Separation method and separation device

Abstract

This separation method for separating CO2 from a gas mixture comprises: a step for preparing a separation membrane composite in which a separation membrane composed of a metal-organic framework is disposed on a porous support; a step for adjusting the temperature of the gas mixture to within a restricted temperature range (W1) determined according to the concentration of moisture contained in the gas mixture; and a step for supplying the separation membrane composite with the gas mixture after the temperature adjustment and permeating the gas mixture through the separation membrane, thereby separating CO2 from the gas mixture. The restricted temperature range (W1) has a temperature width of 30°C in the range of 50-120°C, and in the restricted temperature range (W1), the fluctuation width of the permeation rate of CO2 contained in the gas mixture through the separation membrane composite is 20% or less. This makes it possible to easily achieve stable CO2 permeation performance in the separation membrane.

Description

Separation method and separation device

[0001] The present invention is directed to the production of CO from a mixed gas. ２ [Reference to Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2024-16268, filed February 6, 2024, and International Patent Application PCT / JP2024 / 39659, filed November 7, 2024, the entire disclosures of which are incorporated herein by reference.

[0002] Metal-organic framework (MOF) membranes for gas separation have been developed. For example, Japanese Patent Application Laid-Open No. 2014-36935 (Document 1) discloses a composite porous body having a MOF crystalline layer that can be used as a separation membrane. International Publication No. 2023 / 153172 (Document 2) and Japanese Patent Application Laid-Open No. 2016-67972 (Document 3) disclose mixed gas separation methods using MOF membranes as separation membranes. Document 2 describes that the mixed gas contains one or more substances selected from the group consisting of hydrogen, helium, nitrogen, oxygen, water, carbon monoxide, and carbon dioxide, and that the temperature of the mixed gas when supplied to the MOF membrane is 10 to 250°C. Document 3 describes that the temperature of the mixed gas is changed within a range from -70°C to 300°C to change the molecular diameter of the gas contained in the mixed gas.

[0003] In recent years, CO ２ There is a demand for separation membranes for CO separation. However, with MOF membranes, when the temperature of the mixed gas changes, ２ The permeation rate of CO changes significantly. ２ To maintain permeation performance, the temperature must be strictly controlled, which is not easy. Therefore, in the MOF membrane, stable CO ２ There is a need for a method to easily achieve transmission performance.

[0004] The present invention provides a method for producing a stable CO ２ The purpose is to easily achieve transmission performance.

[0005] The invention of aspect 1 is a method for producing CO from a mixed gas. ２a) preparing a separation membrane composite in which a separation membrane made of a metal-organic framework is provided on a porous support; b) adjusting the temperature of the mixed gas to within a limited temperature range determined according to the concentration of the moisture, when the mixed gas contains moisture; and c) supplying the mixed gas after the temperature adjustment in step b) to the separation membrane composite, and ２ and separating the CO contained in the mixed gas from the mixed gas by allowing the CO to permeate through the separation membrane, wherein the limited temperature range has a temperature width of 30°C within a range of 50 to 120°C, and ２ The fluctuation range of the permeation rate for the separation membrane composite is 20% or less.

[0006] According to the present invention, a separation membrane made of a metal organic framework can provide a stable CO ２ Transmission performance can be easily achieved.

[0007] A second aspect of the present invention is the separation method of the first aspect, further comprising, before the step c), a step of adjusting the concentration of the moisture in the mixed gas to fall within a set range.

[0008] The invention of Aspect 3 is the separation method of Aspect 1 or 2, wherein the metal element constituting the metal organic framework includes at least one selected from the group consisting of Al, Zr, Zn, and Cr.

[0009] A fourth aspect of the invention is the separation method according to any one of the first to third aspects, wherein in the metal organic framework, the ligand coordinated to the metal element has a carbon-carbon double bond or a carbon-nitrogen double bond, and a carboxyl group or a nitrogen-containing aromatic ring.

[0010] A fifth aspect of the invention is the separation method according to the fourth aspect, wherein the ligand comprises at least one selected from the group consisting of 2,5-furandicarboxylic acid, 2,5-thiophenedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 1H-pyrrole-2,5-dicarboxylic acid, fumaric acid, trimesic acid, isophthalic acid, 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid, 5-hydroxyisophthalic acid, imidazole, methylimidazole, and triazole.

[0011] A sixth aspect of the invention is the separation method according to any one of the first to fifth aspects, wherein the mixed gas contains at least one selected from the group consisting of hydrogen, helium, ammonia, carbon monoxide, oxygen, nitrogen, methane, methanol, ethanol, and hydrogen sulfide.

[0012] A seventh aspect of the present invention is the separation method according to any one of the first to sixth aspects, wherein the concentration of the water in the mixed gas is 300 to 100,000 ppm.

[0013] The invention of aspect 8 is a method for producing CO from a mixed gas. ２ a gas supply unit having a temperature control section, wherein the mixed gas contains moisture, the temperature control section controls the temperature of the mixed gas to within a limited temperature range determined according to the concentration of the moisture, and the gas supply unit supplies the mixed gas whose temperature has been controlled by the temperature control section to the separation membrane composite, and the CO in the mixed gas is separated from the mixed gas by the temperature control section. ２ is separated from the mixed gas by permeating the separation membrane, the limited temperature range having a temperature width of 30°C within a range of 50 to 120°C, and in the limited temperature range, CO contained in the mixed gas ２ The fluctuation range of the permeation rate for the separation membrane composite is 20% or less.

[0014] A ninth aspect of the present invention is the separation apparatus of the eighth aspect, wherein the gas supply unit further includes a moisture concentration adjusting section that adjusts the moisture concentration of the mixed gas within a set range.

