Separation membrane composite and mixed gas separation device

Abstract

The separation membrane composite (1) comprises a porous support (11) and a separation membrane (12) that is disposed on the support (11). In the separation membrane composite (1), the membrane end region (122) refers to each region in the range that is one-tenth the length of a longitudinal direction of a separation membrane (12) from each edge in the longitudinal direction of the separation membrane (12), and the membrane central region (123) refers to the part of the separation membrane (12) other than the membrane end regions (122) at the two sides in the longitudinal direction. The average permeation velocity of CF4 gas at one membrane end region (122) is at least 5-times, but not more than 100-times, the average permeation velocity of CF4 gas at the membrane central region (123). The separation performance of the separation membrane composite (1) can be improved by these features.

Description

[Technical Field]

[0001] The present invention relates to a separation membrane composite, a mixed gas separation device, and a method for producing a separation membrane composite. [Reference to Related Application] This application claims the benefit of priority from Japanese Patent Application JP2022-017638, filed February 8, 2022, the entire disclosure of which is incorporated herein by reference. [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 / 104048 (Reference 1) and WO 2016 / 104049 (Reference 2) disclose gas separation modules that separate specific gases from a mixed gas using a gas separation membrane structure in which a gas separation membrane is formed on a porous support. In these gas separation modules, the internal space of the housing is divided into two spaces by a plate-like gas separation membrane structure, and a mixed gas is supplied to one space (i.e., the supply side space). A specific gas in the mixed gas (hereinafter referred to as the "target gas to permeate") permeates through the gas separation membrane structure and moves to the other space (i.e., the permeate side space) where it is separated from the mixed gas. In these gas separation modules, when the concentration of the target gas to permeate in the mixed gas is low, a sweep gas is passed through the permeate side space to reduce the partial pressure of the target gas to permeate in the permeate side space, thereby promoting permeation of the target gas.

[0004] Furthermore, International Publication No. 2016 / 093192 (Reference 3) and Japanese Patent Application Laid-Open No. 2009-214075 (Reference 4) disclose a monolithic separation membrane composite comprising a cylindrical porous support having a plurality of longitudinally extending through-holes (i.e., cells) and a separation membrane provided on the inner surface of the cells. In this separation membrane composite, a seal portion is provided at the longitudinal end of the porous support so as to contact the separation membrane, and cracks are likely to occur in the separation membrane at the portion adjacent to the seal portion (i.e., the longitudinal end of the separation membrane). Therefore, Reference 4 proposes a technology for preventing leakage of gases other than the target gas through cracks by providing a membrane-shaped coating zeolite at the boundary between the separation membrane and the seal portion so as to cover both the separation membrane and the seal portion.

[0005] Incidentally, when separating a mixed gas containing a low concentration of the target gas using a monolithic separation membrane composite such as those described in References 3 and 4, it is possible to flow a sweep gas into the space outside the columnar porous support. However, in cells that are far from the space through which the sweep gas flows (for example, cells located near the center of the cross section perpendicular to the longitudinal direction of the porous support), the permeation-promoting effect of the sweep gas is not very pronounced, limiting the improvement in the separation performance of the mixed gas. Furthermore, with regard to defects such as cracks at the longitudinal ends of the separation membrane, attention has been focused only on reducing the defects, and there has been no idea of ​​actively utilizing the defects to improve separation performance. Summary of the Invention

[0006] The present invention is directed to a separation membrane composite, and has as its main object to improve the separation performance of the separation membrane composite.

[0007] Book A separation membrane composite according to a preferred embodiment of the present invention comprises: A cylindrical or columnar structure extending in the longitudinal direction A porous support and a and a cylindrical member extending in the longitudinal direction. and a separation membrane. The aforementioned From both longitudinal ends of the separation membrane The aforementionedThe portions within the range of 1 / 10 of the longitudinal length are defined as membrane ends, and the separation membrane The aforementioned The portion excluding the membrane ends on both sides in the longitudinal direction is defined as the membrane center, and the average permeation flow rate of CF4 gas at one membrane end is 5 to 100 times the average permeation flow rate of CF4 gas at the membrane center.

[0008] The separation membrane composite according to the present invention can improve separation performance.

[0009] Preferably, the average permeation flow rate of CF4 gas at the one membrane end is 5 to 50 times the average permeation flow rate of CF4 gas at the membrane center.

[0010] Preferably, the average permeation flow rate of CF4 gas at the other membrane end is 5 times or more and 100 times or less than the average permeation flow rate of CF4 gas at the membrane center.

[0011] Preferably, a sealing portion is provided at a portion of the support where the one membrane end is located, covering and sealing the surface opposite to the surface in contact with the one membrane end, and the sealing portion extends from a position facing the one membrane end across the support to a position facing the membrane center across the support.

[0012] Preferably, the separation membrane is a zeolite membrane.

[0013] Preferably, the maximum number of rings in the zeolite constituting the zeolite membrane is 8 or less.

[0014] Preferably, the support is The aforementioned The separation membrane has a columnar shape extending in the longitudinal direction. The aforementioned It is placed on the inner surface of the film-forming cell that penetrates in the longitudinal direction.

[0015] The present invention is also directed to a mixed gas separation apparatus. A preferred embodiment of the mixed gas separation apparatus of the present invention comprises the above-described separation membrane composite and a housing that accommodates the separation membrane composite. The housing is connected to a supply section that supplies a mixed gas containing multiple gases to the separation membrane composite, a permeate gas recovery section that recovers a permeate gas from the mixed gas that has permeated through the separation membrane composite, and a non-permeate gas recovery section that recovers a non-permeate gas from the mixed gas that has not permeated through the separation membrane composite.

[0016] Preferably, the mixed gas contains one or more substances selected from the group consisting of 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 to C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes.

[0018] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view of a separation membrane composite according to one embodiment. [Figure 2] FIG. 2 is a view showing an end face of a separation membrane composite. [Figure 3] FIG. 2 is a cross-sectional view of a separation membrane composite. [Figure 4] FIG. 10 is a diagram showing another example of an end face of a separation membrane composite. [Figure 5] FIG. 3 is an enlarged cross-sectional view showing the vicinity of an end of a first cell. [Figure 6] FIG. 3 is an enlarged cross-sectional view showing the vicinity of an end of a first cell. [Figure 7] FIG. 1 is a diagram showing a flow of manufacturing a separation membrane composite. [Figure 8A] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8B] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8C] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8D] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8E] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8F] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8G] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 8H] FIG. 1 is a diagram showing the state of a separation membrane composite in the process of being manufactured. [Figure 9] FIG. [Figure 10] FIG. 1 is a diagram showing the flow of separation of a mixed gas. [Figure 11] FIG. 3 is an enlarged cross-sectional view showing the vicinity of an end of a first cell. DETAILED DESCRIPTION OF THE INVENTION

[0020] FIG. 1 is a perspective view of a separation membrane composite 1 according to one embodiment of the present invention. FIG. 1 also shows a portion of the internal structure of the separation membrane composite 1. FIG. 2 is a view showing one end surface 114 in the longitudinal direction (i.e., approximately the left-right direction in FIG. 1) of the separation membrane composite 1. FIG. 3 is an enlarged view of a portion of the longitudinal cross section of the separation membrane composite 1, showing the vicinity of a cell 111, which will be described later. The separation membrane composite 1 is used, for example, in a mixed gas separation device 2, which will be described later, to separate a specific gas from a mixed gas.

[0021] The separation membrane composite 1 includes a porous support 11 and a separation membrane 12 (see FIG. 3) formed on the support 11. In FIG. 3, the separation membrane 12 is indicated by diagonal lines. The support 11 is a porous member that is permeable to gas and liquid. In the example shown in FIG. 1, the support 11 is a monolithic support having an integrally molded, continuous columnar body with a plurality of through-holes 111 (hereinafter also referred to as "cells 111") extending in the longitudinal direction of the body. In the support 11, a plurality of cells 111 are formed (i.e., partitioned) by porous partition walls. In the example shown in FIG. 1, the outer shape of the support 11 is approximately cylindrical. The cross-sectional shape of each cell 111 perpendicular to the longitudinal direction is, for example, approximately circular. Note that the term "approximately circular" is a concept that includes not only a perfect circle but also an ellipse or a distorted circle. The cross-sectional shape of each cell 111 is preferably, but not necessarily, a perfect circle. 1, the diameter of the cells 111 is drawn larger than the actual diameter, and the number of the cells 111 is drawn smaller than the actual number (the same applies to FIG. 2). Also, in FIG. 3, the thickness of the separation membrane 12 is drawn thicker than the actual thickness.

