Method for treating zeolite membrane

Abstract

This method for treating a zeolite membrane comprises: a step (step S31) for preparing a heat-treated zeolite membrane; a step (step S32) for bringing a moisture-containing gas having a volumetric moisture content of 4,000-65,000 vol by ppm into contact with the zeolite membrane to adsorb water molecules to the zeolite membrane, after the step S31; and a step (step S33) for partially removing the water molecules adsorbed to the zeolite membrane, after the step S32. Consequently, the permeation performance of the zeolite membrane can be stabilized.

Description

Zeolite membrane treatment method

[0001] The present invention relates to a method for treating a zeolite membrane. [Reference to Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2024-41921, filed on March 18, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] Currently, various research and development efforts are being conducted on the separation of specific molecules using separation membranes such as zeolite membranes. For example, a technique is known in which a mixed gas containing multiple types of gases is supplied to a zeolite membrane, and a highly permeable gas is separated from the mixed gas by passing it through the pores of the zeolite membrane. In addition, a technique is known in which the performance of a zeolite membrane is improved by performing a predetermined treatment on the zeolite membrane.

[0003] For example, Japanese Patent Application Laid-Open No. 2013-013884 (Reference 1) proposes heat-treating a zeolite composite membrane at a temperature of 50°C or higher, followed by immersion in water at a temperature of 40°C to 300°C for one hour or longer (hereinafter referred to as "hot water treatment"). Reference 1 believes that the hot water treatment converts Si-O-Si bonds formed on the zeolite surface by calcination or the like into highly hydrophilic Si-OH bonds, thereby improving water permeability. Reference 1 also believes that the hot water treatment repairs minute defects in the zeolite membrane using amorphous silica or the like within the defects as a raw material, thereby improving the performance of the zeolite membrane.

[0004] Japanese Patent Laid-Open Publication No. 2016-159185 (Document 2) proposes a technique for treating a zeolite membrane composite in a solvent under a pressure of 0.5 MPa or more. Document 2 considers that this treatment causes some substance contained in the solvent to penetrate into defects present in the zeolite membrane, thereby sealing the defects and improving separation performance.

[0005] In the production of zeolite membrane composites, zeolite membranes are typically calcined at high temperatures to remove impurities and organic structure-directing agents. Zeolite membranes calcined at such high temperatures are prone to adsorb water molecules from the atmosphere. Therefore, if a zeolite membrane composite is stored as is, further adsorption of water molecules to the zeolite membrane and desorption of water molecules adsorbed to the zeolite membrane may occur, which may result in variations in the permeation performance (e.g., separation performance and permeation rate) of the zeolite membrane among multiple zeolite membrane composites produced under the same conditions. Furthermore, even for the same zeolite membrane composite, variations in the permeation performance may occur if the storage period is changed.

[0006] However, although research has been conducted on improving the performance of zeolite membranes as in Literature 1 and Literature 2, no studies have been conducted on techniques for suppressing variations in the permeation performance of zeolite membranes (i.e., stabilizing the permeation performance of zeolite membranes).

[0007] The present invention is directed to a method for treating a zeolite membrane, and aims to stabilize the permeation performance of the zeolite membrane.

[0008] A first aspect of the invention is a method for treating a zeolite membrane, comprising: a) preparing a heat-treated zeolite membrane; b) after the step a), contacting the zeolite membrane with a moisture-containing gas having a volumetric moisture fraction of 4000 ppmv or more and 65000 ppmv or less to adsorb water molecules onto the zeolite membrane; and c) after the step b), partially removing the water molecules adsorbed onto the zeolite membrane.

[0009] According to the present invention, the permeation performance of the zeolite membrane can be stabilized.

[0010] The invention of Aspect 2 is the zeolite membrane treatment method of Aspect 1, wherein in the step c), water molecules adsorbed to the zeolite membrane are partially removed by performing one or more of the following processes: reducing the pressure on the zeolite membrane; replacing the atmosphere around the zeolite membrane with a dry gas having a lower water volume fraction than the water-containing gas; spraying the dry gas onto the zeolite membrane; and housing the zeolite membrane in a container together with a moisture adsorbent.

[0011] A third aspect of the present invention is the zeolite membrane treatment method according to the second aspect, wherein the step c) comprises subjecting the zeolite membrane to a decompression treatment, in which the zeolite membrane is maintained in a vacuum atmosphere for 3 hours or more and 240 hours or less.

[0012] A fourth aspect of the present invention is the zeolite membrane treatment method according to any one of the first to third aspects, wherein the moisture-containing gas is atmospheric air.

[0013] A fifth aspect of the invention is the method for treating a zeolite membrane according to the fourth aspect, wherein in the step b), the zeolite membrane is brought into contact with air having a relative humidity of 25% or more and 80% or less for 1 hour or more and 72 hours or less, thereby causing water molecules to be adsorbed onto the zeolite membrane.

[0014] A sixth aspect of the invention is the method for treating a zeolite membrane according to any one of the first to third aspects (or any one of the first to fifth aspects), wherein the maximum number of rings in the zeolite constituting the zeolite membrane is 10 or less.

[0015] 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.

[0016] Fig. 1 is a cross-sectional view of a separation membrane composite according to one embodiment; Fig. 2 is a cross-sectional view showing an enlarged portion of the separation membrane composite; Fig. 3 is a view showing a separation device; Fig. 4 is a view showing a flow of separation of mixed substances; Fig. 5 is a view showing a flow of manufacturing a zeolite membrane composite; Fig. 6 is a view showing a flow of treatment of a zeolite membrane.

[0017] Fig. 1 is a cross-sectional view showing one embodiment of a zeolite membrane composite 1 to be treated by the zeolite membrane treatment method according to the present invention. Fig. 2 is a cross-sectional view showing an enlarged portion of the zeolite membrane composite 1. The zeolite membrane composite 1 includes a support 11 and a zeolite membrane 12. In Fig. 1, the zeolite membrane 12 is depicted with a thick line. In Fig. 2, the zeolite membrane 12 is depicted with hatched lines to make it appear thicker than it actually is.

[0018] The support 11 is a porous member that is permeable to gas and liquid. In the example shown in FIG. 1 , the support 11 is an integrally molded, continuous, approximately columnar member. The support 11 is provided with a plurality of through holes 111 that each extend in the longitudinal direction. In other words, the support 11 is a so-called monolithic member. The outer shape of the support 11 is, for example, approximately cylindrical. The cross section perpendicular to the longitudinal direction of each through hole 111 (i.e., cell) is, for example, approximately 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.

[0019] 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 columnar 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.

[0020] The material of the support 11 can be any of various substances (e.g., ceramic or metal) as long as it is chemically stable in the process of forming the zeolite membrane 12 on its surface. In this embodiment, the support 11 is formed of a ceramic sintered body. Examples of ceramic sintered bodies 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 includes at least one of alumina, silica, and mullite.

