Separation membrane composite, and method for producing separation membrane composite

Abstract

A separation membrane composite (1) comprises: a porous support (11); and a separation membrane (12) which is a film of a metal organic structure provided on the support (11), and which carries amorphous fine particles (126) of an inorganic material in a region between crystal particles (121) of the metal organic structure. This makes it possible to improve separation performance while suppressing a decrease in transmission performance.

Description

Separation membrane composite and method for producing the separation membrane composite

[0001] The present invention relates to a separation membrane composite and a method for manufacturing a separation membrane composite. [Reference to Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2024-25484, filed on February 22, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] In recent years, efforts to become carbon neutral have been underway worldwide, and carbon dioxide (CO ) contained in industrial exhaust gases emitted from factories and other facilities has become a major issue. ２ ) and capture technology (CO ２ / N ２ Meanwhile, metal-organic frameworks (hereinafter also referred to as "MOFs") are porous materials with a large surface area, and by forming membranes on porous supports in the same way as zeolite membranes, they are expected to be used in a variety of applications, such as gas and liquid separation.

[0003] Japanese Patent Laid-Open Publication No. 2018-167150 (Reference 1) discloses a method for filling grain boundaries by forming a grain boundary film using an organic material or MOF at the grain boundaries of an inorganic membrane. In one method described in Reference 1, a solution containing an organic material is added to one space partitioned by an inorganic membrane, and the other space is depressurized, thereby filling the grain boundaries of the inorganic membrane with the organic material. In another method, a first raw material solution of an inorganic material is poured into one space, and a second raw material solution is poured into the other space. The second raw material solution is brought into contact with the first raw material solution at the grain boundaries of the inorganic membrane by diffusion, thereby generating an inorganic material and filling the grain boundaries. Japanese Patent Laid-Open Publication No. 2002-263457 (Reference 2) discloses a method for repairing the grain boundaries of a zeolite membrane using a coupling agent that undergoes hydrolysis and polymerization upon contact with water. In the technique of Document 2, a gaseous coupling agent is supplied to one side of a zeolite membrane, and water or water vapor is supplied to the other side.

[0004] However, in MOF membranes, interactions between crystalline particles do not occur, and reactions do not proceed. This leads to the formation of large gaps between the crystalline particles, making it easy for grain boundary defects to occur. In particular, in thin MOF membranes (e.g., membrane thickness of 2 μm or less), the effect of grain boundary defects becomes significant, making it impossible to achieve high separation performance. While the method described in Reference 1 suggests repairing (filling) grain boundary defects in MOF membranes with organic materials or MOF grain boundary membranes, this method results in the formation of grain boundary membranes over the entire (or a wide area) surface of the MOF membrane, significantly reducing permeation performance. Furthermore, because the grain boundary membrane itself is gas permeable, separation performance is not significantly improved. When a gaseous coupling agent is supplied, as described in Reference 2, the coupling agent has difficulty penetrating into the grain boundary defects, making it impossible to properly repair the grain boundary defects. As a result, the improvement in separation performance is insufficient. Therefore, a method is needed to improve separation performance while suppressing a decrease in permeation performance in a separation membrane composite in which an MOF membrane is provided on a support.

[0005] An object of the present invention is to improve the separation performance of a separation membrane composite while suppressing a decrease in permeation performance.

[0006] A first aspect of the invention is a separation membrane composite, comprising: a porous support; and a separation membrane that is a metal-organic framework membrane provided on the support, the separation membrane carrying amorphous fine particles of an inorganic material in regions between crystalline particles of the metal-organic framework.

[0007] According to the present invention, it is possible to improve separation performance while suppressing a decrease in permeation performance.

[0008] A second aspect of the present invention is the separation membrane composite of the first aspect, wherein the amorphous fine particles include fine particles of zirconia, titania, alumina, or silica.

[0009] A third aspect of the present invention is the separation membrane composite of the first or second aspect, wherein the metal ions that are components of the metal organic framework are Al ３＋ , Co ３＋ , Co ２＋ , Ni ２＋ , Ni ＋ , Cu ２＋ , Cu ＋ , Zn ２＋ , Fe３＋ , Fe ２＋ , Ti ３＋ and Zr ４＋ The composition includes at least one selected from the group consisting of:

[0010] A fourth aspect of the present invention is the separation membrane composite of any one of the first to third aspects, wherein the average thickness of the separation membrane is 2 μm or less.

[0011] A fifth aspect of the invention is the separation membrane composite of any one of the first to fourth aspects, wherein a repair solution containing a repair material that reacts with water to precipitate the amorphous fine particles and an organic solvent having a kinetic molecular diameter smaller than the pore size of the membrane of the metal-organic framework is brought into contact with one surface of the membrane of the metal-organic framework provided on the support, and a gas or liquid containing water is brought into contact with the other surface, thereby forming the amorphous fine particles.

[0012] A sixth aspect of the invention is a method for producing a separation membrane composite, comprising: a) preparing a porous support having a metal-organic framework membrane provided thereon; b) drying the metal-organic framework membrane; and c) contacting one surface of the metal-organic framework membrane with a repair solution containing an organic solvent and a repair material that reacts with water to precipitate amorphous fine particles of an inorganic material, and contacting the other surface of the metal-organic framework membrane with a gas or liquid containing water.

[0013] A seventh aspect of the invention is the method for producing the separation membrane composite of the sixth aspect, wherein in the step c), the repair solution is brought into contact with a surface of the metal organic framework on the membrane opposite to the support.

[0014] An eighth aspect of the invention is the method for producing the separation membrane composite of the sixth or seventh aspect, further comprising, after the step c), a step of contacting the one surface of the membrane of the metal-organic framework with an organic solvent to remove the repair material remaining on the membrane.

[0015] A ninth aspect of the invention is the method for producing a separation membrane composite according to any one of the sixth to eighth aspects, wherein the organic solvent contained in the repair solution has a kinetic molecular diameter smaller than the pore diameter of the membrane of the metal organic framework.

[0016] 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.

[0017] FIG. 1 is a cross-sectional view of a separation membrane composite; FIG. 2 is a cross-sectional view showing an enlarged portion of the separation membrane composite; FIG. 3 is a diagram showing MOF crystal particles that constitute a MOF membrane; FIG. 4 is a diagram showing the flow of manufacturing a separation membrane composite; FIG. 5 is a diagram showing a state in which a repair solution is brought into contact with a MOF membrane; FIG. 6 is a diagram showing a MOF membrane in contact with a repair solution; FIG. 7 is a diagram showing a MOF membrane that has undergone repair treatment according to a comparative example; FIG. 8 is a diagram showing a separation device; FIG. 9 is a diagram showing the flow of separation of a mixed substance.

[0018] FIG. 1 is a cross-sectional view of a separation membrane composite 1. FIG. 2 is a cross-sectional view showing an enlarged portion of the separation membrane composite 1. The separation membrane composite 1 includes a porous support 11 and a separation membrane 12 disposed on the support 11. As described below, the separation membrane 12 is a metal-organic framework (MOF) membrane (hereinafter also referred to as a "MOF membrane") supporting amorphous fine particles of an inorganic material, and the separation membrane composite 1 is a MOF membrane composite. An MOF membrane is at least a membrane of MOFs formed on the surface of the support 11, and does not include a membrane in which MOF particles are simply dispersed in an organic membrane. In FIG. 1, the separation membrane 12 is emphasized with a thick line. In FIG. 2, the separation membrane 12 is indicated by hatching. Also, in FIG. 2, the thickness of the separation membrane 12 is depicted as being thicker than it actually is.