[0022] The multiple cells 111 include first cells 111a and second cells 111b. In the example shown in FIGS. 1 and 2, the first cells 111a and the second cells 111b have substantially the same shape. At both longitudinal end faces 114 of the support body 11, the openings of the second cells 111b are plugged with plugging members 115. In other words, the second cells 111b are closed at both longitudinal ends. In FIGS. 1 and 2, the plugging members 115 are indicated by diagonal lines. On the other hand, at both longitudinal end faces 114 of the support body 11, the openings of the first cells 111a are not plugged and are open.

[0023] The separation membrane 12 (see FIG. 3) described above is disposed on the inner surface of each first cell 111a, which is open at both longitudinal ends. The separation membrane 12 is preferably provided so as to cover the entire inner surface of each first cell 111a. That is, the first cell 111a is a membrane cell having the separation membrane 12 provided on the inside. In the separation membrane composite 1, the second cell 111b does not have the separation membrane 12 provided on the inside. As will be described later, the second cell 111b is an exhaust cell used to exhaust the permeation gas that has permeated the separation membrane 12.

[0024] In the example shown in Figures 1 and 2, the multiple cells 111 are arranged in a matrix on the end surface 114 of the support 11 in the vertical direction (i.e., the up-and-down direction in Figure 2) and the horizontal direction. In the following description, a group of cells 111 arranged in a row in the horizontal direction (i.e., the left-right direction in Figure 2) will also be referred to as a "cell row." The multiple cells 111 include multiple rows of cell rows arranged in the vertical direction. In the example shown in Figure 2, each row of cell rows is composed of multiple first cells 111a or multiple second cells 111b.

[0025] In the example shown in Fig. 2, in the multiple cell rows, a cell row of second cells 111b in one row (hereinafter also referred to as "second cell row 116b") and a cell row of first cells 111a in two rows (hereinafter also referred to as "first cell row 116a") are arranged adjacent to each other in the vertical direction and alternately. In Fig. 2, each first cell row 116a and each second cell row 116b are indicated by being surrounded by a two-dot chain line (the same applies to Fig. 4 described later). The second cell row 116b is a plugged cell row in which both ends in the longitudinal direction are plugged.

[0026] The second cells 111b in the second cell row 116b are connected to each other by slits 117 (see FIG. 1) extending in the horizontal direction. The slits 117 extend to the outer surface 112 of the support 11 on both sides of the second cell row 116b in the horizontal direction, and the second cells 111b in the second cell row 116b are connected to the space outside the support 11 through the slits 117. The cross-sectional shape of the slits 117 perpendicular to the horizontal direction is, for example, substantially rectangular. The cross-sectional shape of the slits 117 may be modified in various ways, such as to be substantially circular. The cross-section of the slits 117 is much larger than the cross-section of the pores in the support 11. In the separation membrane composite 1 illustrated in FIG. 1, three slits 117 are provided near each longitudinal end of the support 11. Each slit 117 opens to the outer surface of the support 11 on both sides in the lateral direction, so six openings (hereinafter also referred to as "slit openings") are provided on the outer surface of the support 11 near the ends. The six slit openings have approximately the same shape and are located at approximately the same position in the longitudinal direction. Note that near both ends of the support 11 in the longitudinal direction, the shapes and positions of some or all of the slit openings (the above-mentioned six slit openings) may be different.

[0027] The first cell row 116a is an open cell row with both longitudinal ends open, and is also a deposition cell row with a separation film 12 (see FIG. 3) provided inside. The two rows of first cells 111a adjacent to one side of the second cell row 116b in the vertical direction constitute an open cell row group. In other words, the open cell row group is the two rows of first cells 116a sandwiched between the two second cell rows 116b positioned closest to each other in the vertical direction.

[0028] The number of rows of the first cell rows 116a constituting the open cell row group is not limited to two and may be variously changed. Preferably, the number of rows of the first cell rows 116a constituting the open cell row group is one or more and six or less, and more preferably one or two. Figure 4 shows an example in which the number of rows of the first cell rows 116a constituting the open cell row group sandwiched between two second cell rows 116b is five.

[0029] Furthermore, the number of second cell rows 116b is not limited to three, and may be one, or two or more. Furthermore, in the separation membrane complex 1, the second cells 111b do not necessarily need to be arranged in the horizontal direction, and the second cells 111b may be arranged randomly. Alternatively, the number of second cells 111b provided in the separation membrane complex 1 may be one. Furthermore, in the separation membrane complex 1, the second cells 111b may be omitted, and only the first cells 111a may be provided.

[0030] The length of the support 11 in the longitudinal direction is, for example, 100 mm to 2000 mm. The outer diameter of the support 11 is, for example, 5 mm to 300 mm. The distance between adjacent cells 111 (i.e., the thickness of the support 11 between the closest portions of the adjacent cells 111) is, for example, 0.3 mm to 10 mm. The surface roughness (Ra) of the inner surface of the first cells 111a of the support 11 is, for example, 0.1 μm to 5.0 μm, and preferably 0.2 μm to 2.0 μm. The shape of the support 11 may be, for example, a honeycomb shape, a flat plate shape, a tubular shape, a cylindrical shape, a columnar shape, or a polygonal pillar shape. When the shape of the support 11 is tubular or cylindrical, the thickness of the support 11 is, for example, 0.1 mm to 10 mm.

[0031] The area of ​​the cross section perpendicular to the longitudinal direction of each cell 111 is, for example, 2 mm 2 Over 300mm 2 The following is an example. As described above, when the cross section of each cell 111 is substantially circular, the diameter of the cross section is preferably 1.6 mm to 20 mm. The shape and size of the cells 111 may be changed in various ways. For example, the shape of the cross section perpendicular to the longitudinal direction of the cells 111 may be substantially polygonal. The shapes and sizes of the first cells 111a and the second cells 111b may be different. Furthermore, the shapes and sizes of some or all of the first cells 111a may be different from each other, and the shapes and sizes of some or all of the second cells 111b may be different from each other.

[0032] Various substances (for example, ceramics or metals) can be used as the material of support 11, as long as they are chemically stable in the process of forming separation membrane 12 on the surface. In this embodiment, support 11 is formed of a ceramic sintered body. Examples of ceramic sintered bodies selected as the material of support 11 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, support 11 contains at least one of alumina, silica, and mullite.

[0033] The support 11 may contain an inorganic binder for binding aggregate particles of the ceramic sintered body, which may be at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite.

[0034] The support 11 has a multilayer structure in which multiple layers with different average pore sizes are stacked in the thickness direction near the inner surface of each of the first cells 111a, which are open cells (i.e., near the separation membrane 12). In the example shown in FIG. 3, the support 11 includes a porous substrate 31, a porous intermediate layer 32 formed on the substrate 31, and a porous surface layer 33 formed on the intermediate layer 32. That is, the surface layer 33 is indirectly provided on the substrate 31 via the intermediate layer 32. The intermediate layer 32 is also provided between the substrate 31 and the surface layer 33. The surface layer 33 constitutes the inner surface of each of the first cells 111a of the support 11, and the separation membrane 12 is formed on the surface layer 33. The thickness of the surface layer 33 is, for example, 1 μm to 100 μm. The thickness of the intermediate layer 32 is, for example, 100 μm to 500 μm. The intermediate layer 32 and the surface layer 33 may or may not be provided on the inner surface of each second cell 111b. The intermediate layer 32 and the surface layer 33 may or may not be provided on the outer surface 112 and the end surface 114 of the support 11.

[0035] The average pore diameter of the surface layer 33 is smaller than the average pore diameter of the intermediate layer 32 and the average pore diameter of the substrate 31. The average pore diameter of the intermediate layer 32 is also smaller than the average pore diameter of the substrate 31. The average pore diameter of the substrate 31 is, for example, 1 μm or more and 70 μm or less. The average pore diameter of the intermediate layer 32 is, for example, 0.1 μm or more and 10 μm or less. The average pore diameter of the surface layer 33 is, for example, 0.005 μm or more and 2 μm or less. The average pore diameters of the substrate 31, intermediate layer 32, and surface layer 33 can be measured, for example, by a mercury porosimeter, a perm porometer, or a nanoperm porometer.

