having an 8-membered oxygen ring is not subject to the above-mentioned constraints because it allows ammonia gas to permeate, and could be an effective method applicable to industrial processes. However, in the ammonia separation method proposed in Patent Document 8 using the molecular sieving action of zeolite, which utilizes the pore size of the zeolite, the permeance ratio (ideal separation factor) of ammonia gas to nitrogen gas achieved is only about 14 at most, and the permeation performance is insufficient. Furthermore, Patent Document 8 proposes that ammonia gas is basically selectively permeated from a mixture of hydrogen gas, nitrogen gas, and ammonia gas by calculating the permeance ratios of hydrogen gas and ammonia gas to nitrogen gas individually and comparing these ratios. However, the permeation performance is insufficient, particularly in terms of the permeance ratio of ammonia gas to hydrogen gas, and the effectiveness of ammonia gas separation using the molecular sieving action utilizing the zeolite pore size is limited. Furthermore, in Patent Document 8, ammonia gas is separated from a mixture of nitrogen and ammonia gas at 140°C. However, when comparing the permeance of various gases before and after ammonia gas permeation, the permeance values ​​of all gases increase after permeation, and there remains the issue of impaired durability of the zeolite membrane even at relatively low temperatures such as 140°C. To address these issues, in order to efficiently permeate ammonia gas using a zeolite membrane, the composition of the feed mixture gas and the temperature during separation must also be appropriately combined, because ammonia is inherently adsorbable to zeolite. However, Patent Document 8 does not describe or propose appropriate separation conditions, and does not demonstrate a method for separating ammonia from a mixture of hydrogen gas, nitrogen gas, and ammonia gas, or a mixture of hydrogen gas and ammonia gas. Meanwhile, in the ammonia production process, a highly active ammonia production catalytic process has been reported in recent years even under low temperature and low pressure conditions, as in Patent Document 9, and this process is expected to reduce energy consumption during production. However, because the ammonia production reaction is an equilibrium reaction as described above, this innovative production process alone cannot produce a mixed gas containing ammonia gas at a high concentration exceeding the equilibrium composition due to the constraints of reaction equilibrium, and therefore cannot essentially solve the problem of reducing energy consumption during production, including the above-mentioned processes of recovering the produced ammonia and recycling the raw material gas.

[0012] The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a method for separating ammonia, which can separate ammonia gas from a mixed gas consisting of a plurality of components including ammonia gas, hydrogen gas, and / or nitrogen gas with high selectivity and high permeability by causing ammonia gas to permeate through a zeolite membrane, and which further has excellent high-temperature separation stability and long-term operational stability. [Means for solving the problem]

[0013] In order to solve the above problems, the present inventors have further investigated the separation of ammonia using a zeolite membrane, and have found that when the ammonia gas concentration in a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas exceeds a specific amount, the ammonia gas permeates through the zeolite membrane. We have found that the selectivity is significantly improved. Furthermore, we have found that by using one embodiment of the present invention, it is possible to stably maintain ammonia gas separation performance even under temperature conditions exceeding 200°C. Even more surprisingly, we have found that a similar effect is also achieved with zeolites such as MFI, which have pore sizes large relative to the molecular sizes of hydrogen, nitrogen, and ammonia molecules. That is, Patent Document 8 proposes a method for separating ammonia by designing an ammonia gas separation membrane that avoids blockage of the pores of zeolites, since permeating ammonia gas causes the pores to become blocked. In contrast, we have found that, in the present invention, a method for actively adsorbing ammonia onto zeolites significantly improves ammonia gas separation performance and separation stability, leading to the completion of the present invention. Furthermore, unlike the silica membrane proposed in Patent Document 7, we have found that when a zeolite membrane is used, ammonia separation performance can be stably maintained even under high-temperature conditions exceeding 50°C and even 200°C. This has led to the completion of the present invention.

[0014] The first embodiment of the present invention (Invention A) was achieved based on this finding and provides the following.

[0015] [A1] A method for separating ammonia by selectively allowing ammonia gas to permeate through a zeolite membrane from a mixed gas containing at least ammonia gas, hydrogen gas, and nitrogen gas, wherein the ammonia gas concentration in the mixed gas is 1.0% by volume or more. [A2] The method for separating ammonia according to [A1], wherein the volume ratio of hydrogen gas to nitrogen gas in the mixed gas is 0.2 or more and 3 or less. [A3] The method for separating ammonia according to [A1] or [A2], wherein the temperature during separation of ammonia is higher than 50°C and not higher than 500°C. [A4] The method for separating ammonia according to any one of [A1] to [A3], wherein the zeolite constituting the zeolite membrane is an RHO-type zeolite or an MFI-type zeolite. [A5] A method for separating ammonia, comprising a step of producing ammonia from hydrogen gas and nitrogen gas, and separating ammonia from a mixed gas containing ammonia gas obtained in the production step by the separation method according to any one of [A1] to [A4].

[0016] Furthermore, in order to solve the above-mentioned problems, the present inventors further investigated the separation of ammonia gas using zeolite membranes. They found that, although existing zeolite membranes for ammonia gas separation can separate ammonia gas more selectively and efficiently than existing silica membranes, their separation performance was limited to a permeance ratio (ideal separation factor) of only about 14 for ammonia gas and nitrogen gas. They also found that the use of a zeolite membrane with a surface having a specific molar ratio of nitrogen atoms to Al atoms, as determined by X-ray photoelectron spectroscopy (XPS), significantly improves ammonia gas separation performance. They also found that the present invention can stably maintain ammonia gas separation performance even under high-temperature conditions. Specifically, they found that, in order to separate ammonia gas from a mixed gas consisting of ammonia gas and multiple components, including hydrogen gas and / or nitrogen gas, with high selectivity and permeability, even under high-temperature conditions, it is necessary to use a zeolite membrane with a surface containing a specific molar ratio of nitrogen atoms to Al atoms. This finding led to the completion of the present invention. The second embodiment of the present invention (Invention B) was achieved based on this finding and provides the following. [B1] A zeolite membrane characterized in that the molar ratio of nitrogen atoms to Al atoms determined by X-ray photoelectron spectroscopy under the following measurement conditions is 0.01 or more and 4 or less. (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method [B2] The zeolite membrane is a zeolite membrane treated with an ammonium salt. The zeolite membrane according to [B1]. [B3] The zeolite membrane according to [B2], characterized in that the zeolite membrane is further treated with aluminum nitrate. [B4] The zeolite membrane according to any one of [B1] to [B3], wherein the zeolite is an RHO-type zeolite. [B5] The zeolite membrane according to any one of [B1] to [B4], which is used for separating ammonia gas. [B6] A method for separating ammonia, comprising permeating ammonia gas through the zeolite membrane according to any one of [B1] to [B5] and separating the ammonia gas from a mixed gas containing at least ammonia gas and hydrogen gas and / or nitrogen gas. [B7] The ammonia obtained in the process of producing ammonia from hydrogen gas and nitrogen gas is [B 6] A method for separating ammonia by the separation method described in [6].

[0017] Furthermore, the present inventors further investigated the separation of ammonia gas using zeolite membranes in order to solve the above-mentioned problems. They found that, although existing zeolite membranes for separating ammonia gas can separate ammonia gas more selectively and efficiently than existing silica membranes, their separation performance suffers from problems such as a permeance ratio (ideal separation factor) of ammonia gas to nitrogen gas of only about 14 and the durability of the zeolite membrane is impaired even at relatively low temperatures such as 140°C. However, they found that a zeolite membrane having a surface with a specific molar ratio of Si atoms to Al atoms, as determined by X-ray photoelectron spectroscopy (XPS), exhibits remarkable ammonia separation performance and improved separation stability at high temperatures. Specifically, they found that, in order to separate ammonia gas from a mixed gas consisting of multiple components, including ammonia gas, hydrogen gas, and / or nitrogen gas, with high selectivity and permeability even at high temperatures, it is necessary to use a zeolite membrane having a surface containing a specific molar ratio of Si atoms to Al atoms. This finding led to the completion of the present invention. The third embodiment of the present invention (Invention C) was achieved based on this finding and provides the following. [C1] A zeolite membrane characterized in that the molar ratio of Si atoms to Al atoms determined using X-ray photoelectron spectroscopy under the following measurement conditions is 2.0 or more and 10 or less. (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method [C2] The zeolite membrane according to [C1], characterized in that the molar ratio of nitrogen atoms to Al atoms, determined using X-ray photoelectron spectroscopy under the following measurement conditions, is 0.01 or more and 4 or less. (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method [C3] The zeolite membrane according to [C1] or [C2], wherein the zeolite membrane is a zeolite membrane treated with an aluminum salt. [C4] The zeolite membrane according to any one of [C1] to [C3], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt. [C5] The zeolite membrane according to any one of [C1] to [C4], characterized in that the zeolite membrane is treated with an ammonium salt and then with an aluminum salt. [C6] The zeolite membrane according to any one of [C1] to [C5], wherein the zeolite is an RHO-type zeolite. [C7] The zeolite membrane according to any one of [C1] to [C6], wherein the zeolite membrane is used for separating ammonia. [C8] A mixed gas containing at least ammonia gas, hydrogen gas, and / or nitrogen gas A method for separating ammonia, comprising permeating and separating ammonia gas through the zeolite membrane according to any one of [C1] to [C7]. [C9] A method for separating ammonia, which comprises separating ammonia obtained in a process for producing ammonia from hydrogen gas and nitrogen gas by the separation method according to [C8].

[0018] Furthermore, in order to solve the above-mentioned problems, the present inventors further investigated the separation of ammonia gas using zeolite membranes and found that the use of a zeolite membrane having a surface in which the molar ratio of alkali metal atoms to Al atoms, as determined by X-ray photoelectron spectroscopy (XPS), falls within a specific range can improve permeability while maintaining high ammonia gas separation selectivity. Furthermore, the present inventors found that the present invention can stably maintain ammonia gas separation performance even under high-temperature conditions. Specifically, the present inventors discovered that, among various zeolite membranes, a zeolite membrane having a molar ratio surface containing a specific molar ratio of alkali metal atoms to Al atoms is necessary to separate ammonia gas with high selectivity and high permeability even under high-temperature conditions, in order to separate ammonia gas from a mixed gas consisting of multiple components including ammonia gas, hydrogen gas, and / or nitrogen gas, and thus completed the present invention. The fourth embodiment of the present invention (Invention D) was achieved based on these findings and provides the following. [D1] A zeolite membrane characterized in that the molar ratio of alkali metal atoms to Al atoms determined by X-ray photoelectron spectroscopy under the following measurement conditions is 0.01 or more and 0.070 or less. (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method [D2] The zeolite membrane according to [D1], characterized in that the molar ratio of nitrogen atoms to Al atoms determined by X-ray photoelectron spectroscopy under the following measurement conditions is 0.01 or more and 4 or less. (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method [D3] The zeolite membrane according to [D1] or [D2], wherein the zeolite membrane is a zeolite membrane treated with an alkali metal salt. [D4] The zeolite membrane according to any one of [D1] to [D3], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt. [D5] The zeolite membrane according to any one of [D1] to [D4], characterized in that the zeolite membrane is a zeolite membrane which has been treated with an ammonium salt and then with an alkali metal salt. [D6] The zeolite membrane according to any one of [D1] to [D5], wherein the zeolite is an RHO-type zeolite. [D7] The zeolite membrane according to any one of [D1] to [D6], wherein the zeolite membrane is used for separating ammonia gas. [D8] A method for separating ammonia, comprising permeating ammonia gas through the zeolite membrane according to any one of [D1] to [D7] and separating the ammonia gas from a mixed gas containing at least ammonia gas and hydrogen gas and / or nitrogen gas. [D9] A method for separating ammonia, which comprises separating ammonia obtained in a process for producing ammonia from hydrogen gas and nitrogen gas by the separation method according to [D8].

[0019] Furthermore, in order to solve the above-mentioned problems, the present inventors further investigated the separation of ammonia gas using a zeolite membrane composite. As a result, they found that although zeolite membranes can separate ammonia gas more selectively and efficiently than existing silica membranes, when a zeolite membrane composite formed from a CHA-type zeolite such as that proposed in Patent Document 8 is used, in which the rate of change in thermal shrinkage at 200°C and 300°C relative to 30°C changes monotonically to 0.13% and 0.30% (c-axis direction), as described in Reference Example E1 of the present invention, the ammonia gas separation performance decreases, particularly in the temperature range above 200°C, and there is room for improvement. This is presumably because cracks occur at the grain boundaries of the zeolite due to thermal contraction of the zeolite, and gas passes through these cracks. However, even in the case of a zeolite such as the RHO zeolite described in Example E of the present invention, which exhibits a nonlinear thermal expansion / contraction behavior with temperature, with a rate of change in thermal contraction rate at 200°C from 30°C being 1.55%, which is significantly smaller than that of CHA zeolite, it has been found that ammonia can be separated efficiently and with high selectivity under high-temperature conditions exceeding 200°C, so long as the rate of change in thermal expansion rate at 300°C is approximately 0.02%. Specifically, the present inventors discovered that, in order to achieve high-selectivity and high-permeability separation of ammonia gas from a gas mixture consisting of multiple components, including ammonia gas and hydrogen gas and / or nitrogen gas, under high-temperature conditions, it is necessary to use a zeolite membrane composite formed from a zeolite that exhibits a thermal expansion change rate in a specific temperature range, among various zeolite membrane composites. This finding led to the completion of the present invention. Note that, in this specification, the term "change rate of thermal expansion coefficient" refers to the rate of change of thermal expansion coefficient along the axis in which the rate of change of thermal expansion coefficient is greatest. For example, CHA-type zeolite has different thermal expansion / contraction rates along the a-axis and c-axis, but the rate of change is greater along the c-axis. Therefore, the rate of change of thermal expansion coefficient of CHA is the rate of change of thermal expansion coefficient along the c-axis. Similarly, MFI-type zeolite has different thermal expansion / contraction rates along the a-axis, b-axis, and c-axis, but the rate of change is greater along the c-axis. Therefore, the rate of change of thermal expansion coefficient of MFI in this specification refers to the rate of change of thermal expansion coefficient along the c-axis. On the other hand, RHO-type zeolite has a cubic crystal system, and all of its crystal axes are equivalent, so the rate of change in the thermal expansion coefficient is constant regardless of the axial direction. The fifth embodiment (Invention E) of the present invention was achieved based on this finding, and provides the following. [E1] A zeolite membrane composite for ammonia separation containing a zeolite, wherein the rate of change in the thermal expansion coefficient of the zeolite at 300°C relative to the thermal expansion coefficient at 30°C is within ±0.25%, and the rate of change in the thermal expansion coefficient of the zeolite at 400°C relative to the thermal expansion coefficient at 30°C is within ±0.35%. [E2] The zeolite membrane composite for ammonia separation according to [E1], wherein the rate of change in the thermal expansion coefficient of the zeolite at 400°C relative to the thermal expansion coefficient at 30°C relative to the thermal expansion coefficient at 300°C is within ±120%. [E3] The zeolite membrane composite for ammonia separation according to [E1] or [E2], wherein the zeolite is an RHO-type zeolite or an MFI-type zeolite. [E4] The SiO2 / Al2O3 molar ratio of the zeolite is 6 or more and 500 or less, [E1 ] to [E3]. The zeolite membrane composite for ammonia separation according to any one of [E4] to [E5]. [E5] A method for separating ammonia, comprising separating ammonia from a gas mixture containing at least ammonia gas, and hydrogen gas and / or nitrogen gas, using the zeolite membrane composite for ammonia gas separation according to any one of [E1] to [E4]. [E6] A method for separating ammonia, which comprises separating ammonia obtained in a process for producing ammonia from hydrogen gas and nitrogen gas by the separation method according to [E5]. The second to fifth embodiments are particularly technologies relating to an ammonia gas separation membrane that contribute to the completion of an energy-saving ammonia production process, and are also technologies that can be expected to be applied to a reactive separation type ammonia production process, which is one aspect of the present invention. [Effects of the Invention]

[0020] According to the first embodiment of the present invention, ammonia gas can be continuously and efficiently separated on the permeation side with high selectivity from a mixed gas consisting of multiple components including ammonia gas, hydrogen gas, and nitrogen gas. Furthermore, according to the present invention, the membrane can be used stably even under high-temperature conditions exceeding 50°C and even 200°C, so that the ammonia gas permeability is high. As a result, the membrane area required for separation can be reduced, and ammonia separation can be achieved at low cost using small-scale facilities. A specific example of the application of the zeolite membrane of the present invention is the Haber-Bosch process. In an ammonia production process, for example, when recovering ammonia from a mixed gas consisting of multiple components including ammonia gas, hydrogen gas, and nitrogen gas recovered from a reactor, ammonia can be separated more efficiently than with conventional cooling condensation separation methods, and the cooling energy required for ammonia condensation can be reduced. In another embodiment, the zeolite membrane of the present invention can stably separate ammonia gas from a mixed gas composed of multiple components including ammonia gas, hydrogen gas, and nitrogen gas to the permeation side with high permeability even under high-temperature conditions. Therefore, a reactive separation-type ammonia production process can be designed in which the zeolite membrane of the present invention is installed in a reactor and ammonia gas is produced while the produced ammonia gas is simultaneously recovered. According to the second to fifth embodiments of the present invention, ammonia gas can be continuously and efficiently separated to the permeate side with high selectivity from a mixed gas consisting of multiple components including ammonia gas and hydrogen gas and / or nitrogen gas, even under high-temperature conditions. Furthermore, the zeolite membrane of the present invention can be used stably under higher-temperature conditions, and therefore has high ammonia gas permeability. As a result, the membrane area required for separation can be reduced, and ammonia gas separation can be achieved with small-scale facilities at low cost. A specific application example of the zeolite membrane of the present invention is in an ammonia production process, such as the Haber-Bosch process, where ammonia is recovered from a mixed gas consisting of multiple components including ammonia gas, hydrogen gas, and / or nitrogen gas recovered from a reactor.Since ammonia can be separated more efficiently than with conventional cooling condensation separation methods, the cooling energy required for ammonia condensation can be reduced. In another embodiment, the zeolite membrane of the present invention can stably separate ammonia gas from a mixed gas composed of multiple components including ammonia gas, hydrogen gas, and / or nitrogen gas at high permeability to the permeate side even under high-temperature conditions. Therefore, a reactive separation-type ammonia production process can be designed in which the zeolite membrane of the present invention is installed in a reactor and ammonia gas is produced while the produced ammonia gas is simultaneously recovered. In particular, application of the first to fifth embodiments to a reactive separation-type ammonia production process is expected to not only lower the reaction pressure during ammonia production, but also significantly improve the conversion rate of the raw material gas to ammonia gas, thereby reducing the amount of recovered gas recycled to the reactor during production. In other words, the reactive separation-type ammonia production process using the zeolite membrane of the present invention makes it possible to reduce energy consumption during production, enabling economical, energy-saving ammonia production. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an apparatus used in an ammonia gas separation test in the Examples. [Figure 2] 1 shows the results of measuring the thermal expansion coefficient of the zeolite according to Example E4 at different temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following describes in more detail the embodiments of the present invention, but the following description of the constituent elements is merely an example of the embodiment of the present invention, and the present invention is not limited to these contents, and various modifications can be made within the scope of the gist. Note that the zeolite in this specification is a zeolite defined by the International Zeolite Association (IZA). The structure is characterized by X-ray diffraction data. In this specification, a "porous support-zeolite membrane composite in which a zeolite membrane is formed on a porous support" may be referred to as a "zeolite membrane composite" or a "membrane composite." In addition, a "porous support" may be abbreviated simply as a "support," and an "aluminosilicate zeolite" may be abbreviated simply as a "zeolite." In this specification, "hydrogen gas," "nitrogen gas," and "ammonia gas" may be abbreviated simply as "hydrogen," "nitrogen," and "ammonia," respectively. Meanwhile, ammonia separation in the present invention refers to obtaining a mixed gas containing a higher concentration of ammonia gas from a mixed gas containing ammonia gas.

[0023] The first embodiment (Invention A) of the ammonia separation method of the present invention is a method for stably and continuously separating ammonia from a mixed gas consisting of multiple components including at least ammonia, hydrogen, and nitrogen using a zeolite membrane with high permeability and high selectivity to the permeation side, and is characterized in that ammonia is selectively permeated and separated from a mixed gas of hydrogen and nitrogen containing a specific amount or more of ammonia. Another embodiment of the method for separating ammonia of the present invention is characterized in that a mixed gas consisting of ammonia and multiple components including hydrogen and / or nitrogen is brought into contact with a specific zeolite membrane, and ammonia is selectively permeated and separated from the mixed gas. Details are explained below.

[0024] <Ammonia manufacturing method> The ammonia separation method according to this embodiment can be effectively used to efficiently separate ammonia from a mixed gas containing at least ammonia, hydrogen, and nitrogen, and therefore is effective when used in combination with an ammonia production method that produces such a mixed gas. That is, in addition to an ammonia production method that includes a first step of producing ammonia from hydrogen and nitrogen and a second step of separating the ammonia produced in the first step by an ammonia separation method described below, and in which ammonia is separated from the ammonia produced in the first step in the second step, a preferred embodiment of the present invention also includes an ammonia production method in which the first and second steps proceed in a single reactor. Proceeding the first and second steps in a single reactor means that the first and second steps proceed simultaneously. In other words, in one embodiment of the present invention, ammonia gas is produced from hydrogen gas and nitrogen gas in a vessel, and ammonia can be efficiently produced in the vessel while ammonia is separated from a mixed gas containing the produced ammonia gas. There are no particular limitations on the industrial production method of ammonia, but the Haber-Bosch process is one example. This process essentially uses iron oxide as a catalyst. Nitrogen and hydrogen gas react over the catalyst at high temperatures and pressures of 300–500°C and 10–40 MPa to produce ammonia. The ammonia produced in the reactor outlet gas is cooled, condensed, and separated for recovery as a product, while unreacted nitrogen and hydrogen gas are separated and recycled as feed gas. In the 1980s, a Ru-based supported catalyst was developed as an improvement over the Haber-Bosch process, enabling ammonia production under lower pressures. A process combining this with the Haber-Bosch process has also been commercialized, but the basic production process has remained unchanged for over 100 years. Thus, industrial ammonia production catalysts are generally divided into iron-based and Ru-based catalysts. The theoretical molar ratio of hydrogen to nitrogen (H / N) is ideal for ammonia production. However, because Ru-based catalysts are prone to catalyst poisoning by hydrogen, production conditions with a lower molar ratio are preferred. Considering this point, although not particularly limited, the ammonia production catalytic process to be combined with the ammonia separation technology of the present invention is preferably a process using a Ru-based catalyst, since this approaches the preferred volume ratio of hydrogen gas / nitrogen gas contained in the feed gas in ammonia separation, which will be described later, and this combination makes it possible to reduce the amount of hydrogen permeating during separation of the produced ammonia.

[0025] <Method for separating ammonia> A first embodiment of the method for separating ammonia of the present invention is characterized in that a mixed gas consisting of ammonia, hydrogen, and a plurality of components including nitrogen is brought into contact with the zeolite membrane, and ammonia is selectively permeated and separated from the mixed gas. The method for separating ammonia of the present invention is characterized in that a mixed gas consisting of ammonia and a plurality of components including hydrogen and / or nitrogen is brought into contact with the zeolite membrane using a specific zeolite membrane, and ammonia is selectively permeated and separated from the mixed gas. As described above, according to the present invention, ammonia gas is produced from hydrogen gas and nitrogen gas in a reactor. Ammonia can be efficiently produced and recovered by producing ammonia gas through a zeolite membrane in the reactor, and allowing the produced ammonia gas to permeate through the membrane.

[0026] In the present invention, ammonia separation using a zeolite membrane is primarily based on the hopping mechanism of ammonia within the zeolite pores, but separation as a molecular sieve is also utilized by controlling the pore size of the zeolite membrane using adsorbed ammonia, ammonium ions, etc. The former action allows ammonia, which has a high affinity for the zeolite membrane, to permeate the zeolite membrane with high selectivity, and the latter action efficiently separates gas molecules with sizes equal to or larger than the effective pore size of the zeolite membrane to which ammonia is adsorbed from gas molecules with sizes smaller than this, thereby enabling more effective ammonia separation.

[0027] The reason for the significant improvement in ammonia permeation selectivity due to the ammonia hopping mechanism within the zeolite pores is still unclear, but it is believed that such zeolite membranes narrow the pore size due to the adsorbed ammonia and ammonium ions contained within the zeolite, thereby reducing the permeation rate of hydrogen gas, which has a small molecular size. This effect also occurs when using zeolites with pore sizes larger than the molecular sizes of hydrogen, nitrogen, and ammonia gases, as the pores of the zeolite membrane are narrowed, thereby inhibiting the permeation of nitrogen and hydrogen gases. On the other hand, the adsorbed ammonia and ammonium ions contained within the zeolite pores can cause ammonia to hop within the pores due to adsorption / desorption, and this behavior results in the selective separation of ammonia gas.

[0028] The first embodiment of the present invention (Invention A) utilizes the adsorption of ammonia onto zeolite as described above, and is characterized by the separation of ammonia based on the hopping mechanism of ammonia within the zeolite pores. Therefore, the ammonia gas concentration in the feed gas containing water gas, nitrogen gas, and ammonia gas must be controlled to a specific level or higher. It is important that the ammonia gas concentration in the feed gas be 1.0 vol% or higher. This is because the ammonia adsorbed onto the zeolite is in an adsorption equilibrium relationship with ammonia gas in the gas phase, and the adsorption capacity of ammonia onto the zeolite is highly dependent on the ammonia gas concentration in the feed gas. As shown in the comparative examples of the present invention, even at ammonia gas concentrations below 1.0 vol%, some ammonia permeation selectivity is exhibited, but the effect is not significant. Therefore, in the present invention, it is important to use a feed gas with an ammonia gas concentration of 1.0 vol% or higher. Contacting such a gas with a zeolite membrane under pressurized conditions effectively induces ammonia adsorption onto the zeolite, thereby improving the separation selectivity of ammonia from the feed gas. Furthermore, when a feed gas having an ammonia gas concentration of 1.0% by volume or more is used, the ammonia gas concentration in the feed gas is increased, and therefore the permeation rate is also improved. When the ammonia gas concentration in the mixed gas is set to 1.0% by volume or more, ammonia may be produced under conditions such that the ammonia gas concentration in the mixed gas obtained during ammonia production is 1.0% by volume or more. Among the above, the ammonia gas concentration in the feed gas is preferably 2.0% by volume or more, more preferably 3.0% by volume or more, and particularly preferably 5.0% by volume or more. While there is no particular upper limit, the higher the ammonia gas concentration in the feed gas, the better the separation performance, so it is usually less than 100% by volume. However, due to the need to separate ammonia, it is generally 80% by volume or less, preferably 60% by volume or less, and more preferably 40% by volume or less. The ammonia concentration in the feed gas is determined by sampling the feed gas, analyzing its components, and expressing the ammonia molar fraction as the same as volume %. The volume percentages of other gases are also considered to be volume percentages in terms of molar fractions. On the other hand, when separating ammonia in combination with an ammonia production process, the concentration is below the equilibrium concentration of ammonia produced under the production process conditions. The ammonia separation technology using the present invention is a process for separating ammonia from a supply gas, as opposed to known methods for selectively permeating hydrogen gas and / or nitrogen gas from a mixed gas of hydrogen, nitrogen, and ammonia, and is therefore advantageous for separating ammonia from a mixed gas containing a high concentration of ammonia. In addition, after that, if necessary, Even when a process for recovering hydrogen gas from the non-permeated mixed gas that did not permeate the membrane is adopted as needed, the design is such that hydrogen is recovered from the mixed gas in which the ammonia gas concentration has been sufficiently reduced, and therefore the above-mentioned problems associated with known processes for separating hydrogen and / or nitrogen from a feed gas and concentrating ammonia are unlikely to occur. Furthermore, compared to Patent Document 7, for example, the process is characterized by significantly improved ammonia separation performance and high separation stability during operation at high temperatures and long-term operation.

