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

Abstract

A zeolite membrane composite body (1)is provided with a porous supporting body (11) and a zeolite membrane (12) which is arranged on the supporting body (11) and is formed of LTA zeolite. If the Si / Al molar ratio in the zeolite membrane (12) is 1.74 to 2.80, the zeolite membrane composite body (1) can have improved hydrothermal durability. If the Si / Al molar ratio in the zeolite membrane (12) is 1.2 or more, and at least one of the intensity of a peak that is present around 2θ = 24.0° and the intensity of a peak that is present around 2θ = 30.0° is not less than 0.85 times the intensity of a peak that is present around 2θ = 7.2° in the X-ray diffraction pattern obtained by irradiating the surface of the zeolite membrane (12) with an X-ray, the zeolite membrane composite body (1) can have improved strength.

Description

[Technical Field]

[0001] The present invention relates to a zeolite membrane composite, a membrane reactor, and a method for producing a zeolite membrane composite. [Reference to Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2021-184979, filed on November 12, 2021, the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002] Zeolite membranes have traditionally been used as separation membranes that utilize molecular sieving. Zeolite membranes are usually provided on a porous support and treated as zeolite membrane composites. For example, Japanese Patent Laid-Open Publication No. 7-185275 (Document 1) discloses a separation membrane in which a zeolite membrane having an LTA-type crystal structure (A-type zeolite membrane) is formed on a porous support. The publication describes that the zeolite membrane is formed by hydrothermal synthesis, and that the raw material composition ratios are adjusted to a SiO2 / Al2O3 molar ratio of 2 to 6, a HO / Na2O molar ratio of 20 to 300, and a Na2O / SiO2 molar ratio of 0.3 to 2.

[0003] International Publication No. 2020 / 261795 (Reference 2) describes the problem that the Si / Al ratio of LTA zeolite membranes is typically approximately 1, which is insufficient in terms of thermal stability and hydrothermal stability, and describes the production of LTA zeolite membranes with Si / Al ratios of 1.29 to 1.60. Reference 2 also describes that LTA zeolite membranes with a Si / Al ratio of 1.70 become brittle. "Framework stabilization of Si-rich LTA zeolite prepared in organic-free media" (Chem. Commun., 2015, Vol. 51, pp. 269-272) (Reference 3) by Marlon T. Conato and four others describes the synthesis of LTA zeolite powder with a Si / Al ratio of 1.7 to 2.1. "Synthesis and Characterization of A-Type Zeolites" (ACS Symposium Series, American Chemical Society, 1983, Vol. 218, pp. 267-281) (Reference 4) by RH JARMAN and two others describes the synthesis of LTA-type zeolite powder with a Si / Al ratio of 1.16 to 2.99.

[0004] As mentioned above, in Literature 2, the hydrothermal durability (hydrothermal stability) of an LTA zeolite membrane is improved by adjusting the Si / Al ratio to 1.29 to 1.60, but this is not necessarily sufficient. Furthermore, if the Si / Al ratio of the LTA zeolite membrane is increased, the strength of the zeolite membrane composite decreases, which becomes a practical problem. Therefore, there is a demand for a zeolite membrane composite with improved hydrothermal durability and / or strength. Summary of the Invention

[0005] The present invention is directed to a zeolite membrane composite, and aims to provide a zeolite membrane composite having improved hydrothermal durability and / or strength.

[0006] A first aspect of the invention is a zeolite membrane composite, comprising a porous support and a zeolite membrane formed on the support and made of LTA zeolite, wherein the zeolite membrane has a Si / Al molar ratio of 1.74 or more and 2.80 or less.

[0007] This makes it possible to provide a zeolite membrane composite with improved hydrothermal durability.

[0008] A second aspect of the invention is the zeolite membrane composite of the first aspect, wherein in an X-ray diffraction pattern obtained by irradiating the surface of the zeolite membrane with X-rays, at least one of the intensity of a peak present near 2θ=24.0° and the intensity of a peak present near 2θ=30.0° is 0.85 times or more the intensity of a peak present near 2θ=7.2°.

[0009] A third aspect of the invention is a zeolite membrane composite comprising a porous support and a zeolite membrane formed on the support and made of LTA zeolite, wherein the zeolite membrane has a Si / Al molar ratio of 1.2 or more, and an X-ray diffraction pattern obtained by irradiating the surface of the zeolite membrane with X-rays has a peak intensity near 2θ=24.0° and a peak intensity near 2θ=30.0° that is 0.85 times or more the peak intensity near 2θ=7.2°.

[0010] This makes it possible to provide a zeolite membrane composite with improved strength.

[0011] A fourth aspect of the invention is the zeolite membrane composite of any one of the first to third aspects, wherein the zeolite membrane has a thickness of 5 μm or less.

[0012] A fifth aspect of the invention is the zeolite membrane composite of any one of the first to fourth aspects, wherein the total permeation flux is 2.0 kg / m when a mixed liquid containing 50 mass % of water and 50 mass % of ethanol at 60°C is supplied to the permeation side at -94.66 kPaG. 2h or more, and the separation factor between water and ethanol is 2000 or more.

[0013] The present invention is also directed to a membrane reactor. A sixth aspect of the present invention is a membrane reactor comprising the zeolite membrane composite of any one of the first to fifth aspects, a catalyst for promoting a chemical reaction of a raw material, a reactor containing the zeolite membrane composite and the catalyst, and a supply unit for supplying the raw material to the reactor. The zeolite membrane composite separates a highly permeable substance from other substances by passing it through the mixed substance containing a product produced by the chemical reaction of the raw material in the presence of the catalyst.

[0014] The present invention is also directed to a method for producing a zeolite composite membrane. A seventh aspect of the invention is a method for producing a zeolite composite membrane, comprising: (a) preparing a raw material solution by mixing a sodium source, an aluminum source, and a silicon source with water; (b) stirring the raw material solution for 10 hours or more after the step (a); (c) immersing a porous support having seed crystals containing LTA zeolite attached thereto in the raw material solution; and (d) heating the raw material solution 70 minutes or more after the end of the step (b), thereby forming a zeolite membrane made of LTA zeolite on the support having the seed crystals attached thereto. In the raw material solution, the SiO / AlO molar ratio is 4 to 7, the HO / NaO molar ratio is 100 to 1200, and the NaO / SiO molar ratio is 0.1 to 0.6.

[0015] An eighth aspect of the invention is the method for producing the zeolite composite membrane according to the seventh aspect, wherein the raw material solution has a molar ratio of H2O / Na2O of 350 or more.

[0016] A ninth aspect of the invention is the method for producing the zeolite composite membrane according to the seventh or eighth aspect, wherein the Si / Al molar ratio of the seed crystals is 2.4 or more.

