Separation membrane composite, method for manufacturing separation membrane composite, and separation method

Abstract

A separation membrane composite has a porous support and a separation membrane formed on the support. The separation membrane includes small voids (121). When the surface area of the separation membrane is represented as S m , the area of each 1 small void (121) is represented as S k , and the area of each 1 large void (122) is represented as S p , a small void index I k = (Σ(S k 1.5 )) / (S m 1.5 ) is 10 x 10 ‑15 or more, and a large void index I p = (Σ(S p 2 )) / (S m 2 ) is less than 200 x 10 ‑22 . Accordingly, a high separation ratio can be achieved in the separation membrane composite.

Description

Technical Field

[0001] This invention relates to a separation membrane composite, a method for manufacturing the separation membrane composite, and a separation method using the separation membrane composite.

[0002] [Reference for related applications]

[0003] This application claims priority to Japanese Patent Application JP2020-090315, filed on May 25, 2020, the entire disclosure of which is incorporated herein by reference. Background Technology

[0004] Currently, zeolite membrane composites are made by forming zeolite membranes on porous supports, and various studies and developments are being carried out to target the separation and adsorption of specific molecules using the molecular sieving effect of zeolite.

[0005] For example, a known separation process involves supplying a mixed gas (e.g., a mixture of CO2 and CH4) to a zeolite membrane complex, allowing a highly permeable substance (e.g., CO2) to pass through, thereby separating it from the mixed gas. However, sometimes the separation ratio (i.e., the ratio of the permeation rate of the highly permeable substance to the permeation rate of the low-permeability substance) decreases because low-permeability substances (e.g., CH4) leak out along with the highly permeable substance from defects in the zeolite membrane. Therefore, methods for manufacturing zeolite membranes with fewer defects are proposed in International Publication No. 2014 / 157701 (Document 1) and International Publication No. 2011 / 105511 (Document 2).

[0006] However, even with simply reducing defects in zeolite membranes, achieving a high separation ratio in mixed gas separation under low differential pressure conditions where the difference between the supply and permeation pressures is small can be challenging under high differential pressure conditions where the difference is large. Furthermore, increasing the separation ratio by reducing zeolite membrane defects necessitates thickening the membrane, potentially reducing the permeation rate of highly permeable substances within it. Summary of the Invention

[0007] This invention relates to a separation membrane composite, the purpose of which is to achieve a high separation ratio under both low differential pressure and high differential pressure conditions.

[0008] A preferred embodiment of the present invention relates to a separation membrane composite comprising: a porous support and a separation membrane formed on the support. The separation membrane contains small pores. When the surface area of ​​the separation membrane is expressed as S... m The area of ​​each small gap is expressed as S. k The area of ​​each large gap is represented by S. pWhen, the small void index I represents the existence rate of the small voids. k =(Σ(S) k 1.5 )) / (S m 1.5 ) is 10×10 -15 The above represents the large void index I, which indicates the existence rate of the large voids. p =(Σ(S) p 2 )) / (S m 2 Less than 200×10 -22 .

[0009] Therefore, a high separation ratio can be achieved.

[0010] Preferably, the large porosity index I p Less than 100×10 -22 .

[0011] Preferably, the small void index I k 20×10 -15 above.

[0012] Preferably, the permeation rate of CH4 when supplying a mixed gas containing 50% by volume of CO2 and 50% by volume of CH4 at 25°C is less than 1.9 times the permeation rate when the supply-side pressure is 8.0 MPaG and the permeation-side pressure is 0.0 MPaG.

[0013] Preferably, the separation membrane is a zeolite membrane.

[0014] Preferably, the maximum number of rings in the zeolite constituting the zeolite membrane is 8 or less.

[0015] This invention also relates to a method for manufacturing a separation membrane composite. A preferred embodiment of the invention involves a method for manufacturing a separation membrane composite comprising the following steps: a) preparing a porous support formed by firing; b) heating the support at a pretreatment temperature; c) after step b) washing the support with a fluid; d) after step c) attaching seed crystals to the support; e) immersing the support with the attached seed crystals in a raw material solution, and using hydrothermal synthesis to allow zeolite to grow from the seed crystals, forming a separation membrane on the support. The pretreatment temperature is 400°C or higher and less than 80% of the firing temperature of the support in step a). This enables the achievement of a high separation ratio.

[0016] The present invention also relates to a separation method. A preferred embodiment of the present invention includes the following steps: a) preparing the aforementioned separation membrane composite; b) supplying a mixture containing multiple gases or liquids to the separation membrane composite, causing highly permeable substances in the mixture to permeate through the separation membrane composite, thereby separating them from other substances. Accordingly, a high separation ratio can be achieved.

[0017] Preferably, the mixture comprises one or more substances selected from hydrogen, helium, nitrogen, oxygen, water, water vapor, carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, sulfur oxides, hydrogen sulfide, sulfur fluoride, mercury, arsine, hydrogen cyanide, carbonyl sulfide, C1-C8 hydrocarbons, organic acids, alcohols, thiols, esters, ethers, ketones, and aldehydes.

[0018] The above-mentioned objects, as well as other objects, features, solutions, and advantages, will become clear from the following detailed description of the invention with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of a zeolite membrane composite involved in one embodiment.

[0020] Figure 2 This is a magnified cross-sectional view of a portion of the zeolite membrane complex.

[0021] Figure 3 This is a diagram showing the separation device.

[0022] Figure 4 It is a diagram showing the separation process of a mixture.

[0023] Figure 5 This is a conceptual diagram representing a portion of the surface of a zeolite film.

[0024] Figure 6 This is a diagram illustrating the manufacturing process of the separation membrane complex.

[0025] Figure 7 It is a graph showing the relationship between the total pressure of the supply side and the permeation side and the permeation rate. Detailed Implementation

[0026] Figure 1 This is a cross-sectional view of the separation membrane composite 1 according to one embodiment of the present invention. Figure 2 This is a cross-sectional view showing an enlarged portion of the separation membrane composite 1. The separation membrane composite 1 includes: a porous support 11, and a separation membrane, namely a zeolite membrane 12, formed on the support 11. The zeolite membrane 12 is a membrane obtained by forming at least zeolite in a film-like form on the surface of the support 11, and does not include a membrane obtained by simply dispersing zeolite particles in an organic membrane. In addition, the zeolite membrane 12 may contain two or more types of zeolite with different structures and compositions. Figure 1 In the middle, the zeolite film 12 is depicted with thick lines. Figure 2 In the image, parallel oblique lines are marked on zeolite film 12. Additionally... Figure 2 In the diagram, the thickness of the zeolite membrane 12 is depicted as thicker than it actually is. It should be noted that the separation membrane composite 1 may include separation membranes other than the zeolite membrane 12.

[0027] The support 11 is a porous component that allows gas and liquid to pass through. Figure 1 In the example shown, the support 11 is a columnar body integrally formed and connected, with supports respectively along the length direction (i.e., ...). Figure 1 An integral support body with multiple through holes 111 extending in the left and right directions. Figure 1 In the example shown, the support 11 is generally cylindrical. The cross-section of each through hole 111 (i.e., compartment) perpendicular to the length direction is, for example, generally circular. Figure 1 In the diagram, the diameter of the through hole 111 is depicted as larger than it actually is, and the number of through holes 111 is depicted as fewer than it actually is. A zeolite film 12 is formed on the inner surface of the through hole 111, covering the inner surface of the through hole 111 approximately the entire surface.