[0029] Thus, when the ammonia gas concentration in a hydrogen, nitrogen, and ammonia gas mixture exceeds a certain level, the permeation selectivity of ammonia through the zeolite membrane increases significantly. The reason for this is unclear. However, increasing the ammonia gas concentration in the mixture facilitates adsorption to the zeolite due to the adsorption equilibrium between ammonia gas and the zeolite, resulting in the formation of a zeolite membrane with ammonia adsorbed within its pores. The resulting ammonia-adsorbed zeolite membrane narrows the pore size of the zeolite membrane, thereby reducing the permeation rate of hydrogen, which has a small molecular size. This effect also occurs when using zeolites with pore sizes larger than the molecular sizes of hydrogen, nitrogen, and ammonia, as the pores of the zeolite membrane narrow, significantly inhibiting hydrogen permeation. Meanwhile, ammonia adsorbed within the zeolite pores can undergo hopping due to the adsorption / desorption of ammonia within the pores due to the pressure difference between the inside and outside of the membrane. This behavior results in selective separation of ammonia. That is, the present invention is a technology that first actively adsorbs ammonia onto zeolite, controls the pore size of the zeolite membrane, and increases the ammonia separation selectivity, while allowing ammonia to selectively permeate within the pores by utilizing hopping movement due to ammonia adsorption / desorption within the pores. In contrast, Patent Document 8 differs significantly in that it proposes a technology that designs a zeolite that does not cause such adsorption, since such ammonia-adsorbed zeolite membranes cause blockages in ammonia permeation, and separates ammonia using a molecular sieve that utilizes the zeolite pore size. On the other hand, the silica membrane proposed in Patent Document 7 is less likely to adsorb ammonia, and even if ammonia is adsorbed, its thermal stability is low, so the effects of the present invention are not achieved. On the other hand, in the present invention, in which ammonia is separated primarily by the intrapore hopping mechanism accompanied by the adsorption / desorption of ammonia onto a zeolite, the temperature during ammonia separation is an important design factor because it significantly affects the long-term durability of the zeolite membrane used, the ammonia separation performance of the zeolite membrane, and the production energy balance of the entire process when combined with an ammonia production facility. From these perspectives, in the present invention, when separating the product gas in ammonia synthesis, the temperature during ammonia separation is typically the same as or lower than the ammonia synthesis temperature. The temperature during ammonia separation is the temperature inside the separator where ammonia separation is performed, i.e., the temperature of the mixed gas used for separation and the temperature of the separated ammonia gas. Furthermore, the temperature of the separation membrane can be considered to be approximately the same as the temperature inside the separator. From the perspective of ammonia production process design, performing separation at the same temperature as the synthesis temperature is preferable because it eliminates the need to heat the hydrogen and nitrogen recycled to the reactor. For this reason, the preferred temperature during ammonia separation, although depending on the reaction temperature in the ammonia synthesis reaction, is typically 500°C or lower, preferably 450°C or lower, and more preferably 400°C or lower. When ammonia is separated using the zeolite membrane of the present invention under these temperature conditions, the zeolite membrane is highly stable, enabling continuous operation over a long period of time and exhibiting high ammonia permeation selectivity. Meanwhile, the lower limit is typically a temperature above 50°C, preferably 100°C or higher, more preferably 150°C or higher, particularly preferably 200°C or higher, and among these, preferably 250°C or higher, and particularly preferably 300°C or higher. Separating ammonia under these temperature conditions improves the desorption rate of ammonia adsorbed in the zeolite pores, thereby improving the ammonia permeation rate through the zeolite membrane. Furthermore, when recycling raw gas as an ammonia production process, ammonia separation under higher temperature conditions is preferred because it reduces the energy required to heat hydrogen and nitrogen. From this perspective, the lower limit is preferably 250°C or higher, more preferably 300°C or higher. In the method of separating ammonia by intrapore hopping migration as in the present invention, the rate can be controlled by controlling the molar ratio of alkali metal atoms to Al atoms in the zeolite pores to be less than the saturation ratio, so control of this molar ratio is important, and it may be preferable to combine this method with a technique of controlling the molar ratio to 0.01 or more and 0.070 or less as in the fourth embodiment of the present invention. While there are no particular limitations on the composition of other gases in the feed gas (mixed gas), the volume ratio of hydrogen gas to nitrogen gas contained in the feed gas is typically 3 or less, more preferably 2 or less. Adjusting this volume ratio reduces the amount of hydrogen permeating during ammonia separation, improving ammonia separation selectivity. For these reasons, when the feed gas for the ammonia separation process of the present invention is obtained from an ammonia production process, it is preferable to combine it with a Ru-based ammonia production catalyst process in which the volume ratio of hydrogen gas to nitrogen gas in the feed gas is low, although this is not particularly limited. On the other hand, the lower limit is not particularly limited because the lower the ratio, the better the ammonia separation selectivity, but is typically 0.2 or more, preferably 0.3 or more, and more preferably 0.5 or more. Here, the upper and lower limits are defined within the range of significant figures. That is, an upper limit of 3 or less means 2.5 to less than 3.5, while 0.2 or more means 0.15 to less than 0.25, and 1.0 or more means 0.95 to less than 1.05.

[0030] In the present invention, the pressure of the feed gas (mixed gas) is preferably higher because the separation performance of the zeolite membrane improves and the area of ​​the zeolite membrane used can be reduced, but there is no particular limitation as long as the pressure is equal to or higher than atmospheric pressure, and the pressure may be appropriately reduced and adjusted to the desired pressure. If the pressure of the gas to be separated is lower than the pressure used for separation, it can be increased using a compressor or the like.

[0031] The pressure of the supply gas is usually atmospheric pressure or higher, preferably 0.1 MPa or higher, more preferably 0.2 MPa or higher, and the upper limit is usually 20 MPa or lower, preferably 10 MPa or lower, more preferably 5 MPa or lower, and may be 3 MPa or lower.

[0032] The pressure on the permeation side is not particularly limited as long as it is lower than the pressure of the gas on the supply side, but is usually 10 MPa or less, preferably 5 MPa or less, more preferably 1 MPa or less, and even more preferably 0.5 MPa or less, and in some cases may be reduced to a pressure below atmospheric pressure. When separating ammonia until the concentration of ammonia in the supply gas becomes low, a low pressure on the permeation side is preferred, and reducing the pressure to below atmospheric pressure makes it possible to separate ammonia until the ammonia gas concentration in the supply gas becomes even lower.

[0033] The pressure difference between the gas on the feed side and the gas on the permeation side is not particularly limited, but is usually 20 MPa or less, preferably 10 MPa or less, more preferably 5 MPa or less, and even more preferably 1 MPa or less, and is usually 0.001 MPa or more, preferably 0.01 MPa or more, and more preferably 0.02 MPa or more.

[0034] Here, the differential pressure refers to the difference between the partial pressure on the supply side and the partial pressure on the permeation side of the gas. Furthermore, pressure [Pa] refers to absolute pressure unless otherwise specified.

[0035] The flow rate of the feed gas should be such that it can compensate for the decrease in the permeating gas, and that it can mix the feed gas so that the concentration of the gas with low permeability in the immediate vicinity of the membrane matches the concentration in the entire gas. Although it depends on the tube diameter of the zeolite membrane composite and the separation performance of the membrane, the linear velocity is usually 0.001 mm / sec or more, preferably 0.01 mm / sec or more, more preferably 0.1 mm / sec or more, and among these, it is preferred The upper limit is not particularly limited, and is usually 1 m / sec or less, preferably 0.5 m / sec or less.

[0036] In the method for separating ammonia from a mixed gas of the present invention, a sweep gas may be used. The sweep gas refers to a gas supplied to efficiently recover ammonia that has permeated through the separation membrane. It is not a gas introduced into the feed gas side before separation and permeation, but a gas supplied to the permeation side of the separation membrane. In other words, the sweep gas is a gas supplied separately from the feed gas before separation and permeation, and a gas different from the feed gas is passed through the permeation side to recover the gas that has permeated the membrane. The sweep gas used in the present invention refers to, for example, gas 9 supplied from line 12 shown in FIG. 1. The pressure of the sweep gas is usually atmospheric pressure, but is not particularly limited to atmospheric pressure. It is preferably 20 MPa or less, more preferably 10 MPa or less, and even more preferably 1 MPa or less. The lower limit is preferably 0.09 MPa or more, more preferably 0.1 MPa or more. In some cases, the sweep gas may be used at reduced pressure.

[0037] The flow rate of the sweep gas is not particularly limited, but is usually 0.5 mm / sec or more, preferably 1 mm / sec or more, in terms of linear velocity. There is no upper limit, but it is usually 1 m / sec or less, preferably 0.5 m / sec or less.

[0038] The apparatus used for gas separation is not particularly limited, but a zeolite membrane composite is usually used as a membrane module (hereinafter, "zeolite membrane composite and / or separation apparatus using a zeolite membrane composite" may be simply referred to as "membrane module"). The membrane module may be, for example, an apparatus as schematically shown in FIG. 1, or may be a membrane module exemplified in "Gas Separation and Purification Technology" (Toray Research Center, Inc., 2007, p. 22). The operation of separating a mixed gas in the apparatus of FIG. 1 will be explained in the Examples section.

[0039] When performing membrane separation of ammonia from a mixed gas, membrane modules may be used in multiple stages. In this case, the gas to be separated may be supplied to the first membrane module, and the non-permeated gas that does not permeate the membrane may be further supplied to the second membrane module, or the permeated gas may be supplied to the second membrane module. The former method can further increase the concentration of less permeable components in the non-permeated side, while the latter method can further increase the concentration of more permeable components in the permeated gas. A combination of these methods can also be used. When separation is performed using membrane modules provided in multiple stages, the pressure of the feed gas may be adjusted by a pressure booster or the like as necessary when the gas is supplied to the membrane module in the subsequent stage.

[0040] Furthermore, when using multiple membrane modules, membranes with different performance characteristics can be installed in each stage. Generally, membranes with high permeability have low separation performance, while membranes with high separation performance tend to have low permeability. Therefore, when processing gas components to be separated or concentrated to a desired concentration, membranes with high permeability require a smaller membrane area, but low-permeability components also easily permeate to the permeate side, resulting in a low concentration of highly permeable components in the permeate side gas. Conversely, membranes with high separation performance tend to limit the permeation of low-permeability components to the permeate side, resulting in a high concentration of highly permeable components in the permeate side gas, but require a larger membrane area. Separation using a single type of membrane makes it difficult to control the relationship between the required membrane area and the permeation and non-permeation amounts of the target gas for concentration or separation. However, using membranes with different performance characteristics makes this easier. By selecting the optimal membrane area and the permeation and non-permeation amounts of the target gas for concentration or separation, based on the membrane cost and the price of the gas to be separated and recovered, membranes can be installed to maximize overall benefits.

[0041] For example, if ammonia cannot be sufficiently separated in one membrane separation, the non-permeate gas can be separated using several more membranes. Also, if the ammonia / hydrogen separation of the membrane is not sufficient in one membrane separation and a large amount of hydrogen is contained in the permeate side along with ammonia, the permeate gas can be separated using several more membranes. Ammonia and hydrogen can also be separated using a membrane with high separation performance.

[0042] The zeolite membrane used in the present invention has excellent chemical resistance, oxidation resistance, heat stability, and pressure resistance, and also exhibits high ammonia permeability and separation performance, and has excellent durability.

[0043] The term "high permeability" used here refers to a sufficient throughput, for example, the permeance [mol / (m 2 ·s·Pa)], for example, when ammonia is passed through at a temperature of 200°C and a differential pressure of 0.3 MPa, it is usually 1×10 -9 or more, preferably 5 x 10 -9 or more, more preferably 1×10 -8 More preferably, 2 × 10 -8 More than 5 × 10 -8 More preferably, 1×10 -7 or more, most preferably 2 x 10 -7 The upper limit is not particularly limited, and is usually 3 × 10 -4 The following is the result.

[0044] The permeance [mol / (m 2 ·s·Pa)] is typically 5×10 -8 Less than or equal to 3 x 10 -8 Less than or equal to 1×10 -8 Below, particularly preferably 5 × 10 -9 Below 1×10, most preferably -9 Ideally, the permeance is 0, but in practice it is 1×10 -10 ~1×10 -14 It may be on the order of about this.

[0045] Here, permeance (also called "permeability") is the amount of permeating substance divided by the product of the membrane area, time, and the partial pressure difference between the supply side and permeation side of the permeating substance, and its unit is [mol / (m 2s Pa)] and by the method described in the Examples section This is the value calculated.

[0046] The selectivity of a zeolite membrane is expressed by an ideal separation factor. The ideal separation factor and separation factor are indicators of selectivity generally used in membrane separation. The ideal separation factor is calculated by the method described in the Examples section, and the separation factor is calculated as follows:

[0047] The separation factor α is calculated using the following formula. α=(Q'1 / Q'2) / (P'1 / P'2) [In the above formula, Q'1 and Q'2 represent the permeation amounts [mol / (m 2 s Pa), and P'1 and P'2 represent the partial pressures [Pa] of the highly permeable gas and the less permeable gas in the supply gas, respectively. The separation factor α can also be determined as follows. α=(C'1 / C'2) / (C1 / C2) (In the above formula, C'1 and C'2 represent the concentrations [vol %] of the highly permeable gas and the less permeable gas in the permeating gas, respectively, and C1 and C2 represent the concentrations [vol %] of the highly permeable gas and the less permeable gas in the supply gas, respectively.)

[0048] For example, when ammonia and nitrogen are permeated at a temperature of 200°C and a differential pressure of 0.3 MPa, the ideal separation factor is usually 15 or more, preferably 20 or more, more preferably 25 or more, and most preferably 30 or more. When ammonia and hydrogen are permeated at a temperature of 200°C and a differential pressure of 0.3 MPa, the ideal separation factor is usually 2 or more, preferably 3 or more, more preferably 5 or more, even more preferably 7 or more, particularly preferably 8 or more, particularly preferably 10 or more, and most preferably 15 or more. The upper limit of the ideal separation factor is when only ammonia permeates, in which case the upper limit is infinite, but in practice the separation factor may be about 100,000 or less.

[0049] The separation factor of the zeolite membrane used in the present invention, for example, when a mixed gas of ammonia and nitrogen in a volume ratio of 1:1 is permeated at a temperature of 50°C and a differential pressure of 0.1 MPa, is usually 2 or more, preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. The upper limit of the separation factor is when only ammonia permeates, in which case it is infinite, but in practice the separation factor may be about 100,000 or less.

[0050] As described above, the zeolite membrane used in the present invention has excellent chemical resistance, oxidation resistance, heat stability, and pressure resistance, and exhibits high permeability and separation performance and is highly durable. The ammonia separation method of the present invention using such a zeolite membrane can be applied to the separation of ammonia from the product of ammonia synthesis. Furthermore, the ammonia separation method of the present invention can also be used as a membrane reactor in which a zeolite membrane is provided in an ammonia synthesis reactor, and ammonia is selectively permeated and separated in the reactor, thereby shifting the equilibrium between hydrogen gas and nitrogen gas and ammonia gas in the reaction system, thereby synthesizing ammonia efficiently at a high conversion rate.

[0051] (Zeolite) In the present invention, the zeolite constituting the zeolite membrane is an aluminosilicate. The aluminosilicate is mainly composed of oxides of Si and Al, and may contain other elements as long as the effects of the present invention are not impaired. The cationic species contained in the zeolite of the present invention are preferably cationic species that are easily coordinated to the ion exchange sites of the zeolite, for example, cationic species selected from the group consisting of elements of Groups 1, 2, 8, 9, 10, 11, and 12 of the periodic table, NH4 + and two or more of these cationic species, more preferably cationic species selected from the group of elements of Groups 1 and 2 of the periodic table, NH4 + and two or more cationic species thereof.

[0052] The zeolite used in the present invention is an aluminosilicate. The SiO2 / Al2O3 molar ratio of the aluminosilicate is not particularly limited, but is usually 6 or more, preferably 7 or more, and more preferably 8 or more. It is usually 500 or less, preferably 100 or less, more preferably 80 or less, even more preferably 50 or less, particularly preferably 45 or less, even more preferably 30 or less, and most preferably 25 or less. Using a zeolite with an SiO2 / Al2O3 molar ratio in this specific range is preferable because it improves the density of the zeolite membrane and its durability, such as chemical reactivity resistance and heat resistance. Furthermore, from the perspective of the separation performance of ammonia permeation from a mixed gas containing multiple components including ammonia, hydrogen, and nitrogen, it is preferable to use a zeolite containing a larger amount of Al, because the acid sites of the Al element serve as ammonia adsorption sites, as mentioned above. Using a zeolite with the above SiO2 / Al2O3 molar ratio allows for high ammonia permeation and high selectivity separation. The SiO2 / Al2O3 molar ratio of the zeolite is adjusted by the reaction conditions of the hydrothermal synthesis, which will be described later. It is possible.

[0053] In this specification, the SiO2 / Al2O3 molar ratio is determined by scanning electron microscope-energy This is a value determined by electron-dispersive X-ray spectroscopy (SEM-EDX). In this case, measurements are usually performed at an X-ray acceleration voltage of 10 kV to obtain information on films only a few microns thick.

[0054] The structure of the zeolite used in the present invention is that of the International Zeolite Association ( For example, ABW, ACO, AEI, AEN, AFI, AFT, AFX, ANA, ATN, ATT, ATV, AWO, AWW, BIK, CHA, DDR, DFT, EAB, EPI, ERI, ESV, GIS, GOO, ITE, JBW, KFI, LEV, LTA, MER, MON, MTF, OWE, PAU, PHI. , RHO, RTE, RWR, SAS, SAT, SAV, SIV, TSC, UFI, VNI, YUG, AEL, AFO, AHT, DAC, FER, HEU, IMF, ITH, MEL, MFS, MWW, OBW, RRO, SFG, STI, SZR, TER, TON, TUN, WEI, MFI, MON, PAU, PHI, MOR, FAU, etc.

[0055] Among them, the framework density is 18.0T / nm 3 Zeolites having the following structure are preferred: More preferably, AEI, AFX, CHA, DDR, ERI, LEV, RHO, MOR, MFI, or FAU, even more preferably AEI, CHA, DDR, RHO, MOR, MFI, or FAU, particularly preferably CHA, RHO, or MFI, and most preferably RHO or MFI. By using a zeolite with a low framework density, when permeating components other than ammonia are present in a mixed gas containing ammonia, the resistance to permeation of these permeating components can be reduced, making it easier to increase the amount of ammonia permeated. In the fifth embodiment of the present invention (zeolite membrane composite E), the framework density is 18.0 T / nm 3 Zeolites such as AFX, DDR, ERI, LEV, RHO, MOR, MFI, and FAU are preferred, DDR, RHO, MOR, MFI, and FAU are more preferred, and RHO and MFI are most preferred.

[0056] Here, the framework density (unit: T / nm 3 ) is the unit volume (1 nm) of zeolite 3It means the number of T atoms (atoms other than oxygen that make up the zeolite framework) present per 1000 sq m (1000 sq m), and this value is determined by the structure of the zeolite. The relationship between framework density and zeolite structure is shown in ATLAS OF ZEOLITE FRAMEWORK TYPES Sixth Revised Edition 2007 ELSEVIER.

[0057] The membrane separation of ammonia, hydrogen, and nitrogen according to the present invention utilizes the adsorption of ammonia onto zeolite, and is characterized by the separation of ammonia based on the hopping mechanism of ammonia within the zeolite pores. Although not particularly limited, zeolites having pore sizes close to the molecular diameter of ammonia may be preferable because they improve ammonia separation selectivity. From this perspective, zeolites with 8-membered oxygen ring pores are preferred. On the other hand, pores larger than the 8-membered oxygen ring are preferred because they increase ammonia permeability, but may have reduced separation performance from hydrogen and / or nitrogen. However, even when using zeolites with pores larger than the 8-membered oxygen ring, if a zeolite with a reduced SiO2 / Al2O3 molar ratio is used, the ammonia adsorbed on the Al site may be easily separated. The pore size of the zeolite membrane is controlled by ammonia, allowing ammonia to be separated with high selectivity and high permeability.

[0058] Therefore, the effective pore size of the zeolite used in membrane separation is an important design factor, as it significantly affects the pore size of the zeolite membrane when ammonia is adsorbed. The effective pore size of the zeolite can also be controlled by the type of metal introduced into the zeolite, ion exchange, acid treatment, silylation treatment, etc. It is also possible to improve separation performance by controlling the effective pore size using other methods.

[0059] For example, the pore size of a zeolite is slightly affected by the atomic size of the metal species introduced into the zeolite framework. When a metal with an atomic size smaller than that of silicon, such as boron (B), is introduced, the pore size becomes smaller, while when a metal with an atomic size larger than that of silicon, such as tin (Sn), is introduced, the pore size becomes larger. In addition, the pore size may be affected by desorbing the metal introduced into the zeolite framework through acid treatment.

[0060] When ions in zeolite are exchanged with monovalent ions with a large ionic radius, the effective pore size becomes smaller. On the other hand, when ions are exchanged with monovalent ions with a small ionic radius, the effective pore size becomes close to the pore size inherent in the zeolite structure.

[0061] The effective pore size of zeolite can also be reduced by silylation treatment. For example, by silylating the terminal silanols on the outer surface of a zeolite membrane and then laminating a silylated layer, the effective pore size of the pores facing the outer surface of the zeolite can be reduced.

[0062] The separation function of the zeolite membrane composite used in the present invention is not particularly limited, but is manifested by controlling the surface properties of the zeolite to control the affinity and adsorption of gas molecules to the zeolite membrane. That is, by controlling the polarity of the zeolite, the adsorption of ammonia to the zeolite can be controlled, thereby facilitating permeation.

[0063] For example, as in the second embodiment of the present invention, the polarity of the zeolite can be controlled by making nitrogen atoms present, thereby controlling the affinity of ammonia to the zeolite and making it easier for ammonia to pass through.

[0064] In addition, the polarity of zeolite can be increased by substituting Al atoms for Si atoms in the zeolite framework, which allows highly polar gas molecules such as ammonia to be actively adsorbed and permeated through the zeolite pores. Furthermore, the polarity of the resulting zeolite can be controlled by adding other atom sources besides Al atoms, such as Ga, Fe, B, Ti, Zr, Sn, and Zn, to the aqueous reaction mixture for hydrothermal synthesis.

[0065] In addition, ion exchange can be used to control not only the pore size of the zeolite but also its molecular adsorption performance, thereby controlling the permeation rate.

[0066] (Zeolite membrane) The zeolite membrane in the present invention refers to a membranous material made of zeolite, preferably formed by crystallizing zeolite on the surface of a porous support. The membrane may contain, as necessary, inorganic binders such as silica and alumina, organic substances such as polymers, or silylating agents for modifying the zeolite surface, in addition to zeolite. The preferred zeolite contained in the zeolite membrane used in the present invention is as described above, but the zeolite contained in the zeolite membrane may be one type or multiple types. Furthermore, the zeolite membrane may contain zeolites that tend to form in a mixed phase, such as ANA, GIS, and MER, or amorphous components other than crystals.

[0067] Another aspect of the present invention (zeolite membrane B) is a zeolite membrane containing zeolite, characterized in that the molar ratio of nitrogen element to Al element determined by X-ray photoelectron spectroscopy is 0.01 or more and 4 or less. Zeolite membrane B is particularly preferably used in the ammonia separation method of the first embodiment. Zeolite membrane B is preferably a zeolite membrane having a surface in which the molar ratio of nitrogen atoms to Al atoms, as determined by X-ray photoelectron spectroscopy (XPS), falls within a specific range. Here, the "surface of the zeolite membrane" in this specification refers to the surface of the zeolite membrane on the side where a mixed gas consisting of multiple components including ammonia and hydrogen and / or nitrogen is supplied for ammonia separation. When the zeolite membrane composite is used in the form of a membrane formed on a porous support, it refers to the side that is not in contact with the porous support. In this specification, the molar ratio of nitrogen atoms to Al atoms contained in the zeolite membrane is a value determined by X-ray photoelectron spectroscopy (XPS) under the following measurement conditions:

[0068] (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method

[0069] In the second embodiment of the present invention, the nitrogen atom content of the zeolite membrane surface, as determined by the XPS measurement, relative to the Al atoms on the zeolite membrane surface, is typically 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, particularly preferably 0.30 or more, and particularly preferably 0.50 or more. The upper limit is not particularly limited because it depends on the structure of the nitrogen-containing cation species in the zeolite membrane and the amount of nitrate ions remaining after nitration treatment of the zeolite membrane, if necessary. However, it is typically 4 or less, preferably 3 or less, and more preferably 1 or less. The use of a zeolite having a surface composition with such a specific nitrogen atom / Al atomic ratio can improve the denseness and durability of the zeolite membrane, such as chemical reactivity resistance and heat resistance, and can also enable high permeability and high selectivity separation of ammonia from a mixed gas consisting of ammonia and multiple components including hydrogen and / or nitrogen. The upper and lower limits are defined within the range of significant figures. That is, the upper limit of 4 or less means less than 4.5, while 0.01 or more means 0.005 or more.

[0070] In the second embodiment of the present invention, the nitrogen atoms contained in the zeolite membrane are substituted by ammonium ions (NH4 + nitrogen atoms derived from cationic species protonated from organic amines having 1 to 20 carbon atoms, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetraamine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N,N-diisopropylethylamine, N,N,N-trimethyl-1-adamantanamine, pyridine, and piperidine; nitrogen atoms derived from an organic template when a nitrogen-containing organic template (structure-directing agent) is used in producing a zeolite membrane; and nitrogen atoms derived from nitrate ions remaining after the nitrate treatment of a zeolite membrane, which is performed as needed, as described below.

[0071] Although the details of this embodiment are not yet clear and are not particularly limited, as described below, the effective pore size of the zeolite used for membrane separation is controlled by utilizing the adsorption of ammonia to the zeolite, and ammonia is separated based on the hopping mechanism of ammonia within the zeolite pores. In this embodiment, in which ammonia is separated primarily by utilizing the intrapore hopping mechanism involving the adsorption / desorption of ammonia to the zeolite, an important design factor is how to increase the adsorption affinity of ammonia in the ammonia-containing feed mixed gas with the zeolite membrane surface relative to other gases, such as hydrogen and nitrogen, contained in the mixed gas. From this perspective, the presence of nitrogen atoms in the above-described form on the zeolite membrane surface tends to improve ammonia separation performance because the adsorption affinity of ammonia to the zeolite membrane is increased due to interactions such as hydrogen bonding with ammonia in the feed gas.

[0072] Another aspect of the present invention (zeolite membrane C) is a zeolite membrane containing zeolite, characterized in that the molar ratio of Si element to Al element determined by X-ray photoelectron spectroscopy is 2.0 or more and 10 or less. Zeolite membrane C is preferably used in the ammonia separation method of the first embodiment. The zeolite membrane C used in the present invention is characterized by having a surface in which the molar ratio of Si atoms to Al atoms, as determined by X-ray photoelectron spectroscopy (XPS), falls within a specific range. In this specification, the molar ratio of Si atoms to Al atoms contained in the zeolite membrane is a value determined by X-ray photoelectron spectroscopy (XPS) under the following measurement conditions:

[0073] (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method In this embodiment, the molar ratio of Si atoms contained in the zeolite membrane surface, as determined by the XPS measurement, to Al atoms on the zeolite membrane surface is 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more, with the upper limit usually being 10 or less, preferably 8.0 or less, more preferably 7.0 or less, and particularly preferably 6.7 or less. In the present invention, the molar ratio of Si atoms to Al atoms in the zeolite membrane can be controlled by, as described below, controlling the SiO / AlO ratio of the zeolite in the zeolite membrane or treating the zeolite membrane with an aluminum salt. As apparent from this example, when ammonia is separated from a mixed gas containing ammonia and multiple components including hydrogen and / or nitrogen, the use of a zeolite membrane with such a specific Si / Al molar ratio improves the denseness and durability of the zeolite membrane, such as chemical reactivity resistance and heat resistance, and also improves separation thermal stability at high temperatures.

