Gas separation membrane and method for producing gas separation membrane

Abstract

The purpose of the present invention is to provide: a gas separation membrane which utilizes advantages of two or more kinds of metals, and which has more excellent gas separation performance; and a method for producing such a gas separation membrane.　This gas separation membrane is characterized by containing a composite metal oxide that includes two or more kinds of metals, and two or more kinds of organic ligands. It is preferable that the two or more kinds of metals are selected from the group consisting of group 2 metal elements, group 3 metal elements, group 4 metal elements, group 13 metal elements, and group 14 metal elements.

Description

Gas separation membrane and method for producing gas separation membrane

[0001] This disclosure relates to a gas separation membrane and a method for manufacturing the gas separation membrane. This application claims priority to Japanese Patent Application No. 2023-137352, filed in Japan on August 25, 2023, and Japanese Patent Application No. 2023-192871, filed in Japan on November 13, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, there has been a demand for the development of sustainable manufacturing processes from the perspectives of environmental friendliness and resource recycling. Accordingly, the importance of environmental friendliness and resource recycling has increased for purification technologies, which are essential in various manufacturing processes, and improvements in energy efficiency and quality are being further demanded. In light of this current situation, gas separation membranes with high energy efficiency and excellent gas separation ability (i.e., the ability to separate two or more gas molecules with high selectivity) are being developed.

[0003] Zirconia is an example of a material for gas separation membranes. However, zirconia alone has the disadvantage of being highly crystalline, and the gaps between the crystalline particles become the pores in the gas separation membrane, resulting in large pore sizes and poor gas separation ability. Therefore, it has been difficult to provide a gas separation membrane with excellent gas separation ability from only one material. Therefore, attempts have been made to develop gas separation membranes that use two or more metals as materials, taking advantage of the advantages of each metal, and exhibiting better gas separation ability. However, when two or more metals are used as materials, a new problem arises: it is difficult to obtain a homogeneous composite metal oxide due to the differences in the reactivity of each metal.

[0004] Patent Document 1 describes that the use of a specific organic chelating agent makes it possible to control the reactivity of metal alkoxide, which is a precursor of a composite metal oxide containing TiO2 and SiO2 or Al2O3, thereby obtaining a more homogeneous composite metal oxide. Furthermore, it describes that a gas separation membrane containing the composite metal oxide and one organic chelating agent can permeate He with very high selectivity over N2 or SF6.

[0005] In addition, Non-Patent Documents 1 to 5 describe gas separation membranes made of composite metal oxides containing TiO2 and SiO2 or ZrO2, which are obtained by using one specific organic chelating agent.

[0006] Japanese Patent Application Laid-Open No. 2022-129937

[0007] Toshiya Fukumoto et al., Journal of Membrane Science, 461 (2014), 96-105Yuki Sada et al., Journal of Membrane Science Science, 591 (2019), 117304 Ryosuke Iesako et al., Separation and Purification Technology, 297 (2022), 121458 Shunsuke Kitamura et al., Separation and Purification Technology, 315 (2023), 123576 Etsuko Tachi et al., Separation and Purification Technology, 322 (2023), 124091

[0008] However, even in the gas separation membranes of Patent Document 1 and Non-Patent Documents 1 to 5, it cannot be said that the advantages of two or more metals are maximized, and there is still room for improvement in gas separation ability.

[0009] Therefore, an object of the present disclosure is to provide a gas separation membrane that utilizes the advantages of two or more metals and has superior gas separation ability, and to provide a method for producing such a gas separation membrane.

[0010] As a result of intensive research to achieve the above object, the present inventors have found that by using a composite metal oxide having two or more metals and two or more organic ligands, a gas separation membrane that takes advantage of the advantages of the two or more metals and has superior gas separation ability can be obtained. The present disclosure has been completed based on these findings.

[0011] Specifically, the present disclosure provides a gas separation membrane comprising a composite metal oxide having two or more metals and two or more organic ligands. By incorporating the composite metal oxide having two or more metals, the gas separation membrane takes advantage of the advantages of the two or more metals, and by virtue of the above-described configuration, the gas separation membrane exhibits excellent gas separation ability.

[0012] The two or more metals are preferably two or more selected from the group consisting of metal elements of Group 2, metal elements of Group 3, metal elements of Group 4, metal elements of Group 13, and metal elements of Group 14.

[0013] The composite metal oxide preferably contains Ti and Al and / or Zr, and the molar ratio of the total amount of Al and / or Zr to 1 mole of Ti is preferably 0.01 or more and 100 or less.

[0014] The two or more organic ligands are preferably polydentate ligands.

[0015] The multidentate ligand is preferably one or more selected from the group consisting of dicarbonyl compounds, polyol compounds, and polyol derivatives.

[0016] It is preferable that the composite metal oxide has Ti and Al and / or Zr, the two or more organic ligands are a dicarbonyl compound and a polyol compound, and that the dicarbonyl compound is coordinated to the Ti, and the polyol compound is coordinated to the Al and / or Zr.

[0017] The gas separation membrane preferably has an average pore size of 0.6 nm or less as measured by the normalized Knudsen-based permeance method (NKP method).

[0018] The gas separation membrane includes a structure derived from a composite metal gel containing the two or more metals and the two or more organic ligands, and the composite metal gel has a peak temperature T M The organic ligand exhibits a peak at a peak temperature TL A peak appears at the peak temperature T M and the peak temperature T L Is T M >T L It is preferable to satisfy the following.

[0019] The gas separation membrane preferably has a crystallinity of 20% or less, as represented by the following formula (1): <Method for calculating crystallinity> 100×Ic / (Ic+Ia) formula (1) where Ic is the sum of integrated intensities of diffraction peaks due to crystalline regions in the X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane, and Ia is the sum of integrated intensities of halos due to amorphous regions in the X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane.

[0020] The present disclosure also provides a method for producing a gas separation membrane, comprising the steps of preparing a mixture containing two or more metal compounds and two or more organic ligands, and heating the mixture.

[0021] The step of preparing the mixture preferably comprises a step of mixing each of the metal compounds with one or more of the organic ligands, and then a step of further mixing the mixtures.

[0022] In the above production method, the two or more metal compounds are preferably two or more metal alkoxides.

[0023] In the above production method, the two or more types of metal alkoxides are preferably metal alkoxides formed from two or more types of metals selected from the group consisting of metal elements of Group 2, metal elements of Group 3, metal elements of Group 4, metal elements of Group 13, and metal elements of Group 14.

[0024] In the above production method, the two or more metal alkoxides are a titanium alkoxide and an aluminum alkoxide or a zirconium alkoxide, and the molar ratio of the total amount of the aluminum alkoxide and / or zirconium alkoxide to 1 mole of the titanium alkoxide is preferably 0.01 or more and 100 or less.

[0025] In the above production method, the two or more organic ligands are preferably multidentate ligands.

[0026] In the above production method, the multidentate ligand is preferably at least one selected from the group consisting of dicarbonyl compounds, polyol compounds, and polyol derivatives.

[0027] In the above-mentioned production method, the step of preparing the mixture preferably includes a step of mixing a titanium alkoxide as the metal compound with a dicarbonyl compound as the organic ligand, a step of mixing an aluminum alkoxide and / or a zirconium alkoxide as the metal compound with a polyol compound as the organic ligand, and then a step of further mixing the respective mixtures.

[0028] The gas separation membrane of the present disclosure has excellent gas separation ability. Therefore, for example, it is possible to provide a gas separation membrane that allows permeation of H with extremely high selectivity over CH or CF. Furthermore, the manufacturing method of the gas separation membrane of the present disclosure can provide a gas separation membrane that exhibits excellent gas separation ability.