[0036] The surface layer 33, the intermediate layer 32, and the substrate 31 have substantially the same porosity. The porosity of the surface layer 33, the intermediate layer 32, and the substrate 31 is, for example, 15% or more and 70% or less. The porosity of the surface layer 33, the intermediate layer 32, and the substrate 31 can be measured by, for example, the Archimedes method, the mercury porosity method, or an image analysis method.

[0037] The substrate 31, intermediate layer 32, and surface layer 33 may be formed of the same material or different materials. For example, the substrate 31 and surface layer 33 contain Al2O3 as a main material. The intermediate layer 32 contains aggregate particles mainly made of Al2O3 and an inorganic binder mainly made of TiO2. In this embodiment, the aggregate particles of the substrate 31, intermediate layer 32, and surface layer 33 are formed substantially only from Al2O3. The substrate 31 may contain an inorganic binder such as glass.

[0038] The average particle size of the aggregate particles in the surface layer 33 is smaller than the average particle size of the aggregate particles in the intermediate layer 32. The average particle size of the aggregate particles in the intermediate layer 32 is also smaller than the average particle size of the aggregate particles in the base material 31. The average particle sizes of the aggregate particles in the base material 31, intermediate layer 32, and surface layer 33 can be measured by, for example, laser diffraction.

[0039] The plugging member 115 can be formed from the same material as the base material 31, the intermediate layer 32, and the surface layer 33. The porosity of the plugging member 115 is, for example, 15% to 70%.

[0040] As described above, the separation membrane 12 is formed on the inner surface of each first cell 111a, which is an open cell (i.e., on the surface layer 33), and covers the inner surface over substantially the entire surface. The separation membrane 12 is a porous membrane having micropores. The separation membrane 12 separates a specific substance from a mixture of multiple types of substances. In this embodiment, the separation membrane 12 is substantially cylindrical.

[0041] The separation membrane 12 is preferably an inorganic membrane formed from an inorganic material, more preferably a zeolite membrane, silica membrane, carbon membrane, or MOF (metal-organic composite) membrane, and particularly preferably a zeolite membrane. That is, the separation membrane composite 1 is preferably an inorganic membrane composite, more preferably a zeolite membrane composite, silica membrane composite, carbon membrane composite, or MOF membrane composite, and particularly preferably a zeolite membrane composite. A zeolite membrane is at least a membrane of zeolite formed on the surface of a support 11, and does not include a membrane of zeolite particles simply dispersed in an organic membrane. The same applies to other inorganic membranes. In this embodiment, the separation membrane 12 is a zeolite membrane. The separation membrane 12 may be a zeolite membrane containing two or more types of zeolites with different structures and compositions.

[0042] The thickness of the separation membrane 12 is, for example, 0.05 μm or more and 50 μm or less, preferably 0.1 μm or more and 20 μm or less, and more preferably 0.5 μm or more and 10 μm or less. Increasing the thickness of the separation membrane 12 improves separation performance. Reducing 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 even more preferably 0.5 μm or less. The pore diameter of the separation membrane 12 is, for example, 0.2 nm to 1 nm. The pore diameter of the separation membrane 12 is smaller than the average pore diameter of the surface layer 33 of the support 11.

[0043] When the maximum number of rings in the zeolite constituting the separation membrane 12 is n, the minor axis of the n-membered ring pore is defined as the pore diameter of the separation membrane 12. When the zeolite has multiple types of n-membered ring pores with the same n, the minor axis of the n-membered ring pore with the largest minor axis is defined as the pore diameter of the separation membrane 12. Note that an n-membered ring refers to a portion in which the number of oxygen atoms constituting the skeleton forming the pore is n, and each oxygen atom is bonded to a T atom (described below) to form a ring structure. Note that an n-membered ring refers to a ring that forms a through-hole (channel), and does not include a ring that does not form a through-hole. An n-membered ring pore is a pore formed by an n-membered ring. From the viewpoint of improving selectivity, the maximum number of rings in the zeolite constituting the separation membrane 12 is preferably 8 or less (for example, 6 or 8).

[0044] The pore size of the separation membrane 12 is primarily 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

[0045] The type of zeolite constituting separation membrane 12 is not particularly limited, and may be, for example, AEI, AEN, AFN, AFV, AFX, BEA, CHA, DDR, ERI, ETL, FAU (X, Y), GIS, IHW, LEV, LTA, LTJ, MEL, MFI, MOR, PAU, RHO, SOD, or SAT zeolite. When the zeolite is an eight-membered ring zeolite, it may be, for example, AEI, AFN, AFV, AFX, CHA, DDR, ERI, ETL, GIS, IHW, LEV, LTA, LTJ, RHO, or SAT zeolite. In this embodiment, the type of zeolite constituting separation membrane 12 is DDR zeolite.

[0046] 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). Zeolites constituting the separation membrane 12 include zeolites in which the T atom is Si only or contains Si and Al, AlPO zeolites in which the T atom is Al and P, SAPO zeolites in which the T atom is Si, Al, and P, MAPSO zeolites in which the T atom is magnesium (Mg), Si, Al, and P, and ZnAPSO zeolites in which the T atom is zinc (Zn), Si, Al, and P. Some of the T atoms may be substituted with other elements. The zeolite constituting the separation membrane 12 may contain an alkali metal. The alkali metal is, for example, sodium (Na) or potassium (K).

[0047] When the zeolite constituting separation membrane 12 contains Si atoms and Al atoms, the Si / Al ratio in the zeolite constituting separation membrane 12 is, for example, 1 or more and 100,000 or less. The Si / Al ratio is the molar ratio of Si element to Al element contained in the zeolite constituting separation membrane 12. The Si / Al ratio is preferably 5 or more, more preferably 20 or more, and even more preferably 100 or more; the higher the Si / Al ratio, the higher the heat resistance and acid resistance of separation membrane 12, which is preferable. The Si / Al ratio can be adjusted by adjusting the compounding ratio of the Si source and Al source in the raw material solution, which will be described later.

[0048] FIG. 5 is an enlarged cross-sectional view showing the vicinity of one longitudinal end of the first cell 111a of the separation membrane composite 1. In FIG. 5, the separation membrane 12 is depicted thicker than it actually is, and the support 11, separation membrane 12, and sealing portion 21 are indicated by hatched lines (the same applies to FIG. 6). The sealing portion 21 is a member that covers and seals the longitudinal end face 114 of the support 11 and a portion of the outer surface 112 near the end face 114 on both longitudinal sides of the separation membrane composite 1. The sealing portion 21 is a sealing layer made of, for example, glass or resin. The sealing portion 21 prevents gas and liquid from flowing into or out of the support 11.

[0049] In the following description, the portions of the separation membrane 12 that extend from the longitudinal edge 121 of the separation membrane 12 to 1 / 10 of the longitudinal length of the separation membrane 12 on both longitudinal sides will be referred to as the "membrane end portion 122." In other words, the membrane end portion 122 is a substantially cylindrical portion that extends from the edge 121 of the separation membrane 12 toward the longitudinal center by 1 / 10 of the longitudinal length of the separation membrane 12. In the example shown in FIG. 5, the edge 121 of the separation membrane 12 is located at substantially the same longitudinal position as the opening of the first cell 111a and the end face 114 of the support 11. Therefore, the longitudinal length of the separation membrane 12 (i.e., the longitudinal distance between the opposite edge 121 of the separation membrane 12) is substantially the same as the longitudinal length of the support 11. In the following description, the portions of the separation membrane 12 excluding the membrane end portions 122 on both longitudinal sides will be referred to as the "membrane center portion 123." In FIG. 5, a boundary 124 between the membrane edge 122 and the membrane center 123 of the separation membrane 12 is indicated by a two-dot chain line.

[0050] 5, the sealing portion 21 covers a portion of the end face 114 of the support 11 excluding the opening of the first cell 111a and a portion of the outer surface 112 of the support 11 near the end face 114, but does not substantially cover the inner surface of the first cell 111a. The sealing portion 21 extends in a substantially cylindrical shape in the longitudinal direction on the outer surface 112 of the support 11 from the end face 114 of the support 11, and extends toward the center in the longitudinal direction beyond a boundary 124 between a membrane end portion 122 and a membrane center portion 123.