[0021] 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.

[0022] The average pore diameter of the support 11 is, for example, 0.01 μm to 70 μm, preferably 0.05 μm to 25 μm. The average pore diameter of the support 11 near the surface on which the zeolite membrane 12 is formed is 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. The average pore diameter can be measured, for example, by a mercury porosimeter, a perm porometer, or a nanoperm porometer. With regard to the pore diameter 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%.

[0023] 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 grain 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 grain 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.

[0024] The zeolite membrane 12 is a substantially cylindrical thin film provided on the inner surface of the through-hole 111 of the support 11, covering substantially the entire inner surface. The zeolite membrane 12 is a dense porous membrane with micropores. A zeolite membrane is at least a membrane of zeolite formed on the surface of the support 11 or the like, and does not include a membrane in which zeolite particles are simply dispersed in an organic film. A zeolite membrane can be used as a separation membrane for separating a specific substance from a mixture of substances. Other substances are less likely to permeate a zeolite membrane than the specific substance. In other words, the permeation rate of the other substances through the zeolite membrane is lower than the permeation rate of the specific substance. Note that a zeolite membrane may contain two or more types of zeolites with different structures or compositions.

[0025] 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. Increasing the thickness of the zeolite membrane 12 improves separation performance. Increasing the thickness of the zeolite membrane 12 increases the permeation rate. 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.

[0026] The pore diameter of the zeolite crystals contained in the zeolite membrane 12 (hereinafter also simply referred to as the "pore diameter of the zeolite membrane 12") is 0.2 nm or more and 0.8 nm or less, more preferably 0.25 nm or more and 0.7 nm or less, and even more preferably 0.28 nm or more and 0.45 nm or less. If the pore diameter of the zeolite membrane 12 is less than 0.2 nm, the amount of gas permeating the zeolite membrane 12 may be reduced, and if the pore diameter of the zeolite membrane 12 is greater than 0.8 nm, the gas selectivity of the zeolite membrane 12 may be insufficient. The pore diameter of the zeolite membrane 12 refers to the diameter of the pore (i.e., the minor axis) in a direction approximately perpendicular to the maximum diameter of the pores of the zeolite crystals constituting the zeolite membrane 12 (i.e., the major axis, which is the maximum distance between oxygen atoms). The pore size of the zeolite membrane 12 is smaller than the average pore size on the surface of the support 11 on which the zeolite membrane 12 is disposed.

[0027] When the maximum number of rings in the zeolite constituting the zeolite membrane 12 is n, the minor axis of the n-membered ring pore is defined as the pore diameter of the zeolite membrane 12. Furthermore, when the zeolite has multiple types of n-membered ring pores with the same n, the minor axis of the n-membered ring pore with the largest minor axis is defined as the pore diameter of the zeolite membrane 12. Note that an n-membered ring refers to a portion in which the number of oxygen atoms constituting the skeleton forming the pore is n, and each oxygen atom is bonded to a T atom (described below) to form a ring structure. Furthermore, an n-membered ring refers to a ring that forms a through-hole (channel), but does not include a ring that does not form a through-hole. An n-membered ring pore is a pore formed by an n-membered ring. From the viewpoint of improving selectivity, the maximum number of rings in the zeolite contained in the above-mentioned zeolite membrane 12 is preferably 10 or less (e.g., 10, 8, or 6).

[0028] The pore size of the zeolite membrane 12 is uniquely determined by the skeletal structure of the zeolite, and can be determined from values ​​disclosed in the "Database of Zeolite Structures" [online] of the International Zeolite Society, available on the Internet at <URL: http: / / www.iza-structure.org / databases / >.

[0029] The type of zeolite constituting the zeolite membrane 12 is not particularly limited, and examples thereof include 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, IHW type, LEV type, LTA type, LTJ type, MEL type, MFI type, MOR type, MTN type, PAU type, RHO type, SOD type, SAT type, etc. Preferably, the zeolite constituting the zeolite membrane 12 is CHA type, DDR type, LTA type, MFI type, or MTN type zeolite.

[0030] The zeolite constituting the zeolite membrane 12 is composed of T atoms (i.e., oxygen tetrahedra (TO ４The atom at the center of the zeolite membrane 12 may include, for example, aluminum (Al). Zeolites constituting the zeolite membrane 12 may include zeolites in which the T atom is silicon (Si) only or contains Si and Al, AlPO zeolites in which the T atom is Al and phosphorus (P), SAPO zeolites in which the T atom is Si, Al, and P, MAPSO zeolites in which the T atom is magnesium (Mg), Si, Al, and P, and ZnAPSO zeolites in which the T atom is zinc (Zn), Si, Al, and P. Some of the T atoms may be substituted with other elements.

[0031] The zeolite membrane 12 contains, for example, Si. The zeolite membrane 12 may contain, for example, any two or more of Si, Al, and P. The zeolite membrane 12 may also contain an alkali metal. The alkali metal is, for example, sodium (Na) or potassium (K). When the zeolite membrane 12 contains Si atoms and Al atoms, the Si / Al ratio in the zeolite membrane 12 is, for example, 1 or more and 100,000 or less. The Si / Al ratio is the molar ratio of Si to Al contained in the zeolite membrane 12. The Si / Al ratio is preferably 5 or more, more preferably 20 or more, and even more preferably 100 or more, and the higher the Si / Al ratio, the better. The Si / Al ratio in the zeolite membrane 12 can be adjusted by adjusting the blending ratio of the Si source and the Al source in the raw material solution, which will be described later.

[0032] Next, separation of a mixed substance using the zeolite membrane composite 1 will be described with reference to Figures 3 and 4. Figure 3 is a diagram showing a separation device 2. Figure 4 is a diagram showing the flow of separation of a mixed substance using the separation device 2.

[0033] 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 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 (hereinafter also referred to as "highly permeable substances") from the mixed substance, or for the purpose of concentrating lowly permeable substances (hereinafter also referred to as "lowly permeable substances").

[0034] 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.

[0035] The mixture may include, for example, hydrogen (H ２ ), helium (He), nitrogen (N ２ ), oxygen (O ２ ), water (H ２ O), water vapor (H ２ O), carbon monoxide (CO), carbon dioxide (CO ２ ), nitrogen oxides, ammonia (NH ３ ), sulfur oxides, hydrogen sulfide (H ２ S), sulfur fluoride, mercury (Hg), arsine (AsH ３ ), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1-C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. ２ , He, N ２ , O ２ , H ２ O, CO ２ , N.H. ３ and H ２ S is one or more substances.

[0036] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO ２ ), nitrous oxide (also called dinitrogen monoxide) (N ２ O), dinitrogen trioxide (N ２ O ３), dinitrogen tetroxide (N ２ O ４ ), dinitrogen pentoxide (N ２ O ５ ) etc. Ｘ It is a gas called NOX.