[0019] 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 so-called monolithic support having a single, continuous columnar body formed integrally with the support 11, and a plurality of through-holes 111 extending in the longitudinal direction (i.e., the left-right direction in FIG. 1 ). In the example shown in FIG. 1 , the support 11 is substantially cylindrical. The cross section perpendicular to the longitudinal direction of each through-hole 111 (i.e., cell) is, for example, substantially circular. In FIG. 1 , the diameter of the through-hole 111 is drawn larger than in reality, and the number of through-holes 111 is drawn smaller than in reality. The separation membrane 12 is formed on the inner circumferential surface of the through-hole 111 and covers the inner circumferential surface of the through-hole 111 over substantially the entire surface.

[0020] The length of the support 11 (i.e., the length in the left-right direction in FIG. 1 ) is, for example, 10 cm to 200 cm (the symbol "to" means greater than or equal to the value before it and less than or equal to the value after it). The outer diameter of the support 11 is, for example, 0.5 cm to 30 cm. The distance between the central axes of adjacent through holes 111 is, for example, 0.3 mm to 10 mm. The surface roughness (Ra) of the support 11 is, for example, 0.1 μm to 5.0 μm, and preferably 0.2 μm to 2.0 μm. The shape of the support 11 may be, for example, a honeycomb shape, a flat plate shape, a tubular shape, a cylindrical shape, a columnar shape, or a polygonal pillar shape. When the shape of the support 11 is tubular or cylindrical, the thickness of the support 11 is, for example, 0.1 mm to 10 mm.

[0021] The support 11 is made of ceramic. Examples of ceramic sintered bodies selected as the material of the support 11 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, the support 11 contains at least one of alumina, silica, and mullite. The support 11 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.

[0022] The average pore diameter of the support 11 is, for example, 0.01 μm to 70 μm, preferably 0.05 μm to 25 μm. The average pore diameter of the support 11 near the surface where the separation membrane 12 is formed is 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. The average pore diameter can be measured, for example, by a mercury porosimeter, a perm porometer, or a nanoperm porometer. With regard to the pore size distribution throughout the support 11, including the surface and interior, D5 is, for example, 0.01 μm to 50 μm, D50 is, for example, 0.05 μm to 70 μm, and D95 ​​is, for example, 0.1 μm to 2000 μm. The porosity of the support 11 near the surface where the separation membrane 12 is formed is, for example, 20% to 60%. The porosity can be determined as the percentage of the area where voids exist in an SEM (scanning electron microscope) image of a cross section of the support 11.

[0023] The support 11 has, for example, a multilayer structure in which multiple layers with different average pore sizes are stacked in the thickness direction. The average pore size and sintered grain size in the surface layer, including the surface on which the separation membrane 12 is formed, are smaller than the average pore size and sintered grain size in the layers other than the surface layer. The average pore size in the surface layer of the support 11 is, for example, 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. When the support 11 has a multilayer structure, the materials described above can be used for each layer. The materials of the multiple layers forming the multilayer structure may be the same or different. Note that when the support 11 has a multilayer structure, the average pore size of the support 11 refers to the average pore size of the surface layer, including the surface on which the separation membrane 12 is formed.

[0024] The separation membrane 12 is a porous membrane having fine pores (micropores). The separation membrane 12 can separate a specific substance from a mixture of multiple substances by utilizing molecular sieving or the like. Other substances are less likely to permeate the separation membrane 12 than the specific substance. In other words, the permeation rate of the other substances through the separation membrane 12 is slower than the permeation rate of the specific substance.

[0025] The average thickness of the separation membrane 12 is, for example, 5 μm or less, preferably 2 μm or less. This enables a high permeation rate to be achieved. The lower limit of the average thickness of the separation membrane 12 is not particularly limited, but from the viewpoint of improving separation performance, it is preferably 0.5 μm, more preferably 0.7 μm. To measure the average thickness of the separation membrane 12, a cross section perpendicular to the surface of the separation membrane 12 is exposed, for example, by cross-sectional polishing. In the cross section, multiple randomly selected fields (e.g., seven fields) are observed using an SEM. The SEM magnification is, for example, 5000x. The average thickness of the separation membrane 12 in each field (field-average thickness) is calculated as the average of the thicknesses at five appropriately selected locations, and the arithmetic mean of the field-average thicknesses of the remaining fields, excluding the fields with the maximum and minimum field-average thickness values, is obtained as the average thickness of the separation membrane 12. The surface roughness (Ra) of the separation membrane 12 is, for example, 2 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less.

[0026] The MOF membrane in the separation membrane 12 is a polycrystalline membrane mainly composed of numerous MOF crystals (MOF crystal particles 121 in Figure 3) formed on the surface of the support 11. At the interface between the separation membrane 12 and the support 11, a composite layer 13 is formed in which the MOF crystals penetrate into the pores of the support 11. In Figure 2, the composite layer 13 is indicated by parallel diagonal lines superimposed on a portion of the support 11. The composite layer 13 is part of the support 11. The thickness of the composite layer 13 is, for example, 2 µm or less. This makes it possible to suppress a decrease in permeation rate due to the presence of the composite layer 13. The composite layer 13 does not have to be present, and the lower limit of the thickness of the composite layer 13 is 0.

[0027] In measuring the thickness of the composite layer 13, in cross-sectional observation using an SEM, the boundary position of the composite layer 13 in a direction perpendicular to the interface between the support 11 and the separation membrane 12 (hereinafter referred to as the "depth direction") is identified near one measurement position along the interface. Specifically, the boundary position on the separation membrane 12 side of the composite layer 13 is the interface between the separation membrane 12 and the support 11. The boundary position on the opposite side of the composite layer 13 from the separation membrane 12 is the edge of the MOF present in the pores of the support 11 that is farthest from the separation membrane 12 in the depth direction. The depth-wise distance between the boundary position on the separation membrane 12 side of the composite layer 13 and the boundary position on the opposite side of the separation membrane 12 is obtained as the thickness of the composite layer 13 at that measurement position. Then, the average of the thicknesses of the composite layer 13 at multiple different measurement positions (e.g., 10 measurement positions) is determined as the thickness of the composite layer 13 in the separation membrane composite 1.

[0028] Not only when the composite layer 13 is not present, but also when the composite layer 13 is present, there is no intermediate layer formed separately between the support 11 and the separation membrane 12 in the separation membrane composite 1, so the support 11 and the separation membrane 12 are in direct contact with each other. In other words, there is no intermediate layer formed between the support 11 and the separation membrane 12 in a step other than the step of forming the MOF membrane.