[0074] In this embodiment, the Si atom content on the zeolite membrane surface is controlled, and if necessary, the nitrogen atom content on the zeolite membrane surface, as determined by XPS measurement, is controlled to a specific range. This tends to significantly improve the separation selectivity when separating ammonia from a mixed gas composed of multiple components contained on the zeolite membrane surface. Therefore, it is preferable to allow nitrogen atoms to coexist on the zeolite membrane surface and appropriately control their contents. When nitrogen atoms are present on the zeolite membrane surface as necessary, the nitrogen atom content relative to the Al atoms on the zeolite membrane surface is typically 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, particularly preferably 0.30 or more, and particularly preferably 0.50 or more. The upper limit is not particularly limited because it depends on the structure of the nitrogen-containing cation species in the zeolite contained in the zeolite membrane and the amount of nitrate ions remaining when the zeolite membrane is subjected to nitrate treatment as necessary. However, it is typically 4 or less, preferably 3 or less, and more preferably 1 or less. The use of a zeolite having a surface composition with such a specific nitrogen atom / Al atomic ratio is preferable because it can improve the denseness of the zeolite membrane and its durability, such as chemical reactivity resistance and heat resistance, and also enables highly selective separation of ammonia from a mixed gas consisting of ammonia and multiple components including hydrogen and / or nitrogen. The upper and lower limits described above are valid within the range of significant figures. That is, an upper limit of 4 or less means less than 4.5, while a value of 0.01 or more means 0.005 or more.

[0075] In this embodiment, when nitrogen atoms are contained in the zeolite membrane, the nitrogen atoms are ammonium ions (NH4 +), nitrogen atoms derived from cationic species obtained by protonating organic amines having 1 to 20 carbon atoms, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetraamine, aniline, methylaniline, benzylamine, as well as methylbenzylamine, hexamethylenediamine, N,N-diisopropylethylamine, N,N,N-trimethyl-1-adamantanamine, pyridine, and piperidine; nitrogen atoms derived from an organic template when a nitrogen-containing organic template (structure-directing agent) is used in producing a zeolite membrane; and nitrogen atoms derived from nitrate ions remaining after the nitrate treatment of a zeolite membrane, which is performed as needed, as described below.

[0076] In this embodiment, furthermore, when the content of alkali metal atoms contained in the zeolite membrane surface as determined by XPS measurement is controlled to a specific range, the ammonia permeability tends to improve when ammonia is separated from a mixed gas consisting of ammonia and multiple components including hydrogen and / or nitrogen. Therefore, controlling the content as needed is one of the preferred embodiments. In this way, alkali metal atoms when present on the zeolite membrane surface as needed include Li, Na, K, Rb, Cs, and the like. Examples include two or more metal atoms from these metals. Among these, Li, Na, and Cs are preferred, with Na being more preferred because it has excellent ammonia separation performance and is a commonly used alkali metal. These alkali metal atoms exist in the form of cations as ion pairs at Al sites in the zeolite constituting the zeolite membrane, and are usually introduced into the zeolite by ion exchange treatment of the synthesized zeolite membrane, as described below. When alkali metal atoms are optionally present on the zeolite membrane surface, the content of the alkali metal atoms relative to the Al atoms on the zeolite membrane surface is, in molar ratio, 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, even more preferably 0.04 or more, and particularly preferably 0.05 or more. The upper limit is usually 0.10 molar equivalents or less, preferably 0.070 molar equivalents or less, more preferably 0.065 molar equivalents or less, even more preferably 0.060 molar equivalents or less, and particularly preferably 0.55 molar equivalents or less. Controlling the content of alkali metal atoms within the above range tends to improve ammonia permeability while maintaining high ammonia separation selectivity, which is preferable. The molar ratio of alkali metal atoms to Al atoms in the zeolite membrane can be controlled by adjusting the amount of ions exchanged during ion exchange treatment of the zeolite, as described below. This embodiment, while not yet fully understood and not particularly limited, is characterized in that the effective pore size of the zeolite used for membrane separation is controlled by utilizing the adsorption of ammonia onto the zeolite, and ammonia is separated based on the hopping mechanism of ammonia within the zeolite pores, as described below. In this invention, which primarily utilizes the intrapore hopping mechanism involving the adsorption / desorption of ammonia onto the zeolite to separate ammonia, an important design factor is how to increase the adsorption affinity of ammonia in the ammonia-containing feed mixed gas with the zeolite membrane surface compared to other gases, such as hydrogen and nitrogen, contained in the mixed gas. From this perspective, the presence of more Al atoms on the zeolite membrane surface changes the polarity of the zeolite membrane surface, increasing the adsorption affinity with ammonia in the feed gas, thereby improving ammonia separation performance. Furthermore, in this embodiment, the content of Al atoms on the zeolite membrane surface is determined by the SiO2 / Al2O3 ratio of the zeolite constituting the zeolite membrane and the zeolite membrane formation temperature. This is controlled by the subsequent aluminum salt treatment, etc., but the latter aluminum salt treatment in particular has the effect of sealing fine defects present on the zeolite membrane surface, which can improve the density of the zeolite membrane as well as its durability, such as chemical reactivity resistance and heat resistance, and also greatly contributes to improving the thermal separation stability of the zeolite membrane at high temperatures, which is one of the objects of the present invention.

[0077] Another aspect of the present invention (zeolite membrane D) is a zeolite membrane containing zeolite, in which the molar ratio of alkali metal element to Al element determined by X-ray photoelectron spectroscopy is 0.01 or more and 0.070 or less. Zeolite membrane D is particularly preferably used in the ammonia separation method of the first embodiment. The zeolite membrane D used in the fourth embodiment of the present invention is preferably a zeolite membrane having a surface in which the molar ratio of alkali metal atoms to Al atoms, as determined by X-ray photoelectron spectroscopy (XPS), falls within a specific range. In this specification, the molar ratio of alkali metal atoms to Al atoms contained in the zeolite membrane is a value determined by X-ray photoelectron spectroscopy (XPS) under the following measurement conditions:

[0078] (Measurement conditions) X-ray source during measurement: Monochromated Al-Kα ray, output 16kV-34W Background determination in quantitative calculations: Shirley's method

[0079] In this embodiment, examples of alkali metal atoms contained in the zeolite membrane surface determined by the XPS measurement include Li, Na, K, Rb, Cs, and two or more of these metal atoms. Among these, Li, Na, and Cs are preferred, and Na is more preferred because it has excellent ammonia separation performance and is a commonly used alkali metal. These alkali metal atoms form ion pairs with Al sites in the zeolite constituting the zeolite membrane. These exist in the form of cations and are usually introduced into the zeolite by ion exchange treatment of the synthesized zeolite membrane, as described below.

[0080] In this embodiment, it is important to control the content of alkali metal atoms contained in the zeolite membrane surface as determined by the XPS measurement described above. The content, in terms of molar ratio relative to Al atoms on the zeolite membrane surface, is 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, even more preferably 0.04 or more, and particularly preferably 0.05 or more. The upper limit is usually 0.10 molar equivalents or less, preferably 0.070 molar equivalents or less, more preferably 0.065 molar equivalents or less, even more preferably 0.060 molar equivalents or less, and particularly preferably 0.55 molar equivalents or less. As is clear from the present examples and reference examples, by controlling the alkali metal element content within the above range, it is possible to improve ammonia permeability while maintaining high ammonia separation selectivity.

[0081] In this embodiment, the molar ratio of alkali metal atoms to Al atoms in the zeolite membrane can be controlled by adjusting the amount of ions exchanged during the ion exchange treatment of the zeolite, as described below. By using a zeolite membrane with such a specific alkali metal atom / Al atomic ratio, when separating ammonia from a mixed gas containing multiple components including ammonia and hydrogen and / or nitrogen, it is possible to improve the ammonia permeability while exhibiting high permeation selectivity compared to a zeolite membrane that does not contain the alkali metal atoms. In this embodiment, controlling the content of alkali metal atoms on the zeolite membrane surface and, if necessary, controlling the content of nitrogen atoms on the zeolite membrane surface, as determined by XPS measurement, to a specific range tends to significantly improve the separation selectivity when separating ammonia from a mixed gas consisting of ammonia and multiple components containing hydrogen and / or nitrogen. Therefore, it is preferable to allow alkali metal atoms and nitrogen atoms to coexist on the zeolite membrane surface and appropriately control their contents. When nitrogen atoms are present on the zeolite membrane surface, the content of the nitrogen atoms relative to the Al atoms on the zeolite membrane surface is typically 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, particularly preferably 0.30 or more, and particularly preferably 0.50 or more. The upper limit is not particularly limited because it depends on the structure of the nitrogen-containing cation species in the zeolite contained in the zeolite membrane and the amount of nitrate ions remaining when the zeolite membrane is subjected to nitrate treatment, if necessary. However, it is typically 4 or less, preferably 3 or less, and more preferably 1 or less. The use of a zeolite having a surface composition with such a specific nitrogen atom / Al atomic ratio is preferable because it can improve the denseness of the zeolite membrane and its durability, such as chemical reactivity resistance and heat resistance, and also enables highly selective separation of ammonia from a mixed gas consisting of ammonia and multiple components including hydrogen and / or nitrogen. The upper and lower limits described above are valid within the range of significant figures. That is, an upper limit of 4 or less means less than 4.5, while a value of 0.01 or more means 0.005 or more.

[0082] In the present invention, when nitrogen atoms are contained in the zeolite membrane, the nitrogen atoms are ammonium ions (NH4 + ), nitrogen atoms derived from cationic species obtained by protonating organic amines having 1 to 20 carbon atoms, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetraamine, aniline, methylaniline, benzylamine, as well as methylbenzylamine, hexamethylenediamine, N,N-diisopropylethylamine, N,N,N-trimethyl-1-adamantanamine, pyridine, and piperidine; nitrogen atoms derived from an organic template when a nitrogen-containing organic template (structure-directing agent) is used in producing a zeolite membrane; and nitrogen atoms derived from nitrate ions remaining after the nitrate treatment of a zeolite membrane, which is performed as needed, as described below.

[0083] Although the details of this embodiment are not yet clear and are not particularly limited, as described below, the present invention is characterized by controlling the effective pore size of the zeolite used in membrane separation by utilizing the adsorption of ammonia to the zeolite, and separating ammonia based on the hopping mechanism of ammonia within the zeolite pores. In this embodiment, ammonia is separated primarily by utilizing the intrapore hopping mechanism, which involves the adsorption / desorption of ammonia to the zeolite. In this embodiment, the ammonia separation selectivity from a mixed gas containing ammonia and multiple components, including hydrogen and / or nitrogen, is improved by the blocking effect of ammonia adsorption to the Al sites within the zeolite pores. However, the high adsorption of ammonia to the Al sites tends to impair permeability (permeability). In contrast, by incorporating a specific amount of alkali metal atoms in the form of cations as ion pairs at the Al sites in the zeolite constituting the zeolite membrane, the amount of ammonia adsorbed to the Al sites can be controlled, while the size of the alkali metal cations can maintain ammonia separation selectivity. These mechanisms enable increased permeability while maintaining ammonia separation selectivity. That is, it is important to control the content of alkali metal atoms relative to Al atoms in the zeolite to a molar ratio of 0.01 or more and 0.070 or less. If the molar ratio is less than 0.01, the ammonia permeability will decrease due to the adsorption of ammonia to the Al sites, while if the molar ratio exceeds 0.20, the blocking effect due to the adsorption of ammonia to the Al sites will be weakened, and the ammonia separation selectivity will decrease.

[0084] Another aspect of the present invention (zeolite membrane composite E) is a zeolite membrane composite for ammonia separation, comprising a porous support and a zeolite membrane containing zeolite on the surface thereof, characterized in that the rate of change in the thermal expansion coefficient of the zeolite at 300°C and at 400°C relative to the thermal expansion coefficient at 30°C falls within a specific range. Zeolite membrane composite E is preferably used in the ammonia separation method of the first embodiment. Specifically, the rate of change in the thermal expansion coefficient of zeolite at 300°C relative to that at 30°C is within ±0.25%, and the rate of change in the thermal expansion coefficient at 400°C relative to that at 30°C is within ±0.35%. The thermal expansion coefficient that defines the zeolite of this embodiment is a numerical value calculated under the following conditions. In this specification, when the numerical value of the thermal expansion coefficient is a positive number, it indicates that the zeolite has expanded, and when it is a negative number, it indicates that the zeolite has contracted.

[0085] (Method for measuring the rate of change in thermal expansion coefficient) In the present invention, the rate of change in the thermal expansion coefficient of a zeolite at a predetermined temperature relative to the thermal expansion coefficient at 30°C can be calculated by the following formula (1) using the crystallite constant measured at 30°C and the predetermined temperature by a temperature-programmed XRD measurement method under the following conditions.

[0086] (Temperature-raised XRD measurement equipment specifications)

[0087] [Table 1]

[0088] (Measurement conditions)

[0089] [Table 2] Measurement atmosphere: air Temperature rise condition: 20℃ / min Measurement method: XRD measurement is carried out after holding at the measurement temperature for 5 minutes. The measurement data is subjected to fixed slit correction using a variable slit.

[0090] Rate of change of thermal expansion coefficient = (crystal lattice constant measured at a given temperature) ÷ (crystal lattice constant measured at 30°C) - 1 (1)

[0091] The rate of change in the thermal expansion coefficient of the zeolite of the present invention at 300°C relative to the thermal expansion coefficient at 30°C is, in absolute value, 0.25% or less, preferably 0.20% or less, more preferably 0.15% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less. The rate of change in the elongation is within ±0.25%, preferably within ±0.20%, more preferably within ±0.15%, particularly preferably within ±0.10%, and most preferably within ±0.05%. On the other hand, the rate of change in the thermal expansion coefficient of zeolite at 400°C relative to the thermal expansion coefficient at 30°C is, in absolute value, 0.35% or less, preferably 0.30% or less, more preferably 0.25% or less, particularly preferably 0.20% or less, particularly preferably 0.15% or less, and most preferably 0.10% or less. That is, the rate of change in the thermal expansion coefficient of zeolite at 400°C relative to the thermal expansion coefficient at 30°C is within ±0.35%, preferably within ±0.30%, more preferably within ±0.25%, particularly preferably within ±0.20%, particularly preferably within ±0.15%, and most preferably within ±0.10%. A zeolite composite membrane formed on a porous support using such a zeolite exhibiting a low rate of change in thermal expansion coefficient is less likely to develop cracks at the zeolite grain boundaries due to thermal expansion (contraction) of the zeolite when the composite is heated to temperatures above 200°C, particularly above 250°C, and even above 300°C, during permeation of ammonia from a gas mixture containing ammonia and multiple components including hydrogen and / or nitrogen. Therefore, the composite membrane can efficiently separate ammonia with high permeability even under high-temperature conditions. Even if a zeolite composite membrane using a zeolite exhibiting such a thermal expansion coefficient exhibits nonlinear thermal expansion / contraction behavior with respect to temperature, as described particularly in the RHO-type zeolite of this example, it still exhibits stable, high separation performance as a membrane under high-temperature conditions. Here, nonlinear thermal expansion / contraction behavior with respect to temperature refers to behavior that does not thermally expand or contract monotonically with temperature, i.e., exhibiting thermal expansion or contraction behavior in a certain temperature range but exhibiting the opposite behavior in other temperature ranges, i.e., thermal contraction in the former case and thermal expansion in the latter case.

[0092] Although the reason for this is not yet clear and is not particularly limited, it is thought that even if the zeolite thermally contracts or expands during the temperature rise process, the zeolite moves favorably on the support, does not generate cracks, and forms a dense zeolite membrane composite that exhibits high separation performance suitable for high temperature conditions. Therefore, when stably separating ammonia under high temperature conditions, a zeolite that exhibits nonlinear thermal expansion / contraction behavior during the temperature rise process may be used. There is no particular limitation on the zeolite used in the present invention, but examples thereof include RHO (DR Corbin et al. J. Am. Chem. Soc., 112, 4821-4830), MFI, AFI, DDR (Park S. H. et al. Stud. Surf. Sci. Catal. 1997, 105, 198 9-1994) are known.

[0093] Furthermore, the ratio of the rate of change in thermal expansion coefficient at 300°C to the rate of change in thermal expansion coefficient at 30°C of the zeolite of this embodiment at 400°C to the rate of change in thermal expansion coefficient at 30°C is typically 120% or less, preferably 115% or less, more preferably 110% or less, particularly preferably 105% or less, and most preferably 103% or less, in absolute value. A zeolite composite membrane formed on a porous support using a zeolite exhibiting such a specific ratio of rate of change in thermal expansion coefficient between specific temperatures can suppress the occurrence of grain boundary cracks due to local thermal expansion (contraction) of the zeolite, even when non-uniform heat generation occurs in a reactor at the beginning of the ammonia production reaction, for example, and therefore can stably and efficiently separate ammonia to the permeation side at high permeability.

[0094] The zeolite composite membrane of this embodiment is preferably prepared by a process of attaching a zeolite having a thermal expansion coefficient change rate within a specific range to a porous support as seed crystals during membrane synthesis, which often enables stable and highly selective ammonia separation even under high-temperature conditions. The absolute value of the change in thermal expansion coefficient of the zeolite used as seed crystals in the preparation of such a zeolite composite membrane is 0.25% or less, preferably 0.20% or less, more preferably 0.15% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less, relative to the thermal expansion coefficient at 30°C. On the other hand, the absolute value of the change in thermal expansion coefficient at 400°C relative to the thermal expansion coefficient at 30°C is usually 0.30% or less, preferably 0.25% or less, more preferably 0.20% or less, particularly preferably 0.15% or less, and most preferably 0.10% or less.

[0095] The rate of change in the thermal expansion coefficient of a zeolite at a specific temperature, which is a feature of this embodiment, can be controlled by appropriately selecting the cation species of the zeolite used, as described below. For example, the relationship between the cation species and the thermal expansion coefficient of RHO zeolite is known to vary depending on the cation species contained in the zeolite, as described in Chemical Communications, 2000, pp. 2221-2222. Therefore, in order to obtain a zeolite membrane composite that can stably separate ammonia with high selectivity even under high-temperature conditions as in this embodiment, it is particularly important to select a specific cation species from among the RHO zeolites. Meanwhile, with regard to the thermal expansion coefficient of the MFI zeolite described in the examples of this embodiment, a zeolite membrane composite exhibiting the characteristics of this embodiment can be produced by appropriately selecting the cation species in the zeolite, as in the case of the RHO zeolite described above. The cationic species contained in the zeolite of this embodiment are preferably cationic species that are easily coordinated to the ion exchange sites of the zeolite, and examples thereof include cationic species selected from the group consisting of elements of Groups 1, 2, 8, 9, 10, 11, and 12 of the periodic table, NH4 +and two or more of these cationic species, more preferably cationic species selected from the group of elements of Groups 1 and 2 of the periodic table, NH4 + and two or more cationic species thereof.

[0096] The zeolite used in this embodiment is an aluminosilicate. The SiO2 / Al2O3 molar ratio of the aluminosilicate is not particularly limited, but is usually 6 or more, preferably 7 or more, and more preferably 8 or more. The upper limit is usually such that Al is present in an amount comparable to an impurity, and the SiO2 / Al2O3 molar ratio is usually 500 or less, preferably 100 or less, more preferably 90 or less, even more preferably 80 or less, especially preferably 70 or less, even more preferably 50 or less, and most preferably 30 or less. The use of a zeolite having an SiO2 / Al2O3 molar ratio in this specific range can improve the denseness of the zeolite membrane and its durability, such as chemical reactivity resistance and heat resistance. Furthermore, from the viewpoint of the separation performance of ammonia permeation from a gas mixture containing multiple components including ammonia and hydrogen and / or nitrogen, it is preferable to use a zeolite containing a specific amount of Al, because the acid sites of the Al element serve as ammonia adsorption sites, as described above. The use of a zeolite having the above SiO2 / Al2O3 molar ratio allows for high-permeability and highly selective separation of ammonia. The SiO2 / Al2O3 molar ratio of the zeolite can be adjusted by the reaction conditions of the hydrothermal synthesis, which will be described later.

[0097] The thickness of the zeolite membrane used in the present invention is not particularly limited, but is usually 0.1 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, even more preferably 0.7 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. It is also usually 100 μm or less, preferably 60 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, even more preferably 10 μm or less, and particularly preferably 5 μm or less. When the thickness of the zeolite membrane is equal to or greater than the above lower limit, defects tend to be less likely to occur and separation performance tends to be improved. When the thickness of the zeolite membrane is equal to or less than the above upper limit, permeation performance tends to be improved. Furthermore, in the high-temperature region, cracks are less likely to occur in the zeolite membrane due to temperature rise, which tends to suppress a decrease in permeation selectivity at high temperatures.

[0098] The average primary particle size of the zeolite forming the zeolite membrane is not particularly limited, but is usually 30 The average primary particle size of the zeolite is 100 nm or more, preferably 50 nm or more, and more preferably 100 nm or more, with the upper limit being equal to or less than the thickness of the membrane. If the average primary particle size of the zeolite is equal to or greater than the lower limit, the grain boundaries of the zeolite can be made small, resulting in good permeation selectivity. Therefore, it is most preferable that the average primary particle size of the zeolite is the same as the thickness of the zeolite membrane. In this case, the grain boundaries of the zeolite can be made the smallest. Zeolite membranes obtained by hydrothermal synthesis, which will be described later, are preferred because the zeolite particle size and membrane thickness may be the same. In the present invention, the average primary particle diameter is determined by measuring the primary particle diameters of 30 or more arbitrarily selected particles when observing the surface or fracture surface of the zeolite membrane composite of the present invention with a scanning electron microscope, and then averaging the measured values.

[0099] The shape of the zeolite membrane is not particularly limited, and any shape can be adopted, such as tubular, hollow fiber, monolith, honeycomb, etc. The size of the zeolite membrane is also not particularly limited, and it is formed, for example, as a zeolite membrane composite formed on a porous support having the size described below.

[0100] (Porous support) In the present invention, the zeolite membrane is preferably formed on the surface of a porous support, etc. Preferably, the zeolite is crystallized in the form of a membrane on the porous support.

[0101] The porous support used in the present invention preferably has chemical stability sufficient to allow zeolite to crystallize into a membrane on its surface. Suitable porous supports include gas-permeable porous polymers such as polysulfone, cellulose acetate, aromatic polyamide, vinylidene fluoride, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, polytetrafluoroethylene, and polyimide; sintered ceramics such as silica, α-alumina, γ-alumina, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide; sintered metals and mesh-like molded bodies such as iron, bronze, and stainless steel; and inorganic porous bodies such as glass and carbon molded bodies. Among these, inorganic porous supports such as sintered ceramics, sintered metals, glass, and carbon molded bodies are preferred for use in ammonia separation at high temperatures because of their excellent mechanical strength, deformation resistance, thermal stability, and reactivity resistance at high temperatures. The inorganic porous support is preferably a sintered ceramic, a solid material whose basic or majority components are composed of inorganic non-metallic substances.

[0102] As described above, preferred ceramic sintered bodies include ceramic sintered bodies containing α-alumina, γ-alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, etc., but these may be sintered bodies of a single material or a mixture of two or more materials sintered together. A part of the surface of these ceramic sintered bodies may be converted into zeolite during zeolite membrane synthesis, which increases the adhesion between the porous support and the zeolite membrane, thereby improving the durability of the zeolite membrane composite. In particular, inorganic porous supports containing at least one of alumina, silica, and mullite are more preferred because they can be easily partially zeoliteized, resulting in a stronger bond between the inorganic porous support and the zeolite, making it easier to form a dense zeolite membrane with high separation performance. The porous support used in the present invention preferably has, on its surface (hereinafter also referred to as "porous support surface"), the action of crystallizing the zeolite formed on the porous support. The pore size of the surface of the porous support is preferably controlled. The average pore size of the porous support near the surface is usually 0.02 μm or more, preferably 0.05 μm or more. The pore size is preferably 0.1 μm or more, more preferably 0.1 μm or more, more preferably 0.15 μm or more, even more preferably 0.5 μm or more, particularly preferably 0.7 μm or more, and most preferably 1.0 μm or more, and is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less, and particularly preferably 2 μm or less. By using a porous support having a pore size in this range, a dense zeolite membrane that improves ammonia permeation selectivity can be formed. The surface of the porous support is preferably smooth, and the surface may be polished with a file or the like, if necessary. The pore size of the porous support used in the present invention in the portion other than the vicinity of the surface of the porous support is not limited and does not need to be particularly controlled, but the porosity of the other portion is usually 20% or more, more preferably 30% or more, and usually 60% or less, preferably 50% or less. The porosity of the portion other than the vicinity of the surface of the porous support affects the permeation flow rate when separating gas or liquid, and when the porosity is above the above-mentioned lower limit, the permeate tends to diffuse easily, while when it is below the above-mentioned upper limit, it tends to be easier to prevent a decrease in the strength of the porous support. In addition, as a method of controlling the permeation flow rate, a porous support formed by combining porous bodies with different porosities in layers may be used. The shape of the porous support used in the present invention is not limited as long as it can effectively separate mixed gases or liquid mixtures, and specific examples include flat, tubular, cylindrical, honeycomb-shaped structures with numerous through-holes, and monolithic structures. The size of the porous support is optional and may be appropriately selected and adjusted so as to obtain the desired zeolite membrane composite. Among these, a tubular shape of the porous support may be preferable. The length of the tubular porous support is not particularly limited, but is usually 2 cm or more, preferably 4 cm or more, more preferably 5 cm or more, particularly preferably 10 cm or more, particularly preferably 40 cm or more, and most preferably 50 cm or more, and is usually 200 cm or less, preferably 150 cm or less, and more preferably 100 cm or less. When the length of the porous support is equal to or greater than the above-mentioned lower limit, the amount of mixed gas separated per support can be increased, thereby reducing equipment costs. When the length is equal to or less than the above-mentioned upper limit, the production of the zeolite membrane composite can be simplified, and further, problems such as fragility due to vibration during use can be prevented. The inner diameter of the tubular porous support is usually 0.1 cm or more, preferably 0.2 cm or more, more preferably 0.3 cm or more, particularly preferably 0.4 cm or more, and usually 2 cm or less, preferably 1.5 cm or less, more preferably 1.2 cm or less, and particularly preferably 1.0 cm or less. The outer diameter is usually 0.2 cm or more, preferably 0.3 cm or more, more preferably 0.6 cm or more, and particularly preferably 1.0 cm or more, and usually 2.5 cm or less, preferably 1.7 cm or less, and more preferably 1.3 cm or less. The wall thickness of the tubular porous support is usually 0.1 mm or more, preferably 0.3 mm or more, more preferably 0.5 mm or more, even more preferably 0.7 mm or more, even more preferably 1.0 mm or more, and particularly preferably 1.2 mm or more, and usually 4 mm or less, preferably 3 mm or less, and more preferably 2 mm or less. If the inner diameter, outer diameter, and wall thickness of the tubular porous support are each above the above lower limit, the strength of the support can be improved and it can be made less likely to break. Furthermore, if the inner diameter and outer diameter of the tubular support are each equal to or less than the above upper limit, the size of the equipment required for ammonia separation can be reduced, which can be economically advantageous. Furthermore, if the wall thickness of the tubular support is equal to or less than the above upper limit, the permeation performance tends to be improved.

