Separation membrane composite, separation device, separation method, and method for producing separation membrane composite

Abstract

This separation membrane composite (1) comprises a support (11), a separation membrane (12), and a covering membrane (13). The support (11) has a porous section (41) and a compact section (42) that are disposed continuously. The separation membrane (12) is provided on the porous section (41) of the support (11). An end section of the separation membrane (12) is in contact with the compact section (42). The covering membrane (13) is formed from a layered inorganic compound. The covering membrane (13) covers a boundary section (45) between the compact section (42) and the separation membrane (12). This makes it possible to improve the separation performance of the separation membrane composite (1). Additionally, the covering membrane (13) can easily be formed.

Description

[Technical field]

[0001] The present invention relates to separation Membrane complexes, and separation This relates to a technique for separating mixed substances using a membrane complex. [Background technology]

[0002] Currently, various research and development efforts are being conducted on the separation and adsorption of specific molecules using separation membranes such as zeolite membranes.

[0003] For example, WO 2016 / 093192 (Reference 1) discloses a separation membrane composite suitable for separating liquids and gases, which comprises a porous support, a pair of dense glass seals covering both end faces of the porous support, and a zeolite membrane formed on the porous support.

[0004] In such a separation membrane composite, a glass seal covering the end surface of the porous support covers the end surface of the porous support, and the zeolite membrane is formed in contact with the glass seal. When a dense portion such as a glass seal comes into contact with a separation membrane such as a zeolite membrane in this manner, defects such as cracks may occur in the separation membrane near the boundary between the separation membrane and the dense portion during the manufacturing process of the separation membrane composite.

[0005] WO 2014 / 050702 (Document 2) proposes a method of blocking both ends of defective cells with a polymer compound such as synthetic resin, or a method of pouring the polymer compound into defective cells and hardening the polymer compound, as a method of repairing defective cells in a monolithic separation membrane composite in which a zeolite membrane is formed on the inner surface of the through holes (i.e., cells) of a columnar porous support (i.e., a monolithic porous support) having a plurality of through holes extending in the longitudinal direction. In this way, the time required to repair defects in a separation membrane composite is reduced by filling the defective cells themselves without directly repairing the defects.

[0006] Furthermore, JP 2009-214075 A (Reference 3) discloses a technology for suppressing defects at the boundary between a separation membrane formed on a porous support and a dense portion in a separation membrane composite by providing a membrane-shaped coating zeolite that covers both the separation membrane and the dense portion.

[0007] However, when the defective cells themselves are filled as in Reference 2, the number of cells available for separation is reduced, which may decrease the separation speed using the separation membrane composite. Even if the defects are suppressed by providing a membrane-like polymer compound at the boundary between the dense portion and the separation membrane without filling the defective cells themselves, the polymer compound does not have very high heat resistance or organic solvent resistance, so that the use of the separation membrane composite may cause the polymer compound to deteriorate early, resulting in a decrease in separation performance.

[0008] Furthermore, when forming a membrane-like coating zeolite at the boundary between the dense portion and the separation membrane as in Document 3, it is necessary to form the coating zeolite by hydrothermal synthesis or the like after forming the dense portion and the separation membrane, which may complicate the manufacturing process of the separation membrane composite and increase the manufacturing cost of the separation membrane composite. Summary of the Invention

[0009] The present invention is directed to a separation membrane composite, and has an object to improve the separation performance of the separation membrane composite and to easily produce the separation membrane composite.

[0010] A separation membrane composite according to a preferred embodiment of the present invention includes a support having a porous portion and a dense portion arranged in succession, a separation membrane provided on the porous portion of the support and having an end portion in contact with the dense portion, and a membrane covering the boundary between the dense portion and the separation membrane. Subject to and a covering film. The coating film is made of smectite or bentonite, and has an average thickness of 0.002 μm or more and 2.0 μm or less.

[0011] According to the present invention, the separation performance of a separation membrane composite can be improved, and the separation membrane composite can be easily produced.

[0016] Preferably, the separation membrane is a zeolite membrane.

[0017] The present invention is also directed to a separation device. A separation device according to a preferred embodiment of the present invention includes the above-mentioned separation membrane composite and a supply unit that supplies a mixed substance containing multiple types of gases or liquids to the separation membrane composite. The separation membrane composite separates a highly permeable substance in the mixed substance from the mixed substance by permeating the highly permeable substance in the mixed substance.

[0018] The present invention is also directed to a separation method. A separation method according to a preferred embodiment of the present invention includes the steps of: a) preparing the above-mentioned separation membrane composite; and b) supplying a mixed substance containing a plurality of types of gases or liquids to the separation membrane composite, and separating a highly permeable substance in the mixed substance from the mixed substance by permeating the separation membrane composite.

[0019] Preferably, the mixture contains one or more of 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, mercaptans, esters, ethers, ketones, and aldehydes.

[0020] The present invention is directed to a method for producing a separation membrane composite. A method for producing a separation membrane composite according to a preferred embodiment of the present invention includes the steps of: a) arranging a dense portion of a support so as to be continuous with a porous portion; b) forming a separation membrane on the porous portion of the support; and c) forming a separation membrane on a boundary portion between the separation membrane and the dense portion, the boundary portion having an end in contact with the dense portion. to and covering the boundary portion by forming a covering film. The coating film is made of smectite or bentonite, and has an average thickness of 0.002 μm or more and 2.0 μm or less.

[0025] Preferably, the separation membrane is a zeolite membrane.

[0026] Preferably, the method for producing the separation membrane composite further comprises, after step c), a step of heat treating the support, the separation membrane and the covering membrane at a temperature of 200° C. or higher.

[0027] The above and other objects, features, aspects and advantages will become apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief description of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view of a separation membrane composite according to one embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing an end portion of the separation membrane composite. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing a central portion of the separation membrane composite. [Figure 4A] 1 is an SEM image showing a cross section near the coating film. [Figure 4B] 1 is an enlarged SEM image showing a cross section near the coating film. [Diagram 5] FIG. [Figure 6] FIG. 1 is a diagram showing the flow of separation of a mixed material. [Figure 7] FIG. 2 is a diagram showing a flow of manufacturing a separation membrane composite. [Figure 8] FIG. 11 is an enlarged cross-sectional view showing an end portion of another separation membrane composite. [Figure 9] FIG. 11 is an enlarged cross-sectional view showing an end portion of another separation membrane composite. [Figure 10] FIG. 11 is an enlarged cross-sectional view showing an end portion of another separation membrane composite. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Fig. 1 is a cross-sectional view of a separation membrane composite 1 according to one embodiment of the present invention. Fig. 2 is a cross-sectional view showing an enlarged view of a portion of an end portion in the longitudinal direction (i.e., the left-right direction in Fig. 1) of the separation membrane composite 1. Fig. 3 is a cross-sectional view showing an enlarged view of a portion of the central portion in the longitudinal direction of the separation membrane composite 1.

