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 membrane of a metal organic structure provided on the support (11), has an average pore diameter of 0.40 nm-0.90 nm inclusive, and has an amine supported on a surface and in pores in the vicinity of the surface. When the separation membrane (12) is prepared, the amine is supported in the membrane by bringing a solution containing the amine into contact with the surface of the membrane of the metal organic structure.

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 JP2023-132688, filed on August 16, 2023, 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 There is a growing need for technologies to separate and recover carbon dioxide. The use of mesoporous silica membranes has been proposed as one carbon dioxide separation technology. For example, in Japanese Patent Laid-Open Publication No. 2007-44677 (Reference 1), a precursor solution is applied to a porous support impregnated with liquid paraffin to form a thin gel film. The liquid paraffin and the surfactant in the thin gel film are then removed by calcination to obtain a mesoporous silica membrane. Subsequently, basic functional groups are introduced into the mesoporous silica membrane by refluxing with a silane coupling agent having basic functional groups.

[0003] In WO 2022 / 209002 (Document 2), a porous support is provided with an intermediate membrane made of zeolite having a small average pore size, and a separation membrane made of mesoporous silica is further provided on the intermediate membrane. Functional groups such as amino groups are introduced into the pores in the surface layer of the separation membrane.

[0004] Meanwhile, metal-organic frameworks (MOFs) are porous materials with high surface areas. Similar to zeolite and mesoporous silica membranes, MOFs are expected to be used for gas and liquid separations when fabricated on porous supports. Nanyi Wang et al., "Amine-modified Mg-MOF-74 / CPO-27-Mg membrane with enhanced H2 / CO2 separation," Chemical Engineering Science, 124 (2015) 27-36 (Reference 3), propose a technique for using MOFs to separate specific gases. In Reference 3, an Mg-MOF-74 membrane is formed on a support and then refluxed at 110°C in a solution of ethylenediamine dissolved in toluene, resulting in a separation membrane loaded with ethylenediamine.

[0005] In Literature 1, a mesoporous silica membrane is chemically reacted with a silane coupling agent having a basic functional group by refluxing. Also in Literature 3, ethylenediamine is introduced into the MOF membrane by refluxing. Therefore, in the separation membranes of Literature 1 and Literature 3, a large amount of amine permeates the entire membrane, resulting in a decrease in the target gas permeability.

[0006] Furthermore, in the method of Reference 1, it is necessary to perform reflux treatment by heating toluene in which aminopropyltriethoxysilane is dissolved to 150°C under an argon gas atmosphere, which makes it difficult to treat large membranes. ２ However, the structure is complex and it is not easy to reduce the manufacturing cost. In addition, the average pore size of the mesoporous silica membrane is 1 nm or more, and the amine is chemically bonded to the mesoporous silica membrane. The separation membrane in Reference 3 has an average pore size of 1 nm or more in the MOF, and is excellent in CO separation performance. ２ than nitrogen (N ２ ) penetrates through the ２ and N ２ Furthermore, it is thought that the presence of amines within the support increases the permeation resistance.

[0007] An object of the present invention is to provide a separation membrane composite that exhibits high separation performance for specific gases while suppressing a decrease in fluid permeability, and a method for producing the same.

[0008] A first aspect of the present 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 having an average pore diameter of 0.40 nm or more and 0.90 nm or less, and having an amine supported on a surface and in the pores near the surface.

[0009] According to aspect 1 of the present invention, it is possible to provide a separation membrane composite that exhibits high separation performance for a specific gas while suppressing a decrease in fluid permeability.

[0010] A second aspect of the present invention is the separation membrane composite of the first 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＋ , Fe ３＋ , Fe ２＋ , Ti ３＋ and Zr ４＋ At least one selected from the group consisting of:

[0011] A third aspect of the present invention is the separation membrane composite of the first aspect (which may be either the first or second aspect), wherein the organic ligand that is a component of the metal-organic framework is a bidentate ligand that is an ion of an organic molecule having two carboxy groups.

[0012] A fourth aspect of the present invention is the separation membrane composite of the first aspect (which may be any one of the first to third aspects), in which the amine comprises one or more kinds of linear amines.

[0013] A fifth aspect of the present invention is the separation membrane composite of the first aspect (which may be any one of the first to fourth aspects), wherein the average pore diameter is 0.40 nm or more and 0.70 nm or less.

[0014] A sixth aspect of the present invention is a separation membrane composite according to the first aspect (which may be any one of the first to fifth aspects),２ and the CO ２ The ratio of the permeation rate of the target gas to the permeation rate of the target gas to be separated is 5 or more.

[0015] A seventh aspect of the present invention is the separation membrane composite of the first aspect (which may be any one of the first to sixth aspects), wherein the average thickness of the separation membrane is 0.5 μm or more and 2 μm or less.