[0037] Sulfur oxides are compounds of sulfur and oxygen. Examples of the sulfur oxides include sulfur dioxide (SO ２ ), sulfur trioxide (SO ３ ) and other SOs Ｘ It is a gas called SOX.

[0038] Sulfur fluoride is a compound of fluorine and sulfur. The above-mentioned sulfur fluoride is, for example, disulfur difluoride (FS-SF, S=SF ２ ), sulfur difluoride (SF ２ ), sulfur tetrafluoride (SF ４ ), sulfur hexafluoride (SF ６ ) or disulfur decafluoride (S ２ F １０ ) etc.

[0039] 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 either saturated hydrocarbons (i.e., those without double and triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double and / or triple bonds in the molecule). C1-C4 hydrocarbons include, for example, methane (CH ４ ), ethane (C ２ H ６ ), ethylene (C ２ H ４ ), propane (C ３ H ８ ), propylene (C ３ H ６ ), normal butane (CH ３ (CH ２ ) ２ CH ３ ), isobutane (CH(CH ３ ) ３ ), 1-butene (CH ２ =CHCH２ CH ３ ), 2-butene (CH ３ CH=CHCH ３ ) or isobutene (CH ２ =C(CH ３ ) ２ )

[0040] The organic acid is a carboxylic acid or a sulfonic acid. The carboxylic acid is, for example, formic acid (CH ２ O ２ ), acetic acid (C ２ H ４ O ２ ), oxalic acid (C ２ H ２ O ４ ), acrylic acid (C ３ H ４ O ２ ) or benzoic acid (C ６ H ５ COOH), etc. Sulfonic acids include, for example, ethanesulfonic acid (C ２ H ６ O ３ S) and the like. The organic acid may be a chain compound or a cyclic compound.

[0041] The alcohols mentioned above include, for example, methanol (CH ３ OH), ethanol (C ２ H ５ OH), isopropanol (2-propanol) (CH ３ CH(OH)CH ３ ), ethylene glycol (CH ２ (OH)CH ２ (OH)) or butanol (C ４ H ９ OH) and the like.

[0042] Mercaptans are organic compounds with hydrogenated sulfur (SH) at the end, and are also called thiols or thioalcohols. Examples of the above-mentioned mercaptans include methyl mercaptan (CH ３ SH), ethyl mercaptan (C ２ H ５ SH) or 1-propanethiol (C ３ H ７SH), etc.

[0043] The esters mentioned above are, for example, formates or acetates.

[0044] The above-mentioned ethers include, for example, dimethyl ether ((CH ３ ) ２ O), methyl ethyl ether (C ２ H ５ OCH ３ ) or diethyl ether ((C ２ H ５ ) ２ O) etc.

[0045] The above-mentioned ketones can be, for example, acetone ((CH ３ ) ２ CO), methyl ethyl ketone (C ２ H ５ COCH ３ ) or diethyl ketone ((C ２ H ５ ) ２ CO), etc.

[0046] The aldehydes mentioned above include, for example, acetaldehyde (CH ３ CHO), propionaldehyde (C ２ H ５ CHO) or butanal (butyraldehyde) (C ３ H ７ CHO) etc.

[0047] In the following description, it is assumed that the mixed substance separated by the separation device 2 is a mixed gas containing a plurality of types of gases.

[0048] 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.

[0049] The sealing portion 21 is attached to both longitudinal ends of the support 11 (i.e., the left-right direction in FIG. 3 ) and is a member that covers and seals both longitudinal end faces of the support 11 and the outer surfaces near these end faces. The sealing portion 21 prevents gas and liquid from flowing in and out from these end faces of the support 11. The sealing portion 21 is, for example, a plate-like or film-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 the multiple through holes 111 of the support 11 in the longitudinal direction, and therefore both longitudinal ends of each through hole 111 of the support 11 are not covered by the sealing portion 21. Therefore, gas and liquid can flow in and out of the through holes 111 from these ends.

[0050] 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. 3 ), and a first discharge port 222 is provided at the other longitudinal 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 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 an enclosed space isolated from the space around the housing 22.

[0051] Two seal members 23 are disposed around the entire periphery of the zeolite membrane composite 1 between the outer surface of the zeolite membrane composite 1 and the inner 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 material impermeable to gases and liquids. The seal members 23 are, for example, O-rings made of flexible resin. The seal members 23 are in close contact with the outer surface of the zeolite membrane composite 1 and the inner surface of the housing 22 around the entire periphery. In the example shown in FIG. 3 , the seal members 23 are in close contact with the outer surface of the sealing portion 21 and indirectly with the outer surface of the zeolite membrane composite 1 via the sealing portion 21. The seal members 23 are sealed between the outer surface of the zeolite membrane composite 1 and the inner surface of the housing 22, so that gases and liquids can hardly or completely pass through.

[0052] Supply unit 26 supplies the mixed gas to the internal space of housing 22 via supply port 221. Supply unit 26 includes a pressure-feeding mechanism such as a blower or pump that pressure-feeds the mixed gas toward housing 22. The pressure-feeding mechanism includes, for example, a temperature adjustment unit and a pressure adjustment unit that respectively adjust the temperature and pressure of the mixed gas supplied to housing 22. First recovery unit 27 and second recovery unit 28 include, for example, a storage container that stores the gas drawn out from housing 22, or a blower or pump that transports the gas.

[0053] When a mixed gas is separated, first, a zeolite membrane composite 1 is prepared ( FIG. 4 : step S11). Specifically, the zeolite membrane composite 1 is attached to the inside of the housing 22. Next, a mixed gas containing multiple types of gases with different permeabilities through the zeolite membrane 12 is supplied into the housing 22 by the supply unit 26 as indicated by arrow 251.

[0054] The pressure of the mixed gas supplied from the supply unit 26 to the inside of the housing 22 (i.e., the supply-side pressure, which is the gas pressure on the primary side of the zeolite membrane 12) is, for example, 0.1 MPaG to 20.0 MPaG. The temperature of the mixed gas supplied from the supply unit 26 is, for example, 10°C to 250°C.

[0055] The mixed gas supplied from the supply unit 26 to the housing 22 is introduced into each through-hole 111 of the support 11 (i.e., the inside of the approximately cylindrical zeolite membrane 12) from the left end of the zeolite membrane composite 1 in the drawing. Highly permeable gas, which is a gas with high permeability in the mixed gas, permeates through the zeolite membrane 12 provided on the inner surface of each through-hole 111 and the support 11, and is discharged from the outer surface of the support 11. In this way, the highly permeable gas is separated from the low-permeable gas, which is a gas with low permeability in the mixed gas (step S12).