[0030] The separation membrane composite 1 includes a support 11, a separation membrane 12, and a coating membrane 13. The support 11 includes a porous portion 41, which is a columnar main body portion, and a dense portion 42 that covers both end surfaces in the longitudinal direction (i.e., the left-right direction in FIG. 1) of the porous portion 41. In FIG. 1, the separation membrane 12 is depicted by a thick line. Also, in FIG. 1, the coating membrane 13 shown in FIG. 2 is omitted. In FIG. 2, the porous portion 41, the dense portion 42, and the separation membrane 12 are marked with parallel diagonal lines, and the coating membrane 13 is depicted by a thick line. Also, in FIG. 2, the dense portion 42, the separation membrane 12, and the coating membrane 13 are depicted thicker than they actually are. Similarly, in FIG. 3, the separation membrane 12 is depicted thicker than they actually are.

[0031] In the example shown in FIG. 1, the porous portion 41 of the support 11 is an integrally molded, continuous, substantially columnar member. The porous portion 41 is provided with a plurality of through holes 111 each extending in the longitudinal direction. That is, the porous portion 41 is a so-called monolithic member. The outer shape of the porous portion 41 is, for example, substantially cylindrical. The porous portion 41 is a porous member having pores through which gas and liquid can pass. The cross section perpendicular to the longitudinal direction of each through hole 111 (i.e., cell) is, for example, substantially circular. In FIG. 1, the diameter of the through holes 111 is drawn larger than the actual diameter, and the number of the through holes 111 is drawn smaller than the actual number.

[0032] The length of the porous portion 41 (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 porous portion 41 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 porous portion 41 is, for example, 0.1 μm to 5.0 μm, and preferably 0.2 μm to 2.0 μm. The shape of the porous portion 41 may be, for example, a honeycomb shape, a flat plate shape, a tubular shape, a cylindrical shape, a columnar shape, or a polygonal column shape. When the shape of the porous portion 41 is a tubular or cylindrical shape, the thickness of the porous portion 41 is, for example, 0.1 mm to 10 mm.

[0033] The material of the porous portion 41 can be various substances (for example, ceramics or metals) as long as they are chemically stable in the process of forming the separation membrane 12 on the surface. In this embodiment, the porous portion 41 is formed of a ceramic sintered body. Examples of ceramic sintered bodies selected as the material of the porous portion 41 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, the porous portion 41 contains at least one of alumina, silica, and mullite.

[0034] The porous portion 41 may contain an inorganic binder. As the inorganic binder, at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite can be used.

[0035] The average pore diameter of the porous portion 41 is, for example, 0.01 μm to 70 μm, and preferably 0.05 μm to 25 μm. The average pore diameter of the porous portion 41 in the vicinity of the surface on which the separation membrane 12 is formed is 0.01 μm to 1 μm, and preferably 0.05 μm to 0.5 μm. The average pore diameter can be measured, for example, by a mercury porosimeter, a perm-po Lome Data or Nano Perm Po Lome The pore size distribution throughout the porous portion 41, including the surface and the interior, is D5, for example, 0.01 μm to 50 μm, D50, for example, 0.05 μm to 70 μm, and D95, for example, 0.1 μm to 2000 μm. The porosity of the porous portion 41 in the vicinity of the surface where the separation membrane 12 is formed is, for example, 20% to 60%.

[0036] The porous portion 41 has a multilayer structure in which, for example, a plurality of layers having different average pore diameters are laminated in the thickness direction. The average pore diameter and sintered grain size in the surface layer including the surface on which the separation membrane 12 is formed are smaller than the average pore diameter and sintered grain size in the layers other than the surface layer. The average pore diameter of the surface layer of the porous portion 41 is, for example, 0.01 μm to 1 μm, and preferably 0.05 μm to 0.5 μm. When the porous portion 41 has a multilayer structure, the materials for each layer can be those described above. The materials for the layers forming the multilayer structure may be the same or different.

[0037] The dense portion 42 is a film-like or thin plate-like member fixed to both longitudinal ends of the porous portion 41. At each longitudinal end of the porous portion 41, the dense portion 42 covers and seals the longitudinal end faces of the porous portion 41, the outer side faces near the end faces, and the inner side faces near the end faces of each through hole 111. The dense portion 42 is, for example, a non-porous member that does not substantially have pores. The dense portion 42 preferably has high strength, as well as high heat resistance and chemical resistance.

[0038] The dense portion 42 is formed of, for example, glass, ceramic, metal, resin, or the like. In the present embodiment, the dense portion 42 is made of glass. The dense portion 42 is, for example, a glass film formed on the surface of the porous portion 41 by firing. The average thickness of the dense portion 42 is, for example, 1 μm to 1000 μm. The dense portion 42 is formed, for example, by attaching glass frit to the surface of the porous portion 41 and firing it together with the porous portion 41. The dense portion 42 may be formed in parallel with the formation of the separation membrane 12, or may be formed before or after the formation of the separation membrane 12. The material and shape of the dense portion 42 may be appropriately changed. For example, the dense portion 42 may be a porous member having pores with an average pore diameter smaller than that of the surface layer of the porous portion 41.

[0039] In the portion where the dense portion 42 is disposed, the inflow and outflow of gas and liquid does not substantially occur, and even if it does occur, it is slight. That is, the dense portion 42 is disposed continuously with the porous portion 41, and is a sealing portion that substantially prevents the inflow and outflow of gas and liquid into the porous portion 41. Note that, in the portion of the dense portion 42 that covers the longitudinal end face of the porous portion 41, a plurality of openings that overlap with the plurality of through holes 111 of the porous portion 41 are provided. Therefore, both longitudinal ends of each through hole 111 are not covered by the dense portion 42, and the inflow and outflow of gas and liquid from the both ends into the through hole 111 is possible.

[0040] The separation membrane 12 is a substantially cylindrical thin film provided on the inner surface of the through hole 111 of the porous portion 41, over substantially the entire surface of the inner surface. The longitudinal end of the separation membrane 12 contacts the dense portion 42 covering the longitudinal end of the inner surface on the inner surface of the through hole 111. That is, the separation membrane 12 covers substantially the entire region of the inner surface of the through hole 111 that is not covered by the dense portion 42. In the example shown in FIG. 2, the longitudinal edge of the separation membrane 12 and the longitudinal edge of the dense portion 42 are in contact with each other, and the longitudinal end of the separation membrane 12 and the longitudinal end of the dense portion 42 hardly overlap each other in the radial direction of the through hole 111 (i.e., the vertical direction in FIG. 2).

[0041] The separation membrane 12 is a dense porous membrane having micropores. The separation membrane 12 can separate a specific substance from a mixed substance in which a plurality of types of substances are mixed. When the dense portion 42 is a porous material, the average pore diameter of the separation membrane 12 is larger than the average pore diameter of the dense portion 42. In other words, the dense portion 42 is denser than the separation membrane 12. When the dense portion 42 is a porous material, if the specific substance is to be separated from the mixed substance by the dense portion 42, the permeation rate of the specific substance is 1 / 10 or less (preferably 1 / 100 or less) of the case where separation is performed by the separation membrane 12. Preferably, the dense portion 42 is a non-porous material that is sufficiently denser than the separation membrane 12 and does not substantially allow the specific substance to permeate.