[0029] FIG. 1 is a schematic diagram of a substrate produced in an example. FIG. 2 is an enlarged schematic diagram of a cross section of a gas separation membrane module produced in an example. FIG. 3 is a diagram showing a TG-DTG curve of a gel produced in an example. FIG. 4 is a diagram showing an X-ray diffraction spectrum of a calcined powder produced in an example. FIG. 5 is a diagram showing a nitrogen adsorption / desorption isotherm of a calcined powder produced in an example. FIG. 6 is a schematic diagram of a gas permeation device used in a gas separation performance evaluation test of a gas separation membrane module produced in an example. FIG. 7 is a diagram showing the results of a gas separation performance evaluation of a gas separation membrane module produced in an example.

[0030] [Gas Separation Membrane] The gas separation membrane of the present disclosure comprises a composite metal oxide having at least two or more metals and two or more organic ligands. In this specification, metalloids that exhibit intermediate properties between metals and non-metals are also referred to as metals. Examples of the metal include metal elements from Groups 1 to 16 of the periodic table. Among these, metal elements from Groups 2, 3, 4, 13, and 14 are preferred, with metal elements from Groups 4, 13, and 14 being more preferred, and metal elements from Groups 4 and 13 being even more preferred. As the metal elements from Group 4, Ti and Zr are preferred, with Ti being more preferred. As the metal elements from Group 13, B, Al, and Ga are preferred, with Al being more preferred. As the metal elements from Group 14, C, Si, and Ge are preferred, with Si being more preferred. When the metal is one of the above, the gas separation membrane of the present disclosure can have better gas separation ability, chemical stability, thermal stability, mechanical strength, and the like.

[0031] The combination of two or more metals preferably contains at least Ti. Also preferably, it contains Al and / or Zr. More preferably, it contains Ti, Al and / or Zr. Even more preferably, it contains Ti and Al. This is because Ti is excellent in terms of high hydrothermal stability and chemical stability, Al is excellent in terms of high mechanical strength and ease of forming a porous membrane, and Zr is excellent in terms of high chemical stability and mechanical strength. By containing two or more metals, the gas separation membrane of the present disclosure can utilize the advantages of each metal and achieve even better gas separation ability.

[0032] The composite metal oxide preferably has a site where two or more kinds of metal atoms are bonded to each other via oxygen atoms, and more preferably, the proportion of different kinds of metal atoms bonded to each other via oxygen atoms is higher than the proportion of the same kind of metal atoms bonded to each other via oxygen atoms. 1 , the second metal is M 2 In this case, the composite metal oxide is preferably -M 1 -O-M 1 -, -M 1 -O-M 2 -, -M2 -O-M 1 -, and -M 2 -O-M 2 - (in the formula, M 1 and M 2 has three or more bonds, the bonds are omitted. 1 -O-M 2 - and - M 2 -O-M 1 The proportion of bonds represented by - is -M 1 -O-M 1 - and - M 2 -O-M 2 - is higher than the proportion of bonds represented by . Furthermore, the above composite metal oxide preferably has a structure in which different metal atoms are bonded to each other via oxygen atoms in at least a portion of the surface through which gas molecules pass, and more preferably has a structure in which different metal atoms are bonded to each other via oxygen atoms over the entire surface through which gas molecules pass. When such a structure is present, the composite metal oxide tends to have fewer crystalline regions and more amorphous regions, resulting in better gas separation ability. This is thought to be because when there are more amorphous regions, there are fewer metal grain boundaries (boundaries between metal particles) large enough to allow various gas molecules to pass through.

[0033] The ratio of the two or more metals contained in the composite metal oxide can be adjusted appropriately depending on the characteristics of each metal. For example, when the composite metal oxide contains a certain metal and other metals, the molar ratio of the other metals to 1 mole of the certain metal is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and particularly preferably 0.2 or more. Furthermore, the molar ratio of the other metals to 1 mole of the certain metal is preferably 100 or less, more preferably 20 or less, even more preferably 10 or less, and particularly preferably 5 or less. When the molar ratio of the other metals to 1 mole of the certain metal is within the above range, a more homogeneous gas separation membrane can be produced. In this specification, "other metals" refers to metals different from the "certain metal." When there are two or more "other metals," the "molar ratio of the other metals" refers to the molar ratio of the total amount of the other metals to 1 mole of the certain metal (total number of moles of other metals / 1 mole of the certain metal).

[0034] The "certain metal" is preferably any one of Ti, Al, and Zr, more preferably Ti. The "other metal" is preferably one or more selected from the group consisting of Ti, Al, and Zr, more preferably Al and / or Zr, and even more preferably Al. Furthermore, the combination of the "certain metal" and the "other metal" is preferably Ti and Al and / or Zr, more preferably Ti and Al.

[0035] The number of types of metals is not particularly limited, but is preferably 5 or less, more preferably 3 or less, and even more preferably 2. When the number of types of metals is within the above range, a gas separation membrane that takes advantage of the advantages of multiple metals can be obtained, and production costs can be reduced.

[0036] The organic ligand contained in the gas separation membrane of the present disclosure is preferably a multidentate ligand. Generally, metals can be coordinated at two or more positions, so that the metal contained in the composite metal oxide is sufficiently coordinated by the multidentate ligand, thereby stably maintaining the amorphous region of the composite metal oxide even in the heating step described below. As a result, the gas separation ability of the gas separation membrane of the present disclosure can be improved.

[0037] The molecular weight of the organic ligand can be adjusted appropriately depending on the size of the gas molecules to be separated. For example, when selective permeation of small gas molecules such as H is desired, the organic ligand is preferably a low-molecular-weight organic ligand, and its molecular weight is, for example, preferably 1,000 or less, more preferably 800 or less, even more preferably 500 or less, still more preferably 400 or less, still more preferably 300 or less, still more preferably 200 or less, and particularly preferably 150 or less. By using such a low-molecular-weight organic ligand, the average pore size of the gas separation membrane can be controlled to be smaller.

[0038] Examples of the organic ligand include dicarbonyl compounds, polyol compounds, and polyol derivatives. These compounds are preferred because they are multidentate ligands and can stably coordinate to metals. Furthermore, the above descriptions regarding the molecular weight of organic ligands can be used to directly refer to the molecular weights of the dicarbonyl compounds, polyol compounds, and polyol derivatives listed above.

[0039] Examples of the dicarbonyl compound include 1,2-dicarbonyl compounds, 1,3-dicarbonyl compounds, 1,4-dicarbonyl compounds, etc. Among these, 1,3-dicarbonyl compounds are preferred because of their ease of coordination to metal atoms. Examples of the 1,3-dicarbonyl compound include 1,3-diketone compounds such as acetylacetone, 6-methyl-2,4-heptanedione, 2,6-dimethyl-3,5-heptanedione, 3-methyl-2,4-pentanedione, 3,5-heptanedione, 1-phenyl-1,3-butanedione, 1,3-cyclopentanedione, and 1,3-cyclohexanedione; 1,3-ketoester compounds such as ethyl acetoacetate, ethyl 2-methylacetoacetate, propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, sec-butyl acetoacetate, isobutyl acetoacetate, tert-butyl acetoacetate, ethyl 3-oxopentanoate, ethyl 3-oxohexanoate, and ethyl 2-ethylacetoacetate; and 1,3-diester compounds such as dimethyl malonate, dimethyl methylmalonate, diethyl malonate, dipropyl malonate, tert-butylethyl malonate, and diisopropyl malonate. Among these, when it is desired to selectively allow small gas molecules such as H2 to permeate, acetylacetone, 6-methyl-2,4-heptanedione, 2,6-dimethyl-3,5-heptanedione, and ethyl acetoacetate are preferred, with acetylacetone being more preferred.