[0103] The rate of change in the thermal expansion coefficient of the porous support used in the fifth embodiment at 300°C relative to that at 30°C is, in absolute value, 0.25% or less, preferably 0.20% or less, more preferably 0.15% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less. That is, the rate of change in the thermal expansion coefficient of the porous support of zeolite membrane composite E at 300°C relative to that at 30°C is within ±0.25%, preferably within ±0.20%, more preferably within ±0.15%, particularly preferably within ±0.10%, and most preferably within ±0.05%. On the other hand, the rate of change in the thermal expansion coefficient of the porous support of zeolite membrane composite E at 400°C relative to that at 30°C is, in absolute value, usually 0.30% or less, preferably 0.25% or less, more preferably 0.20% or less, particularly preferably 0.15% or less, and most preferably 0.10% or less. That is, the rate of change in the thermal expansion coefficient of the porous support at 400° C. relative to the thermal expansion coefficient at 30° C. is within ±0.30%, preferably within ±0.25%, more preferably within ±0.20%, particularly preferably within ±0.15%, and most preferably within ±0.10%. A zeolite membrane composite formed on a porous support having such a low thermal expansion coefficient is unlikely to develop cracks in the zeolite membrane due to the thermal expansion (contraction) of the porous support when the composite is heated, for example, at temperatures exceeding 200° C., even at temperatures exceeding 300° C., in order to allow ammonia to permeate from a gas mixture containing ammonia and multiple components including hydrogen and / or nitrogen. Therefore, ammonia can be stably and efficiently separated to the permeation side at high permeability even under high-temperature conditions.

[0104] Furthermore, the ratio of the rate of change in the thermal expansion coefficient of the porous support used in the fifth embodiment at 30°C to the rate of change in the thermal expansion coefficient of the porous support at 300°C to the rate of change in the thermal expansion coefficient of the porous support at 30°C is usually 120% or less, preferably 115% or less, more preferably 110% or less, particularly preferably 105% or less, and most preferably 103% or less, in absolute terms. A zeolite membrane composite formed on a porous support exhibiting such a specific ratio of thermal expansion coefficients between specific temperatures can suppress the occurrence of cracks in the zeolite membrane that follow local thermal expansion (contraction) of the porous support, even when non-uniform heat generation occurs in a reactor during ammonia production, for example, and therefore can efficiently separate ammonia to the permeation side at high permeability stably even under high-temperature conditions.

[0105] (Zeolite membrane composite) In the present invention, the zeolite membrane is preferably used as a zeolite membrane composite comprising at least zeolite and a support. In the present invention, the zeolite membrane composite is a composite in which the above-mentioned zeolite is fixed in the form of a membrane, preferably in a crystallized state, to the surface of the above-mentioned porous support, and in some cases, it is preferable that a part of the zeolite is fixed to the inside of the support. The zeolite membrane composite is preferably, for example, one in which zeolite is crystallized into a membrane on the surface of a porous support by hydrothermal synthesis.

[0106] The position of the zeolite membrane on the porous support is not particularly limited. When a tubular support is used, the zeolite membrane may be formed on the outer surface, the inner surface, or even on both surfaces depending on the application system. The zeolite membrane may be formed by laminating it on the surface of the support, or may be crystallized so as to fill the pores in the surface layer of the support. In this case, it is important that the crystallized membrane layer does not have cracks or continuous micropores, and forming a so-called dense membrane is preferable in terms of improving separation performance.

[0107] Furthermore, there are no particular limitations on the zeolite and support that constitute the zeolite membrane composite, and it is preferable to use any combination of the above-mentioned zeolites and supports. Among these, particularly preferred combinations of zeolite and porous support include an MFI type zeolite-porous alumina support, an RHO type zeolite-porous alumina support, a DDR type zeolite-porous alumina support, an AFI type zeolite-porous alumina support, a CHA type zeolite-porous alumina support, and an AEI type zeolite-porous alumina support, and preferably a CHA type zeolite-porous alumina support, an MFI type zeolite-porous alumina support, and an RHO type zeolite-porous alumina support, and more preferably an MFI type zeolite-porous alumina support and an RHO type zeolite-porous alumina support. In one embodiment of the present invention (zeolite membranes B to E), an MFI type zeolite-porous alumina support or an RHO type zeolite-porous alumina support is preferred, and an RHO type zeolite-porous alumina support is more preferred.

[0108] <Method of manufacturing zeolite membrane composite> In the present invention, the method for forming the zeolite membrane composite is not particularly limited as long as it is a method capable of forming the above-mentioned zeolite membrane on a porous support, and it can be produced by any known method. For example, any of the following methods can be used: (1) a method of crystallizing zeolite into a membrane on a support, (2) a method of fixing zeolite to a support with an inorganic binder or an organic binder, (3) a method of fixing a polymer in which zeolite is dispersed to a support, and (4) a method of impregnating a support with a zeolite slurry and, in some cases, suctioning the zeolite to fix the zeolite to the support.

[0109] Among these, a method of crystallizing zeolite in a membrane form on a porous support is particularly preferred. Although there are no particular limitations on the crystallization method, a method of placing the support in a reaction mixture for hydrothermal synthesis used to produce zeolite (hereinafter, this may be referred to as an "aqueous reaction mixture") and directly carrying out hydrothermal synthesis to crystallize zeolite on the surface of the support is preferred. In this case, the zeolite membrane composite can be produced, for example, by placing an aqueous reaction mixture homogenized by adjusting the composition in a heat-resistant and pressure-resistant container such as an autoclave containing a porous support therein, sealing the container, and heating the container for a certain period of time.

[0110] The aqueous reaction mixture contains a Si atom source, an Al atom source, an alkali source, and water, and further contains an organic template (structure directing agent) as needed. To facilitate a deeper understanding of the method for producing a zeolite membrane composite, the methods for producing an RHO-type zeolite membrane composite and an MFI-type zeolite membrane composite will be described in detail below as representative examples. However, the zeolite membrane and the method for producing the same of the present invention are not limited thereto.

[0111] (RHO type zeolite membrane) The RHO-type zeolite used in the present invention refers to a zeolite with an RHO structure, a code for specifying the structure of zeolites established by the International Zeolite Association (IZA). RHO-type zeolite has a structure characterized by three-dimensional pores consisting of eight-membered oxygen rings with a diameter of 3.6 × 3.6 Å, and this structure is characterized by X-ray diffraction data. The framework density of the RHO-type zeolite used in the present invention is 14.1T / 1000Å. 3 More than 10 ... It means the number of atoms constituting the external framework, and this value is determined by the structure of the zeolite. The relationship between the framework density and the structure of the zeolite is shown in ATLAS OF ZEOLITE FRAMEWORK TYPES Fifth Revised Edition 2007 ELSEVIER.

[0112] (MFI-type zeolite membrane) The MFI-type zeolite used in the present invention refers to that with an MFI structure defined by the code that defines the structure of zeolites determined by the International Zeolite Association (IZA). The MFI-type zeolite has a structure characterized by three-dimensional pores composed of 10-membered oxygen rings with a diameter of 5.1×5.5 Å or 5.3×5.6 Å, and its structure is characterized by X-ray diffraction data. The framework density of the MFI-type zeolite used in the present invention is 17.9 T / 1000 Å. The framework density means the number of atoms outside the oxygen 3 per 1000 Å of the zeolite constituting the external framework, and this value is determined by the structure of the zeolite and the relationship between the framework density and the structure of the zeolite is shown in ATLAS OF ZEOLITE FRAMEWORK TYPES Fifth Revised Edition 2007 ELSEVIER.

[0113] <Method for producing RHO-type zeolite membrane>

[0114] (Silicon atom source) The silicon (Si) atom source used in the aqueous reaction mixture is not particularly limited, and examples thereof include aluminosilicate zeolite, fumed silica, colloidal silica, amorphous silica, sodium silicate, methyl silicate, ethyl silicate, silicon alkoxides such as trimethylethoxysilane, tetraethyl orthosilicate, and aluminosilicate gel, with aluminosilicate zeolite, fumed silica, colloidal silica, amorphous silica, sodium silicate, methyl silicate, ethyl silicate, silicon alkoxides, and aluminosilicate gel being preferred. These may be used alone or in combination of two or more.

[0115] The Si atom source is used so that the amounts of the other raw materials used relative to the Si atom source fall within the preferred ranges described above or below.

[0116] (Aluminum atom source) The aluminum (Al) atom source used in the production of the porous support-RHO-type zeolite membrane composite is not particularly limited, and examples thereof include aluminosilicate zeolite, amorphous aluminum hydroxide, aluminum hydroxide having a gibbsite structure, aluminum hydroxide having a bayerite structure, aluminum nitrate, aluminum sulfate, aluminum oxide, sodium aluminate, boehmite, pseudo-boehmite, aluminum alkoxide, and aluminosilicate gel. Of these, aluminosilicate zeolite, amorphous aluminum hydroxide, sodium aluminate, boehmite, pseudo-boehmite, aluminum alkoxide, and aluminosilicate gel are preferred, and aluminosilicate zeolite, amorphous aluminum hydroxide, sodium aluminate, and aluminosilicate gel are particularly preferred. These may be used alone or in combination of two or more.

[0117] The aluminosilicate zeolite may be used alone or in combination of two or more. When an aluminosilicate zeolite is used as the Al atom source, it is preferable that the aluminosilicate zeolite accounts for 50 mass% or more, particularly 70 to 100 mass%, and especially 90 to 100 mass% of the total Al atom source. When an aluminosilicate zeolite is used as the Si atom source, it is preferable that the aluminosilicate zeolite accounts for 50 mass% or more, particularly 70 to 100 mass%, and especially 90 to 100 mass% of the total Si atom source. When the proportion of the aluminosilicate zeolite is within this range, the Si atom / Al atom molar ratio of the RHO-type zeolite membrane is high, resulting in a zeolite membrane with excellent acid resistance and water resistance and a wide range of applications.

[0118] The preferred range of the amount of Al atom source (including the above-mentioned aluminosilicate zeolite and other Al atom sources) used relative to the silicon (Si atoms) contained in the raw material mixture other than the seed crystals (Al atom / Si atom ratio) is usually 0.01 or more, preferably 0.02 or more, more preferably 0.04 or more, and even more preferably 0.06 or more, and usually 1.0 or less, preferably 0.5 or less, more preferably 0.2 or less, and even more preferably 0.1 or less. Controlling the amount used within this range makes it easier to control the contents of nitrogen atoms and alkali metal elements in the zeolite within the preferred ranges of the present invention. Furthermore, the Al atom / Si atom ratio can be increased by reducing the amount of silicon atom source used relative to the aluminum atom source, while the ratio can be decreased by increasing the amount of silicon atom source used relative to the aluminum atom source.

[0119] In some embodiments of the present invention (for example, Inventions B to E), if the Al atom / Si atom ratio exceeds 1.0, the water resistance and acid resistance of the obtained RHO type zeolite membrane may be low, and the applications of the zeolite membrane may be limited. If the Al atom / Si atom ratio is less than 0.01, it may be difficult to obtain an RHO type zeolite membrane.

[0120] The aqueous reaction mixture may contain, in addition to the silicon atom source and the aluminum atom source, other atom sources such as gallium (Ga), iron (Fe), boron (B), titanium (Ti), zirconium (Zr), tin (Sn), and zinc (Zn).

[0121] The type of alkali used as the alkali source is not particularly limited, and alkali metal hydroxides and alkaline earth metal hydroxides can be used.

[0122] The metal species of these metal hydroxides are usually sodium (Na), potassium (K), lithium (Li), rubidium (Rb), cesium (Cs), calcium (Ca), magnesium (Mg), strontium (Sr), and barium (Ba), preferably Na, K, and Cs, and more preferably Na and Cs. Two or more metal species of the metal oxides may be used in combination, and specifically, it is preferable to use Na and Cs in combination. Specific examples of metal hydroxides that can be used include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide; and alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide, strontium hydroxide, and barium hydroxide.

[0123] Additionally, hydroxide ions, which are counter anions of the organic template described below, can be used as the alkali source for the aqueous reaction mixture.

[0124] In the crystallization of the zeolite according to the present invention, an organic template (structure-directing agent) is not necessarily required. However, by using a type of organic template corresponding to each structure, the ratio of silicon atoms to aluminum atoms in the crystallized zeolite increases, thereby improving the crystallinity, and therefore it is preferable to use an organic template.

[0125] The organic template may be of any type as long as it can form the desired zeolite membrane, and one type of template may be used, or two or more types may be used in combination.

[0126] The type of organic template suitable for the reaction varies depending on the zeolite structure to be synthesized, and an organic template that can obtain the desired zeolite structure may be used. Specifically, for example, in the case of the RHO structure, 18-crown-6-ether or the like may be used.

[0127] When the organic template is a cation, it is accompanied by an anion that is not detrimental to the formation of the zeolite. Representative of such anions are Cl. - , Br - , I - These include halogen ions, hydroxide ions, acetates, sulfates, and carboxylates, etc. Among these, hydroxide ions are particularly preferred, and in the case of hydroxide ions, they function as an alkali source as described above.

[0128] The ratio of the Si atom source to the organic template in the aqueous reaction mixture was determined as follows: The molar ratio of the plate (organic template / SiO2 ratio) is usually 0.005 or more, preferably is 0.01 or more, more preferably 0.02 or more, even more preferably 0.05 or more, particularly preferably 0.08 or more, and most preferably 0.1 or more, and is usually 1 or less, preferably 0. The organic template / SiO2 ratio in the aqueous reaction mixture is preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.35 or less, particularly preferably 0.30 or less, and most preferably 0.25 or less. When the organic template / SiO2 ratio in the aqueous reaction mixture is within this range, a dense zeolite membrane can be produced, and a zeolite with excellent acid resistance and low Al atom detachment can be obtained. Furthermore, under these conditions, a particularly dense and acid-resistant RHO-type aluminosilicate zeolite can be formed.

[0129] The use of an appropriate amount of alkali metal atom source facilitates the coordination of the organic structure-directing agent (described below) with aluminum in a suitable state, thereby facilitating the formation of a crystal structure. The molar ratio (R / Si atom) of the alkali metal atom source (R) to the silicon (Si atom) contained in the raw material mixture for hydrothermal synthesis other than the seed crystal is usually 0.1 or more, preferably 0.15 or more, more preferably 0.20 or more, even more preferably 0.25 or more, particularly preferably 0.30 or more, and particularly preferably 0.35 or more, and is usually 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less, even more preferably 0.8 or less, particularly preferably 0.6 or less, and most preferably 0.5 or less.

[0130] If the molar ratio of the alkali metal atom source to silicon (R / Si atoms) is greater than the above upper limit, the produced zeolite tends to dissolve, which may result in failure to obtain zeolite or a significantly reduced yield. If the R / Si atoms is less than the above lower limit, the raw material Al atom source and Si atom source do not dissolve sufficiently, which may result in failure to obtain a uniform raw material mixture for hydrothermal synthesis, making it difficult to produce RHO-type zeolite.

[0131] (amount of water) The amount of water in the raw material mixture for hydrothermal synthesis, expressed as a molar ratio to the silicon (Si atoms) contained in the raw material mixture other than the seed crystals, is usually 10 or more, preferably 20 or more, more preferably 30 or more, even more preferably 40 or more, and particularly preferably 50 or more, and is usually 200 moles or less, preferably 150 or less, more preferably 100 or less, even more preferably 80 or less, and particularly preferably 60 or less. If the molar ratio is greater than the upper limit, the reaction mixture may be too dilute, making it difficult to form a defect-free, dense membrane. If the molar ratio is less than 10, the reaction mixture may be too concentrated, making it easy for spontaneous nuclei to form, which may inhibit the growth of RHO zeolite from the support and make it difficult to form a dense membrane.

[0132] (seed crystal) In the present invention, seed crystals may be used as one component of the raw material (raw material compound) for producing "zeolite." During hydrothermal synthesis, it is not necessary to have seed crystals present in the reaction system, but the presence of seed crystals can promote the crystallization of zeolite on the porous support. The method for having seed crystals present in the reaction system is not particularly limited, and methods such as adding seed crystals to the aqueous reaction mixture, as in the synthesis of powdered zeolite, or attaching seed crystals to the support can be used. In the present invention, however, it is preferable to attach seed crystals to the support. Attaching seed crystals to the support in advance makes it easier to produce a dense zeolite membrane with high separation performance.

[0133] The seed crystals to be used may be of any type as long as they are zeolite that promotes crystallization, but for efficient crystallization, they preferably have the same crystal type as the zeolite membrane to be formed. For example, when forming a zeolite membrane of RHO-type aluminosilicate, it is preferable to use seed crystals of RHO-type zeolite.

[0134] The particle size of the seed crystals is preferably close to the pore size of the support, and they may be crushed before use as necessary. The particle size is usually 20 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. It is usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less, and particularly preferably 1.5 μm or less. Depending on the pore size of the support, a smaller particle size of the seed crystal may be desirable, and the seed crystal may be crushed as necessary. The particle size of the seed crystal is usually 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more, and usually 5 μm or less, preferably 3 μm or less, and more preferably 2 μm or less.

[0135] The method for attaching seed crystals to a support is not particularly limited. For example, a dip method in which seed crystals are dispersed in a solvent such as water and the support is immersed in the dispersion to attach the seed crystals to the surface; a suction method in which seed crystals are dispersed in a solvent such as water and the support, with one end sealed, is immersed in the dispersion and then suctioned from the other end to firmly attach the seed crystals to the support surface; or a method in which seed crystals are mixed with a solvent such as water to form a slurry and then applied to the support. The dip and suction methods are desirable for controlling the amount of seed crystal attachment and producing zeolite membranes with good reproducibility, while the suction and suction methods in which seed crystals are applied in a slurry state are desirable for adhering the seed crystals to the support. Furthermore, for the purpose of adhering the seed crystals to the support and / or removing excess seed crystals, rubbing and pressing the support to which the seed crystals are attached with a finger wearing a latex glove is also preferably performed after the dip or suction method.

[0136] The solvent in which the seed crystals are dispersed is not particularly limited, but water or an alkaline aqueous solution is particularly preferred. The type of alkaline aqueous solution is not particularly limited, but a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is preferred. These alkaline species may also be mixed. The alkali concentration of the alkaline aqueous solution is not particularly limited, but is usually 0.0001 mol% or more, preferably 0.0002 mol% or more, more preferably 0.001 mol% or more, and even more preferably 0.002 mol% or more. The alkali concentration is also usually 1 mol% or less, preferably 0.8 mol% or less, more preferably 0.5 mol% or less, and even more preferably 0.2 mol% or less.

[0137] The solvent in which the seed crystals are dispersed is not particularly limited, but water is particularly preferred. The amount of seed crystals to be dispersed is not particularly limited, and is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, particularly preferably 2% by mass or more, and most preferably 3.0% by mass or more, based on the total weight of the dispersion. Furthermore, the amount is usually 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less.

[0138] If the amount of dispersed seed crystals is too small, the amount of seed crystals attached to the support will be small, which may result in areas on the support where zeolite is not produced during hydrothermal synthesis, resulting in a defective membrane. On the other hand, for example, the amount of seed crystals attached to the porous support by the dipping method becomes almost constant when the amount of seed crystals in the dispersion exceeds a certain level, so if the amount of seed crystals in the dispersion is too large, a lot of seed crystals will be wasted, which is disadvantageous in terms of cost.

[0139] It is desirable to attach seed crystals to a support by dipping, suction, or by applying a slurry, and then dry the resulting mixture before forming a zeolite membrane. The drying temperature is usually 50°C or higher, preferably 80°C or higher, and more preferably 100°C or higher, and usually 200°C or lower, preferably 180°C or lower, and more preferably 150°C or lower. The drying time is not problematic as long as the mixture is sufficiently dried, but is usually 10 minutes or longer, preferably 30 minutes or longer. There is no particular upper limit, but from an economical viewpoint, it is usually 5 hours or shorter.

[0140] After drying, the support to which the seed crystals are attached is preferably rubbed and pressed with fingers or the like wearing latex gloves, in order to adhere the seed crystals to the support and / or to remove excess seed crystals.

[0141] The amount of seed crystals to be attached to the porous support in advance is not particularly limited, and the amount is determined by the number of crystals per 1 m of the membrane-forming surface of the porous support. 2 The mass per unit area is usually 0.1 g or more, preferably 0.3 g or more, more preferably It is preferably 0.5 g or more, more preferably 0.80 g or more, and most preferably 1.0 g or more, and is usually 100 g or less, preferably 50 g or less, more preferably 10 g or less, even more preferably 8 g or less, and most preferably 5 g or less.

[0142] If the amount of seed crystals attached is less than the above lower limit, crystals tend to be difficult to form, resulting in insufficient or uneven membrane growth. Furthermore, if the amount of seed crystals exceeds the above upper limit, the seed crystals may increase the surface irregularities, or seed crystals that fall off the support may facilitate spontaneous nucleation, inhibiting membrane growth on the support. In either case, it tends to be difficult to produce a dense zeolite membrane.

[0143] When forming a zeolite membrane on a porous support by hydrothermal synthesis, there is no particular limitation on the method for immobilizing the support, and any form such as vertical placement, horizontal placement, etc. In this case, the zeolite membrane may be formed by a static method, or may be formed while stirring the aqueous reaction mixture.

[0144] Hydrothermal synthesis is carried out by placing the support carrying the seed crystals as described above and the prepared hydrothermal synthesis mixture or an aqueous gel obtained by aging the mixture in a pressure-resistant container, and maintaining the mixture at a predetermined temperature under self-generated pressure or under a gas pressure that does not inhibit crystallization, while stirring, rotating or rocking the container, or leaving it stationary. Hydrothermal synthesis in a stationary state is desirable because it does not inhibit crystal growth from the seed crystals on the support.

[0145] The reaction temperature when forming a zeolite membrane by hydrothermal synthesis is not particularly limited, and may be any temperature suitable for obtaining a membrane with the desired zeolite structure. It is usually 100°C or higher, preferably 110°C or higher, more preferably 120°C or higher, particularly preferably 130°C or higher, particularly preferably 140°C or higher, and most preferably 150°C or higher, and usually 200°C or lower, preferably 190°C or lower, more preferably 180°C or lower, and even more preferably 170°C or lower. If the reaction temperature is too low, the zeolite may be difficult to crystallize. If the reaction temperature is too high, a type of zeolite different from the desired zeolite may be easily produced.

[0146] The heating (reaction) time when forming a zeolite membrane by hydrothermal synthesis is not particularly limited, and may be any time suitable for obtaining a membrane with the desired zeolite structure. It is usually 3 hours or more, preferably 8 hours or more, more preferably 12 hours or more, and particularly preferably 15 hours or more, and usually 10 days or less, preferably 5 days or less, more preferably 3 days or less, even more preferably 2 days or less, and particularly preferably 1.5 days or less. If the reaction time is too short, the zeolite may be difficult to crystallize. If the reaction time is too long, a type of zeolite different from the desired zeolite may be easily produced.

[0147] The pressure during hydrothermal synthesis is not particularly limited, and the autogenous pressure that occurs when an aqueous reaction mixture placed in a sealed vessel is heated to the above-mentioned temperature range is sufficient. If necessary, an inert gas such as nitrogen may be added.

[0148] The density of the zeolite membrane can be improved by repeating the hydrothermal synthesis multiple times. When the hydrothermal synthesis is repeated multiple times, the zeolite membrane composite obtained in the first hydrothermal synthesis is washed with water, dried by heating, and then immersed again in a newly prepared aqueous reaction mixture for hydrothermal synthesis. The zeolite membrane composite obtained after the first hydrothermal synthesis does not necessarily need to be washed with water or dried, but washing with water and drying can maintain the intended composition of the aqueous reaction mixture. When the synthesis is performed multiple times, the number of synthesis times is usually two or more and usually ten or less, preferably five or less, and more preferably three or less. The water washing may be repeated once or multiple times.

[0149] The zeolite membrane composite obtained by hydrothermal synthesis is washed with water, then heat-treated, and dried. Here, heat treatment means drying the zeolite membrane composite by applying heat, and also means removing an organic template, if used, by calcining the organic template.

[0150] When the purpose of the heat treatment is drying, the temperature is usually 50° C. or higher, preferably 80° C. or higher, more preferably 100° C. or higher, and usually 200° C. or lower, preferably 150° C. or lower. When the purpose of the heat treatment is to remove the organic template by calcination, the temperature is usually 250° C. or higher, preferably 300° C. or higher, more preferably 350° C. or higher, even more preferably 400° C. or higher, and usually 800° C. or lower, preferably 600° C. or lower, even more preferably 550° C. or lower, particularly preferably 500° C. or lower.

[0151] When the purpose is to remove the organic template by calcination, if the heat treatment temperature is too low, the proportion of the organic template remaining tends to be high, reducing the number of pores in the zeolite and potentially reducing the amount of permeation when used to separate ammonia. If the heat treatment temperature is too high, the difference in the thermal expansion coefficients between the support and the zeolite becomes large, which may lead to the likelihood of cracks occurring in the zeolite membrane, causing the zeolite membrane to lose its denseness and resulting in reduced separation performance.

[0152] The heat treatment time is not particularly limited as long as it is sufficient to sufficiently dry the zeolite membrane and remove the organic template by calcination, and is preferably 0.5 hours or more, more preferably 1 hour or more, for the purpose of drying, and is preferably 1 hour or more, more preferably 5 hours or more, for the purpose of removing the organic template by calcination, although this varies depending on the temperature increase rate and temperature decrease rate. The upper limit of the heating time is not particularly limited, and is usually 200 hours or less, preferably 150 hours or less, more preferably 100 hours or less.

[0153] The heat treatment for calcining the template may be carried out in an air atmosphere, but may also be carried out in an atmosphere containing an inert gas such as nitrogen or oxygen.

[0154] When the hydrothermal synthesis is carried out in the presence of an organic template, it is appropriate to wash the obtained zeolite membrane composite with water and then remove the organic template by, for example, a heat treatment or extraction, preferably by the above-mentioned heat treatment, i.e., calcination.

[0155] In the heat treatment for the purpose of firing and removing the organic template, the heating rate should be made as slow as possible in order to prevent cracks from occurring in the zeolite membrane due to the difference in the thermal expansion coefficients of the porous support and the zeolite. The heating rate is usually 5 °C / min or less, preferably 2 °C / min or less, more preferably 1 °C / min or less, still more preferably 0.5 °C / min or less, and particularly preferably 0.3 °C / min or less. The lower limit of the heating rate is usually 0.1 °C / min or more in consideration of workability.

[0156] Also, in the heat treatment for the purpose of firing and removing the organic template, it is necessary to control the cooling rate after the heat treatment in order to avoid cracks from occurring in the zeolite membrane. Similar to the heating rate, the slower the cooling rate, the more desirable. The cooling rate is usually 5 °C / min or less, preferably 2 °C / min or less, more preferably 1 °C / min or less, still more preferably 0.5 °C / min or less, and particularly preferably 0.3 °C / min or less. The lower limit of the cooling rate is usually 0.1 °C / min or more in consideration of workability. <Method for Producing MFI-Type Zeolite Membrane>

[0157] (Silicon Atom Source) Examples of the silicon (Si) atom source used in the aqueous reaction mixture include aluminosilicate zeolite, fumed silica, colloidal silica, amorphous silica, sodium silicate, methyl silicate, ethyl silicate, silicon alkoxides such as trimethylethoxysilane, tetraethyl orthosilicate, aluminosilicate gel, etc. Preferably, fumed silica, colloidal silica, amorphous silica, sodium silicate, methyl silicate, ethyl silicate, silicon alkoxide, aluminosilicate gel are mentioned. These may be used alone or in combination of two or more.