[0017] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view of a zeolite membrane composite. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a part of the zeolite composite membrane. [Figure 3] FIG. 1 shows an X-ray diffraction pattern obtained from the surface of a zeolite membrane. [Figure 4] FIG. 1 is a diagram showing a flow of manufacturing a zeolite membrane composite. [Figure 5] FIG. [Figure 6] FIG. 1 is a diagram showing the flow of separation of a mixed substance. DETAILED DESCRIPTION OF THE INVENTION

[0019] FIG. 1 is a cross-sectional view of a zeolite membrane composite 1. FIG. 2 is an enlarged cross-sectional view of a portion of the zeolite membrane composite 1. The zeolite membrane composite 1 includes a porous support 11 and a zeolite membrane 12 provided on the support 11. The zeolite membrane refers to at least a zeolite membrane formed on the surface of the support 11, and does not include a membrane in which zeolite particles are simply dispersed in an organic film. In FIG. 1, the zeolite membrane 12 is depicted with a thick line. In FIG. 2, the zeolite membrane 12 is depicted with parallel diagonal lines. Furthermore, in FIG. 2, the thickness of the zeolite membrane 12 is depicted thicker than it actually is.

[0020] The support 11 is a porous member that is permeable to gases and liquids. In the example shown in FIG. 1, the support 11 is a monolithic support having a single, continuous columnar body formed integrally with the support 11, and multiple through-holes 111 extending in the longitudinal direction (i.e., the left-right direction in FIG. 1) are provided in the support 11. In the example shown in FIG. 1, the support 11 is substantially cylindrical. The cross section perpendicular to the longitudinal direction of each through-hole 111 (i.e., cell) is, for example, substantially circular. In FIG. 1, the diameter of the through-holes 111 is drawn larger than in reality, and the number of through-holes 111 is drawn smaller than in reality. The zeolite membrane 12 is formed on the inner circumferential surfaces of the through-holes 111, covering the inner circumferential surfaces of the through-holes 111 over substantially the entire surfaces.

[0021] The length of the support 11 (i.e., the length in the left-right direction in FIG. 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, and preferably 0.2 μm to 2.0 μm. The shape of the support 11 may be, for example, a honeycomb shape, a flat plate shape, a tubular shape, a cylindrical shape, a columnar shape, or a polygonal pillar shape. When 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.

[0022] The material of the support 11 can be various substances (for example, ceramic or metal) as long as they are chemically stable in the process of forming the zeolite membrane 12 on the surface. In this embodiment, the support 11 is formed of a ceramic sintered body. Examples of ceramic sintered bodies that can be selected as the material of the support 11 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, the support 11 contains at least one of alumina, silica, and mullite.

[0023] The support 11 may contain an inorganic binder, which may be at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite.

[0024] The average pore size of the support 11 is, for example, 0.01 μm to 70 μm, and preferably 0.05 μm to 25 μm. The average pore size of the support 11 near the surface on which the zeolite membrane 12 is formed is 0.01 μm to 1 μm, and preferably 0.05 μm to 0.5 μm. The average pore size can be measured, for example, by a mercury porosimeter, a perm porometer, or a nanoperm porometer. Regarding the pore size distribution 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 on which the zeolite membrane 12 is formed is, for example, 20% to 60%.

[0025] The support 11 has, for example, a multilayer structure in which multiple layers with different average pore sizes are stacked in the thickness direction. The average pore size and sintered particle size in the surface layer, including the surface on which the zeolite membrane 12 is formed, are smaller than the average pore size and sintered particle size in the layers other than the surface layer. The average pore size in the surface layer of the support 11 is, for example, 0.01 μm to 1 μm, and preferably 0.05 μm to 0.5 μm. When the support 11 has a multilayer structure, the materials described above can be used for each layer. The materials of the multiple layers forming the multilayer structure may be the same or different.

[0026] The zeolite membrane 12 is a porous membrane having fine pores (micropores). The zeolite membrane 12 can be used as a separation membrane that separates a specific substance from a mixture of multiple substances by utilizing molecular sieving action. The zeolite membrane 12 is less permeable to other substances than to the specific substance. In other words, the amount of the other substances that permeates the zeolite membrane 12 is smaller than the amount of the specific substance that permeates the zeolite membrane 12.

[0027] The thickness of the zeolite membrane 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. Since a thinner zeolite membrane 12 increases the permeation rate, the thickness of the zeolite membrane 12 is more preferably 5 μm or less. On the other hand, a thicker zeolite membrane 12 improves separation performance. The surface roughness (Ra) of the zeolite membrane 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. The thickness and surface roughness of the zeolite membrane 12 can be obtained by observing a cross section of the zeolite membrane 12 using a scanning electron microscope (SEM).

[0028] The zeolite membrane 12 is composed of zeolite with an LTA structure. In other words, the zeolite membrane 12 is made of zeolite with the structure code "LTA" defined by the International Zeolite Association. The X-ray diffraction pattern obtained from the surface of the zeolite membrane 12, as shown in FIG. 3 (described later), has peak positions that match those of the X-ray diffraction pattern expected from the structure of LTA zeolite. The zeolite membrane 12 is typically composed only of LTA zeolite, but depending on the production method, the zeolite membrane 12 may contain small amounts (for example, 1 mass % or less) of substances other than LTA zeolite.

[0029] The maximum number of ring members in LTA zeolite is 8. An 8-ring pore is a micropore in which the number of oxygen atoms in the ring structure formed by bonding with a T atom (described later) is 8. The intrinsic pore diameter of LTA zeolite is 0.41 nm. The pore diameter of the zeolite membrane 12 is smaller than the average pore diameter of the support 11 in the vicinity of the surface on which the zeolite membrane 12 is formed.

[0030] An example of the LTA-type zeolite constituting the zeolite membrane 12 is an aluminosilicate zeolite in which the atom (T atom) located at the center of the oxygen tetrahedron (TO4) constituting the zeolite is composed of silicon (Si) and aluminum (Al). Some of the T atoms may be substituted with other elements (Ti, B, P, etc.). This allows the pore size and adsorption characteristics to be changed.

[0031] The Si / Al molar ratio (the value obtained by dividing the number of moles of Si atoms by the number of moles of Al atoms; the same applies hereinafter) in the zeolite membrane 12 is 1.2 or more. This allows the hydrothermal durability of the zeolite membrane 12 to be improved to a certain extent. As will be described later, the hydrothermal durability can be evaluated by the degree of deterioration in separation performance before and after immersion of the zeolite membrane composite 1 in heated water. From the viewpoint of further improving the hydrothermal durability, the Si / Al molar ratio is preferably 1.74 or more, more preferably 1.85 or more, and even more preferably 2.0 or more. If the Si / Al molar ratio is greater than 2.80, it becomes difficult to form a dense membrane. Therefore, the Si / Al molar ratio is preferably 2.80 or less. The Si / Al molar ratio in the zeolite membrane 12 can be adjusted by adjusting the blending ratios in the raw material solution, which will be described later (the same applies to the ratios of other elements). The Si / Al molar ratio can be measured by EDS (energy dispersive X-ray spectroscopy) analysis of a cross section of the zeolite membrane 12.