[0051] In other words, the plugging portion 21 covers the outer surface 112 of the support 11, which is the surface opposite to the surface in contact with the membrane end portion 122 (i.e., the inner surface of the first cell 111a) at the portion where the membrane end portion 122 is located. Furthermore, on the outer surface 112 of the support 11, the plugging portion 21 extends from a position facing the membrane end portion 122 across the support 11 to a position facing the membrane central portion 123 across the support 11. In further words, the plugging portion 21 covers the entire region of the outer surface 112 of the support 11 that overlaps with the membrane end portion 122 in the radial direction centered on the central axis of the separation membrane composite 1 (i.e., an imaginary line extending longitudinally through the center of both end surfaces 114 of the separation membrane composite 1), and covers a portion of the region that overlaps with the membrane central portion 123 in the radial direction (i.e., the region near the boundary 124 in the longitudinal direction).

[0052] FIG. 6 is an enlarged cross-sectional view showing the vicinity of one longitudinal end of the first cell 111a of the separation membrane composite 1. The example shown in FIG. 6 is substantially the same as the example shown in FIG. 5, except that the plugging portion 21 also extends onto the inner surface of the first cell 111a. As in the example shown in FIG. 5, the plugging portion 21 illustrated in FIG. 6 covers a portion of the end surface 114 of the support body 11 excluding the opening of the first cell 111a, and a portion of the outer surface 112 of the support body 11 near the end surface 114. The plugging portion 21 extends in a substantially cylindrical shape in the longitudinal direction on the outer surface 112 of the support body 11 from the end surface 114 of the support body 11, and extends toward the center in the longitudinal direction beyond the boundary 124 between the membrane end portion 122 and the membrane center portion 123.

[0053] Furthermore, plugging portion 21 extends slightly in a substantially cylindrical shape in the longitudinal direction from end face 114 of support 11 on the inner surface of first cell 111a and contacts separation membrane 12. On the inner surface of first cell 111a, the boundary between plugging portion 21 and separation membrane 12 is longitudinal edge 121 of separation membrane 12. Edge 121 of separation membrane 12 is located in the longitudinal direction between the edge of plugging portion 21 on the outer surface 112 of support 11 (i.e., the edge opposite end face 114 of support 11) and end face 114 of support 11. In the example shown in FIG. 6, the longitudinal length of separation membrane 12 (i.e., the longitudinal distance between both edges 121 of separation membrane 12) is slightly shorter than the longitudinal length of support 11.

[0054] In the separation membrane 12 shown in Figures 5 and 6, defects 125 of a predetermined size are intentionally provided in the membrane end portion 122 when the separation membrane 12 is formed on the support 11 in a manufacturing method of the separation membrane composite 1, which will be described later. In Figures 5 and 6, the defects 125 are depicted larger than they actually are. Furthermore, although Figures 5 and 6 depict multiple defects 125 that are approximately uniformly distributed in the longitudinal direction in the membrane end portion 122, the number, arrangement, size, etc. of the defects 125 may be modified in various ways.

[0055] The defects 125 are pores (for example, gaps or cracks at grain boundaries) that are significantly larger than the above-mentioned pores of the separation membrane 12. When the separation membrane composite 1 is used to separate a mixed gas, the pores of the separation membrane 12 allow a gas with high permeability (hereinafter also referred to as a "high permeability gas") in the mixed gas to pass through, but do not substantially allow a gas with low permeability (hereinafter also referred to as a "low permeability gas") to pass through. On the other hand, the defects 125 allow not only the high permeability gas in the mixed gas to pass through, but also the low permeability gas. In the separation membrane 12, the defects 125 are not intentionally provided in the membrane center portion 123.

[0056] For example, when CF4 gas is used as the low-permeability gas, the average permeation flow rate of CF4 gas at one membrane end 122 in the longitudinal direction is 5 to 100 times, preferably 5 to 50 times, the average permeation flow rate of CF4 gas at the membrane center 123. Similarly, the average permeation flow rate of CF4 gas at the other membrane end 122 in the longitudinal direction is 5 to 100 times, preferably 5 to 50 times, the average permeation flow rate of CF4 gas at the membrane center 123. The average permeation flow rate at the membrane end 122 is the average value of the permeation flow rates at each position across the entire membrane end 122. The average permeation flow rate at the membrane center 123 is the average value of the permeation flow rates at each position across the entire membrane center 123.

[0057] Next, an example of the flow of manufacturing the separation membrane composite 1 will be described with reference to Fig. 7 and Figs. 8A to 8H. Fig. 7 is a diagram showing the flow of manufacturing the separation membrane composite 1. Figs. 8A to 8H are cross-sectional views showing a part of the separation membrane composite 1 in the process of manufacturing. Figs. 8A to 8H show an enlarged view of the vicinity of the longitudinal end of the first cell 111a, and the cross section is simplified and conceptually shown to facilitate understanding of the drawings.

[0058] When the separation membrane composite 1 is manufactured, first, a support 11 having plugs 21 provided at its longitudinal ends is prepared, as shown in Fig. 8A. In the example shown in Fig. 8A, the shape of the plugs 21 is the same as that shown in Fig. 5, and no plugs 21 are provided on the inner surface of the first cell 111a.

[0059] Next, as shown in FIG. 8B , one longitudinal end of the support 11 is brought into contact with the pretreatment liquid 71 (step S11). Similarly, the other longitudinal end of the support 11 is brought into contact with the pretreatment liquid 71. The support 11 is brought into contact with the pretreatment liquid 71, for example, by immersing the longitudinal end of the support 11 in the pretreatment liquid 71 stored in a container 72. The pretreatment liquid 71 is a liquid for forming defects 125 in the above-described film end 122, and is, for example, water. The pretreatment liquid 71 may be a liquid other than water as long as it has a lower seed crystal concentration than a dispersion liquid in which seed crystals are dispersed, as described below. The seed crystal concentration in the pretreatment liquid 71 is preferably 50% or less of the seed crystal concentration in the dispersion liquid, more preferably 20% or less, and particularly preferably 10% or less, and may be 0%. This makes it easier to control the density of seed crystals attached to the end of the support 11 in step S12, as described below. The solvent of the pretreatment liquid 71 is, for example, water or an alcohol such as ethanol, but the solvent of the pretreatment liquid 71 may also be other liquids.

[0060] In step S11, the end of the support 11 that is brought into contact with the pretreatment liquid 71 is a portion extending from the longitudinal edge (i.e., the end surface 114) of the support 11 to 1 / 10 or less of the longitudinal length of the support 11. The longitudinal length of the end that is brought into contact with the pretreatment liquid 71 is preferably 1 / 15 or less, more preferably 1 / 20 or less, of the longitudinal length of the support 11. This allows defects 125 to be formed at the end of the support 11, and in step 22 described below, the mixed gas that passes through the defects 125 and flows out to the permeation side can more efficiently function as a sweep gas. In step S11, the pretreatment liquid 71 adheres to the entire or part of the region on the inner surface of the first cell 111a where the membrane end 122 will be placed in a subsequent step. The support 11 is then lifted from the container 72 in which the pretreatment liquid 71 is stored. After being pulled out of the container 72, the support 11 is impregnated with and retains the pretreatment liquid 71 in the pores at the longitudinal end of the support 11, as shown in Fig. 8C. In Fig. 8C, the portion of the support 11 impregnated with the pretreatment liquid 71 is indicated by hatching that is different from the other portions. Note that the support 11 may be brought into contact with the pretreatment liquid 71 in step S11 by a method other than immersion.

[0061] 8D and 8E, a dispersion 74 in which seed crystals 73 (i.e., zeolite seed crystals) used to form the separation membrane 12 are dispersed in a solvent is brought into contact with the support 11, and the seed crystals 73 are attached to the support 11 (step S12). In FIGS. 8D and 8E, the size of the seed crystals 73 is drawn larger than the actual size (the same applies to FIGS. 8F and 8G).

[0062] The support 11 is brought into contact with the dispersion liquid 74 by, for example, immersing the support 11 in the dispersion liquid 74 stored in a container 75. In step S12, the surface of the support 11 except for the inner surfaces of the first cells 111a is covered with a resin film or the like (not shown). Therefore, the seed crystals are attached only to the inner surfaces of the first cells 111a of the surface of the support 11. Note that the seed crystals may be attached to the inner surfaces of the first cells 111a by other methods.

[0063] The dispersion liquid 74 is prepared by dispersing seed crystals 73 in a solvent (for example, water or an alcohol such as ethanol) in advance. The solvent of the dispersion liquid 74 may be the same as or different from the solvent of the pretreatment liquid 71. The seed crystals 73 are generated in advance, for example, by the following procedure. In generating the seed crystals 73, first, raw materials such as a Si source and a structure-directing agent (hereinafter also referred to as "SDA") are dissolved or dispersed in a solvent to prepare a raw material solution of the seed crystals. Subsequently, hydrothermal synthesis is performed on the raw material solution, and the obtained crystals are washed and dried to obtain zeolite powder. The zeolite powder may be used as the seed crystals 73 as is, or the seed crystals 73 may be obtained by processing the powder by pulverization or the like.