[0042] In this embodiment, the separation membrane 12 is a zeolite membrane. The zeolite membrane is at least a membrane of zeolite formed on the surface of the porous portion 41 of the support 11, and does not include a membrane in which zeolite particles are simply dispersed in an organic membrane. As described above, the zeolite membrane can be used as a separation membrane for separating a specific substance from a mixed substance. In the zeolite membrane, other substances are less likely to permeate than the specific substance. In other words, the amount of the other substance that permeates the zeolite membrane is smaller than the amount of the specific substance that permeates the zeolite membrane. The zeolite membrane may contain two or more types of zeolites with different structures and compositions.

[0043] The thickness of the separation 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 separation membrane 12 improves the separation performance. Increasing the thickness of the separation membrane 12 increases the permeation rate. The surface roughness (Ra) of the separation membrane 12 is, for example, 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and more preferably 0.5 μm or less.

[0044] The pore diameter of the zeolite crystals contained in the separation membrane 12 (hereinafter, simply referred to as the "pore diameter of the separation 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 0.5 nm or less. If the pore diameter of the separation membrane 12 is less than 0.2 nm, the amount of substances that permeate the separation membrane 12 may be small, and if the pore diameter of the separation membrane 12 is greater than 0.8 nm, the selectivity of the substances by the separation membrane 12 may be insufficient. The pore diameter of the separation membrane 12 is the diameter of the pore in a direction approximately perpendicular to the maximum diameter of the pores of the zeolite crystals that constitute the separation membrane 12 (i.e., the major axis, which is the maximum distance between oxygen atoms). The pore diameter of the separation membrane 12 is smaller than the average pore diameter on the surface of the porous portion 41 of the support 11 on which the separation membrane 12 is disposed.

[0045] When the maximum number of rings in the zeolite constituting the separation membrane 12 is n, the short diameter of the n-ring pore is defined as the pore diameter of the separation membrane 12. When the zeolite has a plurality of types of n-ring pores with the same n, the short diameter of the n-ring pore with the largest short diameter is defined as the pore diameter of the separation membrane 12. The n-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 later to form a ring structure. The n-ring refers to a ring that forms a through hole (channel), and does not include a ring that does not form a through hole. The n-ring pore is a pore formed by an n-ring. From the viewpoint of improving selectivity, the maximum number of rings in the zeolite contained in the above-mentioned separation membrane 12 is preferably 8 or less (for example, 6 or 8).

[0046] The pore size of the separation membrane 12, which is a zeolite membrane, is uniquely determined by the framework structure of the zeolite.<URL:http: / / www.iza-structure.org / databases / > The values ​​can be obtained from the values ​​disclosed in the

[0047] The type of zeolite constituting the separation membrane 12 is not particularly limited, and examples thereof include zeolites of 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, examples thereof include zeolites of 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.

[0048] The zeolite constituting the separation membrane 12 contains at least one of silicon (Si), aluminum (Al) and phosphorus (P) as a T atom (i.e., an atom located at the center of an oxygen tetrahedron (TO4) constituting the zeolite). As the zeolite constituting the separation membrane 12, a zeolite in which the T atom is only Si or consists of Si and Al, an AlPO type zeolite in which the T atom is Al and P, a SAPO type zeolite in which the T atom is Si, Al and P, a MAPSO type zeolite in which the T atom is magnesium (Mg), Si, Al and P, a ZnAPSO type zeolite in which the T atom is zinc (Zn), Si, Al and P, or the like can be used. Some of the T atoms may be substituted with other elements.

[0049] The separation membrane 12 contains, for example, Si. The separation membrane 12 may contain, for example, any two or more of Si, Al, and P. The separation membrane 12 may contain an alkali metal. The alkali metal is, for example, sodium (Na) or potassium (K). When the separation membrane 12 contains Si atoms and Al atoms, the Si / Al ratio in the separation membrane 12 is, for example, 1 or more and 100,000 or less. The Si / Al ratio is the molar ratio of Si elements to Al elements contained in the separation 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 ratio, the more preferable it is. The Si / Al ratio in the separation membrane 12 can be adjusted by adjusting the mixing ratio of the Si source and the Al source in the raw material solution described later.

[0050] In the separation membrane composite 1, the separation membrane 12 may include a membrane other than a zeolite membrane in addition to the zeolite membrane, or the separation membrane 12 may be a membrane other than a zeolite membrane.

[0051] The coating film 13 is a thin-film member that covers the boundary 45 between the dense portion 42 and the separation membrane 12 over substantially the entirety in each through-hole 111. In the example shown in FIG. 2, the boundary 45 between the dense portion 42 and the separation membrane 12 is a substantially circumferential region where the longitudinal edge of the dense portion 42 and the separation membrane 12 are in contact. As shown in FIG. 2, when the substantially circumferential region (i.e., the contact portion) where the longitudinal edge of the dense portion 42 and the separation membrane 12 are in contact is directly covered by the separation membrane 12, the substantially circumferential region where the surface extending from the contact portion in a direction perpendicular to the surface of the porous portion 41 (i.e., the normal direction of the surface of the porous portion 41) intersects with the surface of the separation membrane 12 is defined as the boundary 45. The coating film 13 is a member that includes a substantially cylindrical portion provided over the entire circumference of the inner surface of the through-hole 111 on the boundary 45 between the dense portion 42 and the separation membrane 12. The coating membrane 13 may extend on both sides in the longitudinal direction from the boundary portion 45. Furthermore, the coating membrane 13 may extend continuously in the longitudinal direction from the longitudinal end of the separation membrane 12 to the dense portion 42, and cover the longitudinal end of the dense portion 42.

[0052] 2, the coating film 13 extends from the boundary portion 45 toward the separation membrane 12 in the longitudinal direction by 1 mm to 50 mm. The coating film 13 covers substantially the entire surface of the dense portion 42 on the inner side surface of the through hole 111. In the example shown in FIG. 2, the coating film 13 extends from the boundary portion 45 to the longitudinal end face of the support 11 (i.e., the longitudinal end face of the dense portion 42), but it does not have to extend to the end face. Alternatively, the edge of the coating film 13 on the dense portion 42 side may be located between the longitudinal end face of the support 11 and the boundary portion 45.