[0016] Aspect 8 of the present invention is the separation membrane composite according to any one of aspects 1 to 7, wherein the amount of the amine present per unit volume gradually decreases from the surface of the separation membrane toward the support.

[0017] A ninth aspect of the present invention is a method for producing a separation membrane composite, comprising: a) a step of attaching seed crystals of a metal-organic framework onto a porous support; b) a step of preparing a raw material solution of the metal-organic framework; c) a step of immersing the support in the raw material solution and forming a film of the metal-organic framework having an average pore diameter of 0.40 nm or more and 0.90 nm or less on the support by solvothermal synthesis; and d) a step of contacting a solution containing an amine with a surface of the film of the metal-organic framework.

[0018] According to the ninth aspect of the present invention, it is possible to provide a method for producing a separation membrane composite that has high separation performance for a specific gas while suppressing a decrease in fluid permeability.

[0019] A tenth aspect of the present invention is the method for producing the separation membrane composite of Aspect 9, further comprising, between the step c) and the step d), the step e) of drying the film of the metal-organic framework, and the step f) of maintaining the film of the metal-organic framework in a high-humidity environment.

[0020] 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.

[0021] 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 the flow of manufacturing a separation membrane composite; Fig. 4 is a diagram showing the state of an amine supporting treatment; Fig. 5 is a diagram showing a separation device; Fig. 6 is a diagram showing the flow of separation of mixed substances by a separation device.

[0022] 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 provided 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") on which an amine is supported, and the separation membrane composite 1 is a MOF membrane composite. An MOF membrane is at least a membrane in which an MOF is 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 parallel diagonal lines. Also, in FIG. 2, the thickness of the separation membrane 12 is depicted thicker than it actually is.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The average thickness of the separation membrane 12 is 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, and more preferably 0.5 μm or less.

[0030] The average pore diameter of the MOF membrane constituting the separation membrane 12 is 0.40 nm or more and 0.90 nm or less. The "average pore diameter of the MOF" is the average value of the long and short diameters of the pore openings theoretically derived from the skeletal structure of the MOF. Alternatively, the long and short diameters of the pore openings may be obtained by observation using a TEM (transmission electron microscope) to determine the average pore diameter. More precisely, the long and short diameters of the pore openings refer to the interlattice spacing of a highly regular lattice structure formed by metal ions and organic ligands. MOFs have unique pore structures consisting of channels (pores) and cages (internal spaces) depending on their structural type. Here, the pore diameter refers to the pore diameter of the channel, with the maximum diameter in the cross section of the channel being the long diameter and the diameter of the cross section in a direction approximately perpendicular to the long diameter being the short diameter, and the arithmetic mean of the short diameter and the long diameter being the average pore diameter. The average pore size 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.

[0031] The average particle size of the MOFs constituting the separation membrane 12, i.e., the average size of the crystal grains, 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 a separation membrane 12 having a small average MOF particle size, grain boundary defects caused by excessively large gaps formed between MOF crystals are reduced, making it possible to improve separation performance. The average particle size of the MOF in this embodiment is the arithmetic mean of the maximum diameters of multiple MOF particles (e.g., 30 particles) measured by observing the membrane surface using an SEM. The multiple particles to be measured may be randomly selected on an SEM image.

[0032] At the interface between the separation membrane 12 and the support 11, a composite layer 13 is formed in which crystals of the MOF penetrate into the pores of the support 11. In FIG. 2 , the composite layer 13 is shown by drawing parallel diagonal lines over 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 necessarily have to be present, and the lower limit of the thickness of the composite layer 13 is 0.

[0033] 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.

[0034] 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.

[0035] 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. In practical terms, the metal ions constituting the MOF are preferably 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 is 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.

[0036] The ligand, which is a component of the MOF, is preferably 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 another specific gas. The structure other than the two carboxy groups is not particularly limited, but one suitable example is a ligand having a heterocycle. Furthermore, the ligand may have, instead of a carboxy group, a ligand such as a pyridine group or a pyrrole group that can coordinate to a metal ion.

[0037] The separation membrane 12 is composed of MOFs on which an amine is supported. That is, the separation membrane 12 is a MOF membrane on which an amine is supported. "Amine supported" means that amine molecules are present in contact with the skeleton of the MOF, and that the amine is attached to the MOF with such a force that the amine is not easily released from the skeleton of the MOF when the gas to be permeated through the separation membrane 12 permeates through the MOF. This state may also be expressed as "amine introduced into the MOF membrane" or "MOF membrane modified with an amine." The amine is supported at least on the surface of the MOF membrane and in the pores near the surface.