[0056] The gas discharged from the outer surface of the support 11 (hereinafter referred to as "permeation gas") is introduced to the second recovery section 28 via the second discharge port 223 as indicated by arrow 253, and is recovered by the second recovery section 28. The pressure of the gas recovered by the second recovery section 28 (i.e., the permeation side pressure, which is the gas pressure on the secondary side of the zeolite membrane 12) is, for example, 0.0 MPaG. In other words, the difference between the supply side pressure and the permeation side pressure is, for example, 0.1 MPa to 20.0 MPa. In addition to the above-mentioned high permeation gas, the permeation gas may also include low permeation gas that has permeated the zeolite membrane 12.

[0057] Furthermore, the gas mixture excluding the gas that has permeated the zeolite membrane 12 and the support 11 (hereinafter referred to as "non-permeated gas") passes through each through-hole 111 of the support 11 from left to right in the figure and is recovered by the first recovery section 27 via the first discharge port 222, as indicated by arrow 252. The pressure of the gas recovered by the first recovery section 27 is, for example, approximately the same as the supply-side pressure. In addition to the low-permeability gas described above, the non-permeable gas may also include a high-permeability gas that has not permeated the zeolite membrane 12. The non-permeated gas recovered by the first recovery section 27 may be circulated to the supply section 26 and supplied again into the housing 22, for example.

[0058] The above-described zeolite membrane composite 1 is produced, for example, as follows. First, the support 11 is immersed in a solution in which seed crystals are dispersed, and the seed crystals are attached to the support 11 ( FIG. 5 : step S21). The seed crystals are, for example, zeolite powder produced by hydrothermal synthesis or pulverized zeolite powder. Note that the attachment of the seed crystals to the support 11 may be performed by a method other than the above.

[0059] Next, the support 11 with the attached seed crystals is immersed in the raw material solution to perform hydrothermal synthesis (step S22). As a result, zeolite grows around the seed crystals as nuclei, and a zeolite membrane 12 is formed on the support 11. The raw material solution is prepared by dissolving or dispersing raw materials such as a Si source and a structure-directing agent (hereinafter also referred to as "SDA") in a solvent (e.g., water). The temperature during hydrothermal synthesis is, for example, 110°C to 200°C, and the hydrothermal synthesis time is, for example, 5 hours to 200 hours.

[0060] After the hydrothermal synthesis is completed, the support 11 and the zeolite membrane 12 are washed and dried, and then subjected to a heat treatment in an oxidizing gas atmosphere (step S23). This heat treatment burns and removes the SDA and impurities in the zeolite membrane 12. As a result, a zeolite membrane composite 1 having a zeolite membrane 12 with micropores therethrough is obtained. The oxidizing gas atmosphere is an oxygen-containing atmosphere, such as air. The temperature during the heat treatment is, for example, 200°C or higher and 800°C or lower, preferably 300°C or higher and 600°C or lower, and more preferably 350°C or higher and 500°C or lower. The heat treatment time is, for example, 10 hours to 200 hours.

[0061] The produced zeolite membrane composite 1 is stored, for example, in the atmosphere, until it is actually used (for example, shipped or installed in a separation device). In the zeolite membrane composite 1 immediately after production, a relatively large amount of water molecules in the atmosphere are adsorbed onto the zeolite membrane 12, which has been heated to a relatively high temperature by the heat treatment described above. The water molecules are adsorbed onto the surface of the zeolite membrane 12 opposite to the support 11 (i.e., the outer surface) and onto the surfaces inside the pores of the zeolite membrane 12 (i.e., the inner surface). Furthermore, adsorption of water molecules onto the zeolite membrane 12 occurs relatively frequently even in the zeolite membrane composite 1 that has been stored as is after the heat treatment.

[0062] When a large amount of water molecules are adsorbed onto the zeolite membrane 12, it is considered that the water molecules are adsorbed in a state in which they are stacked in multiple layers in a direction approximately perpendicular to the surface (i.e., in a multilayer adsorption state) on the surface (i.e., the outer and inner surfaces described above) of the zeolite membrane 12. Then, phenomena such as some of the water molecules in the multilayer adsorption state being desorbed from the zeolite membrane 12 or water molecules in the air being further adsorbed onto the water molecules in the multilayer adsorption state may occur, and this may cause variations in the permeation performance (e.g., separation performance and permeation rate) of the zeolite membrane 12 among a plurality of zeolite membrane composites 1 stored as is after the heat treatment as described above.

[0063] Therefore, in the present invention, in order to suppress the above-mentioned variations in the permeation performance of the zeolite membrane 12, the zeolite membrane 12 is treated (hereinafter also referred to as "post-treatment") by the following treatment method (see FIG. 6) according to the present invention. In this treatment method, first, the zeolite membrane 12 that has been heat-treated in the above-mentioned step S23 (see FIG. 5) is prepared (step S31). Preferably, the zeolite membrane composite 1 is prepared immediately after the heat treatment is completed and the temperature is lowered to room temperature (e.g., 25°C).

[0064] Next, a moisture-containing gas having a volumetric moisture content (i.e., volumetric moisture content) of 4000 ppmv or more and 65000 ppmv or less is brought into contact with the zeolite membrane 12 of the zeolite membrane composite 1 to adsorb water molecules onto the zeolite membrane 12 (step S32). The volumetric moisture content of the moisture-containing gas is preferably 5500 ppmv or more, more preferably 7500 ppmv or more. The volumetric moisture content of the moisture-containing gas is preferably 40000 ppmv or less, more preferably 20000 ppmv or less. After the water molecule adsorption process in step S32 is completed, it is believed that the water molecules are adsorbed onto the zeolite membrane 12 in a multilayer adsorption state.

[0065] The moisture-containing gas is, for example, air. In step S32, for example, air having a relative humidity of 25% or more and 80% or less is brought into contact with the zeolite membrane 12, thereby adsorbing water molecules to the zeolite membrane 12. The air is brought into contact with the zeolite membrane 12 by, for example, exposing the zeolite membrane composite 1 to the air. The air contact time with the zeolite membrane 12 is, for example, 1 hour or more. The contact time is, for example, 72 hours or less, preferably 48 hours or less, and more preferably 24 hours or less. By setting the contact time to 1 hour or more, the amount of water molecules necessary for the post-treatment is suitably adsorbed onto the zeolite membrane 12. Furthermore, by setting the contact time to 72 hours or less, the amount of water molecules adsorbed onto the zeolite membrane 12 is prevented from becoming excessive. Furthermore, the time required for step S32 is prevented from becoming too long. Step S32 is performed, for example, in an environment of 15°C or more and 40°C or less under atmospheric pressure.

[0066] In step S32, the air used as the moisture-containing gas includes a gas that is substantially the same as the air, such as air in a natural state to which a trace amount of a substance has been added. Note that a gas other than the air may also be used as the moisture-containing gas.