[0015] 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.

[0016] 1 is a diagram showing the configuration of a separation device; FIG. 2 is a cross-sectional view of a separation membrane composite; FIG. 3 is a cross-sectional view showing an enlarged portion of the separation membrane composite; FIG. 4 is a diagram showing the flow of separation of a mixed gas; ２ 1 is a graph showing the relationship between the permeation rate and the temperature of the mixed gas. ２ 1 is a graph showing the relationship between the permeation rate and the temperature of the mixed gas. ２ 1 is a graph showing the relationship between the permeation rate and the temperature of the mixed gas. ２ FIG. 10 is a graph showing the relationship between the permeation rate and the temperature of the mixed gas.

[0017] FIG. 1 is a diagram showing the configuration of a separation device 2 according to one embodiment of the present invention. In FIG. 1, the hatched lines in the cross section of some of the components are omitted. The separation device 2 separates carbon dioxide (CO ) from a mixed gas containing multiple types of gases. ２ ) is separated. ２ is a substance (highly permeable substance) that has high permeability to the separation membrane 12 described later. Separation in the separation device 2 typically involves separating CO from the mixed gas. ２ However, it may also be performed to concentrate substances with low permeability.

[0018] 1 includes a separation membrane composite 1, a housing 22, two seal members 23, a gas supply unit 26, a first recovery section 27, and a second recovery section 28. The separation membrane composite 1 and the seal members 23 are housed within the housing 22. The gas supply unit 26, the first recovery section 27, and the second recovery section 28 are disposed outside the housing 22 and connected to the housing 22.

[0019] FIG. 2 is a cross-sectional view of a separation membrane composite 1. FIG. 3 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 membrane made of a metal-organic framework (MOF) (hereinafter also referred to as a "MOF membrane"), 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 membranes in which MOF particles are simply dispersed in an organic film. In FIG. 2, the separation membrane 12 is emphasized with a thick line. In FIG. 3, the separation membrane 12 is indicated by parallel diagonal lines. Furthermore, in FIG. 3, the thickness of the separation membrane 12 is depicted as being thicker than it actually is.

[0020] The support 11 is a porous member that is permeable to gas and liquid. In the example shown in FIG. 2 , the support 11 is a so-called monolithic support in which a plurality of through holes 111 extending in the longitudinal direction (i.e., the left-right direction in FIG. 2 ) are provided in an integrally molded, continuous columnar body. In the example shown in FIG. 2 , the support 11 is substantially cylindrical. A cross section perpendicular to the longitudinal direction of each through hole 111 (i.e., cell) is, for example, substantially circular. In FIG. 2 , the diameter of the through holes 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 holes 111 and covers the inner circumferential surface of the through holes 111 over substantially the entire surface.

[0021] The length of the support 11 (i.e., the length in the left-right direction in FIG. 2 ) 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.

[0022] The support 11 is formed of, for example, 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.

[0023] 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.

[0024] 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, and 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.

[0025] 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 (permeation rate per unit membrane area and unit pressure difference) is lower than the permeation rate of the specific substance.

[0026] The average thickness of the separation membrane 12 is, for example, 5 μm or less, preferably 3 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, for example, 0.2 μm, preferably 0.5 μm, and 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 (for example, seven fields) are observed using an SEM. The magnification of the SEM is, for example, 5000 times. 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.

[0027] As described above, the separation membrane 12 is composed of MOFs. That is, the separation membrane 12 is a MOF membrane. The separation membrane 12 is typically composed only of MOFs, but depending on the production method, the separation membrane 12 may contain a small amount (for example, 1 mass % or less) of a substance other than the MOF.

[0028] The average pore diameter of the MOF membrane constituting the separation membrane 12 is, for example, 1 nm or less, preferably 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. The long and short diameters of the pore openings, more 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 the structural type. The pore diameter here refers to the pore diameter of the channel, with the long diameter being the maximum diameter in the cross section of the channel and the short diameter being the diameter of the cross section in a direction approximately perpendicular to the long diameter, and the arithmetic mean of the short diameter and the long diameter being the average pore diameter. The average pore diameter is smaller than the average pore diameter of the support 11 near the surface on which the separation membrane 12 is formed.

[0029] 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 MOFs in this embodiment is the arithmetic mean of the maximum Feret 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.

[0030] 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. 3 , 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 have to be present, and the lower limit of the thickness of the composite layer 13 is 0.

[0031] 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 substantially continuous with the separation membrane 12 in the depth direction but is farthest from the separation membrane 12. 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.

[0032] 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.

[0033] 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 that are components of the MOF preferably contain at least one selected from the group consisting of Al ions, Zr ions, Zn ions, and Cr ions. In other words, the metal elements constituting the MOF contain at least one selected from the group consisting of Al, Zr, Zn, and Cr. Preferably, the number of types of metal ions contained in the MOF is one, but multiple types may be present. Furthermore, the metal elements constituting the MOF may be elements other than those exemplified above.

[0034] The ligands that are components of MOFs, i.e., the ligands coordinated to the metal elements, preferably have both hydrophobic and hydrophilic moieties, since this can reduce the fluctuation range of the gas permeation rate in the limited temperature range described below. As the hydrophobic moiety, a carbon-carbon double bond or a carbon-nitrogen double bond is preferred, with a carbon-carbon double bond being more preferred. As the hydrophilic moiety, electron-donating oxygen (e.g., the oxygen atom of a carboxyl group) or electron-donating nitrogen (e.g., the nitrogen atom of a nitrogen-containing aromatic ring) is preferred, with electron-donating oxygen being more preferred. In other words, the ligand preferably has a carbon-carbon double bond or a carbon-nitrogen double bond and a carboxyl group or a nitrogen-containing aromatic ring, and more preferably has a carbon-carbon double bond and a carboxyl group. By using such a ligand, the water adsorption force to the MOF can be maintained at an appropriate value, and the fluctuation range of the gas permeation rate in the limited temperature range can be further reduced. For example, the ligand includes at least one selected from the group consisting of 2,5-furandicarboxylic acid, 2,5-thiophenedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 1H-pyrrole-2,5-dicarboxylic acid, fumaric acid, trimesic acid, isophthalic acid, 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid, 5-hydroxyisophthalic acid, imidazole, methylimidazole, and triazole. The ligand may be a substance other than those exemplified above.