[0029] In the separation membrane 12, the pore diameter of the MOF constituting the MOF membrane (hereinafter also referred to as the "pore diameter of the MOF membrane") is, for example, 1 nm or less, preferably 0.40 nm or more and 0.90 nm or less. The "pore diameter of the MOF membrane" refers to the diameter of the pore in a direction approximately perpendicular to the maximum diameter (major axis) of the pore opening theoretically derived from the skeletal structure of the MOF (i.e., the minor axis). The minor axis of the pore opening may also be obtained by observation using a TEM (transmission electron microscope). The major and minor axes of the pore opening precisely refer to the interlattice spacing of the highly regular lattice structure formed by metal ions and organic ligands. MOFs have a unique pore structure consisting of channels (pores) and cages (internal spaces) depending on their structural type. The pore diameter here refers to the pore diameter of the channel, which is the diameter in a direction approximately perpendicular to the maximum diameter in the cross section of the channel. The pore size of the MOF membrane is smaller than the average pore size of the support 11 in the vicinity of the surface on which the separation membrane 12 is formed.

[0030] The MOF constituting the separation membrane 12 is composed of metal ions and organic ligands (hereinafter simply referred to as "ligands") coordinated to the metal ions. The metal ions constituting the MOF are not particularly limited, but in practical terms, Al ３＋ , Co ３＋ , Co ２＋ , Ni ２＋ , Ni ＋ , Cu ２＋ , Cu ＋ , Zn ２＋ , Fe ３＋ , Fe ２＋ , Ti ３＋ and Zr ４＋ More preferably, the metal ion comprises at least one selected from the group consisting of Al ３＋ , Zn ２＋ , Ti ３＋ and Zr ４＋ Preferably, the number of types of metal ions contained in the MOF is one, but may be multiple.

[0031] The ligands that are components of MOFs are not particularly limited, but one example is a bidentate ligand, which is an ion of an organic molecule having two carboxy groups. This makes it possible to easily form pores that allow a specific gas to pass through more easily than other specific gases. The structure other than the two carboxy groups is not particularly limited, but one suitable example is a ligand having a heterocycle. Furthermore, instead of a carboxy group, the ligand may have a ligand such as a pyridine group or a pyrrole group that can coordinate to a metal ion.

[0032] FIG. 3 is a schematic diagram showing MOF crystal particles 121 constituting the MOF membrane 120. The average particle size of the MOFs constituting the MOF membrane 120, i.e., the average particle size of the MOF crystal particles 121, is, for example, 0.1 μm to 2 μm. The average particle size is preferably 1 μm or less, and more preferably 0.5 μm or less. In an MOF membrane 120 with a small average particle size, grain boundary defects D1, described below, are reduced. In this embodiment, the average particle size of the MOF crystal particles 121 is the arithmetic mean of the maximum diameters of multiple MOF particles (e.g., 30 particles) measured by observing the membrane surface using a SEM. The multiple particles to be measured may be randomly selected on the SEM image.

[0033] In the separation membrane 12, amorphous particles 126 (indicated by black circles or clusters of black circles in FIG. 3 ) are supported in the regions between adjacent MOF crystal particles 121. In other words, the amorphous particles 126 are attached to and held by the MOF crystal particles 121 in the regions between the MOF crystal particles 121. In this way, the separation membrane 12 is an MOF membrane 120 that supports amorphous particles 126. For reasons that will be described later, the amorphous particles 126 are selectively (locally) present in grain boundary defects D1, which are excessively large gaps between the MOF crystal particles 121. A typical example of grain boundary defects D1 is a continuous space extending from the surface 120a of the MOF membrane 120 opposite the support 11 (the surface of the MOF membrane 120, hereinafter referred to as the "first surface 120a") to the surface on the support 11 side (the surface in contact with the support 11, hereinafter referred to as the "second surface"), forming a flow path with a diameter sufficiently larger than the pore size of the MOF membrane 120. Amorphous particles 126 block the grain boundary defects D1. Some of the amorphous particles 126 may be supported on the first surface 120a of the MOF membrane 120, or on the surface or in the pores of the support 11.

[0034] The amorphous particles 126 are made of an inorganic material, such as a metal oxide or a silicon oxide. Preferred amorphous particles 126 include particles of zirconia, titania, alumina, or silica. The amorphous particles 126 may be particles of a single material, or may include particles of multiple different materials. The amorphous particles 126 are almost gas-impermeable.

[0035] The amorphous microparticles 126 present in the regions between the MOF crystal particles 121 can be confirmed, for example, in an image (hereinafter referred to as a "TEM image") of a cross section of the separation membrane 12 perpendicular to the surface of the support 11 taken using a scanning transmission electron microscope (STEM). In the TEM image, regions without lattice fringes (interference fringes) are identified as amorphous microparticles 126, and regions with lattice fringes are identified as MOF crystal particles 121. Whether the microparticles supported on the MOF membrane 120 are amorphous may be confirmed by X-ray diffraction (XRD) or the like. The presence of the amorphous microparticles 126 can also be confirmed by elemental analysis (element mapping) using energy dispersive X-ray spectroscopy (EDS) or the like. The size (particle diameter) of the amorphous microparticles 126 varies.

[0036] Next, the production of the separation membrane composite 1 will be described with reference to FIG. 4 . When the separation membrane composite 1 is produced, seed crystals to be used in the production of the MOF membrane 120, which is the skeleton of the separation membrane 12, are first prepared (step S11). The seed crystals are produced as MOF powder by, for example, solvothermal synthesis using water and / or an organic solvent (also called hydrothermal synthesis when the solvent is water). The MOF powder may be produced by any or known production method. The MOF powder may be used as is as the seed crystal, or more preferable seed crystals may be obtained by processing the powder by pulverization or the like.

[0037] The average particle size (D50) of the seed crystals is preferably 0.5 μm or less. This makes it possible to suppress the occurrence of grain boundary defects in the MOF membrane 120, which would otherwise be caused by the average particle size of the MOFs becoming excessively large. There is no particular limitation on the lower limit of the average particle size of the seed crystals, but, for example, by setting the average particle size to 0.1 μm or more, it is possible to suppress a decrease in the crystallinity of the seed crystals. The average particle size (D50) of the seed crystals can be measured, for example, by a laser scattering method.

[0038] Next, the seed crystals are dispersed in a solvent (water and / or an organic solvent) to prepare a dispersion of, for example, 0.01 wt % to 1 wt %. A porous support 11 is immersed in the dispersion to attach the seed crystals to the support 11 (dip coating method) (step S12). Alternatively, the dispersion in which the seed crystals are dispersed in a solvent is brought into contact with the portion of the support 11 where the separation membrane 12 is to be formed, thereby attaching the seed crystals to the support 11. The solvent is then removed by drying to prepare a seed crystal-attached support. The seed crystals may also be attached to the support 11 by other methods.

[0039] Next, a raw material solution (also called a synthesis sol or synthesis solution) used to form the MOF membrane 120 is prepared (step S13). The preparation of the raw material solution may be performed before step S12 or in parallel with step S12. In preparing the raw material solution, a solvent (water and / or an organic solvent), a ligand, a metal ion source, and other raw materials are mixed. In one example, the ligand is added to the solvent and dissolved by ultrasonic treatment or heating in a thermostatic bath. Then, metal ions are added to obtain the raw material solution.