[0067] After step S32 is completed, the water molecules adsorbed on the zeolite membrane 12 are partially removed (step S33). In other words, in step S33, only a portion of the water molecules adsorbed on the zeolite membrane 12 are removed. Specifically, for example, among the water molecules adsorbed on the zeolite membrane 12 in a multilayer adsorption state, water molecules that are not in direct contact with the zeolite membrane 12 (i.e., water molecules that are adsorbed by stacking on water molecules that are directly adsorbed on the zeolite membrane 12) are desorbed from the zeolite membrane 12 and become non-adsorbed.

[0068] After the dehydration process in step S33 is completed, the water molecules on the surface of the zeolite membrane 12 (i.e., the outer and inner surfaces) are considered to be in a monolayer adsorption state. The monolayer adsorption state refers to a state in which water molecules on the surface of the zeolite membrane 12 are adsorbed to the zeolite membrane 12 in a monolayer without being substantially stacked with other water molecules. The monolayer adsorption state is more stable than the multilayer adsorption state described above, and therefore, the desorption of water molecules adsorbed to the zeolite membrane 12 is suppressed compared to the multilayer adsorption state. Furthermore, because the water molecules in the monolayer adsorption state are adsorbed to each adsorption site on the surface of the zeolite membrane 12, there are essentially no adsorption sites available for new water molecules to adsorb. Therefore, the adsorption of new water molecules to the zeolite membrane 12 is suppressed.

[0069] The partial removal of water molecules in step S33 may be achieved by a process of placing the zeolite membrane composite 1 together with a moisture adsorbent in a container (hereinafter also referred to as "adsorbent treatment"). The container is preferably a sealed container. For example, a sealed container made of two overlapping sheet-like members whose outer peripheral edges are heat-fused (i.e., heat-sealed) over substantially the entire periphery can be used. The zeolite membrane composite 1 is placed in the sealed space of the sheet-like sealed container together with a moisture adsorbent such as silica gel. The sealed space is filled with, for example, an inert gas such as nitrogen or argon (Ar), or the atmosphere.

[0070] The two sheet-like members described above are each, for example, a three-layer laminate sheet. The innermost layer of each sheet-like member (i.e., the layer closest to the sealed space) is formed, for example, from a synthetic resin. Examples of such synthetic resins that can be used include nylon (NY, polyamide (PA)), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), polycarbonate (PC), polystyrene (PS), polyacrylonitrile (PAN), ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), ethylene-methacrylic acid copolymer (EMAA), polyethylene naphthalate (PEN), polyester, cellophane, imide, and polymers thereof.

[0071] The outermost layer of each of the sheet-like members (i.e., the layer that comes into direct contact with the outside air) is made of, for example, a synthetic resin. As the synthetic resin, the same synthetic resin as that used for the innermost layer of the sheet-like member can be used.

[0072] The intermediate layer located between the innermost layer and the outermost layer of each of the sheet-like members is formed by, for example, vapor-depositing a metal material or a ceramic material onto the outer surface of the innermost layer. Examples of metal materials that can be used include aluminum (Al), chromium (Cr), zinc (Zn), gold (Au), silver (Ag), platinum (Pt), and nickel (Ni). Examples of ceramic materials that can be used include alumina and silica. Vapor deposition of the metal material or the ceramic material is performed by, for example, plasma CVD (Chemical Vapor Deposition) or thermal CVD. The intermediate layer improves the airtightness of the sealed container and blocks external light.

[0073] The thickness of the innermost layer of each sheet-like member is, for example, 5 μm to 500 μm, the thickness of the intermediate layer of each sheet-like member is, for example, 10 nm to 100 nm, and the thickness of the outermost layer of each sheet-like member is, for example, 5 μm to 30 μm.

[0074] The partial removal of water molecules in step S33 may be achieved by subjecting the zeolite membrane 12 to a decompression treatment. In this decompression treatment, for example, the zeolite membrane composite 1 is accommodated in a sealed space inside the sealed container or vacuum chamber described above, and is maintained under a vacuum atmosphere for 3 hours or more and 240 hours or less. The time for maintaining the zeolite membrane composite 1 under a vacuum atmosphere is preferably 6 hours or more and 72 hours or less, and more preferably 12 hours or more and 24 hours or less. The pressure of the vacuum atmosphere in this decompression treatment is, for example, 10 ４ Pa or less, preferably 10 ２ Pa or less, and more preferably 10 －１ Pa or less.

[0075] The partial removal of water molecules in step S33 may be achieved by replacing the atmosphere around the zeolite membrane 12 with a dry gas having a lower water volume fraction than the water-containing gas used in step S32 (hereinafter also referred to as a "gas replacement process"). For example, the zeolite membrane composite 1 is accommodated in the sealed space in the sealed container or the sealed space in the housing 22 of the separation device 2, and the atmosphere in the sealed space is replaced with a dry gas, thereby partially removing water molecules adsorbed to the zeolite membrane 12. As the dry gas, for example, an inert gas such as nitrogen or argon, or dry air having a dew point of −20° C. or lower at atmospheric pressure can be used.

[0076] The partial removal of water molecules in step S33 may be achieved by a process of blowing the above-mentioned dry gas onto the zeolite membrane 12 (hereinafter also referred to as a "gas blowing process"). For example, the zeolite membrane composite 1 is housed in the housing 22 of the above-mentioned separation device 2, and a dry gas is supplied into the housing 22 from the supply unit 26, whereby the dry gas is blown onto the zeolite membrane 12, and the water molecules adsorbed on the zeolite membrane 12 are partially removed.

[0077] The partial removal of water molecules in step S33 is achieved by performing one or more of the four processes described above (i.e., adsorbent treatment, decompression treatment, gas replacement treatment, and gas spraying treatment). Note that the partial removal of water molecules in step S33 may be achieved by a process other than the four processes described above, or by combining the other process with one or more of the four processes described above.

[0078] In this way, by performing the above-described post-treatments (steps S31 to S33), it is possible to suppress desorption of water molecules from the zeolite membrane 12 and further adsorption to the zeolite membrane 12. As a result, for example, when a plurality of zeolite membrane composites 1 produced under the same conditions are stored in the atmosphere, it is possible to suppress variations in the permeation performance (e.g., separation performance and permeation rate) of the zeolite membrane 12 due to adsorption and desorption of water molecules to and from the zeolite membrane 12. Furthermore, even when the storage period, etc. of the same zeolite membrane composite is changed, it is possible to suppress variations in the permeation performance of the zeolite membrane 12 in a substantially similar manner.