[0158] The Si atom source is used such that the usage amounts of other raw materials with respect to the Si atom source are within the suitable ranges described above or below.

[0159] (Aluminum Atom Source) The aluminum (Al) atom source used in producing the porous support-MFI zeolite membrane composite is not particularly limited, and examples thereof include aluminosilicate zeolite, amorphous aluminum hydroxide, aluminum hydroxide having a gibbsite structure, aluminum hydroxide having a bayerite structure, aluminum nitrate, aluminum sulfate, aluminum oxide, sodium aluminate, boehmite, pseudo-boehmite, aluminum alkoxide, and aluminosilicate gel. Of these, amorphous aluminum hydroxide, sodium aluminate, boehmite, pseudo-boehmite, aluminum alkoxide, and aluminosilicate gel are preferred, and amorphous aluminum hydroxide, sodium aluminate, and aluminosilicate gel are particularly preferred. These may be used alone or in combination of two or more.

[0160] The preferred range of the amount of aluminum atom source (including the above-mentioned aluminosilicate zeolite and other aluminum atom sources) used relative to the silicon (Si atoms) contained in the raw material mixture other than the seed crystals (Al atom / Si atom ratio) is, in terms of molar ratio, usually 0.001 or more, preferably 0.002 or more, more preferably 0.003 or more, and even more preferably 0.004 or more, and usually 1.0 or less, preferably 0.5 or less, more preferably 0.2 or less, and even more preferably 0.1 or less. Controlling the amount used within this range makes it easier to control the contents of nitrogen atoms and alkali metal elements in the zeolite within the preferred ranges of the present invention. In order to increase the Al atom / Si atom ratio, the amount of silicon atom source used relative to the aluminum atom source can be reduced, while in order to decrease this ratio, the amount of silicon atom source used relative to the aluminum atom source can be increased.

[0161] The aqueous reaction mixture may contain, in addition to the Si atom source and the Al atom source, other atom sources such as Ga, Fe, B, Ti, Zr, Sn, and Zn.

[0162] The type of alkali used as the alkali source is not particularly limited, and alkali metal hydroxides and alkaline earth metal hydroxides can be used.

[0163] Specific examples of metal hydroxides that can be used include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide; and alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide, strontium hydroxide, and barium hydroxide.

[0164] Additionally, hydroxide ions, which are counter anions of the organic template described below, can be used as the alkali source for the aqueous reaction mixture.

[0165] In the crystallization of the zeolite according to the present invention, an organic template is not necessarily required. However, by using a type of organic template (structure-directing agent) corresponding to each structure, the ratio of silicon atoms to aluminum atoms in the crystallized zeolite increases, thereby improving the crystallinity, and therefore it is preferable to use an organic template.

[0166] The organic template may be of any type as long as it can form the desired zeolite membrane, and one type of template may be used, or two or more types may be used in combination.

[0167] The type of organic template suitable for the reaction varies depending on the zeolite structure to be synthesized, and an organic template that can obtain the desired zeolite structure may be used. Specifically, for example, tetrapropylammonium hydroxide may be used for the MFI structure.

[0168] When the organic template is a cation, it is accompanied by an anion that is not detrimental to the formation of the zeolite. Representative of such anions are Cl. - , Br - , I -These include halogen ions, hydroxide ions, acetates, sulfates, and carboxylates, etc. Among these, hydroxide ions are particularly preferred, and in the case of hydroxide ions, they function as an alkali source as described above.

[0169] The ratio of the Si atom source to the organic template in the aqueous reaction mixture was determined as follows: The molar ratio of the plate (organic template / SiO2 ratio) is usually 0.005 or more, preferably is 0.01 or more, more preferably 0.02 or more, particularly preferably 0.05 or more, and particularly preferably 0.1 or more, and is usually 1 or less, preferably 0.5 or less, more preferably 0.3 or less, particularly preferably 0.25 or less, and particularly preferably 0.2 or less. When the organic template / SiO2 ratio of the aqueous reaction mixture is within this range, a dense zeolite membrane can be produced, and a zeolite with excellent acid resistance and low Al desorption can be obtained. Furthermore, under these conditions, a particularly dense and acid-resistant MFI-type aluminosilicate zeolite can be formed. The use of an appropriate amount of alkali metal atom source facilitates the coordination of the organic structure-directing agent (described below) with aluminum in a suitable state, thereby facilitating the formation of a crystal structure. The molar ratio R / Si of the alkali metal atom source (R) to the silicon (Si) contained in the mixture of raw materials for hydrothermal synthesis other than the seed crystals is usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, even more preferably 0.04 or more, and particularly preferably 0.05 or more, and is usually 1.0 or less, preferably 0.6 or less, more preferably 0.4 or less, even more preferably 0.2 or less, and particularly preferably 0.1 or less.

[0170] If the molar ratio of the alkali metal atom source to silicon (R / Si) is greater than the upper limit, the produced zeolite is likely to dissolve, which may result in failure to obtain zeolite or a significantly reduced yield. If R / Si is less than the lower limit, the Al atom source and Si atom source as raw materials may not dissolve sufficiently, which may result in failure to obtain a uniform raw material mixture for hydrothermal synthesis, making it difficult to produce MFI zeolite.

[0171] (amount of water) The amount of water in the raw material mixture for hydrothermal synthesis, expressed as a molar ratio to the silicon (Si) contained in the raw material mixture other than the seed crystals, is usually 10 or more, preferably 15 or more, more preferably 20 or more, even more preferably 25 or more, and particularly preferably 30 or more, and is usually 500 moles or less, preferably 300 or less, more preferably 200 or less, even more preferably 150 or less, and particularly preferably 100 or less. If the molar ratio is greater than the upper limit, the reaction mixture may be too dilute, making it difficult to form a defect-free, dense membrane. If the molar ratio is less than 10, the reaction mixture may be too concentrated, making it easier for spontaneous nuclei to form, which may inhibit the growth of MFI zeolite from the support and make it difficult to form a dense membrane.

[0172] (seed crystal) In the present invention, seed crystals may be used as one component of the raw material (raw material compound) for producing "zeolite." During hydrothermal synthesis, it is not necessary to have seed crystals present in the reaction system, but the presence of seed crystals can promote the crystallization of zeolite on the porous support. The method for having seed crystals present in the reaction system is not particularly limited, and methods such as adding seed crystals to the aqueous reaction mixture, as in the synthesis of powdered zeolite, or attaching seed crystals to the support can be used. In the present invention, however, it is preferable to attach seed crystals to the support. Attaching seed crystals to the support in advance makes it easier to produce a dense zeolite membrane with high separation performance.

[0173] The seed crystals to be used may be of any type as long as they are zeolite that promotes crystallization, but for efficient crystallization, they preferably have the same crystal type as the zeolite membrane to be formed. For example, when forming a zeolite membrane of MFI type aluminosilicate, it is preferable to use seed crystals of MFI type zeolite.

[0174] The particle size of the seed crystals is desirably close to the pore size of the support, and they may be crushed before use as necessary. The particle size is usually 1 nm or more, preferably 10 nm or more, more preferably 50 nm or more, even more preferably 0.1 μm or more, particularly preferably 0.5 μm or more, especially preferably 0.7 μm or more, and most preferably 1 μm or more, and is usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less, most preferably 1.5 μm or less, and particularly preferably 1.2 μm or less. Depending on the pore size of the support, a smaller particle size of the seed crystal may be desirable, and the seed crystal may be crushed as necessary. The particle size of the seed crystal is usually 0.5 nm or more, preferably 1 nm or more, and more preferably 2 nm or more, and usually 5 μm or less, preferably 3 μm or less, and more preferably 2 μm or less.

[0175] The method for attaching seed crystals to a support is not particularly limited. For example, a dip method in which seed crystals are dispersed in a solvent such as water and the support is immersed in the dispersion to attach the seed crystals to the surface; a suction method in which seed crystals are dispersed in a solvent such as water and the support, with one end sealed, is immersed in the dispersion and then suctioned from the other end to firmly attach the seed crystals to the support surface; or a method in which seed crystals are mixed with a solvent such as water to form a slurry and then applied to the support. The dip and suction methods are desirable for controlling the amount of seed crystal attachment and producing zeolite membranes with good reproducibility, while the suction and suction methods in which seed crystals are applied in a slurry state are desirable for adhering the seed crystals to the support. Furthermore, for the purpose of adhering the seed crystals to the support and / or removing excess seed crystals, rubbing and pressing the support to which the seed crystals are attached with a finger wearing a latex glove is also preferably performed after the dip or suction method.

[0176] The solvent in which the seed crystals are dispersed is not particularly limited, but water or an alkaline aqueous solution is particularly preferred. The type of alkaline aqueous solution is not particularly limited, but a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is preferred. These alkaline species may also be mixed. The alkali concentration of the alkaline aqueous solution is not particularly limited, but is usually 0.0001 mol% or more, preferably 0.0002 mol% or more, more preferably 0.001 mol% or more, and even more preferably 0.002 mol% or more. The alkali concentration is also usually 1 mol% or less, preferably 0.8 mol% or less, more preferably 0.5 mol% or less, and even more preferably 0.2 mol% or less.

[0177] The solvent in which the seed crystals are dispersed is not particularly limited, but water is particularly preferred. The amount of is not particularly limited, and is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, particularly preferably 2% by mass or more, and most preferably 3% by mass or more, based on the total weight of the dispersion. Also, it is usually 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less.

[0178] If the amount of dispersed seed crystals is too small, the amount of seed crystals attached to the support will be small, which may result in areas on the support where zeolite is not produced during hydrothermal synthesis, resulting in a defective membrane. On the other hand, for example, the amount of seed crystals attached to the porous support by the dipping method becomes almost constant when the amount of seed crystals in the dispersion exceeds a certain level, so if the amount of seed crystals in the dispersion is too large, a lot of seed crystals will be wasted, which is disadvantageous in terms of cost.

[0179] It is desirable to attach seed crystals to a support by dipping, suction, or by applying a slurry, and then dry the resulting mixture before forming a zeolite membrane. The drying temperature is usually 50°C or higher, preferably 80°C or higher, and more preferably 100°C or higher, and usually 200°C or lower, preferably 180°C or lower, and more preferably 150°C or lower. The drying time is not problematic as long as the mixture is sufficiently dried, but is usually 10 minutes or longer, preferably 30 minutes or longer. There is no particular upper limit, but from an economical viewpoint, it is usually 5 hours or shorter.

[0180] After drying, the support to which the seed crystals are attached is preferably rubbed and pressed with fingers or the like wearing latex gloves, in order to adhere the seed crystals to the support and / or to remove excess seed crystals.

[0181] The amount of seed crystals to be attached to the porous support in advance is not particularly limited, and the amount is determined by the number of crystals per 1 m of the membrane-forming surface of the porous support. 2 The mass per unit area is usually 0.1 g or more, preferably 0.3 g or more, more preferably It is preferably 0.5 g or more, more preferably 0.80 g or more, and most preferably 1.0 g or more, and is usually 100 g or less, preferably 50 g or less, more preferably 10 g or less, even more preferably 8 g or less, and most preferably 5 g or less.

[0182] If the amount of seed crystals attached is less than the above lower limit, crystals tend to be difficult to form, resulting in insufficient or uneven membrane growth. Furthermore, if the amount of seed crystals exceeds the above upper limit, the seed crystals may increase the surface irregularities, or seed crystals that fall off the support may facilitate spontaneous nucleation, inhibiting membrane growth on the support. In either case, it tends to be difficult to produce a dense zeolite membrane.

[0183] When forming a zeolite membrane on a porous support by hydrothermal synthesis, there is no particular limitation on the method for immobilizing the support, and any form such as vertical placement, horizontal placement, etc. In this case, the zeolite membrane may be formed by a static method, or may be formed while stirring the aqueous reaction mixture.

[0184] Hydrothermal synthesis is carried out by placing the support carrying the seed crystals as described above and the prepared hydrothermal synthesis mixture or an aqueous gel obtained by aging the mixture in a pressure-resistant container, and maintaining the mixture at a predetermined temperature under self-generated pressure or under a gas pressure that does not inhibit crystallization, while stirring, rotating or rocking the container, or leaving it stationary. Hydrothermal synthesis in a stationary state is desirable because it does not inhibit crystal growth from the seed crystals on the support.

[0185] The reaction temperature when forming a zeolite membrane by hydrothermal synthesis is not particularly limited, and may be any temperature suitable for obtaining a membrane with the desired zeolite structure. The reaction temperature is usually 100°C or higher, preferably 120°C or higher, more preferably 130°C or higher, particularly preferably 140°C or higher, particularly preferably 150°C or higher, and most preferably 160°C or higher, and is usually 200°C or lower, preferably The reaction temperature is preferably 190°C or lower, more preferably 180°C or lower, and particularly preferably 170°C or lower. If the reaction temperature is too low, the zeolite may be difficult to crystallize. If the reaction temperature is too high, a type of zeolite different from the target zeolite may be easily produced.

[0186] The heating (reaction) time when forming a zeolite membrane by hydrothermal synthesis is not particularly limited, and may be any time suitable for obtaining a membrane with the desired zeolite structure, but is usually at least 1 hour, preferably at least 5 hours, and more preferably at least 10 hours, and usually at most 10 days, preferably at most 5 days, more preferably at most 3 days, even more preferably at most 2 days, and particularly preferably at most 1 day. If the reaction time is too short, the zeolite may be difficult to crystallize. If the reaction time is too long, a type of zeolite different from the desired zeolite may be easily produced.

[0187] The pressure during hydrothermal synthesis is not particularly limited, and the autogenous pressure that occurs when an aqueous reaction mixture placed in a sealed vessel is heated to the above-mentioned temperature range is sufficient. If necessary, an inert gas such as nitrogen may be added.

[0188] The density of the zeolite membrane can be improved by repeating the hydrothermal synthesis multiple times. When the hydrothermal synthesis is repeated multiple times, the zeolite membrane composite obtained in the first hydrothermal synthesis is washed with water, dried by heating, and then immersed again in a newly prepared aqueous reaction mixture for hydrothermal synthesis. The zeolite membrane composite obtained after the first hydrothermal synthesis does not necessarily need to be washed with water or dried, but washing with water and drying can maintain the intended composition of the aqueous reaction mixture. When the synthesis is repeated multiple times, the number of synthesis times is usually two or more and usually ten or less, preferably five or less, and more preferably three or less. Washing with water may be performed once or multiple times.

[0189] The zeolite membrane composite obtained by hydrothermal synthesis is washed with water, then heat-treated, and dried. Here, heat treatment means drying the zeolite membrane composite by applying heat, and also means removing an organic template, if used, by calcining the organic template.

[0190] When the purpose of the heat treatment is drying, the temperature is usually 50° C. or higher, preferably 80° C. or higher, more preferably 100° C. or higher, and usually 200° C. or lower, preferably 150° C. or lower. When the purpose of the heat treatment is to remove the organic template by calcination, the temperature is usually 350° C. or higher, preferably 400° C. or higher, more preferably 450° C. or higher, even more preferably 500° C. or higher, and usually 900° C. or lower, preferably 800° C. or lower, even more preferably 700° C. or lower, and particularly preferably 600° C. or lower.

[0191] If the purpose is to remove the organic template by calcination, a too low heat treatment temperature tends to increase the proportion of the organic template remaining, reducing the number of pores in the zeolite and potentially reducing the amount of permeation when used to separate ammonia. If the heat treatment temperature is too high, the difference in thermal expansion coefficient between the support and the zeolite becomes large, which may lead to the likelihood of cracking in the zeolite membrane, causing the zeolite membrane to lose its density and reduce its separation performance. When tetrapropylammonium hydroxide is used as the organic template, the content of nitrogen atoms in the zeolite can be controlled by adjusting the heat treatment temperature.

[0192] The heat treatment time is not particularly limited as long as it is sufficient to sufficiently dry the zeolite membrane and remove the organic template by calcination, and is preferably 0.5 hours or more, more preferably 1 hour or more, for the purpose of drying, and is preferably 1 hour or more, more preferably 5 hours or more, for the purpose of removing the organic template by calcination, although this varies depending on the temperature increase rate and temperature decrease rate. The upper limit of the heating time is not particularly limited, and is usually 200 hours or less, preferably 150 hours or less, more preferably 100 hours or less.

[0193] The heat treatment for calcining the template may be carried out in an air atmosphere, but may also be carried out in an atmosphere containing an inert gas such as nitrogen or oxygen.

[0194] When the hydrothermal synthesis is carried out in the presence of an organic template, it is appropriate to wash the obtained zeolite membrane composite with water and then remove the organic template by, for example, a heat treatment or extraction, preferably by the above-mentioned heat treatment, i.e., calcination.

[0195] The heating rate during the heat treatment for calcining and removing the organic template is desirably as slow as possible to prevent cracks from forming in the zeolite membrane due to the difference in thermal expansion coefficient between the porous support and the zeolite. The heating rate is usually 5°C / min or less, preferably 2°C / min or less, more preferably 1°C / min or less, particularly preferably 0.5°C / min or less, and most preferably 0.3°C / min or less. The lower limit of the heating rate is usually 0.1°C / min or more, taking workability into consideration.

[0196] In addition, in the heat treatment for calcining and removing the organic template, the temperature drop rate after the heat treatment must also be controlled to avoid cracking of the zeolite membrane. As with the temperature increase rate, the slower the temperature drop rate, the more desirable it is. The temperature drop rate is usually 5°C / min or less, preferably 2°C / min or less, more preferably 1°C / min or less, particularly preferably 0.5°C / min or less, and most preferably 0.3°C / min or less. The lower limit of the temperature drop rate is usually 0.1°C / min or more, taking workability into consideration.

[0197] (ion exchange) The synthesized zeolite membrane may be ion-exchanged as needed. In particular, in certain embodiments of the present invention (e.g., the zeolite membranes of Inventions B, C, D, and E), the synthesized zeolite membrane is subjected to an ion-exchange treatment. The thermal expansion characteristics and thermal stability of ammonia separation, which are one of the features of the present invention, are significantly affected by the cation species in the zeolite, and therefore, this ion exchange is an important control method. Furthermore, as described below, the ammonia permeability and / or separation performance of the zeolite membrane may be improved depending on the cation species used. That is, the cation species used in the present invention are appropriately selected taking into account the ammonia permeability and separation performance while maintaining the thermal expansion characteristics and thermal stability of ammonia separation of the zeolite.

[0198] (ion exchange) When a zeolite membrane is synthesized using an organic template, ion exchange is usually performed after removing the organic template. In the present invention, the ions to be exchanged are NH4+ or any of the cationic species obtained by protonating an organic amine having 1 to 20 carbon atoms, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetraamine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N,N-diisopropylethylamine, N,N,N-trimethyl-1-adamantanamine, pyridine, and piperidine, and other cationic species are also preferred. + , K. + , Li + , Rb + , Cs + Alkali metal ions such as Ca 2+ , Mg 2+ , Sr 2+ , Ba 2+ and ions of transition metals such as Fe, Cu, Zn, Ga, and La may coexist. Among these, protons, NH4 + , Na + , Li + , Cs + The preferred cations are Fe ions, Ga ions, and La ions. A plurality of these ions may be present in the zeolite, and the method of having the above ions present in the zeolite is preferably adopted in order to balance the thermal expansion characteristics and ammonia permeability of the zeolite. By controlling the cation species to be ion-exchanged and the amount thereof in this way, the zeolite can be It is possible to control the ammonia affinity of the zeolite and the effective pore size of the zeolite, thereby increasing the ammonia permeation selectivity and improving the ammonia permeation rate. Among these, the ionic species that increase the ammonia permeation selectivity are NH4 +Cationic species obtained by protonating organic amines having 1 to 20 carbon atoms, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetraamine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N,N-diisopropylethylamine, N,N,N-trimethyl-1-adamantanamine, pyridine, and piperidine, are preferred, and among these, NH4 + For the above reasons, cationic species in which small molecular amines such as amines having 1 to 6 carbon atoms are protonated are more preferred, and among these, NH4 + On the other hand, the ion species that improve the ammonia permeation rate are protons, Na + , Li + , Cs + , Fe ions, Ga ions, and La ions are preferred, and Na + , Li + , Cs + The ion is particularly preferred, Na + In the present invention, the molar ratio of nitrogen atoms to Al atoms in the zeolite membrane can be controlled by adjusting the amount of ions exchanged, which essentially include ion species containing nitrogen atoms.

[0199] In addition, the zeolite of the present invention contains Na + When Na ions are contained, the content thereof is, in molar ratio relative to the Al atoms in the zeolite, usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, even more preferably 0.04 or more, and particularly preferably 0.05 or more. The upper limit is not particularly limited, but is usually 0.10 molar equivalents or less, preferably 0.070 molar equivalents or less, more preferably 0.065 molar equivalents or less, even more preferably 0.060 molar equivalents or less, and particularly preferably 0.55 molar equivalents or less. +By using a zeolite with a zeolite / Al atomic ratio, ammonia can be separated with high permeability from a mixed gas consisting of multiple components including ammonia and hydrogen and / or nitrogen.

[0200] Ion exchange can be performed by treating the calcined zeolite membrane (e.g., when an organic template is used) with nitrates, sulfates, phosphates, organic acid salts, hydroxides, and halogen salts of Cl and Br of the cations to be ion-exchanged, or with an acid such as hydrochloric acid, typically at room temperature to 100°C, followed by rinsing with water or hot water at 40°C to 100°C. The solvent used for the ion exchange treatment can be water or an organic solvent as long as it dissolves the salt to be ion-exchanged. The concentration of the salt used is typically 10 mol / L or less, with a lower limit of 0.1 mol / L or more, preferably 0.5 mol / L or more, and more preferably 1 mol / L or more. These treatment conditions can be appropriately set depending on the salt and solvent used. When using an acid such as hydrochloric acid, the acid concentration is typically 5 mol / L or less, as the acid destroys the crystalline structure of the zeolite, and the temperature and time can be appropriately set. Furthermore, since the ion exchange rate increases when the ion exchange treatment is repeated, the number of times the ion exchange treatment is performed is not particularly limited, and the treatment may be repeated until the desired effect is achieved. Furthermore, since the ion-exchanged zeolite membrane may be calcined at 200 to 500°C as necessary to remove the residue from the ion exchange treatment, if any residue from the ion exchange treatment raw materials remains in the zeolite pores after the ion exchange treatment, this will hinder gas permeability.

[0201] (Nitrate treatment) In some embodiments of the present invention (for example, the zeolite membranes of Inventions B, C, D, and E), it is preferable to use a nitrate treatment in combination as a method for adjusting the nitrogen atom content in the zeolite membrane, and the nitrate treatment will be described below.

[0202] In the present invention, the synthesized zeolite membrane may be subjected to a nitrate treatment if necessary. The nitrate treatment may be carried out while the zeolite composite membrane contains an organic template or after the organic template has been removed by calcination. The nitrate treatment is carried out by immersing the zeolite composite membrane in a solution containing a nitrate, for example. This may be preferable because the nitrate can seal fine defects present on the membrane surface. Furthermore, when nitrate is present in the zeolite pores, it has the effect of improving the affinity of the zeolite membrane with ammonia, making it a suitable method for improving ammonia permeability. The solvent used for the nitrate treatment may be water or an organic solvent as long as the salt is soluble therein. There are no limitations on the nitrate used, but examples include magnesium nitrate, calcium nitrate, barium nitrate, aluminum nitrate, gallium nitrate, indium nitrate, iron nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and zinc nitrate. These may be used alone or in combination of two or more. Among these, magnesium nitrate, calcium nitrate, barium nitrate, aluminum nitrate, gallium nitrate, and indium nitrate are preferred, with magnesium nitrate, calcium nitrate, barium nitrate, and aluminum nitrate being more preferred, and aluminum nitrate being particularly preferred because it has a significant effect of sealing fine defects present on the surface of the zeolite membrane, thereby improving ammonia separation performance. The nitrate concentration is usually 10 mol / L or less, with a lower limit of 0.1 mol / L or more, preferably 0.5 mol / L or more, and more preferably 1 mol / L or more. The treatment temperature is usually from room temperature to 150°C or less, and the treatment may be carried out for approximately 10 minutes to 48 hours. These treatment conditions may be appropriately set depending on the type of nitrate and solvent used. The zeolite membrane after the nitrate treatment may be washed with water, and by repeating the water washing, the nitrogen atom content of the zeolite membrane can be adjusted to a preferred range.

[0203] (Aluminum salt treatment) In the present invention, the synthesized zeolite membrane may be subjected to an aluminum salt treatment, if necessary. The aluminum salt treatment may be performed while the zeolite membrane contains the organic template or after the organic template has been removed by calcination. The aluminum salt treatment is performed by immersing the zeolite membrane composite in a solution containing an aluminum salt, for example. This may result in the aluminum salt sealing fine defects present on the membrane surface. Furthermore, when aluminum salt is present in zeolite pores, it has the effect of attracting ammonia, making it a suitable method for improving ammonia permeability. The solvent used for the aluminum salt treatment may be water or an organic solvent as long as the salt dissolves therein. There are no limitations on the aluminum salt used, but examples include aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum acetate, aluminum carbonate, and aluminum hydroxide. These may be used alone or in combination of two or more. The concentration of the aluminum salt is typically 10 mol / L or less, with a lower limit of 0.1 mol / L or more, preferably 0.5 mol / L or more, and more preferably 1 mol / L or more. The treatment temperature is typically between room temperature and 150°C or less, and the treatment may be carried out for approximately 10 minutes to 48 hours. These treatment conditions may be appropriately set depending on the aluminum salt and solvent type used. The zeolite membrane after aluminum salt treatment may be washed with water, and the Al atom content of the zeolite membrane can be adjusted by repeated washing with water. To increase the Si atom / Al atom ratio of the present invention, it is preferable to reduce the concentration or treatment amount of the aluminum salt used for treatment or increase the number of water washes after aluminum salt treatment. Conversely, to decrease the ratio, it is preferable to increase the concentration or treatment amount of the aluminum salt used for treatment or reduce the number of water washes after aluminum salt treatment.

[0204] (Silylation treatment) In the present invention, the synthesized zeolite membrane may be subjected to a silylation treatment if necessary. The silylation treatment is carried out by immersing the zeolite membrane composite in a solution containing, for example, a Si compound. This allows the zeolite membrane surface to be modified with the Si compound, and the membrane can have specific physicochemical properties. For example, by reliably forming a layer containing a large amount of Si-OH on the zeolite membrane surface, the polarity of the membrane surface is improved, and the separation performance of polar molecules can be improved. In addition, modifying the zeolite membrane surface with a Si compound can sometimes have the effect of sealing fine defects present on the membrane surface. Furthermore, the pore size of zeolite can be controlled by a silylation treatment, and this treatment can be suitably used as a method for improving the ammonia permeation selectivity.

[0205] The solvent used for the silylation treatment may be water or an organic solvent. The solution may also be acidic or basic, in which case the silylation reaction is catalyzed by the acid or base. There are no limitations on the silylating agent used, but alkoxysilanes are preferred. The treatment temperature is usually from room temperature to 150°C or less, and the treatment may be carried out for approximately 10 minutes to 30 hours. These treatment conditions may be appropriately set depending on the silylating agent and solvent used.