[0028] The length of the support 11 (i.e., Figure 1 The length (in the left-right direction) of the support 11 is, for example, 10cm to 200cm. The outer diameter of the support 11 is, for example, 0.5cm to 30cm. The distance between the central axes of adjacent through holes 111 is, for example, 0.3mm to 10mm. The surface roughness (Ra) of the support 11 is, for example, 0.1μm to 5.0μm, preferably 0.2μm to 2.0μm. It should be noted that the shape of the support 11 can be, for example, honeycomb, flat, tubular, cylindrical, prismatic, or polygonal. When the shape of the support 11 is tubular or cylindrical, the thickness of the support 11 is, for example, 0.1mm to 10mm.

[0029] The material of the support 11 can be a chemically stable material used in the process of forming the zeolite film 12 on the surface, and various substances (e.g., ceramics or metals) can be used. In this embodiment, the support 11 is formed from a ceramic sintered body. Examples of ceramic sintered bodies selected as the material of the support 11 include: alumina, silicon dioxide, andalusite, zirconium oxide, titanium dioxide, yttrium oxide, silicon nitride, and silicon carbide. In this embodiment, the support 11 includes at least one of alumina, silicon dioxide, and andalusite.

[0030] The support 11 may contain an inorganic binder. As an inorganic binder, at least one of the following may be used: titanium dioxide, andalusite, easily sinterable alumina, silica, glass frit, clay minerals, and easily sinterable cordierite.

[0031] The average pore size of the support 11 is, for example, 0.01 μm to 70 μm, preferably 0.05 μm to 25 μm. The average pore size of the support 11 near the surface to which the zeolite film 12 is to be formed is 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. For example, the average pore size can be measured using a mercury porosimeter, a pore size distribution measuring instrument, or a nanoscale pore size distribution measuring instrument. Regarding the overall pore size distribution of 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 to which the zeolite film 12 is to be formed is, for example, 20% to 60%.

[0032] The support 11 has 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 of the surface layer, including the surface on which the zeolite film 12 is to be formed, are smaller than the average pore size and sintered particle size of the layers other than the surface layer. The average pore size of the surface layer of the support 11 is, for example, 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. When the support 11 has a multilayer structure, the material of each layer can be the material described above. The materials of the multiple layers forming the multilayer structure can be the same or different.

[0033] The zeolite membrane 12 is a porous membrane with micropores. The zeolite membrane 12 can be used as a separation membrane to separate a specific substance from a mixture of multiple substances using molecular sieving. In the zeolite membrane 12, other substances are less likely to permeate compared to the specific substance. In other words, the permeation rate of other substances through the zeolite membrane 12 is less than the permeation rate of the specific substance.

[0034] 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. If the zeolite membrane 12 is thickened, the separation performance is improved. If the zeolite membrane 12 is thinned, the permeation rate is increased. 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.

[0035] The pore size of the zeolite crystals contained in the zeolite membrane 12 (hereinafter also referred to as the "pore size of the zeolite membrane 12") is 0.2 nm or more and 0.8 nm or less, more preferably 0.3 nm or more and 0.7 nm or less, and even more preferably 0.3 nm or more and 0.45 nm or less. When the pore size of the zeolite membrane 12 is less than 0.2 nm, the amount of substance permeating through the zeolite membrane may decrease; when the pore size of the zeolite membrane 12 is greater than 0.8 nm, the selectivity of the zeolite membrane for substances may be insufficient. The pore size of the zeolite membrane 12 is: the diameter (i.e., the minor axis) of the pores in the direction substantially perpendicular to the maximum diameter of the pores (i.e., the major axis representing the maximum distance between oxygen atoms) of the zeolite crystals constituting the zeolite membrane 12. The pore size of the zeolite membrane 12 is smaller than the average pore size at the surface of the support 11 on which the zeolite membrane 12 is to be disposed.

[0036] When the maximum number of rings in the zeolite constituting the zeolite membrane 12 is n, the short axis of the n-membered ring pores is set as the pore diameter of the zeolite membrane 12. Furthermore, when the zeolite has multiple n-membered ring pores of equal size, the short axis of the n-membered ring pore with the largest short axis is set as the pore diameter of the zeolite membrane 12. It should be noted that an n-membered ring is a portion where the number of oxygen atoms constituting the framework forming the pores is n, and each oxygen atom is bonded to T atoms (described later) to form a ring structure. Additionally, an n-membered ring refers to a portion forming through-holes (channels), excluding portions where through-holes are not formed. An n-membered ring pore is a pore formed by n-membered rings. From the viewpoint of improving selectivity, the maximum number of rings in the zeolite membrane 12 is preferably 8 or less (e.g., 6 or 8).

[0037] The pore size of the zeolite membrane is uniquely determined by the zeolite's skeletal structure and can be solved using the values ​​published in the International Zeolite Society's "Database of Zeolite Structures" [online], URL: http: / / www.iza-structure.org / databases / >.

[0038] The type of zeolite constituting the zeolite membrane 12 is not particularly limited, and can be, for example, AEI type, AEN type, AFN type, AFV type, AFX type, BEA type, CHA type, DDR type, ERI type, ETL type, FAU type (X type, Y type), GIS type, IHW type, LEV type, LTA type, LTJ type, MEL type, MFI type, MOR type, PAU type, RHO type, SOD type, SAT type, etc. When the zeolite is an 8-membered ring zeolite, it can be, for example, AEI type, AFN type, AFV type, AFX type, CHA type, DDR type, ERI type, ETL type, GIS type, IHW type, LEV type, LTA type, LTJ type, RHO type, SAT type, etc. In this embodiment, the zeolite constituting the zeolite membrane 12 is a DDR type zeolite.

[0039] For the zeolite constituting the zeolite film 12, the T atom (i.e., the atom located at the center of the oxygen tetrahedron (TO4) constituting the zeolite) may contain, for example, aluminum (Al). The zeolite constituting the zeolite film 12 may be: a zeolite with only silicon (Si) as the T atom, or a zeolite with both Si and Al as the T atom, an AlPO-type zeolite with Al and phosphorus (P) as the T atom, a SAPO-type zeolite with Si, Al, and P as the T atom, a MAPSO-type zeolite with magnesium (Mg), Si, Al, and P as the T atom, or a ZnAPSO-type zeolite with zinc (Zn), Si, Al, and P as the T atom, etc. A portion of the T atom may be replaced by other elements.

[0040] The zeolite membrane 12 contains, for example, Si. The zeolite membrane 12 may contain any two or more of, for example, Si, Al, and P. The zeolite membrane 12 may contain an alkali metal, such as sodium (Na) or potassium (K). When the zeolite membrane 12 contains both Si 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 elements contained in the zeolite membrane 12. This Si / Al ratio is preferably 5 or more, more preferably 20 or more, and even more preferably 100 or more; the higher the ratio, the better. The Si / Al ratio in the zeolite membrane 12 can be adjusted by adjusting the proportion of Si and Al sources in the raw material solution, as described later.