[0040] Examples of the polyol compound include aliphatic polyol compounds and aromatic polyol compounds. Polyalkanolamines are preferred as the aliphatic polyol compound. Examples of the polyalkanolamine include dialkanolamines and trialkanolamines. Of these, dialkanolamines are preferred. Examples of the dialkanolamine include diethanolamine, N-methyldiethanolamine, diisopropanolamine, and N-ethyldiethanolamine. Among these, when selective permeation of small gas molecules such as H2 is desired, diethanolamine and diisopropanolamine are preferred, and diethanolamine is more preferred. Examples of the trialkanolamine include triethanolamine and triisopropanolamine. Examples of the aromatic polyol compound include aromatic diol compounds and aromatic triol compounds. Examples of the aromatic diol compound include aromatic 1,2-diol compounds and aromatic 1,3-diol compounds. Of these, aromatic 1,2-diol compounds are preferred. Examples of the aromatic 1,2-diol compounds include 1,2-dihydroxybenzene, 3,4-dihydroxybenzaldehyde, 2,3-dihydroxynaphthalene, 1,2-dihydroxynaphthalene, 3,5-di-tert-butylcatechol, 3-methylcatechol, and 4-methylcatechol. Examples of the aromatic triol compounds include aromatic 1,2,3-triol compounds and aromatic 1,2,4-diol compounds. Of these, aromatic 1,2,3-triol compounds are preferred. Examples of the aromatic 1,2,3-diol compounds include gallic acid, methyl gallate, propyl gallate, and isoamyl gallate.

[0041] Examples of the polyol derivatives include aliphatic polyol derivatives and aromatic polyol derivatives. Preferred examples of the aliphatic polyol derivatives include polyalkanolamine derivatives. Examples of the polyalkanolamine derivatives include dialkanolamine derivatives and trialkanolamine derivatives. Among these, dialkanolamine derivatives are preferred. Examples of the dialkanolamine derivatives include bis(2-methoxyethyl)amine and bis(2-ethoxyethyl)amine. Examples of the trialkanolamine derivatives include tris[2-(2-methoxyethoxy)ethyl]amine. Examples of the aromatic polyol derivatives include aromatic diol derivatives and aromatic triol derivatives. Examples of the aromatic diol derivatives include aromatic 1,2-diol derivatives and aromatic 1,3-diol derivatives. Among these, aromatic 1,2-diol derivatives are preferred. Examples of the aromatic 1,2-diol derivatives include 2-methoxyphenol, isoeugenol, and ethyl ferulate. Examples of the aromatic triol derivatives include aromatic 1,2,3-triol derivatives and aromatic 1,2,4-diol derivatives.

[0042] In this specification, a compound having two or more hydroxy groups in the molecule is referred to as a "polyol compound," and a polyol compound in which one or more hydroxy groups have been converted to an alkoxy group, an ester group, or the like is referred to as a "polyol derivative." Furthermore, dicarbonyl compounds, polyol compounds, and polyol derivatives may overlap with one another. However, the dicarbonyl compound is preferably not a polyol compound, and more preferably not a polyol compound or a polyol derivative. Furthermore, the polyol compound is preferably not a dicarbonyl compound, and more preferably not a dicarbonyl compound or a polyol derivative. Furthermore, the polyol derivative is preferably not a dicarbonyl compound, and more preferably not a dicarbonyl compound or a polyol compound.

[0043] In the present disclosure, the organic ligands may be of the same type, either alone or in combination. That is, the gas separation membrane of the present disclosure contains two or more types of organic ligands, and may, for example, contain two or more different dicarbonyl compounds, or may contain one or more dicarbonyl compounds and one or more polyol compounds and / or polyol derivatives.

[0044] The number of types of organic ligands is not particularly limited, but is preferably 5 or less, more preferably 3 or less, and even more preferably 2. When the number of types of organic ligands is within the above range, all of the two or more metals can be stabilized, and the chemical stability, thermal stability, gas separation ability, etc. of the gas separation membrane of the present disclosure can be improved. The number of types of organic ligands may be the same as or different from the number of types of metals.

[0045] The ratio of the total amount of the two or more organic ligands to the total amount of the two or more metals may be appropriately adjusted depending on the characteristics of each metal and / or organic ligand. For example, the molar ratio of the total amount of the two or more organic ligands to 1 mole of the total amount of the two or more metals is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. Furthermore, the molar ratio of the total amount of the two or more organic ligands to 1 mole of the total amount of the two or more metals is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less. When the molar ratio of the total amount of the two or more organic ligands to 1 mole of the total amount of the two or more metals is within the above range, the metals can be sufficiently coordinated, and free organic ligands can be less likely to clog the pores, thereby producing a gas separation membrane that is more homogeneous and has excellent chemical stability, thermal stability, gas separation ability, etc.

[0046] When the composite metal oxide contains Ti as a metal, from the viewpoint of increasing the gas permeability ratio of H to CH, the molar ratio of the one kind of organic ligand to 1 mole of Ti is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. The molar ratio of the one kind of organic ligand to 1 mole of Ti is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, still more preferably 3 or less, even more preferably 2 or less, and particularly preferably 1.8 or less.

[0047] From the viewpoint of increasing the gas permeability ratio of H to CF, the molar ratio of the one kind of organic ligand to 1 mole of Ti is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more, and the molar ratio of the one kind of organic ligand to 1 mole of Ti is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less.

[0048] When the composite metal oxide contains Ti as the metal, the one kind of organic ligand is preferably a dicarbonyl compound, more preferably a 1,3-dicarbonyl compound, and even more preferably a 1,3-diketone compound. Among these, when it is desired to selectively allow small gas molecules such as H to permeate, acetylacetone is particularly preferred.

[0049] When the composite metal oxide contains Al and / or Zr as the metal, from the viewpoint of increasing the gas permeability ratio of H to CH, the molar ratio of the one kind of organic ligand to 1 mole of the total amount of Al and / or Zr is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. The molar ratio of the one kind of organic ligand to 1 mole of the total amount of Al and / or Zr is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less.

[0050] Furthermore, from the viewpoint of increasing the gas permeability ratio of H to CF, the molar ratio of the one kind of organic ligand to 1 mole of the total amount of Al and / or Zr is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. The molar ratio of the one kind of organic ligand to 1 mole of the total amount of Al and / or Zr is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, still more preferably 3 or less, even more preferably 2 or less, and particularly preferably 1.8 or less.

[0051] When the composite metal oxide contains Al and / or Zr as the metal, the one organic ligand is preferably a polyol compound or a polyol derivative, more preferably a polyol compound, even more preferably a polyalkanolamine, and even more preferably a dialkanolamine. Among these, when selective permeation of small gas molecules such as H is desired, diethanolamine is particularly preferred.

[0052] When the above-mentioned composite metal oxide contains Ti and Al and / or Zr as metals, a combination of a dicarbonyl compound and a polyol compound and / or a polyol derivative is preferred as the organic ligand. A combination of a dicarbonyl compound and a polyol compound is more preferred. A combination of a 1,3-dicarbonyl compound and a dialkanolamine is even more preferred. In such a combination, the dicarbonyl compound can be coordinated to Ti, and the polyol compound can be coordinated to Al and / or Zr, allowing each metal to be more fully coordinated.

[0053] Due to the above-described configuration, the gas separation membrane of the present disclosure contains few crystalline regions and many amorphous regions. Therefore, the gas separation membrane has few metal grain boundaries and very fine pores, resulting in superior gas separation ability. These pores are interconnected pores, i.e., pores that penetrate from one surface (front surface) of the gas separation membrane to the opposite surface (back surface), allowing gas molecules smaller than the pore size to pass through. The average pore size of the pores can be adjusted appropriately depending on the size of the gas molecules to be separated. For example, when selectively allowing small gas molecules such as H2 to pass through, the average pore size measured by the normalized Knudsen-based permeance method (NKP method) is preferably 0.6 nm or less, more preferably 0.58 nm or less, and even more preferably 0.55 nm or less. Furthermore, the average pore size measured by the NKP method is preferably 0.1 nm or more, more preferably 0.2 nm or more, and even more preferably 0.3 nm or more. The "NKP method" is a method for evaluating sub-nano-sized pore diameters by utilizing the phenomenon that the permeability of gas molecules passing through a gas separation membrane deviates from the Knudsen diffusion based on the mass of the molecule due to the influence of the size of the gas molecules. Generally, the gas permeability (unit: mol / (m)) of gases such as He, H2, CO2, N2, and SF6 is measured. 2 s Pa)), calculate NKP from the measured values, and calculate the diameter d of each molecule i The NKP value is plotted against the molecular size d when the NKP value becomes zero. p can be determined as the average pore diameter.