[0035] Here, an example of a manufacturing flow of the separation membrane composite 1 will be described. In the manufacturing of the separation membrane composite 1, first, seed crystals to be used in manufacturing the separation membrane 12 are prepared. The seed crystals are produced as MOF powders, for example, by solvothermal synthesis using water and / or an organic solvent (also called hydrothermal synthesis when the solvent is water). The MOF powders may be produced by any or known manufacturing method. The MOF powders may be used as seed crystals directly, or more preferable seed crystals may be obtained by processing the powders by pulverization or the like.

[0036] 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. The dispersion in which the seed crystals are dispersed in the 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. For example, a dip coating method can be used in which the porous support 11 is immersed in the dispersion to attach 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.

[0037] Next, a raw material solution (also called a synthetic sol or synthesis solution) to be used in forming the MOF membrane is prepared. The raw material solution may be prepared in advance. In preparing the raw material solution, a solvent (water and / or an organic solvent), a ligand, a metal ion source, and the like are mixed. For example, the ligand is added to the solvent, and the ligand is dissolved by stirring, ultrasonic treatment, or heating in a thermostatic bath. Then, metal ions are added to obtain the raw material solution.

[0038] Once the raw material solution is prepared, a 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 the solvothermal synthesis, MOFs grow using the seed crystals as nuclei, and a separation membrane 12, which is an MOF membrane, is formed on the support 11. The synthesis temperature (heating temperature of the raw material solution) during the solvothermal synthesis is, for example, 40 to 200°C, preferably 70 to 160°C. The solvothermal synthesis time is, for example, 1 to 100 hours, preferably 1 to 50 hours.

[0039] After the solvothermal synthesis is complete, 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. "Drying" refers to removing molecules of the substances used for washing, such as water and ethanol, from the pores of the MOF membrane. This completes the separation membrane composite 1.

[0040] As shown in FIG. 1 , in the separation membrane composite 1, sealing portions 21 are provided at both longitudinal ends of the support 11. The sealing portions 21 are attached to both longitudinal ends of the support 11 (i.e., the left-right direction in FIG. 1 ) and are members that cover and seal both longitudinal end faces of the support 11 and the outer peripheral surfaces near these end faces. The sealing portions 21 prevent gas from flowing in or out from these end faces of the support 11. The sealing portions 21 are, for example, plate-like members formed of glass or resin. The material and shape of the sealing portions 21 may be changed as appropriate. Note that the sealing portions 21 have multiple openings that overlap with the multiple through holes 111 in the support 11, and therefore both longitudinal ends of each through hole 111 in the support 11 are not covered by the sealing portions 21. Therefore, gas and the like can flow in and out of the through holes 111 from these ends.

[0041] 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. 1 ), 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 gas supply unit 26 is connected to the supply port 221. A first recovery section 27 is connected to the first discharge port 222. A second recovery section 28 is connected to the second discharge port 223. The internal space of the housing 22 is a sealed space isolated from the space surrounding the housing 22.

[0042] 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. 1 , 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.

[0043] The gas supply unit 26 includes a supply pipe 261, a water concentration adjuster 262, a temperature adjuster 263, and an adjustment valve 264. The supply pipe 261 connects the mixed gas supply source 91 and the supply port 221 of the housing 22. The supply pipe 261 is provided with the water concentration adjuster 262, the temperature adjuster 263, and the adjustment valve 264, in this order from the supply source 91 toward the housing 22. As described below, the order of the water concentration adjuster 262, the temperature adjuster 263, and the adjustment valve 264 may be changed as appropriate. Furthermore, the adjustment valve 264 may be provided between the first recovery section 27 and the first discharge port 222, rather than in the gas supply unit 26. Note that if the pressure of the mixed gas is an appropriate value and is approximately constant, the adjustment valve 264 may be omitted.

[0044] The moisture concentration adjuster 262 includes, for example, a moisture concentration meter, a humidifier, and a concentration control unit. The moisture concentration meter measures the moisture concentration of the mixed gas flowing through the supply pipe 261. The humidifier supplies water vapor to the mixed gas flowing through the supply pipe 261. The concentration control unit controls the humidifier based on the measurement value of the moisture concentration meter. For example, the concentration control unit pre-sets a target range (hereinafter referred to as the "set range") for the moisture concentration of the mixed gas. If the measurement value of the moisture concentration meter is lower than the set range, the concentration control unit increases the amount of water vapor supplied by the humidifier, and if the measurement value of the moisture concentration meter is higher than the set range, the concentration control unit decreases the amount of water vapor supplied by the humidifier. This adjusts the moisture concentration of the mixed gas to within the set range. Note that the moisture concentration meter and concentration control unit may be omitted if the moisture concentration of the mixed gas can be adjusted within the set range. The set range of moisture concentration will be described in detail below. The concentration control unit is implemented, for example, by a control electrical circuit (the same applies to the other control units described below). The concentration control unit, together with other control units, may be realized by a computer having a CPU or the like. In the moisture concentration adjustment unit 262, for example, instead of a humidifier, a dehumidifier using a cooling device, a dehydrating membrane, an adsorbent, or the like may be used to dehumidify the mixed gas. Note that if the moisture concentration of the mixed gas is an appropriate value and is approximately constant, the moisture concentration adjustment unit 262 may be omitted.