[0041] Next, refer to Figure 3 and Figure 4 The separation of mixed substances using separation membrane complex 1 is explained. Figure 3 This is a diagram showing the separation device 2. Figure 4 This is a diagram showing the process of separating a mixture using separation device 2.

[0042] In the separation device 2, a mixture containing multiple fluids (i.e., gases or liquids) is supplied to the separation membrane composite 1, causing highly permeable substances in the mixture to permeate through the separation membrane composite 1, thereby separating them from the mixture. The separation purpose in the separation device 2 can be, for example, to extract highly permeable substances (hereinafter also referred to as "highly permeable substances") from the mixture, or to concentrate substances with low permeability (hereinafter also referred to as "lowly permeable substances").

[0043] The mixture (i.e., the mixed fluid) can be a mixture of gases containing multiple gases, a mixture of liquids containing multiple liquids, or a gas-liquid two-phase fluid containing both gases and liquids.

[0044] The mixture contains one or more substances selected from, for example, hydrogen (H2), helium (He), nitrogen (N2), oxygen (O2), water (H2O), water vapor (H2O), carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, ammonia (NH3), sulfur oxides, hydrogen sulfide (H2S), sulfur fluoride, mercury (Hg), arsene (AsH3), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1-C8 hydrocarbons, organic acids, alcohols, thiols, esters, ethers, ketones, and aldehydes. The highly permeable substances mentioned above are, for example, one or more substances selected from, H2, N2, O2, H2O, CO2, and H2S.

[0045] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also known as dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5), which are collectively referred to as NO. X (NOx) gas.

[0046] Sulfur oxides are compounds of sulfur and oxygen. The sulfur oxides mentioned above, such as sulfur dioxide (SO2) and sulfur trioxide (SO3), are collectively referred to as SO42-SO ... X (Sox) gas.

[0047] Sulfur fluorides are compounds of fluorine and sulfur. Examples of sulfur fluorides include, for instance, disulfur difluoride (FSSF, S=SF2), sulfur difluoride (SF2), sulfur tetrafluoride (SF4), sulfur hexafluoride (SF6), or disulfur decafluoride (S2F). 10 )wait.

[0048] Hydrocarbons with C1 to C8 are hydrocarbons with one or more but fewer than eight carbon atoms. Hydrocarbons with C3 to C8 can be any of the following: straight-chain compounds, side-chain compounds, and cyclic compounds. In addition, hydrocarbons with C2 to C8 can be any of the following: saturated hydrocarbons (i.e., hydrocarbons without double or triple bonds in the molecule) and unsaturated hydrocarbons (i.e., hydrocarbons with double and / or triple bonds in the molecule). Hydrocarbons with C1 to C4 are, for example, methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), n-butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), or isobutene (CH2=C(CH3)2).

[0049] The organic acids mentioned above are carboxylic acids or sulfonic acids, etc. Examples of carboxylic acids include formic acid (CH₂O₂), acetic acid (C₂H₄O₂), oxalic acid (C₂H₂O₄), acrylic acid (C₃H₄O₂), or benzoic acid (C₆H₅COOH), etc. Examples of sulfonic acids include ethanesulfonic acid (C₂H₆O₃S), etc. These organic acids can be chain compounds or cyclic compounds.

[0050] 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), etc.

[0051] Thiols are organic compounds with hydrogenated sulfur (SH) at their terminals, and are also known as Thiol or Thioalcohol. Examples of thiols include methanethiol (CH3SH), ethanethiol (C2H5SH), or 1-propanethiol (C3H7SH).

[0052] The esters mentioned above are, for example, formate esters or acetate esters.

[0053] The ethers mentioned above are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3), or diethyl ether ((C2H5)2O), etc.

[0054] The ketones mentioned above are, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO), etc.

[0055] The aldehydes mentioned above include, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO), or butyraldehyde (C3H7CHO).

[0056] In the following description, we will take a mixture of multiple gases as an example, which is a mixture of substances separated by the separation device 2.

[0057] The separation device 2 includes: a separation membrane composite 1, a sealing part 21, an outer cylinder 22, two sealing components 23, a supply part 26, a first recovery part 27, and a second recovery part 28. The separation membrane composite 1, the sealing part 21, and the sealing components 23 are housed inside the outer cylinder 22. The supply part 26, the first recovery part 27, and the second recovery part 28 are disposed outside the outer cylinder 22 and connected to the outer cylinder 22.

[0058] The sealing part 21 is: installed along the length direction of the support 11 (i.e., Figure 3 The sealing portion 21 is a component that seals the two ends of the support body 11 in the left-right direction and covers and seals the two end faces of the support body 11 in the longitudinal direction and the outer surfaces near the two end faces. The sealing portion 21 prevents gas and liquid from flowing in and out from the two end faces of the support body 11. The sealing portion 21 is a plate-shaped or film-shaped component, for example, made of glass or resin. The material and shape of the sealing portion 21 can be appropriately changed. It should be noted that since the sealing portion 21 has multiple openings that overlap with the multiple through holes 111 of the support body 11, the two ends of each through hole 111 in the longitudinal direction of the support body 11 are not covered by the sealing portion 21. Therefore, gas and liquid can flow in and out from the two ends into the through holes 111.

[0059] The shape of the outer cylinder 22 is not particularly limited; for example, it may be a generally cylindrical cylindrical component. The outer cylinder 22 is formed of, for example, stainless steel or carbon steel. The length direction of the outer cylinder 22 is generally parallel to the length direction of the separation membrane composite 1. At one end of the outer cylinder 22 in the length direction (i.e., Figure 3 A supply port 221 is provided at the left end of the outer cylinder 22, and a first discharge port 222 is provided at the other end. A second discharge port 223 is provided on the side of the outer cylinder 22. A supply section 26 is connected to the supply port 221. A first recovery section 27 is connected to the first discharge port 222. A second recovery section 28 is connected to the second discharge port 223. The internal space of the outer cylinder 22 is a sealed space isolated from the space surrounding the outer cylinder 22.

[0060] Two sealing components 23 are arranged circumferentially between the outer surface of the separation membrane composite 1 and the inner surface of the outer cylinder 22 near both ends along the length of the membrane composite 1. Each sealing component 23 is a generally annular component formed of a gas- and liquid-impermeable material. The sealing component 23 is, for example, an O-ring formed of a flexible resin. The sealing components 23 are in close contact with the outer surface of the separation membrane composite 1 and the inner surface of the outer cylinder 22 throughout the entire circumference. Figure 3 In the example shown, the sealing member 23 is in close contact with the outer surface of the sealing portion 21, and is indirectly in close contact with the outer surface of the separation membrane composite 1 through the sealing portion 21. The sealing member 23 is sealed between the outer surface of the separation membrane composite 1 and between the sealing member 23 and the inner surface of the outer cylinder 22, so that gas and liquid can hardly or completely not pass through.

