Zeolite membrane composite, method for producing zeolite membrane composite, and separation method

Abstract

A zeolite membrane composite body (1) according to the present invention is provided with a porous supporting body (11), and a zeolite membrane (12) that is provided on the supporting body (11). With respect to the zeolite membrane (12), the Si / Al molar ratio increases from an interface part (121) at the interface with the supporting body (11) toward the membrane inner side, while the Si / Al molar ratio decreases from the membrane inner side toward a surface part (122) that is on the reverse side from the supporting body (11). Consequently, the present invention enables the achievement of a zeolite membrane composite body (1) which has high water permeation flux and high hydrothermal durability, while being suppressed in membrane separation.

Description

[Technical Field]

[0001] The present invention relates to a zeolite membrane composite, a method for producing a zeolite membrane composite, and a method for separating them. [Reference to related applications] This application claims priority from Japanese Patent Application JP2022-029614, filed on 28 February 2022, and all disclosures of said application are incorporated herein. [Background technology]

[0002] Generally, zeolite membranes with a high Si / Al ratio are known to have high hydrothermal resistance, while zeolite membranes with a low Si / Al ratio are known to have high water permeation flux. Therefore, in International Publication No. 2018 / 225787 (Reference 1), a separation membrane is disclosed in which a first zeolite membrane with a high Si / Al ratio (high-silica zeolite membrane) and a second zeolite membrane with a low Si / Al ratio (low-silica zeolite membrane) are laminated to achieve both high hydrothermal resistance and high water permeation flux.

[0003] Furthermore, Japanese Patent Publication No. 6748104 (Reference 2) discloses a crystalline pure silica film formed on the surface of a porous substrate. This pure silica film has a CHA-type crystalline structure, and the portion from the film surface to 2 μm is composed only of silicon and oxygen. Because the pure silica film in Reference 2 has high hydrophobicity, it is thought that the water permeation flux will be low. Japanese Patent Publication No. 4759724 (Reference 3) discloses a zeolite film formed on a porous substrate, in which the Si / Al ratio is continuously or stepwise sloped in the depth direction of the film. International Publication No. 2017 / 169591 (Reference 4) discloses a method for manufacturing a porous support, etc. Japanese Patent Application Publication No. 2004-83375 (Reference 5) discloses a method for manufacturing DDR-type zeolite.

[0004] Incidentally, in the separation membrane described in Reference 1, a zeolite membrane with a high Si / Al ratio (i.e., low polarity) comes into contact with a porous support having polar hydroxyl groups on its surface. This results in poor adhesion to the support, making the membrane prone to delamination. Furthermore, in Reference 1, a first zeolite membrane is formed using one raw material solution, and then a second zeolite membrane is formed using another raw material solution, which requires a long time to prepare the separation membrane. [Overview of the Initiative]

[0005] This invention is directed towards zeolite membrane composites and aims to provide zeolite membrane composites with high water permeation flux and hydrothermal resistance, and suppressed membrane delamination, as well as to efficiently manufacture such zeolite membrane composites.

[0006] The invention of Embodiment 1 is a zeolite membrane composite comprising a porous support and a zeolite membrane provided on the support. In the zeolite membrane, the Si / Al ratio, which is a molar ratio, increases from the interface with the support toward the interior of the membrane, and decreases from the interior of the membrane toward the surface opposite to the support.

[0007] According to the present invention, it is possible to provide a zeolite membrane composite with high water permeability flux and hydrothermal resistance, and in which membrane delamination is suppressed.

[0008] The invention of Embodiment 2 is a zeolite film composite of Embodiment 1, wherein the Si / Al ratio in the zeolite film changes in the thickness direction, and the Si / Al ratio becomes twice or more the Si / Al ratio of the surface portion. The aforementioned thickness direction The length of the range is 25% or more of the thickness of the zeolite film.

[0009] The invention of embodiment 3 is a zeolite film composite according to embodiment 1 or 2, wherein the maximum Si / Al ratio in the zeolite film is 180 or more as the Si / Al ratio changes in the thickness direction.

[0010] The invention of embodiment 4 is a zeolite film composite according to any one of embodiments 1 to 3, wherein the Si / Al ratio at the surface portion of the zeolite film is 120 or less.

[0011] The invention of embodiment 5 is a zeolite film composite according to any one of embodiments 1 to 4, wherein, in the thickness direction change of the Si / Al ratio in the zeolite film, the first position from the interface toward the interior of the film where the Si / Al ratio becomes half of the maximum Si / Al ratio of the zeolite film and the support are The aforementioned thickness direction The length of the range is 25% or more of the thickness of the zeolite film.

[0012] The invention of embodiment 6 is a zeolite membrane composite according to any one of embodiments 1 to 5, wherein the zeolite constituting the zeolite membrane is an 8-membered ring zeolite.

[0013] The invention of embodiment 7 is a method for producing a zeolite membrane composite, comprising the steps of: a) preparing a raw material solution by mixing a Si source and two types of Al sources with different solubility in water with water; b) immersing a porous support in the raw material solution; and c) heating the raw material solution to form a zeolite membrane on the support. In step c), hydrothermal synthesis is performed at a temperature in which substantially all of one of the two types of Al sources contained in the raw material solution dissolves, and at least a portion of the other Al source does not dissolve, and then hydrothermal synthesis is performed at a temperature higher than the said temperature. This makes it possible to efficiently produce the zeolite membrane composite.

[0014] The invention of embodiment 8 is a separation method comprising: a) preparing a zeolite membrane composite according to any one of embodiments 1 to 6; and b) supplying a mixed substance containing a plurality of types of gases or liquids to the zeolite membrane composite, and separating a substance with high permeability in the mixed substance from other substances by allowing it to pass through the zeolite membrane composite.

[0015] The above object and other objects, features, aspects and advantages will be clarified by the following detailed description of the present invention with reference to the accompanying drawings.