[0045] The temperature adjustment unit 263 includes, for example, a thermometer, a heater, and a temperature control unit. The thermometer measures the temperature of the mixed gas flowing through the supply pipe 261. The heater is an electric or fuel-powered heater, a heat exchanger using steam, or the like, and heats the mixed gas flowing through the supply pipe 261. The temperature control unit controls the heater based on the measurement value of the thermometer. For example, the temperature control unit pre-sets a predetermined temperature range (hereinafter referred to as the "limited temperature range") for the temperature of the mixed gas. When the measurement value of the thermometer is lower than the limited temperature range, the temperature control unit increases the heating temperature of the mixed gas by the heater, and when the measurement value of the thermometer is higher than the limited temperature range, the temperature control unit decreases the heating temperature of the mixed gas by the heater. In this way, the temperature of the mixed gas is adjusted to within the limited temperature range. Details of the limited temperature range will be described later. As will be described later, control may be performed to adjust the temperature of the mixed gas to a temperature range narrower than the limited temperature range. In the temperature adjustment unit 263, for example, instead of a heater, a cooler using a refrigerant or the like may be used to cool the mixed gas. Furthermore, a temperature regulator (heater or cooler), a heat insulator, etc. may be provided on the outside of the housing 22 in order to adjust the temperature of the mixed gas.

[0046] The adjustment valve 264 adjusts the pressure of the mixed gas supplied to the housing 22. A pressure gauge may be provided in the supply pipe 261, and a pressure control unit may control the adjustment valve 264 based on the measurement value of the pressure gauge. Note that if the pressure of the mixed gas is an appropriate value and is approximately constant, the adjustment valve 264 may be omitted. The mixed gas flowing through the supply pipe 261 is supplied to the internal space of the housing 22 via the supply port 221. The gas supply unit 26 may include a blower, a pump, or the like that pressure-feeds the mixed gas toward the housing 22.

[0047] The first recovery unit 27 recovers the gas discharged from the first exhaust port 222. The second recovery unit 28 recovers the gas discharged from the second exhaust port 223. As will be described later, the gas recovered in the second recovery unit 28 is mainly CO ２ The second recovery section 28 ２ A processing unit is connected to perform processing using the recovered CO ２The gas is used for processing in the processing unit. The first collection unit 27 and the second collection unit 28 may be provided with a storage container for storing the collected gas, and may also be provided with a blower, a pump, or the like for transporting the gas.

[0048] 4 is a diagram showing the flow of separation of a mixed gas by the separation device 2. Here, the mixed gas contains multiple types of gases with different permeabilities to the separation membrane 12, specifically, CO ２ and other gases. The other gases include, for example, hydrogen (H ２ ), helium (He), ammonia (NH ３ ), carbon monoxide (CO), oxygen (O ２ ), nitrogen (N ２ ), methane (CH ４ ), methanol (CH ３ OH), ethanol (C ２ H ５ OH) and hydrogen sulfide (H ２ The other gas typically includes at least one selected from the group consisting of CO ２ The mixed gas is a substance (low-permeable substance) that has a low permeability through the separation membrane 12 compared to CO, and may be a gas other than the substances exemplified above. ２ The main component of the mixed gas in this processing example is CO ２ and N ２ The mixed gas contains CO ２ and N ２ Other gases may also be included.

[0049] In the separation of a mixed gas, the separation device 2 described above is prepared, thereby preparing the separation membrane composite 1 (step S11). Next, the gas supply unit 26 supplies the mixed gas to the internal space of the housing 22. Specifically, the mixed gas is supplied from the supply source 91 into the supply pipe 261, and the moisture concentration of the mixed gas flowing through the supply pipe 261 is adjusted to within a set range by the moisture concentration adjuster 262 (step S12). For example, the set moisture concentration range is higher than the moisture concentration of the mixed gas before the moisture concentration adjustment, and the mixed gas is humidified by the moisture concentration adjuster 262. The mixed gas before the moisture concentration adjustment may contain moisture or may contain almost no moisture. The moisture concentration of the mixed gas before the moisture concentration adjustment may be approximately the same as or higher than the set range. If the moisture concentration of the mixed gas before the moisture concentration adjustment is higher than the set range, the mixed gas may be dehumidified by the moisture concentration adjuster 262.

[0050] Next, in the temperature adjusting unit 263, the temperature of the mixed gas flowing through the supply pipe 261 is adjusted to within a limited temperature range (step S13). For example, the limited temperature range is higher than the temperature of the mixed gas before the temperature adjustment, and the mixed gas is heated in the temperature adjusting unit 263. As will be described later, by adjusting the temperature of the mixed gas to within the limited temperature range, stable CO ２ If the temperature of the mixed gas before the temperature adjustment is higher than the temperature limit range, the mixed gas may be cooled by the temperature adjustment unit 263.

[0051] The adjustment valve 264 adjusts the pressure of the mixed gas after adjusting the water concentration and temperature, and the pressure-adjusted mixed gas is supplied into the housing 22 via the supply port 221. The pressure of the mixed gas supplied to the internal space of the housing 22 (i.e., the introduction pressure) is, for example, 0.1 MPa to 20.0 MPa. In the gas supply unit 26, the arrangement of the water concentration adjuster 262, the temperature adjuster 263, and the adjustment valve 264 may be changed as appropriate, as long as the gas supply unit 26 can supply into the housing 22 a mixed gas whose water concentration is within a set range and whose temperature is within a restricted temperature range. If the water concentration of the mixed gas before supply to the gas supply unit 26 (i.e., the mixed gas discharged from the supply source 91) is an appropriate value and is approximately constant, the water concentration adjuster 262 may be omitted. Similarly, if the pressure of the mixed gas is an appropriate value and is approximately constant, the adjustment valve 264 may be omitted.