[0040] Once the raw material solution is prepared, the support 11 with seed crystals attached is immersed in the raw material solution. The raw material solution is then heated to initiate solvothermal synthesis, including hydrothermal synthesis (hereinafter collectively referred to as "solvothermal synthesis"). In solvothermal synthesis, MOFs grow using the seed crystals as nuclei, and an MOF membrane 120, which is the basic structure of the separation membrane 12, is formed on the support 11 (step S14). The synthesis temperature (heating temperature of the raw material solution) during solvothermal synthesis is, for example, 40 to 200°C, preferably 70 to 150°C. The solvothermal synthesis time is, for example, 1 to 100 hours, preferably 1 to 50 hours. Once the solvothermal synthesis is complete, the support 11 and the MOF membrane 120 are washed with pure water and then with ethanol or the like. Preferably, washing with water and ethanol or the like is repeated multiple times. Through the above process, the support 11 on which the MOF membrane 120 is formed is prepared.

[0041] Next, the washed support 11 and MOF membrane 120 are placed in a dryer and dried (step S15). In this processing example, "drying" refers to removing moisture (water molecules) from the first and second surfaces of the MOF membrane 120 and from the pores. The drying temperature for the MOF membrane 120 is, for example, 50 to 100°C, and the drying time is, for example, 0.5 to 72 hours. If the support 11 and MOF membrane 120 are left in the air after the drying process until the next step S16, water molecules in the air will be adsorbed into the pores of the MOF membrane 120. Therefore, it is preferable to perform the drying process again immediately before step S16.

[0042] After the drying process, the MOF membrane 120 is contacted with a repair solution, thereby supporting the amorphous microparticles 126 on the MOF membrane 120 (step S16). Specifically, a repair solution containing a repair material and an organic solvent is first prepared. The repair material is a substance that reacts with water to precipitate inorganic amorphous microparticles 126. Examples of repair materials that can be used include metal alkoxides such as titanium tetraisopropoxide, aluminum isopropoxide, and zirconium (IV) isopropoxide, and silane coupling agents such as tetraethoxysilane. Typically, the kinetic molecular diameter of the repair material is larger than the pore diameter of the MOF membrane 120. This prevents the precipitation of the amorphous microparticles 126 in the pores of the MOF membrane 120. The organic solvent is ethanol, methanol, acetone, isopropanol, toluene, or the like. It is preferable that the kinetic molecular diameter of the organic solvent be smaller than the pore diameter of the MOF membrane 120. The concentration of the repair material in the solution obtained by dissolving the repair material in the organic solvent is, for example, 0.001 to 1 mol / L, and preferably 0.05 to 0.5 mol / L. The repair solution does not contain water.

[0043] 5 is a diagram showing the state in which the repair solution 53 is brought into contact with the MOF membrane 120. For example, as shown in FIG. 5, the support 11 is arranged so that the through-holes 111 are parallel to the direction of gravity, and silicone tubes 51, 52 are connected to the upper and lower end surfaces of the support 11. The tube 52 has a bottom. When the tubes 51, 52 are filled with the repair solution 53, the inner circumferential surfaces of the through-holes 111 of the support 11 come into contact with the repair solution 53. In other words, the repair solution 53 comes into contact with the first surface 120a (see FIG. 3) of the MOF membrane 120, and the first surface 120a becomes wet with the repair solution 53.

[0044] FIG. 6 shows an MOF membrane 120 in contact with a repair solution 53. Similar to FIG. 3 , FIG. 6 also shows a schematic representation of MOF crystal particles 121. The area filled with the repair solution 53 is hatched with dashed lines. As shown in FIG. 6 , the repair solution 53 penetrates into the grain boundary defects D1 from the first surface 120a of the MOF membrane 120. At the grain boundary defects D1 that penetrate the MOF membrane 120, the repair solution 53 seeps out onto the second surface (support 11 side) of the MOF membrane 120. The second surface is in contact with the atmosphere (air) that has entered through the pores of the support 11. The repair material contained in the repair solution 53 that seeps out from the grain boundary defects D1 onto the second surface reacts with water in the atmosphere, causing hydrolysis and condensation polymerization. As a result, amorphous particles 126 precipitate at the grain boundary defects D1, and the grain boundary defects D1 are blocked by the amorphous particles 126. In other words, the amorphous particles 126 are selectively supported on the grain boundary defects D1 of the MOF film 120, thereby repairing the grain boundary defects D1.

[0045] As described above, the kinetic molecular diameter of the repair material is larger than the pore diameter of the MOF membrane 120, thereby preventing the precipitation of amorphous microparticles 126 in the pores of the MOF membrane 120. Furthermore, in the repair solution 53 of this processing example, the kinetic molecular diameter of the organic solvent is smaller than the pore diameter of the MOF membrane 120. Therefore, the organic solvent contained in the repair solution 53 is continuously present from the first surface 120a of the MOF membrane 120 to the pores, thereby preventing water from the atmosphere from reaching the openings of the pores in the first surface 120a. As a result, the precipitation of amorphous microparticles 126 and the blockage of the pores are prevented. The temperature of the repair solution 53 in the processing (repair processing) of step S16 is, for example, 0 to 60°C, preferably 40°C or less. The temperature of the repair solution 53 may be room temperature. The repair processing time is, for example, 0.5 to 72 hours, preferably 0.5 to 24 hours. In FIG. 5, the tubes 51 and 52 may be one tube that covers the entire outer circumferential surface of the support 11 .

[0046] After the repair process is completed, the repair solution 53 in the tubes 51 and 52 is removed, and then the tubes 51 and 52 are filled with an organic solvent. This brings the organic solvent into contact with the first surface 120a of the MOF membrane 120 (see FIG. 6 ), and any unreacted repair material remaining in the MOF membrane 120 dissolves in the organic solvent (step S17). In other words, the MOF membrane 120 is washed to remove the unreacted repair material from the MOF membrane 120. It is preferable that the organic solvent in the tubes 51 and 52 is replaced multiple times (i.e., the MOF membrane 120 is washed multiple times).

[0047] The MOF membrane 120 is then dried, and becomes the final separation membrane 12. In the separation membrane 12, amorphous fine particles 126 of an inorganic material are present in the regions between the MOF crystal particles 121 (mainly at grain boundary defects D1). A small amount of amorphous fine particles 126 may be present in the pores of the support 11. By the above-mentioned processes, a separation membrane composite 1 is obtained.

[0048] In the example of FIG. 5 , the repair solution 53 is supplied to the inner circumferential surface of the through-hole 111. However, for example, the repair solution 53 may be supplied to the outer circumferential surface of the support 11 while sealing both ends of each through-hole 111 in the longitudinal direction. In this case, the repair solution 53 that has entered the pores of the support 11 contacts the second surface of the MOF membrane 120, and the first surface 120a contacts the air on the inner circumferential surface side of the through-hole 111. This causes amorphous microparticles 126 to precipitate approximately locally at the grain boundary defects D1. In this way, the repair solution 53 only needs to contact the MOF membrane 120 from one direction. Furthermore, a water-containing gas other than air or a water-containing liquid (which may be water) may contact the surface of the MOF membrane 120 opposite to the surface that contacts the repair solution 53.