[0061] The supply unit 26 supplies the mixed gas into the interior space of the outer cylinder 22 via the supply port 221. The supply unit 26 includes a pressure conveying mechanism, such as a blower or pump, that pressurizes the mixed gas toward the outer cylinder 22. This pressure conveying mechanism includes, for example, a temperature regulating unit and a pressure regulating unit that adjust the temperature and pressure of the mixed gas supplied to the outer cylinder 22, respectively. The first recovery unit 27 and the second recovery unit 28 include, for example, a storage container for storing the gas discharged from the outer cylinder 22, or a blower or pump for transferring the gas.

[0062] When performing mixed gas separation, firstly, prepare separation membrane complex 1 ( Figure 4 (Step S11). Specifically, the separation membrane composite 1 is installed inside the outer cylinder 22. Next, using the supply unit 26, a mixed gas containing multiple gases with different permeabilities to the zeolite membrane 12 is supplied to the interior of the outer cylinder 22, as shown by arrow 251. For example, the main components of the mixed gas are CO2 and CH4. The mixed gas may contain gases other than CO2 and CH4. The pressure (i.e., supply-side pressure) of the mixed gas supplied from the supply unit 26 to the interior of the outer cylinder 22 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.

[0063] The mixed gas supplied from the supply section 26 to the outer cylinder 22 is introduced from the left end of the separation membrane composite 1 in the figure into each through hole 111 of the support 11. The highly permeable gas in the mixed gas, i.e., the highly permeable substance, permeates through the zeolite membrane 12 and the support 11 disposed on the inner side of each through hole 111, and is thus discharged from the outer side of the support 11. Accordingly, the highly permeable substance (e.g., CO2) is separated from the less permeable gas in the mixed gas, i.e., the low-permeability substance (e.g., CH4) (step S12).

[0064] The gas (hereinafter referred to as "permeable material") discharged from the outer side of the support 11 is introduced into the second recovery unit 28 through the second outlet 223 as shown by arrow 253, and is recovered by the second recovery unit 28. The pressure of the gas recovered by the second recovery unit 28 (i.e., the permeable side pressure) is, for example, 0.0 MPaG. In addition to the high permeability material described above, the permeable material may also contain a low permeability material that permeates from the zeolite membrane 12.

[0065] In addition, gases in the mixed gas other than those permeating through the zeolite membrane 12 and the support 11 (hereinafter referred to as "impermeable substances") pass through the through holes 111 of the support 11 from left to right in the figure, as shown by arrow 252, and are recovered by the first recovery unit 27 via the first discharge port 222. The pressure of the gas recovered by the first recovery unit 27 is, for example, approximately the same as the inlet pressure. The impermeable substances may include, in addition to the low-permeability substances mentioned above, high-permeability substances that do not permeate through the zeolite membrane 12. The impermeable substances recovered by the first recovery unit 27 can be circulated to, for example, the supply unit 26 and supplied back into the outer cylinder 22.

[0066] As described above, conventionally, zeolite membrane 12 contains voids (also called defects) through which low-permeability substances, which are difficult to pass through the fine pores of the zeolite, can pass. Therefore, during mixed gas separation, the low-permeability substances passing through these voids mix with the permeable substances passing through the zeolite membrane 12. In other words, these voids cause a decrease in the separation ratio of the zeolite membrane 12 (i.e., the value obtained by dividing the permeation rate of the high-permeability substances by the permeation rate of the low-permeability substances). This decrease in the separation ratio is more significant under high differential pressure conditions where the difference between the supply-side pressure and the permeation-side pressure is relatively large.

[0067] The inventors of this application conducted in-depth research and obtained the following insight: the pores of the aforementioned zeolite membrane 12 can be divided into two types of pores with different degrees of influence on the reduction of the separation ratio. Specifically, the pores of the zeolite membrane 12 can be divided into a first pore and a second pore. The first pore exhibits approximately the same permeation rate for low-permeability materials under both low differential pressure conditions (e.g., differential pressure 0.3 MPa) and high differential pressure conditions (e.g., differential pressure 8.0 MPa). The second pore exhibits a significantly higher permeation rate under high differential pressure conditions than under low differential pressure conditions. Hereinafter, the first pore will be referred to as the "small pore," and the second pore as the "large pore." Furthermore, in this application, "low differential pressure conditions" refers to a differential pressure (i.e., the value obtained by subtracting the permeation pressure from the supply side pressure) that is less than 1 MPa; "high differential pressure conditions" refers to a differential pressure that is 1 MPa or higher.

[0068] Figure 5 This is a diagram that conceptually represents a portion of the surface of the zeolite film 12. Figure 5 In the middle, parallel oblique lines are marked on the surface of zeolite film 12. Figure 5 In the example shown, the zeolite membrane 12 contains multiple small pores 121 and multiple large pores 122. In the small pores 121, the gas diffusion mechanism is Knudsen flow, and the gas permeation velocity F... k (mol / (m) 2The gas diffusion mechanism in the large pore 122 is a Poiseuille flow, and the gas permeation velocity F is... p (mol / (m) 2 The permeation velocity of the gas, F (·Pa·sec), is represented by the following mathematical formula 2. k F p The permeation flow rate of gas per unit area and per unit differential pressure.

[0069] [Mathematical Expression 1]

[0070]

[0071] [Mathematical Expression 2]

[0072]

[0073] In mathematical formula 1, r k Let r be the radius (m) of a small pore 121, L be the representative length (i.e., the film thickness of the zeolite film 12) of the small pore 121 (m), M be the molar mass of the gas (kg / mol), R be the gas constant (J / (K·mol)), and T be the absolute temperature (K). k It is: the radius of the small void 121 when the surface is viewed from a direction perpendicular to the surface of the zeolite film 12, approximating it as a circle. In mathematical formula 2, r p Let L be the radius of a large pore 122 (m), L be the representative length of the large pore 122 (i.e., the film thickness of the zeolite film 12) (m), μ be the viscosity of the gas (Pa·sec), R be the gas constant (J / (K·mol)), T be the absolute temperature (K), and P be the velocity of the gas. h For supply-side pressure (PaA), P l The permeable lateral pressure (PaA). The radius r of the large pore 122. p Yes: The radius of the large void 122 when it is approximated as a circle when viewed from a direction perpendicular to the surface of the zeolite film 12. It should be noted that in mathematical formulas 1 and 2, the representative length L of the small void 121 and the representative length L of the large void 122 are set as the film thickness of the zeolite film 12. However, the actual lengths of the small void 121 and the large void 122 are not necessarily equal to the film thickness of the zeolite film 12.

[0074] The absolute value j of the permeation flow rate per unit differential pressure of the gas permeating through a small gap 121 k (mol / (Pa·sec)), as shown in Equation 3 below, through velocity F k Multiply by the area S of the small gap 121 k (=π·r) k2 The solution is to calculate the absolute value j of the permeation flow rate per unit differential pressure of the gas permeating through a large gap 122. p (mol / (Pa·sec)), as shown in the following mathematical formula 4, through velocity F p Multiply by the area S of the large gap 122 p (=π·r) p 2 The solution is then performed. Below, the absolute value j of the permeable flow rate per unit differential pressure is given. k j p It is also simply referred to as "through flow j" k j p ".