[0052] The mixed gas supplied from the gas 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. ２ The CO 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. ２ However, the gas with low permeability in the mixed gas (e.g., N ２ The gas (hereinafter referred to as "permeable material") discharged from the outer peripheral surface of the support 11 is collected by the second collection section 28 via the second discharge port 223 as shown by the arrow 253. Most of the permeable material is CO ２ The pressure (i.e., permeation pressure) of the gas recovered by the second recovery section 28 via the second discharge port 223 is, for example, 0 MPa to 0.10 MPa (approximately 1 atmosphere).

[0053] Furthermore, gases (hereinafter referred to as "impermeable substances") in the mixed gas excluding the gas that has permeated the separation membrane 12 and the support 11 pass through each through-hole 111 of the support 11 from left to right in the figure, and are recovered by the first recovery section 27 via the first discharge port 222, as shown by arrow 252. The pressure of the gas recovered by the first recovery section 27 via the first discharge port 222 is, for example, approximately the same as the introduction pressure. In addition to the above-mentioned low-permeability substances, impermeable substances include CO 2 that did not permeate the separation membrane 12, ２ may be included.

[0054] Here, the temperature limit range of the mixed gas will be explained. ２ The permeation rate (permeance) of the separation membrane composite (hereinafter simply referred to as "CO ２ 5 is a graph showing the relationship between the CO permeation rate (hereinafter referred to as the "permeation rate") and the temperature of the mixed gas. Line L11 in FIG. 5 shows the relationship between the CO permeation rate (hereinafter referred to as the "permeation rate") and the temperature of the mixed gas. ２ The line L12 shows the CO permeation rate when the mixed gas does not contain moisture (the moisture concentration is 0 ppm). ２ The permeation rate is shown in FIG. ２ The relationship between the permeation rate and the temperature of the mixed gas is ２ 50% by volume, N ２ 50% by volume of a mixed gas and a separation membrane composite of Sample No. 1 described later, and was obtained by varying only the temperature of the mixed gas supplied to the separation membrane composite.

[0055] When the mixed gas does not contain moisture, as shown by the line L12 in FIG. 5, as the temperature of the mixed gas increases, the CO ２ On the other hand, when the mixed gas contains moisture, as shown by line L11, in the relatively low temperature range of the mixed gas, the water is adsorbed on the separation membrane, and the CO ２ The permeation of CO ２ When the temperature of the mixed gas rises to a certain level, water is desorbed from the separation membrane and CO ２ is more easily transmitted, ２When the temperature of the mixed gas further increases and the amount of water adsorbed on the separation membrane becomes sufficiently small, CO2 increases with the temperature of the mixed gas, just as when the mixed gas does not contain moisture. ２ In this way, when the mixed gas contains moisture, the CO ２ The relationship between the permeation rate and the temperature of the mixed gas exhibits a mountain-like shape.

[0056] The temperature range of the mixed gas is 50 to 120°C with a temperature width of 30°C. When only the temperature of the mixed gas is changed, the CO ２ This is the temperature range in which the fluctuation range of the permeation rate is 20% or less (0% or more). ２ The fluctuation range of the permeation rate is the CO ２ The difference between the maximum and minimum values ​​of the permeation rate is divided by the minimum value. In the example of FIG. 5, the limit temperature range W1 is determined to be 50 to 80°C. The line L11 shows the CO ２ The difference between the maximum and minimum values ​​of the permeation rate is V11, and the minimum value is the CO ２ CO permeation rate in the limited temperature range W1 ２ The fluctuation range of the permeation rate is 14%. For example, ２ In the change of the permeation rate, in the temperature range of 50 to 80°C (limited temperature range W1), which is a temperature range of 30°C within the range of 50 to 120°C, ２ The fluctuation range of the permeation rate is minimized.

[0057] On the other hand, in the case where the mixed gas does not contain moisture, the line L12 indicates that the CO ２ The difference between the maximum and minimum values ​​of the permeation rate is V12, which is significantly larger than the difference V11 when the mixed gas contains moisture. ２ The permeation rate is almost the same as when the mixed gas contains moisture. ２ The fluctuation range of the permeation rate is 47%. ２ The fluctuation range of the permeation rate is significantly smaller than the fluctuation range when the mixed gas does not contain moisture.

[0058] Therefore, by making water coexist in the mixed gas and adjusting the temperature of the mixed gas to be within the restricted temperature range W1, even if the temperature of the mixed gas varies to some extent within the restricted temperature range W1, the CO ２ The temperature range W1 of the mixed gas has a temperature width of 30°C within the range of 50 to 120°C, and the CO ２ The temperature range may be arbitrarily determined as long as the fluctuation width of the permeation rate is 20% or less. For example, in the example of FIG. 5, even if the limit temperature range W1 is determined to be 55 to 85°C, ２ The fluctuation range of the permeation rate is 20% or less. ２ In the limited temperature range W1, the temperature at which the permeation rate is maximum (i.e., the peak temperature of the line L11) is included. ２ The fluctuation range of the permeation rate is preferably 1 / 2 or less, more preferably 1 / 3 or less, of the fluctuation range when the mixed gas does not contain moisture. ２ The fluctuation range of the permeation rate is preferably 18% or less, and more preferably 15% or less.