[0064] In step S12, the pretreatment liquid 71 is previously attached to the longitudinal end portion of the support 11 that is immersed in the dispersion liquid 74. Therefore, as shown in Fig. 8E, the density of the seed crystals 73 attached to the inner surfaces of the first cells 111a at the end portion of the support 11 is lower than the density of the seed crystals 73 attached to the inner surfaces of the first cells 111a in portions other than the end portion (i.e., portions to which the pretreatment liquid 71 is not attached).

[0065] After step S12 is completed, the support 11 is pulled out of the container 75 storing the dispersion liquid 74 and dried. As a result, as shown in FIG. 8F , a seed crystal-attached support is obtained in which the seed crystals 73 are attached to the inner surfaces of the first cells 111a of the support 11. Even in this seed crystal-attached support, the density of the seed crystals 73 attached to the inner surfaces of the first cells 111a at the longitudinal end portions of the support 11 is lower than the density of the seed crystals 73 attached to the inner surfaces of the first cells 111a in portions other than the end portions.

[0066] Next, as shown in FIG. 8G, the support 11 with the seed crystal 73 attached thereto is immersed in a raw material solution 76 stored in a container 77. The raw material solution 76 is prepared in advance by dissolving, for example, a Si source and SDA in a solvent. The solvent for the raw material solution is, for example, water or an alcohol such as ethanol. The SDA contained in the raw material solution is, for example, an organic substance. For example, 1-adamantanamine can be used as the SDA.

[0067] Then, by growing zeolite using the seed crystals 73 as nuclei by hydrothermal synthesis, separation membrane 12, which is a zeolite membrane, is formed on the inner surface of first cell 111a of support 11, as shown in FIG. 8H (step S13). The temperature during hydrothermal synthesis is preferably 120 to 200°C, for example, 160°C. The hydrothermal synthesis time is preferably 5 to 100 hours, for example, 30 hours. In separation membrane 12 formed in step S13, the above-mentioned defects 125 are formed at the longitudinal end where the attachment density of seed crystals 73 was low (i.e., the portion included in membrane end 122), and defects 125 are not intentionally formed in portions other than these ends.

[0068] After the hydrothermal synthesis is completed, the support 11 and the separation membrane 12 are washed with pure water. The washed support 11 and the 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 (i.e., calcined) to almost completely burn off the SDA in the separation membrane 12 and open up the micropores in the separation membrane 12. This results in the above-described separation membrane composite 1 (step S14). In the separation membrane composite 1 obtained in step S14, as described above, defects 125 are formed at the longitudinal ends of the separation membrane 12 (i.e., the portions included in the membrane ends 122), and defects 125 are not intentionally formed in portions of the separation membrane 12 other than these ends. Note that in the production of the separation membrane composite 1, the plugging portions 21 may be provided after the separation membrane 12 is formed.

[0069] Next, with reference to Figs. 9 and 10, the separation of a mixed gas using the separation membrane composite 1 will be described. Fig. 9 is a cross-sectional view showing a mixed gas separation device 2 (hereinafter also simply referred to as "separation device 2"). In Fig. 9, the cross section of the separation membrane composite 1 is shown in a simplified conceptual form to facilitate understanding of the drawing. Fig. 10 is a diagram showing the flow of mixed gas separation by the separation device 2.

[0070] In the separation device 2, a mixed gas containing multiple types of gases is supplied to the separation membrane composite 1, and a highly permeable gas in the mixed gas is separated from the mixed gas by permeating through the separation membrane composite 1. Separation in the separation device 2 may be performed, for example, for the purpose of extracting a highly permeable gas from the mixed gas, or for the purpose of concentrating a low-permeable gas.

[0071] The mixed gas may contain one or more substances selected from the group consisting of hydrogen (H), helium (He), nitrogen (N), oxygen (O), water (H), O, carbon monoxide (CO), carbon dioxide (CO), nitrogen oxides, ammonia (NH), sulfur oxides, hydrogen sulfide (H), sulfur fluoride, mercury (Hg), arsine (AsH), hydrogen cyanide (HCN), carbonyl sulfide (COS), C to C hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. The highly permeable gas may be one or more substances selected from the group consisting of CO, NH, and H. The mixed gas and highly permeable gas may be substances other than those listed above.

[0072] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5), etc. X It is a substance called NOX.

[0073] Sulfur oxides are compounds of sulfur and oxygen. Examples of sulfur oxides include sulfur dioxide (SO2), sulfur trioxide (SO3), and other sulfur compounds. X It is a substance called SOX.

[0074] Sulfur fluoride is a compound of fluorine and sulfur. The sulfur fluoride may be, for example, disulfur difluoride (FSSF, S=SF), sulfur difluoride (SF), sulfur tetrafluoride (SF), sulfur hexafluoride (SF), or disulfur decafluoride (SF). 10 ) etc.

[0075] C1-C8 hydrocarbons are hydrocarbons with one or more carbon atoms and eight or less. C3-C8 hydrocarbons may be straight-chain compounds, branched-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be saturated hydrocarbons (i.e., those without double or triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double and / or triple bonds in the molecule). Examples of C1-C4 hydrocarbons include methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), normal butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), and isobutene (CH2=C(CH3)2).

[0076] The organic acid may be a carboxylic acid or a sulfonic acid. Examples of the carboxylic acid include formic acid (CHO), acetic acid (CHO), oxalic acid (CHO), acrylic acid (CHO), or benzoic acid (CHCOOH). Examples of the sulfonic acid include ethanesulfonic acid (CHOS). The organic acid may be a chain compound or a cyclic compound.

[0077] 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).

[0078] Mercaptans are organic compounds with hydrogenated sulfur (SH) at the end, also known as thiols or thioalcohols. Examples of the mercaptans include methyl mercaptan (CHSH), ethyl mercaptan (CHSH), and 1-propanethiol (CHSH).

[0079] The esters mentioned above are, for example, formates or acetates.

[0080] The above-mentioned ethers are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3) or diethyl ether ((C2H5)2O).

[0081] The ketone may be, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO).

[0082] The aldehydes mentioned above are, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO) or butanal (butyraldehyde) (C3H7CHO).

[0083] As shown in FIG. 9, the separation device 2 includes a separation membrane composite 1, a sealing unit 21, a housing 22, and two sealing members 23. The sealing unit 21 may be considered to be included in the separation membrane composite 1. The separation membrane composite 1, the sealing unit 21, and the sealing members 23 are housed in the housing 22. In FIG. 9, the separation membrane 12 of the separation membrane composite 1 is indicated by hatching. The internal space of the housing 22 is a sealed space isolated from the space surrounding the housing 22. A supply unit 26, a first recovery unit 27, and a second recovery unit 28 are connected to the housing 22.

[0084] As described above, the sealing portions 21 are attached to both ends of the support body 11 in the longitudinal direction (i.e., the left-right direction in FIG. 9 ), and are members that cover and seal both end faces 114 of the support body 11 in the longitudinal direction and parts of the outer surface 112 near the both end faces 114. In this embodiment, the sealing portions 21 are glass seals with a thickness of 10 μm to 50 μm. The material and shape of the sealing portions 21 may be changed as appropriate. Note that the sealing portions 21 are provided with a plurality of openings that overlap with the plurality of first cells 111a of the support body 11, and therefore both ends of each first cell 111a in the longitudinal direction are not covered by the sealing portions 21. Therefore, fluid can flow in and out of the first cells 111a from the both ends.

[0085] The housing 22 is a substantially cylindrical tubular member. The housing 22 is made of, for example, stainless steel or carbon steel. The longitudinal direction of the housing 22 is substantially parallel to the longitudinal direction of the separation membrane composite 1. A supply port 221 is provided at one longitudinal end of the housing 22 (i.e., the left end in FIG. 9 ), and a first discharge port 222 is provided at the other end. 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 discharge port 223 is provided on a side surface of the housing 22. A second collection unit 28 is connected to the second discharge port 223. The shape and material of the housing 22 may be modified in various ways.

[0086] The two seal members 23 are disposed near both longitudinal ends of the separation membrane composite 1, between the outer surface 112 of the separation membrane composite 1 and the inner surface of the housing 22. At each longitudinal end of the separation membrane composite 1, the seal members 23 are located between the slits 117 and the end surface 114 of the separation membrane composite 1 in the longitudinal direction. Each seal member 23 is a substantially annular member made of a material that is impermeable to gases and liquids. The seal members 23 are, for example, O-rings or packings made of flexible resin.