[0038] Preferably, the amount of amine present gradually decreases from the surface of the MOF membrane (the surface opposite the support 11) toward the support 11. "Gradually decreasing" describes the overall appearance and excludes minute increases and decreases when viewed microscopically. As described below, the amine is preferably a linear amine. The linear amine supported on the MOF is not limited to one type, and may be one or more types of linear amine. Preferably, no amine is present on the support 11 (including cases where a small amount is unintentionally present), and more preferably, no amine is present near the support 11 in the MOF membrane (including cases where a small amount is unintentionally present).

[0039] Next, with reference to FIG. 3 , the flow of manufacturing the separation membrane composite 1 will be described. When manufacturing the separation membrane composite 1, first, seed crystals to be used in manufacturing the MOF membrane, which is the skeleton of the separation membrane 12, are prepared (step S11). The seed crystals are produced as MOF powder, for example, by 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 manufacturing method. The MOF powder may be used as is as the seed crystals, or more preferable seed crystals may be obtained by processing the powder by pulverization or the like.

[0040] 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, 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.

[0041] Next, the seed crystals are dispersed in a solvent (water and / or an organic solvent) to prepare a 0.01 wt % to 1 wt % dispersion. 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.

[0042] Next, a raw material solution (also called a synthesis sol or synthesis solution) used to form the MOF membrane 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. Specifically, 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 a raw material solution.

[0043] Once the raw material solution is prepared, the support 11 to which the seed crystals are 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 the solvothermal synthesis, MOFs with an average pore diameter of 0.40 nm or more and 0.90 nm or less grow using the seed crystals as nuclei, and a dense MOF membrane, which is the basic structure of the separation membrane 12, is formed on the support 11 (step S14). The synthesis temperature during the solvothermal synthesis (the heating temperature of the raw material solution) 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.

[0044] After the solvothermal synthesis is completed, the support 11 and the MOF membrane are washed with pure water, and then washed with ethanol or the like. Preferably, washing with water and ethanol or the like is repeated multiple times. After washing, the support 11 and the MOF membrane are dried, for example, at 100°C (step S15). "Drying" refers to removing molecules of the substances used for washing, such as water and ethanol, from the pores of the MOF membrane.

[0045] Next, a humidification treatment is performed to maintain the MOF membrane in a high-humidity environment (step S16). "Maintaining" the MOF membrane in a high-humidity environment means placing the MOF membrane in a high-humidity environment (atmosphere). "High humidity" refers to a humidity higher than the relatively dry environment in which experiments are conducted, and does not refer to the high humidity of a natural environment. In a high-humidity environment, the gas surrounding the MOF membrane may or may not flow. The humidification treatment essentially brings water vapor into contact with the MOF membrane. While the humidification treatment is not essential, it is believed that the amount of amine supported on the MOF membrane gradually decreases from the surface of the MOF membrane toward the support 11 in the subsequent amine support treatment, thereby preventing excessive amine support on the MOF membrane. This achieves both high gas separation performance and high gas permeation rate.

[0046] In the humidification treatment, the MOF membrane is kept in an environment at a temperature of 10°C or higher and 80°C or lower, preferably 20°C or higher and 50°C or lower (close to room temperature), with a humidity of 30% or higher (preferably 40% or higher) and 100% or lower, for 0.5 hours or longer, preferably 1 hour or longer, and more preferably 3 hours or longer (preferably 10 hours or shorter).

[0047] Next, an amine-containing solution is brought into contact with the surface of the MOF membrane, thereby supporting the amine on the MOF membrane (step S17). That is, the amine is present on the surface of the MOF membrane and in the pores of the MOF membrane. Specifically, the amine-containing solution is brought into contact only with the surface of the MOF membrane opposite the support 11, thereby supporting the amine on the surface of the MOF membrane and inside the MOF membrane near the surface. The amine concentration of the solution obtained by dissolving the amine in an organic solvent is 0.001 mol / L or more and 1 mol / L or less. More preferably, the amine concentration is 0.05 mol / L or more and 0.5 mol / L or less. "Contacting" the amine-containing solution with the surface of the MOF membrane refers to the presence of the solution on the surface. It is preferable that the amine-containing solution be present on the surface for a certain period of time or more, and "contacting" refers to wetting the surface with the amine-containing solution when viewed locally.

[0048] The amine impregnation treatment is carried out in a mild environment of 10°C to 60°C. Preferably, the amine impregnation treatment is carried out at 20°C to 40°C. More preferably, the amine impregnation treatment is carried out at room temperature. This allows for safer treatment compared to the dangerous prior art in which an organic solvent is used to impregnate a zeolite membrane or a mesoporous silica membrane with an amine at high temperatures. The duration of the amine impregnation treatment is preferably 1 hour to 72 hours, more preferably 5 hours to 30 hours.