[0075] [Mathematical Expression 3]

[0076]

[0077] [Mathematical Expression 4]

[0078]

[0079] As shown in mathematical formulas 1 and 3, the transmission velocity F of the small gap 121 k and through flow j k It is unaffected by supply-side pressure and permeation-side pressure. On the other hand, as shown in Equations 2 and 4, the permeation velocity F of the large gap 122... p and through flow j p It increases with the increase of supply-side pressure and permeation-side pressure.

[0080] The inventors of this application have also realized that the area of ​​each of the large pores 122 and small pores 121 in the zeolite membrane 12 affects the separation ratio and the permeation rate of highly permeable substances in the separation membrane composite 1. Specifically, if the total area of ​​the large pores 122 in the zeolite membrane 12 increases, the separation ratio of highly permeable substances to low-permeability substances in the separation membrane composite 1 decreases. Furthermore, if the area of ​​the small pores 121 in the zeolite membrane 12 is reduced, the zeolite membrane 12 becomes thicker, and the permeation rate of highly permeable substances in the separation membrane composite 1 decreases.

[0081] Therefore, the inventors of this application focus on the large porosity index I, which represents the presence rate of large porosity 122 in the zeolite film 12. p and the small void index I, which represents the presence rate of small voids 121 in the zeolite film 12. k For the small void index I k Let the surface area of ​​the zeolite membrane 12 be S. m (m) 2Let S be the area of ​​each small gap 121 (i.e., the area of ​​each small gap 121). k (m) 2 ), is represented by the following mathematical formula 5. Furthermore, for the large porosity index I... p Let the surface area of ​​the zeolite membrane 12 be S. m (m) 2 Let S be the area of ​​each large gap 122 (i.e., the area of ​​each large gap 122). p (m) 2 ), is represented by the following mathematical expression 6.

[0082] [Mathematical Expression 5]

[0083]

[0084] [Mathematical Expression 6]

[0085]

[0086] The surface area S of zeolite film 12 m for Figure 2 The surface area S of the zeolite film 12 exposed in the through hole 111 is the total surface area of ​​the zeolite film 12. In other words, the surface area S of the zeolite film 12 is... m The total area of ​​the region where the zeolite film 12 is formed. Figure 5 In the example shown, the surface area of ​​the zeolite membrane 12 is the area of ​​the entire rectangular region in the figure, and also includes the area of ​​multiple large voids 122 and multiple small voids 121.

[0087] In the separation membrane complex 1, the large porosity index I p Less than 200×10 -22 By reducing the large porosity 122 of the zeolite membrane 12 in this way, a high separation ratio of the separation membrane composite 1 can be achieved. Preferably, the porosity index I... p Less than 100×10 -22 Therefore, the separation ratio is improved. Furthermore, in the separation membrane complex 1, the small porosity index I... k 10×10 -15 The above describes how increasing the number of small pores 121 in the zeolite membrane 12 to a certain extent can suppress the decrease in the permeation rate of highly permeable substances in the separation membrane complex 1. Preferably, the small pore index I... k 20×10 -15 The above. Therefore, the reduction in the permeation rate of highly permeable materials is further suppressed. Small porosity index I k There is no specific upper limit for the small gap index I. k If the value is too high, it may lead to a decrease in the aforementioned separation ratio. From the perspective of suppressing this decrease in the separation ratio, the small void index I...k Preferably 5000×10 -15 the following.

[0088] Next, refer to Figure 6 An example of the manufacturing process of the separation membrane composite 1 will be described. When manufacturing the separation membrane composite 1, firstly, a porous support 11 is formed for later use (step S21). In step S21, for example, raw materials including aggregate material, pore-forming agent, and binder containing the support 11 are prepared and mixed. Next, water is added to the raw materials, and the mixture is kneaded using a kneader to prepare a blank. Next, the blank is formed using an extrusion molding machine or the like to obtain a material having multiple through holes 111 (see reference). Figure 1 The molded body is formed by means of molding other than extrusion molding. It should be noted that the molded body can be obtained using molding methods other than extrusion molding. After drying and degreasing, the molded body is fired. Accordingly, the aforementioned support 11 is formed. The firing temperature (i.e., firing temperature) of the outermost layer of the molded body is, for example, 1200°C to 1300°C, and in this embodiment, it is 1250°C. The firing time is, for example, 6 hours to 10 hours. The firing conditions of the molded body can be appropriately changed.

[0089] After step S21 is completed, the support 11 is heated at a pretreatment temperature (step S22). This allows impurities such as organic matter adhering to the support 11 to be burned and / or decomposed and removed. For example, the heating treatment in step S22 is performed in the atmosphere. The pretreatment temperature is preferably 400°C or higher, and less than 80% of the firing temperature of the support 11 in step S21. It should be noted that this ratio (%) of pretreatment temperature to firing temperature is a percentage in degrees Celsius. If the pretreatment temperature is less than 400°C, the burning and decomposition of organic matter may be insufficient. Furthermore, if the pretreatment temperature is 80% or higher of the firing temperature of the support 11, firing of the support 11 may occur, adversely affecting the formation of the zeolite film 12 in step S26. The heating time in step S22 is, for example, 2 hours to 36 hours.

[0090] After step S22 is completed, the support 11 is cleaned using a fluid (step S23). This removes residues such as organic matter from combustion and decomposition in step S22 from the support 11. The fluid can be a liquid such as water or alcohol, or a gas such as air. Alternatively, both liquid and gas can be used to clean the support 11. For example, 100 mL of ethanol is flowed over the surface of the support 11 for a first cleaning treatment, followed by a second cleaning treatment using a dryer or similar device to circulate air over the surface of the support 11 for 1 minute.

[0091] After step S23 is completed, seed crystals for forming zeolite film 12 are generated for later use (step S24). During seed crystal generation, raw materials such as Si source and structure-directing agent (hereinafter also referred to as "SDA") are dissolved or dispersed in a solvent to prepare a raw material solution for the seed crystals. Next, hydrothermal synthesis of this raw material solution is performed, and the resulting crystals are washed and dried to obtain zeolite powder (e.g., DDR-type zeolite). This zeolite powder can be used directly as seed crystals, or it can be processed by pulverization or the like to obtain seed crystals. It should be noted that step S24 can be performed simultaneously with steps S21 to S23, or it can be performed before steps S21 to S23.

[0092] Next, seed crystals are attached to the inner surface of the through-hole 111 of the support 11 (step S25). For example, the seed crystals are dispersed in a solvent (e.g., water or an alcohol such as ethanol) to obtain a dispersion, and the porous support 11 is immersed in the dispersion, thereby attaching the seed crystals to the support 11. The immersion of the support 11 in the dispersion can be repeated multiple times. Alternatively, the seed crystals can be attached to the support 11 using other methods different from those described above.