[0049] Here, the repair process of the comparative example will be described. In the repair process of the comparative example, similar to JP 2018-167150 A (the above-mentioned document 1), a solution containing an organic material is supplied to the space on one side of the MOF membrane, and the space on the other side is depressurized. As a result, as shown in FIG. 7, the organic material is filled into the grain boundaries 93 of the MOF membrane 91. On the other hand, in the repair process of the comparative example, the entire surface (or a wide area) of the MOF membrane 91 is covered with a membrane 92 of organic material, which significantly reduces permeation performance. Furthermore, because the membrane 92 itself is gas permeable, separation performance is not significantly improved.

[0050] In contrast, the manufacturing method of the separation membrane composite 1 shown in FIG. 4 involves contacting one side of the MOF membrane 120 with a repair solution 53 containing a repair material and an organic solvent, and contacting the other side with a gas or liquid containing water. This facilitates the production of a separation membrane 12 without a membrane covering the entire MOF membrane, as in the comparative example, and in which inorganic amorphous particles 126 fill the regions between the MOF crystal particles 121 (mainly grain boundary defects D1). In a separation membrane composite 1 having such a separation membrane 12, the blockage of grain boundary defects D1 by the amorphous particles 126 improves separation performance. This repair process is particularly suitable for thin separation membranes 12 with an average thickness of 2 μm or less, where grain boundary defects D1 are likely to occur. Drying the MOF membrane 120 before the repair process can prevent the precipitation of many amorphous particles 126 on the surface of the MOF membrane 120, thereby suppressing (mitigating) a decrease in permeation performance.

[0051] Preferably, after the repair treatment, the repair material remaining on the MOF membrane 120 is removed by bringing an organic solvent into contact with the one surface of the MOF membrane 120. This makes it possible to prevent unnecessary amorphous fine particles from precipitating on the MOF membrane 120.

[0052] Preferably, in the repair process, the repair solution 53 contacts the surface of the MOF membrane 120 opposite to the support 11 (the first surface 120a in the above example), which is opposite to the support 11. This makes it possible to prevent unnecessary amorphous fine particles from being deposited in the pores of the support 11.

[0053] In a preferred separation membrane composite 1, amorphous microparticles 126 are formed by contacting one surface of the MOF membrane 120 with a repair solution 53 containing a repair material and an organic solvent having a kinetic molecular diameter smaller than the pore size of the MOF membrane 120. This makes it possible to prevent the pores of the MOF membrane 120 from being blocked by the amorphous microparticles 126 on the one surface, thereby maintaining high permeability. Note that because the pores of the MOF membrane 120 are extremely small, it is difficult to confirm whether each pore is blocked by the amorphous microparticles 126, and there are circumstances that make it impossible or impractical to directly identify the separation membrane composite 1 described above by its structure or characteristics.

[0054] However, the repair material (e.g., metal alkoxide) contained in the repair solution tends to adhere to zeolite membranes. When repairing a zeolite membrane using this repair material solution, a large amount of the repair material adheres to the surface of the zeolite membrane. Therefore, in JP 2002-263457 A (reference 2), the repair material is supplied to the zeolite membrane in gaseous form. Meanwhile, the present inventors have discovered that, as previously described, dissolving the repair material in an organic solvent with a kinetic molecular diameter smaller than the pore size of the MOF membrane 120 can suppress the deposition of amorphous microparticles 126 on the surface of the MOF membrane 120 (blockage of pores by the amorphous microparticles 126). In the above-described processing example, these characteristics are utilized to bring the repair solution into contact with the surface of the MOF membrane 120, causing the amorphous microparticles 126 to deposit approximately only on the grain boundary defects D1, thereby repairing the grain boundary defects D1.

[0055] Next, separation of a mixed substance using the separation membrane composite 1 will be described with reference to Figures 8 and 9. Figure 8 is a diagram showing the separation device 2. Figure 9 is a diagram showing the flow of separation of a mixed substance by the separation device 2.

[0056] In the separation device 2, a mixed substance containing multiple types of fluids (i.e., gases or liquids) 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 from the mixed substance, or for the purpose of concentrating less permeable substances.

[0057] 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.

[0058] The mixture may include, for example, hydrogen (H ２ ), helium (He), nitrogen (N ２ ), oxygen (O ２ ), water (H ２ O), carbon monoxide (CO), carbon dioxide (CO ２ ), nitrogen oxides, ammonia (NH ３ ), sulfur oxides, hydrogen sulfide (H ２ S), sulfur fluoride, mercury (Hg), arsine (AsH ３ ), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1-C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes.

[0059] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO ２ ), nitrous oxide (also called dinitrogen monoxide) (N ２ O), dinitrogen trioxide (N ２ O ３ ), dinitrogen tetroxide (N ２ O ４ ), dinitrogen pentoxide (N ２ O ５ ) etc. Ｘ It is a gas called NOX.

[0060] Sulfur oxides are compounds of sulfur and oxygen. Examples of the sulfur oxides include sulfur dioxide (SO ２ ), sulfur trioxide (SO３ ) and other SOs Ｘ It is a gas called SOX.

[0061] Sulfur fluoride is a compound of fluorine and sulfur. The above-mentioned sulfur fluoride is, for example, disulfur difluoride (FS-SF, S=SF ２ ), sulfur difluoride (SF ２ ), sulfur tetrafluoride (SF ４ ), sulfur hexafluoride (SF ６ ) or disulfur decafluoride (S ２ F １０ ) etc.

[0062] C1-C8 hydrocarbons are hydrocarbons with one or more carbon atoms and eight or less. C3-C8 hydrocarbons may be straight-chain compounds, branched-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be either saturated hydrocarbons (i.e., those without double and triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double and / or triple bonds in the molecule). C1-C4 hydrocarbons include, for example, methane (CH ４ ), ethane (C ２ H ６ ), ethylene (C ２ H ４ ), propane (C ３ H ８ ), propylene (C ３ H ６ ), normal butane (CH ３ (CH ２ ) ２ CH ３ ), isobutane (CH(CH ３ ) ３ ), 1-butene (CH ２ =CHCH ２ CH ３ ), 2-butene (CH ３ CH=CHCH ３ ) or isobutene (CH ２ =C(CH ３ ) ２ )

[0063] The organic acid is a carboxylic acid or a sulfonic acid. The carboxylic acid is, for example, formic acid (CH ２O ２ ), acetic acid (C ２ H ４ O ２ ), oxalic acid (C ２ H ２ O ４ ), acrylic acid (C ３ H ４ O ２ ) or benzoic acid (C ６ H ５ COOH), etc. Sulfonic acids include, for example, ethanesulfonic acid (C ２ H ６ O ３ S) and the like. The organic acid may be a chain compound or a cyclic compound.

[0064] The alcohols mentioned above include, for example, methanol (CH ３ OH), ethanol (C ２ H ５ OH), isopropanol (2-propanol) (CH ３ CH(OH)CH ３ ), ethylene glycol (CH ２ (OH)CH ２ (OH)) or butanol (C ４ H ９ OH) and the like.

[0065] Mercaptans are organic compounds with hydrogenated sulfur (SH) at the end, and are also called thiols or thioalcohols. Examples of the above-mentioned mercaptans include methyl mercaptan (CH ３ SH), ethyl mercaptan (C ２ H ５ SH) or 1-propanethiol (C ３ H ７ SH), etc.