[0054] The gas separation membrane of the present disclosure has fine pores as described above, and therefore is considered to have a large surface area. The surface area is not particularly limited, but a larger surface area is preferable because it allows for more pores to be present.

[0055] The gas separation membrane of the present disclosure is believed to have two or more organic ligands coordinated to two or more metals, forming coordinate bonds between the metals and the organic ligands. The membrane may exhibit unusual behavior in thermal analysis techniques that is believed to be due to the coordinate bonds. Examples of thermal analysis techniques include thermogravimetric analysis (TGA) and thermogravimetric differential thermal analysis (TG-DTA). Thermogravimetric analysis is an analytical method in which a sample and a reference material are heated while measuring the weight change of the sample. Thermogravimetric differential thermal analysis is an analytical method in which a sample and a reference material are heated while simultaneously measuring the weight change of the sample and the temperature difference (differential heating) between the sample and the reference material. A weight loss curve (TG) is obtained by either the thermogravimetric analysis or the thermogravimetric differential thermal analysis, and a derivative thermogravimetric curve (DTG) is obtained by differentiating the weight loss curve (TG) with respect to time. From the weight loss curve (TG) and the derivative thermogravimetric curve (DTG), the state of weight change due to thermal decomposition of the sample can be observed. For example, when a peak appears in the derivative thermogravimetric curve (DTG), the temperature at the top of the peak (peak temperature) means the temperature at which the weight change rate is maximum.

[0056] Specifically, the gas separation membrane of the present disclosure includes a structure derived from a composite metal gel containing two or more types of metals and two or more types of organic ligands, and the composite metal gel (the manufacturing method and the like will be described later) has a peak temperature T M The organic ligand exhibits a peak at a peak temperature T L A peak appears at the peak temperature T M and the peak temperature T L Is T M >T L It is preferable that the peak temperature T M and / or the peak temperature T LIt is more preferable that the peaks are all peaks accompanied by weight loss, and M and the peak temperature T L It is more preferable that all of the peaks are peaks accompanied by a weight loss. The composite metal gel and the organic ligand may exhibit multiple peaks in the differential thermogravimetric curve (DTG). In this specification, when the organic ligand exhibits two or more peaks in the differential thermogravimetric curve (DTG), the peak temperature of the peak that appears at the highest temperature is defined as the T of the organic ligand. L Therefore, the two or more organic ligands each have a unique T L The composite metal gel has a peak temperature T M The peak temperature T of at least one of the two or more organic ligands L In contrast, T M >T L It is preferable that the peak temperature T M is the peak temperature T L In contrast, T M >T L It is more preferable that the following conditions are satisfied.

[0057] Generally, when a thermogravimetric differential thermal analysis is performed on an organic ligand alone, a peak specific to the organic ligand may appear in the resulting differential thermogravimetric curve (DTG). For example, when the thermogravimetric differential thermal analysis is performed under a nitrogen atmosphere, the peak specific to the organic ligand is thought to be due to thermal decomposition of the organic ligand. Since the organic ligand becomes more stable by being coordinated to a metal, it will thermally decompose in a higher temperature range than when it exists alone. In other words, the peak temperature of the peak that appears in the differential thermogravimetric curve (DTG) when the organic ligand is coordinated to a metal (coordinated state) is higher than the peak temperature of the peak that appears in the differential thermogravimetric curve (DTG) obtained when the thermogravimetric differential thermal analysis is performed in a free state where the organic ligand is not coordinated to a metal. Therefore, the peak temperature T M and a peak temperature T of at least one of the two or more organic ligands.L But, T M >T L is satisfied, it is believed that this strongly suggests that a coordinate bond is formed between the metal and the organic ligand contained in the gas separation membrane of the present disclosure.

[0058] The gas separation membrane of the present disclosure also includes a structure derived from a composite metal gel containing two or more metals and two or more organic ligands, and the composite metal gel preferably exhibits peaks in a temperature range of 130°C to less than 250°C and / or 250°C or higher in a differential thermogravimetric curve (DTG) obtained by thermogravimetric differential thermal analysis, and more preferably exhibits peaks in a temperature range of 130°C to less than 250°C and 250°C or higher. It is even more preferable that all of the peaks are accompanied by weight loss. This is because, in the differential thermogravimetric curve (DTG) obtained when the below-described thermogravimetric differential thermal analysis is performed on DEA and ACA as the organic ligands, in the case of DEA, the peak temperature T L(DEA) is about 230°C, and in the case of ACA, the peak temperature T L(ACA) is about 120°C.

[0059] The gas separation membrane of the present disclosure contains many amorphous regions and therefore may exhibit unique behavior in crystallographic analysis techniques such as X-ray diffraction (XRD) analysis.

[0060] The gas separation membrane of the present disclosure preferably exhibits a broad halo due to amorphous regions when subjected to XRD analysis. When the gas separation membrane of the present disclosure contains Ti and / or Al as the metal, the position of the broad halo due to the amorphous regions differs from the position of the diffraction peaks due to crystalline TiO2 and / or Al2O3, and preferably appears, for example, in at least one of the ranges of 2θ = 10 to 14°, 18 to 22°, and 26 to 30°. Note that the gas separation membrane of the present disclosure may contain crystalline regions, and therefore may exhibit diffraction peaks due to the crystalline regions.

[0061] The gas separation membrane of the present disclosure preferably has a crystallinity of 20% or less, expressed as 100 × Ic / (Ic + Ia). Ic is the sum of the integrated intensities of diffraction peaks due to crystalline regions in the spectrum obtained by XRD analysis of the gas separation membrane of the present disclosure, and Ia is the sum of the integrated intensities of halos due to amorphous regions in the spectrum obtained by XRD analysis of the gas separation membrane of the present disclosure. The crystallinity of the gas separation membrane of the present disclosure can be determined by XRD analysis under the conditions described below.

[0062] The gas separation membrane of the present disclosure may have a single layer structure or a laminate structure consisting of two or more layers. When the gas separation membrane of the present disclosure has a laminate structure, the two or more layers in the gas separation membrane of the present disclosure may have the same composition or different compositions. The gas separation membrane of the present disclosure may also include other layers or may be used laminated with other layers. In this case, the gas separation membrane of the present disclosure may have a laminate structure in which the two or more layers are laminated via other layers. Examples of the other layers include other gas separation membranes, particle layers, etc. The other layers may be a single layer or multiple layers. A gas separation membrane module including the other layers, etc., can be obtained using the gas separation membrane of the present disclosure.

[0063] The other gas separation membrane is a layer different from the gas separation membrane of the present disclosure, and functions, for example, as a layer that can further improve gas permeability and / or a layer that can impart mechanical strength to the gas separation membrane module. The structure of the other gas separation membrane preferably includes a composite metal oxide having two or more metals, more preferably a composite metal oxide having two or more metals and one organic ligand. Examples of metals contained in the other gas separation membrane include metal elements from Groups 1 to 16 of the periodic table. Among these, metal elements from Groups 2, 3, 4, 13, and 14 are preferred, with metal elements from Groups 4, 13, and 14 being more preferred. Preferred metal elements from Group 4 are Ti and Zr. Preferred metal elements from Group 13 are B, Al, and Ga, with Al being more preferred. Preferred metal elements from Group 14 are C, Si, and Ge, with Si being more preferred.

[0064] The combination of two or more metals contained in the other gas separation membrane preferably contains at least Ti. Also preferably, it contains Si and / or Zr. More preferably, it contains Ti, Si and / or Zr. This is because Ti is excellent in terms of high hydrothermal stability and chemical stability, Si is excellent in terms of high permeability selectivity and ease of forming a porous membrane, and Zr is excellent in terms of high chemical stability and mechanical strength. By including the above metals in the other gas separation membrane, the chemical stability, thermal stability, mechanical strength, etc. of the gas separation membrane module can be improved.