Brief Description of the Drawings

[0016] [Figure 1] It is a cross-sectional view of a zeolite membrane composite. [Figure 2] It is a cross-sectional view showing an enlarged part of the zeolite membrane composite. [Figure 3] It is a diagram for explaining the change in the Si / Al ratio in the thickness direction of the zeolite membrane. [Figure 4] It is a diagram showing the manufacturing process flow of the zeolite membrane composite. [Figure 5A] It is a diagram schematically showing the state of the raw material solution. [Figure 5B] It is a diagram schematically showing the state of the raw material solution. [Figure 5C] It is a diagram schematically showing the state of the raw material solution. [Figure 6] It is a diagram showing a separation device. [Figure 7] It is a diagram showing the separation flow of a mixture. [Figure 8A] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane. [Figure 8B] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane. [Figure 8C] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane. [Figure 8D] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane. [Figure 8E] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane. [Figure 9A] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane of a comparative example. [Figure 9B] It is a diagram showing the change in the Si / Al ratio in the thickness direction of the zeolite membrane of a comparative example. [Figure 9C]This figure shows the change in the Si / Al ratio in the thickness direction of the zeolite film of the comparative example. [Figure 10] This is a diagram illustrating the measurement of vacuum levels. [Modes for carrying out the invention]

[0017] Figure 1 is a cross-sectional view of the zeolite membrane composite 1. Figure 2 is an enlarged cross-sectional view showing a part of the zeolite membrane composite 1. The zeolite membrane composite 1 comprises a porous support 11 and a zeolite membrane 12 provided on the support 11. The zeolite membrane is defined as a zeolite film formed on the surface of the support 11, and does not include a film in which zeolite particles are simply dispersed in an organic membrane. The zeolite membrane 12 may also contain two or more types of zeolites with different structures and compositions. In Figure 1, the zeolite membrane 12 is drawn with a thick line. In Figure 2, the zeolite membrane 12 is drawn with parallel diagonal lines. Also, in Figure 2, the thickness of the zeolite membrane 12 is drawn thicker than it actually is.

[0018] The support 11 is a porous member that can permeate gases and liquids. In the example shown in Figure 1, the support 11 is a monolithic support in which a plurality of through holes 111 extending in the longitudinal direction (i.e., the left-right direction in Figure 1) are provided on a single, integrally molded columnar body. In the example shown in Figure 1, the support 11 is approximately cylindrical. The cross-section perpendicular to the longitudinal direction of each through hole 111 (i.e., cell) is, for example, approximately circular. In Figure 1, the diameter of the through holes 111 is depicted as larger than it actually is, and the number of through holes 111 is depicted as fewer than it actually is. The zeolite film 12 is formed on the inner circumferential surface of the through holes 111 and covers the inner circumferential surface of the through holes 111 over substantially the entire surface.

[0019] The length of the support 11 (i.e., the length in the left-right direction in Figure 1) is, for example, 10 cm to 200 cm. The outer diameter of the support 11 is, for example, 0.5 cm to 30 cm. The distance between the central axes of adjacent through holes 111 is, for example, 0.3 mm to 10 mm. The surface roughness (Ra) of the support 11 is, for example, 0.1 μm to 5.0 μm, preferably 0.2 μm to 2.0 μm. The shape of the support 11 may be, for example, honeycomb, flat, tubular, cylindrical, columnar, or polygonal prism. If the shape of the support 11 is tubular or cylindrical, the thickness of the support 11 is, for example, 0.1 mm to 10 mm.

[0020] The material of the support 11 can be any material (e.g., ceramic or metal) as long as it has chemical stability during the process of forming the zeolite film 12 on its surface. In this embodiment, the support 11 is formed from a ceramic sintered body. Examples of ceramic sintered bodies selected as the material for the support 11 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, the support 11 includes at least one of alumina, mullite, and zirconia.

[0021] The support 11 may contain an inorganic binder. At least one of titania, mullite, easily sinterable alumina, silica, glass frit, clay minerals, and easily sinterable cordierite can be used as the inorganic binder.

[0022] The average pore size of the support 11 is, for example, 0.01 μm to 70 μm, preferably 0.05 μm to 25 μm. The average pore size of the support 11 near the surface where the zeolite film 12 is formed is 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. The average pore size can be measured, for example, by a mercury porosimeter, palm porometer, or nanopalm porometer. For the distribution of pore size throughout the support 11, including the surface and interior, D5 is, for example, 0.01 μm to 50 μm, D50 is, for example, 0.05 μm to 70 μm, and D95 ​​is, for example, 0.1 μm to 2000 μm. The porosity of the support 11 near the surface where the zeolite film 12 is formed is, for example, 25% to 50%.

[0023] The support 11 has a multilayer structure in which multiple layers with different average pore diameters are stacked in the thickness direction. The average pore diameter and sintered grain size in the surface layer, including the surface on which the zeolite film 12 is formed, are smaller than the average pore diameter and sintered grain size in the layers other than the surface layer. The average pore diameter of the surface layer of the support 11 is, for example, 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. When the support 11 has a multilayer structure, the materials of each layer can be those described above. The materials of the multiple layers forming the multilayer structure may be the same or different.

[0024] The zeolite membrane 12 is a porous membrane having pores. The zeolite membrane 12 can be used as a separation membrane to separate a specific substance from a mixture of multiple substances using molecular sieving action. Other substances are less permeable through the zeolite membrane 12 than the specific substance. In other words, the amount of other substances that permeate through the zeolite membrane 12 is small compared to the amount of the specific substance that permeates through it.

[0025] The thickness of the zeolite film 12 is, for example, 0.05 μm to 30 μm, preferably 0.1 μm to 20 μm, and more preferably 0.5 μm to 10 μm. Increasing the thickness of the zeolite film 12 improves separation performance. Thinning the zeolite film 12 increases the transmission rate. The surface roughness (Ra) of the zeolite film 12 is, for example, 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0026] The average pore diameter of the zeolite film 12 is, for example, 1 nm or less. Preferably, the average pore diameter of the zeolite film 12 is 0.2 nm or more and 0.8 nm or less, more preferably 0.3 nm or more and 0.7 nm or less, and even more preferably 0.3 nm or more and 0.6 nm or less. If the average pore diameter is greater than 1 nm, the separation performance may decrease. Also, if the average pore diameter is less than 0.2 nm, the transmission rate may decrease. The average pore diameter of the zeolite film 12 is smaller than the average pore diameter of the support 11 near the surface on which the zeolite film 12 is formed.

[0027] If the maximum number of member rings in the zeolite constituting the zeolite membrane 12 is n, the average pore diameter is defined as the arithmetic mean of the short and long axes of the n-membered ring pores. An n-membered ring pore is a pore in which the number of oxygen atoms in the ring structure formed by oxygen atoms bonded to T atoms (described later) is n. If the zeolite has multiple types of n-membered ring pores with equal n, the average pore diameter of the zeolite is defined as the arithmetic mean of the short and long axes of all types of n-membered ring pores. Thus, the average pore diameter of the zeolite membrane is uniquely determined by the skeletal structure of the zeolite, as can be seen in the International Zeolite Society's "Database of Zeolite Structures" [online] and the Internet.<URL:http: / / www.iza-structure.org / databases / > It can be determined from the values ​​disclosed.

[0028] The type of zeolite constituting the zeolite membrane 12 is not particularly limited, but may be, for example, AEI type, AEN type, AFN type, AFV type, AFX type, BEA type, CHA type, DDR type, ERI type, ETL type, FAU type (X type, Y type), GIS type, LEV type, LTA type, MEL type, MFI type, MOR type, PAU type, RHO type, SAT type, SOD type, etc.