[0066] The esters mentioned above are, for example, formates or acetates.

[0067] The above-mentioned ethers include, for example, dimethyl ether ((CH ３ ) ２ O), methyl ethyl ether (C ２ H ５ OCH ３) or diethyl ether ((C ２ H ５ ) ２ O) etc.

[0068] The above-mentioned ketones can be, for example, acetone ((CH ３ ) ２ CO), methyl ethyl ketone (C ２ H ５ COCH ３ ) or diethyl ketone ((C ２ H ５ ) ２ CO), etc.

[0069] The aldehydes mentioned above include, for example, acetaldehyde (CH ３ CHO), propionaldehyde (C ２ H ５ CHO) or butanal (butyraldehyde) (C ３ H ７ CHO) etc.

[0070] 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.

[0071] The separation device 2 includes a separation membrane composite 1, a sealing unit 21, a housing 22, two seal members 23, a supply unit 26, a first recovery unit 27, and a second recovery unit 28. The separation membrane composite 1, the sealing unit 21, and the seal members 23 are housed within the housing 22. The supply unit 26, the first recovery unit 27, and the second recovery unit 28 are disposed outside the housing 22 and connected to the housing 22.

[0072] The sealing portion 21 is attached to both longitudinal end portions of the support 11 (i.e., the left-right direction in FIG. 8 ) and is a member that covers and seals both longitudinal end faces of the support 11 and the outer peripheral surfaces near these end faces. The sealing portion 21 prevents gas from flowing in and out from these end faces of the support 11. The sealing portion 21 is, for example, a plate-like member formed of glass or resin. The material and shape of the sealing portion 21 may be changed as appropriate. Note that the sealing portion 21 has multiple openings that overlap with the multiple through holes 111 of the support 11, and therefore both longitudinal ends of each through hole 111 of the support 11 are not covered by the sealing portion 21. Therefore, gas and the like can flow in and out of the through holes 111 from these ends.

[0073] The shape of the housing 22 is not limited, but may be, for example, a substantially cylindrical tubular member. The housing 22 is formed, for example, from 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. 8 ), and a first discharge port 222 is provided at the other end. A second discharge port 223 is provided on the side of the housing 22. A supply unit 26 is connected to the supply port 221. A first collection unit 27 is connected to the first discharge port 222. A second collection unit 28 is connected to the second discharge port 223. The internal space of the housing 22 is an enclosed space isolated from the space surrounding the housing 22.

[0074] The two seal members 23 are disposed around the entire circumference between the outer peripheral surface of the separation membrane composite 1 and the inner peripheral surface of the housing 22 near both longitudinal ends of the separation membrane composite 1. Each seal member 23 is a substantially annular member made of a gas-impermeable material. The seal members 23 are, for example, O-rings made of a flexible resin. The seal members 23 are in close contact with the outer peripheral surface of the separation membrane composite 1 and the inner peripheral surface of the housing 22 around the entire circumference. In the example shown in FIG. 8 , the seal member 23 is in close contact with the outer peripheral surface of the sealing portion 21 and indirectly in close contact with the outer peripheral surface of the separation membrane composite 1 via the sealing portion 21. A seal is formed between the seal member 23 and the outer peripheral surface of the separation membrane composite 1, and between the seal member 23 and the inner peripheral surface of the housing 22, so that gas hardly or completely passes through.

[0075] Supply unit 26 supplies the mixed gas to the internal space of housing 22 via supply port 221. Supply unit 26 is, for example, a blower or a pump that pressure-feeds the mixed gas toward housing 22. The blower or pump includes a pressure adjustment unit that adjusts the pressure of the mixed gas supplied to housing 22. First recovery unit 27 and second recovery unit 28 are, for example, storage containers that store the gas drawn out from housing 22, or blowers or pumps that transport the gas.

[0076] When separating a mixed gas, the separation device 2 is prepared, thereby preparing the separation membrane composite 1 (step S21). Next, a mixed gas containing multiple types of gases with different permeabilities through the separation membrane 12 is supplied by the supply unit 26 to the internal space of the housing 22. For example, the main components of the mixed gas are CO ２ and N ２ The mixed gas contains CO ２ and N ２ The pressure of the mixed gas supplied from the supply unit 26 to the internal space of the housing 22 (i.e., the introduction pressure) is, for example, 0.1 MPa to 20.0 MPa. The temperature at which the mixed gas is separated is, for example, 10°C to 150°C.

[0077] The mixed gas supplied from the supply unit 26 to the housing 22 is introduced into each of the through-holes 111 of the support 11 from the left end of the separation membrane composite 1 in the drawing, as indicated by arrow 251. A gas with high permeability in the mixed gas (for example, CO ２ The highly permeable substance (hereinafter referred to as "highly permeable substance") passes through the separation membrane 12 provided on the inner circumferential surface of each through-hole 111 and the support 11, and is discharged from the outer circumferential surface of the support 11. As a result, the highly permeable substance is able to separate the low permeable gas (e.g., N ２ (hereinafter referred to as "low-permeability material") is separated from the low-permeability material (step S22). The gas (hereinafter referred to as "permeation material") discharged from the outer peripheral surface of the support 11 is recovered by the second recovery unit 28 via the second discharge port 223, as shown by arrow 253. The pressure of the gas recovered by the second recovery unit 28 via the second discharge port 223 (i.e., permeation pressure) is, for example, about 1 atmosphere (0.101 MPa).

[0078] Furthermore, gases (hereinafter referred to as "impermeable substances") excluding the gas that has permeated the separation membrane 12 and the support 11 of the mixed gas pass through each through-hole 111 of the support 11 from left to right in the figure, and are recovered by the first recovery unit 27 via the first discharge port 222, as shown by arrow 252. The pressure of the gas recovered by the first recovery unit 27 via the first discharge port 222 is, for example, approximately the same as the introduction pressure. In addition to the above-mentioned low-permeable substances, the impermeable substances may also include highly permeable substances that did not permeate the separation membrane 12.

[0079] In order to use the separation membrane composite 1 for gas separation, the permeation rate of the highly permeable substance is preferably at least five times the permeation rate of the low-permeable substance. The permeation rate (permeance) is the gas permeation rate per unit membrane area and unit pressure difference. In the case of the separation membrane composite 1 having the separation membrane 12 supporting the amorphous fine particles 126, at least CO ２ It is suitable for the separation of CO, a highly permeable material. ２ and the target gas to be separated (i.e., a low permeability material, e.g., N ２ ) is preferably 5 or more. In particular, as will be apparent from the examples described later, when the target gas is N２ If CO ２ Permeation rate and N ２ The ratio of the CO ２ / N ２ The permeation rate ratio (hereinafter referred to as the "permeation rate ratio") is preferably 10 or more, and more preferably 30 or more.

[0080] When comparing the separation membrane composite 1 before supporting the amorphous fine particles 126 and the separation membrane composite 1 after supporting the amorphous fine particles 126, the CO ２ The permeation rate is the CO permeation rate of the separation membrane composite before loading. ２ The CO permeation rate in the separation membrane composite 1 after loading is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. ２ / N ２ The permeation rate ratio is the ratio of the CO ２ / N ２ The ratio is preferably 2 times or more, more preferably 5 times or more, and even more preferably 10 times or more of the permeation rate ratio.