[0032] Typically, the zeolite membrane 12 contains an alkali metal. The alkali metal is, for example, sodium (Na). The zeolite membrane 12 may contain other alkali metals. In one example of manufacturing the zeolite membrane 12, an organic substance called a structure-directing agent (hereinafter also referred to as "SDA") is not used. The zeolite membrane 12 may be manufactured using an SDA. In this case, it is preferable that the SDA is almost or completely removed after the formation of the zeolite membrane 12. This ensures that the pores in the zeolite membrane 12 are properly maintained. The SDA is, for example, tetramethylammonium hydroxide.

[0033] Fig. 3 is a diagram showing an example of an X-ray diffraction (XRD) pattern obtained by irradiating the surface of the zeolite membrane 12 with X-rays. The X-ray diffraction pattern in Fig. 3 is obtained using CuKα radiation as the radiation source of an X-ray diffractometer. As described above, the peak positions of the X-ray diffraction pattern obtained from the zeolite membrane 12 coincide with those of the X-ray diffraction pattern expected from the structure of LTA zeolite.

[0034] In the zeolite membrane 12, in the X-ray diffraction pattern, at least one of the peak intensities near 2θ (diffraction angle) = 24.0° and the peak intensities near 2θ = 30.0° (preferably both) is, for example, 0.85 times or more the intensity of the peak near 2θ = 7.2°. The peak near 2θ = 24.0° is a peak present in the range of 2θ = 24.0° ± 0.5° and is derived from the (622) plane of LTA zeolite. The peak near 2θ = 30.0° is a peak present in the range of 2θ = 30.0° ± 0.5° and is derived from the (820) or (644) plane. The peak near 2θ = 7.2° is a peak present in the range of 2θ = 7.2° ± 0.5° and is derived from the (200) plane.

[0035] For example, in Figure 6 of International Publication No. 2020 / 261795 (the above-mentioned Document 2), in the X-ray diffraction pattern of the LTA zeolite membrane, both the intensity of the peak near 2θ = 24.0 ° and the intensity of the peak near 2θ = 30.0 ° are less than 0.85 times (actually, about 0.8 times) the intensity of the peak near 2θ = 7.2 °. In other words, in the LTA zeolite membrane of Document 2, the intensity of the peak near 2θ = 7.2 ° is relatively large, and it is thought that the zeolite crystals grow in an oriented manner. Therefore, as the Si / Al molar ratio increases, the zeolite membrane tends to become brittle and its strength decreases.

[0036] In contrast, in a zeolite membrane 12 in which at least one of the peak intensities near 2θ=24.0° and 2θ=30.0° is 0.85 times or more the peak intensity near 2θ=7.2°, the peak intensity near 2θ=7.2° is relatively small, suggesting that the zeolite crystals grow randomly without orientation. Therefore, even if the Si / Al molar ratio increases, the zeolite membrane 12 is less likely to become brittle and maintains a certain level of strength. The strength of the zeolite membrane 12 can be evaluated by the degree of deterioration in separation performance before and after a hydraulic pressure test, which will be described later.

[0037] To ensure the strength of the zeolite membrane 12, the peak intensity near 2θ=24.0° is preferably at least 0.90 times, and more preferably at least 0.95 times, the peak intensity near 2θ=7.2°. The same applies to the peak intensity near 2θ=30.0°. Typically, the peak intensity near 2θ=24.0° is not excessively large compared to the peak intensity near 2θ=7.2°. For example, the peak intensity near 2θ=24.0° is no more than three times the peak intensity near 2θ=7.2°. The same applies to the peak intensity near 2θ=30.0°. The peak intensity is measured using the bottom line in the X-ray diffraction pattern, i.e., the height excluding background noise components. The bottom line in the X-ray diffraction pattern can be determined, for example, by the Sonneveld-Visser method or spline interpolation.

[0038] Next, with reference to FIG. 4 , an example of a flow of manufacturing the zeolite membrane composite 1 will be described. When manufacturing the zeolite membrane composite 1, seed crystals to be used in manufacturing the zeolite membrane 12 are first prepared (step S11). For example, LTA zeolite powder is produced by hydrothermal synthesis, and the seed crystals are obtained from the zeolite powder. The LTA zeolite powder may be produced by any or known manufacturing method. In one example, the LTA zeolite powder is produced by hydrothermal synthesis of a solution similar to the raw material solution described below. When the solution contains SDA, the SDA in the powder is almost completely burned and removed by heat treatment of the zeolite powder. The zeolite powder may be used as is as the seed crystals, or the seed crystals may be obtained by processing the powder by pulverization or the like. To more reliably manufacture a zeolite membrane composite 1 having improved hydrothermal durability and / or strength, it is preferable that the Si / Al molar ratio of the seed crystals is relatively large, for example, 2.4 or more. The upper limit of the Si / Al molar ratio of the seed crystal is not particularly limited, but is 5, for example.

[0039] Next, the porous support 11 is immersed in the dispersion liquid in which the seed crystals are dispersed, and the seed crystals are attached to the support 11 (step S12). Alternatively, the dispersion liquid in which the seed crystals are dispersed is brought into contact with the portion of the support 11 where the zeolite membrane 12 is to be formed, thereby attaching the seed crystals to the support 11. In this way, a seed crystal-attached support is produced. The seed crystals may also be attached to the support 11 by other methods.

[0040] A raw material solution used to produce the zeolite membrane 12 is prepared (step S13). The raw material solution is prepared, for example, by mixing a Si source, an Al source, and a Na source in water (HO). Examples of the Si source include colloidal silica, fumed silica, tetraethoxysilane, and sodium silicate. Examples of the Al source include sodium aluminate, aluminum isopropoxide, aluminum hydroxide, boehmite, sodium aluminate, and alumina sol. Examples of the Na source include sodium hydroxide, sodium aluminate, sodium chloride, and sodium silicate. The raw material solution may contain SDA. Examples of SDA include tetramethylammonium hydroxide, tetramethylammonium chloride, tetramethylammonium bromide, and diethyldimethylammonium hydroxide.