[0049] Specifically, as shown in FIG. 4 , the support 11 is positioned so that the through-holes 111 are parallel to the direction of gravity, and silicone tubes 51 and 52 are connected to the upper and lower end faces of the support 11. The tubes 51 and 52 have bottoms. The tubes 51 and 52 are filled with an amine-containing solution 53, so that the inner surfaces of the through-holes 111 in the support 11 come into contact with the solution. As a result, only one surface of the MOF membrane 12a (the surface opposite the support 11) comes into contact with the solution, and the amine is introduced into the surface of that surface of the MOF membrane 12a and the interior thereof in the vicinity thereof. The tubes 51 and 52 may be a single tube that covers the entire outer peripheral surface of the support 11.

[0050] Thereafter, the MOF membrane 12a is dried, and the MOF membrane 12a becomes the final separation membrane 12. In the separation membrane 12, amines are present on its surface and inside near the surface. More preferably, the density of amines in the MOF membrane gradually decreases from the surface toward the support 11. Preferably, no amines are present on the support 11 (including unintentional slight presence), and more preferably, no amines are present near the support 11 in the MOF membrane either (including unintentional slight presence). By the above-mentioned processes, a separation membrane composite 1 is obtained.

[0051] The amine in the amine loading treatment, i.e., the amine source in the solution, is preferably a linear amine. "Linear" means that the carbon atoms making up the hydrocarbon or its derivative are bonded in a single chain without forming a cyclic or branched structure. The linear amine preferably has 1 to 6 amino groups, and the number of nitrogen atoms and carbon atoms connected in a linear chain is preferably 2 to 30. The use of a linear amine is thought to facilitate entry of the amine into the pores of the MOF membrane 12a. Furthermore, the use of a linear amine is thought to suppress clogging of the pores of the MOF, resulting in high gas permeability.

[0052] The presence of amines in the separation membrane 12 can be confirmed, for example, by TOF-SIMS-depth (TOF-SIMS stands for "Time-of-Flight Secondary Ion Mass Spectrometry"). By measuring the N element (nitrogen element), the amount of amine supported, i.e., the amount of amine present per unit volume, can be measured. In TOF-SIMS-depth, the concentration of N element is measured in the depth direction from the surface of the separation membrane 12. As a result of the measurement, it has been confirmed that the concentration of N element gradually decreases from the surface toward the support 11 in the separation membrane 12. That is, the amount of amine present per unit volume gradually decreases from the surface of the separation membrane 12 toward the support 11. The concentration of N element in the immediate vicinity of the surface of the separation membrane 12 may be ignored due to the influence of contamination.

[0053] In the separation membrane composite 1, the amine is not chemically bonded to the MOF membrane. Therefore, if the amine deteriorates, it is possible to remove the amine from the MOF membrane with a solvent and then load a new amine onto the membrane.

[0054] Next, separation of a mixed substance using the separation membrane composite 1 will be described with reference to Figures 5 and 6. Figure 5 is a diagram showing the separation device 2. Figure 6 is a diagram showing the flow of separation of a mixed substance by the separation device 2.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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 )

[0062] 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.

[0063] 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.

[0064] 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.

[0065] The esters mentioned above are, for example, formates or acetates.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] The sealing portion 21 is attached to both longitudinal end portions of the support 11 (i.e., the left-right direction in FIG. 5 ) 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.

[0072] 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. 5 ), and a first discharge port 222 is provided at the other end. A second discharge port 223 is provided on the side of the 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.

[0073] 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. 5 , 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.

[0074] 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.

[0075] 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.

[0076] 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).

[0077] 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.

[0078] 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 carrying an amine, 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 permeation rate to the permeation rate is preferably 10 or more, and more preferably 30 or more.

[0079] 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.

[0080]

[0081] First, the production of the four types of seed crystals used in the Examples and Comparative Examples will be described. In each Example and Comparative Example, one of the four types of seed crystals was used.

[0082] <Preparation of Al Fumarate Seed Crystals> The MOF known as "Al Fumarate" is known from Qiwei Liua and five others, "Fast synthesis of Al fumarate metal-organic framework as a novel tetraethylenepentamine support for efficient CO2 capture," Colloids and Surfaces A, 579 (2019) 123645. First, a mixed solution was prepared by adding 0.28 g of fumaric acid and 0.34 g of sodium formate (ligands) to 50 mL of deionized water. The mixed solution was stirred at 50 °C for 3 hours, cooled to room temperature, and 0.83 g of aluminum sulfate 18-hydrate was added as a metal ion source. This solution was then 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. This yielded MOF powder as Al Fumarate seed crystals.