[0029] From the viewpoint of improving separation performance, it is preferable that the maximum number of member rings of the zeolite constituting the zeolite membrane 12 is 8. That is, it is preferable that the zeolite is an 8-membered ring zeolite. The zeolite membrane 12 is, for example, a DDR-type zeolite. In other words, the zeolite membrane 12 is a zeolite membrane composed of a zeolite whose structural code as defined by the International Zeolite Society is "DDR". In this case, the intrinsic pore size of the zeolite constituting the zeolite membrane 12 is 0.36 nm × 0.44 nm, and the average pore size is 0.40 nm.

[0030] Typically, the zeolite constituting the zeolite film 12 is an aluminosilicate zeolite in which the central atoms (T atoms) of the oxygen tetrahedrons (TO4) constituting the zeolite are composed of silicon (Si) and aluminum (Al). Some of the T atoms may be substituted with other elements. The zeolite film 12 may also contain alkali metals. These alkali metals are, for example, sodium (Na) or potassium (K).

[0031] Figure 3 is a diagram illustrating the change in the Si / Al ratio in the zeolite film 12 in the thickness direction. The lower part of Figure 3 shows the change in the Si / Al ratio in the zeolite film 12 in the thickness direction. The vertical axis in the lower part of Figure 3 represents the Si / Al ratio, and the horizontal axis represents the position in the thickness direction (depth direction) with the surface of the zeolite film 12 set to 0 (the same applies to Figures 8A to 8E and Figures 9A to 9C described later). The upper part of Figure 3 shows a part of the cross-section of the zeolite film 12 and the support 11, and the cross-section showing the zeolite film 12 has a gradient that becomes darker as the Si / Al ratio increases. The Si / Al ratio is a molar ratio, obtained by dividing the number of moles of Si atoms by the number of moles of Al atoms. The change in the Si / Al ratio in the thickness direction is determined by performing a depth-direction composition analysis on the zeolite film 12 after cleaning (1 nm sputtering to remove surface contamination layer) using X-ray photoelectron spectroscopy (XPS). Furthermore, in the case of changes in the Si / Al ratio in the thickness direction, the range in the thickness direction where the Si / Al ratio is less than 1 is considered to be the support 11.

[0032] The zeolite film 12 has an interface portion 121 and a surface portion 122. The interface portion 121 is the part that forms the interface with the support 11, and the surface portion 122 is the part that forms the surface opposite to the support 11. In the zeolite film 12, the portion between the interface portion 121 and the surface portion 122 is called the film interior, and the Si / Al ratio changes almost continuously in the thickness direction from the interface portion 121 through the film interior to the surface portion 122. Specifically, as shown in the lower part of Figure 3, the Si / Al ratio gradually increases from the interface portion 121 toward the film interior and gradually decreases from the film interior toward the surface portion 122. That is, the change in the thickness direction of the Si / Al ratio has a bell-shaped curve with a slope that increases toward the film interior on both the interface portion 121 side and the surface portion 122 side. In reality, the value of the Si / Al ratio may fluctuate due to measurement variations. In this case, when measurements are taken from the film surface toward the support 11, the actual value is used for the film surface, the average of the three points (the first, second, and third points) is used for the second point, and the average of the five points (the first two points and the second two points) is used for the third point and beyond to obtain the change in the thickness direction of the Si / Al ratio. If the change in the Si / Al ratio shows a continuous increasing or decreasing trend (except for locations near where the trend shifts from increasing to decreasing within the film), it is determined that the Si / Al ratio is changing continuously. Note that if, for example, Al is below the detection limit at a location within the film, the Si / Al ratio at that location may be excluded. Furthermore, the Si / Al ratio at that location may be interpolated using nearby values, or it may be calculated using the detection limit of Al.

[0033] In the zeolite film 12, the Si / Al ratio Va at the surface portion 122 is relatively small, and the surface portion 122 contains a large amount of Al. This increases the polarity of the surface portion 122, resulting in high hydrophilicity and achieving a high water permeation flux. The Si / Al ratio Va of the surface portion 122 is, for example, less than half of the maximum Si / Al ratio Vb described later. The Si / Al ratio Va is preferably 120 or less, more preferably 110 or less, and even more preferably 100 or less. This makes it possible to more reliably improve the water permeation flux. The lower limit of the Si / Al ratio Va of the surface portion 122 is not particularly limited, but is, for example, 1.

[0034] In the zeolite film 12, high water and heat resistance is achieved due to the relatively large Si / Al ratio within the film. As described later, water and heat resistance can be evaluated by the degree of decrease in vacuum before and after immersing the zeolite film composite 1 in heated water. When the Si / Al ratio changes in the thickness direction, the range in the thickness direction where the Si / Al ratio is twice or more than the Si / Al ratio Va of the surface portion 122 is called the "high Si / Al ratio range". The ratio (La / T) of the length La in the thickness direction of the high Si / Al ratio range to the thickness T of the zeolite film 12 is preferably 25% or more, more preferably 28% or more, and even more preferably 30% or more. Furthermore, the maximum Si / Al ratio Vb in the thickness direction of the Si / Al ratio change is preferably 180 or more, more preferably 200 or more, and even more preferably 220 or more. The upper limit of the maximum Si / Al ratio Vb is not particularly limited, but for example, it is 300. As described above, the high Si / Al ratio in the zeolite film 12 is more reliably improved by having a wide area of ​​high Si / Al ratio and / or a large maximum Si / Al ratio Vb.

[0035] In the zeolite film 12, delamination is suppressed due to the relatively small Si / Al ratio at the interface 121. The reason why delamination is suppressed in the zeolite film 12 is not entirely clear, but it is thought that the adhesion between the zeolite film 12 and the surface of the support 11 is enhanced because the hydroxyl groups on the surface of the support 11 are polar, while the interface 121, which has a small Si / Al ratio and contains a large amount of Al, is also highly polar. When the Si / Al ratio changes in the thickness direction, if we refer to the range in the thickness direction between the first position where the Si / Al ratio becomes half of the maximum Si / Al ratio Vb of the zeolite film 12 as you move from the interface 121 towards the interior of the film, and the support 11, as the "interface-side area of ​​interest," then the ratio of the length Lb of the interface-side area of ​​interest in the thickness direction to the thickness T of the zeolite film 12 (Lb / T) is preferably 25% or more, more preferably 30% or more, and even more preferably 35% or more. This makes it possible to suppress delamination more reliably.