[0041] In the raw material solution, when it is assumed that the Si source is entirely present as SiO2 and the Al source is entirely present as Al2O3, the molar ratio of SiO2 / Al2O3 is preferably 4 to 7. When it is assumed that the Na source is entirely present as Na2O, the molar ratio of H2O / Na2O is preferably 100 to 1200. To ensure a high molar ratio of Si / Al in the zeolite membrane 12, the molar ratio of H2O / Na2O is preferably 350 or more. The molar ratio of H2O / Na2O may be 550 or more. The molar ratio of Na2O / SiO2 is preferably 0.1 to 0.6. The molar ratio of SDA / Al2O3 is preferably 0 to 2. Other raw materials may be mixed into the raw material solution.

[0042] After preparation of the raw material solution, the raw material solution is stirred for 10 hours or more (step S14). The stirring of the raw material solution may be performed by various well-known methods. The temperature of the raw material solution during stirring is lower than the temperature during hydrothermal synthesis described below, for example, 0 to 60°C, and preferably 5 to 50°C. Typically, the temperature of the raw material solution during stirring is room temperature. The upper limit of the stirring time is not particularly limited, but is, for example, 100 hours.

[0043] At least 70 minutes after the end of stirring the raw material solution, the support 11 to which the seed crystals are attached is immersed in the raw material solution (step S15). Thereafter, the raw material solution is heated to initiate hydrothermal synthesis. In the hydrothermal synthesis, LTA-type zeolite grows using the seed crystals as nuclei, and an LTA-type zeolite membrane 12 is formed on the support 11 (step S16). The synthesis temperature during the hydrothermal synthesis (the heating temperature of the raw material solution) is, for example, 65 to 150°C, and preferably 70 to 120°C. The hydrothermal synthesis time is, for example, 5 to 200 hours, and preferably 10 to 150 hours. The support 11 may be immersed in the raw material solution in step S15 before 70 minutes have elapsed since the end of stirring the raw material solution. In this case, heating of the raw material solution, i.e., formation of the zeolite membrane 12, is initiated 70 minutes or more after the end of stirring. The upper limit of the time from the end of stirring to the start of heating the raw material solution is not particularly limited, but is, for example, 1000 minutes.

[0044] After the hydrothermal synthesis is completed, the support 11 and the zeolite membrane 12 are washed with pure water. The washed support 11 and the zeolite membrane 12 are dried, for example, at 80°C. When the raw material solution contains SDA, the support 11 and the zeolite membrane 12 are dried, and then the zeolite membrane 12 is heat-treated in an oxidizing gas atmosphere to burn and remove the SDA in the zeolite membrane 12. This penetrates the micropores in the zeolite membrane 12. Preferably, the SDA is almost completely removed. The heating temperature for removing the SDA is, for example, 300 to 600°C. The heating time is, for example, 1 to 100 hours. The oxidizing gas atmosphere is an atmosphere containing oxygen, such as air. When the raw material solution does not contain SDA, the heat treatment is not performed. Through the above treatments, the above-mentioned zeolite membrane composite 1 is obtained.

[0045] Next, separation of a mixed substance using the zeolite membrane composite 1 will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a diagram showing a separation device 2. Fig. 6 is a diagram showing the flow of separation of a mixed substance by the separation device 2.

[0046] In the separation device 2, a mixed substance containing multiple types of fluids (i.e., gases or liquids) is supplied to the zeolite membrane composite 1, and highly permeable substances in the mixed substance (hereinafter also referred to as "highly permeable substances") are separated from the mixed substance by permeating through the zeolite membrane composite 1. Separation in the separation device 2 may be performed, for example, for the purpose of extracting highly permeable substances from the mixed substance, or for the purpose of concentrating less permeable substances (hereinafter also referred to as "lowly permeable substances").

[0047] The mixed substance (i.e., 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.

[0048] The mixture may include one or more of hydrogen (H), helium (He), nitrogen (N), oxygen (O), water (H), carbon monoxide (CO), carbon dioxide (CO), nitrogen oxides, ammonia (NH), sulfur oxides, hydrogen sulfide (H), sulfur fluoride, mercury (Hg), arsine (AsH), hydrogen cyanide (HCN), carbonyl sulfide (COS), C to C hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. The highly permeable substance may be one or more of H, He, N, O, CO, NH, and H, preferably H.

[0049] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5), etc. X It is a gas called NOX.

[0050] Sulfur oxides are compounds of sulfur and oxygen. Examples of sulfur oxides include sulfur dioxide (SO2), sulfur trioxide (SO3), and other sulfur compounds. X It is a gas called SOX.

[0051] Sulfur fluoride is a compound of fluorine and sulfur. The sulfur fluoride may be, for example, disulfur difluoride (FSSF, S=SF), sulfur difluoride (SF), sulfur tetrafluoride (SF), sulfur hexafluoride (SF), or disulfur decafluoride (SF). 10 ) etc.

[0052] C1-C8 hydrocarbons are hydrocarbons with one or more carbon atoms and eight or less. C3-C8 hydrocarbons may be straight-chain compounds, branched-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be 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), normal butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), and isobutene (CH2=C(CH3)2).

[0053] The organic acid may be a carboxylic acid or a sulfonic acid. Examples of the carboxylic acid include formic acid (CHO), acetic acid (CHO), oxalic acid (CHO), acrylic acid (CHO), or benzoic acid (CHCOOH). Examples of the sulfonic acid include ethanesulfonic acid (CHOS). The organic acid may be a chain compound or a cyclic compound.

[0054] The alcohols mentioned above are, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)) or butanol (C4H9OH).

[0055] Mercaptans are organic compounds with hydrogenated sulfur (SH) at the end, also known as thiols or thioalcohols. Examples of the mercaptans include methyl mercaptan (CHSH), ethyl mercaptan (CHSH), and 1-propanethiol (CHSH).

[0056] The esters mentioned above are, for example, formates or acetates.

[0057] The ethers mentioned above are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3), diethyl ether ((C2H5)2O) or tetrahydrofuran ((CH2)4O).

[0058] The ketone may be, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO).

[0059] The aldehydes mentioned above are, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO) or butanal (butyraldehyde) (C3H7CHO).

[0060] In the following description, it is assumed that the mixed substance to be separated by the separation device 2 is a mixed liquid containing a plurality of types of liquid, and that separation is performed by pervaporation.

[0061] The separation device 2 includes a zeolite membrane composite 1, a plugging section 21, a housing 22, two seal members 23, a supply section 26, a first recovery section 27, and a second recovery section 28. The zeolite membrane composite 1, the plugging section 21, and the seal members 23 are housed in the housing 22. The supply section 26, the first recovery section 27, and the second recovery section 28 are disposed outside the housing 22 and connected to the housing 22.

[0062] The sealing portion 21 is attached to both ends of the support 11 in the longitudinal direction (i.e., the left-right direction in FIG. 5 ), and is a member that covers and seals both longitudinal end faces of the support 11 and the outer peripheral surfaces near these end faces. The sealing portion 21 prevents liquid from flowing in or out from these end faces of the support 11. The sealing portion 21 is, for example, a plate-like 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, and therefore both longitudinal ends of each through hole 111 of the support 11 are not covered by the sealing portion 21. Therefore, liquid and the like can flow in and out of the through holes 111 from these ends.