[0053] FIG. 4A is a scanning electron microscope (SEM) image showing a cross section of the separation membrane composite 1 near the coating membrane 13. FIG. 4B is an enlarged SEM image of the coating membrane 13 of FIG. 4A. As shown in FIG. 4A and FIG. 4B, the coating membrane 13 is a thin film member having a layered microstructure formed by a layered inorganic compound. A layered inorganic compound is an inorganic compound having a layered structure. In other words, when a cross section of the coating membrane 13 is observed by an SEM or a transmission electron microscope (TEM), it is possible to confirm that the coating membrane 13 is formed by a layered inorganic compound by observing a layered microstructure. The layered structure is a structure in which a sheet structure in which atoms are strongly bonded and densely arranged by covalent bonds or ionic bonds, etc., is stacked approximately parallel in the thickness direction by weak bonding forces such as van der Waals forces, or a highly flat structure in which the sheet structures are stacked in the thickness direction and bonded via ions or molecules. 4A and 4B, a large number of sheet structures are laminated in layers in the vertical direction in the drawing. The thickness of each sheet structure is, for example, 0.3 nm to 10 nm.

[0054] As the layered inorganic compound forming the coating film 13, for example, clay minerals, layered metal oxides, layered double hydroxides, layered phosphates, layered carbon, etc. can be used. As the clay minerals, for example, pyrophyllite, mica, smectite, vermiculite, chlorite, kaolinite, halloysite, talc, other layered silicates, etc. can be used. As the layered metal oxides, for example, layered titanates, layered niobates, layered manganese oxides, layered perovskites, etc. can be used. As the layered phosphates, for example, α-type zirconium phosphate, γ-type zirconium phosphate, α-type titanium phosphate, γ-type titanium phosphate, aluminum triphosphate, etc. can be used. As the layered carbons, for example, graphite, graphene, graphene oxide, etc. can be used.

[0055] The layered inorganic compound forming the coating film 13 is preferably a clay mineral or a layered metal oxide, more preferably a clay mineral. More preferably, the layered inorganic compound forming the coating film 13 is smectite. As the smectite, montmorillonite, beidellite, nontronite, saponite, hectorite, stevensite, sauconite, etc. can be used.

[0056] It is preferable that the coating membrane 13 does not substantially allow gas and liquid to permeate, and even if it does, the amount of permeation is small. If the coating membrane 13 is a porous member, if the specific substance is to be separated from the mixed substance by the coating membrane 13, the permeation rate of the specific substance is equal to or lower than that when separation is performed by the separation membrane 12 (preferably 1 / 10 or less, more preferably 1 / 100 or less). It is preferable that the coating membrane 13 is sufficiently denser than the separation membrane 12 and is a non-porous member that does not substantially allow the specific substance to permeate. It is preferable that the coating membrane 13 has high strength, as well as high heat resistance and chemical resistance. It is acceptable for either the coating membrane 13 or the dense portion 42 to be denser than the other, and they may have the same degree of denseness.

[0057] The average thickness of the coating film 13 is, for example, 0.002 μm or more, preferably 0.01 μm or more. By setting the average thickness to 0.002 μm, the denseness of the coating film 13 is improved, and the permeation of gas, liquid, etc. through the coating film 13 is suitably suppressed. Furthermore, by setting the average thickness to 0.01 μm or more, the denseness of the coating film 13 is further improved. The upper limit of the average thickness of the coating film 13 is not particularly limited, but is, for example, 10 μm or less, preferably 5 μm or less. By setting the average thickness to 10 μm or less, the occurrence of defects such as cracks in the coating film 13 is suppressed. Furthermore, by setting the average thickness to 5 μm or less, the occurrence of defects is further suppressed. The average thickness of the coating film 13 can be obtained by observing the cross section with a SEM or TEM.

[0058] Next, separation of a mixed substance using the separation membrane complex 1 will be described with reference to Figures 5 and 6. Figure 5 is a diagram showing a separation device 2. Figure 6 is a diagram showing a flow of separation of a mixed substance by the separation device 2.

[0059] In the separation device 2, a mixed substance containing multiple types of fluids (i.e., gas or liquid) is supplied to the separation membrane composite 1, and highly permeable substances in the mixed substance are separated from the mixed substance by permeating through the separation 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 low permeable substances (hereinafter also referred to as "lowly permeable substances").

[0060] 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.

[0061] The mixture includes, for example, one or more of 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), arsine (AsH3), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1-C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. The highly permeable substance is, for example, one or more of H2, He, N2, O2, H2O, CO2, NH3, and H2S.

[0062] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the above-mentioned nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5), etc. X The gas is called NOX.

[0063] Sulfur oxides are compounds of sulfur and oxygen. The above-mentioned sulfur oxides include, for example, sulfur dioxide (SO2), sulfur trioxide (SO3), and other SO X The gas is called SOXX.

[0064] Sulfur fluoride is a compound of fluorine and sulfur. The above-mentioned sulfur fluoride is, for example, disulfur difluoride (FSSF, S = SF2), sulfur difluoride (SF2), sulfur tetrafluoride (SF4), sulfur hexafluoride (SF6) or disulfur decafluoride (S2F 10 ) etc.

[0065] C1-C8 hydrocarbons are those with 1 to 8 carbon atoms. C3-C8 hydrocarbons may be straight-chain compounds, side-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be saturated hydrocarbons (i.e., those with no double or triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double or triple bonds in the molecule). C1-C4 hydrocarbons are, for example, methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), normal butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), or isobutene (CH2=C(CH3)2).

[0066] The organic acid may be a carboxylic acid or a sulfonic acid. The carboxylic acid may be, for example, formic acid (CH2O2), acetic acid (C2H4O2), oxalic acid (C2H2O4), acrylic acid (C3H4O2), or benzoic acid (C6H5COOH). The sulfonic acid may be, for example, ethanesulfonic acid (C2H6O3S). The organic acid may be a chain compound or a cyclic compound.

[0067] The above-mentioned alcohols are, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)) or butanol (C4H9OH).

[0068] Mercaptans are organic compounds that have hydrogenated sulfur (SH) at the end, and are also called thiols or thioalcohols. Examples of the mercaptans mentioned above include methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), and 1-propanethiol (C3H7SH).

[0069] The esters mentioned above are, for example, formates or acetates.

[0070] The above-mentioned ethers are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3) or diethyl ether ((C2H5)2O).

[0071] The above-mentioned ketones are, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3) or diethyl ketone ((C2H5)2CO).

[0072] The above-mentioned aldehydes are, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO) or butanal (butyraldehyde) (C3H7CHO).

[0073] 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.

[0074] The separation device 2 includes a separation membrane composite 1, an outer cylinder 22, two sealing members 23, a supply section 26, a first recovery section 27, and a second recovery section 28. The separation membrane composite 1 and the sealing members 23 are housed in the outer cylinder 22. The supply section 26, the first recovery section 27, and the second recovery section 28 are disposed outside the outer cylinder 22 and connected to the outer cylinder 22.