[0036] Next, with reference to Figure 4, an example of the manufacturing flow of the zeolite membrane composite 1 will be described. When the zeolite membrane composite 1 is manufactured, first, seed crystals to be used in the manufacture of the zeolite membrane 12 are prepared (step S11). Seed crystals are obtained, for example, from DDR-type zeolite powder produced by hydrothermal synthesis. The zeolite powder may be used as seed crystals as is, or seed crystals may be obtained by processing the powder by pulverization or the like.

[0037] Next, the porous support 11 is immersed in a dispersion containing seed crystals to attach the seed crystals to the support 11 (step S12). Alternatively, the seed crystals are attached to the support 11 by bringing the dispersion containing seed crystals into contact with the portion of the support 11 on which the zeolite film 12 is to be formed. This creates a support with attached seed crystals. The seed crystals may also be attached to the support 11 by other methods.

[0038] Furthermore, a raw material solution used for the formation of the zeolite film 12 is prepared (step S13). The raw material solution is prepared by mixing, for example, a Si source, two types of Al sources (hereinafter referred to as "first Al source" and "second Al source"), and a structure-directing agent (hereinafter also called "SDA") with water (H2O). In this example, the Si source is amorphous silica (e.g., silica sol). The Si source may also be colloidal silica, fumed silica, sodium silicate, silicon alkoxide, water glass, etc. The first Al source and the second Al source have different solubility in water. Specifically, in the temperature range from the initial temperature to the first synthesis temperature during hydrothermal synthesis described later, the solubility of the first Al source in water is higher than that of the second Al source. The first Al source is, for example, a water-soluble aluminum compound, such as sodium aluminate, aluminum hydroxide, and aluminum alkoxide. The second Al source is, for example, a poorly water-soluble aluminum compound, such as boehmite and aluminum oxide. The SDA is, for example, an organic substance. Examples of SDAs include 1-adamantanamine, tetramethylammonium hydroxide, and choline chloride. Other raw materials, such as a sodium source, may be mixed into the raw material solution.

[0039] Once the raw material solution is prepared, the support 11 with the seed crystal attached is immersed in the raw material solution (step S14). Subsequently, a DDR-type zeolite film 12 is formed on the support 11 by growing a DDR-type zeolite on the seed crystal as a nucleus through hydrothermal synthesis (step S15). In hydrothermal synthesis, the raw material solution is heated in two stages. In this example, the raw material solution is heated from an initial temperature (e.g., room temperature) to a first synthesis temperature, and then maintained at a constant temperature at the first synthesis temperature. After a predetermined time has elapsed since reaching the first synthesis temperature, the raw material solution is heated from the first synthesis temperature to a second synthesis temperature higher than the first synthesis temperature, and then maintained at a constant temperature at the second synthesis temperature. After a predetermined time has elapsed since reaching the second synthesis temperature, the temperature of the raw material solution is returned to near the initial temperature.

[0040] Figures 5A to 5C schematically show the state of the raw material solution. In this processing example, at the initial temperature, almost all of the water-soluble first Al source is dissolved in the water. During the period when the raw material solution is heated from the initial temperature to the first synthesis temperature and held, as shown in Figure 5A, the Si source 80 dispersed in the raw material solution gradually dissolves in the water, and the Si concentration of the raw material solution (i.e., the concentration of Si dissolved in water) increases. As a result, as shown in the lower part of Figure 3, the Si / Al ratio in the zeolite film 12 gradually increases from the interface 121 toward the interior of the film. Depending on the amount of the first Al source in the raw material solution, almost all of the first Al source (for example, 99% or more) may dissolve in the water at the first synthesis temperature. At the first synthesis temperature, the second Al source 82 is hardly dissolved in the water and is in a dispersed state. At the first synthesis temperature, a portion of the second Al source 82 may dissolve in the water. Furthermore, as mentioned above, even when a seed crystal is used, the seed crystal grows while incorporating Al dissolved in the raw material solution, so the Si / Al ratio at the interface 121 changes almost continuously in the thickness direction.

[0041] As shown in Figure 5B, once all of the Si source 80 is dissolved in water, the dissolved Si and Al are consumed in a nearly constant proportion for the formation of the zeolite film 12, and the Si / Al ratio becomes approximately constant near the maximum Si / Al ratio Vb. Subsequently, during the period when the raw material solution is heated from the first synthesis temperature to the second synthesis temperature and held, as shown in Figure 5C, the second Al source 82 dispersed in the raw material solution gradually dissolves in water, and the Al concentration of the raw material solution (i.e., the concentration of Al dissolved in water) increases. As a result, in the zeolite film 12, the Si / Al ratio gradually decreases from the inside of the film toward the surface 122. In this way, by controlling the amount of Si and Al in the raw material solution (synthesis sol), a zeolite film 12 is formed in which the Si / Al ratio changes continuously and in a curved shape in the thickness direction. A zeolite film 12 in which the Si / Al ratio changes continuously can be considered as a single-layer film.

[0042] In this example, the first synthesis temperature is a temperature at which the first Al source is almost completely dissolved and the second Al source is not completely dissolved (i.e., at least a portion of the second Al source is not dissolved), for example, 100 to 130°C, preferably 120 to 130°C. The second synthesis temperature is a higher temperature than the first synthesis temperature, for example, 130 to 150°C, preferably 140 to 150°C. The holding time at the first synthesis temperature is, for example, 4 to 15 hours, preferably 4 to 11 hours. The holding time at the second synthesis temperature is, for example, 1 to 10 hours, preferably 2 to 7 hours. The total holding time at the first and second synthesis temperatures is, for example, 5 to 25 hours. In the synthesis of the zeolite film 12, it is not necessarily required to maintain a constant temperature for a period of time. For example, by appropriately changing the rate of temperature change during heating, a zeolite film 12 may be formed in which the Si / Al ratio increases from the interface 121 towards the interior of the film and decreases from the interior towards the surface 122.

[0043] After the hydrothermal synthesis is complete, the support 11 and the zeolite membrane 12 are washed with pure water. After washing, the support 11 and the zeolite membrane 12 are dried, for example, at 80°C. After drying the support 11 and the zeolite membrane 12, the zeolite membrane 12 is heat-treated to almost completely burn off the SDA in the zeolite membrane 12, allowing it to penetrate the micropores within the zeolite membrane 12. This yields the zeolite membrane composite 1 described above.

[0044] Next, the separation of mixed substances using the zeolite membrane composite 1 will be explained with reference to Figures 6 and 7. Figure 6 is a diagram of the separation apparatus 2. Figure 7 is a diagram of the separation flow of the mixed substances by the separation apparatus 2.

[0045] In separation device 2, a mixed substance containing multiple types of fluids (i.e., gas or liquid) is supplied to zeolite membrane composite 1, and substances with high permeability in the mixed substance (hereinafter also referred to as "high-permeability substances") are separated from the mixed substance by passing them through the zeolite membrane composite 1. The separation in separation device 2 may be performed, for example, for the purpose of extracting high-permeability substances from the mixed substance, or for the purpose of concentrating substances with low permeability (hereinafter also referred to as "low-permeability substances").