[0065] The organic ligands contained in the other gas separation membranes may be any of the organic ligands contained in the gas separation membranes of the present disclosure. When the other gas separation membranes have the organic ligands, the chemical stability, thermal stability, gas separation ability, and the like of the gas separation membrane module can be improved.

[0066] The pore size of the above-mentioned other gas separation membranes is not particularly limited. For example, the average pore diameter measured by nanoperm porometry is preferably 0.5 nm to 50 nm, more preferably 0.5 nm to 20 nm, even more preferably 0.5 nm to 10 nm, and particularly preferably 0.5 nm to 5 nm. Nanoperm porometry is a standard method for measuring pore diameters of approximately 0.5 to 50 nm, and is a technique for measuring the average pore diameter by utilizing capillary condensation of condensed gas when condensed gas and non-condensed gas are simultaneously supplied to the pores. In this case, the contact angle θ was assumed to be complete wetting (θ = 0). In this specification, HO was used as the condensed gas and N was used as the non-condensed gas.

[0067] The particle layer is a layer that does not fall under the gas separation membrane of the present disclosure and includes a frit. The particle layer functions as a layer that maintains gas permeability and can impart mechanical strength to the gas separation membrane module. The particle layer preferably includes a composite metal oxide having two or more metals, more preferably a composite metal oxide having two or more metals and one organic ligand. Examples of metals included in the particle layer include metal elements of Groups 1 to 16 of the periodic table. Among these, metal elements of Groups 2, 3, 4, 13, and 14 are preferred, with metal elements of Groups 4, 13, and 14 being more preferred. As the metal elements of Group 4, Ti and Zr are preferred. As the metal elements of Group 13, B, Al, and Ga are preferred, with Al being more preferred. As the metal elements of Group 14, C, Si, and Ge are preferred, with Si being more preferred.

[0068] The combination of two or more metals contained in the particle layer preferably contains at least Ti. Also, preferably, it contains Si and / or Zr. More preferably, it contains Ti, Si and / or Zr. Even more preferably, it contains Ti and Si. This is because Ti is excellent in terms of high hydrothermal stability and chemical stability, Si is excellent in terms of high permselectivity and ease of forming a porous membrane, and Zr is excellent in terms of high chemical stability and mechanical strength. By including these metals in the particle layer, the chemical stability, thermal stability, mechanical strength, etc. of the gas separation membrane module can be improved.

[0069] The organic ligand contained in the particle layer may be any of the organic ligands contained in the gas separation membrane of the present disclosure. By including the organic ligand in the particle layer, the chemical stability, thermal stability, gas separation ability, and the like of the gas separation membrane module may be improved.

[0070] Here, the frit is different from the composite metal oxide contained in the gas separation membrane of the present disclosure, and is, for example, crystalline fine particles. Examples of materials for this frit include alumina, silica, cordierite, zirconia, titania, magnesia, zeolite, Vycor glass, and sintered metal. Examples of the average particle size of the frit include 0.1 μm to 5 μm. By using such a frit, the pores of the particle layer can be adjusted to a pore size relatively larger than the pores of the gas separation membrane of the present disclosure and other gas separation membranes, and the mechanical strength of the gas separation membrane can be improved. The above frits can be used alone or in combination of two or more types.

[0071] The size of the pores in the particle layer is not particularly limited, but the average pore diameter measured by the bubble point method is preferably 100 nm to 1 μm.

[0072] The gas separation membrane module may include components other than the layers described above. Examples of such components include a substrate that functions as a support, and examples of such substrates include porous and non-porous materials. Examples of materials for the substrate include alumina, silica, cordierite, zirconia, titania, magnesia, zeolite, Vycor glass, and sintered metal. The substrates may be used alone or in combination of two or more.

[0073] When a non-porous body is used as the substrate, it functions as a support when the gas separation membrane is produced and handled by connecting it to the gas separation membrane so as not to block the pores of the gas separation membrane.

[0074] When a porous body is used as the substrate, the gas separation membrane is formed directly on the surface of the porous body, which functions as a support that provides mechanical strength to the gas separation membrane without blocking the communicating pores. The gas separation membrane may or may not be in contact with the porous body. The average pore size of the porous body is, for example, preferably 1 nm to 50 μm, more preferably 50 nm to 40 μm, even more preferably 100 nm to 30 μm, even more preferably 500 nm to 20 μm, and particularly preferably 1 μm to 10 μm. When the average pore size of the porous body is within the above range, sufficient permeability to gas molecules can be ensured, and the gas separation membrane of the present disclosure or other gas separation membranes can be favorably formed on the surface of the porous body.

[0075] Examples of the structure of the substrate include a hollow tube, a flat membrane, and hollow particles, with a hollow tube being preferred. The outer diameter of the hollow tube is, for example, preferably 1 mm to 50 cm, more preferably 2 mm to 30 cm, even more preferably 5 mm to 15 cm, and particularly preferably 5 mm to 15 mm. When the outer diameter of the substrate is within the above range, the pressure loss of the permeating gas is small, thereby sufficiently reducing energy consumption and reducing the production cost of the gas separation membrane module.

[0076] The thickness of each layer of the gas separation membrane of the present disclosure and the total thickness of the gas separation membrane of the present disclosure are not particularly limited. The thickness of each layer of the gas separation membrane of the present disclosure is, for example, preferably 1 nm to 20 μm, more preferably 2 nm to 10 μm, even more preferably 3 nm to 7 μm, and particularly preferably 5 nm to 5 μm. The total thickness of the gas separation membrane of the present disclosure is, for example, preferably 1 nm to 50 μm, more preferably 5 nm to 10 μm.

[0077] The thickness of each layer of the other gas separation membrane and the total thickness of the other gas separation membrane are not particularly limited. The thickness of each layer of the other gas separation membrane is preferably, for example, 10 nm to 200 μm. The total thickness of the other gas separation membrane is preferably, for example, 10 nm to 500 μm.

[0078] The thickness of each layer of the particle layer and the total thickness of the particle layer are not particularly limited. The thickness of each layer of the particle layer is preferably, for example, 10 nm to 200 μm. The total thickness of the particle layer is preferably, for example, 10 nm to 500 μm.

[0079] The gas separation membrane of the present disclosure exhibits excellent gas separation ability by having the above-mentioned configuration. Specifically, for example, when a gas separation ability evaluation test described below is performed, the gas permeability ratio of H to CH (gas permeability of H / gas permeability of CH) is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. Furthermore, the gas permeability ratio of H to CF (gas permeability of H / gas permeability of CF) is preferably 40 or more, more preferably 50 or more, even more preferably 100 or more, even more preferably 200 or more, and particularly preferably 250 or more.

[0080] The gas separation membrane of the present disclosure may contain other components in addition to two or more metals and two or more organic ligands. Examples of other components include catalysts, solvents, water, surfactants, polymers, etc. The content of the other components is not particularly limited, but is, for example, preferably 0% to 50% by mass, more preferably 0% to 40% by mass, even more preferably 0% to 30% by mass, even more preferably 0% to 20% by mass, even more preferably 0% to 10% by mass, and particularly preferably 0% to 5% by mass, relative to 100% by mass of the gas separation membrane of the present disclosure. Furthermore, the gas separation membrane of the present disclosure may be substantially free of other components.

[0081] [Method for producing gas separation membrane] The method for producing a gas separation membrane of the present disclosure includes a step of preparing a mixture containing two or more metal compounds and two or more organic ligands (mixing step), and a step of heating the mixture (heating step). In this specification, the method for producing a gas separation membrane of the present disclosure may be simply referred to as the "production method of the present disclosure." In addition to the mixing step and the heating step, the production method of the present disclosure may also include other steps such as a drying step.