[0081] Next, examples and comparative examples of the separation membrane composite will be described. Table 1 shows the manufacturing conditions and measurement results of the examples and comparative examples.

[0082]

[0083] First, we describe the preparation of seed crystals for four types of MOFs, called "Al Fumarate," "KMF-1," "UiO-66-NH2," and "CALF-20." Each example and comparative example used one of the four types of seed crystals.

[0084] <Preparation of Al Fumarate Seed Crystals> First, 0.28 g of fumaric acid and 0.34 g of sodium formate, which serve as ligands, were added to 50 mL of deionized water to prepare a mixed solution. The mixed solution was stirred at 50°C for 3 hours, then cooled to room temperature, and 0.83 g of aluminum sulfate 18-hydrate was added as a metal ion source. Next, this solution was subjected to solvothermal synthesis at 120°C for 12 hours. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. As a result, Al Fumarate seed crystals were obtained.

[0085] <Preparation of KMF-1 seed crystals> First, 1.551 g of 1H-pyrrole-2,5-dicarboxylic acid (ligand) and 1.36 g of sodium formate were added to 50 mL of deionized water to prepare a mixed solution. The mixed solution was stirred at 50°C for 3 hours, then cooled to room temperature, and 3.333 g of aluminum sulfate 18-hydrate (metal ion source) was added. Next, this solution was subjected to solvothermal synthesis at 120°C for 12 hours. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. In this way, KMF-1 seed crystals were obtained.

[0086] <Preparation of UiO-66-NH2 seed crystals> First, 0.233 g of zirconium chloride (metal ion source) and 0.166 g of 2-aminoterephthalic acid (ligand) were added to a mixed solvent of 3 mL of acetic acid and 30 mL of dimethylformamide (DMF) to prepare a mixed solution. The mixed solution was sonicated at room temperature for 30 minutes to obtain a homogeneous solution. Next, this solution was subjected to solvothermal synthesis at 120°C for 24 hours. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. This yielded UiO-66-NH2 seed crystals.

[0087] <Preparation of CALF-20 seed crystals> First, 0.646 g of zinc oxalate dihydrate, the metal ion source, and 0.957 g of 1,2,4-triazole, the ligand, were added to 11.36 mL of water and 17 mL of methanol solution, respectively. The resulting mixture was sonicated at room temperature for 30 minutes to obtain a homogeneous solution. Next, this solution was subjected to solvothermal synthesis at 180°C for 24 hours. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. This yielded CALF-20 seed crystals.

[0088] <Pulverization of seed crystals> 1 g of each type of seed crystal was placed in a glass vial containing zirconia balls, and 9 g of water was added. The glass vial was set on a ball mill stand, and the seed crystals were pulverized at 60 rpm for 5 to 24 hours to obtain seed crystals with an average particle size of 0.20 to 0.50 μm.

[0089] Example 1 (Supporting of Seed Crystals) Al fumarate seed crystals were supported on a ceramic support.

[0090] (MOF membrane production) First, 0.39 g of fumaric acid and 0.45 g of sodium formate, which are ligands, were added to 150 mL of deionized water to prepare a mixed solution. The mixed solution was heated to 40 ° C. and stirred for 1 hour. After confirming that the mixed solution was transparent, it was cooled to room temperature, and 1.10 g of aluminum sulfate 18-hydrate, which is a metal ion source, was added to prepare a raw material solution. Next, the raw material solution and the support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was performed at 100 ° C. for 20 hours. This resulted in a separation membrane composite in which an Al Fumarate MOF membrane was formed on the support. This separation membrane composite was washed three times with deionized water and ethanol. The separation membrane composite was then left in the atmosphere for 12 hours or more and dried.

[0091] (Drying Treatment) The separation membrane structure was placed in a dryer and dried at 60° C. for 1 hour.

[0092] (Repair Treatment) Titanium tetraisopropoxide, a repair material, was added to 30 mL of ethanol, an organic solvent, and stirred with a stirrer for 1 minute to prepare a 0.1 mol / L repair solution. A silicone tube was connected to the separation membrane composite (see Figure 5), and the repair solution was allowed to come into contact with only the MOF membrane surface for 24 hours (this can be considered an immersion treatment of the MOF membrane in the repair solution). The membrane surface was then washed three times with ethanol alone and dried at 100°C for 12 hours to obtain a separation membrane composite with a repaired MOF membrane.

[0093] (Confirmation of amorphous fine particles) By cross-sectional observation using a STEM (scanning transmission electron microscope), it was confirmed that amorphous fine particles were precipitated in the regions between MOF crystal particles (grain boundaries or defects). The same applies to the following examples.

[0094] (Measurement of average film thickness) Seven fields of view of the longitudinal cross section of the MOF membrane were randomly observed using an SEM (scanning electron microscope). As already explained, the average film thickness of the MOF membrane in each field of view (field-average film thickness) was determined, and the arithmetic mean of the field-average film thicknesses of five fields of view excluding the fields with the maximum and minimum field-average film thickness values ​​was taken as the average film thickness of the MOF membrane. The measurement results of the average film thickness are shown in the "MOF film thickness" column in Table 1. The same applies to the following examples and comparative examples.

[0095] (CO ２ Permeation rate and CO ２ / N ２ Measurement of transmission rate ratio) CO ２ and N ２ The permeation rate of CO ２ 50% by volume, N ２ The measurement was performed by introducing a mixed gas with a composition of 50% by volume of CO at 25°C and a pressure of 0.3 MPa onto the surface of the separation membrane. ２ / N ２ The permeation rate ratio is ２ The permeation rate is N ２ The CO was obtained by dividing by the permeation rate. ２ / N ２ Permeation rate ratio and CO ２ The measurement results of the permeation rate are shown in Table 1 under "CO ２ / N ２ Permeation Rate Ratio" and "CO ２The same applies to the following examples and comparative examples.

[0096] Example 2 The same procedure as in Example 1 was carried out except that the organic solvent contained in the repair solution was changed to methanol.

[0097] Example 3 The same procedure as in Example 1 was carried out except that the organic solvent contained in the repair solution was changed to acetone.

[0098] Example 4 The same procedure as in Example 1 was carried out except that the time for which the repair solution was brought into contact with the surface of the MOF membrane in the repair treatment was changed to 2 hours.

[0099] Example 5 The same procedure as in Example 1 was carried out except that the temperature in the drying treatment was changed to 100°C.

[0100] Example 6 The same procedure as in Example 1 was carried out except that the repair material contained in the repair solution was changed to aluminum isopropoxide.

[0101] Example 7 The same procedure as in Example 1 was carried out except that the repair material contained in the repair solution was changed to zirconium (IV) isopropoxide and the organic solvent was changed to isopropanol.

[0102] Example 8 The same procedure as in Example 1 was carried out except that the repair material contained in the repair solution was changed to tetraethoxysilane.

[0103] Example 9 (Supporting of Seed Crystals) Seed crystals of KMF-1 were supported on a ceramic support.