[0079] In the above-described post-treatment of the zeolite membrane composite 1, if the adsorption of water molecules to the zeolite membrane 12 in step S32 is excessive, the partial removal of water molecules in step S33 may not be performed properly, which may result in a decrease in the permeation rate of the zeolite membrane 12. On the other hand, if the adsorption of water molecules to the zeolite membrane 12 in step S32 is insufficient, the water molecules may be re-adsorbed to the zeolite membrane 12 during, for example, the evaluation of the permeation performance of the zeolite membrane composite 1, which is performed after step S33, which may result in an unstable permeation performance of the zeolite membrane 12. Furthermore, if the removal of water molecules (i.e., dehydration) in step S33 is excessive, the water molecules may be re-adsorbed to the zeolite membrane 12 during, for example, the evaluation of the permeation performance of the zeolite membrane composite 1, which may result in an unstable permeation performance of the zeolite membrane 12.

[0080] As described above, the above-mentioned zeolite membrane treatment method includes a step of preparing a heat-treated zeolite membrane 12 (step S31); a step (step S32) after step S31 of contacting the zeolite membrane 12 with a moisture-containing gas having a volumetric moisture content of 4000 ppmv or more and 65000 ppmv or less to adsorb water molecules onto the zeolite membrane 12; and a step (step S33) after step S32 of partially removing the water molecules adsorbed onto the zeolite membrane 12.

[0081] In this way, the zeolite membrane 12 is temporarily exposed to a moisture-containing gas to intentionally adsorb water molecules onto the zeolite membrane 12, and then excess water molecules adsorbed onto the zeolite membrane 12 are removed, thereby allowing water molecules to exist in a monolayer adsorption state on the surface of the zeolite membrane 12 (i.e., the outer and inner surfaces described above). As described above, a monolayer adsorption state is more stable than a multilayer adsorption state. Furthermore, because water molecules in a monolayer adsorption state are adsorbed to each adsorption site on the surface of the zeolite membrane 12, there are essentially no adsorption sites available for new water molecules to adsorb. Therefore, in the zeolite membrane 12 treated by the above-described zeolite membrane treatment method (steps S31 to S33), desorption of adsorbed water molecules is suppressed, and adsorption of new water molecules is also suppressed. As a result, the permeation performance of the zeolite membrane 12 can be stabilized, and the zeolite membrane 12 can be stored in a state where the permeation performance is stable.

[0082] Preferably, in step S33, the water molecules adsorbed to the zeolite membrane 12 are partially removed by performing one or more of the following processes: reducing the pressure on the zeolite membrane 12; substituting the atmosphere around the zeolite membrane 12 with a dry gas having a lower water volume fraction than the water-containing gas; spraying the dry gas onto the zeolite membrane 12; and housing the zeolite membrane 12 together with a moisture adsorbent in a container. This allows the excess water molecules adsorbed to the zeolite membrane 12 in step S32 to be suitably removed.

[0083] More preferably, in step S33, a pressure reduction treatment is performed on the zeolite membrane 12, and the zeolite membrane 12 is maintained in a vacuum atmosphere for 3 hours or more and 240 hours or less during the pressure reduction treatment. This makes it possible to more effectively remove excess water molecules adsorbed to the zeolite membrane 12 in step S32. Specifically, by maintaining the zeolite membrane composite 1 in a vacuum atmosphere for 3 hours or more, excess water molecules can be prevented from remaining on the surface of the zeolite membrane 12. Furthermore, by maintaining the maintenance time for 240 hours or less, excess removal of water molecules adsorbed to the zeolite membrane 12 can be prevented.

[0084] As described above, the moisture-containing gas is preferably atmospheric air. This allows water molecules to be suitably adsorbed onto the zeolite membrane 12 in step S32. Furthermore, step S32 can be easily performed. Furthermore, compared with the case where the moisture-containing gas is a gas other than atmospheric air, the costs required for preparing and using the moisture-containing gas can be reduced.

[0085] More preferably, in step S32, the zeolite membrane 12 is exposed to air having a relative humidity of 25% or more and 80% or less for 1 hour or more and 72 hours or less, thereby adsorbing water molecules to the zeolite membrane 12. This allows water molecules to be more suitably adsorbed to the zeolite membrane 12. Specifically, by setting the relative humidity to 25% or more, a sufficient amount of water molecules can be adsorbed to the zeolite membrane 12. Furthermore, by setting the relative humidity to 80% or less, excessive adsorption of water molecules to the zeolite membrane 12 can be suppressed. By setting the contact time of the air to the zeolite membrane 12 to 1 hour or more, a sufficient amount of water molecules can be adsorbed to the zeolite membrane 12. Furthermore, by setting the contact time of the air to the zeolite membrane 12 to 72 hours or less, excessive adsorption of water molecules to the zeolite membrane 12 can be suppressed.

[0086] Preferably, the maximum number of rings in the zeolite constituting the zeolite membrane 12 is 10 or less. In such a zeolite membrane 12, the average pore size is relatively small, and therefore the adsorption of water molecules onto the pore surfaces has a relatively large effect on the permeation performance. As described above, the zeolite membrane treatment method shown in steps S31 to S33 can control the adsorption of water molecules onto the zeolite membrane 12 and stabilize the permeation performance of the zeolite membrane 12. Therefore, this treatment method is particularly suitable for treating the zeolite membrane 12, whose permeation performance is relatively greatly affected by the adsorption of water molecules.

[0087] Next, with reference to Tables 1 and 2, the relationship between the post-treatment of the zeolite membrane 12 (steps S31 to S33) and the stabilization of permeation performance will be described.

[0088]

[0089]

[0090] In Examples 1 to 4 and Comparative Examples 1 to 10 in Tables 1 and 2, the stability of the permeation performance of the zeolite membrane 12 was evaluated using the coefficient of variation of the permeation rate of the highly permeable gas and the coefficient of variation of the separation ratio. Specifically, when the coefficient of variation of the permeation rate of the highly permeable gas was 0.15 or less and the coefficient of variation of the separation ratio was 0.15 or less, the permeation performance of the zeolite membrane 12 was judged to be stable. On the other hand, when the coefficient of variation of the permeation rate of the highly permeable gas was greater than 0.15 and / or the coefficient of variation of the separation ratio was greater than 0.15, the permeation performance of the zeolite membrane 12 was judged to fluctuate greatly and the stability of the permeation performance of the zeolite membrane 12 was judged to be insufficient.