[0075] The shape of the outer cylinder 22 is not particularly limited, and is, for example, a substantially cylindrical tubular member. The outer cylinder 22 is formed of, for example, stainless steel or carbon steel. The longitudinal direction of the outer cylinder 22 is substantially parallel to the longitudinal direction of the separation membrane composite 1. A supply port 221 is provided at one end of the outer cylinder 22 in the longitudinal direction (i.e., the end on the left side in FIG. 5), 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 unit 26 is connected to the supply port 221. A first collection unit 27 is connected to the first discharge port 222. A second collection unit 28 is connected to the second discharge port 223. The internal space of the outer cylinder 22 is a sealed space isolated from the space around the outer cylinder 22.

[0076] The two seal members 23 are disposed around the entire circumference between the outer surface of the separation membrane composite 1 and the inner surface of the outer tube 22 near both ends of the separation membrane composite 1 in the longitudinal direction. Each seal member 23 is a substantially annular member formed of a material impermeable to gas and liquid. The seal member 23 is, for example, an O-ring formed of a flexible resin. The seal member 23 is in close contact with the outer surface of the separation membrane composite 1 and the inner surface of the outer tube 22 around the entire circumference. In the example shown in FIG. 5, the seal member 23 is in close contact with a portion of the outer surface of the support 11 of the separation membrane composite 1 where the porous portion 41 is covered by the dense portion 42. Note that a coating film 13 may be formed on the portion of the dense portion 42 where the seal member 23 is disposed. In other words, the seal member 23 and the dense portion 42 may be in close contact with each other via the coating film 13. The gap between the sealing member 23 and the outer surface of the separation membrane composite 1, and the gap between the sealing member 23 and the inner surface of the outer cylinder 22 are sealed, so that gas and liquid can hardly or completely pass through them.

[0077] The supply unit 26 supplies the mixed gas to the internal space of the outer cylinder 22 via the supply port 221. The supply unit 26 includes a pressure-feeding mechanism such as a blower or a pump that pressure-feeds the mixed gas toward the outer cylinder 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 the outer cylinder 22. The first recovery unit 27 and the second recovery unit 28 include, for example, a storage container that stores the gas derived from the outer cylinder 22, or a blower or a pump that transfers the gas.

[0078] When separating a mixed gas, first, a separation membrane composite 1 is prepared (FIG. 6: step S11). Specifically, the separation membrane composite 1 is prepared by being attached inside the outer casing 22. Then, a mixed gas containing a plurality of types of gases having different permeabilities to the separation membrane 12 is supplied to the inside of the outer casing 22 by the supply unit 26 as shown by the 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 of the mixed gas supplied from the supply unit 26 to the inside of the outer casing 22 (i.e., the supply side pressure) 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.

[0079] The mixed gas supplied from the supply unit 26 to the outer cylinder 22 is introduced into each through-hole 111 of the support 11 from the left end of the separation membrane composite 1 in the figure. In other words, the mixed gas from the supply unit 26 is supplied to the separation membrane composite 1 in the outer cylinder 22. A highly permeable substance (e.g., CO2) that is a gas with high permeability in the mixed gas permeates the separation membrane 12 provided on the inner surface of each through-hole 111 and the porous portion 41 of the support 11, and is discharged from the outer surface of the support 11. As a result, the highly permeable substance is separated from the mixed gas (step S12).

[0080] The gas (hereinafter referred to as "permeate") discharged from the outer surface of the support 11 is led to the second recovery section 28 via the second discharge port 223 as shown by the 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) is, for example, 0.0 MPaG. In addition to the above-mentioned high permeability substances, the permeate substances may also include low permeability substances (e.g., CH4), which are gases with low permeability in the mixed gas.

[0081] Furthermore, gases other than the substances that have permeated the separation membrane 12 and the support 11 (hereinafter referred to as "non-permeating substances") in the mixed gas pass through each through-hole 111 of the support 11 from the left side to the right side in the figure, and are recovered by the first recovery section 27 via the first discharge port 222, as shown by the arrow 252. The pressure of the gas recovered by the first recovery section 27 is, for example, approximately the same as the introduction pressure. The non-permeating substances may include, in addition to the above-mentioned low-permeability substances, highly permeable substances that have not permeated the separation membrane 12. The non-permeating substances recovered by the first recovery section 27 may be circulated to the supply section 26, for example, and supplied again into the outer cylinder 22.

[0082] Next, an example of a manufacturing flow of the separation membrane composite 1 will be described with reference to FIG. 7. In the following, a manufacturing method of the separation membrane composite 1 including the separation membrane 12, which is a DDR type zeolite membrane, will be described. When the separation membrane composite 1 is manufactured, first, the support 11 is formed and prepared (step S21). In step S21, for example, raw materials including the aggregate material of the porous portion 41, a pore-forming agent, a binder, and the like are prepared and mixed. Next, water is added to the raw materials, and the materials are kneaded by a kneader to prepare a puddle. Next, the puddle is molded by an extrusion molding machine or the like, and a molded body having a plurality of through holes 111 (see FIG. 1) is obtained. Note that the molded body may be molded by a molding method other than extrusion molding.

[0083] The molded body is dried and degreased. Then, a material for the dense portion 42, such as glass frit, is attached to the area of ​​the molded body where the dense portion 42 is to be provided. Thereafter, the molded body to which the glass frit or the like is attached is fired to form the support 11. As described above, the support 11 includes the porous portion 41 and the dense portion 42 continuous with the porous portion 41. That is, step S21 is a process of forming and arranging the dense portion 42 of the support 11 so as to be continuous with the porous portion 41. The temperature during firing treatment of the outermost layer of the molded body (i.e., firing temperature) is, for example, 1000°C to 1500°C, and is 1250°C in this embodiment. The firing time is, for example, 1 hour to 100 hours. The firing treatment conditions of the molded body may be appropriately changed. In step S21, the molded body may be fired without adhering glass frit or the like to form a porous portion 41, and then glass frit or the like may be attached to the porous portion 41 and fired again to form a dense portion 42 continuous with the porous portion 41.

[0084] In the production of the separation membrane composite 1, in parallel with step S21, or before or after step S21, zeolite seed crystals to be used in the formation of the separation membrane 12 are generated and prepared (step S22). In the generation of the seed crystals, a raw material solution of the seed crystals 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. Subsequently, hydrothermal synthesis of the raw material solution is performed, and the obtained crystals are washed and dried to obtain a powder of zeolite (e.g., DDR type zeolite). The zeolite powder may be used as the seed crystals as it is, or the seed crystals may be obtained by processing the powder by pulverization or the like.

[0085] Next, the seed crystals are attached onto the inner side surfaces of the through holes 111 of the support 11 (step S23). Specifically, the seed crystals are attached to the inner side surfaces of the through holes 111 at locations where the porous portions 41 are exposed. The attachment of the seed crystals to the support 11 is performed, for example, by immersing the porous support 11 in a dispersion liquid in which the seed crystals are dispersed in a solvent (for example, water or an alcohol such as ethanol). The immersion of the support 11 in the dispersion liquid may be repeated multiple times. The seed crystals may also be attached to the support 11 by a method other than the above.