[0059] The moisture concentration of the mixed gas is not limited to 2500 ppm and may be changed as appropriate. ２ The moisture concentration of the mixed gas is set so that the fluctuation range of the permeation rate is 20% or less. ２ Since the relationship between the permeation rate and the temperature of the mixed gas varies depending on the water concentration of the mixed gas, the limit temperature range W1 of the mixed gas is determined according to the water concentration of the mixed gas supplied to the separation membrane composite. The set range of the water concentration of the mixed gas is, for example, 0.7 to 1.3 times, preferably 0.8 to 1.2 times, and more preferably 0.9 to 1.1 times the water concentration at the time of determining the limit temperature range W1 (2500 ppm in the above example). The CO2 obtained from the mixed gas with a water concentration at the upper limit of the set range is ２In the relationship between the permeation rate and the temperature of the mixed gas, ２ It is preferable that the fluctuation range of the permeation rate is 20% or less. Similarly, the CO ２ In the relationship between the permeation rate and the temperature of the mixed gas, ２ It is preferable that the fluctuation range of the permeation rate is 20% or less.

[0060] The water concentration of the mixed gas supplied to the separation membrane composite is, for example, 300 to 100,000 ppm, preferably 500 to 50,000 ppm, and more preferably 1,000 to 10,000 ppm. This allows an appropriate temperature limit range W1 to be set more reliably. The setting range of the water concentration of the mixed gas is also preferably within the above range. Depending on the water concentration of the mixed gas before water concentration adjustment, the water concentration of the mixed gas supplied to the separation membrane composite may be outside the range of 300 to 100,000 ppm. As described above, if the water concentration of the mixed gas discharged from the supply source 91 is an appropriate value and is approximately constant, adjustment of the water concentration may be omitted.

[0061] As described above, the separation method shown in FIG. 4 includes a step of preparing separation membrane composite 1 in which separation membrane 12 made of a metal-organic framework is provided on porous support 11 (step S11); a step of adjusting the temperature of a mixed gas containing moisture to within a limited temperature range W1 determined according to the moisture concentration (step S13); and a step of supplying the mixed gas after temperature adjustment in step S13 to separation membrane composite 1 to remove CO from the mixed gas. ２ and a step (step S14) of separating the CO contained in the mixed gas by passing it through the separation membrane 12. The limited temperature range W1 has a temperature width of 30°C within the range of 50 to 120°C. ２ The fluctuation range of the permeation rate of the separation membrane composite 1 is 20% or less. ２In other words, it is possible to produce stable CO 2 in the separation membrane 12 without strictly adjusting the temperature of the mixed gas (i.e., by roughly adjusting the temperature of the mixed gas). ２ As a result, it is possible to provide a separation system that is easy to control. ２ This allows stable post-processing using the above.

[0062] In step S13, if the temperature of the mixed gas is adjusted to be within the restricted temperature range W1, control may be performed to adjust the temperature of the mixed gas to be within a target temperature range narrower than the restricted temperature range W1. For example, ２ When the target temperature range is set to a temperature range approximately centered on the temperature at which the permeation rate is maximized, ２ In addition, when the mixed gas is heated in step S13, if the lower temperature range in the restricted temperature range W1 is set as the target temperature range, the energy required to heat the mixed gas can be reduced.

[0063] A preferred separation method further includes a step of adjusting the moisture concentration of the mixed gas to within a set range before step S14. This makes it possible to keep the moisture concentration of the mixed gas supplied to the separation membrane composite 1 approximately constant even when the moisture concentration of the mixed gas discharged from the supply source 91 fluctuates. As a result, CO ２ Reduce the change in permeation rate, i.e., CO ２ The permeability can be stabilized.

[0064] 1 includes the separation membrane composite 1 and a gas supply unit 26 having a temperature adjustment section 263. The temperature adjustment section 263 adjusts the temperature of the mixed gas to within the restricted temperature range W1. The gas supply unit 26 supplies the mixed gas whose temperature has been adjusted by the temperature adjustment section 263 to the separation membrane composite 1, and ２ is separated from the mixed gas by permeating the separation membrane 12. As a result, stable CO ２Transmission performance can be easily achieved.

[0065] Next, CO from the mixed gas ２ First, the preparation of the separation membrane composites of sample numbers 1 to 4 used in this experiment will be described.

[0066] (Preparation of Separation Membrane Composite of Sample No. 1) <Preparation of Seed Crystals> A mixed solution was prepared by mixing 1.551 g of 1H-pyrrole-2,5-dicarboxylic acid and 1.36 g of sodium formate with 50 mL of deionized water. The mixed solution was stirred at 50°C for 3 hours, then cooled to room temperature, and 3.33 g of aluminum sulfate 18-hydrate was added. Next, this solution was maintained at 120°C for 12 hours to perform solvothermal synthesis. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. As a result, a powder of MOF containing 1H-pyrrole-2,5-dicarboxylic acid as a ligand was obtained as seed crystals.

[0067] <Supporting of seed crystals on ceramic support> 1 g of the obtained seed crystals 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 to obtain seed crystals with an average particle size (D50) of 0.33 μm. The seed crystals were then supported on a ceramic support.

[0068] <Preparation of Separation Membrane Composite> 1.55 g of 1H-pyrrole-2,5-dicarboxylic acid, 1.22 g of sodium formate, and 0.58 g of N,N-dimethylformamide as an organic solvent were added to 150 mL of deionized water to prepare a mixed solution. The mixed solution was heated to 60°C and stirred for 2 hours (heating and stirring treatment). After confirming that the mixed solution had become transparent, it was cooled to room temperature. 3.333 g of aluminum sulfate 18-hydrate was then added to the mixed solution to prepare a synthesis solution. Next, the ceramic support carrying seed crystals and the synthesis solution were placed in a Teflon (registered trademark) container and held at 100°C for 20 hours to perform solvothermal synthesis. The obtained separation membrane composite was washed three times with deionized water and ethanol, and then dried. Through the above treatment, a separation membrane composite designated Sample No. 1 was obtained.