[0087] The sealing members 23 are in close contact with the outer surface 112 of the separation membrane composite 1 and the inner surface of the housing 22 around the entire periphery in the circumferential direction (hereinafter simply referred to as the "circumferential direction") around the central axis of the separation membrane composite 1. In the example shown in FIG. 9, the sealing members 23 are in close contact with the outer surfaces of the sealing portions 21 and indirectly contact the outer surface 112 of the separation membrane composite 1 via the sealing portions 21. The sealing members 23 may also be in direct contact with the outer surface 112 of the separation membrane composite 1. The gaps between each sealing member 23 and the outer surface 112 of the separation membrane composite 1 or the sealing portions 21, and between each sealing member 23 and the inner surface of the housing 22 are sealed, so that gas and liquid cannot pass through. The material of the sealing members 23 may be carbon, metal, or other inorganic materials in addition to resin.

[0088] Supply unit 26 supplies the mixed gas to the internal space of housing 22 via supply port 221. Supply unit 26 includes a pressure-feeding mechanism such as a blower or pump that pressure-feeds the mixed gas toward housing 22. The pressure-feeding mechanism includes, for example, a temperature adjustment unit and a pressure adjustment unit that respectively adjust the temperature and pressure of the mixed gas supplied to housing 22. First recovery unit 27 and second recovery unit 28 include, for example, a storage container that stores the gas drawn out from housing 22, or a blower or pump that transports the gas.

[0089] When separating a mixed gas, first, a separation membrane composite 1 is prepared (FIG. 10: step S21). Specifically, the separation membrane composite 1 is attached inside the housing 22. Next, a mixed gas containing multiple types of gases with different permeabilities to the separation membrane 12 is supplied by the supply unit 26 into the interior of the housing 22 (specifically, into the space to the left of the left end face 114 of the separation membrane composite 1) as indicated by arrow 251 in FIG. 9. For example, the main components of the mixed gas are CO2 and N2. The mixed gas may contain gases other than CO2 and N2. The pressure of the mixed gas supplied from the supply unit 26 to the interior of the housing 22 (i.e., the introduction pressure) is, for example, 0.1 MPa to 20.0 MPa. The temperature of the mixed gas supplied from the supply unit 26 is, for example, 10°C to 250°C.

[0090] The mixed gas supplied from the supply unit 26 into the housing 22 flows into each first cell 111a of the separation membrane composite 1. The highly permeable gas in the mixed gas permeates from the first cell 111a through the separation membrane 12 and the support 11, as indicated by arrow 252a, and is discharged from the outer surface 112 of the separation membrane composite 1 to the separation space 220. The highly permeable gas that permeates from the first cell 111a through the separation membrane 12 and the support 11 and flows into the second cell 111b, as indicated by arrow 252b, flows out into the separation space 220 through the slit 117, as indicated by arrow 252c. The highly permeable gas that flows from the first cell 111a to the second cell 111b may also be discharged into the separation space 220 by permeating the support 11 without passing through the slit 117.

[0091] FIG. 11 is an enlarged cross-sectional view showing the vicinity of the longitudinal end of the first cell 111a. As described above, in the separation membrane composite 1, a defect 125 is provided in the membrane end 122 of the separation membrane 12. As shown in FIG. 11, the mixed gas supplied to the first cell 111a flows through the defect 125 to the permeate side of the separation membrane 12 (i.e., the side opposite the internal space of the first cell 111a), flows through the pores of the support 11 along the membrane center 123 as indicated by arrow 255, and then flows toward the separation space 220. As a result, the highly permeable gas that has permeated the membrane center 123 of the separation membrane 12 from the first cell 111a is carried by the mixed gas that has flowed from the membrane end 122 to the permeate side and is rapidly discharged to the separation space 220. In other words, the mixed gas that has flowed from the membrane end 122 to the permeate side acts as a sweep gas flowing through the permeate side of the separation membrane 12. This reduces the partial pressure of the highly permeable gas on the permeate side of separation membrane 12, accelerating the movement of the highly permeable gas from the supply side of separation membrane 12 (ie, the internal space of first cell 111a) to the permeate side.

[0092] As described above, the plugging portion 21 extends from a position facing the membrane end portion 122 across the support 11 to a position facing the membrane center portion 123 across the support 11. In other words, the plugging portion 21 extends to the longitudinal center side of the boundary 124 between the membrane end portion 122 and the membrane center portion 123. This prevents the mixed gas that passes through the defect 125 in the membrane end portion 122 and flows out to the permeation side from immediately heading toward the separation space 220, increasing the distance that the mixed gas flows along the membrane center portion 123. As a result, the mixed gas functions more effectively as a sweep gas, further promoting the movement of the high-permeability gas from the supply side to the permeation side of the separation membrane 12.

[0093] 9, as described above, the high-permeability gas permeates the separation membrane 12 and is led to the separation space 220, whereby the high-permeability gas (e.g., CO2) is separated from other substances in the mixed gas, such as the low-permeability gas (e.g., N2) (step S22). Note that, as described above, in the separation membrane composite 1, the end face 114 of the support 11 is covered with the sealing portion 21, and therefore the mixed gas containing the low-permeability gas is prevented or suppressed from entering the inside of the support 11 through the end face 114 and entering the separation space 220 without permeating the separation membrane 12.

[0094] The gas discharged into the separation space 220 (hereinafter referred to as "permeate gas") is guided to the second recovery section 28 via the second discharge port 223 and recovered, as indicated by the arrow 253 in FIG. 9. The second recovery section 28 is a permeate gas recovery section that recovers the permeate gas from the mixed gas that has permeated through the separation membrane 12. The permeate gas may include, in addition to the high permeate gas described above, a low permeate gas that has permeated through the separation membrane 12.

[0095] Furthermore, the gas mixture excluding the gas that has permeated separation membrane 12 and support 11 (hereinafter referred to as "non-permeated gas") flows from left to right in FIG. 9 within first cell 111a and is guided to first recovery section 27 via first discharge port 222 as indicated by arrow 254 and recovered. First recovery section 27 is a non-permeated gas recovery section that recovers the non-permeated gas of the mixed gas that has not permeated separation membrane 12. The non-permeated gas recovered by first recovery section 27 may include, in addition to the low-permeability gas described above, a high-permeability gas that has not permeated separation membrane 12. The non-permeated gas recovered by first recovery section 27 may be circulated to supply section 26 and supplied again into housing 22, for example.

[0096] Next, with reference to Table 1, the performance of the separation membrane composites 1 of Examples 1 to 3 and Comparative Examples 1 and 2 will be described.

[0097] [Table 1]

[0098] In Example 1, a separation membrane composite 1 was produced by a manufacturing method similar to steps S11 to S14 described above. In step S11, a 10 mm area from the end face 114 of the support 11 on both sides in the longitudinal direction was immersed in water, which is the pretreatment liquid 71, for 1 minute. The outer diameter of the support 11 was 30 mm, and the length of the support 11 and the length of the separation membrane 12 were 160 mm. The separation membrane 12 in each of the first cells 111a was a DDR-type zeolite membrane. The inner diameter of each of the first cells 111a was 2.0 mm.

[0099] In Example 1, the density of the separation membrane 12 before SDA removal was evaluated between steps S13 and S14. In this evaluation, the separation membrane composite 1 before SDA removal was attached to the inside of the housing 22 of the separation device 2, and N2 gas (single component gas) was supplied from the supply unit 26. The amount of N2 gas recovered in the second recovery unit 28 was then measured, and the permeation flow rate of the N2 gas (nmol / m 2 In Table 1, the permeation flow rate of N2 gas was 0.005 nmol / m2 s Pa is indicated by "◎", and 0.005 nmol / m 2 s Pa or more and 0.01 nmol / m 2 s Pa is indicated by "○", and 0.01 nmol / m 2 s Pa or more and 0.05 nmol / m 2 s Pa is indicated by "△", and values ​​below 0.05 nmol / m 2 ·s·P After a If it is above, it is indicated by "x".