[0063] The shape of the housing 22 is not particularly limited, and may be, for example, a substantially cylindrical tubular member. The housing 22 is formed 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 longitudinal end of the housing 22 (i.e., the left end in FIG. 5 ), and a first discharge port 222 is provided at the other end. A second discharge port 223 is provided on a side surface of the housing 22. A supply unit 26 is connected to the supply port 221. A first collection unit 27 is connected to the first discharge port 222. A second collection 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 around the housing 22.

[0064] Two seal members 23 are disposed around the entire circumference 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 seal member 23 is a substantially annular member made of a liquid-impermeable material. The seal members 23 are, for example, O-rings made of a flexible resin. The seal members 23 are in close contact with the outer circumferential surface of the zeolite membrane composite 1 and the inner circumferential surface of the housing 22 around the entire circumference. In the example shown in FIG. 5 , the seal member 23 is in close contact with the outer circumferential surface of the sealing portion 21 and indirectly with the outer circumferential surface of the zeolite membrane composite 1 via the sealing portion 21. A seal is formed between the seal member 23 and the outer circumferential surface of the zeolite membrane composite 1 and between the seal member 23 and the inner circumferential surface of the housing 22, so that liquids can hardly or completely pass through.

[0065] The supply unit 26 supplies the mixed liquid to the internal space of the housing 22 through the supply port 221. The supply unit 26 includes, for example, a pump that pressure-feeds the mixed liquid toward the housing 22. The pump includes a temperature regulator and a pressure regulator that regulate the temperature and pressure, respectively, of the mixed liquid supplied to the housing 22. The first recovery unit 27 includes, for example, a storage container that stores the liquid discharged from the housing 22, or a pump that transfers the liquid. The second recovery unit 28 includes, for example, a vacuum pump that reduces the pressure of the space outside the outer circumferential surface of the zeolite membrane composite 1 in the housing 22 (i.e., the space sandwiched between the two seal members 23), and a cooling chiller trap that cools and liquefies the gas that has vaporized and permeated the zeolite membrane composite 1.

[0066] When separating a mixed liquid, the above-described separation device 2 is provided, thereby preparing a zeolite membrane composite 1 (FIG. 6: step S21). Subsequently, a mixed liquid containing a plurality of liquids having different permeabilities to the zeolite membrane 12 is supplied by the supply unit 26 to 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 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.

[0067] The mixed liquid supplied from the supply unit 26 to the housing 22 is introduced into each of the through-holes 111 of the support 11 from the left end of the zeolite membrane composite 1 in the drawing, as indicated by arrow 251. A highly permeable substance, which is a liquid with high permeability in the mixed liquid, vaporizes and permeates through the zeolite membrane 12 provided on the inner circumferential surface of each through-hole 111 and the support 11, and is discharged from the outer circumferential surface of the support 11. In this way, the highly permeable substance (e.g., water) is separated from a less permeable substance (e.g., ethanol), which is a liquid with low permeability in the mixed liquid (step S22).

[0068] The gas (hereinafter referred to as "permeate") discharged from the outer peripheral surface of the support 11 is led to the second collection section 28 via the second discharge port 223 as shown by the arrow 253, where it is cooled and collected as a liquid. The pressure of the gas collected by the second collection section 28 via the second discharge port 223 (i.e., permeate pressure) is, for example, about 6.67 kPa (about 50 Torr). The permeate may include low-permeate substances that have permeated the zeolite membrane 12 in addition to the high-permeate substances described above.

[0069] Furthermore, the liquid in the mixed liquid excluding the substances that have permeated the zeolite membrane 12 and the support 11 (hereinafter referred to as "impermeable substances") 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 substances described above, the impermeable substances may also include highly permeable substances that did not permeate the zeolite membrane 12. The impermeable substances recovered by the first recovery unit 27 may be circulated to the supply unit 26 and supplied again into the housing 22, for example.

[0070] The separation apparatus 2 shown in FIG. 5 may be used, for example, as a membrane reactor. In this case, the housing 22 is used as a reactor. A catalyst that promotes a chemical reaction of the raw materials supplied from the supply unit 26 is accommodated inside the housing 22. The catalyst is disposed, for example, between the supply port 221 and the first discharge port 222. Preferably, the catalyst is disposed near the zeolite membrane 12 of the zeolite membrane composite 1. The catalyst is of an appropriate material and shape depending on the type of raw material and the type of chemical reaction to be caused in the raw material. The raw material may include one type or two or more types of substances. The membrane reactor may further include a heating device for heating the reactor (i.e., the housing 22) and the raw material to promote the chemical reaction of the raw material.

[0071] In the separation device 2 used as a membrane reactor, a mixed substance containing a product substance produced by a chemical reaction of a raw material in the presence of a catalyst is supplied to the zeolite membrane 12 in the same manner as described above, and the highly permeable substance in the mixed substance permeates the zeolite membrane 12, thereby being separated from other substances having lower permeability than the highly permeable substance. For example, the mixed substance may be a fluid containing the product substance and unreacted raw material. The mixed substance may also contain two or more types of product substances. The highly permeable substance may be a product substance produced from the raw material, or may be a substance other than the product substance. Preferably, the highly permeable substance contains one or more types of product substances.

[0072] When the highly permeable substance is a product substance produced from a raw material, the yield of the product substance can be improved by separating the product substance from other substances using the zeolite membrane 12. When the mixed substance contains two or more types of product substances, the two or more types of product substances may be highly permeable substances, or some of the two or more types of product substances may be highly permeable substances.

[0073] Next, zeolite composite membranes will be described in Examples 1 to 9 and Comparative Examples 1 to 4. Table 1 shows the composition (molar ratio) of the raw material solution used to form the LTA zeolite membrane, the stirring time, the time from the end of stirring to the start of heating, the synthesis temperature, and the synthesis time.

[0074] [Table 1]

[0075] (Seed crystal production) Colloidal silica (LUDOX AS-40, Sigma-Aldrich) as the Si source was added to a tetramethylammonium hydroxide solution (15% aqueous solution, Fujifilm Wako Pure Chemical Industries, Ltd.) as the SDA, and the mixture was stirred for 30 minutes to produce solution A. Sodium hydroxide (Sigma-Aldrich) as the Na source and sodium aluminate powder (Sigma-Aldrich) as the Al source were added to pure water and stirred until transparent to produce solution B. Solution B was added dropwise to solution A and stirred at room temperature for 24 hours or more to produce a seed crystal raw material solution with the composition 1Al2O3:6.5SiO2:1.45Na2O:1.8(TMA)2O:320HO.