[0069] (Preparation of Separation Membrane Composite of Sample No. 2) <Preparation of Seed Crystals> A mixed solution was prepared by mixing 1.56 g of 2,5-furandicarboxylic acid and 1.36 g of sodium formate with 50 mL of deionized water. The mixed solution was stirred at 50°C for 3 hours, then cooled to room temperature, and 2.41 g of aluminum chloride hexahydrate was added. Next, this solution was maintained at 100°C for 12 hours to perform solvothermal synthesis. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. As a result, a powder of MOF containing 2,5-furandicarboxylic acid as a ligand was obtained as seed crystals.

[0070] <Supporting of seed crystals on ceramic support> 1 g of the obtained seed crystals 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 to obtain seed crystals with an average particle size (D50) of 0.25 μm. The seed crystals were then supported on a ceramic support.

[0071] <Preparation of Separation Membrane Composite> 1.56 g of 2,5-furandicarboxylic acid, 1.22 g of sodium formate, and 0.58 g of N,N-dimethylformamide as an organic solvent were added to 150 mL of deionized water to prepare a mixed solution. The mixed solution was heated to 60°C and stirred for 2 hours (heating and stirring treatment). After confirming that the mixed solution had become transparent, it was cooled to room temperature. 2.41 g of aluminum chloride hexahydrate was then added to the mixed solution to prepare a synthesis solution. Next, the ceramic support carrying seed crystals and the synthesis solution were placed in a Teflon container and held at 80°C for 20 hours to perform solvothermal synthesis. The obtained separation membrane composite was washed three times with deionized water and ethanol and then dried. Through the above treatment, a separation membrane composite of sample number 2 was obtained.

[0072] (Preparation of Separation Membrane Composite of Sample No. 3) <Preparation of Seed Crystals> 0.28 g of fumaric acid and 0.34 g of sodium formate were mixed with 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. Next, this solution was held at 120°C for 12 hours to perform solvothermal synthesis. The precipitate was separated using a centrifuge and washed three times with deionized water and ethanol. As a result, a powder of MOF containing fumaric acid as a ligand was obtained as seed crystals.

[0073] <Supporting of seed crystals on ceramic support> 1 g of the obtained seed crystals 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 to obtain seed crystals with an average particle size (D50) of 0.25 μm. The seed crystals were then supported on a ceramic support.

[0074] <Preparation of Separation Membrane Composite> 0.39 g of fumaric acid and 0.45 g of sodium formate 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 (heating and stirring treatment). After confirming that the mixed solution had become transparent, it was cooled to room temperature. 1.10 g of aluminum sulfate 18-hydrate was then added to the mixed solution to prepare a synthesis solution. Next, the ceramic support carrying seed crystals and the synthesis solution were placed in a Teflon container and held at 100°C for 20 hours to perform solvothermal synthesis. The obtained separation membrane composite was washed three times with deionized water and ethanol, and then dried. Through the above treatment, a separation membrane composite of sample number 3 was obtained.

[0075] (Preparation of Separation Membrane Composite of Sample No. 4) <Preparation of Seed Crystals> 0.67 g of zinc chloride was added to 50 mL of methanol, and 1.62 g of 2-methylimidazole was added to another 50 mL of methanol. These solutions were mixed to prepare a mixed solution. The mixed solution was stirred at room temperature for 6 hours and then held at 30°C for 24 hours to perform solvothermal synthesis. The precipitate was separated using a centrifuge and washed three times with deionized water and methanol. As a result, a powder of MOF containing 2-methylimidazole as a ligand was obtained as seed crystals.

[0076] <Supporting of seed crystals on ceramic support> 1 g of the obtained seed crystals 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 to obtain seed crystals with an average particle size (D50) of 0.25 μm. The seed crystals were then supported on a ceramic support.

[0077] <Preparation of separation membrane composite> 1.86 g of 2-methylimidazole and 1.01 g of sodium formate were added to 150 mL of methanol to prepare a mixed solution. The mixed solution was stirred at room temperature for 1 hour. After confirming that the mixed solution had become transparent, 2.00 g of zinc chloride was added to the mixed solution to prepare a synthesis solution. Next, the ceramic support carrying the seed crystals and the synthesis solution were placed in a Teflon container and kept at 130°C for 7 hours to perform solvothermal synthesis. The obtained separation membrane composite was washed three times with deionized water and methanol, and then dried. Through the above treatment, a separation membrane composite of sample number 4 was obtained.

[0078] (CO ２ Measurement of permeation rate) For the separation membrane composites of sample numbers 1 to 4, CO ２ 50% by volume, N ２ A gas separation test was carried out using a mixed gas with a composition of 50% by volume of CO₂ and a mixed gas with 2500 ppm of water added. The pressure of the supplied mixed gas was 0.3 MPa, the pressure on the permeation side was 0.1 MPa, and the gas separation test was carried out in the range of 50°C to 120°C. ２ The permeation rate (Permeance) was determined.

[0079] 5 shows the results of a gas separation test using the separation membrane composite of sample number 1, FIG. 6 shows the results of a gas separation test using the separation membrane composite of sample number 2, FIG. 7 shows the results of a gas separation test using the separation membrane composite of sample number 3, and FIG. 8 shows the results of a gas separation test using the separation membrane composite of sample number 4. Lines L11, L21, L31, and L41 in FIGS. 5 to 8 show the results of a CO separation test using the separation membrane composite of sample number 1 when the moisture concentration of the mixed gas is 2500 ppm. ２Lines L12, L22, L32, and L42 show the CO permeation rate when the mixed gas does not contain moisture (the moisture concentration is 0 ppm). ２ The permeation rate is shown.