[0083] <Preparation of KMF-1 Seed Crystals> The MOF called "KMF-1" is known from Kyung Ho Cho et al., "Rational design of a robust aluminum metal-organic framework for multi-purpose water-sorption-driven heat allocations," NATURE COMMUNICATIONS, (2020) 11:5112, (https: / / doi.org / 10.1038 / s41467-020-18968-7). First, a mixed solution was prepared by adding 1.551 g of 1H-pyrrole-2,5-dicarboxylic acid (ligand) and 1.36 g of sodium formate to 50 mL of deionized water. The mixed solution was stirred at 50 °C for 3 hours, 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 by centrifugation and washed three times with deionized water and ethanol, yielding MOF powder as seed crystals for KMF-1.

[0084] <Preparation of MIL-125-NH2(Ti) seed crystals> The MOF of "MIL-125-NH2(Ti)" was developed by Liang Zhang and nine other researchers, who are working on "NH2-MIL-53(Al) Metal-Organic Framework as the Smart Platform for Simultaneous High-Performance Detection and Removal of Hg" 2+", Inorganic Chemistry 2019 58 (19), 12573-12581 (https: / / doi.org / 10.1021 / acs.inorgchem.9b01242). First, 2.0 mL of titanium tetraisopropoxide (metal ion source) and 1.36 g of 2-aminoterephthalic acid (ligand) were added to a mixed solvent of 9 mL of dimethylformamide (DMF) and 1 mL of dry methanol to prepare a mixed solution. The mixed solution was stirred at room temperature for 1 hour. Next, this solution was subjected to solvothermal synthesis at 150 °C for 72 hours. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. From the above, MOF powder was obtained as a seed crystal for MIL-125-NH2(Ti).

[0085] <Preparation of UiO-66-NH2(Zr) Seed Crystals> The UiO-66-NH2(Zr) MOF is also disclosed in the above-mentioned literature (Liang Zhang and nine others). 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 DMF to prepare a mixed solution. The mixed solution was sonicated at room temperature for 30 minutes. 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 MOF powder as UiO-66-NH2(Zr) seed crystals.

[0086] <Preparation of CAU-10-H Seed Crystals> The CAU-10-H MOF is known from VB Lopez-Cervantes and five others, "CO2 Adsorption under Humid Conditions: Self-Regulated Water Content in CAU-10," Polyhedron 155 (2018) 163-169. First, 1.666 g of aluminum sulfate hexahydrate (metal ion source) and 0.415 g of trimesic acid (ligand) were added to a mixed solvent of 36 mL of DMF and 144 mL of water to prepare a mixed solution. The mixed solution was sonicated at room temperature for 30 minutes. Next, this solution was subjected to solvothermal synthesis at 135°C for 24 hours. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. This yielded MOF powder as CAU-10-H seed crystals.

[0087] Example 1 (Supporting of Seed Crystals) 1 g of Al Fumarate seed crystals was dispersed in 10 mL of ethanol as a dispersion medium and pulverized in a ball mill for 24 hours to obtain a dispersion of seed crystals with an average particle size (D50) of 250 nm. Ethanol was then added so that the concentration of the dispersion became 0.01%. A porous alumina support was immersed in the dispersion to adhere the dispersion to the support, and the solvent was evaporated in a dryer to support the seed crystals on the support surface. The support used had an average pore size of approximately 100 nm.

[0088] (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 to confirm that the mixed solution became transparent. After that, 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 to obtain a MOF membrane composite in which a MOF membrane was formed on the support. This MOF membrane composite was washed three times with deionized water and ethanol. Then, the MOF membrane composite was dried in the air for 12 hours or more, and then dried at 100 ° C. for 12 hours.

[0089] (Humidification Treatment) The MOF membrane composite was placed in a thermo-hygroscopic dryer and subjected to humidification treatment at a temperature of 25°C and a relative humidity of 50% for 72 hours.

[0090] (Amine loading treatment) Tetraethylenepentamine (TEPA) was added as an amine source to 30 mL of ethanol and stirred for 10 minutes to prepare a 0.1 mol / L amine-containing ethanol solution. A silicone tube was connected to the MOF composite (see Figure 4), and the amine-containing ethanol solution was allowed to contact only the membrane surface of the MOF for 24 hours. The membrane surface was then washed three times with ethanol alone and dried at 100°C for 12 hours to load the amine onto the MOF membrane. This yielded a separation membrane composite.

[0091] (Film Thickness Measurement Results) The longitudinal cross section of the MOF membrane was observed at seven randomly selected visual fields using a SEM (scanning electron microscope), and as already described, the average film thickness of the MOF membrane in each visual field image (visual field average film thickness) was determined. The arithmetic mean of the visual field average film thicknesses of five visual fields excluding the visual fields with the maximum and minimum visual field average film thickness values ​​was taken as the average film thickness of the MOF membrane. The same applies to the following Examples and Comparative Examples.

[0092] The average thickness of the MOF membrane in Example 1 was measured by the above-mentioned method and found to be 1.8 μm.