[0206] In the present invention, the content of nitrogen atoms contained in the surface of the zeolite membrane of the present invention can be controlled by, as described above, adjusting the Al atom / Si atom ratio of the zeolite by selecting a cation species containing nitrogen atoms in the zeolite contained in the zeolite membrane, adjusting the content of nitrogen atoms by adjusting the amount of ion exchange by ion exchange, using an organic template (structure-directing agent) containing nitrogen atoms when producing the zeolite membrane as needed and adjusting the amount of the organic template added or the heating temperature and heating time when the organic template is removed by baking, treating the zeolite membrane with nitrate, adjusting the number of times of water washing when washing the nitric acid-treated zeolite membrane with water, or by an appropriate combination of these methods. In the present invention, the content of Al atoms contained in the surface of the zeolite membrane of the present invention can be controlled by adjusting the Al atom / Si atom ratio in the zeolite contained in the zeolite membrane, treating the zeolite membrane with an aluminum salt, adjusting the number of times the aluminum salt-treated zeolite membrane is washed with water, or by appropriately combining these methods, as described above. In the present invention, the content of alkali metal elements contained in the surface of the zeolite membrane of the present invention can be controlled by, as described above, adjusting the Al atom / Si atom ratio in the zeolite contained in the zeolite membrane, adjusting the content of alkali metal elements by adjusting the amount of ion exchange by ion exchange, adjusting the number of times the zeolite membrane is washed with water, or by an appropriate combination of these methods.

[0207] The zeolite composite membrane thus produced has excellent properties and can be suitably used as a membrane separation means for separating ammonia from a mixed gas in the present invention. [Example]

[0208] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as it does not depart from the gist of the invention. Note that the values ​​of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present invention, and a preferred range may be defined by combining the upper or lower limit values ​​with the values ​​in the following examples or values ​​between the examples. In the following, "CHA-type silicate zeolite" will be simply referred to as "CHA-type zeolite," "RHO-type silicate zeolite" will be simply referred to as "RHO-type zeolite," and "MFI-type silicate zeolite" will be simply referred to as "MFI-type zeolite."

[0209] [Example A] [Separation performance measurement] The separation performance of the zeolite membrane composite was measured as follows.

[0210] (1) Ammonia separation test In the apparatus shown in Figure 1, an ammonia separation test was carried out as follows. In the apparatus shown in Figure 1, ammonia gas (NH3), nitrogen gas (N2), and hydrogen ( A mixed gas containing H2 was introduced into the pressure vessel and the zeolite membrane composite at a flow rate of 100 SCCM. The back pressure valve was used to adjust the pressure difference between the gas on the supply side and the gas that had permeated the membrane to a constant 0.3 MPa, and the exhaust gas discharged from pipe 10 was analyzed by a micro gas chromatograph to calculate the concentration and flow rate of the permeated gas.

[0211] In the ammonia separation test, the pressure vessel was purged with the sample gas to be used for drying and exhausting at temperatures above the measurement temperature in order to remove components such as moisture and air from the pressure vessel. After that, the sample gas temperature and the differential pressure between the supply gas side and the permeate gas side of the zeolite membrane composite were kept constant, and after the permeate gas flow rate had stabilized, the flow rate of the sample gas (permeate gas) that had permeated the zeolite membrane composite was measured, and the gas permeance [mol / (m 2 The pressure difference between the supply side and permeation side of the feed gas (differential pressure) was used as the pressure when calculating the permeance. In the case of a mixed gas, the partial pressure difference was used. Based on the measurement results, the ideal separation factor α' was calculated using the following formula (1). α'=(Q1 / Q2) / (P1 / P2) (1) [In equation (1), Q1 and Q2 represent the permeation amounts [mol (m 2 ·s) -1 ], and P1 and P2 represent the pressure difference [Pa] between the supply side and the permeation side of the high-permeability gas and the low-permeability gas, respectively. This indicates the ratio of the permeance of each gas, and therefore the permeance of each gas can be calculated and determined from the ratio.

[0212] [Production Example A1: Production of CHA-type zeolite membrane composite 1] CHA-type zeolite membrane composite 1 was produced by the following method.

[0213] (Raw material mixture for hydrothermal synthesis) First, a raw material mixture for hydrothermal synthesis was prepared as follows. To a mixture of 1.45 g of 1 mol / L NaOH aqueous solution, 5.78 g of 1 mol / L KOH aqueous solution, and 114.6 g of water, 0.19 g of aluminum hydroxide (Al2O3 - 53.5 mass% content, manufactured by Aldrich) was added and stirred to dissolve, forming a transparent solution. 2.43 g of a 25 mass% TMADAOH aqueous solution was added as an organic template, and 10.85 g of colloidal silica (Nissan Chemical Snowtec-40) was added and stirred for 2 hours to form a raw material mixture for hydrothermal synthesis. The composition (molar ratio) of this mixture was SiO2 / Al2O3 / NaO H / KOH / H2O / TMADAOH=1 / 0.018 / 0.02 / 0.08 / 100 / 0.04, SiO2 / Al2O3=58.

[0214] (Support) The porous support used was an alumina tube BN1 (outer diameter 6 mm, inner diameter 4 mm) manufactured by Noritake Co., Ltd., cut to a length of 80 mm, washed in an ultrasonic cleaner, and then dried.

[0215] (Seed crystal dispersion) The seed crystals were prepared by hydrothermal synthesis at 160°C for 2 days using a gel composition (molar ratio) of SiO2 / Al2O3 / NaOH / KOH / H2O / TMADAOH = 1 / 0.033 / 0.1 / 0.06 / 20 / 0.07, followed by filtration, washing with water, and drying to produce CHA-type zeolite seed crystals. The seed crystals had a particle size of approximately 0.3 to 3 μm. Next, the seed crystals were dispersed in water to a concentration of approximately 1 mass % to produce a seed crystal dispersion (CHA-type seed crystal dispersion).

[0216] (Production of membrane complex) The porous support was prepared, immersed in the seed crystal dispersion for 1 minute, and then dried at 100°C for 1 hour to attach the seed crystals to the support. The mass of the attached seed crystals was approximately 0.001 g.

[0217] The support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube (200 ml) containing the above-mentioned mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and the mixture was heated at 180°C for 72 hours in a static state under autogenous pressure. After the predetermined time had elapsed, the support-zeolite membrane composite was allowed to cool, then removed from the mixture of raw materials for hydrothermal synthesis, washed, and dried at 100°C for 3 hours. Next, the dried membrane composite was calcined in an electric furnace in air at 450°C for 10 hours and at 500°C for 5 hours, to obtain a CHA-type zeolite membrane composite 1 from which the template contained in the zeolite had been removed. The heating rate and cooling rate from room temperature to 450°C were both 0.5°C / min, and the heating rate and cooling rate from 450°C to 500°C were both 0.1°C / min. The mass of the CHA-type zeolite crystallized on the support, calculated from the difference between the mass of the membrane composite after calcination and the mass of the support, was approximately 0.279 to 0.289 g. The air permeability of the membrane composite after calcination was 2.4 to 2.9 cm 3 / min.

[0218] [Example A1] <Evaluation of membrane separation performance> As a pretreatment, a mixed gas of 50 vol% H2 / 50 vol% N2 was introduced as a feed gas between the pressure vessel and the CHA-type zeolite membrane composite 1 described in Production Example A1 at 200°C, and the pressure was maintained at approximately 0.4 MPa. The inside of the cylinder of the CHA-type zeolite membrane composite 1 was set to 0.098 MPa (atmospheric pressure), and the composite was dried for approximately 120 minutes. An ammonia separation test was conducted by the above-mentioned method using the CHA-type zeolite membrane composite 1 under conditions where the temperatures of the CHA-type zeolite membrane composite 1 were 100°C, 150°C, 200°C, and 250°C. The mixed gas used was a 12.0 vol% NH3 / 51.0 vol% N2 / 37.0 vol% H2 mixed gas. The ammonia concentration of the obtained permeable gas and the permeance ratios of ammonia / hydrogen (NH3 / H2) and ammonia / nitrogen (NH3 / N2) are shown in Table 3. In Table 3, the ammonia concentration of the permeable gas is rounded to one decimal place.

[0219] [Table 3]

[0220] [Example A2] Using the CHA-type zeolite membrane composite 1 described in Production Example A1, the temperature was set to 100°C, and the mixed gas was a mixed gas of 3.0 vol% NH3 / 24.0 vol% N2 / 73.0 vol% H2. Ammonia separation was evaluated in the same manner as in Example A1 except for the above. The ammonia gas concentration in the permeated gas was 4.1% by volume. The obtained results demonstrate that ammonia can be separated from mixed gases.

[0221] [Example A3] Using the CHA-type zeolite membrane composite 1 described in Production Example A1, the temperature was set to 100°C, and the mixed gas was a mixed gas of 2.0 vol% NH3 / 19.0 vol% N2 / 79.0 vol% H2. Ammonia separation was evaluated in the same manner as in Example A1 except for the above. As a result, the ammonia gas concentration in the permeated gas was 2.3% by volume. It can be seen that the separation of near is possible.

[0222] [Comparative Example A1] Ammonia separation was evaluated in the same manner as in Example A1, except that the temperature of the CHA-type zeolite membrane composite 1 described in Production Example A1 was 100°C and a mixed gas of 0.7 vol% NH3 / 80.0 vol% N2 / 19.3 vol% H2 was used. As a result, the ammonia gas concentration of the permeated gas was 0.8 vol%.

[0223] [Comparative example A2] Ammonia separation was evaluated in the same manner as in Example A1, except that the temperature of the CHA-type zeolite membrane composite 1 described in Production Example A1 was 100°C and a mixed gas of 0.8 vol% NH3 / 20.1 vol% N2 / 79.1 vol% H2 was used. As a result, the ammonia gas concentration of the permeated gas was 0.8 vol%.

[0224] As can be seen from Examples A1, A2, and A3 and Comparative Examples A1 and A2, even when the same zeolite membrane composite is used, if the ammonia gas concentration in the mixed gas is low, it is difficult to separate ammonia from the mixed gas. However, when the ammonia gas concentration in the mixed gas is 1.0 vol% or more, it is possible to efficiently separate ammonia.

[0225] [Reference example A1] Using the CHA-type zeolite membrane composite 1 prepared in Example A1, an annulus was prepared in the same manner as in Example A2, except that the temperature of the CHA-type zeolite membrane composite 1 was set to 100°C and a mixed gas of 12% by volume NH3 / 50% by volume N2 / 38% by volume H2 was passed through at a flow rate of 100 SCCM. As a result of evaluating the hydrogen separation, the hydrogen permeance was 7.0 × 10 -8 [mol / (m 2 ·s·Pa)], and the nitrogen permeance is 2.1×10 -8 [mol / (m 2 ·s·Pa)] , the ammonia permeance is 2.4 × 10 -7 [mol / (m 2 ·s·Pa)] In contrast, the hydrogen permeance when hydrogen gas is circulated alone is 1.6 x 10 -6 [mol / (m2 ·s·Pa)], and the permeance of nitrogen when nitrogen gas is circulated alone is 3.0×10 -7 [mol / (m 2 ·s·Pa), and these results show that when ammonia gas is contained in the feed gas, the permeance of both hydrogen and nitrogen drops significantly. From these results, it is thought that when the ammonia gas concentration in the mixed gas is above a certain amount, the ammonia in the feed gas is adsorbed by the zeolite, thereby inhibiting the permeation of hydrogen and nitrogen.

[0226] [Production Example A2: Production of CHA-type zeolite membrane composite 2] The CHA-type zeolite membrane composite 1 obtained in Production Example A1 after template removal was placed in a Teflon (registered trademark) inner tube (65 ml) containing 45 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0227] After a predetermined time has passed and the membrane is allowed to cool, the CHA-type zeolite membrane is taken out of the aqueous solution, washed with ion-exchanged water at 100°C for 1 hour three times, and then dried at 100°C for 4 hours or more to obtain the CHA-type zeolite membrane composite 2, NH4 + The CHA-type zeolite membrane composite was obtained.

[0228] [Example A4] <Evaluation of membrane separation performance> Ammonia separation evaluation was carried out in the same manner as in Example A1, except that the CHA-type zeolite membrane composite 2 described in Production Example A2 was used instead of the CHA-type zeolite membrane 1 described in Production Example A1. The ammonia concentration of the obtained permeable gas and the permeance ratios of ammonia / hydrogen and ammonia / nitrogen are shown in Table 4. In Table 4, the ammonia concentration of the permeable gas is rounded to one decimal place. From the results in Table 4, it can be seen that when the ammonia gas concentration in the mixed gas is equal to or greater than a specific amount, This indicates that ammonia can be separated efficiently. It also indicates that ammonia can be separated efficiently even under high temperature conditions.

[0229] [Table 4]

[0230] [Production Example A3: Production of RHO-type zeolite membrane composite 1] (Raw material mixture for hydrothermal synthesis) 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The crown ether-alkali aqueous solution was added dropwise to the CBV720 to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the resulting raw material mixture for hydrothermal synthesis was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.033 / 0.36 / 0.18 / 50 / 0.18.

[0231] (Support) The porous support was an alumina tube (outer diameter 6 mm, pore size 0.15 μm, manufactured by Noritake Co., Ltd.) cut into a length of 40 mm, washed with water, and then dried.

[0232] (Seed crystal dispersion) 23 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 6 g of NaOH (Kishida Chemical Industry Co., Ltd.), and 5 g of CsOH·H2O (Mitsuwa Chemical Industry Co., Ltd.) were dissolved in 84 g of water. The resulting solution was stirred at 80°C for 3 hours to obtain an aqueous crown ether-alkali solution.

[0233] Next, the crown ether-alkali aqueous solution was added dropwise to 30 g of FAU zeolite (SAR=30, Zeolyst CBV720), and 0.6 g of RHO zeolite seed crystals synthesized according to WO2015020014 was added. The mixture was stirred at room temperature for 2 hours to prepare a mixture. The molar ratio of this mixture was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.033 / 0.30 / 0.06 / 10 / 0.18.

[0234] This mixture was aged at room temperature for 24 hours, then placed in a pressure vessel and placed in a 150°C oven for 72 hours to carry out hydrothermal synthesis. After this hydrothermal synthesis reaction, the reaction solution was cooled and the resulting crystals were collected by filtration. The collected crystals were dried at 100°C for 12 hours to obtain RHO-type zeolite crystals.

[0235] The obtained RHO type zeolite was pulverized in a ball mill to produce a seed crystal dispersion. Specifically, 10 g of the above RHO type zeolite, 300 g of 3φ mm HD alumina balls (manufactured by Nikkato Corporation), and 90 g of water were placed in a 500 mL plastic bottle and pulverized in a ball mill for 6 hours to produce a 10 mass % RHO type zeolite dispersion. Water was added to this zeolite dispersion so that the RHO type zeolite was 3 mass %, and a seed crystal dispersion was obtained.

[0236] (Production of membrane complex) The seed crystal dispersion was dropped onto the support, and the seed crystals were attached to the support by a rubbing method.

[0237] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing a mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and it was heated at 150°C for 72 hours under autogenous pressure.

[0238] After a predetermined time had passed, the support-zeolite membrane composite was allowed to cool, then removed from the autoclave, washed, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 1.5 / (m 2Next, to remove the template, The membrane composite was calcined at 300°C to obtain an RHO-type zeolite membrane composite. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the calcined zeolite membrane composite and the weight of the support. 2 It was.

[0239] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon (registered trademark) inner tube (65 ml) containing 45 g of 3 M ammonium nitrate aqueous solution, and the autoclave was sealed and heated at 110°C for 1 hour in a static state under autogenous pressure.

[0240] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution, washed with water, and then dried at 100°C for 4 hours or more to remove NH4 + The RHO-type zeolite membrane composite was obtained.

[0241] The obtained NH4 + The RHO-type zeolite membrane composite was + To make this RHO type The zeolite membrane composite was fired in an electric furnace at 400°C for 2 hours. The heating and cooling rates up to 150°C were both 2.5°C / min, and the heating and cooling rates from 150°C to 400°C were both 0.5°C / min. + RHO-type zeolite membrane A complex was obtained.

[0242] [Example A5] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 1 described in Production Example A3, ammonia / hydrogen / nitrogen Ammonia separation tests from the mixed gas were carried out using the apparatus shown in Figure 1 as described above. As a pretreatment, a mixed gas of 50 vol% H2 / 50 vol% N2 was introduced as a feed gas between the pressure vessel and the RHO-type zeolite membrane composite 1 at 250°C, and the pressure was maintained at approximately 0.3 MPa. The inside of the cylinder of the RHO-type zeolite membrane composite 1 was set to 0.098 MPa (atmospheric pressure), and the composite was dried for approximately 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was injected for 100 seconds. The back pressure was set to 0.4 MPa. At this time, the pressure difference between the feed gas side and the permeate gas side of the RHO-type zeolite membrane composite 1 was 0.3 MPa.

[0243] The temperature of the RHO-type zeolite membrane composite 1 was changed to 150°C, 250°C, and 300°C, and the mixed gas was passed through, and the ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the obtained permeated gas were calculated. The results are shown in Table 5. In Table 5, the ammonia concentration of the permeated gas is a value rounded to one decimal place. The ammonia permeance at 250°C was 1.0 x 10 -8 [mol / (m 2 The results in Table 5 were as follows: From this, it can be seen that when the ammonia gas concentration in the mixed gas is above a specific level, ammonia can be separated efficiently. It was confirmed that ammonia was separated with high selectivity without any gaps or defects.

[0244] [Table 5]

[0245] [Production Example A4: Production of RHO zeolite membrane composite 2] The same procedure as in Production Example A3 was repeated except that the support with the attached seed crystals was immersed vertically in the Teflon (registered trademark) inner tube containing the raw material mixture for hydrothermal synthesis 2, the autoclave was sealed, and the mixture was heated at 150°C for 72 hours under autogenous pressure. + Type H + Without conversion to the type The outside is NH4 + The RHO-type zeolite membrane composite was obtained. Then, NH4 + The RHO-type zeolite membrane composite was placed in a Teflon (registered trademark) inner tube (65 ml) containing 45 g of 1 M aqueous aluminum nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0246] After a predetermined time has passed and the RHO-type zeolite membrane composite is left to cool, it is taken out of the aqueous solution, washed with water, and then dried at 100°C for 4 hours or more. + The RHO-type zeolite membrane composite was obtained and further placed in a Teflon (registered trademark) inner tube (65 ml) containing 45 g of 1 M aqueous sodium nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0247] After a predetermined time has passed and the membrane is allowed to cool, it is taken out of the aqueous solution, washed with water, and then dried at 100°C for 4 hours or more. + The ion-exchanged RHO-type zeolite membrane composite was obtained.

[0248] [Example A6] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 2 described in Production Example A4, ammonia / hydrogen / nitrogen Ammonia separation tests from the mixed gas were carried out using the above-mentioned method and the apparatus shown in Figure 1. As a pretreatment, a mixed gas of 50 vol% H2 / 50 vol% N2 was introduced as a supply gas 7 between the pressure vessel 2 and the zeolite membrane composite 1 at 250°C, and the pressure was maintained at approximately 0.3 MPa. The inside of the cylinder of the RHO-type zeolite membrane composite 2 was then dried at 0.098 MPa (atmospheric pressure) for approximately 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was injected for 100 seconds. The back pressure was set to 0.4 MPa. At this time, the pressure difference between the feed gas 7 side and the permeate gas 8 side of the zeolite membrane composite 2 was 0.3 MPa.

[0249] Thereafter, the temperature of the RHO-type zeolite membrane composite 2 was changed to 100°C and 250°C, and the permeance ratios of ammonia / hydrogen and ammonia / nitrogen in the obtained permeated gas were calculated. The results are shown in Table 6. In Table 6, the ammonia concentration in the permeated gas is rounded to the first decimal place. The results in Table 6 show that efficient ammonia separation is possible when the ammonia gas concentration in the mixed gas is a specific amount or more. It was also confirmed that the RHO-type zeolite membrane composite can separate ammonia with high selectivity even under high-temperature conditions. The ammonia permeance at 250°C was 2.0 x 10 -8 [mol / (m 2 ·s·Pa)].

[0250] [Table 6]

[0251] [Production Example A5: Production of RHO-type zeolite membrane composites 3 and 4] Seed crystals and a support were prepared in the same manner as in Production Example A4, except that water was added so that the RHO zeolite concentration became 1% by mass to obtain a seed crystal dispersion. The support, the inside of which was evacuated, was immersed in this seed crystal dispersion for 1 minute, and then, with the inside of the support still evacuated, the seed crystals were attached to the support by a rubbing method.

[0252] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner cylinder containing a mixture of raw materials for hydrothermal synthesis prepared by the same method as in Production Example A4, the autoclave was sealed, and the autoclave was heated at 160°C for 24 hours under autogenous pressure.

[0253] After a predetermined time had passed, the support-zeolite membrane composite was allowed to cool, then removed from the autoclave, washed, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 / (m 2 Next, to remove the template, The membrane composite was calcined to obtain an RHO-type zeolite membrane composite. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the calcined zeolite membrane composite and the weight of the support. 2 It was.

[0254] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon (registered trademark) inner tube (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0255] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0256] After that, the above treatment with 1M ammonium nitrate water was repeated five times, and then dried at 100°C for 4 hours or more to obtain the RHO-type zeolite membrane composite 3, NH4 + The RHO-type zeolite membrane composite was obtained.

[0257] The obtained NH4 + The RHO-type zeolite membrane composite 3 was placed in a Teflon (registered trademark) inner cylinder (65 ml) containing 45 g of 1 M aqueous aluminum nitrate solution, and the autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0258] After a predetermined time has passed and the membrane is allowed to cool, the RHO-type zeolite composite membrane 3 is taken out of the aqueous solution, washed with water, and then dried at 100°C for 4 hours or more. + The RHO-type zeolite membrane composite was obtained.

[0259] [Example A7] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 4 described in Production Example A5, an ammonia separation test was carried out from a mixed gas of ammonia (NH3) / hydrogen (H2) / nitrogen (N2) by the above-mentioned method. This was done using the device. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 4 at 250°C. The pressure inside the cylinder of the RHO zeolite membrane composite 4 was kept at about 0.3 MPa, and the pressure inside the cylinder was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. After that, a mixed gas of 12% by volume of NH3, 51% by volume of N2, and 37% by volume of H2 was passed through at 100 SCCM, and the back pressure was set to 0.4 MPa. At this time, the pressure difference between the feed gas side and the permeate gas side of the RHO zeolite membrane composite 4 was 0.3 MPa. Argon was supplied as a sweep gas from the feed gas 9 at 3.9 SCCM.

[0260] The temperature of the RHO-type zeolite membrane composite 4 was changed to 250°C, 300°C, and 325°C, and the mixed gas was passed through. The ammonia concentration of the obtained permeable gas and the ammonia / hydrogen and ammonia / nitrogen permeance ratios are shown in Table 7. In Table 7, the ammonia concentration of the permeable gas is rounded to one decimal place. These results also show that the Al-treated NH4 + It was confirmed that the RHO-type zeolite membrane was able to separate ammonia with high selectivity. In addition, the ammonia permeance at 250°C was 1.0 × 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 2.0 × 10 -8 [mol / (m 2 ·s·Pa). From the results in Table 7, it can be seen that efficient ammonia separation is possible when the ammonia gas concentration in the mixed gas is above a specific amount. It can also be seen that efficient ammonia separation is possible even under high temperature conditions.

[0261] [Table 7]

[0262] [Production Example A6: Production of RHO-type zeolite membrane composite 5] NH4 obtained by the same method as RHO-type zeolite membrane composite 3 in Production Example A5 + The RHO-type zeolite membrane composite was placed in a Teflon (registered trademark) inner tube (65 ml) containing 50 g of 1 M aqueous sodium nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0263] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour, then dried at 100°C for 4 hours or more to remove Na + The RHO-type zeolite membrane composite was then ion-exchanged into the Na + The RHO-type zeolite membrane was placed in a Teflon (registered trademark) inner cylinder (65 ml) containing 50 g of 1 M aqueous aluminum nitrate solution, and the autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0264] After a predetermined time has passed and the membrane is allowed to cool, it is taken out of the aqueous solution and washed with 100°C ion-exchanged water for 1 hour three times, and then dried at 100°C for 4 hours or more to obtain the RHO-type zeolite membrane composite 5, which is an Al-treated Na + The RHO-type zeolite membrane composite was obtained.

[0265] [Example A8] <Evaluation of membrane separation performance> Instead of the RHO-type zeolite membrane composite 4 described in Production Example A5, the RHO-type zeolite membrane composite 5 described in Production Example A6 was used, and argon was supplied as a sweep gas at 8.3 SCCM. A separation test of a mixed gas of 12.0 vol % NH3 / 51.0 vol % N2 / 37.0 vol % H2 was carried out in the same manner as in Example A7, except for the above. The ammonia concentration of the obtained permeation gas and the ammonia / hydrogen and ammonia / nitrogen permeance ratios are shown in Table 8. In Table 8, the ammonia concentration of the permeation gas is rounded to one decimal place. The ammonia permeance at 250°C was 4.4 x 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 1.1 × 10 -7 [mo l / (m 2 From these results, the ammonia gas concentration in the mixed gas It was also confirmed that ammonia could be separated with high selectivity even under high temperature conditions.

[0266] [Table 8]

[0267] [Example A9] The RHO-type zeolite membrane composite 5 described in Production Example A6 was mixed at a temperature of 250°C. The combined gas was a mixture of 2.0% by volume of NH3, 20.0% by volume of N2, and 78.0% by volume of H2. Ammonia separation was evaluated in the same manner as in Example A8, except for the above. The ammonia gas concentration in the permeable gas was 19.9% ​​by volume. The results show that ammonia can be separated from mixed gases.

[0268] [Example A10] The RHO-type zeolite membrane composite 5 described in Production Example A6 was mixed at a temperature of 250°C. The combined gas was a mixture of 3.0% by volume of NH3, 20.0% by volume of N2, and 77.0% by volume of H2. Ammonia separation was evaluated in the same manner as in Example A8, except for the above. The ammonia gas concentration in the permeable gas was 27.6% by volume. The results show that ammonia can be separated from mixed gases.

[0269] [Production Example A7: Production of RHO-type zeolite membrane composite 6] (mixture for hydrothermal synthesis) The following raw material mixture was prepared for hydrothermal synthesis. 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The crown ether-alkali aqueous solution was added dropwise to 0.2 g of 18-crown-6-ether (CBV720) and 0.2 g of aluminum hydroxide (53.5% by mass of Al2O3, manufactured by Aldrich) to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the resulting raw material mixture for hydrothermal synthesis was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.040 / 0.36 / 0.18 / 50 / 0.18.

[0270] (Production of membrane complex) The seed crystals and the support were prepared in the same manner as in Production Example A4, except that water was added so that the RHO-type zeolite concentration became 1% by mass to obtain a seed crystal dispersion. The support was evacuated to a vacuum. The support was immersed in this seed crystal dispersion for 1 minute, and then the seed crystals were attached to the support by a rubbing method while the inside of the support was evacuated to a vacuum.

[0271] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing a mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and it was heated at 160°C for 24 hours under autogenous pressure.

[0272] After a predetermined time had passed, the support-zeolite membrane composite was allowed to cool, then removed from the autoclave, washed, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 / (m 2 Next, to remove the template, The membrane composite was calcined to obtain an RHO-type zeolite membrane composite. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the calcined zeolite membrane composite and the weight of the support. 2 It was.

[0273] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon (registered trademark) inner tube (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0274] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0275] Next, the above treatment with 1M ammonium nitrate water was repeated five times, and then the mixture was dried at 100°C for more than 4 hours and then treated with NH4 + The RHO-type zeolite membrane composite was obtained.

[0276] NH4 + The RHO-type zeolite membrane composite was placed in a Teflon (registered trademark) inner tube (65 ml) containing 50 g of 1 M aqueous aluminum nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0277] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution, washed with water, and then dried at 100°C for 4 hours or more. + The RHO-type zeolite membrane composite was obtained.

[0278] [Example A11] <Evaluation of membrane separation performance> The same method as in Example A7 was used, except that the RHO-type zeolite membrane composite 6 described in Production Example A7 was used instead of the RHO-type zeolite membrane composite 4 described in Production Example A5. A separation test was carried out on a mixed gas of 51% by volume N2 / 37% by volume H2.