[0046] The mixed substance (i.e., the mixed fluid) may be a mixed gas containing multiple types of gases, a mixed liquid containing multiple types of liquids, or a gas-liquid two-phase fluid containing both gas and liquid.

[0047] The mixed substance includes, for example, one or more substances from among hydrogen (H2), helium (He), nitrogen (N2), oxygen (O2), water (H2O), carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, ammonia (NH3), sulfur oxides, hydrogen sulfide (H2S), sulfur fluoride, mercury (Hg), arsine (AsH3), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1-C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. The highly permeable substance mentioned above is, for example, one or more substances from among H2, He, N2, O2, CO2, NH3, and H2O, and is preferably H2O.

[0048] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5). X It is a gas called (NOX).

[0049] Sulfur oxides are compounds of sulfur and oxygen. Examples of sulfur oxides include sulfur dioxide (SO2), sulfur trioxide (SO3), and other SO2 compounds. X It is a gas called (socks).

[0050] Sulfur fluoride is a compound of fluorine and sulfur. Examples of sulfur fluoride include disulfur difluoride (FSSF, S=SF2), sulfur difluoride (SF2), sulfur tetrafluoride (SF4), sulfur hexafluoride (SF6), or disulfur decafluoride (S2F). 10 ) etc.

[0051] C1-C8 hydrocarbons are hydrocarbons containing one to eight carbon atoms. C3-C8 hydrocarbons may be linear compounds, side-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be either saturated hydrocarbons (i.e., those without double or triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double and / or triple bonds in the molecule). Examples of C1-C4 hydrocarbons include methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), n-butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), or isobutene (CH2=C(CH3)2).

[0052] The organic acids mentioned above are carboxylic acids or sulfonic acids, etc. Examples of carboxylic acids include formic acid (CH2O2), acetic acid (C2H4O2), oxalic acid (C2H2O4), acrylic acid (C3H4O2), or benzoic acid (C6H5COOH). Examples of sulfonic acids include ethanesulfonic acid (C2H6O3S). These organic acids may be chain compounds or cyclic compounds.

[0053] The alcohols mentioned above include, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)), or butanol (C4H9OH).

[0054] Mercaptans are organic compounds that have a hydrogenated sulfur (SH) group at their terminus, and are also known as thiols or thioalcohols. Examples of mercaptans include methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), or 1-propanethol (C3H7SH).

[0055] The esters mentioned above include, for example, formic acid esters or acetate esters.

[0056] The ethers mentioned above include, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3), diethyl ether ((C2H5)2O), or tetrahydrofuran ((CH2)4O).

[0057] The ketones mentioned above include, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO).

[0058] The aldehydes mentioned above include, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO), or butanal (butyraldehyde) (C3H7CHO).

[0059] In the following explanation, the mixed substance separated by separation device 2 is described as a mixture containing multiple types of liquids, and the separation is performed by pervaporation.

[0060] The separation device 2 comprises a zeolite membrane composite 1, a sealing section 21, a housing 22, two sealing members 23, a supply section 26, a first recovery section 27, and a second recovery section 28. The zeolite membrane composite 1, the sealing section 21, and the sealing members 23 are housed within the housing 22. The supply section 26, the first recovery section 27, and the second recovery section 28 are located outside the housing 22 and connected to it.

[0061] The sealing portion 21 is attached to both ends of the support 11 in the longitudinal direction (i.e., the left-right direction in Figure 6) and is a member that covers and seals both longitudinal end faces of the support 11 and the outer peripheral surface near those end faces. The sealing portion 21 prevents liquid from flowing in and out from these end faces of the support 11. The sealing portion 21 is, for example, a plate-shaped member made of glass or resin. The material and shape of the sealing portion 21 may be changed as appropriate. Note that the sealing portion 21 has multiple openings that overlap with the multiple through holes 111 of the support 11, so the longitudinal ends of each through hole 111 of the support 11 are not covered by the sealing portion 21. Therefore, liquid can flow in and out of the through holes 111 from these ends.

[0062] The shape of the housing 22 is not particularly limited, but for example, it is a substantially cylindrical tubular member. The housing 22 is made of, for example, stainless steel or carbon steel. The longitudinal direction of the housing 22 is substantially parallel to the longitudinal direction of the zeolite membrane composite 1. A supply port 221 is provided at one end of the housing 22 in the longitudinal direction (i.e., the left end in Figure 6), and a first discharge port 222 is provided at the other end. A second discharge port 223 is provided on the side of the housing 22. A supply unit 26 is connected to the supply port 221. A first recovery unit 27 is connected to the first discharge port 222. A second recovery unit 28 is connected to the second discharge port 223. The internal space of the housing 22 is a sealed space isolated from the space surrounding the housing 22.

[0063] The two sealing members 23 are positioned around the entire circumference of the zeolite membrane composite 1, between the outer circumferential surface of the zeolite membrane composite 1 and the inner circumferential surface of the housing 22, near both longitudinal ends of the zeolite membrane composite 1. Each sealing member 23 is a substantially annular member formed of a material that is impermeable to liquids. The sealing member 23 is, for example, an O-ring made of a flexible resin. The sealing member 23 adheres tightly to the outer circumferential surface of the zeolite membrane composite 1 and the inner circumferential surface of the housing 22 over its entire circumference. In the example shown in Figure 6, the sealing member 23 adheres tightly to the outer circumferential surface of the sealing portion 21 and indirectly adheres to the outer circumferential surface of the zeolite membrane composite 1 via the sealing portion 21. The space between the sealing member 23 and the outer circumferential surface of the zeolite membrane composite 1, and the space between the sealing member 23 and the inner circumferential surface of the housing 22 are sealed, making it almost impossible or impossible for liquids to pass through.

[0064] The supply unit 26 supplies the mixed liquid to the internal space of the housing 22 via the supply port 221. The supply unit 26 includes, for example, a pump that pressurizes the mixed liquid toward the housing 22. The pump includes a temperature control unit and a pressure control unit that adjust the temperature and pressure of the mixed liquid supplied to the housing 22, respectively. The first recovery unit 27 includes, for example, a storage container for storing the liquid discharged from the housing 22, or a pump for transferring the liquid. The second recovery unit 28 includes, for example, a vacuum pump that reduces the pressure in the space outside the outer peripheral surface of the zeolite membrane composite 1 within the housing 22 (i.e., the space sandwiched between the two sealing members 23), and a cooling chiller trap that cools and liquefies the gas that has vaporized and permeated through the zeolite membrane composite 1.