[0093] (CO ２ / N ２ Measurement results of permeation rate ratio) Amine is CO ２ The separation membrane carrying the amine has the property of adsorbing CO ２ It is suitable for separating CO ２ / N ２ Permeation rate ratio (N ２ CO ２ The ratio of the CO permeation rate to the CO permeation rate was measured. ２ and N ２ The CO permeation rate was measured by introducing the gas to be measured onto the surface of the separation membrane at 100°C and a pressure of 0.3 MPa. ２ permeation rate and N ２ From the permeation rate of CO ２ / N ２ The same applies to the following Examples and Comparative Examples.

[0094] CO in Example 1 ２ / N ２ The permeation rate ratio was measured by the above-mentioned method and was found to be 55.

[0095] Example 2 The treatment conditions in Example 2 were the same as those in Example 1, except that the humidification treatment was performed at a temperature of 50°C and a relative humidity of 20% for 0.5 hours. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 50.

[0096] Example 3 The treatment conditions in Example 3 were the same as those in Example 1, except that the humidification treatment was carried out at a temperature of 30°C and a relative humidity of 90% for 24 hours. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 55.

[0097] Example 4 The treatment conditions in Example 4 were the same as those in Example 1, except that the MOF membrane composite was brought into contact with an amine-containing ethanol solution for 2 hours during the amine loading treatment. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 40.

[0098] Example 5 The treatment conditions in Example 5 were the same as those in Example 1, except that the MOF membrane composite was contacted with an amine-containing ethanol solution for 72 hours in the amine loading treatment. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 60.

[0099] Example 6 The treatment conditions in Example 6 were the same as those in Example 1, except that ethylenediamine was used as the amine source in the amine-carrying treatment. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 40.

[0100] Example 7 The treatment conditions in Example 7 were the same as those in Example 1, except that 2-(2-aminoethylamino)ethanol was used as the amine source in the amine-carrying treatment. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 60.

[0101] Example 8 The treatment conditions in Example 8 were the same as those in Example 1, except that diethylenetriamine was used as the amine source in the amine-carrying treatment. Therefore, the average thickness of the MOF membrane was the same as that in Example 1. ２ / N ２ The permeation rate ratio was 40.

[0102] Example 9 The treatment conditions in Example 9 were the same as those in Example 1, except that the solvothermal synthesis conditions for the MOF membrane were 100°C for 10 hours and the humidification treatment conditions were a temperature of 30°C and a relative humidity of 80% for 12 hours. The average thickness of the MOF membrane was 1.0 μm. ２ / N ２ The permeation rate ratio was 55.

[0103] Example 10 A MOF membrane was prepared in the same manner as in Example 1, and an amine-supporting treatment was carried out in the same manner as in Example 1. No humidification treatment was carried out. Therefore, the average thickness of the MOF membrane was the same as in Example 1. ２ / N ２ The permeation rate ratio was 15.

[0104] Example 11 (Supporting of seed crystals) A support supporting seed crystals was obtained in the same manner as in Example 1, except that KMF-1 was used as the seed crystals.

[0105] (MOF membrane production) The KMF-1 raw material solution was prepared using the same process as for seed crystal preparation. Next, the raw material solution and the 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. The obtained MOF membrane composite was washed three times with deionized water and ethanol. The MOF membrane composite was then left to dry in the air for 12 hours or more, and then dried at 100°C for 12 hours.

[0106] (Humidification Treatment) The humidification treatment was the same as in Example 1.

[0107] (Amine Supporting Treatment) The amine supporting treatment was carried out in the same manner as in Example 1.

[0108] (Results of Membrane Thickness Measurement) The average membrane thickness of the MOF membrane determined in the same manner as in Example 1 was 1.2 μm.

[0109] (CO ２ / N ２ Measurement results of the transmission rate ratio) CO ２ / N ２ The permeation rate ratio was 25.

[0110] Example 12 The amine loading treatment in Example 12 was the same as in Example 11, except that 2-(2-aminoethylamino)ethanol was used as the amine source. Therefore, the average thickness of the MOF membrane was the same as in Example 11. ２ / N ２ The permeation rate ratio was 30.

[0111] Example 13 (Supporting of seed crystals) A support supporting seed crystals was obtained in the same manner as in Example 1, except that MIL-125-NH2(Ti) was used as the seed crystals and water was used as the dispersion medium.

[0112] (MOF membrane production) The raw material solution of MIL-125-NH2(Ti) was prepared using the same process as for preparing the seed crystals. Next, the raw material solution and the support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 150°C for 10 hours. The obtained MOF membrane composite was washed three times with deionized water and ethanol. The MOF membrane composite was then left to dry in the air for 12 hours or more, and then dried at 100°C for 12 hours.

[0113] (Humidification Treatment) The humidification treatment was the same as in Example 1.

[0114] (Amine Supporting Treatment) The amine supporting treatment was carried out in the same manner as in Example 1.