[0080] CO in mixed gas containing moisture ２ In the change in the permeation rate (lines L11, L21, L31, and L41 in FIGS. 5 to 8), when a temperature range of 30°C is set within the range of 50 to 120°C, ２ The temperature range where the fluctuation range of the permeation rate is the smallest was determined as the limiting temperature range. ２ The fluctuation range of the permeation rate is shown in Table 1. ２ Table 1 also shows the value (improvement ratio) of the fluctuation range of the permeation rate in a mixed gas containing no moisture relative to the fluctuation range in the limited temperature range.

[0081]

[0082] As shown in Table 1, the separation membrane composite of sample number 1 had a temperature limit of 50 to 80°C, and the CO ２ The fluctuation range of the permeation rate in the limiting temperature range was 14%. For the separation membrane composite of sample No. 2, the limiting temperature range was determined to be 82 to 112°C, and the CO permeation rate in the mixed gas containing moisture was ２ The fluctuation range of the permeation rate in the limiting temperature range was 10%. For the separation membrane composite of sample No. 3, the limiting temperature range was determined to be 75 to 105°C, and the CO permeation rate in the mixed gas containing moisture was ２ The fluctuation range of the permeation rate in the limiting temperature range was 8%. For the separation membrane composite of sample No. 4, the limiting temperature range was determined to be 50 to 80°C, and the CO permeation rate in the mixed gas containing moisture was ２ The fluctuation range of the permeation rate in the limited temperature range was 9%. In all of the separation membrane composites of Samples 1 to 4, the CO permeation rate in the limited temperature range when the mixed gas contains moisture was ２ The fluctuation range of the permeation rate was significantly smaller than that when the mixed gas did not contain moisture. ２Furthermore, the separation membrane composites of sample numbers 1 to 3, in which the ligand had a carbon-carbon double bond and a carboxyl group, generally had a larger improvement ratio than the separation membrane composite of sample number 4, in which the ligand did not have a carbon-carbon double bond or a carboxyl group.

[0083] The separation method and separation device 2 described above can be modified in various ways.

[0084] As already mentioned, the mixed gas may contain substances other than those exemplified in the above description.

[0085] In the separation membrane composite 1 , a separately formed intermediate layer may be present between the support 11 and the separation membrane 12 .

[0086] The separation membrane composite 1 may be produced by a method other than the above-described production method.

[0087] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0088] 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.

[0089] The separation method and separation device of the present invention can be used to separate various substances in various fields.

[0090] REFERENCE SIGNS LIST 1 separation membrane composite 2 separation device 11 support 12 separation membrane 26 gas supply unit 262 water concentration adjusting section 263 temperature adjusting section S11 to S14 steps W1 limited temperature range

Claims

1. CO from mixed gas ２ a) preparing a separation membrane composite in which a separation membrane made of a metal organic framework is provided on a porous support; b) adjusting the temperature of the mixed gas containing moisture to within a limited temperature range determined according to the concentration of the moisture; and c) supplying the mixed gas after the temperature adjustment in step b) to the separation membrane composite, and ２ from the mixed gas by permeating the separation membrane, wherein the limited temperature range has a temperature width of 30°C within a range of 50 to 120°C, and in the limited temperature range, ２ The separation method of claim 1, wherein the fluctuation range of the permeation rate through the separation membrane composite is 20% or less.

2. The separation method according to claim 1, further comprising the step of adjusting the moisture concentration of the mixed gas to within a set range before step c).

3. The separation method according to claim 1, wherein the metal element constituting the metal organic framework includes at least one selected from the group consisting of Al, Zr, Zn and Cr.

4. The separation method according to claim 1, wherein in the metal organic framework, the ligand coordinated to the metal element has a carbon-carbon double bond or a carbon-nitrogen double bond, and a carboxyl group or a nitrogen-containing aromatic ring.

5. The separation method according to claim 4, wherein the ligand comprises at least one selected from the group consisting of 2,5-furandicarboxylic acid, 2,5-thiophenedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 1H-pyrrole-2,5-dicarboxylic acid, fumaric acid, trimesic acid, isophthalic acid, 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid, 5-hydroxyisophthalic acid, imidazole, methylimidazole, and triazole.

6. The separation method according to claim 1, wherein the mixed gas contains at least one selected from the group consisting of hydrogen, helium, ammonia, carbon monoxide, oxygen, nitrogen, methane, methanol, ethanol, and hydrogen sulfide.

7. A separation method according to any one of claims 1 to 6, wherein the concentration of the water in the mixed gas is 300 to 100,000 ppm.

8. CO from mixed gases ２ a gas supply unit having a temperature adjustment section; and a separation membrane composite in which a separation membrane made of a metal organic framework is provided on a porous support; wherein the mixed gas contains moisture, and the temperature adjustment section adjusts the temperature of the mixed gas to within a limited temperature range determined according to the concentration of the moisture, and the gas supply unit supplies the mixed gas whose temperature has been adjusted by the temperature adjustment section to the separation membrane composite, and detects CO in the mixed gas. ２ is separated from the mixed gas by permeating the separation membrane, the limited temperature range having a temperature width of 30°C within a range of 50 to 120°C, and in the limited temperature range, CO contained in the mixed gas is ２ The separation device has a permeation rate fluctuation range of 20% or less for the separation membrane composite.

9. A separation apparatus according to claim 8, wherein the gas supply unit further comprises a moisture concentration adjusting section for adjusting the moisture concentration of the mixed gas within a set range.

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