[0100] In Example 1, a CO2 separation test was conducted after step S14. In the CO2 separation test, the separation membrane composite 1 after SDA removal was installed inside the housing 22 of the separation device 2, and a mixed gas containing 10% by volume of CO2 gas and 90% by volume of N2 gas was supplied from the supply unit 26. The mixed gas supplied from the supply unit 26 to the inside of the housing 22 was set to a pressure of 1 MPa and a flow rate of 20 NL / min. The pressure of the permeable gas recovered by the second recovery unit 28 was set to atmospheric pressure. The flow rate and CO2 concentration of the permeable gas recovered by the second recovery unit 28 were then measured to determine the CO2 recovery rate.

[0101] In Example 1, the ratio of the average permeation flow rate of CF4 gas at the membrane end 122 to the average permeation flow rate of CF4 gas at the membrane center 123 (hereinafter also referred to as the "end permeation rate") was determined. Specifically, the separation membrane composite 1 after SDA removal was installed inside the housing 22 of the separation device 2, and CF4 gas (single component gas) was supplied from the supply unit 26. The pressure of the CF4 gas supplied from the supply unit 26 to the inside of the housing 22 was set to 0.4 MPa. The pressure of the permeate gas recovered by the second recovery unit 28 was set to atmospheric pressure. The amount of CF4 gas recovered by the second recovery unit 28 was then measured, and the permeation flow rate of the CF4 gas was determined. This permeation flow rate is the average permeation flow rate of the entire separation membrane 12 (i.e., the average value of the permeation flow rates at each position throughout the separation membrane 12), and is hereinafter also referred to as the "overall permeation flow rate."

[0102] Next, on both sides of the separation membrane composite 1 in the longitudinal direction, the entire inner surface of the membrane end 122 of the separation membrane 12 (i.e., the surface opposite to the support 11) is , covered The coating membrane seals the separation membrane 12 to a state where gas permeation is substantially impossible. The coating membrane is a thin film member having a layered microstructure formed from a layered inorganic compound. The coating membrane is formed, for example, from a clay mineral such as smectite. The membrane end 122 refers to the area of ​​the separation membrane 12 that is 16 mm from the end surface 114 of the support 11.

[0103] Then, in the same manner as when the overall permeation flow rate was calculated, the separation membrane composite 1 with the sealed membrane end 122 was installed inside the housing 22 of the separation device 2, and CF4 gas was supplied from the supply unit 26 to calculate the permeation flow rate of the CF4 gas. This permeation flow rate was the average permeation flow rate across the entire membrane center 123, and hereinafter also referred to as the "membrane center permeation flow rate." Subsequently, the overall permeation flow rate and the membrane center permeation flow rate were used to calculate the "membrane end permeation flow rate," which is the average permeation flow rate across the entire membrane end 122, and the membrane end permeation flow rate was divided by the membrane center permeation flow rate to calculate the end permeation rate.

[0104] In Example 1, the end permeation ratio was 49.6 times, the denseness of the separation membrane 12 was evaluated as "Excellent", and the CO2 recovery rate was 67.1%. A CO2 recovery rate of 50% or more is preferable, and the CO2 recovery rate in Example 1 was high.

[0105] In Examples 2 and 3 and Comparative Examples 1 and 2, separation membrane composite 1 was obtained using substantially the same procedures as in Example 1, except for the changes described below, and the performance of separation membrane composite 1 was evaluated using the same procedures as in Example 1.

[0106] In Example 2, the immersion time of the support 11 in water in step S11 was changed to 0.2 minutes. In Example 2, the end permeation rate was 5.2 times, the denseness of the separation membrane 12 was evaluated as "◎", and the CO2 recovery rate was high at 50.2%.

[0107] In Example 3, the immersion time of the support 11 in water in step S11 was changed to 2 minutes. In Example 3, the end permeation ratio was 98.0 times, the denseness of the separation membrane 12 was evaluated as "○", and the CO recovery rate was high at 77.4%.

[0108] In Comparative Example 1, the immersion of the support 11 in water in step S11 was omitted. As a result, in Comparative Example 1, excessive seed crystals adhered to the region of the support 11 where the membrane end 122 was to be formed, resulting in insufficient formation of defects 125 at the membrane end 122, resulting in a low end permeation rate of 1.2 times. In addition, the density of the separation membrane 12 was evaluated as "Excellent", and the CO2 capture rate was low at 43.7%.

[0109] In Comparative Example 2, the immersion of the support 11 in water in step S11 was omitted, and between steps S12 and S13, the end of the support 11 to which the seed crystals were attached was immersed in water and ultrasonic waves were applied. As a result, in Comparative Example 2, an excessive proportion of the seed crystals was removed from the region of the support 11 where the membrane end 122 was to be formed, and therefore the density of the separation membrane 12 was evaluated as "X". Furthermore, in Comparative Example 2, the end permeation ratio was excessively high at 903.5 times. Note that, since the density of the separation membrane 12 in Comparative Example 2 was very low, the CO2 capture rate was not measured.

[0110] Comparing Examples 1 to 3 with Comparative Example 1, from the viewpoint of increasing the CO2 recovery rate (for example, 50% or more), it is preferable that the end permeation rate is 5 times or more.

[0111] Comparing Examples 1 to 3 with Comparative Example 2, from the viewpoint of ensuring the denseness of separation membrane 12, it is preferable that the end permeation ratio is 100 times or less.

[0112] Furthermore, when Examples 1 to 3 are compared, from the viewpoint of improving the density of separation membrane 12, the end permeation ratio is preferably set to 50 times or less.

[0113] As described above, the separation membrane composite 1 includes a porous support 11 and a separation membrane 12 provided on the support 11. In the separation membrane composite 1, the portions of the separation membrane 12 ranging from both longitudinal edges to 1 / 10 of the longitudinal length of the separation membrane 12 are defined as membrane end portions 122, and the portion of the separation membrane 12 excluding the membrane end portions 122 on both longitudinal sides is defined as a membrane center portion 123. The average permeation flow rate of CF4 gas at one membrane end portion 122 is 5 to 100 times the average permeation flow rate of CF4 gas at the membrane center portion 123.

[0114] In this way, by setting the end permeation ratio at one membrane end 122 in the longitudinal direction to be 5 times or more and 100 times or less, the density of the separation membrane 12 is ensured, as described above, and the gas flowing out from the one membrane end 122 to the permeate side functions favorably as a sweep gas flowing through the permeate side of the separation membrane 12. As a result, the separation performance of the separation membrane composite 1 can be improved. Note that the gas flowing out from the membrane end 122 to the permeate side includes a mixed gas that has passed through defects 125, etc., of the membrane end 122, and a highly permeable gas that has permeated the zeolite membrane of the membrane end 122. The same applies to the following explanation.

[0115] Preferably, the average permeation flow rate of CF4 gas at the one membrane end 122 is 5 to 50 times the average permeation flow rate of CF4 gas at the membrane center 123. This can improve the density of the separation membrane 12.

[0116] As described above, the average permeation flow rate of CF4 gas at the other membrane end 122 is preferably 5 to 100 times the average permeation flow rate of CF4 gas at the membrane center 123. In this way, by setting the end permeation rate at the membrane end 122 to 5 to 100 times on both the upstream and downstream sides of the mixed gas flow in the first cell 111a, the separation performance of the separation membrane composite 1 can be further improved. Specifically, on the upstream side where the partial pressure of the highly permeable gas in the mixed gas is relatively high, the gas flowing out from the upstream membrane end 122 to the permeation side acts as a sweep gas, which favorably promotes permeation of the highly permeable gas in the upstream part of the membrane center 123 and increases the amount of the highly permeable gas permeating the separation membrane 12. Furthermore, at the downstream side where the partial pressure of the highly permeable gas in the mixed gas is relatively low, the gas flowing out from the downstream membrane end 122 to the permeation side acts as a sweep gas, thereby allowing the separation membrane 12 to function properly even in the downstream portion of the membrane center 123, and increasing the amount of highly permeable gas that permeates the separation membrane 12.

[0117] More preferably, the average permeation flow rate of CF4 gas at the other membrane end portion 122 is 5 to 50 times the average permeation flow rate of CF4 gas at the membrane center portion 123. This can further improve the density of the separation membrane 12.

[0118] As described above, a plugging portion 21 is preferably provided at the portion of the support 11 where the one membrane end portion 122 is located, covering and sealing the surface opposite to the surface in contact with the one membrane end portion 122. The plugging portion 21 preferably extends from a position facing the one membrane end portion 122 across the support 11 to a position facing the membrane center portion 123 across the support 11. This increases the distance that the gas flowing from the one membrane end portion 122 to the permeate side flows through the pores of the support 11 along the separation membrane 12. As a result, the separation performance of the separation membrane composite 1 can be further improved.