[0091] The permeation rate of the highly permeable gas was determined by supplying a mixed gas to the zeolite membrane composite 1 in the separation device 2 and measuring the permeation rate (permeance) of the highly permeable gas permeating the zeolite membrane 12 per unit membrane area and unit pressure difference. The coefficient of variation of the permeation rate of the highly permeable gas (hereinafter also referred to as the "permeation rate variation coefficient") was determined by repeating the measurement of the permeation rate five times and dividing the standard deviation of the measured values ​​by the arithmetic mean of the measured values. The separation ratio was determined by supplying a mixed gas to the zeolite membrane composite 1 in the separation device 2 and dividing the permeation rate of the highly permeable gas permeating the zeolite membrane 12 per unit membrane area and unit pressure difference by the permeation rate of the low permeable gas permeating the zeolite membrane 12 per unit membrane area and unit pressure difference. The coefficient of variation of the separation ratio (hereinafter also referred to as the "separation ratio variation coefficient") was determined by repeating the measurement of the separation ratio five times and dividing the standard deviation of the measured values ​​by the arithmetic mean of the measured values. When evaluating the permeation performance of the zeolite membrane 12, the pressure and temperature of the mixed gas supplied from the supply unit 26 of the separation device 2 were 0.3 MPaG and 25°C, respectively.

[0092] In Example 1, the type of zeolite constituting the zeolite membrane 12 is DDR type. The moisture-containing gas brought into contact with the zeolite membrane 12 in the water molecule adsorption treatment in step S32 is atmospheric air, and the volumetric moisture content, temperature, and relative humidity of the moisture-containing gas are 11680 ppmv, 20°C, and 50%, respectively. The contact time of the moisture-containing gas with the zeolite membrane 12 is 12 hours. The dehydration treatment in step S33 was performed by the above-mentioned decompression treatment. The pressure in the decompression treatment, and the retention time and retention temperature of the zeolite membrane composite 1 under reduced pressure were 10 －１ Pa, 24 hours and 22° C. The reduced pressure treatment was carried out using the above-mentioned sheet-like sealed container.

[0093] The permeation performance of the zeolite membrane 12 was evaluated using CO ２ and CH ４ In this mixed gas, CO ２ is a highly permeable gas, and CH ４ is a low permeability gas. ２ The concentration of is 50% by volume, and CH ４The concentration of zeolite membrane 12 was 50% by volume. The coefficient of variation of the permeation rate was 0.02, and the coefficient of variation of the separation ratio was 0.07. Therefore, the permeation performance of the zeolite membrane 12 was considered to be stable, and the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "good."

[0094] Example 2 was the same as Example 1, except that the volumetric moisture content, temperature, and relative humidity of the moisture-containing gas in the water molecule adsorption treatment in step S32 were 4226 ppmv, 15°C, and 25%, respectively. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.08 and 0.13, respectively, and the stability of the permeation performance of the zeolite membrane 12 was evaluated as "good."

[0095] Example 3 was the same as Example 1, except that the volumetric moisture content, temperature, and relative humidity of the moisture-containing gas in the water molecule adsorption treatment in step S32 were 61920 ppmv, 40°C, and 80%, respectively. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.10 and 0.12, respectively, and the stability of the permeation performance of the zeolite membrane 12 was evaluated as "good."

[0096] Example 4 is the same as Example 1, except that the dehydration treatment in step S33 was performed by gas replacement treatment. The gas replacement treatment was performed in the above-mentioned separation device 2, and nitrogen gas was used as the dry gas. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.04 and 0.09, respectively, and the stability of the permeation performance of the zeolite membrane 12 was evaluated as "good."

[0097] Example 5 is the same as Example 1, except that the dehydration treatment in step S33 was performed by a gas blowing treatment. The gas blowing treatment was performed in the above-mentioned separation device 2, and dry air with an atmospheric dew point of -20°C was used as the dry gas. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.03 and 0.10, respectively, and the stability of the permeation performance of the zeolite membrane 12 was evaluated as "good."

[0098] Example 6 was the same as Example 1, except that the dehydration treatment in step S33 was performed using an adsorbent treatment. The adsorbent treatment was performed using the above-mentioned sheet-like sealed container, and silica gel was used as the adsorbent. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.04 and 0.08, respectively, and the stability of the permeation performance of the zeolite membrane 12 was evaluated as "good."

[0099] In Example 7, the type of zeolite constituting the zeolite membrane 12 is MFI type, and the permeation performance of the zeolite membrane 12 is evaluated using N ２ and SF ６ This is the same as Example 1, except that a mixed gas containing N ２ is a highly permeable gas, and SF ６ is a low permeable gas. ２ The concentration of SF is 80% by volume. ６ The concentration of was 20% by volume. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.04 and 0.13, respectively, and the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "good."

[0100] Example 8 is the same as Example 1, except that the type of zeolite constituting the zeolite membrane 12 is CHA type. The coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were 0.05 and 0.09, respectively, and the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "good."

[0101] Comparative Example 1 was the same as Example 1, except that the water molecule adsorption treatment in step S32 and the dehydration treatment in step S33 were not performed. The permeation rate variation coefficient was 0.15, and the separation ratio variation coefficient was 0.50. In Comparative Example 1, the separation ratio variation coefficient was greater than 0.15, resulting in a large variation in the separation ratio. Therefore, it is considered that the permeation performance of the zeolite membrane 12 was not stabilized, and the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0102] Comparative Example 2 is the same as Example 1 except that the dehydration treatment of step S33 was not performed. The coefficient of variation of the permeation rate was 0.21, and the coefficient of variation of the separation ratio was 0.23. In Comparative Example 2, the coefficient of variation of the permeation rate was greater than 0.15, resulting in a large variation in the permeation rate. Furthermore, the coefficient of variation of the separation ratio was greater than 0.15, resulting in a large variation in the separation ratio. Therefore, it is considered that the permeation performance of the zeolite membrane 12 was not stabilized, and the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0103] Comparative Example 3 was the same as Example 1, except that the volumetric moisture content and relative humidity of the moisture-containing gas in the water molecule adsorption treatment in step S32 were 3480 ppmv and 15%, respectively. The coefficient of variation of the permeation rate was 0.15, and the coefficient of variation of the separation ratio was 0.25. In Comparative Example 3, the coefficient of variation of the separation ratio was greater than 0.15, resulting in a large variation in the separation ratio, and therefore the stability of the permeation performance of the zeolite membrane 12 was evaluated as "poor."