[0086] The support 11 to which the seed crystal is attached is immersed in the raw material solution. The raw material solution is prepared, for example, by dissolving a Si source, SDA, and the like in a solvent. The composition of the raw material solution is, for example, 1.0SiO2:0.015SDA:0.12(CH2)2(NH2)2. Water or alcohol such as ethanol may be used as the solvent of the raw material solution. When water is used as the solvent of the raw material solution, the molar ratio of SDA to water contained in the raw material solution is preferably 0.01 or less. In addition, the molar ratio of SDA to water contained in the raw material solution is preferably 0.00001 or more. The SDA contained in the raw material solution is, for example, an organic substance. For example, 1-adamantanamine can be used as the SDA.

[0087] Then, the DDR-type zeolite is grown by hydrothermal synthesis using the above-mentioned seed crystals as nuclei, thereby forming the DDR-type separation membrane 12 on the porous portion 41 of the support 11 (step S24). The longitudinal end of the separation membrane 12 is in contact with the longitudinal end of the dense portion 42, as described above. The temperature during the hydrothermal synthesis is preferably 120 to 200°C, for example 130°C. The hydrothermal synthesis time is preferably 5 to 100 hours, for example 15 hours.

[0088] When the hydrothermal synthesis is completed, the support 11 and the separation membrane 12 are washed with pure water. The washed support 11 and separation membrane 12 are dried, for example, at 80° C. After the support 11 and the separation membrane 12 are dried, the separation membrane 12 is heat-treated to burn off the SDA in the separation membrane 12 almost completely, thereby perforating the micropores in the separation membrane 12 (step S25).

[0089] In the method for producing the separation membrane composite 1, the formation of the dense portion 42 in step S21 may be performed after steps S22 to S25 (i.e., the formation of the separation membrane 12 on the porous portion 41). Depending on the use mode of the SDA, step S25 may be omitted.

[0090] When steps S21 to S25 are completed, coating film 13 made of a layered inorganic compound is formed on boundary portion 45 between separation membrane 12 and dense portion 42. As a result, boundary portion 45 is coated with coating film 13 (step S26).

[0091] In forming the coating film 13, first, a material for the coating film 13 (hereinafter also referred to as "coating film material") is dispersed in a solvent to prepare a dispersion liquid. The coating film material is a powder of a layered inorganic compound (for example, a clay mineral such as smectite). In the dispersion liquid, solvent molecules enter between the layers of the layered inorganic compound, and the layered inorganic compound is separated into flakes. The size of each flake in the planar direction (i.e., the direction perpendicular to the thickness direction) is, for example, several tens of nm to several tens of μm. The type of solvent is appropriately determined according to the type of material for the coating film 13. When smectite is used as the material for the coating film 13, pure water or the like can be used as the solvent. The content of the coating film material in the dispersion liquid is appropriately determined depending on the type of coating film material, the thickness of the coating film 13 to be formed, and the like. The content is, for example, 0.1% by mass to 10% by mass.

[0092] When the dispersion liquid is prepared, the dispersion liquid is applied to the support 11 having the separation membrane 12 formed on the inner surface of the through hole 111. The dispersion liquid is applied to the entire region (i.e., the region including the boundary portion 45) on the inner surface of the through hole 111 where the coating film 13 is to be formed, and is not applied to other regions. The dispersion liquid is applied, for example, by inserting the longitudinal end of the support 11 into the dispersion liquid stored in a container and immersing it (so-called dip coating). The dispersion liquid may be applied by various methods other than dip coating. For example, the dispersion liquid may be sprayed onto the support 11 and the separation membrane 12, or the dispersion liquid may be applied by a coater such as a brush.

[0093] Thereafter, the support 11 and separation membrane 12 coated with the dispersion are dried. The drying is, for example, natural drying or ventilation drying in a temperature environment of 20° C. to 100° C. As the dispersion dries, a coating membrane 13 is formed that covers the boundary portion 45 between the separation membrane 12 and the dense portion 42, and the above-mentioned separation membrane composite 1 is obtained.

[0094] In the production of the separation membrane composite 1, after step S26, the separation membrane composite 1 (i.e., the support 11, the separation membrane 12, and the coating membrane 13) may be heat-treated at a temperature of 200° C. or higher (step S27). This improves the adhesion of the coating membrane 13 to the separation membrane 12 and the dense portion 42. The denseness of the coating membrane 13 is also improved. The heating temperature during the heat treatment is, for example, 200° C. or higher and 1000° C. or lower, preferably 250° C. or higher and 800° C. or lower, and more preferably 300° C. or higher and 600° C. or lower. The heating time during the heat treatment is, for example, 1 hour to 100 hours. The heat treatment is performed, for example, by placing the separation membrane composite 1 in a dryer, an electric furnace, or the like and heating it. The heat treatment may be performed by various other methods. In addition, the atmosphere during the heat treatment may be, for example, air, oxygen, an inert gas, or the like.

[0095] Next, with reference to Table 1, the relationship between the presence or absence of the coating membrane 13 and the separation performance of the separation membrane composite 1 will be described. The separation membrane composites 1 of Examples 1 to 3 in Table 1 are separation membrane composites equipped with the above-mentioned coating membrane 13. The separation membrane composite of Comparative Example 1 is a separation membrane composite not equipped with the coating membrane 13 (i.e., the boundary portion 45 between the separation membrane 12 and the dense portion 42 is exposed).

[0096] The permeation rates (i.e., permeance) of CO2 and CH4 through the separation membrane composite 1 were determined by supplying a mixed gas of CO2 and CH4 from the supply unit 26 to the separation membrane composite 1 in the outer cylinder 22 in the above-mentioned separation device 2. The unit of the permeation rate is [nmol / (m 2 The pressure of the mixed gas supplied from the supply unit 26 to the separation membrane composite 1 (i.e., the supply side pressure) is 0.3 MPaG. The pressure of the permeable gas that has permeated the separation membrane composite 1 (i.e., the permeation side pressure) is 0 MPaG. The permeation rates of CO2 and CH4 were determined by measuring the permeable gas with a mass flow meter (MFM) and a gas chromatograph. The CO2 permeation rate was then divided by the CH4 permeation rate to determine the ratio of the CO2 permeation rate to the CH4 permeation rate (i.e., the permeation rate ratio CO2 / CH4).

[0097] [Table 1]

[0098] The permeation rate ratio coefficient in Table 1 indicates the ratio of the permeation rate ratio CO2 / CH4 of Examples 1 to 3, with the permeation rate ratio CO2 / CH4 of Comparative Example 1 taken as the standard (i.e., 1.0). In other words, the permeation rate ratio coefficient is a value obtained by dividing the permeation rate ratio CO2 / CH4 of Examples 1 to 3 by the permeation rate ratio CO2 / CH4 of Comparative Example 1.