[0119] More preferably, a plugging portion 21 is provided at the portion of the support 11 where the other membrane end portion 122 is located, covering and sealing the surface opposite to the surface in contact with the other membrane end portion 122. The plugging portion 21 preferably extends from a position facing the other membrane end portion 122 across the support 11 to a position facing the membrane center portion 123 across the support 11. This increases the distance that the gas flowing from the other membrane end portion 122 to the permeate side flows through the pores of the support 11 along the separation membrane 12. As a result, the separation performance of the separation membrane composite 1 can be further improved.

[0120] As described above, the separation membrane 12 is preferably a zeolite membrane. By forming the separation membrane 12 from zeolite crystals with uniform pore diameters, selective permeation of highly permeable gases can be suitably achieved. As a result, highly permeable gases can be efficiently separated from mixed gases.

[0121] More preferably, the maximum number of ring members of the zeolite constituting the zeolite membrane is 8 or less. This allows for more favorable selective permeation of highly permeable gases with relatively small molecular diameters, such as CO. As a result, highly permeable gases can be separated from mixed gases more efficiently.

[0122] As described above, the support 11 is preferably cylindrical and extends longitudinally, and the separation membrane 12 is preferably disposed on the inner surface of a membrane-forming cell (i.e., the first cell 111a) that penetrates the support 11 in the longitudinal direction. In the separation membrane composite 1, as described above, the sweep gas can be supplied from the membrane end 122 of each first cell 111a. Therefore, even in first cells 111a in positions where the permeation-promoting effect of the sweep gas is not as pronounced when the sweep gas is flowed along the outer surface 112 of the separation membrane composite 1 (for example, first cells 111a located near the center in a cross section perpendicular to the longitudinal direction of the separation membrane composite 1), the sweep gas can be efficiently supplied near the separation membrane 12. As a result, the separation performance of the separation membrane composite 1 can be further improved.

[0123] The separation device 2 described above includes the separation membrane composite 1 and a housing 22 that accommodates the separation membrane composite 1. A supply section 26, a permeate gas recovery section (i.e., second recovery section 28), and a non-permeate gas recovery section (i.e., first recovery section 27) are connected to the housing 22. The supply section 26 supplies a mixed gas containing multiple types of gases to the separation membrane composite 1. The second recovery section 28 recovers permeate gas from the mixed gas that has permeated through the separation membrane 12. The first recovery section 27 recovers non-permeate gas from the mixed gas that has not permeated through the separation membrane 12. As described above, the separation device 2 can efficiently separate mixed gases.

[0124] Such a separator 2 is particularly suitable for use in a gas mixture containing 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, mercaptans, esters, ethers, ketones, and aldehydes.

[0125] The method for producing the separation membrane composite 1 described above includes the steps of: bringing a dispersion 74, in which zeolite seed crystals 73 are dispersed, into contact with a porous support 11 to adhere the seed crystals 73 to the support 11 (step S12); immersing the support 11 with the adhered seed crystals 73 in a raw material solution 76 and growing zeolite from the seed crystals 73 by hydrothermal synthesis to form a separation membrane 12, which is a zeolite membrane, on the support 11 (step S13); and, prior to step S12, bringing a portion of the support 11, extending from a longitudinal edge to 1 / 10 or less of the longitudinal length of the support 11, into contact with a liquid (i.e., pretreatment liquid 71) having a lower concentration of the seed crystals 73 than the dispersion 74. This makes it possible to provide a separation membrane composite 1 with improved separation performance, as described above.

[0126] The above-described separation membrane composite 1, separation device 2, and method for manufacturing the separation membrane composite 1 can be modified in various ways.

[0127] For example, the sealing portion 21 does not necessarily need to extend on the outer surface 112 of the support 11 from a position facing the membrane end portion 122 across the support 11 to a position facing the membrane center portion 123 across the support 11, but may be provided only at a position facing the membrane end portion 122 across the support 11. Alternatively, the sealing portion 21 does not need to be provided on the outer surface 112 of the support 11.

[0128] In the separation membrane composite 1, as long as the end permeation rate at one membrane end 122 of the separation membrane 12 is 5 times or more and 100 times or less, the end permeation rate at the other membrane end 122 may be less than 5 times or more than 100 times.

[0129] In the separation membrane composite 1, the maximum number of membered rings of the zeolite constituting the separation membrane 12, which is a zeolite membrane, may be greater than 8. Furthermore, the separation membrane 12 is not limited to a zeolite membrane and may be an inorganic membrane such as a silica membrane or a carbon membrane, or an organic membrane such as a polyimide membrane or a silicone membrane. In addition to the separation membrane 12, 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 a zeolite membrane, an inorganic membrane other than a zeolite membrane, or an organic membrane.

[0130] The structure of the separation membrane composite 1 is not limited to the above example and may be modified in various ways. For example, the slits 117 penetrating the plurality of second cells 111b may be omitted. Furthermore, the plurality of cells 111 provided in the support 11 do not necessarily have to include the second cells 111b with both longitudinal ends plugged, and both ends of all the cells 111 may be open, and the separation membrane 12 may be provided on the inner surface of all the cells 111. In other words, all the cells 111 may be first cells 111a. Furthermore, the number of first cells 111a may be one.

[0131] The separation membrane composite 1 does not necessarily have to be produced by the above-described production method (steps S11 to S14), but may be produced by various other production methods.

[0132] The separation membrane composite 1 may be used to separate a mixed gas in a mixed gas separation apparatus having a structure different from that of the above-described separation apparatus 2. Alternatively, the separation membrane composite 1 may be used to separate a fluid other than a mixed gas (for example, a mixed liquid in which two or more types of liquid are mixed). Furthermore, the separation membrane composite 1 may be combined with a catalyst and used as a membrane reactor.

[0133] The configurations of the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory. [Industrial Applicability]

[0134] The present invention can be used in separation devices for separating various mixed substances.

[0135] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention. [Explanation of symbols]

[0136] 1 Separation membrane complex 2 Separation device 11 Support 12 Separation membrane 21 Sealing part 22 Housing 26 Supply section 27 First Recovery Section 28 Second Recovery Section 71 Pre-treatment liquid 73 Seed Crystal 74 Dispersion 76 Raw material solution 111a Cell 1 121 Edge 122 Membrane edge 123 Membrane center S11~S14, S21~S22 steps

Claims

1. A separation membrane complex, a cylindrical or columnar porous support extending in a longitudinal direction; a cylindrical separation membrane provided on the support and extending in the longitudinal direction; Equipped with The portions of the separation membrane within a range of 1 / 10 of the length of the separation membrane in the longitudinal direction from both end edges of the separation membrane in the longitudinal direction are defined as membrane end portions, and the portion of the separation membrane excluding the membrane end portions on both sides in the longitudinal direction is defined as a membrane center portion, CF at one end of the membrane ４ The average gas permeation flow rate is ４ The flow rate is 5 times or more and 100 times or less than the average permeation flow rate of the gas.

2. The separation membrane composite according to claim 1, CF at one end of the film ４ The average gas permeation flow rate is ４ The flow rate is 5 times or more and 50 times or less the average permeation flow rate of the gas.

3. The separation membrane composite according to claim 1, CF at the other membrane end ４ The average gas permeation flow rate is ４ The flow rate is 5 times or more and 100 times or less than the average permeation flow rate of the gas.

4. The separation membrane composite according to claim 1, a sealing portion is provided in a portion of the support where the one membrane end portion is disposed, the sealing portion covering and sealing a surface opposite to a surface in contact with the one membrane end portion; The sealing portion extends from a position facing the one membrane end portion across the support to a position facing the membrane center portion across the support.

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

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

7. The separation membrane composite according to claim 1, the support body has a columnar shape extending in the longitudinal direction, The separation membrane is disposed on the inner surface of a membrane-forming cell that passes through the support in the longitudinal direction.

8. A mixed gas separation device, comprising: The separation membrane composite according to any one of claims 1 to 7, a housing that accommodates the separation membrane composite; Equipped with The housing includes: a supply unit that supplies a mixed gas containing a plurality of types of gases to the separation membrane composite; a permeation gas recovery section that recovers a permeation gas that has permeated the separation membrane composite from the mixed gas; a non-permeate gas recovery section that recovers non-permeate gas from the mixed gas that has not permeated through the separation membrane composite; is connected.

9. 9. The mixed gas separation apparatus according to claim 8, The mixed gas contains one or more of 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 to C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes.

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