[0082] (Mixing step) In the mixing step, two or more metal compounds and two or more organic ligands are mixed to produce a composite metal oxide in which two or more organic ligands form coordinate bonds with two or more metals. In the mixing step, components other than the metal compounds and organic ligands may be used. Examples of the other components include a catalyst, a solvent, and water.

[0083] The metal compound used in the mixing step is not particularly limited, but it is preferable to use two or more metal alkoxides that can prepare a composite metal oxide by a sol-gel method. Generally, metal alkoxides are compounds represented by M(OR)n (where M represents a metal, R represents a substituent, and n represents the valence of M). For example, when the metal is Ti, Zr, or Si, n is 4, and when the metal is Al, n is 3. Examples of the substituent include alkyl groups having 1 to 5 carbon atoms. Of these, alkyl groups having 3 to 4 carbon atoms are preferred, with n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl being more preferred. In the case of metal alkoxides having such substituents, it becomes easier to adjust the hydrolysis rate in the sol-gel method.

[0084] Examples of the metal alkoxide include metal alkoxides formed from any of the metal elements of Groups 1 to 16 of the periodic table. Among these, metal alkoxides formed from any of the metal elements of Groups 2, 3, 4, 13, and 14 are preferred, metal alkoxides formed from any of the metal elements of Groups 4, 13, and 14 are more preferred, and metal alkoxides formed from any of the metal elements of Groups 4 and 13 are even more preferred. As the metal alkoxides formed from any of the metal elements of Group 4, titanium alkoxides and zirconium alkoxides are preferred, with titanium alkoxide being more preferred. As the metal alkoxides formed from any of the metal elements of Group 13, boron alkoxides and aluminum alkoxides are preferred, with aluminum alkoxide being more preferred. As the metal alkoxides formed from any of the metal elements of Group 14, silane alkoxides are preferred. By using the above metal alkoxide, the gas separation membrane of the present disclosure can be made more excellent in gas separation ability, chemical stability, thermal stability, mechanical strength, and the like.

[0085] The combination of two or more metal alkoxides preferably contains at least titanium alkoxide. Also, preferably, aluminum alkoxide and / or zirconium alkoxide are included. More preferably, titanium alkoxide and aluminum alkoxide and / or zirconium alkoxide are included. Even more preferably, titanium alkoxide and aluminum alkoxide are included. This is because Ti is excellent in terms of high hydrothermal stability and chemical stability, Al is excellent in terms of high mechanical strength and ease of forming a porous membrane, and Zr is excellent in terms of high chemical stability and mechanical strength. By using the two or more metal alkoxides, the production method of the present disclosure can utilize the advantages of each metal to provide a gas separation membrane with superior gas separation ability.

[0086] Generally, the hydrolysis rate of a metal alkoxide increases as the number of carbon atoms in the alkyl group substituent decreases, and as the alkyl group substituent has a branched structure. That is, the hydrolysis rate of a metal alkoxide having a primary alkyl group as a substituent is slower, while the hydrolysis rate of a metal alkoxide having a tertiary alkyl group as a substituent is faster. When two or more metal alkoxides are used, the hydrolysis rate varies depending on the type of metal. Therefore, to obtain a more homogeneous gas separation membrane with more amorphous regions, it is preferable to adjust the size of the substituent appropriately to make the hydrolysis rates of the two or more metal alkoxides uniform. Since the hydrolysis rate of titanium alkoxides is faster than that of aluminum alkoxides, it is preferable to select an aluminum alkoxide with a faster hydrolysis rate and a titanium alkoxide with a slower hydrolysis rate. Furthermore, organic ligands can function similarly to the above-mentioned substituents. It is believed that organic ligands can inhibit hydrolysis by coordinating with vacant coordination sites of the metal alkoxide.

[0087] Examples of the titanium alkoxide include titanium(IV) n-propoxide, titanium(IV) isopropoxide, titanium(IV) n-butoxide, titanium(IV) isobutoxide, titanium(IV) tert-butoxide, titanium(IV) methoxide, and titanium(IV) ethoxide, and among these, titanium(IV) n-propoxide is preferred. The titanium alkoxides can be used alone or in combination of two or more.

[0088] Examples of the aluminum alkoxide include aluminum sec-butoxide, aluminum tert-butoxide, aluminum isopropoxide, and aluminum ethoxide, with aluminum sec-butoxide being preferred. The aluminum alkoxides can be used alone or in combination of two or more. A preferred combination of two or more metal alkoxides is titanium(IV) n-propoxide and aluminum sec-butoxide.

[0089] The ratio of the two or more metal compounds used in the mixing step can be adjusted appropriately depending on the characteristics of each metal compound. For example, the molar ratio of the other metal compounds to 1 mole of a certain metal compound is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and particularly preferably 0.2 or more. Furthermore, the molar ratio of the other metal compounds to 1 mole of a certain metal compound is preferably 100 or less, more preferably 20 or less, even more preferably 10 or less, and particularly preferably 5 or less. When the molar ratio of the other metal compounds to 1 mole of a certain metal compound is within the above range, the advantages of each metal can be utilized. In this specification, the term "other metal compound" refers to a metal compound different from the "certain metal compound." When there are two or more "other metal compounds," the "molar ratio of the other metal compounds" refers to the molar ratio of the total amount of the other metal compounds to 1 mole of the certain metal compound (total number of moles of the other metal compounds / 1 mole of the certain metal compound).

[0090] The "certain one metal compound" is preferably a metal alkoxide. Among these, any one of titanium alkoxide, aluminum alkoxide, and zirconium alkoxide is preferred, with titanium alkoxide being more preferred. The "other metal compound" is preferably a metal alkoxide. Among these, it is preferably one or more selected from the group consisting of titanium alkoxide, aluminum alkoxide, and zirconium alkoxide, with aluminum alkoxide and / or zirconium alkoxide being more preferred, and aluminum alkoxide being even more preferred. Furthermore, the combination of the "certain one metal compound" and the "other metal compound" is preferably titanium alkoxide and aluminum alkoxide and / or zirconium alkoxide, with titanium alkoxide and aluminum alkoxide being more preferred.

[0091] The number of types of the two or more metal compounds used in the mixing step is, for example, preferably 5 or less, more preferably 3 or less, and even more preferably 2. When the number of types of metal compounds is within the above range, a gas separation membrane that takes advantage of the advantages of multiple metals can be obtained, and production costs can be reduced.

[0092] The organic ligand used in the mixing step is not particularly limited, and all of the contents described in the section [Gas Separation Membrane] can be applied.

[0093] The ratio of the total amount of the two or more organic ligands to the total amount of the two or more metal compounds used in the mixing step may be appropriately adjusted depending on the properties of each metal compound and / or organic ligand. For example, the molar ratio of the total amount of the two or more organic ligands to 1 mole of the total amount of the two or more metal compounds is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. Furthermore, the molar ratio of the total amount of the two or more organic ligands to 1 mole of the total amount of the two or more metal compounds is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less. When the molar ratio of the total amount of the two or more organic ligands to 1 mole of the total amount of the two or more metal compounds is within the above range, the metals can be sufficiently coordinated, and free organic ligands can be less likely to clog the pores, thereby producing a gas separation membrane that is more homogeneous and has excellent chemical stability, thermal stability, gas separation ability, etc.

[0094] When titanium alkoxide is used as the metal compound, from the viewpoint of increasing the gas permeability ratio of H to CH, the molar ratio of the one kind of organic ligand to 1 mole of titanium alkoxide is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. The molar ratio of the one kind of organic ligand to 1 mole of titanium alkoxide is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, still more preferably 3 or less, still more preferably 2 or less, and particularly preferably 1.8 or less.

[0095] Furthermore, from the viewpoint of increasing the gas permeation ratio of H to CF, the molar ratio of the one kind of organic ligand to 1 mole of titanium alkoxide is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, still more preferably 0.8 or more, and particularly preferably 1.5 or more. The molar ratio of the one kind of organic ligand to 1 mole of titanium alkoxide is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less.