[0115] (Results of Membrane Thickness Measurement) The average membrane thickness of the MOF membrane determined in the same manner as in Example 1 was 2.0 μm.

[0116] (CO２ / N ２ Measurement results of the transmission rate ratio) CO ２ / N ２ The permeation rate ratio was 10.

[0117] Example 14 (Supporting of seed crystals) A support supporting seed crystals was obtained in the same manner as in Example 1, except that UiO-66-NH2(Zr) was used as the seed crystals and water was used as the dispersion medium.

[0118] (MOF membrane production) The raw material solution of UiO-66-NH2(Zr) was prepared using the same process as for preparing the seed crystals. Next, the raw material solution and the support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 120°C for 20 hours. The resulting MOF membrane composite was washed three times with deionized water and ethanol. The MOF membrane composite was then left to dry in the air for at least 12 hours, and then dried at 100°C for 12 hours.

[0119] (Humidification Treatment) The humidification treatment was the same as in Example 1.

[0120] (Amine Supporting Treatment) The amine supporting treatment was carried out in the same manner as in Example 1.

[0121] (Results of Membrane Thickness Measurement) The average membrane thickness of the MOF membrane determined in the same manner as in Example 1 was 2.0 μm.

[0122] (CO ２ / N ２ Measurement results of the transmission rate ratio) CO ２ / N ２ The permeation rate ratio was 16.

[0123] Example 15 (Supporting of seed crystals) A support supporting seed crystals was obtained in the same manner as in Example 1, except that CAU-10-H was used as the seed crystals and water was used as the dispersion medium.

[0124] (MOF membrane production) The raw material solution of CAU-10-H was prepared using the same process as for preparing the seed crystals. Next, the raw material solution and the support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 135°C for 20 hours. The obtained MOF membrane composite was washed three times with deionized water and ethanol. The MOF membrane composite was then left to dry in the air for 12 hours or more, and then dried at 100°C for 12 hours.

[0125] (Humidification Treatment) The humidification treatment was the same as in Example 1.

[0126] (Amine Supporting Treatment) The amine supporting treatment was carried out in the same manner as in Example 1.

[0127] (Measurement Results of Membrane Thickness) The average membrane thickness of the MOF membrane determined in the same manner as in Example 1 was 1.0 μm.

[0128] (CO ２ / N ２ Measurement results of the transmission rate ratio) CO ２ / N ２ The permeation rate ratio was 30.

[0129] Example 16 The procedure was the same as in Example 1 except for the method of supporting the amine. Therefore, the average thickness of the MOF membrane was the same as in Example 1.

[0130] (Amine loading treatment) Tetraethylenepentamine (TEPA) was added as an amine source to 200 mL of ethanol and stirred for 10 minutes to prepare a 0.1 mol / L amine-containing ethanol solution. The entire separation membrane on which the MOF membrane was formed was immersed in the amine-containing ethanol solution for 24 hours. The entire separation membrane was then washed three times with ethanol alone and dried at 100 ° C. for 12 hours to load the amine onto the MOF membrane. This resulted in a separation membrane composite.

[0131] (CO ２ / N ２ Measurement results of the transmission rate ratio) CO ２ / N ２ The permeation rate ratio was 10.

[0132] Comparative Example 1 A MOF membrane was prepared in the same manner as in Example 1, but neither the humidification treatment nor the amine-supporting treatment was performed. Therefore, the average thickness of the MOF membrane was the same as in Example 1. ２ / N ２ The permeation rate ratio was 3.

[0133] Comparative Example 2: Seed crystals of Mg-MOF-74 were obtained with reference to the aforementioned literature 3 (Nanyi Wang and four others). Specifically, magnesium nitrate hexahydrate (0.2375 g, 0.925 mmol) and 2,5-dihydroxyterephthalic acid (0.1011 g, 0.509 mmol) were added to a mixed solvent of DMF, water, and ethanol in a volume ratio of 15:1:1 to prepare a mixed solution. This solution was then 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. As a result, MOF powder was obtained as seed crystals of Mg-MOF-74.

[0134] (Supporting of seed crystals) A support supporting seed crystals was obtained in the same manner as in Example 1, except that Mg-MOF-74 seed crystals were used as the seed crystals and water was used as the dispersion medium.

[0135] (MOF membrane production) The raw material solution of Mg-MOF-7 was prepared using the same process as for preparing the seed crystals. Next, the raw material solution and the support carrying the seed crystals were placed in a Teflon (registered trademark) container, and solvothermal synthesis was carried out at 120°C for 20 hours. The obtained MOF membrane composite was washed three times with deionized water and ethanol. The MOF membrane composite was then left to dry in the air for at least 12 hours, and then dried at 100°C for 12 hours.