[0093] The support 11 with seed crystals attached is immersed in a raw material solution. For example, the raw material solution is prepared by dissolving a Si source and SDA in a solvent. The composition of the raw material solution is, for example, 1.0SiO2:0.015SDA:0.12(CH2)2(NH2)2. The solvent for the raw material solution can be an alcohol such as water or ethanol. When water is used as the solvent, the molar ratio of SDA to water in the raw material solution is preferably 0.01 or less. Alternatively, the molar ratio of SDA to water in the raw material solution is preferably 0.00001 or more. The SDA in the raw material solution is, for example, an organic compound. For example, 1-adamantaneamine can be used as the SDA.

[0094] Then, using the aforementioned seed crystals as nuclei, DDR-type zeolite is grown via hydrothermal synthesis, thereby forming a DDR-type zeolite film 12 on the support 11 (step S26). The hydrothermal synthesis temperature is preferably 120–200°C, for example, 160°C. The hydrothermal synthesis time is preferably 5–100 hours, for example, 30 hours.

[0095] After hydrothermal synthesis, the support 11 and zeolite membrane 12 are washed with pure water. The washed support 11 and zeolite membrane 12 are then dried at, for example, 80°C. After drying, the zeolite membrane 12 is heated to almost completely burn away the SDA in it, thus opening up the micropores within the zeolite membrane 12 (step S27). Based on this, the above-described separation membrane composite 1 is obtained.

[0096] As described above, in the manufacturing of the separation membrane composite 1, organic matter, residues, etc., are removed from the surface of the support 11 using steps S22 to S23. Therefore, in step S25, the seed crystals can be uniformly and densely attached to the surface of the support 11. Thus, during the formation of the zeolite membrane 12 in step S26, the formation of large voids 122 due to organic matter, residues, etc., hindering seed crystal attachment can be suppressed. On the other hand, since the formation of small voids 121 depends on the hydrothermal synthesis time and temperature in step S26, the total area of ​​small voids 121 does not change significantly regardless of whether steps S22 to S23 are performed.

[0097] Next, referring to Table 1, the porosity index I in the separation membrane composite 1 of Examples 1-5 is analyzed. p and small void index I k The relationship between transmission performance and the transmission performance will be explained. The same applies to Comparative Examples 1 and 2.

[0098] [Table 1]

[0099]

[0100] The large porosity index I of the separation membrane complex 1 p and small void index I k The solution was obtained using the following method. First, using the separation device 2 described above, CF4 was supplied to the separation membrane composite 1, and the permeation flow rate (mol / (Pa·sec)) of CF4 per unit differential pressure through the zeolite membrane 12 and the support 11 was measured. Then, the permeation flow rate of CF4 per unit differential pressure was repeatedly measured by changing the supply-side pressure of the separation device 2 a predetermined number of times. Specifically, the permeation flow rate of CF4 per unit differential pressure was measured under supply-side pressures of 0.2 MPaA, 0.4 MPaA, 0.6 MPaA, and 0.8 MPaA. The temperature of the supplied CF4 was 25°C, and the permeation-side pressure was 0.1 MPaA.

[0101] Then, as Figure 7 As shown, the horizontal axis is set as the total pressure of the supply side pressure and the permeation side pressure (P). h +P l (PaA), set the vertical axis to the permeation flow rate (mol / (Pa·sec)) per unit differential pressure of CF4 mentioned above, plot the measurement results, and solve for the slope and intercept of the approximate straight line 91 obtained by the least squares method.

[0102] CF4 does not easily permeate through the fine pores of the DDR-type zeolite constituting the zeolite membrane 12. Therefore, it can be considered that it permeates through the large pores 122 and small pores 121 of the zeolite membrane 12. Thus, the permeation flow rate J of CF4 per unit differential pressure is expressed by mathematical formula 7.

[0103] [Mathematical Expression 7]

[0104]

[0105] The slope of the approximate line 91 is the coefficient of the first term on the right side of mathematical formula 7, and the intercept of the approximate line 91 is the second term on the right side of mathematical formula 7. Therefore, based on the intercept and slope of the approximate line 91, the small gap index I shown in mathematical formulas 5 and 6 can be solved. k and large void index I p The representative length L in mathematical formula 7 is, as described above, the thickness of zeolite membrane 12. The thickness of zeolite membrane 12 is defined as the arithmetic mean of the thickness obtained by observing three SEM (scanning electron microscope) images of the cross-section of the separation membrane complex 1. The viscosity μ of CF4 is calculated using the Chapman-Enskog formula. The parameters used for calculating the viscosity μ are those described in the 7th revised edition of the Chemical Engineering Handbook, pp. 69-71.

[0106] It should be noted that the solution for the large porosity index I... p and small void index I k In this case, CF4 can be replaced by a gas that does not permeate the zeolite membrane 12 but can permeate through the large gaps 122 and the small gaps 121. Alternatively, the permeation pressure or the supply pressure and the permeation pressure can be changed instead of the supply pressure.

[0107] The CH4 permeation rate ratio in Table 1 is calculated as follows: In separation unit 2, the supply-side pressure is varied, and a mixed gas containing 50% by volume CO2 and 50% by volume CH4 at 25°C is supplied to separation membrane composite 1. The measured CH4 permeation flow rate (mol / sec) is used to determine the CH4 permeation rate ratio in Table 1. Specifically, first, the value obtained by subtracting the partial pressure of CH4 on the permeation side from the partial pressure of CH4 on the supply side (i.e., the differential pressure of CH4 partial pressures) (Pa) is divided by the measured CH4 permeation flow rate (mol / sec), thereby determining the CH4 permeation flow rate per unit differential pressure (mol / (Pa·sec)). Then, the CH4 permeation rate ratio is obtained by dividing the CH4 permeation flow rate per unit differential pressure at a supply-side pressure of 8.0 MPaG by the CH4 permeation flow rate per unit differential pressure at a supply-side pressure of 0.3 MPaG. The permeation-side pressure is 0.0 MPaG. It should be noted that the permeation flow rate of CH4 per unit differential pressure is divided by the surface area of ​​the zeolite membrane 12 to calculate the permeation velocity of CH4 (i.e., the permeation flow rate of gas per unit area and per unit differential pressure) (mol / (m²). 2·Pa·sec). In other words, the CH4 permeation rate ratio is obtained by dividing the CH4 permeation rate under high differential pressure conditions (differential pressure 8.0MPa) by the CH4 permeation rate under low differential pressure conditions (differential pressure 0.3MPa).

[0108] The relative CO2 permeation rate in Table 1 is calculated as follows: with the supply-side pressure at 0.3 MPaG and the permeation-side pressure at 0.0 MPaG, a mixed gas containing 50 vol% CO2 and 50 vol% CH4 at 25°C is supplied to the separation membrane composite 1. The permeation flow rate of CO2 per unit differential pressure is measured at this time and divided by the permeation flow rate in Example 1 to obtain the relative CO2 permeation rate in Table 1.