[0279] The ammonia concentration of the obtained permeable gas and the ammonia / hydrogen and ammonia / nitrogen permeance ratios are shown in Table 9. In Table 9, the ammonia concentration of the permeable gas is rounded to one decimal place. These results show that efficient ammonia separation is possible when the ammonia gas concentration in the mixed gas is above a specific amount. It was also confirmed that the RHO membrane manufactured with a gel composition with an increased Al content was able to separate ammonia with even higher selectivity under high temperature conditions. The ammonia permeance at 250°C was 1.3 x 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 2.8 × 10 -8 [mol / (m 2 ·s·Pa)].

[0280] [Table 9]

[0281] [Production Example A8: Production of MFI-type zeolite membrane composite 1] (Raw material mixture for hydrothermal synthesis) A raw material mixture for hydrothermal synthesis was prepared by the following method. 0.15 g of sodium aluminate (containing 62.2% by mass of Al2O3) was added to a mixture of 13.65 g of a 50 wt% NaOH aqueous solution and 101 g of water, and the mixture was stirred at room temperature for 10 minutes. 32.3 g of colloidal silica (Nissan Chemical Snowtec-40) was added to the mixture, and the mixture was stirred for 5 minutes. The mixture was stirred at 0°C for 5 hours to prepare a raw material mixture for hydrothermal reaction. The composition (molar ratio) of this raw material mixture for reaction was SiO2 / Al2O3 / NaOH / H2O = 3.05 / 0.013 / 0.193 / 100, and SiO2 / Al2O3 = 239.

[0282] (Seed crystal dispersion) ZSM5 zeolite (HSZ-800 series 822H0A manufactured by Tosoh Corporation) was ground in a mortar and prepared, and seed crystals were dispersed in the ground zeolite so that the concentration of the seed crystals was about 0.4 mass % to prepare a seed crystal dispersion. (Production of membrane complex) A porous support that had been treated in the same manner as in Production Example A1 was immersed in the above-mentioned seed crystal dispersion for 1 minute, dried at 70°C for 1 hour, immersed again in the seed crystal dispersion for 1 minute, and then dried at 70°C for 1 hour. The seed crystals were attached to the support. The mass of the attached seed crystals was approximately 0.0016 g. A porous support having seed crystals attached thereto was also prepared by the method described above.

[0283] The three supports with the seed crystals attached were each immersed vertically in a Teflon (registered trademark) inner tube (200 ml) containing the above-mentioned mixture of raw materials for hydrothermal synthesis, and the autoclave was sealed and heated at 180°C for 30 hours in a static state under autogenous pressure. After a predetermined time had passed and the mixture was allowed to cool, the support-zeolite membrane composite was removed from the reaction mixture, washed, and then dried at 100°C for 3 hours to obtain MFI zeolite membrane composite 1. The mass of the MFI zeolite crystallized on the support was 0.26 to 0.28 g. The air permeability of the membrane composite after calcination was 0.0 to 0.1 cm 3 / min.

[0284] [Example A12] <Evaluation of membrane separation performance> Ammonia separation evaluation was carried out in the same manner as in Example A1, except that the MFI-type zeolite membrane composite 1 described in Production Example A8 was used instead of the CHA-type zeolite membrane composite 1 described in Production Example A1. The ammonia concentration of the obtained permeable gas and the ammonia / hydrogen and ammonia / nitrogen permeance ratios are shown in Table 10. In Table 10, the ammonia concentration of the permeable gas is rounded to one decimal place. The ammonia permeance at 250°C was 7.5 x 10 -8 [mol / (m 2 These results indicate that the amount of argon in the mixed gas is It can be seen that efficient ammonia separation is possible when the ammonia gas concentration is above a specific level. It was also confirmed that ammonia permeates the membrane with high selectivity even when the temperature is changed from 150°C to 250°C. Therefore, it was confirmed that ammonia can be separated with high selectivity even under high temperature conditions.

[0285] [Table 10]

[0286] [Example A13] Ammonia separation was evaluated in the same manner as in Example A12, except that the temperature was 250°C and the mixed gas was a mixed gas of 2.0 vol% NH3 / 20.0 vol% N2 / 78.0 vol% H2. As a result, the ammonia gas concentration in the permeated gas was 7.0% by volume. The results show that it is possible to separate ammonia from a mixed gas.

[0287] [Example A14] Ammonia separation was evaluated in the same manner as in Example A12, except that the temperature was 250°C and the mixed gas was 3.0 vol% NH3 / 20.0 vol% N2 / 77.0 vol% H2. As a result, the ammonia gas concentration in the permeated gas was 10.7% by volume. The results show that it is possible to separate ammonia from mixed gases.

[0288] [Reference example A2] The MFI type zeolite membrane composite 1 prepared in Production Example A8 was used, and the procedure was the same as in Example A12, except that the temperature of the MFI type zeolite membrane composite 1 was set to 250°C and a mixed gas of 12% by volume NH3 / 50% by volume N2 / 38% by volume H2 was passed through at a flow rate of 100 SCCM. As a result of evaluating ammonia separation, the hydrogen permeance was 1.6×10 -8 [mol / (m 2 ·s·Pa)], and the nitrogen permeance is 3.3 × 10 -9 [mol / (m 2·s·Pa)], and the ammonia permeance is 7.5 × 10 -8 [mol / (m 2 ·s·Pa)] In contrast, the hydrogen permeance when hydrogen gas is circulated alone is 4.7 x 10 -7 [mol / (m 2 ·s·Pa)], and the permeance of nitrogen when nitrogen gas is circulated alone is 3.0×10 -7 [mol / (m 2 ·s·Pa), and these results show that when ammonia gas is contained in the feed gas, the permeance of both hydrogen and nitrogen drops significantly. From these results, it is thought that when the ammonia gas concentration in the mixed gas is above a certain amount, the ammonia in the feed gas is adsorbed by the zeolite, thereby inhibiting the permeation of hydrogen and nitrogen.

[0289] Table 11 shows the data for Examples A1 to A3, A8 to 10, A12 to 14, and Comparative Examples A1 to A2. Note that Examples A1 to A3 and Comparative Examples A1 and A2 show evaluation results at 100°C, and Examples A8 to 10 and A12 to 14 show evaluation results at 250°C. These results also show that when the ammonia gas concentration in the mixed gas is a specific amount or more, the concentration of ammonia relative to hydrogen and nitrogen increases.

[0290] [Table 11]

[0291] [Example B] [Measurement of physical properties and separation performance] In the following, the physical properties and separation performance of the zeolite or zeolite membrane composite were measured as follows.

[0292] (1) X-ray diffraction (XRD) measurement The XRD measurement was carried out under the following conditions. Device name: Bruker New D8 ADVANCE Optical system: Concentrated optical system Optical system specifications: Entrance side: sealed X-ray tube (CuKα) Soller Slit (2.5°) Divergence Slit (Variable Slit) Sample stage: XYZ stage Light receiving side: Semiconductor array detector (Lynx Eye 1D mode) Ni-filter Soller Slit (2.5°) Goniometer radius: 280 mm Measurement conditions: X-ray output (CuKα): 40 kV, 40 mA Scan axis: θ / 2θ Scanning range (2θ): 5.0-70.0° Measurement mode: Continuous Reading width: 0.01° Counting time: 57.0 sec (0.3 sec x 190 ch) Automatic variable slit (Automatic-DS): 1 mm (irradiation width) The measurement data was subjected to variable-to-fixed slit correction.

[0293] The X-rays were irradiated in a direction perpendicular to the axial direction of the cylindrical tube. In order to minimize noise, the X-rays were irradiated parallel to the surface of the cylindrical tube-shaped membrane composite placed on the sample stage. Of the two lines that contact the flat surface, the beam was made to mainly hit the other line that was above the surface of the sample stage, rather than the line that contacted the surface of the sample stage. In addition, the irradiation width was fixed at 1 mm using an automatic variable slit, and measurements were taken. The XRD pattern was obtained by performing variable slit to fixed slit conversion using the XRD analysis software JADE+9.4 (English version) from Materials Data, Inc.

[0294] (2)XPS measurement (Na, Si, Al, N) The XPS measurement was carried out under the following conditions. Model name: ULVAC-PHI Inc. Quantum2000 X-ray source during measurement: Monochromated Al-Kα, output 16kV-34W (X-ray generating area 170umφ) Charge neutralization: electron gun 5μA, ion gun 3V Spectroscopic system: Pass energy Wide spectrum: 187.70 eV Narrow spectrum (N1s, O1s, Na1s, Al2p, Si2p, Cs3d5)): 58.70eV *When Cs was detected, the peak positions of Cs3d5 and Al2p overlapped, so the Al2s peak was used instead of Al2p. (Using a sample that did not contain Cs, it was confirmed that there was no difference in the analytical values ​​of the surface composition whether Al2p or Al2s was used.) Measurement area: 300μm square Take-off angle: 45° (from the surface) Energy correction: Si2p=103.4eV

[0295] Quantitation was performed using sensitivity correction factors provided by ULVAC-PHI, Inc., and the background for quantitative calculations was determined by the Shirley method.

[0296] (3) Air permeability One end of the zeolite membrane composite was sealed, and the other end was connected to a 5 kPa vacuum line in a sealed state. The air flow rate was measured with a mass flow meter installed between the vacuum line and the zeolite membrane composite, and the air permeation rate [L / (m 2 ·h)]. The mass flow meter was KOF LOC 8300, for N2 gas, maximum flow rate 500 ml / min (20°C, 1 atmosphere equivalent) When the mass flow meter reading on the KOFLOC 8300 was 10 ml / min (20°C, 1 atmosphere equivalent) or less, measurements were taken using the Lintec MM-2100M for air gas, with a maximum flow rate of 20 ml / min (0°C, 1 atmosphere equivalent).

[0297] In Fig. 1, a cylindrical zeolite membrane composite 1 is placed in a thermostatic chamber (not shown) while being housed in a stainless steel pressure vessel 2. The thermostatic chamber is equipped with a temperature control device so that the temperature of the supplied gas can be adjusted.

[0298] One end of the cylindrical zeolite membrane composite 1 is sealed with an end pin 3 with a T-shaped cross section. The other end of the zeolite membrane composite 1 is connected to an exhaust pipe 10 for a permeate gas 8 via a connection 4, and the pipe 10 extends to the outside of the pressure vessel 2. Furthermore, a pressure gauge 5 for measuring the supply pressure of the supply gas 7 from the supply pipe 12 and a back pressure valve 6 for adjusting the supply pressure are connected to a gas exhaust pipe 13 from the pressure vessel 2. Each connection is airtight.

[0299] In the apparatus shown in Figure 1, when a single-component gas permeation test was performed, a supply gas (sample gas) 7 was supplied at a constant flow rate between the pressure vessel 2 and the zeolite membrane composite 1, the pressure on the supply side was kept constant by the back-pressure valve 6, and the permeated gas 8 that had permeated the zeolite membrane composite 1 was measured by a flow meter connected to the piping 10.

[0300] One end of the cylindrical zeolite membrane composite 1 is sealed with an end pin 3 with a T-shaped cross section. The other end of the zeolite membrane composite 1 is connected to an exhaust pipe 11 for a permeation gas 8 via a connection part 4, and the pipe 11 extends to the outside of the pressure vessel 2. A pressure gauge 5 for measuring the pressure on the supply side of the supply gas 7 is connected to a supply pipe 12 for a supply gas (sample gas) 7 to the pressure vessel 2. Each connection is airtight.

[0301] (4) Ammonia separation test An ammonia separation test was carried out as follows using the apparatus shown schematically in Figure 1. In the apparatus shown in Figure 1, a mixed gas containing ammonia, nitrogen, and hydrogen was supplied as the feed gas between the pressure vessel and the zeolite membrane composite at a flow rate of 100 SCCM, and the pressure difference between the feed gas and the gas that had permeated through the membrane was adjusted to a constant 0.3 MPa using a back-pressure valve. Helium, whose flow rate was controlled by a mass flow controller, was mixed as a standard substance into the exhaust gas discharged from pipe 10, and the mixture was analyzed using a micro gas chromatograph to calculate the concentration and flow rate of the permeated gas.

[0302] In the ammonia separation test, the pressure vessel was purged with the sample gas to be used for drying and exhausting at temperatures above the measurement temperature in order to remove components such as moisture and air from the pressure vessel. After that, the sample gas temperature and the differential pressure between the supply gas side and the permeate gas side of the zeolite membrane composite were kept constant, and after the permeate gas flow rate had stabilized, the flow rate of the sample gas (permeate gas) that had permeated the zeolite membrane composite was measured, and the gas permeance [mol / (m 2 s Pa) was calculated. The pressure used to calculate the fluence was the pressure difference between the supply side and the permeation side of the feed gas (differential pressure). In the case of a mixed gas, the partial pressure difference was used. Based on the measurement results, the ideal separation factor α' was calculated using the following formula (1). α'=(Q1 / Q2) / (P1 / P2) (1) [In equation (1), Q1 and Q2 represent the permeation amounts [mol (m 2 ·s) -1 ], and P1 and P2 are highly permeable The pressure difference [Pa] between the feed side and the permeation side for the low permeability gas and the low permeability gas is shown.] This indicates the ratio of the permeance of each gas, and therefore the permeance of each gas can be calculated and determined from the ratio.

[0303] [Production Example B1: Production of RHO-type zeolite membrane composites 1 and 2] RHO type zeolite membrane composites 1 and 2 were produced by the following method. Prior to the production of the RHO type zeolite membrane composites 1 and 2, a raw material mixture for hydrothermal synthesis 1, a support, and a seed crystal dispersion 1 were prepared as described below.

[0304] (Raw material mixture 1 for hydrothermal synthesis) 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The above crown ether-alkali aqueous solution was added dropwise to CBV720 to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the obtained raw material mixture for hydrothermal synthesis 1 was SiO2 / A l2O3 / NaOH / CsOH / H2O / 18-crown-6-ether=1 / 0.033 / 0.36 / 0.18 / 50 / 0.18.

[0305] (Support) The porous support was an alumina tube (outer diameter 6 mm, inner diameter 4 mm, pore size 0.15 μm, manufactured by Noritake Co., Ltd.) cut to a length of 80 mm, washed with water, and then dried.

[0306] (Seed crystal dispersion 1) 23 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 6 g of NaOH (Kishida Chemical Industry Co., Ltd.), and 5 g of CsOH·H2O (Mitsuwa Chemical Industry Co., Ltd.) were dissolved in 84 g of water. The resulting solution was stirred at 80°C for 3 hours to obtain an aqueous crown ether-alkali solution.

[0307] Next, the crown ether-alkali aqueous solution was added dropwise to 30 g of FAU zeolite (SAR=30, Zeolyst CBV720), and 0.6 g of RHO zeolite seed crystals synthesized according to WO2015020014 was added. The mixture was stirred at room temperature for 2 hours to prepare a mixture. The molar ratio of this mixture was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.033 / 0.30 / 0.06 / 10 / 0.18.

[0308] This mixture was aged at room temperature for 24 hours, then placed in a pressure vessel and placed in a 150°C oven for 72 hours to carry out hydrothermal synthesis. After this hydrothermal synthesis reaction, the reaction solution was cooled and the resulting crystals were collected by filtration. The collected crystals were dried at 100°C for 12 hours to obtain RHO-type zeolite crystals.

[0309] The obtained RHO type zeolite was pulverized in a ball mill to produce a seed crystal dispersion. Specifically, 10 g of the above RHO type zeolite, 300 g of 3φ mm HD alumina balls (manufactured by Nikkato Corporation), and 90 g of water were placed in a 500 mL plastic bottle and pulverized in a ball mill for 6 hours to produce a 10 mass % RHO type zeolite dispersion. Water was added to this zeolite dispersion so that the RHO type zeolite was 1 mass %, and seed crystal dispersion 1 was obtained.

[0310] (Production of Zeolite Membrane Composite) Next, a support with the inside evacuated was immersed in this seed crystal dispersion liquid 1 for 1 minute, and then the support With the inside of the container evacuated to a vacuum, the seed crystal was attached to the support by a rubbing method.

[0311] The support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner cylinder containing a mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and heated at 160°C for 24 hours under autogenous pressure.

[0312] After a predetermined time had passed and the composite support-zeolite membrane was allowed to cool, it was removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, remove the template. To obtain an RHO-type zeolite membrane composite, the obtained membrane composite was calcined. This RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and cooled from 100°C to room temperature in 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated as 62 g / m, based on the difference between the weight of the zeolite membrane composite after calcination and the weight of the support. 2 was .

[0313] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0314] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0315] After that, the above treatment with 1M ammonium nitrate water was repeated five times, and then the mixture was heated at 100°C. The RHO-type zeolite membrane composite 1 was dried for more than 4 hours with NH4 + The RHO-type zeolite membrane composite was obtained.

[0316] The obtained NH4 + The RHO-type zeolite membrane composite 1 was placed in a Teflon container (registered trademark) inner cylinder (65 ml) containing 45 g of 1 M aluminum nitrate aqueous solution, and the autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0317] After a predetermined time has elapsed, the mixture is left to cool, and then the above-treated NH4 +The RHO-type zeolite membrane composite 1 was taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more. The RHO-type zeolite membrane composite 2, which is an Al-treated NH4 + The zeolite membrane of the zeolite membrane composite was measured by XPS, and the nitrogen atom / Al atom molar ratio of the zeolite membrane was found to be 0.42 and the Si atom / Al atom molar ratio was found to be 3.01.

[0318] [Example B1] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 2 described in Production Example B1, ammonia gas (NH Ammonia separation tests from a mixed gas of ethanol (H2) / hydrogen gas (H2) / nitrogen gas (N2) were carried out using the apparatus shown in Figure 1 according to the method described above, specifically as follows. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 2 at 250°C. The pressure inside the cylinder of the RHO zeolite membrane composite 2 was kept at about 0.3 MPa, and the pressure inside the cylinder was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was used as the feed gas. The gas was passed through at 100 SCCM, and the back pressure was set to 0.4 MPa. At this time, the pressure difference between the feed gas side and the permeate gas side of the RHO zeolite membrane composite 2 was 0.3 MPa. In addition, argon was supplied as a sweep gas from the feed gas 9 at 3.9 SCCM.

[0319] The ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the permeated gas obtained when the mixed gas was passed through the RHO-type zeolite membrane composite 2 at temperatures of 250°C, 300°C, and 325°C are shown in Table 12. From the results in Table 12, it can be seen that the nitrogen atom / Al atom molar ratio of 0.42 in the NH4 +It can be seen that the use of this RHO-type zeolite membrane enables efficient separation of ammonia. In addition, under high temperature conditions, the nitrogen atom / Al atom molar ratio was 0.42 as measured by XPS. + It was confirmed that the RHO-type zeolite membrane can separate ammonia with high selectivity. The ammonia permeance at 250°C is 1.0 × 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 2.0 × 10 -8 [mol / (m 2 ·s·Pa)].

[0320] [Table 12]

[0321] [Production Example B2: Production of RHO-type zeolite membrane composite 3] The RHO-type zeolite membrane composite 3 was produced by the following method. The same support as in B1 was used, and the same seed crystal dispersion as in Seed Crystal Dispersion 1 in Production Example B1 was used.

[0322] (Hydrothermal synthesis mixture 2) The following was prepared as a hydrothermal synthesis raw material mixture 2. 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The crown ether-alkali aqueous solution was added dropwise to 0.2 g of 18-crown-6-ether (CBV720) and 0.2 g of aluminum hydroxide (53.5% by mass of Al2O3, manufactured by Aldrich) to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the resulting raw material mixture for hydrothermal synthesis 2 was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.040 / 0.36 / 0.18 / 50 / 0.18.

[0323] (Production of membrane complex) The support, the inside of which was evacuated, was immersed in the seed crystal dispersion liquid 1 for 1 minute, and then the inside of the support was evacuated. The seed crystal was attached to the support by a rubbing method while the support was pulled to the center.

[0324] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing the raw material mixture 2 for hydrothermal synthesis, the autoclave was sealed, and it was heated at 160°C for 24 hours under autogenous pressure.

[0325] After a predetermined time had passed and the composite support-zeolite membrane was allowed to cool, it was removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, remove the template. To obtain an RHO-type zeolite membrane composite, the obtained membrane composite was calcined. This RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and cooled from 100°C to room temperature in 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the zeolite membrane composite after calcination and the weight of the support, and was found to be 56 g / m. 2 was .

[0326] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0327] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0328] Next, the above treatment with 1M ammonium nitrate water was repeated five times, and then the mixture was dried at 100°C for more than 4 hours and then treated with NH4 + The RHO-type zeolite membrane composite was obtained.

[0329] NH4 + The RHO-type zeolite membrane composite was placed in a 65 ml Teflon container (registered trademark) containing 50 g of a 1 M aqueous aluminum nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0330] After a predetermined time has elapsed, the mixture is left to cool, and then the above-treated NH4 + The RHO-type zeolite membrane composite was taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more. This gave RHO-type zeolite membrane composite 3, which is the Al-treated NH4 + RHO-type zeolite membrane composite The nitrogen atom / Al atom molar ratio of the zeolite membrane measured by XPS was 0.76, and the Si atom / Al atom molar ratio was 6.65.

[0331] [Example B2] <Evaluation of membrane separation performance> A separation test of a mixed gas of 12 vol% NH3 / 51 vol% N2 / 37 vol% H2 was carried out under conditions of 250°C and 325°C in the same manner as in Example B1, except that the RHO-type zeolite membrane composite 3 described in Production Example B2 was used instead of the RHO-type zeolite membrane composite 2 described in Production Example B1, and the supply amount of argon as a sweep gas was changed to 8.3 SCCM. .

[0332] The ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the obtained permeated gas are shown in Table 13. From the results in Table 13, it can be seen that the nitrogen atom / Al atom molar ratio was 0.76 by XPS measurement. + It can be seen that efficient ammonia separation is possible by using an RHO-type zeolite membrane of this type. Furthermore, it was confirmed that an RHO membrane manufactured with a gel composition with an increased Al atom content can separate ammonia with even higher selectivity under high temperature conditions. The ammonia permeance at 250°C was 1.3 x 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 2.8 × 10 -8 [mol / (m 2 ·s·Pa)].

[0333] [Table 13]

[0334] [Production Example B3: Production of RHO-type zeolite membrane composite 4] An RHO-type zeolite membrane composite 4 was produced by the following method. The raw material mixture for hydrothermal synthesis and the support used were the same as the raw material mixture for hydrothermal synthesis 1 and the support used in Production Example B1, respectively.

[0335] (Seed crystal dispersion 2) Seed crystal dispersion 2 was produced in the same manner as seed crystal dispersion 1 in Production Example B1, except that a 10 mass% RHO type zeolite dispersion was prepared and then water was added so that the RHO type zeolite concentration was 3 mass%.

[0336] (Production of membrane complex) The seed crystal dispersion 2 was dropped onto the support, and the seed crystals were attached to the support by a rubbing method.

[0337] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing the raw material mixture for hydrothermal synthesis 1, the autoclave was sealed, and the mixture was heated at 150°C for 72 hours under autogenous pressure.

[0338] After a predetermined time had passed and the composite support-zeolite membrane was allowed to cool, it was removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 1.5 L / (m 2 Next, remove the template. To obtain the RHO-type zeolite membrane composite, the obtained membrane composite was calcined. The O-type zeolite membrane composite was heated from room temperature to 150°C in 2 hours, heated from 150°C to 400°C in 20 hours, and calcined at 400°C for 5 hours. After that, the temperature was lowered to 150°C in 20 hours, and then lowered from 150°C to room temperature in 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the zeolite membrane composite after calcination and the weight of the support, and was found to be 78 g / m. 2 was .

[0339] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 45 g of 3 M ammonium nitrate aqueous solution, and the autoclave was sealed and heated at 110°C for 1 hour in a static state under autogenous pressure.

[0340] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more with NH4 + The RHO-type zeolite membrane composite was obtained.

[0341] The obtained NH4 + The RHO-type zeolite membrane composite was + To make this RHO type The zeolite membrane composite was fired in an electric furnace at 400°C for 2 hours. The heating and cooling rates up to 150°C were both 2.5°C / min, and the heating and cooling rates from 150°C to 400°C were both 0.5°C / min. + RHO-type zeolite membrane The nitrogen atom / Al atom molar ratio of the zeolite membrane was measured by XPS to be 0.23, and the Si atom / Al atom molar ratio was 2.92.

[0342] [Example B3] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 4 described in Production Example B3, a test for separating ammonia from a mixed gas of ammonia / hydrogen / nitrogen was carried out using the apparatus shown in FIG. As a pretreatment, a mixed gas of 50% by volume H2 / 50% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO-type zeolite membrane composite 4 at 250°C, the pressure was kept at approximately 0.3 MPa, and the inside of the cylinder of the RHO-type zeolite membrane composite 4 was set to 0.098 MPa (atmospheric pressure), and the composite was dried for approximately 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was injected for 100 seconds. The pressure was set to 0.4 MPa. The differential pressure between the supply gas side and the permeate gas side of the RHO-type zeolite membrane composite 4 was 0.3 MPa. Argon was supplied as a sweep gas from the supply gas 9 at a rate of 2.4 SCCM.

[0343] The ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the permeated gas obtained when the mixed gas was passed through the RHO-type zeolite membrane composite 4 at temperatures of 150°C, 250°C, and 300°C were calculated, and the results are shown in Table 14. From these results, it can be seen that the NH4 + Compared with the separation results of the RHO-type zeolite membrane composite, the nitrogen atom / Al atom molar ratio of this H was 0.23 as measured by XPS. + RHO type Zeo Although the ammonia separation performance of the light membrane composite was slightly reduced, it was confirmed that the separation performance was still high. The ammonia permeance at 250°C was 1.0 × 10 -8 [mol / (m 2 ·s·Pa)].

[0344] [Table 14]

[0345] [Production Example B4: Production of RHO-type zeolite membrane composite 5] An RHO-type zeolite membrane composite 5 was produced by the following method. The raw material mixture for hydrothermal synthesis used was the same as the raw material mixture for hydrothermal synthesis 2 in Production Example B2, and the support and seed crystal dispersion used were the same as the support and seed crystal dispersion 1 in Production Example B1, respectively.

[0346] (Production of membrane complex) The support, the inside of which was evacuated, was immersed in the seed crystal dispersion liquid 1 for 1 minute, and then the inside of the support was evacuated. The seed crystal was attached to the support by a rubbing method while the support was pulled to the center.

[0347] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing the raw material mixture 2 for hydrothermal synthesis, the autoclave was sealed, and it was heated at 160°C for 24 hours under autogenous pressure.

[0348] After a predetermined time had passed and the composite support-zeolite membrane was allowed to cool, it was removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, remove the template. To achieve this, the obtained membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, baked at 300°C for 5 hours, cooled to 100°C in 20 hours, and then cooled from 100°C to room temperature in 2 hours and baked again. +Thus, an RHO-type zeolite membrane composite 5 was obtained. This RHO-type zeolite membrane composite 5 was prepared using no raw materials containing nitrogen atoms, and the nitrogen atom content was less than 0.01 in terms of the molar ratio of nitrogen atoms to Al atoms. The weight of the RHO-type zeolite crystallized on the support was 58 g / m, calculated from the difference between the weight of the zeolite membrane composite after firing and the weight of the support. 2 It was.