[0099] The separation membrane composite of Comparative Example 1 was produced by the production method shown in steps S21 to S25 described above. The porous portion 41 of the support 11 is a monolithic porous alumina substrate. The dense portion 42 is a thin glass film. The separation membrane 12 is a DDR type zeolite membrane. The hydrothermal synthesis temperature and hydrothermal synthesis time in step S24 are 130°C and 15 hours, respectively. In step S25, SDA was removed by heating at 450°C for 50 hours.

[0100] The separation membrane composite 1 of Example 1 was produced by carrying out the above-mentioned steps S26 to S27 for the separation membrane composite of Comparative Example 1. The dispersion in step S26 was prepared by dispersing the coating membrane material in pure water using clay mineral "Sumecton-SA" (manufactured by Kunimine Kogyo Co., Ltd.) as the coating membrane material. Sumecton-SA is a synthetic smectite mainly composed of saponite. The content of the coating membrane material in the dispersion was 1 mass %. The heating temperature and heating time in the heat treatment in step S27 were 200°C and 20 hours, respectively. The permeation rate ratio coefficient was 1.6, and the separation performance of the separation membrane composite 1 was improved compared to Comparative Example 1 not having the coating membrane 13. The improvement in separation performance was due to the fact that defects such as cracks at the boundary portion 45 between the separation membrane 12 and the dense portion 42 were covered (i.e., repaired) by the coating membrane 13, and leakage of CH4 from the defects was suppressed. The thickness of the coating membrane 13 was 0.8 μm.

[0101] Example 2 is similar to Example 1, except that the coating membrane material was changed to a clay mineral, "Sumecton-SWN" (manufactured by Kunimine Kogyo Co., Ltd.). Sumecton-SWN is a synthetic smectite whose main component is hectorite. The permeation rate specific coefficient was 1.6, and the separation performance of the separation membrane composite 1 was improved compared to Comparative Example 1 which did not have the coating membrane 13. The thickness of the coating membrane 13 was 2.0 μm.

[0102] Example 3 is similar to Example 1, except that the coating membrane material was changed to "Kunipia-F" (manufactured by Kunimine Industries Co., Ltd.), which is a clay mineral. Kunipia-F is a refined bentonite whose main component is montmorillonite. The permeation rate specific coefficient was 1.3, and the separation performance of the separation membrane complex 1 was improved compared to Comparative Example 1, which did not have the coating membrane 13. The thickness of the coating membrane 13 was 0.5 μm.

[0103] The separation membrane composites 1 of Examples 1 to 3 were heated at 400° C. for 1 hour, and then the permeation rate specific coefficients were measured in the same manner as above. As a result, the permeation rate specific coefficients did not change. This shows that the coating membranes 13 in the separation membrane composites 1 of Examples 1 to 3 have high heat resistance.

[0104] As described above, the separation membrane composite 1 includes the support 11, the separation membrane 12, and the coating membrane 13. The support 11 has the porous portion 41 and the dense portion 42 that are continuously arranged. The separation membrane 12 is provided on the porous portion 41 of the support 11. An end of the separation membrane 12 contacts the dense portion 42. The coating membrane 13 is formed of a layered inorganic compound. The coating membrane 13 covers the boundary portion 45 between the dense portion 42 and the separation membrane 12. In the separation membrane composite 1, defects such as cracks at the boundary portion 45 between the separation membrane 12 and the dense portion 42 are covered (i.e., repaired) by the coating membrane 13, so that the above-mentioned low-permeability substance can be prevented from leaking from the defect and being included in the permeable substance. As a result, as shown in Examples 1 to 3, the separation performance of the separation membrane composite 1 can be improved. In addition, by using a layered inorganic compound as the coating membrane material, a dense coating membrane 13 can be easily formed compared to the case where the coating membrane is formed from zeolite. As a result, the separation membrane composite 1 can be produced easily.

[0105] As described above, the layered inorganic compound is preferably a clay mineral or a layered metal oxide, which can increase the heat resistance of the coating film 13.

[0106] As described above, it is more preferable that the layered inorganic compound is a clay mineral, which can further facilitate the formation of the coating film 13. In addition, clay minerals are easily available and relatively inexpensive, so that the production cost of the separation membrane composite 1 can be reduced.

[0107] As described above, it is more preferable that the layered inorganic compound is smectite (Examples 1 and 2). This can further improve the density of the coating membrane 13 and the separation performance of the separation membrane composite 1, compared to when the layered inorganic compound is bentonite (Example 3).

[0108] As described above, the average thickness of the coating membrane 13 is preferably 0.002 μm or more. This improves the denseness of the coating membrane 13 and effectively inhibits gas, liquid, and the like from permeating the coating membrane 13. As a result, the separation performance of the separation membrane composite 1 can be effectively improved.

[0109] As described above, the separation membrane 12 is preferably a zeolite membrane. By forming the separation membrane 12 from zeolite crystals with uniform pore size, selective permeation of the target substance can be suitably achieved. As a result, the target substance can be efficiently separated from the mixed substance.

[0110] As described above, the separation device 2 includes the separation membrane composite 1 and a supply unit 26 that supplies a mixed substance containing multiple types of gases or liquids to the separation membrane composite 1. The separation membrane composite 1 separates a substance having high permeability (i.e., a highly permeable substance) from the mixed substance by permeating the substance. The separation device 2 can separate the highly permeable substance from the mixed substance at a high permeation rate ratio.

[0111] The above-mentioned separation method includes a step (step S11) of preparing the separation membrane composite 1, and a step (step S12) of supplying a mixed substance containing multiple types of gases or liquids to the separation membrane composite 1 and separating a substance with high permeability in the mixed substance (i.e., a highly permeable substance) from the mixed substance by permeating the separation membrane composite 1. This allows the highly permeable substance to be separated from the mixed substance at a high permeation rate ratio.

[0112] The separation method is particularly suitable when the mixture contains 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, mercaptans, esters, ethers, ketones, and aldehydes.

[0113] The above-mentioned method for producing the separation membrane composite 1 includes a step (step S21) of arranging the dense portion 42 of the support 11 so as to be continuous with the porous portion 41, a step (step S24) of forming a separation membrane 12 on the porous portion 41 of the support 11, and a step (step S26) of forming a coating film 13 made of a layered inorganic compound on a boundary portion 45 between the separation membrane 12 and the dense portion 42, where the end portion contacts the dense portion 42, to cover the boundary portion 45. This makes it possible to easily form a dense coating film 13, and as a result, a separation membrane composite 1 with high separation performance can be easily produced.

[0114] As described above, the method for producing the separation membrane composite 1 preferably further includes, after step S26, a step of heat treating the support 11, separation membrane 12, and coating membrane 13 at a temperature of 200° C. or higher (step S27). This can improve the adhesion between the separation membrane 12 and the dense portion 42 and the coating membrane 13. It can also improve the density of the coating membrane 13.

[0115] The above-described separation membrane composite 1, the method for producing the separation membrane composite 1, the separation device 2, and the separation method can be modified in various ways.