[0104] Comparative Example 4 was the same as Example 1, except that the volumetric moisture content, relative humidity, and temperature of the moisture-containing gas in the water molecule adsorption treatment in step S32 were 70,200 ppmv, 90%, and 40°C, respectively. The coefficient of variation of the permeation rate was 0.24, and the coefficient of variation of the separation ratio was 0.27. In Comparative Example 4, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were large, and the variations in the permeation rate and the separation ratio were large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0105] Comparative Example 5 was the same as Example 1, except that the water molecule adsorption treatment of step S32 was not performed. The coefficient of variation of the permeation rate was 0.14, and the coefficient of variation of the separation ratio was 0.23. In Comparative Example 5, the coefficient of variation of the separation ratio was large, and the variation in the separation ratio was large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0106] Comparative Example 6 was the same as Comparative Example 5, except that the dehydration treatment in step S33 was carried out by the same gas replacement treatment as in Example 4. The coefficient of variation of the permeation rate was 0.18, and the coefficient of variation of the separation ratio was 0.23. In Comparative Example 6, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were large, and the variations in the permeation rate and the separation ratio were large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0107] Comparative Example 7 was the same as Comparative Example 5, except that the dehydration treatment in step S33 was performed by the same gas blowing treatment as in Example 5. The coefficient of variation of the permeation rate was 0.19, and the coefficient of variation of the separation ratio was 0.39. In Comparative Example 7, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were large, and the variations in the permeation rate and the separation ratio were large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0108] Comparative Example 8 was the same as Comparative Example 5, except that the dehydration treatment in step S33 was performed using the same adsorbent treatment as in Example 6. The coefficient of variation of the permeation rate was 0.20, and the coefficient of variation of the separation ratio was 0.40. In Comparative Example 8, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were large, and the variations in the permeation rate and the separation ratio were large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0109] Comparative Example 9 was the same as Example 7, except that the water molecule adsorption treatment in step S32 and the dehydration treatment in step S33 were not performed. The coefficient of variation of the permeation rate was 0.22, and the coefficient of variation of the separation ratio was 0.31. In Comparative Example 9, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were large, and the variations in the permeation rate and the separation ratio were large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0110] Comparative Example 10 was the same as Example 8, except that the water molecule adsorption treatment in step S32 and the dehydration treatment in step S33 were not performed. The coefficient of variation of the permeation rate was 0.18, and the coefficient of variation of the separation ratio was 0.42. In Comparative Example 10, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio were large, and the variations in the permeation rate and the separation ratio were large, so the evaluation of the stability of the permeation performance of the zeolite membrane 12 was "poor."

[0111] Comparing the above-mentioned Example 1 with Comparative Examples 1, 2, and 5, it can be seen that by performing both the water molecule adsorption treatment in step S32 and the dehydration treatment in step S33, the coefficient of variation of the permeation rate and the coefficient of variation of the separation ratio are reduced, and the permeation performance of the zeolite membrane 12 is stabilized.

[0112] Comparing Example 1 with Comparative Examples 3 and 4, it is found that when the volumetric moisture content of the moisture-containing gas in the water molecule adsorption treatment in step S32 is less than 4000 ppmv and when the volumetric moisture content is 65000 ppmv, the permeation performance of the zeolite membrane 12 varies greatly. Therefore, by setting the volumetric moisture content to 4000 ppmv or more and 65000 ppmv or less, the permeation performance of the zeolite membrane 12 can be stabilized.

[0113] The above-described method for treating the zeolite membrane 12 can be modified in various ways.

[0114] For example, the maximum number of ring members of the zeolite constituting the zeolite membrane 12 may be greater than ten.

[0115] When the air is used as the moisture-containing gas in the water molecule adsorption treatment in step S32, the relative humidity of the air may be less than 25% or more than 80%, and the contact time of the air with the zeolite membrane 12 may be less than 1 hour or more than 72 hours.

[0116] When the zeolite membrane 12 is subjected to a decompression treatment in the dehydration treatment of step S33, the time for which the zeolite membrane 12 is held in a vacuum atmosphere may be less than 3 hours or may be longer than 240 hours.

[0117] The adsorption state of water molecules on the surface of the zeolite membrane 12 does not necessarily have to change from a multilayer adsorption state to a monolayer adsorption state as a result of the dehydration treatment in step S33. For example, the dehydration treatment in step S33 may reduce the number of layers of water molecules adsorbed on the surface of the zeolite membrane 12 (i.e., the layer thickness) while maintaining the multilayer adsorption state of water molecules on the surface of the zeolite membrane 12. Alternatively, the dehydration treatment in step S33 may change the adsorption state from a multilayer adsorption state to a monolayer adsorption state in a portion of the surface of the zeolite membrane 12, while reducing the number of layers of water molecules adsorbed on the surface of the zeolite membrane 12 (i.e., the layer thickness) while maintaining the multilayer adsorption state in other portions of the surface of the zeolite membrane 12.

[0118] In the above-described Examples 1 to 4, the permeation performance of the zeolite membrane 12 was evaluated using CO ２ and CH ４ or a mixture of N ２ and SF ６ However, as described above, the mixed substance separated by the zeolite membrane 12 in the separation device 2 or the like may contain various components. For example, the mixed substance may contain a mixture of H ２ and N, a low permeability gas. ２ The mixed gas may contain H as a main component. ２ and N ２ Gases other than (e.g., NH ３ and / or H ２ O) may be included.

[0119] The zeolite membrane 12 may be a laminated membrane in which a plurality of zeolite membranes formed from different types of zeolite are laminated in the thickness direction, or may be a surface-treated zeolite membrane. In the zeolite membrane composite 1, a membrane of a type different from the zeolite membrane (for example, an inorganic membrane other than a zeolite membrane, such as a silica membrane) may be provided on the zeolite membrane 12 (i.e., on the outer surface of the zeolite membrane 12 opposite to the support 11).

[0120] The configurations of the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0121] 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.

[0122] The present invention can be used in treating zeolite membranes that can be used to separate a wide variety of gas mixtures.

[0123] 12 Zeolite membrane S11 to S12, S21 to S23, S31 to S33 steps

Claims

1. A method for treating a zeolite membrane, comprising: a) preparing a heat-treated zeolite membrane; b) after step a), contacting the zeolite membrane with a moisture-containing gas having a volumetric moisture fraction of 4000 ppmv or more and 65000 ppmv or less to adsorb water molecules onto the zeolite membrane; and c) after step b), partially removing the water molecules adsorbed onto the zeolite membrane.

2. A method for treating a zeolite membrane as set forth in claim 1, wherein in step c), water molecules adsorbed to the zeolite membrane are partially removed by performing one or more of the following processes: reducing the pressure on the zeolite membrane; replacing the atmosphere surrounding the zeolite membrane with a dry gas having a lower moisture volume fraction than the moisture-containing gas; spraying the dry gas onto the zeolite membrane; and placing the zeolite membrane in a container together with a moisture adsorbent.

3. A zeolite membrane treatment method according to claim 2, wherein in step c), a decompression treatment is performed on the zeolite membrane, and in the decompression treatment, the zeolite membrane is maintained in a vacuum atmosphere for 3 hours or more and 240 hours or less.

4. A method for treating a zeolite membrane according to any one of claims 1 to 3, wherein the moisture-containing gas is atmospheric air.

5. A method for treating a zeolite membrane according to claim 4, wherein in step b), the zeolite membrane is brought into contact with air having a relative humidity of 25% or more and 80% or less for 1 hour or more and 72 hours or less, thereby adsorbing water molecules onto the zeolite membrane.

6. A method for treating a zeolite membrane according to any one of claims 1 to 3, wherein the maximum number of rings of the zeolite constituting the zeolite membrane is 10 or less.

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