[0076] LTA zeolite crystals were obtained by hydrothermal synthesis of the seed crystal raw material solution at 100°C for 60 hours. The obtained LTA zeolite crystals were heat-treated at 450°C for 15 hours to burn off the SDA. The heat-treated LTA zeolite crystals were pulverized in a ball mill for 45 hours to obtain seed crystals. Measurement by energy dispersive X-ray spectroscopy was performed in the same manner as in the "Membrane Si / Al ratio measurement" described below, and the Si / Al molar ratio of the seed crystals was found to be 2.4 or higher. Thereafter, a monolithic porous alumina support was brought into contact with the solution in which the seed crystals were dispersed, and the seed crystals were attached to the cells, which were the through-holes of the support.

[0077] (Preparation of LTA film) Sodium hydroxide (Sigma-Aldrich), a Na source, and sodium aluminate powder (Sigma-Aldrich), an Al source, were mixed with pure water. In Example 3 and Comparative Example 4, a tetramethylammonium hydroxide solution (SDA) was further added. After stirring the mixture at room temperature for 1 hour, colloidal silica (Snowtex-50T, Nissan Chemical Industries, Ltd.), a Si source, was added to obtain a raw material solution. Assuming that the Si, Al, and Na sources all exist as oxides, the molar ratios of SiO2 / Al2O3, H2O / Na2O, Na2O / SiO2, and SDA / Al2O3 in the raw material solution are as shown in Table 1. In Examples 1 to 9, the molar ratio of SiO2 / Al2O3 was 4 to 7, the molar ratio of H2O / Na2O was 100 to 1200, and the molar ratio of Na2O / SiO2 was 0.1 to 0.6. On the other hand, in Comparative Example 1, the molar ratio of Na2O / SiO2 was set to 1.0, which was larger than the above range, and in Comparative Example 4, the molar ratio of SiO2 / Al2O3 was set to 10, which was larger than the above range.

[0078] Subsequently, the raw material solution was stirred at room temperature. The stirring times of the raw material solution are as shown in Table 1. In Examples 1 to 9, the stirring time of the raw material solution was set to 10 hours or more. On the other hand, in Comparative Examples 1 and 2, the stirring time of the raw material solution was set to 6 hours.

[0079] After the "time from the end of stirring to the start of heating" in Table 1 had elapsed from the end of stirring of the raw material solution, a support to which seed crystals had been attached was immersed in the raw material solution, and heating of the raw material solution (hydrothermal synthesis) was initiated. The synthesis temperature and synthesis time during hydrothermal synthesis are as shown in Table 1. As a result, an LTA zeolite membrane was formed on the support. In all of Examples 1 to 9, the time from the end of stirring to the start of heating was set to 70 minutes or more. On the other hand, in Comparative Example 3, the time from the end of stirring to the start of heating was set to 40 minutes.

[0080] After the hydrothermal synthesis, the support and the zeolite membrane were thoroughly washed with pure water and then dried at 80°C. In Example 3 and Comparative Example 4, in which the raw material solution contained SDA, the LTA zeolite membrane was heat-treated at 450°C for 30 hours to burn off the SDA. Through the above treatment, the zeolite membrane composites of Examples 1 to 9 and Comparative Examples 1 to 4, each having an LTA zeolite membrane, were obtained.

[0081] Table 2 shows the Si / Al ratio, XRD diffraction peak intensity ratio, water / ethanol separation performance, hydrothermal durability, and strength of the LTA-type zeolite membrane.

[0082] [Table 2]

[0083] (Membrane Si / Al ratio measurement) The Si / Al molar ratio of the zeolite membrane cross section ("Si / Al ratio" in Table 2) was measured using a scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDX). The acceleration voltage was 15 kV. In Examples 1 to 9, in which the stirring time of the raw solution was 10 hours or more and the time from the end of stirring to the start of heating was 70 minutes or more, the Si / Al ratio was 1.2 or more. In particular, in Examples 1 to 7, in which the HO / NaO molar ratio in the raw solution was 350 or more, the Si / Al ratio was 1.74 to 2.80. On the other hand, in Comparative Examples 1 and 2, in which the stirring time of the raw solution was 6 hours, the Si / Al ratio was 1.03 and 1.25, respectively. In Comparative Example 3, in which the time from the end of stirring to the start of heating was 40 minutes, the separation factor was extremely small in the "water / ethanol separation test" described below, and an appropriate separation membrane was not formed. Therefore, measurements other than the "water / ethanol separation test" were not performed. In Comparative Example 4, in which the molar ratio of SiO2 / Al2O3 in the raw material solution was 10, the Si / Al ratio was 2.92, but a dense film was not formed, so measurements other than the Si / Al ratio were not performed.

[0084] (Membrane XRD measurement) The diffraction patterns of the zeolite membrane surfaces of Examples 1 to 9 and Comparative Examples 1 and 2 were measured by X-ray diffraction measurement. From the X-ray diffraction patterns, it was confirmed that LTA zeolite membranes were formed in Examples 1 to 9 and Comparative Examples 1 and 2. Furthermore, in the X-ray diffraction patterns of Examples 1 to 9, the ratio of the intensity of the peak present near 2θ=24.0° to the intensity of the peak present near 2θ=7.2° (represented as "24.0° / 7.2°" in Table 2, hereinafter simply referred to as "24.0° / 7.2° intensity ratio") was 0.85 or more, and in Examples 1 to 3 and 6 to 9, it was 0.90 or more. Furthermore, in Examples 1 to 5 and 7 to 9, the ratio of the intensity of the peak present near 2θ=30.0° to the intensity of the peak present near 2θ=7.2° (represented as "30.0° / 7.2°" in Table 2, hereinafter simply referred to as "30.0° / 7.2° intensity ratio") was 0.85 or more, and in Examples 1 to 3, 8 and 9 it was 0.90 or more. On the other hand, in Comparative Examples 1 and 2, in which the stirring time of the raw material solution was 6 hours, the intensity ratios at 24.0° / 7.2° and 30.0° / 7.2° were both less than 0.85.

[0085] The X-ray diffraction measurements were performed using a Rigaku X-ray diffractometer (MiniFlex600) with a tube voltage of 40 kV, a tube current of 15 mA, a scan rate of 0.5° / min, and a scan step of 0.02°. The divergence slit was 1.25°, the scattering slit was 1.25°, the receiving slit was 0.3 mm, the incident Soller slit was 5.0°, and the receiving Soller slit was 5.0°. A monochromator was not used, and 0.015 mm thick nickel foil was used as a CuKβ ray filter.