[0116] In the technology related to the present invention, The average thickness of the coating film 13 does not necessarily have to be 0.002 μm or more, nor does it necessarily have to be 10 μm or less, that is, the average thickness of the coating film 13 may be less than 0.002 μm, or may be greater than 10 μm.

[0117] As described above, in the separation membrane composite 1 illustrated in Figure 2, the longitudinal ends of the separation membrane 12 and the longitudinal ends of the dense portion 42 barely overlap in the radial direction of the through hole 111 (i.e., the vertical direction in Figure 2), but these ends may overlap.

[0118] For example, as shown in FIG. 8, the end of the dense portion 42 in the longitudinal direction may be in direct contact with the inner side of the through hole 111 of the porous portion 41, and the end of the separation membrane 12 in the longitudinal direction may be provided on the dense portion 42. In other words, the end of the separation membrane 12 in the longitudinal direction is indirectly in contact with the inner side of the through hole 111 of the porous portion 41, sandwiching the dense portion 42. In this case, the boundary portion 45 between the separation membrane 12 and the dense portion 42 refers to a substantially circumferential portion where a surface extending in a direction perpendicular to the surface of the porous portion 41 of a substantially circumferential region where the edge of the dense portion 42 and the separation membrane 12 are in contact intersects with the surface of the separation membrane 12. The coating membrane 13 covers the boundary portion 45 over substantially the entirety, and extends from the boundary portion 45 to both sides in the longitudinal direction. This can improve the separation performance of the separation membrane composite 1 in the same manner as described above. In addition, the dense coating membrane 13 can be easily formed.

[0119] Alternatively, as shown in FIG. 9, the longitudinal end of the separation membrane 12 may be in direct contact with the inner side of the through hole 111 of the porous portion 41, and the longitudinal end of the dense portion 42 may be provided on the separation membrane 12. In other words, the longitudinal end of the dense portion 42 is indirectly in contact with the inner side of the through hole 111 of the porous portion 41, sandwiching the separation membrane 12. In this case, the boundary portion 45 between the separation membrane 12 and the dense portion 42 refers to a substantially circumferential portion where the edge of the dense portion 42 and the separation membrane 12 are in contact with each other in the radial direction of the through hole 111. The coating membrane 13 covers the boundary portion 45 over substantially the entirety, and extends from the boundary portion 45 to both sides in the longitudinal direction. This can improve the separation performance of the separation membrane composite 1, as described above. In addition, the dense coating membrane 13 can be easily formed.

[0120] Also, as shown in FIG. 10, the dense portion 42 may be fixed to the end surface in the longitudinal direction of the porous portion 41. The cross-sectional shape of the porous portion 41 and the cross-sectional shape of the dense portion 42 may be substantially the same or different. The separation membrane 12 is provided on the porous portion 41 and extends on the dense portion 42. That is, the separation membrane 12 covers the boundary portion between the porous portion 41 and the dense portion 42. In this case, the boundary portion 45 between the separation membrane 12 and the dense portion 42 refers to a substantially circumferential portion where the edge of the dense portion 42 and the separation membrane 12 are in contact with each other in the radial direction of the through hole 111. The coating membrane 13 covers substantially the entire boundary portion 45 and extends from the boundary portion 45 to both sides in the longitudinal direction. This can improve the separation performance of the separation membrane composite 1 in the same manner as described above. In addition, the dense coating membrane 13 can be easily formed. In the example shown in FIG. 10, the coating film 13 covers the inner surface of the through hole 421 of the dense portion 42 over substantially the entire surface.

[0121] The method for producing the separation membrane composite 1 is not limited to the above example and may be modified in various ways. For example, the step of heat-treating the separation membrane 12 and the covering membrane 13 at a temperature of 200° C. or higher (step S27) may be omitted.

[0122] In addition to the support 11, the separation membrane 12, and the covering membrane 13, the separation membrane composite 1 may further include a functional membrane or a protective membrane laminated on the separation membrane 12. Such a functional membrane or protective membrane may be an inorganic membrane such as a zeolite membrane, a silica membrane, or a carbon membrane, or an organic membrane such as a polyimide membrane or a silicone membrane.

[0123] As mentioned above, the separation membrane 12 may be a membrane other than a zeolite membrane (for example, the inorganic or organic membranes mentioned above).

[0124] In the above-described separation device 2 and separation method, substances other than those exemplified in the above description may be separated from the mixed substance. The structure of the separation device 2 is not limited to the above example, and may be modified in various ways.

[0125] The configurations in the above-described embodiment and each of the modified examples may be combined as appropriate as long as they are not mutually inconsistent.

[0126] Although the invention has been particularly illustrated and described, it is to be understood that the above description is illustrative and not restrictive, and therefore numerous modifications and variations are possible without departing from the scope of the invention. [Industrial Applicability]

[0127] The separation membrane composite of the present invention can be used, for example, as a gas separation membrane, and further, can be used in various fields as a separation membrane or adsorption membrane for various substances other than gas. [Explanation of symbols]

[0128] 1 Separation membrane complex 2 Separation device 11 Support 12 Separation membrane 13 Coating film 26 Supply section 41 Porous part 42 Dense part 45 Border S11~S12, S21~S27 steps

Claims

1. A separation membrane composite, A support having a porous portion and a dense portion arranged in succession; a separation membrane provided on the porous portion of the support and having an end portion in contact with the dense portion; A coating membrane that covers a boundary portion between the dense portion and the separation membrane; Equipped with The coating film is formed of smectite or bentonite, The average thickness of the coating film is 0.002 μm or more and 2.0 μm or less.

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

3. A separation device comprising: The separation membrane composite according to claim 1 or 2, A supply unit that supplies a mixed substance containing multiple types of gases or liquids to the separation membrane composite; Equipped with The separation membrane composite separates a highly permeable substance in the mixture from the mixture by allowing the substance to permeate therethrough.

4. A method of separation comprising the steps of: a) preparing a separation membrane composite according to claim 1 or 2; b) supplying a mixture containing a plurality of types of gases or liquids to the separation membrane composite, and separating a highly permeable substance in the mixture from the mixture by permeating the separation membrane composite; Equipped with.

5. The method of claim 4, further comprising the steps of: The mixture of substances includes one or more of 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, mercaptans, esters, ethers, ketones, and aldehydes.

6. A method for producing a separation membrane composite, comprising the steps of: a) disposing a dense portion of a support so as to be continuous with a porous portion; b) forming a separation membrane on the porous portion of the support; c) forming a coating film on the boundary between the separation membrane and the dense portion where the end portion contacts the dense portion, thereby coating the boundary portion; Equipped with The coating film is formed of smectite or bentonite, The average thickness of the coating film is 0.002 μm or more and 2.0 μm or less.

7. A method for producing the separation membrane composite according to claim 6, comprising the steps of: The separation membrane is a zeolite membrane.

8. A method for producing the separation membrane composite according to claim 6 or 7, The method further comprises, after step c), a step of heat treating the support, the separation membrane and the coating membrane at a temperature of 200° C. or higher.

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