[0065] When the mixed liquid is separated, the separation device 2 described above is prepared to create the zeolite membrane composite 1 (Figure 7: Step S21). Subsequently, the supply unit 26 supplies a mixed liquid containing multiple types of liquids with different permeability to the zeolite membrane 12 into the internal space of the housing 22. For example, the main components of the mixed liquid are water (H2O) and ethanol (C2H5OH). The mixed liquid may also contain liquids other than water and ethanol. The pressure of the mixed liquid supplied from the supply unit 26 to the internal space of the housing 22 (i.e., the introduction pressure) is, for example, 0.1 MPa to 2 MPa, and the temperature of the mixed liquid is, for example, 10°C to 200°C.

[0066] The mixed liquid supplied from the supply unit 26 to the housing 22 is introduced into each through-hole 111 of the support 11 from the left end of the zeolite membrane composite 1 in the diagram, as indicated by arrow 251. High-permeability substances, which are liquids with high permeability in the mixed liquid, vaporize and pass through the zeolite membrane 12 provided on the inner circumferential surface of each through-hole 111, and the support 11, and are led out from the outer circumferential surface of the support 11. In this way, high-permeability substances (e.g., water) are separated from low-permeability substances (e.g., ethanol), which are liquids with low permeability in the mixed liquid (step S22).

[0067] The gas discharged from the outer surface of the support 11 (hereinafter referred to as "permeate") is guided to the second recovery unit 28 via the second discharge port 223, as indicated by arrow 253, where it is cooled and recovered as a liquid. The pressure (i.e., permeate pressure) of the gas recovered by the second recovery unit 28 via the second discharge port 223 is, for example, about 6.67 kPa (about 50 Torr). In addition to the highly permeable substance described above, the permeate may also include a low-permeability substance that has permeated through the zeolite film 12.

[0068] Furthermore, the liquid from the mixed solution, excluding the substance that permeated the zeolite membrane 12 and the support 11 (hereinafter referred to as "impermeable substance"), passes through each through-hole 111 of the support 11 from left to right in the figure and is recovered by the first recovery unit 27 via the first discharge port 222, as indicated by arrow 252. The pressure of the liquid recovered by the first recovery unit 27 via the first discharge port 222 is, for example, approximately the same as the introduction pressure. In addition to the low-permeability substance described above, the impermeable substance may also include a high-permeability substance that did not permeate the zeolite membrane 12. The impermeable substance recovered by the first recovery unit 27 may be circulated, for example, to the supply unit 26 and supplied again into the housing 22.

[0069] Next, Examples 1-5 and Comparative Examples 1-3 of the zeolite membrane composite will be described.

[0070] (Preparation of seed crystal-attached support) A porous alumina support having a multilayer structure was prepared in the same manner as the manufacturing method described in International Publication No. 2017 / 169591 (reference 4 above). Seed crystals, which are DDR-type zeolite crystal powder, were prepared in the same manner as the manufacturing method described in Japanese Patent Application Publication No. 2004-83375 (reference 5 above). Subsequently, the alumina support was brought into contact with a solution in which the seed crystals were dispersed, and the seed crystals were attached to the alumina support.

[0071] (Preparation of raw material solution) After adding distilled water [a]g to a wide-mouthed fluororesin bottle, a raw material solution for film formation was prepared by adding 1-adamantanamine (1-ADA, manufactured by Sigma-Aldrich) [b]g, sodium hydroxide (NaOH, manufactured by Sigma-Aldrich) [c]g, 30% by weight silica sol (product name: Snowtex S, manufactured by Nissan Chemical Corporation) [d]g, sodium aluminate (manufactured by Wako Pure Chemical Industries, Ltd.) [e]g, and boehmite powder (AlO(OH)₂, product name: C20, manufactured by Daimyo Chemical Co., Ltd.) [f]g and stirring. The masses a to f of the above raw materials in Examples 1 to 5 and Comparative Examples 1 to 3 are as shown in Table 1.

[0072] [Table 1]

[0073] (Synthesis of zeolite films) A DDR-type zeolite film was formed by placing an alumina support inside a fluororesin inner cylinder (internal volume 300 ml) of a stainless steel pressure vessel, then adding the prepared raw material solution and performing a heat treatment (hydrothermal synthesis). In the hydrothermal synthesis, the film was held at 130°C for [g] hours, and then at 150°C for [h] hours. The holding times g and h at each temperature for Examples 1-5 and Comparative Examples 1-3 are shown in Table 1. Next, the alumina support was washed and dried at 80°C for 12 hours or more. Subsequently, the alumina support was heated to 450°C in an electric furnace and held for 50 hours to burn off 1-adamantanamine. Through the above treatment, zeolite film composites having a DDR-type zeolite film were obtained for Examples 1-5 and Comparative Examples 1-3.

[0074] (Si / Al ratio measurement) Using X-ray photoelectron spectroscopy (XPS), depth-direction compositional analysis was performed on zeolite films after cleaning (1 nm sputtering to remove surface contamination layer) to determine the change in Si / Al ratio in the thickness direction. The measurement conditions were: X-ray source: monochromatic AlKα rays (1486.6 eV), X-ray beam diameter: 100 μm, photoelectron extraction angle: 45° relative to the normal to the sample, sputtering: Ar monomer ions. The sputtering pitch, acceleration voltage, sputtering velocity, and sputtering endpoint during cleaning and measurement are as shown in Table 2. Note that the sputtering velocity and depth are values ​​converted to SiO2 equivalent.

[0075] [Table 2]

[0076] Figures 8A to 8E show the measurement results of the Si / Al ratio for the zeolite film composites of Examples 1 to 5, and Figures 9A to 9C show the measurement results of the Si / Al ratio for the zeolite film composites of Comparative Examples 1 to 3. Figures 8A to 8E and 9A to 9C show the change in the Si / Al ratio in the thickness direction. The Si / Al ratio of the surface is indicated by a white triangle, and the position of the interface (here, the position where the Si / Al ratio is less than 1) is indicated by a black triangle. Table 3 shows the Si / Al ratio of the surface, the ratio of the length La of the high Si / Al ratio range to the thickness T of the zeolite film 12 (La / T), the maximum Si / Al ratio, and the ratio of the length Lb of the interface-side area of ​​interest to the thickness T of the zeolite film 12 (Lb / T) for the zeolite film composites of Examples 1 to 5 and Comparative Examples 1 to 3 (see Figure 3). These values ​​were obtained from Figures 8A to 8E and 9A to 9C. Furthermore, in the case of changes in the Si / Al ratio in the thickness direction, the range in the thickness direction where the Si / Al ratio is less than 1 was considered to be an alumina support. If the support is not alumina, the interface is defined as the point where the molar ratio of Si / (total amount of elements other than oxygen constituting the support) is less than 1.