[0096] When titanium alkoxide is used as the metal compound, the organic ligand is preferably a dicarbonyl compound, more preferably a 1,3-dicarbonyl compound, and even more preferably a 1,3-diketone compound. Among these, acetylacetone is particularly preferred when it is desired to selectively allow small gas molecules such as H to permeate.

[0097] When an aluminum alkoxide and / or a zirconium alkoxide is used as the metal compound, from the viewpoint of increasing the gas permeability ratio of H to CH, the molar ratio of the one kind of organic ligand to 1 mole of the aluminum alkoxide and / or the zirconium alkoxide is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, still more preferably 0.8 or more, and particularly preferably 1.5 or more. The molar ratio of the one kind of organic ligand to 1 mole of the aluminum alkoxide and / or the zirconium alkoxide is preferably 20 or less, more preferably 10 or less, still more preferably 5 or less, and particularly preferably 3 or less.

[0098] Furthermore, from the viewpoint of increasing the gas permeation ratio of H to CF, the molar ratio of the one kind of organic ligand to 1 mole of aluminum alkoxide and / or zirconium alkoxide is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and particularly preferably 0.8 or more. The molar ratio of the one kind of organic ligand to 1 mole of aluminum alkoxide and / or zirconium alkoxide is preferably 20 or less, more preferably 10 or less, even more preferably 5 or less, still more preferably 3 or less, even more preferably 2 or less, and particularly preferably 1.8 or less.

[0099] When aluminum alkoxide and / or zirconium alkoxide is used as the metal compound, the organic ligand is preferably a polyol compound and / or a polyol derivative, more preferably a polyol compound, further preferably a polyalkanolamine, and even more preferably a dialkanolamine. Among these, when selective permeation of small gas molecules such as H is desired, diethanolamine is particularly preferred.

[0100] When titanium alkoxide and aluminum alkoxide and / or zirconium alkoxide are used as the metal compounds, it is preferable to use a dicarbonyl compound and a polyol compound and / or a polyol derivative as the organic ligand. It is more preferable to use a dicarbonyl compound and a polyol compound. It is even more preferable to use a 1,3-dicarbonyl compound and a dialkanolamine. In such a combination, the dicarbonyl compound can be coordinated to Ti, and the polyol compound can be coordinated to Al and / or Zr, allowing each metal to be more fully coordinated.

[0101] In the production method of the present disclosure, a composite metal oxide is produced by mixing two or more metal compounds with two or more organic ligands. While the reaction method is not particularly limited, it is preferable to produce the composite metal oxide by a sol-gel method in order to obtain a homogeneous amorphous region. The sol-gel method generally involves hydrolyzing a metal alkoxide and condensation-polymerizing it to produce a fluid metal oxide (metal sol), which is then further condensed or distilled off the solvent and / or water to produce a non-fluid metal oxide (metal gel). The production method of the present disclosure can produce a composite metal oxide in which two or more metals are bonded via oxygen by applying the sol-gel method using two or more metal compounds.

[0102] A catalyst can be used in the mixing step. The type of catalyst is not particularly limited, but one that can promote the hydrolysis reaction and condensation polymerization reaction of the metal alkoxide is preferred, and examples thereof include inorganic acids such as hydrogen chloride, hydrogen bromide, phosphoric acid, and nitric acid, and organic acids such as trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid. Among these, inorganic acids are preferred, and hydrogen chloride is more preferred. The above catalysts can be used alone or in combination of two or more.

[0103] The amount of catalyst used may be adjusted as appropriate within a range that sufficiently promotes the hydrolysis reaction and condensation polymerization reaction of the metal alkoxide. For example, the amount of catalyst used relative to 100 mol% of the metal alkoxide is preferably 0.1 mol% to 200 mol%, more preferably 20 mol% to 180 mol%, even more preferably 50 mol% to 170 mol%, and particularly preferably 80 mol% to 150 mol%.

[0104] The mixing step can be carried out in the presence of a solvent. The type of solvent is not particularly limited, and a solvent capable of producing a homogeneous, fluid composite metal oxide (composite metal sol) is preferred. Examples include alcohols such as absolute ethanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, sec-butanol, and tert-butanol; alkoxymethanols such as methoxymethanol and ethoxymethanol; alkoxyethanols such as 2-methoxyethanol and 2-ethoxyethanol; alkoxypropanols such as 1-methoxy-2-propanol; and alkoxybutanols such as 3-methoxy-1-butanol. Of these, absolute ethanol is preferred because it can produce a homogeneous composite metal sol and precisely control the water content, as described below. The above solvents can be used alone or in combination of two or more.

[0105] The amount of solvent used may be adjusted as appropriate within a range that allows the production of a homogeneous composite metal sol. For example, the amount of solvent used relative to 100% by mass of all components (including the solvent) used in the mixing step is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0106] In the mixing step, for example, when the reaction method is a sol-gel method, water can be used to promote the hydrolysis of the metal alkoxide, and the amount of water used can be appropriately adjusted depending on the reactivity of the metal alkoxide, the molecular weight of the target sol, etc. For example, the molar ratio of water to 1 mole of the total amount of two or more metal alkoxides is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.3 or more, even more preferably 0.5 or more, even more preferably 0.7 or more, even more preferably 1 or more, even more preferably 2 or more, and particularly preferably 3 or more. Furthermore, the molar ratio of water to 1 mole of the total amount of two or more metal alkoxides is preferably 500 or less, more preferably 400 or less, even more preferably 300 or less, even more preferably 200 or less, even more preferably 100 or less, even more preferably 50 or less, even more preferably 30 or less, even more preferably 20 or less, and particularly preferably 10 or less. When the molar ratio of water to 1 mole of the total amount of two or more metal alkoxides is within the above range, the hydrolysis and polycondensation of the two or more metal alkoxides proceeds appropriately, and a more homogeneous composite metal sol can be produced.

[0107] In the mixing step, two or more metal compounds and two or more organic ligands are mixed to produce a composite metal oxide in which two or more organic ligands are coordinated to each metal. The mixing method in the mixing step is not particularly limited. For example, two or more metal compounds and two or more organic ligands may be mixed together, or one of the components may be added later and then mixed. Alternatively, each metal compound may be mixed with one or more organic ligands, and then the resulting mixtures may be further mixed. Specifically, when mixing two metal compounds and two organic ligands, one organic ligand may be dispersed in a solvent, followed by addition and mixing of one metal compound to prepare a mixture (A), and another organic ligand may be dispersed in a solvent, followed by addition and mixing of another metal compound to prepare a mixture (B), and then the mixtures (A) and (B) may be mixed (separate mixing step). Among these, the separate mixing step is preferred. The separate mixing steps described above allow for sufficient coordination of an organic ligand with a high affinity for a certain metal, enabling the production of a more homogeneous composite metal oxide in the subsequent steps. In the mixing step, the method for adding each component is not particularly limited, and known or conventional methods can be applied. For example, the components may be added to the reaction system all at once, diluted with a solvent and then added all at once, added continuously, or a continuous addition operation followed by interruption of the addition operation may be repeated. Known or conventional methods can be applied as a method for continuous addition, such as a method using a microtube pump or a dropping funnel.

[0108] In the mixing step, the method for mixing the catalyst and / or water is not particularly limited. For example, the catalyst and / or water may be dispersed in a solvent in advance, and then two or more metal compounds and two or more organic ligands may be added. Alternatively, two or more metal compounds and two or more organic ligands may be mixed together, and then the catalyst and / or water may be added. Among these, adding the catalyst and water after the separate mixing step is preferred. In the mixing step, the method for adding the catalyst and / or water is not particularly limited, and known or conventional methods can be applied. For example, the catalyst and / or water may be added all at once to the reaction system, or may be added all at once after diluting with a solvent, or may be added continuously, or may be repeated with continuous addition and interruption of the addition. Known or conventional methods can be applied as the method for continuous addition, such as a method using a microtube pump or a dropping funnel. Among these, a method using a microtube pump is preferred.