[0109] The separation membrane composites 1 of Examples 1-5 were manufactured using the manufacturing method given in steps S21-S27 above. In Example 1, the pretreatment temperature in step S22 was 500°C and the heating time was 24 hours. In Example 2, the pretreatment temperature in step S22 was 450°C and the heating time was 18 hours. In Example 3, the pretreatment temperature in step S22 was 420°C and the heating time was 12 hours. In Example 4, the pretreatment temperature in step S22 was 400°C and the heating time was 4 hours. In Example 5, the pretreatment temperature and heating time in step S22 were the same as in Example 2, so that the large porosity index I... p The hydrothermal synthesis time of the zeolite membrane 12 in step S26 was extended to the same extent as in Example 1. In Comparative Examples 1 and 2, the heating treatment in step S22 and the cleaning treatment in step S23 were omitted; otherwise, the separation membrane composite 1 was manufactured using a manufacturing method substantially the same as in Examples 1 to 5. In Comparative Example 2, the hydrothermal synthesis time of the zeolite membrane 12 in step S26 was extended, resulting in a larger porosity index I. p It is to the same extent as Example 1.

[0110] In Examples 1-5, the large void index I p 3.74×10 -22 ~169×10 -22 (i.e., less than 200×10) -22 Small porosity index I k It is 14.7×10 -15 ~59.7×10 -15 (i.e., 10×10) -15 (Above). The CH4 permeation rate is as low as 0.80–1.2 (i.e., less than 1.9), and CH4 leakage is suppressed even under high differential pressure conditions. Therefore, a high separation ratio is achieved in separation membrane composite 1. In addition, the relative CO2 permeation rate is as high as 0.6–1.0. Therefore, high separation capacity is achieved in separation membrane composite 1.

[0111] In Examples 1-3 and 5, the large porosity index I p 3.74×10 -22 ~62.8×10 -22 (i.e., less than 100×10) -22 The porosity index I of Example 4 is smaller than that of Example 4. p =169×10 -22 The CH4 permeation rate ratios in Examples 1-3 and 5 were 0.80-1.1, which was lower than the CH4 permeation rate ratio of 1.2 in Example 4. That is, in Examples 1-3 and 5, CH4 leakage under high differential pressure conditions was further suppressed.

[0112] In Examples 1-4, the small void index I k 28.0×10 -15 ~59.7×10 -15 (i.e., 20×10) -15 (above), greater than the small void index I of Example 5 k =14.7×10 -15 The relative CO2 permeation rates in Examples 1-4 were 0.7-1.0, which is higher than the relative CO2 permeation rate of 0.6 in Example 5. That is, in Examples 1-4, the separation membrane composite 1 further achieved a high separation capacity.

[0113] On the other hand, in Comparative Example 1, steps S22 to S23 were omitted; therefore, the large porosity index I... p Up to 404×10 -22 (i.e., 200×10) -22 (Above). As a result, the CH4 permeation rate ratio is as high as 2.6 (i.e., above 1.9), and under high differential pressure conditions, CH4 leakage increases. That is, the separation ratio of the separation membrane complex decreases.

[0114] In addition, in Comparative Example 2, steps S22 to S23 were omitted, and the large void index I was increased. p The same extent as Example 1 (6.73 × 10) -22 Therefore, the zeolite film 12 thickens, and the small porosity index I... k As low as 3.60×10 -15 (i.e., less than 10×10) -15 As a result, the relative CO2 permeation rate was as low as 0.3. That is, the separation capacity of the membrane complex was reduced.

[0115] As explained above, the separation membrane composite 1 comprises: a porous support 11, and a separation membrane (a zeolite membrane 12 in the above example) formed on the support 11. This separation membrane contains small pores 121. The surface area of ​​the separation membrane is denoted as S. mLet S represent the area of ​​each small gap 121. k Let S represent the area of ​​each large gap 122. p When, the small void index I represents the existence rate of the small void 121. k =(Σ(S) k 1.5 )) / (S m 1.5 ) is 10×10 -15 The above represents the large void index I, indicating the presence rate of the large void 121. p =(Σ(S) p 2 )) / (S m 2 Less than 200×10 -22 .

[0116] By reducing the total area of ​​the large voids 122 in the separation membrane in this way, a high separation ratio can be achieved in the separation membrane composite 1. In particular, as can be seen from the CH4 permeation rate ratios of Examples 1-5, a high separation ratio can be achieved in the separation membrane composite 1 even under high differential pressure conditions. Furthermore, by maintaining the total area of ​​the small voids 121 in the separation membrane to a certain extent, as can be seen from the CO2 relative permeation rates of Examples 1-5, a high separation processing capacity can be achieved in the separation membrane composite 1.

[0117] As mentioned above, the large porosity index I p Preferred size is less than 100×10 -22 Therefore, based on the CH4 permeation rate ratios of Examples 1-3 and 5, it can be seen that a higher separation ratio can be further achieved under high differential pressure conditions.

[0118] As mentioned above, the small porosity index I k Preferably 20×10 -15 Therefore, based on the relative CO2 permeation rates of Examples 1-4, it can be seen that the separation membrane composite 1 can further achieve a high separation processing capacity.

[0119] As described above, regarding the CH4 permeation rate when a mixed gas containing 50 vol% CO2 and 50 vol% CH4 at 25°C is supplied, the permeation rate at a supply-side pressure of 8.0 MPaG and a permeation-side pressure of 0.0 MPaG is preferably less than 1.9 times the permeation rate at a supply-side pressure of 0.3 MPaG and a permeation-side pressure of 0.0 MPaG. In other words, the above-mentioned CH4 permeation rate ratio is preferably less than 1.9. Accordingly, a separation membrane composite 1 is provided that can suppress the leakage of CH4 (i.e., low-permeability substances) under high differential pressure conditions.

[0120] As described above, the thickness of the separation membrane is preferably 2.5 times or more and 7.5 times or less the average pore size of the surface portion (surface layer 33 in the above example) of the support 11. Accordingly, it is possible to suppress the separation membrane from being too thick or too thin, maintain the total area of ​​the small pores 121 at a certain size, and reduce the total area of ​​the large pores 122. As a result, a separation ratio and a permeability rate of highly permeable substances within a preferred range can be achieved.

[0121] It should be noted that the surface layer 33 and the intermediate layer 32 can be omitted in the support 11.

[0122] The separation membrane described above is preferably a zeolite membrane 12. By using zeolite crystals with small pore sizes to form the separation membrane, selective permeation of substances with small molecular sizes can be effectively achieved, thereby enabling efficient separation of the permeable substance from the mixture.

[0123] More preferably, the zeolite rings constituting the zeolite membrane 12 have a maximum number of elements of 8 or less. Accordingly, selective permeation of permeable substances such as H2 and CO2 with small molecular diameters can be well achieved, thereby enabling efficient separation of the permeable substances from the mixture.

[0124] The manufacturing method of the above-mentioned separation membrane composite 1 includes the following steps: preparing a porous support 11 formed by sintering (step S21); heating the support 11 at a pretreatment temperature (step S22); after step S22, cleaning the support 11 with a fluid (step S23); after step S23, attaching seed crystals to the support 11 (step S25); immersing the support 11 with the attached seed crystals in a raw material solution, using hydrothermal synthesis to grow zeolite from the seed crystals, and forming a separation membrane (i.e., zeolite membrane 12) on the support 11 (step S26). Furthermore, the pretreatment temperature is 400°C or higher and less than 80% of the sintering temperature of the support 11 in step S21. Accordingly, a separation membrane composite 1 with a reduced total area of ​​large voids 122 in the zeolite membrane 12 can be provided. In this separation membrane composite 1, a high separation ratio can be achieved as described above.