[0077] [Table 3]

[0078] In the zeolite film composites of Examples 1 to 5, as shown in Figures 8A to 8E, the Si / Al ratio increased from the interface towards the interior of the film, and decreased from the interior towards the surface. On the other hand, in the zeolite film composites of Comparative Examples 1 and 2, as shown in Figures 9A and 9B, the Si / Al ratio at the surface was greater than that at the interior of the film. Furthermore, in the zeolite film composite of Comparative Example 3, as shown in Figure 9C, the Si / Al ratio at the interface was the same as that at the interior of the film.

[0079] (Membrane performance evaluation) Using the above separation device 2, a water-ethanol mixture (mass ratio 50:50) was separated by pervaporation at a temperature of 60°C, and the permeation amount of the liquid recovered in the second recovery section 28 was measured. The density of the liquid was determined using a density hydrometer, and the water / ethanol amount ratio was measured. Then, the water permeation flux and separation factor were determined from the permeation amount of the liquid and the water / ethanol amount ratio. The separation factor is the value obtained by dividing the water concentration (mass%) by the ethanol concentration. In Table 3, when the water permeation flux is 2.5 kg / m 2 h or more, the evaluation is "○", and when it is less than 2.5 kg / m 2 h and 2.0 kg / m 2 h or more, the evaluation is "△", and when it is less than 2.0 kg / m 2 h, the evaluation is "×".

[0080] In the zeolite membrane composites of Examples 1 to 5 and Comparative Examples 2 and 3, the water permeation flux was 2.0 kg / m 2 h or more, and a high water permeation flux was obtained. In particular, in the zeolite membrane composites of Examples 1, 2, 4, 5 and Comparative Examples 2 and 3 where the Si / Al ratio of the surface part is 120 or less, the water permeation flux was 2.5 kg / m 2 h or more. In Comparative Example 1, the water permeation flux was low (less than 2.0 kg / m 2 h).

[0081] (Hydrothermal resistance evaluation) In the water and heat resistance evaluation, the vacuum level was measured using the housing 22 containing the zeolite membrane composite 1, as in Figure 6. For the vacuum level measurement, as shown in Figure 10, a vacuum pump 291 (ULVAC KIKO, Inc.: direct-drive oil rotary vacuum pump, model number: G-20DA, pumping speed 24 L / min, ultimate pressure 1.3 Pa, two-stage) was connected to port 221, one end of the housing 22 in the longitudinal direction, and vacuum was drawn. A vacuum gauge 292 (GE Sensing: calibrator, model number: DPI800) was connected to port 222, the other end of the housing 22, and the ultimate vacuum level was measured. At this time, port 223, located on the side of the housing 22, was opened to the atmosphere. Next, the zeolite membrane composite removed from the housing 22 was immersed in high-temperature water (180°C) for 12 hours, washed with deionized water, and dried at room temperature for at least 12 hours. Subsequently, the vacuum level was measured again, and the ratio of the vacuum level after immersion to the vacuum level before immersion (hereinafter referred to as the "ratio of vacuum levels before and after immersion") was used as an indicator of water and heat resistance. In Table 3, a rating of "○" was given if the ratio of vacuum levels before and after immersion was 95% or higher, a rating of "△" was given if it was less than 95% but 90% or higher, and a rating of "×" was given if it was less than 90%.

[0082] In the zeolite membrane composites of Examples 1-5 and Comparative Examples 1 and 3, the ratio of vacuum levels before and after immersion was 90% or higher, indicating high water-heat resistance. In particular, in the zeolite membrane composites of Examples 1-3 and Comparative Example 3, where the ratio of length La (La / T) in the high Si / Al ratio range was 25% or higher and the maximum Si / Al ratio was 180 or higher, the ratio of vacuum levels before and after immersion was 95% or higher. In Comparative Example 2, the ratio of vacuum levels before and after immersion was less than 90%, indicating low water-heat resistance.

[0083] (Evaluation of adhesion) Adhesive tape specified in JIS Z 1522 was applied to the surface of the zeolite film, and the surface of the zeolite film after the adhesive tape was removed was observed using a scanning electron microscope (SEM). In Table 3, a "○" rating was given when no film peeling was observed, a "△" rating was given when minute film peeling with a maximum width of less than 10 μm was observed, and a "×" rating was given when large film peeling with a maximum width of 10 μm or more was observed.

[0084] In the zeolite film composites of Examples 1-5 and Comparative Examples 1 and 2, no significant delamination was observed, and zeolite films with improved adhesion were obtained. Furthermore, in the zeolite film composites of Examples 1, 3-5 and Comparative Examples 1 and 2, where the ratio of the length Lb of the interface area of ​​interest (Lb / T) was 30% or more, no delamination occurred at all. In Comparative Example 3, significant delamination was observed, indicating poor adhesion.

[0085] As described above, the zeolite membrane composite 1 comprises a porous support 11 and a zeolite membrane 12 provided on the support 11. In the zeolite membrane 12, the molar ratio of Si / Al increases from the interface 121 with the support 11 toward the interior of the membrane, and decreases from the interior of the membrane toward the surface 122 opposite to the support 11. As a result, as in Examples 1 to 5 above, a zeolite membrane composite 1 with high water permeation flux and hydrothermal resistance and suppressed membrane delamination can be realized.

[0086] Preferably, in the thickness direction of the Si / Al ratio in the zeolite film 12, the length of the range where the Si / Al ratio is twice or more that of the surface portion 122 is 25% or more of the length of the zeolite film 12. In this way, by including a large amount of zeolite with a high Si / Al ratio in the zeolite film 12, the water and heat resistance of the zeolite film 12 can be improved more reliably.

[0087] Preferably, in the zeolite film 12, the maximum Si / Al ratio is 180 or higher as the Si / Al ratio changes in the thickness direction. In this way, by including zeolite with a sufficiently large Si / Al ratio in the zeolite film 12, the water and heat resistance of the zeolite film 12 can be further improved.

[0088] Preferably, the Si / Al ratio at the surface portion 122 of the zeolite film 12 is 120 or less. This increases the hydrophilicity of the surface portion 122, thereby more reliably improving the water permeation flux.

[0089] Preferably, in the thickness direction of the Si / Al ratio in the zeolite film 12, the length of the range between the first position where the Si / Al ratio becomes half of the maximum Si / Al ratio of the zeolite film 12 as you move from the interface 121 towards the interior of the film, and the support 11, is 25% or more of the length of the thickness of the zeolite film 12. In this way, by having a low Si / Al ratio over a wide area near the interface 121, film delamination can be more reliably suppressed and the adhesion of the zeolite film 12 can be improved.