[0136] (Humidification Treatment) The humidification treatment was the same as in Example 1.

[0137] (Amine Supporting Treatment) The amine supporting treatment was carried out in the same manner as in Example 1.

[0138] (Results of Membrane Thickness Measurement) The average membrane thickness of the MOF membrane determined in the same manner as in Example 1 was 5.0 μm.

[0139] (CO ２ / N ２ Measurement results of the transmission rate ratio) CO２ / N ２ The permeation rate ratio was 0.5.

[0140] In the above examples, the average pore diameter of Al Fumarate is 0.59 nm. The average pore diameter of KMF-1 is 0.60 nm. The average pore diameter of MIL-125-NH2(Ti) is 0.60 nm. The average pore diameter of UiO-66-NH2(Zr) is 0.60 nm. The average pore diameter of CAU-10-H is 0.40 nm. On the other hand, the average pore diameter of Mg-MOF-74 in the comparative example is 1.10 nm. From the above examples, it can be seen that by supporting amine on a MOF membrane with an average pore diameter of around 0.60 nm, that is, 0.40 nm or more and 0.70 nm or less, high CO ２ / N ２ The types of gases to be separated by the separation membrane composite 1 are CO ２ The amine-supported MOF membrane is not limited to the above, and can also be used for separating other gases. From the above examples, it can be said that an amine-supported MOF membrane suitable for separating specific fluids can be obtained if the average pore size is 0.90 nm or less, which is close to the average value of 0.60 nm and 1.10 nm. In practical use, the average pore size of the MOF membrane is 0.40 nm or more.

[0141] In addition, by supporting the amine on the surface of the MOF membrane (i.e., the surface of the separation membrane 12) and in the pores near the surface, the separation membrane 12 has high separation performance for specific gases while suppressing a decrease in fluid permeability. In particular, this effect is thought to be effectively achieved by the gradual decrease in the amount of amine present per unit volume from the surface of the separation membrane 12 toward the support 11.

[0142] From the above examples, separation membrane composite 1 can be used to ２ / N ２ It can be seen that a high transmission rate ratio is achieved. ２ / N ２ The permeation rate ratio is 30 or more.

[0143] The separation membrane composite 1 and the method for manufacturing the separation membrane composite 1 can be modified in various ways.

[0144] 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.

[0145] In the separation device 2, substances other than those exemplified in the above description may be separated from the mixed substance.

[0146] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0147] 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.

[0148] The separation membrane composite of the present invention can be used in a variety of fields for separating various substances.

[0149] 1 Separation membrane composite 11 Support 12 Separation membrane 12a MOF membrane Steps S11 to S17

Claims

1. A separation membrane composite comprising: a porous support; and a metal-organic framework membrane provided on the support, the metal-organic framework membrane having an average pore diameter of 0.40 nm or more and 0.90 nm or less, and an amine supported on a surface and in pores in the vicinity of the surface.

2. The separation membrane composite according to claim 1, wherein the metal ion that is a component of the metal-organic framework is Al ３＋ , Co ３＋ , Co ２＋ , Ni ２＋ , Ni ＋ , Cu ２＋ , Cu ＋ , Zn ２＋ , Fe ３＋ , Fe ２＋ , Ti ３＋ and Zr ４＋ The separation membrane complex is at least one selected from the group consisting of:

3. A separation membrane composite according to claim 1, wherein the organic ligand, which is a component of the metal-organic framework, is a bidentate ligand that is an ion of an organic molecule having two carboxy groups.

4. The separation membrane composite according to claim 1, wherein the amine comprises one or more linear amines.

5. A separation membrane composite according to claim 1, wherein the average pore diameter is 0.40 nm or more and 0.70 nm or less.

6. The separation membrane composite according to claim 1, ２ and the CO ２ The separation membrane composite has a ratio of the permeation rate of the target gas to the permeation rate of the target gas to be separated of 5 or more.

7. A separation membrane composite according to claim 1, wherein the average thickness of the separation membrane is 0.5 μm or more and 2 μm or less.

8. A separation membrane composite according to any one of claims 1 to 7, wherein the amount of said amine present per unit volume gradually decreases from the surface of said separation membrane toward said support.

9. A method for producing a separation membrane composite, comprising: a) attaching seed crystals of a metal-organic framework onto a porous support; b) preparing a raw material solution of the metal-organic framework; c) immersing the support in the raw material solution and forming a film of the metal-organic framework having an average pore diameter of 0.40 nm or more and 0.90 nm or less on the support by solvothermal synthesis; and d) contacting a solution containing an amine with a surface of the film of the metal-organic framework.

10. A method for producing a separation membrane composite according to claim 9, further comprising, between the steps c) and d), the steps e) of drying the film of the metal-organic framework, and f) of maintaining the film of the metal-organic framework in a high humidity environment.

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