[0349] [Reference example B1] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 5 described in Production Example B4, a test for separating ammonia from a mixed gas of ammonia / hydrogen / nitrogen was carried out by the method described above using the apparatus shown in FIG. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 5 at 250°C. The pressure inside the cylinder of the RHO zeolite membrane composite 2 was kept at about 0.3 MPa, and the pressure inside the cylinder was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was injected for 100 seconds. The back pressure was set to 0.4 MPa. At this time, the differential pressure between the feed gas side and the permeate gas side of the RHO zeolite membrane composite 5 was 0.3 MPa. Argon was supplied as a sweep gas from the feed gas 9 at 3.9 SCCM.

[0350] The ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the permeated gas obtained when the mixed gas was passed through the RHO-type zeolite membrane composite 5 at temperatures of 250°C and 300°C are shown in Table 15. The ammonia permeance at 250°C was 1.9 × 10 -8 [mol / (m 2 ·s·Pa)], ammonia permeability at 300°C Ens is 2.0 x 10 -8 [mol / (m 2 From the results in Table 15, This Cs essentially contains no nitrogen atoms + The RHO-type zeolite membrane was analyzed by X-ray photoelectron spectroscopy. It was revealed that the ammonia separation ability was lower than that of any of the RHO-type zeolite membranes of Examples B1 to B3, which contain a specific amount of nitrogen atoms relative to Al atoms determined by X-ray photoelectron spectroscopy, and that the separation performance tended to decrease significantly when the temperature was further increased. Therefore, from these results, it was revealed that when a zeolite membrane containing a specific amount of nitrogen atoms relative to Al atoms determined by X-ray photoelectron spectroscopy is used, the affinity between the membrane and ammonia is increased, allowing ammonia to permeate preferentially, and the membrane can have high stability against temperature.

[0351] [Table 15]

[0352] [Example C] [Measurement of physical properties and separation performance] In the following, the physical properties and separation performance of the zeolite or zeolite membrane composite were measured in the same manner as in Example B.

[0353] [Production Example C1: Production of RHO-type zeolite membrane composites 1 and 2] RHO type zeolite membrane composites 1 and 2 were produced by the following method. Prior to the production of the RHO type zeolite membrane composites 1 and 2, a raw material mixture for hydrothermal synthesis 1, a support, and a seed crystal dispersion 1 were prepared as described below.

[0354] (Raw material mixture 1 for hydrothermal synthesis) 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The above crown ether-alkali aqueous solution was added dropwise to CBV720 to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the obtained raw material mixture for hydrothermal synthesis 1 was SiO2 / A l2O3 / NaOH / CsOH / H2O / 18-crown-6-ether=1 / 0.033 / 0.36 / 0.18 / 50 / 0.18.

[0355] (Support) The porous support was an alumina tube (outer diameter 6 mm, inner diameter 4 mm, pore size 0.15 μm, manufactured by Noritake Co., Ltd.) cut to a length of 80 mm, washed with water, and then dried.

[0356] (Seed crystal dispersion 1) 23 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 6 g of NaOH (Kishida Chemical Industry Co., Ltd.), and 5 g of CsOH·H2O (Mitsuwa Chemical Industry Co., Ltd.) were dissolved in 84 g of water. The resulting solution was stirred at 80°C for 3 hours to obtain an aqueous crown ether-alkali solution.

[0357] Next, the crown ether-alkali aqueous solution was added dropwise to 30 g of FAU zeolite (SAR=30, Zeolyst CBV720), and 0.6 g of RHO zeolite seed crystals synthesized according to WO2015020014 was added. The mixture was stirred at room temperature for 2 hours to prepare a mixture. The molar ratio of this mixture was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.033 / 0.30 / 0.06 / 10 / 0.18.

[0358] After aging this mixture at room temperature for 24 hours, it was placed in a pressure vessel and placed in an oven at 150°C for 72 hours to carry out hydrothermal synthesis. After this hydrothermal synthesis reaction, the reaction solution was cooled and filtered. The resulting crystals were collected and dried at 100°C for 12 hours to obtain RHO-type zeolite crystals.

[0359] The obtained RHO type zeolite was pulverized in a ball mill to produce a seed crystal dispersion. Specifically, 10 g of the above RHO type zeolite, 300 g of 3φ mm HD alumina balls (manufactured by Nikkato Corporation), and 90 g of water were placed in a 500 mL plastic bottle and pulverized in a ball mill for 6 hours to produce a 10 mass % RHO type zeolite dispersion. Water was added to this zeolite dispersion so that the RHO type zeolite was 1 mass %, and seed crystal dispersion 1 was obtained.

[0360] (Production of Zeolite Membrane Composite) Next, a support with the inside evacuated was immersed in this seed crystal dispersion liquid 1 for 1 minute, and then the support With the inside of the container evacuated to a vacuum, the seed crystal was attached to the support by a rubbing method.

[0361] The support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner cylinder containing a mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and heated at 160°C for 24 hours under autogenous pressure.

[0362] After a predetermined time had passed, the support-zeolite membrane composite was allowed to cool, then removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, the template was removed. To obtain an RHO-type zeolite membrane composite, the obtained membrane composite was calcined. This RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and cooled from 100°C to room temperature in 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated as 62 g / m, based on the difference between the weight of the zeolite membrane composite after calcination and the weight of the support. 2 It was.

[0363] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0364] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0365] After that, the above treatment with 1M ammonium nitrate water was repeated five times, and then dried at 100°C for 4 hours or more to obtain the RHO-type zeolite membrane composite 1, NH4 + The RHO-type zeolite membrane composite was obtained.

[0366] The obtained NH4 + The RHO-type zeolite membrane composite 1 was placed in a Teflon container (registered trademark) inner cylinder (65 ml) containing 45 g of 1 M aluminum nitrate aqueous solution, and the autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0367] After a predetermined time has elapsed, the mixture is left to cool, and then the above-treated NH4 + The RHO-type zeolite membrane composite 1 was taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more. The RHO-type zeolite membrane composite 2, which is an Al-treated NH4 + The nitrogen atom / Al atom molar ratio of the zeolite membrane measured by XPS was 0.42, and the Si atom / Al atom molar ratio was 3.01.

[0368] [Example C1] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 2 described in Production Example C1, ammonia / hydrogen / nitrogen The ammonia separation test from the mixed gas was carried out using the apparatus shown in Figure 1 according to the above method, specifically as follows. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 2 at 250°C. The pressure inside the cylinder of the RHO zeolite membrane composite 2 was kept at about 0.3 MPa, and the pressure inside the cylinder was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was used as the feed gas. The gas was passed through at 100 SCCM, and the back pressure was set to 0.4 MPa. At this time, the pressure difference between the feed gas side and the permeate gas side of the RHO zeolite membrane composite 2 was 0.3 MPa. In addition, argon was supplied as a sweep gas from the feed gas 9 at 3.9 SCCM.

[0369] The ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the permeated gas obtained when the mixed gas was passed through the RHO-type zeolite membrane composite 2 at temperatures of 250°C, 300°C, and 325°C are shown in Table 16. The ammonia permeance at 250°C was 1.0 × 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 2.0 × 10 -8 [mol / (m 2 s·Pa)]. From the results in Table 16, the Si atom / Al atom molar ratio was 3.01 by XPS measurement, and NH4 + It can be seen that the use of an RHO-type zeolite membrane enables efficient separation of ammonia. Furthermore, when comparing the ammonia concentrations of the permeated gas obtained at 250°C and 325°C, the Si atom / Al atom molar ratio of this NH4 + In the case of the RHO-type zeolite membrane, the rate of change was almost 0%, indicating that this zeolite membrane is a separation membrane with excellent thermal stability for separation.

[0370] [Table 16]

[0371] [Production Example C2: Production of RHO-type zeolite membrane composite 3] RHO-type zeolite membrane composite 3 was produced by the following method. The support used was the same as in Production Example C1, and the seed crystal dispersion used was the same as in Seed Crystal Dispersion 1 in Production Example C1.

[0372] (Hydrothermal synthesis mixture 2) The following was prepared as raw material mixture 2 for hydrothermal synthesis. 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The crown ether-alkali aqueous solution was added dropwise to 0.2 g of 18-crown-6-ether (CBV720) and 0.2 g of aluminum hydroxide (53.5% by mass of Al2O3, manufactured by Aldrich) to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the resulting raw material mixture for hydrothermal synthesis 2 was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.040 / 0.36 / 0.18 / 50 / 0.18.

[0373] (Production of membrane complex) A seed crystal dispersion liquid 1 and a support were prepared in the same manner as in Production Example C1. The support, the inside of which was evacuated, was immersed in this seed crystal dispersion liquid 1 for 1 minute, and then, with the inside of the support evacuated, The seed crystal was attached to the support by a rubbing method.

[0374] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing a mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and it was heated at 160°C for 24 hours under autogenous pressure.

[0375] After a predetermined time had passed and the composite support-zeolite membrane was allowed to cool, it was removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, remove the template. To obtain an RHO-type zeolite membrane composite, the obtained membrane composite was calcined. This RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and cooled from 100°C to room temperature in 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the zeolite membrane composite after calcination and the weight of the support, and was found to be 56 g / m. 2 was .

[0376] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0377] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0378] Next, the above treatment with 1M ammonium nitrate water was repeated five times, and then the mixture was dried at 100°C for more than 4 hours and then treated with NH4 + The RHO-type zeolite membrane composite was obtained.

[0379] NH4 + The RHO-type zeolite membrane composite was placed in a 65 ml Teflon container (registered trademark) containing 50 g of a 1 M aqueous aluminum nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0380] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more. This is the RHO-type zeolite membrane composite 3, which is the Al-treated NH4 + The nitrogen atom / Al atom molar ratio of the zeolite membrane measured by XPS was 0.76, and the Si atom / Al atom molar ratio was 6.65.

[0381] [Example C2] <Evaluation of membrane separation performance> A separation test of a mixed gas of 12 vol% NH3 / 51 vol% N2 / 37 vol% H2 was carried out under conditions of 250°C and 325°C in the same manner as in Example C1, except that the RHO-type zeolite membrane composite 3 described in Production Example C2 was used instead of the RHO-type zeolite membrane composite 2 described in Production Example C1, and argon was supplied at 8.3 SCCM as a sweep gas.

[0382] The ammonia concentration and the ammonia / hydrogen and ammonia / nitrogen permeance ratios of the obtained permeated gas are shown in Table 17. The ammonia permeance at 250°C was 1.3 x 10 -8 [mol / (m 2 ·s·Pa)], and the permeance of ammonia at 325°C is 2.8 × 10 -8 [mol / (m 2 s Pa)]. From the results in Table 17, the Si atom / Al atom molar ratio of this NH4 + It can be seen that the use of an RHO-type zeolite membrane enables efficient separation of ammonia. Furthermore, when comparing the ammonia concentrations of the permeated gas obtained at 250°C and 325°C, the Si atom / Al atom molar ratio of this NH4 + In the case of the RHO-type zeolite membrane, the rate of change was about 5%, indicating that this zeolite membrane has excellent thermal stability for separation.

[0383] [Table 17]

[0384] [Production Example C3: Production of RHO-type zeolite membrane composite 4] RHO-type zeolite membrane composite 4 was produced by the following method.

[0385] NH4 obtained by the same method as RHO-type zeolite membrane composite 1 in Production Example C1 + The RHO-type zeolite membrane composite was placed in a Teflon container (65 ml) containing 50 g of 1 M aqueous sodium nitrate solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0386] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour, then dried at 100°C for 4 hours or more to remove Na + The RHO-type zeolite membrane composite was then ion-exchanged into the Na + The RHO-type zeolite membrane was placed in a Teflon container (65 ml) containing 50 g of 1 M aqueous aluminum nitrate solution, and the autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0387] After a predetermined time has passed and the membrane is allowed to cool, it is taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more. + The RHO-type zeolite membrane composite was obtained. The molar ratios of Na / Al, N / Al, and Si / Al atoms of the zeolite membrane measured by XPS were 0.05, 1.21, and 7.46, respectively.

[0388] [Example C3] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 4 described in Production Example C3, a test for separating ammonia from a mixed gas of ammonia / hydrogen / nitrogen was carried out by the method described above using the apparatus shown in FIG. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 4 under the condition of 250°C. The pressure was kept at about 0.3 MPa, and the pressure inside the cylinder of the RHO zeolite membrane composite 4 was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was injected for 100 seconds. The pressure was set to 0.4 MPa. The differential pressure between the feed gas side and the permeate gas side of the RHO zeolite membrane composite was 0.3 MPa. Argon was supplied as a sweep gas from the feed gas 9 at 8.3 SCCM. The ammonia concentration and ammonia / hydrogen and ammonia / nitrogen permeance ratios of the obtained permeated gas are shown in Table 18. The ammonia permeance at 250°C was 4.4 x 10 -8 [mol / (m 2 ·s·Pa)] and the permeance of ammonia at 325°C is 1.1 x 10 -7 [mol / (m 2 s Pa)]. From the results in Table 18, XPS The measured Si atom / Al atom molar ratio is 7.46. + RHO type zeolite membrane It can be seen that efficient ammonia separation is possible by using this catalyst. In addition, when comparing the ammonia concentrations of the permeated gas obtained at 250°C and 325°C, the Si atom / Al atom molar ratio is 7.46 as measured by XPS. + In the case of the RHO-type zeolite membrane, the rate of change was about 20%, and it was found that this zeolite membrane is a separation membrane with slightly inferior thermal stability, but still exhibits high thermal stability.

[0389] [Table 18]

[0390] [Production Example C4: Production of RHO-type zeolite membrane composite 5] An RHO-type zeolite membrane composite 5 was produced by the following method. The mixture for hydrothermal synthesis used was the same as the raw material mixture for hydrothermal synthesis 1 in Production Example C1, and the seed crystal dispersion used was the same as the seed crystal dispersion 1.

[0391] (Support) The porous support was an alumina tube (outer diameter 6 mm, inner diameter 4 mm, pore size 0.15 μm, manufactured by Noritake Co., Ltd.) cut into a length of 40 mm, washed with water, and then dried. (Production of membrane complex) The support, the inside of which has been evacuated, is immersed in this seed crystal dispersion liquid 1 for 1 minute, and then the inside of the support is Under vacuum conditions, the seed crystal was attached to the support by rubbing.

[0392] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner cylinder containing the raw material mixture for hydrothermal synthesis 1, the autoclave was sealed, and it was heated at 160°C for 24 hours under autogenous pressure.

[0393] After a predetermined time had passed, the support-zeolite membrane composite was allowed to cool, then removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, the template was removed. To obtain an RHO-type zeolite membrane composite, the obtained membrane composite was calcined. This RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and cooled from 100°C to room temperature in 2 hours. Based on the difference between the weight of the zeolite membrane composite after calcination and the weight of the support, the weight of the RHO-type zeolite crystallized on the support was 52 g / m. 2 It was.

[0394] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0395] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0396] Next, the above treatment with 1M ammonium nitrate water was repeated five times, and then dried at 100°C for 4 hours or more to obtain the RHO-type zeolite membrane composite 5, NH4 + The RHO-type zeolite membrane composite was obtained.

[0397] [Reference example C1] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 5 described in Production Example C4, ammonia (NH3) / Ammonia separation tests from hydrogen (H2) / nitrogen (N2) mixed gas were carried out using the apparatus shown in Figure 1 according to the method described above. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 5 under the condition of 250°C. The pressure was kept at about 0.3 MPa, and the pressure inside the cylinder of the RHO zeolite membrane composite 5 was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was injected for 100 seconds. The pressure was set to 0.4 MPa. The pressure difference between the feed gas side and the permeate gas side of the RHO zeolite membrane composite was 0.3 MPa. Argon was supplied as a sweep gas from the feed gas 9 at 3.9 SCCM. The ammonia concentration and ammonia / hydrogen and ammonia / nitrogen permeance ratios of the obtained permeated gas are shown in Table 19. From these results, it can be seen that the NH4 + The RHO-type zeolite membrane is treated with Al and NH4 +It was revealed that the separation performance of the RHO-type zeolite membrane was lower than that of the NH4 + It has become clear that by treating an RHO-type zeolite membrane with Al and appropriately controlling the ratio of Al atoms to Si atoms in the zeolite membrane, it is possible to design a zeolite membrane that can highly selectively separate ammonia from a mixed gas consisting of multiple components including ammonia and hydrogen and / or nitrogen. The permeance of ammonia at 250°C is 3.0 x 10 -8 [mol / (m 2 ·s· Pa), and the permeance of ammonia at 300°C is 2.9 × 10 -8 [mol / (m 2 ·s·Pa)].

[0398] [Table 19]

[0399] [Example D] [Measurement of physical properties and separation performance] In the following, the physical properties and separation performance of the zeolite or zeolite membrane composite were measured in the same manner as in Example B.

[0400] [Production Example D1: Production of RHO-type zeolite membrane composites 1 and 2] RHO type zeolite membrane composites 1 and 2 were produced by the following method. Prior to the production of the RHO type zeolite membrane composites 1 and 2, a raw material mixture for hydrothermal synthesis 1, a support, and a seed crystal dispersion 1 were prepared as described below.

[0401] (Raw material mixture 1 for hydrothermal synthesis) 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The above crown ether-alkali aqueous solution was added dropwise to CBV720 to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the obtained raw material mixture for hydrothermal synthesis 1 was SiO2 / A l2O3 / NaOH / CsOH / H2O / 18-crown-6-ether=1 / 0.033 / 0.36 / 0.18 / 50 / 0.18.

[0402] (Support) The porous support was an alumina tube (outer diameter 6 mm, inner diameter 4 mm, pore size 0.15 μm, manufactured by Noritake Co., Ltd.) cut to a length of 80 mm, washed with water, and then dried.

[0403] (Seed crystal dispersion 1) 23 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 6 g of NaOH (Kishida Chemical Industry Co., Ltd.), and 5 g of CsOH·H2O (Mitsuwa Chemical Industry Co., Ltd.) were dissolved in 84 g of water. The resulting solution was stirred at 80°C for 3 hours to obtain an aqueous crown ether-alkali solution.

[0404] Next, the crown ether-alkali aqueous solution was added dropwise to 30 g of FAU zeolite (SAR=30, Zeolyst CBV720), and 0.6 g of RHO zeolite seed crystals synthesized according to WO2015020014 was added. The mixture was stirred at room temperature for 2 hours to prepare a mixture. The molar ratio of this mixture was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.033 / 0.30 / 0.06 / 10 / 0.18.

[0405] This mixture was aged at room temperature for 24 hours, then placed in a pressure vessel and placed in a 150°C oven for 72 hours to carry out hydrothermal synthesis. After this hydrothermal synthesis reaction, the reaction solution was cooled and the resulting crystals were collected by filtration. The collected crystals were dried at 100°C for 12 hours to obtain RHO-type zeolite crystals.

[0406] The obtained RHO type zeolite was pulverized in a ball mill to produce a seed crystal dispersion. Specifically, 10 g of the above RHO type zeolite, 300 g of 3φ mm HD alumina balls (manufactured by Nikkato Corporation), and 90 g of water were placed in a 500 mL plastic bottle and pulverized in a ball mill for 6 hours to produce a 10 mass % RHO type zeolite dispersion. Water was added to this zeolite dispersion so that the RHO type zeolite was 1 mass %, and seed crystal dispersion 1 was obtained.

[0407] (Production of Zeolite Membrane Composite) Next, a support with the inside evacuated was immersed in this seed crystal dispersion liquid 1 for 1 minute, and then the support With the inside of the container evacuated to a vacuum, the seed crystal was attached to the support by a rubbing method.

[0408] The support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner cylinder containing a mixture of raw materials for hydrothermal synthesis, the autoclave was sealed, and heated at 160°C for 24 hours under autogenous pressure.

[0409] After a predetermined time had passed, the support-zeolite membrane composite was allowed to cool, then removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, the template was removed. The resulting membrane composite was calcined to obtain an RHO-type zeolite membrane composite. The RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and then calcined for 1 hour. The temperature was lowered from 0°C to room temperature over 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the zeolite membrane composite and the weight of the support after calcination, and was found to be 62 g / m 2 It was.

[0410] Next, the RHO-type zeolite membrane composite after template removal was placed in a Teflon container (65 ml) containing 50 g of 1 M ammonium nitrate aqueous solution. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0411] After a predetermined time had passed and the mixture was allowed to cool, the above treatment was repeated, and the RHO-type zeolite membrane composite that had undergone the above treatment was taken out of the aqueous solution and washed with 100° C. ion-exchanged water for 1 hour.

[0412] After that, the above treatment with 1M ammonium nitrate water was repeated five times, and then dried at 100°C for 4 hours or more to obtain the RHO-type zeolite membrane composite 1, NH4 + The RHO-type zeolite membrane composite was obtained.

[0413] The obtained NH4 + The RHO-type zeolite membrane composite 1 was placed in a Teflon container (65 ml) containing 50 g of a 1 M aqueous solution of sodium nitrate. The autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0414] After a predetermined time has passed and the membrane is left to cool, it is taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour, then dried at 100°C for 4 hours or more to remove Na + The RHO-type zeolite membrane composite was then ion-exchanged into the Na + The RHO-type zeolite membrane was placed in a Teflon container (65 ml) containing 50 g of 1 M aqueous aluminum nitrate solution, and the autoclave was sealed and heated at 100°C for 1 hour in a static state under autogenous pressure.

[0415] After a predetermined time has passed and the membrane is allowed to cool, it is taken out of the aqueous solution, washed with ion-exchanged water, and then dried at 100°C for 4 hours or more. +The RHO-type zeolite composite membrane was obtained. The alkali metal / Al atom molar ratio of the zeolite composite membrane measured by XPS was 0.05, the N atom / Al atom molar ratio was 1.21, and the Si atom / Al atom molar ratio was 7.46.

[0416] [Example D1] <Evaluation of membrane separation performance> Using the RHO-type zeolite membrane composite 2 described in Production Example D1, a test for separating ammonia from a mixed gas of ammonia / hydrogen / nitrogen was carried out by the above-mentioned method using the apparatus of FIG. 1, specifically by the following method. As a pretreatment, a mixed gas of 10% by volume NH3 / 20% by volume H2 / 60% by volume N2 was introduced as a feed gas between the pressure vessel and the RHO zeolite membrane composite 2 under the condition of 250°C. The pressure was kept at about 0.3 MPa, and the pressure inside the cylinder of the RHO zeolite membrane composite 2 was set to 0.098 MPa (atmospheric pressure), and the cylinder was dried for about 120 minutes. Then, a mixture of 12% NH3 by volume, 51% N2 by volume, and 37% H2 by volume was used as the feed gas. The gas was passed through at 100 SCCM, and the back pressure was set to 0.4 MPa. At this time, the pressure difference between the feed gas side and the permeate gas side of the RHO zeolite membrane composite was 0.3 MPa. In addition, argon was supplied as a sweep gas from feed gas 9 at 8.3 SCCM. The ammonia concentration and ammonia / hydrogen and ammonia / nitrogen permeance ratios of the obtained permeated gas are shown in Table 20. From the results in Table 20, Na + Using RHO-type zeolite membrane This shows that ammonia can be separated efficiently. + It was confirmed that the RHO-type zeolite membrane was able to separate ammonia with high selectivity. In addition, the ammonia permeance at 250°C was 4.4 × 10 -8 [mol / (m 2s·Pa), and a comparison with the RHO-type zeolite membrane composite 3 containing no alkali metal, which has the same N atom / Al atom molar ratio and Si atom / Al atom molar ratio as Reference Example D1, reveals that the inclusion of alkali metal atoms enables recovery of ammonia at a similar high concentration with high permeability.

[0417] [Table 20]

[0418] [Production Example D2: Production of RHO-type zeolite membrane composite 3] An RHO-type zeolite membrane composite 3 was produced by the following method. The support used was the same as in Production Example D1, and the seed crystal dispersion used was the same as in Seed Crystal Dispersion 1 in Production Example D1.

[0419] (Hydrothermal synthesis mixture 2) The following was prepared as raw material mixture 2 for hydrothermal synthesis. 6.8 g of 18-crown-6-ether (Tokyo Chemical Industry Co., Ltd.), 2.1 g of NaOH (Kishida Chemical Co., Ltd.), and 4.2 g of CsOH·H2O (Mitsuwa Chemical Co., Ltd.) were dissolved in 125.9 g of water. The solution was stirred at 80°C for 3 hours to obtain a crown ether-alkali aqueous solution. Then, 8.9 g of Y-type (FAU) zeolite (SAR = 30, Zeolyst) was added. The crown ether-alkali aqueous solution was added dropwise to 0.2 g of 18-crown-6-ether (CBV720) and 0.2 g of aluminum hydroxide (53.5% by mass of Al2O3, manufactured by Aldrich) to prepare a raw material mixture for hydrothermal synthesis. The gel composition (molar ratio) of the resulting raw material mixture for hydrothermal synthesis 2 was SiO2 / Al2O3 / NaOH / CsOH / HO / 18-crown-6-ether = 1 / 0.040 / 0.36 / 0.18 / 50 / 0.18.

[0420] (Production of membrane complex) A seed crystal and a support were prepared in the same manner as in Production Example D1, and the support, the inside of which was evacuated, was immersed in this seed crystal dispersion 1 for 1 minute. Thereafter, with the inside of the support still evacuated, the seed crystal was attached to the support by a rubbing method.

[0421] Next, the support with the attached seed crystals was immersed vertically in a Teflon (registered trademark) inner tube containing the raw material mixture 2 for hydrothermal synthesis, the autoclave was sealed, and it was heated at 160°C for 24 hours under autogenous pressure.

[0422] After a predetermined time had passed and the composite support-zeolite membrane was allowed to cool, it was removed from the autoclave, washed with ion-exchanged water, and dried at 100°C for 5 hours or more. After drying, the air permeability in the as-made state was 0.0 L / (m 2 Next, remove the template. To obtain an RHO-type zeolite membrane composite, the obtained membrane composite was calcined. This RHO-type zeolite membrane composite was heated from room temperature to 100°C in 2 hours, heated from 100°C to 300°C in 20 hours, calcined at 300°C for 5 hours, cooled to 100°C in 20 hours, and cooled from 100°C to room temperature in 2 hours. The weight of the RHO-type zeolite crystallized on the support was calculated from the difference between the weight of the zeolite membrane composite after calcination and the weight of the support, and was found to be 56 g / m. 2 was .

[0423] Next, the RHO-type zeolite membrane composite after template removal was dissolved in 1M ammonium nitrate water. The solution was placed in a 65 ml Teflon container (registered trademark) containing 50 g of the solution. The autoclave was sealed and heated at 100° C. for 1 hour under autogenous pressure in a static state.

[0424] After a predetermined time had passed and the membrane was allowed to cool, it was taken out of the aqueous solution and washed with ion-exchanged water at 100°C for 1 hour.

[0425] Next, the above treatment with 1M ammonium nitrate water was repeated five times, and then the mixture was dried at 100°C for more than 4 hours and then treated with NH4 +The RHO-type zeolite membrane composite was obtained.

[0426] NH4 + The RHO-type zeolite membrane composite was placed in a 65 ml Teflon container (registered trademark) cont...

Claims

1. A zeolite membrane comprising a zeolite, wherein the molar ratio of nitrogen element to Al element determined by X-ray photoelectron spectroscopy is 0.01 or more and 1 or less, and the molar ratio of Si element to Al element determined by X-ray photoelectron spectroscopy is 2.0 or more and 10 or less, and the zeolite is an RHO-type or MFI-type aluminosilicate zeolite.

2. The zeolite is NH ４ ＋ The zeolite membrane of claim 1 , comprising:

3. The zeolite membrane according to claim 1 or 2, wherein the zeolite membrane is for ammonia separation.

4. 4. The zeolite membrane according to claim 1, wherein the molar ratio of alkali metal element to Al element determined by X-ray photoelectron spectroscopy is 0.01 or more and 0.070 or less.

5. A zeolite membrane further comprising a silylated layer laminated on the outer surface of the zeolite membrane according to any one of claims 1 to 4.

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