[0090] Furthermore, it is preferable that the zeolite constituting the zeolite membrane 12 is an 8-membered ring zeolite. This allows for the selective permeation of a target substance with a relatively small molecular diameter (especially water) to be effectively achieved in the zeolite membrane composite 1.

[0091] Here, we will describe a comparative example of a method for manufacturing a zeolite membrane composite. In the comparative example's manufacturing method, a multilayer zeolite membrane is formed. Specifically, a first zeolite layer with a small Si / Al ratio is formed on a support using one raw material solution, a second zeolite layer with a large Si / Al ratio is formed on the first zeolite layer using another raw material solution, and a third zeolite layer with a small Si / Al ratio is formed on the second zeolite layer using yet another raw material solution. This results in a multilayer zeolite membrane with a small Si / Al ratio at the interface and surface. In a multilayer zeolite membrane, the Si / Al ratio is discontinuous at the boundaries of adjacent zeolite layers. In the comparative example's manufacturing method, the formation of zeolite layers is repeated, which results in a long time required for the production of the zeolite membrane composite.

[0092] In contrast, the method for producing the zeolite membrane composite 1 described above comprises the steps of: preparing a raw material solution by mixing a Si source and two types of Al sources with different solubility in water with water (step S13); immersing a porous support 11 in the raw material solution (step S14); and heating the raw material solution to form a zeolite membrane 12 on the support 11 (step S15). In step S15, hydrothermal synthesis is performed at a temperature in which almost all of one of the two types of Al sources contained in the raw material solution dissolves, and at least a portion of the other Al source does not dissolve, and then hydrothermal synthesis is performed at a temperature higher than that temperature. As a result, the zeolite membrane 12 with a small Si / Al ratio at the interface 121 and surface 122 can be easily formed without repeating the formation of a zeolite layer as in the comparative example, and the zeolite membrane composite 1 can be efficiently produced.

[0093] The separation method described above comprises the steps of preparing a zeolite membrane composite 1 (step S21) and supplying a mixed substance containing multiple types of gases or liquids to the zeolite membrane composite 1, and separating a substance with high permeability in the mixed substance from other substances by allowing it to pass through the zeolite membrane composite 1 (step S22). In this separation method, by using a zeolite membrane composite 1 with high water permeation flux and hydrothermal resistance and suppressed membrane peeling, various mixed substances can be separated efficiently and stably. The separation method using the zeolite membrane composite 1 is particularly suitable for separating mixed substances containing water.

[0094] Various modifications are possible to the zeolite membrane composite 1, the method for producing the zeolite membrane composite 1, and the separation method described above.

[0095] If a zeolite film composite 1 with high water permeation flux and hydrothermal resistance, and suppressed film delamination is realized, then the ratio of length La in the high Si / Al ratio range (La / T) in the zeolite film 12 may be less than 25%, and the maximum Si / Al ratio may be less than 180. Similarly, the Si / Al ratio of the surface portion 122 may be greater than 120, and the ratio of length Lb in the interface-side area of ​​interest (Lb / T) may be less than 25%.

[0096] The maximum number of rings in the zeolite constituting the zeolite film 12 may be less than 8 or greater than 8.

[0097] In addition to the support 11 and the zeolite film 12, the zeolite film composite 1 may further include a functional film or protective film laminated on the zeolite film 12. Such a functional film or protective film may be an inorganic film such as a zeolite film, silica film, or carbon film, or an organic film such as a polyimide film or silicone film. Furthermore, the functional film or protective film laminated on the zeolite film 12 may have a substance added that readily adsorbs water.

[0098] In the manufacturing process of the zeolite membrane composite 1 shown in Figure 4, the steps of attaching seed crystals to the support 11 (steps S11 and S12) can be omitted, and the zeolite membrane 12 can be directly formed on the support 11 in step S15. The zeolite membrane composite 1 may also be manufactured by methods other than the manufacturing method shown in Figure 4.

[0099] In addition to the permeation vaporization method exemplified above, the separation of the mixed substances may also be carried out by vapor permeation, reverse osmosis, gas permeation, etc. Furthermore, substances other than those exemplified above may be separated from the mixed substances.

[0100] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other.

[0101] Although the invention has been described in detail, the above description is illustrative and not limiting. Therefore, it can be said that numerous modifications and embodiments are possible as long as they do not deviate from the scope of the present invention. [Industrial applicability]

[0102] The zeolite membrane composite of the present invention can be used, for example, as a dehydration membrane, and furthermore, it can be used in various fields where zeolites are utilized, such as as a separation membrane for various substances other than water, or as an adsorption membrane for various substances. [Explanation of Symbols]

[0103] 1. Zeolite membrane complex 11 Support 12 Zeolite membrane 121 Interface part 122 Surface part S11~S15, S21, S22 Step

Claims

1. A zeolite membrane composite, A porous support, A zeolite film provided on the support, Equipped with, In the zeolite film, the molar ratio of Si / Al increases from the interface with the support toward the interior of the film, and decreases from the interior of the film toward the surface opposite the support.

2. A zeolite membrane composite according to claim 1, In the zeolite film, the length of the range in the thickness direction where the Si / Al ratio is twice or more the Si / Al ratio of the surface portion is 25% or more of the length of the zeolite film.

3. A zeolite membrane composite according to claim 1, In the zeolite film, the maximum Si / Al ratio is 180 or higher as the Si / Al ratio changes in the thickness direction.

4. A zeolite membrane composite according to claim 1, The Si / Al ratio on the surface portion of the zeolite film is 120 or less.

5. A zeolite membrane composite according to claim 1, In the thickness direction change of the Si / Al ratio in the zeolite film, the length of the range in the thickness direction between the first position where the Si / Al ratio becomes half of the maximum Si / Al ratio of the zeolite film as you move from the interface towards the interior of the film, and the support, is 25% or more of the thickness of the zeolite film.

6. A zeolite membrane composite according to claim 1, The zeolite constituting the zeolite membrane is an eight-membered ring zeolite.

7. A method for producing a zeolite membrane composite, a) A step of preparing a raw material solution by mixing a Si source and two types of Al sources with different solubility in water with water, b) A step of immersing a porous support in the raw material solution, c) A step of heating the raw material solution to form a zeolite film on the support, Equipped with, In step c) above, hydrothermal synthesis is performed at a temperature in which substantially all of one of the two types of Al sources contained in the raw material solution dissolves, and at least a portion of the other Al source does not dissolve, and thereafter, hydrothermal synthesis is performed at a temperature higher than the above temperature.

8. A separation method, a) A step of preparing a zeolite membrane composite according to any one of claims 1 to 6, b) A step of supplying a mixed substance containing multiple types of gases or liquids to the zeolite membrane composite, and separating a substance with high permeability in the mixed substance from other substances by allowing it to pass through the zeolite membrane composite, It is equipped with.

Images