[0104] (MOF membrane production) The KMF-1 raw material solution was prepared using the same process as for preparing the seed crystals. Next, the raw material solution and the ceramic support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 100°C for 20 hours. This resulted in a separation membrane composite in which a KMF-1 MOF membrane was formed on the support. This separation membrane composite was washed three times with deionized water and ethanol. The separation membrane composite was then left to dry in the atmosphere for 12 hours or more. The drying and repair processes were the same as in Example 1.

[0105] Example 10 (Supporting of Seed Crystals) Seed crystals of UiO-66-NH2 were supported on a ceramic support.

[0106] (MOF membrane production) The raw material solution of UiO-66-NH2 was prepared using the same process as for seed crystal preparation. Next, the raw material solution and the ceramic support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 100°C for 20 hours. This resulted in a separation membrane composite in which a UiO-66-NH2 MOF membrane was formed on the support. This separation membrane composite was washed three times with deionized water and ethanol. The separation membrane composite was then left to dry in the air for at least 12 hours. The drying and repair processes were the same as in Example 1.

[0107] Example 11 (Supporting of Seed Crystals) CALF-20 seed crystals were supported on a ceramic support.

[0108] (MOF membrane production) The CALF-20 raw material solution was prepared using the same process as for seed crystal preparation. Next, the raw material solution and the ceramic support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 100°C for 20 hours. This resulted in a separation membrane composite in which a CALF-20 MOF membrane was formed on the support. This separation membrane composite was washed three times with deionized water and ethanol. The separation membrane composite was then left to dry in the air for 12 hours or more. The drying and repair processes were the same as in Example 1.

[0109] Example 12 The same procedure as in Example 1 was carried out except that the organic solvent contained in the repair solution was changed to toluene.

[0110] Comparative Example 1 An Al Fumarate MOF membrane was prepared in the same manner as in Example 1, and no repair treatment was carried out.

[0111] Here, when Examples 1 to 8 and 12 in which the same type (Al Fumarate) MOF membranes were prepared were compared with Comparative Example 1, it was found that Examples 1 to 8 and 12 had a lower CO ２ / N ２ The permeation rate ratio was significantly increased. ２ CO permeation rate of Examples 1 to 8 and 12２ The decrease in permeation rate was 10% or less. Therefore, it is believed that in the separation membrane composites of Examples 1 to 8 and 12, the grain boundary defects between the MOF crystal particles are blocked with amorphous fine particles, thereby suppressing the decrease in permeation performance and improving separation performance.

[0112] Next, in Example 12, CO ２ The decrease in the permeation rate (CO ２ The reason why the decrease in the permeation rate (amount of decrease relative to the permeation rate) was larger than in Examples 1 to 8 will be considered. The major and minor axes of the pores of Al Fumarate are 6.0 Å and 5.8 Å, respectively. The kinetic molecular diameters of the organic solvents of the repair solutions used in Examples 1 to 8, i.e., ethanol, methanol, acetone, and isopropanol, are all smaller than the pore diameter (minor axis) of Al Fumarate. In contrast, the kinetic molecular diameter of toluene used in Example 12 is 5.8 Å, the same as the pore diameter of Al Fumarate. Therefore, in the repair treatment of Example 12, the organic solvent does not penetrate much into the pores from the surface of the MOF membrane (first surface 120a in the example of Figure 6), and water in the atmosphere reaches the surface of the MOF membrane through the pores, facilitating the deposition of amorphous fine particles on the surface. As a result, in the separation membrane composite of Example 12, some of the pores of the MOF membrane are blocked by amorphous fine particles, and CO ２ In other words, in Examples 1 to 8, in which an organic solvent having a smaller kinetic molecular diameter than the pore size of the MOF membrane was used, the pores of the MOF membrane could be prevented from being blocked by amorphous fine particles, and the CO ２ This makes it possible to more reliably reduce the decrease in permeation rate (for example, to 5% or less).

[0113] For the separation membrane composites of Examples 9 to 11, which used different types of MOF membranes, no comparative examples were prepared that were not subjected to repair treatment. However, similar to Examples 1 to 8 and 12, amorphous fine particles were precipitated in the regions between the MOF crystalline particles, and therefore it is believed that similar effects can be obtained.

[0114] The separation membrane composite 1 and the method for manufacturing the separation membrane composite 1 can be modified in various ways.

[0115] In the production of the separation membrane composite 1, the type of MOF in the seed crystals and the type of MOF in the MOF membrane do not have to be the same. Furthermore, the raw material solution may contain two or more types of ligands. The separation membrane composite 1 may also be produced by a method other than the above-described production method.

[0116] In the separation device 2, substances other than those exemplified in the above description may be separated from the mixed substance.

[0117] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0118] 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.

[0119] The separation membrane composite of the present invention can be used in a variety of fields for separating various substances.

[0120] 1 Separation membrane composite 11 Support 12 Separation membrane 53 Repair solution 120 MOF membrane 120a (MOF membrane) surface 121 Crystalline particle 126 Amorphous fine particle S11 to S17, S21, S22 Steps

Claims

1. A separation membrane composite comprising: a porous support; and a separation membrane that is a film of a metal-organic framework provided on the support, the separation membrane carrying amorphous fine particles of an inorganic material in regions between crystalline particles of the metal-organic framework.

2. A separation membrane composite according to claim 1, wherein the amorphous fine particles comprise fine particles of zirconia, titania, alumina or silica.

3. The separation membrane composite according to claim 1, wherein the metal ions constituting the metal organic framework are Al ３＋ , Co ３＋ , Co ２＋ , Ni ２＋ , Ni ＋ , Cu ２＋ , Cu ＋ , Zn ２＋ , Fe ３＋ , Fe ２＋ , Ti ３＋ and Zr ４＋ A separation membrane complex comprising at least one selected from the group consisting of:

4. A separation membrane composite according to claim 1, wherein the average thickness of the separation membrane is 2 μm or less.

5. A separation membrane composite according to any one of claims 1 to 4, in which the amorphous microparticles are formed by contacting one side of the membrane of the metal-organic framework provided on the support with a repair solution containing a repair material that reacts with water to precipitate the amorphous microparticles and an organic solvent having a kinetic molecular diameter smaller than the pore diameter of the membrane of the metal-organic framework, and contacting the other side with a gas or liquid containing water.

6. A method for producing a separation membrane composite, comprising: a) preparing a porous support having a metal-organic framework membrane provided thereon; b) drying the metal-organic framework membrane; and c) contacting one surface of the metal-organic framework membrane with a repair solution containing an organic solvent and a repair material that reacts with water to precipitate amorphous fine particles of an inorganic material, and contacting the other surface of the metal-organic framework membrane with a gas or liquid containing water.

7. The method for producing a separation membrane composite according to claim 6, wherein in step c), the repair solution comes into contact with the surface of the membrane of the metal-organic framework opposite to the support.

8. A method for producing a separation membrane composite according to claim 6, further comprising, after step c), a step of contacting the one surface of the membrane of the metal-organic framework with an organic solvent to remove the repair material remaining on the membrane.

9. A method for producing a separation membrane composite according to any one of claims 6 to 8, wherein the organic solvent contained in the repair solution has a kinetic molecular diameter smaller than the pore diameter of the membrane of the metal-organic framework.

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