[0086] (Water / ethanol separation test) A water / ethanol separation test was carried out by pervaporation using the separation apparatus 2 described above. In this test, a mixed liquid containing 50% by mass of water and 50% by mass of ethanol at 60°C was supplied from the supply section 26 to the housing 22 via the supply port 221 at atmospheric pressure. The second discharge port 223, which is the permeation side of the zeolite membrane composite, was depressurized to -94.66 kPaG (approximately 50 Torr). The gas that permeated the zeolite membrane and was discharged from the outer peripheral surface of the support 11 was cooled in the second recovery section 28 and recovered as a liquid. From the mass of the liquid recovered in the second recovery section 28, the total permeation flux (kg / m), which is the amount of fluid that permeated the membrane per unit area per unit time, was calculated. 2 h) was calculated. In addition, the concentrations (mass%) of water and ethanol in the liquid were measured, and the water concentration / ethanol concentration was obtained as the separation factor.

[0087] In all of Examples 1 to 9 and Comparative Examples 1 to 3 in which measurements were performed, the total permeation flux was 2 kg / m 2 h or more. The separation factors were good, being 2000 or more, except for Comparative Example 3. In Comparative Example 3, the separation factor was 156, which was extremely small.

[0088] (Hydrothermal durability evaluation) To evaluate hydrothermal durability, the zeolite membrane composite was immersed in pure water at 60°C for 6 hours and then dried at 80°C for 12 hours or more. After that, the above-mentioned "water / ethanol separation test" was performed again to measure the separation factor, and the ratio of the separation factor after immersion to the separation factor before immersion ("Separation factor after immersion in hot water / Separation factor before immersion in hot water" in Table 2) was used as an index of hydrothermal durability.

[0089] In Examples 1 to 9, the ratio of the separation factor after immersion to the separation factor before immersion was 0.5 or more. In Examples 1 to 7, in which the Si / Al molar ratio was 1.74 to 2.80, the ratio of the separation factor after immersion to the separation factor before immersion was 0.7 or more, which was significantly larger than in Comparative Examples 1 and 2.

[0090] (Water pressure test) In the hydraulic pressure test, the zeolite membrane composite was first positioned so that its longitudinal direction was approximately vertical. Next, room-temperature pure water was introduced into the interior through the lower opening of each through-hole, and the water in the through-holes was pressurized, thereby hydraulically pressurizing the zeolite membrane composite. The pressure was 10 MPaG, and the pressurization time was 1 minute. After drying the zeolite membrane composite at 80°C for 12 hours or more, the above-mentioned "water / ethanol separation test" was performed again to measure the separation factor. The ratio of the separation factor after hydraulic pressure to the separation factor before hydraulic pressure ("Separation factor after hydraulic pressure / Separation factor before hydraulic pressure" in Table 2) was used as an index of strength.

[0091] In Examples 1 to 9, in which at least one of the intensity ratios at 24.0° / 7.2° and 30.0° / 7.2° was 0.85 or higher, the ratio of the separation factor after hydraulic pressurization to the separation factor before hydraulic pressurization was sufficiently larger than in Comparative Examples 1 and 2. That is, the strength of the zeolite membrane composites in Examples 1 to 9 was improved compared to Comparative Examples 1 and 2. In Examples 1 to 3, 8, and 9, in which both the intensity ratio at 24.0° / 7.2° and the intensity ratio at 30.0° / 7.2° were 0.90 or higher, the ratio of the separation factor after hydraulic pressurization to the separation factor before hydraulic pressurization was 1, and the separation factor did not change before and after hydraulic pressurization.

[0092] Incidentally, even in Examples 4 and 5, in which the intensity ratios at 24.0° / 7.2° and 30.0° / 7.2° were slightly greater than 0.85, the ratios of the separation factors after hydraulic pressure to those before hydraulic pressure were sufficiently greater than those in Comparative Examples 1 and 2. Therefore, it is believed that the strength of the zeolite membrane composite is improved when at least one of the intensity ratios at 24.0° / 7.2° and 30.0° / 7.2° is 0.85 or greater.

[0093] As described above, the zeolite membrane composite 1 includes a porous support 11 and a zeolite membrane 12 made of LTA zeolite and provided on the support 11. The Si / Al molar ratio in the zeolite membrane 12 is 1.74 or more and 2.80 or less. This makes it possible to provide a zeolite membrane composite 1 with improved hydrothermal durability (see Examples 1 to 7), enabling the zeolite membrane composite 1 to be used for a long period of time.

[0094] Preferably, in an X-ray diffraction pattern obtained by irradiating the surface of the zeolite membrane 12 with X-rays, the intensity of at least one of the peaks near 2θ=24.0° and 2θ=30.0° is 0.85 times or more the intensity of the peak near 2θ=7.2°. This makes it possible to provide a zeolite membrane composite 1 that has improved strength in addition to hydrothermal durability (see Examples 1 to 7). To further improve the strength of the zeolite membrane composite 1, it is preferable that both the intensity of the peak near 2θ=24.0° and the intensity of the peak near 2θ=30.0° are 0.90 times or more the intensity of the peak near 2θ=7.2° (see Examples 1 to 3).

[0095] From the viewpoint of ensuring a certain level of hydrothermal durability in the zeolite membrane composite 1, the Si / Al molar ratio in the zeolite membrane 12 is sufficient as long as it is 1.2 or more (see Examples 1 to 9). In this case, the strength of the zeolite membrane composite 1 can be improved by ensuring that in the X-ray diffraction pattern, at least one of the peak intensities near 2θ=24.0° and 2θ=30.0° is 0.85 times or more the peak intensity near 2θ=7.2° (see Examples 1 to 9). Similarly, to further improve the strength of the zeolite membrane composite 1, it is preferable that both the peak intensities near 2θ=24.0° and 2θ=30.0° are 0.90 times or more the peak intensity near 2θ=7.2° (see Examples 1 to 3, 8, and 9).

[0096] Preferably, the thickness of the zeolite membrane 12 is 5 μm or less. In the zeolite membrane composite 1, the zeolite membrane 12 can be made thinner while improving the hydrothermal durability and / or strength, and the permeation amount of the highly permeable substance can be increased.

[0097] In the preferred zeolite membrane composite 1, when a mixed liquid containing 50 mass % of water and 50 mass % of ethanol at 60°C is supplied to the permeation side at -94.66 kPaG, the total permeation flux is 2.0 kg / m 2 h or more, and the separation factor between water and ethanol is 2000 or more. This makes it possible to properly separate a mixed liquid of water and ethanol.

[0098] As described above, the membrane reactor includes the zeolite membrane composite 1, a catalyst for promoting the chemical reaction of the raw materials, a reactor (housing 22 in the above example) containing the zeolite membrane composite 1 and the catalyst, and a supply unit 26 for supplying the raw materials to the reactor. The zeolite membrane composite 1 separates highly permeable substances from other substances by allowing them to pass through the mixed substance containing the product produced by the chemical reaction of the raw materials in the presence of the catalyst. This allows the highly permeable substances to be efficiently separated from other substances, as described above. This membrane reactor is particularly suitable for separating HO.