[0125] The separation method described above includes the following steps: preparing a separation membrane composite 1 (step S11); supplying a mixture containing multiple gases or liquids to the separation membrane composite 1, causing highly permeable substances (i.e., highly permeable substances) in the mixture to permeate through the separation membrane composite 1, thereby separating them from other substances (step S12). Accordingly, as described above, a high separation ratio can be achieved in the separation of mixed substances.

[0126] This separation method is particularly suitable for mixtures containing one or more of the following substances: hydrogen, helium, nitrogen, oxygen, water, water vapor, carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, sulfur oxides, hydrogen sulfide, sulfur fluoride, mercury, arsine, hydrogen cyanide, carbonyl sulfide, C1-C8 hydrocarbons, organic acids, alcohols, thiols, esters, ethers, ketones, and aldehydes.

[0127] Various modifications can be made to the above-mentioned separation membrane composite 1, the manufacturing method of separation membrane composite 1, and the separation method.

[0128] For example, the small pores 121 of the zeolite membrane 12 are not limited to pores that are naturally generated during the formation of the zeolite membrane 12, but can also be intentionally formed during the manufacture of the separation membrane composite 1.

[0129] In zeolite membrane 12, large porosity 122 is not necessarily required, and the porosity index I p It can be 0. Additionally, the small porosity index I of zeolite film 12... k It can be less than 10×10 -15 .

[0130] The thickness of the zeolite membrane 12 can be less than 2.5 times or more than 7.5 times the average pore size of the surface layer of the support 11.

[0131] The materials, average pore size, and average particle size of the substrate 31, intermediate layer 32, and surface layer 33 of the support 11 are not limited to those described above and can be modified in various ways. In the support 11, multiple intermediate layers 32 with different average pore sizes can be stacked between the substrate 31 and the surface layer 33. Alternatively, the surface layer 33 or intermediate layer 32 can be omitted from the support 11. Or, as described above, the surface layer 33 and intermediate layer 32 can be omitted.

[0132] The maximum number of rings in the zeolite forming the zeolite membrane 12 can be greater than 8. In the separation membrane complex 1, as described above, various types of zeolite can be used to form the zeolite membrane 12.

[0133] The CH4 permeation rate ratio in the separation membrane composite 1 can be above 1.9.

[0134] The manufacturing method of the separation membrane composite 1 is not limited to the above example and various modifications can be made.

[0135] In addition to the support 11 and the zeolite membrane 12, the separation membrane composite 1 may further include a functional membrane or a protective membrane stacked on the zeolite membrane 12. Such functional membranes or protective membranes may be inorganic membranes such as zeolite membranes, silica membranes, or carbon membranes, or organic membranes such as polyimide membranes or organosilicon membranes.

[0136] In the separation membrane composite 1, a separation membrane other than the zeolite membrane 12 (e.g., the inorganic or organic membrane described above) can be formed on the support 11 to replace the zeolite membrane 12.

[0137] The separation apparatus 2 and separation method described above can separate substances other than those exemplified in the above description from the mixture.

[0138] The above-described embodiments and their variations can be appropriately combined as long as they do not contradict each other.

[0139] Although the invention has been described and illustrated in detail, the above description is illustrative and not limiting. Therefore, it can be said that numerous modifications and solutions can be adopted without departing from the scope of the invention.

[0140] Industrial availability

[0141] The separation membrane composite of the present invention can be used as a gas separation membrane, for example, and can also be used in various fields as a separation membrane for substances other than gases, an adsorption membrane for various substances, etc.

[0142] Symbol Explanation

[0143] 1 Separation Membrane Complex

[0144] 11 Support

[0145] 12 Zeolite membrane

[0146] 33 Surface layer

[0147] 121 Small gap

[0148] 122 large gaps

[0149] Steps S11~S12, S21~S27

Claims

1. A separation membrane composite, wherein, It comprises: a porous support and a separation membrane formed on the support. The separation membrane contains small pores. When the surface area of ​​the separation membrane is expressed as S m The area of ​​each small gap is expressed as S. k The area of ​​each large gap is represented by S. p hour, The small void index I represents the presence rate of the small voids. k =(Σ(S) k 1.5 )) / (S m 1.5 ) is 10×10 -15 above, The large void index I represents the presence rate of the large voids. p =(Σ(S) p 2 )) / (S m 2 Less than 200×10 -22 , Among them, S k =π·r k 2 r k Yes: the radius of the small gap when it is approximated as a circle when the surface is viewed from a direction perpendicular to the surface of the separation membrane; S p =π·r p 2 r p Yes: the radius of the large void when the surface is viewed from a direction perpendicular to the surface of the separation membrane, approximating it as a circle.

2. The separation membrane composite according to claim 1, wherein, The large void index I p Less than 100×10 -22 .

3. The separation membrane composite according to claim 1 or 2, wherein, The small void index I k 20×10 -15 above.

4. The separation membrane composite according to claim 1 or 2, wherein, Regarding the permeation rate of CH4 when a mixed gas containing 50% by volume of CO2 and 50% by volume of CH4 at 25°C is supplied, the permeation rate at a supply-side pressure of 8.0 MPaG and a permeation-side pressure of 0.0 MPaG is less than 1.9 times the permeation rate at a supply-side pressure of 0.3 MPaG and a permeation-side pressure of 0.0 MPaG.

5. The separation membrane composite according to claim 1 or 2, wherein, The separation membrane is a zeolite membrane.

6. The separation membrane composite according to claim 5, wherein, The maximum number of rings in the zeolite constituting the zeolite membrane is 8 or less.

7. A method for manufacturing the separation membrane composite according to claim 1 or 2, wherein, The process includes the following steps: a) Prepare a porous support to be formed by firing; b) Heating the support body at the pretreatment temperature; c) After step b), the support is cleaned with a fluid; d) After step c), the seed crystal is attached to the support; e) The support with the attached seed crystals is immersed in a raw material solution, and hydrothermal synthesis is used to allow zeolite to grow from the seed crystals, forming a separation membrane on the support. The pretreatment temperature is above 400°C and less than 80% of the firing temperature of the support in step a).

8. A separation method, wherein, The process includes the following steps: a) Prepare the separation membrane composite according to any one of claims 1 to 6; b) A mixture containing multiple gases or liquids is supplied to the separation membrane complex, allowing highly permeable substances in the mixture to pass through the separation membrane complex and thus be separated from other substances.

9. The separation method according to claim 8, wherein, The mixture contains one or more of the following substances: hydrogen, helium, nitrogen, oxygen, water, carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, sulfur oxides, hydrogen sulfide, sulfur fluoride, mercury, arsine, hydrogen cyanide, carbonyl sulfide, C1-C8 hydrocarbons, organic acids, alcohols, thiols, esters, ethers, ketones, and aldehydes.

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