[0099] The method for producing the zeolite membrane composite 1 includes the steps of preparing a raw material solution (step S13), stirring the raw material solution for 10 hours or more after step S13 (step S14), immersing a porous support 11 having seed crystals containing LTA zeolite attached thereto in the raw material solution (step S15), and, 70 minutes or more after the end of step S14, heating the raw material solution to form a zeolite membrane 12 made of LTA zeolite on the support 11 (step S16). In step S13, a Na source, an Al source, and a Si source are mixed with water to prepare a raw material solution. In the raw material solution, the SiO / AlO molar ratio is 4 to 7, the HO / NaO molar ratio is 100 to 1200, and the NaO / SiO molar ratio is 0.1 to 0.6 (see Examples 1 to 9).

[0100] In the above-described manufacturing method, the stirring time of the raw solution is set to 10 hours or more, which increases the uniformity of the raw solution and allows the crystals to grow randomly without orientation. Furthermore, since the heating of the raw solution begins 70 minutes or more after the end of stirring, the raw material particles have moderately aggregated to produce raw material particles of appropriate size by the time heating begins. This allows the crystal growth rate to be controlled and the generation of membrane defects (e.g., the generation of heterogeneous phases and impurities) to be suppressed. As a result, a preferable zeolite membrane composite 1 with improved hydrothermal durability and / or strength can be manufactured. The presence or absence of heterogeneous phases and impurities can be confirmed by X-ray diffraction measurement of the surface of the zeolite membrane 12.

[0101] Preferably, the molar ratio of H2O / Na2O in the raw material solution is 350 or more (see Examples 1 to 7). This more reliably improves the hydrothermal durability of the zeolite membrane composite 1. Preferably, the molar ratio of Si / Al in the seed crystals is 2.4 or more. This more reliably produces a preferred zeolite membrane composite 1. Depending on the performance required of the zeolite membrane composite 1, the molar ratio of H2O / Na2O in the raw material solution may be less than 350, and the molar ratio of Si / Al in the seed crystals may be less than 2.4.

[0102] The zeolite membrane composite 1, the membrane reactor, and the method for producing the zeolite membrane composite 1 can be modified in various ways.

[0103] When high strength is not required for the zeolite membrane composite 1, the intensities of the peaks around 2θ=24.0° and 2θ=30.0° in the X-ray diffraction pattern may be less than 0.85 times the intensity of the peak around 2θ=7.2°.

[0104] The zeolite membrane composite 1 may be produced by a method other than the above-mentioned production method.

[0105] In addition to the support 11 and the zeolite membrane 12, the zeolite membrane composite 1 may further include a functional membrane or a protective membrane laminated on the zeolite membrane 12. Such a functional membrane or protective membrane may be an inorganic membrane such as a zeolite membrane, a silica membrane, or a carbon membrane, or an organic membrane such as a polyimide membrane or a silicone membrane. Furthermore, a substance that easily adsorbs water may be added to the functional membrane or protective membrane laminated on the zeolite membrane 12.

[0106] In the separation device 2, the membrane reactor and the separation method, the mixed substances may be separated by vapor permeation, reverse osmosis, gas permeation or the like, in addition to the pervaporation method exemplified in the above description.

[0107] In the separation device 2, the membrane reactor, and the separation method, substances other than those exemplified in the above description may be separated from the mixed substance.

[0108] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0109] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention. [Industrial Applicability]

[0110] The zeolite membrane composite of the present invention can be used, for example, as a dehydration membrane, and further, can be used in various fields in which zeolites are used, such as separation membranes for various substances other than water and adsorption membranes for various substances. [Explanation of symbols]

[0111] 1 Zeolite membrane composite 11 Support 12 Zeolite membrane S11~S16, S21, S22 steps

Claims

1. A zeolite membrane composite, a porous support; a zeolite membrane formed on the support and made of LTA zeolite; Equipped with The zeolite membrane has a Si / Al molar ratio of 1.74 or more and 2.80 or less.

2. The zeolite membrane composite according to claim 1, In an X-ray diffraction pattern obtained by irradiating the surface of the zeolite membrane with X-rays, at least one of the intensity of the peak present near 2θ = 24.0° and the intensity of the peak present near 2θ = 30.0° is 0.85 times or more the intensity of the peak present near 2θ = 7.2°.

3. A zeolite membrane composite, a porous support; a zeolite membrane formed on the support and made of LTA zeolite; Equipped with The zeolite membrane has a Si / Al molar ratio of 1.2 or more, In an X-ray diffraction pattern obtained by irradiating the surface of the zeolite membrane with X-rays, at least one of the intensity of the peak present near 2θ = 24.0° and the intensity of the peak present near 2θ = 30.0° is 0.85 times or more the intensity of the peak present near 2θ = 7.2°.

4. The zeolite membrane composite according to claim 1, The thickness of the zeolite membrane is 5 μm or less.

5. The zeolite membrane composite according to claim 3, The thickness of the zeolite membrane is 5 μm or less.

6. A membrane reactor comprising: The zeolite composite membrane according to any one of claims 1 to 5, a catalyst that promotes a chemical reaction of the raw materials; a reactor containing the zeolite membrane composite and the catalyst; a supply unit that supplies the raw material to the reactor; Equipped with The zeolite membrane composite separates the highly permeable substance from the other substances in the mixture containing the product substance produced by the chemical reaction of the raw material in the presence of the catalyst by allowing the highly permeable substance to pass through.

7. A method for producing a zeolite membrane composite, comprising: a) preparing a raw material solution by mixing a sodium source, an aluminum source, and a silicon source in water; b) after the step a), stirring the raw material solution for 10 hours or more; c) immersing a porous support having seed crystals containing LTA zeolite attached thereto in the raw material solution; d) a step of heating the raw material solution 70 minutes or more after the completion of the step b) to form a zeolite membrane made of LTA zeolite on the support to which the seed crystals are attached; Equipped with In the raw material solution, SiO ２ / Al ２ O ３ The molar ratio of H is 4 or more and 7 or less, ２ O / Na ２ The molar ratio of Na to O is 100 or more and 1200 or less, ２ O / SiO ２ The molar ratio of is 0.1 or more and 0.6 or less.

8. The method for producing the zeolite membrane composite according to claim 7, In the raw material solution, H ２ O / Na ２ The molar ratio of O is 350 or more.

9. The method for producing the zeolite membrane composite according to claim 7 or 8, The Si / Al molar ratio of the seed crystal is 2.4 or more.

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