[0109] In the above-mentioned mixing step, when the one metal compound is a titanium alkoxide, the organic ligand is preferably a dicarbonyl compound, more preferably a 1,3-dicarbonyl compound, and even more preferably a 1,3-diketone compound. Among these, acetylacetone is particularly preferred when selective permeation of small gas molecules such as H is desired. Furthermore, when the other metal compound is an aluminum alkoxide or a zirconium alkoxide, the organic ligand is preferably a polyol derivative or a polyol compound, more preferably a polyol compound, even more preferably a polyalkanolamine, and even more preferably a dialkanolamine. Among these, diethanolamine is particularly preferred when selective permeation of small gas molecules such as H is desired. When the combination of one metal compound and one organic ligand is as described above, the hydrolysis reaction and condensation polymerization reaction of two or more metal alkoxides proceeds smoothly, and a composite metal oxide can be produced in which the proportion of different metal atoms bonded to each other via oxygen atoms is higher than the proportion of same metal atoms bonded to each other via oxygen atoms. Furthermore, even after the composite metal oxide is produced, the amorphous regions can be stably maintained by sufficiently coordinating each metal with the organic ligands.

[0110] When the sol-gel method is applied to the mixing step, a fluid composite metal sol containing two or more metals and two or more organic ligands is produced by hydrolysis and condensation polymerization of a metal alkoxide. Generally, when the hydrolysis rate or condensation polymerization rate of the metal alkoxide is slow, a chain-like polymer tends to be obtained, while when the rate is fast, condensation polymerization also proceeds in two or three dimensions, resulting in a spherical polymer. To produce a gas separation membrane with a smaller pore size and a larger specific surface area, it is preferable to form a chain-like polymer sol with a smaller molecular weight in the mixing step. On the other hand, to produce a gas separation membrane with a relatively large pore size and a relatively small specific surface area, it is preferable to form a spherical polymer sol with a larger molecular weight in the mixing step. Furthermore, in order to laminate a layer with a relatively large pore size and a relatively small specific surface area and a layer with a smaller pore size and a large specific surface area, both a spherical polymer sol and a chain-like polymer sol may be prepared.

[0111] In order to slow the hydrolysis rate or polycondensation rate of the metal alkoxide, in addition to adjusting the substituents or organic ligand structure of the metal alkoxide as described above, the rate can also be adjusted by operations such as lowering the concentration of the metal alkoxide in the reaction solution, increasing the concentration of water, or lowering the reaction temperature. The reaction temperature can be, for example, 10°C or higher and 40°C or lower, or can be room temperature. Furthermore, when it is desired to accelerate the hydrolysis rate or polycondensation rate of the metal alkoxide, the reaction temperature can be, for example, 60°C or higher and 120°C or lower. The reaction time can be, for example, 10 minutes or higher and 4 hours or lower. Furthermore, when it is desired to accelerate the hydrolysis rate or polycondensation rate of the metal alkoxide, the reaction time can be, for example, 5 hours or higher and 50 hours or lower. The hydrolysis reaction and polycondensation reaction in the mixing step can also be performed under heated reflux conditions.

[0112] The manufacturing method of the present disclosure can also be applied to the manufacture of other layers. However, when manufacturing a particle layer, the frit described in [Gas separation membrane] is further mixed with the composite metal sol obtained in the mixing step.

[0113] (Heating Step) In the heating step, a gas separation membrane can be obtained by heating the composite metal sol obtained in the mixing step. Here, the composite metal sol can be heated to evaporate the solvent and water to form a composite metal gel, and the composite metal gel can then be heated to obtain a gas separation membrane. Alternatively, the composite metal sol can be heated directly to obtain a gas separation membrane. The heating step may include a step of molding (forming) the composite metal sol (molding step). The composite metal sol may be molded and then heated, or molding and heating may be performed simultaneously. Alternatively, the composite metal sol may be heated to form a composite metal gel and then molded. The molding method is not particularly limited, and any known or conventional method may be used. For example, the composite metal sol can be molded by applying, spraying, or spin-coating the composite metal sol to a substrate. Alternatively, the composite metal sol can be molded by immersing the substrate in the composite metal sol. Furthermore, a thin film containing the composite metal gel may be formed by preheating the substrate, applying the composite metal sol while evaporating the solvent and water in the composite metal sol, or by simultaneously performing the molding operation and heating operation (hot coating method). In the case of the hot coating method, after forming a thin film, a calcination operation as described below may be performed, or further heating may be performed before the calcination operation as described below. When the composite metal sol is applied to the substrate without heating it, the composite metal sol penetrates into the pores of the porous substrate, allowing a relatively thick film to be formed (cold coating method). In the case of the cold coating method, after forming a thin film, a calcination operation as described below may be performed, or further heating may be performed before the calcination operation as described below. When the substrate is immersed in the composite metal sol, an even thicker film can be formed.

[0114] The heating temperature for heating the composite metal sol to generate the composite metal gel can be, for example, 30° C. or higher and 200° C. or lower. The heating time can be, for example, 5 minutes or higher and 50 hours or lower. When the hot coating method is used, the above heating temperature and heating time can be applied to the substrate.

[0115] When a gas separation membrane is produced by heating (calcining) a composite metal sol or composite metal gel, the calcination temperature is not particularly limited, and is preferably 100°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. The calcination temperature is preferably 1000°C or lower, more preferably 800°C or lower, even more preferably 600°C or lower, even more preferably 500°C or lower, and particularly preferably 400°C or lower. When the calcination temperature is within the above range, the loss of organic ligands contained in the gas separation membrane can be suppressed, and the structure of the composite metal oxide can be stably maintained. The calcination time is not particularly limited, and can be, for example, 5 minutes or longer and 10 hours or shorter. The heating operation, particularly the heating operation for obtaining a gas separation membrane, may be referred to as the calcination operation. When the hot coating method is used, the above calcination temperature and calcination time can be applied to the substrate.

[0116] The number of times the heating step is performed is not particularly limited, and a thicker membrane can be obtained by repeating the heating step multiple times. Furthermore, a gas separation membrane having a laminated structure can be produced by forming a layer with a relatively large pore size and a relatively small specific surface area on the surface of the porous body, and then forming a layer with a small pore size and a large specific surface area. In this case, the pore size can be adjusted by using two or more composite metal sols with different molecular weights.

[0117] When a gas separation membrane is produced by firing a composite metal sol or a composite metal gel, the firing may be performed in an inert gas atmosphere, an active gas atmosphere, or an air atmosphere. Among these, firing in an inert gas atmosphere is preferred from the viewpoint of suppressing loss of organic ligands. Examples of the inert gas include nitrogen gas, carbon dioxide gas, argon gas, and helium gas.

[0118] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution, and other modifications of the configuration are possible as appropriate within the scope of the spirit of this disclosure. The present disclosure is not limited by the embodiments.

[0119] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0120] Sols used to form the gas separation membrane of the present disclosure, other gas separation membranes, intermediate layers, and particle layers, as well as gels and powders used to measure physical properties, were obtained by the following methods. Note that in this specification, other gas separation membranes formed between the outermost layer of a gas separation membrane module (the gas separation membrane of the present disclosure in the Examples or other gas separation membranes in the Comparative Examples) and the particle layer may also be referred to as intermediate layers.

[0121] Example 1 A substrate 3 shown in FIG. 1 was produced through the following steps. Then, a particle layer 4, an intermediate layer 5, and a gas separation membrane 2 of the present disclosure were formed in this order on the surfaces of the alumina perforated tubes 3a included in the substrate 3, thereby producing a gas separation membrane module 1 having the layered structure shown in FIG. 2.

[0122] 1(a) is a schematic diagram of the substrate 3 produced in this step, and FIG. 1(b) is a schematic diagram of its cross section. In the manufacturing process of the substrate 3, the substrate 3 was obtained by joining the ends of a substantially cylindrical alumina perforated tube 3a (manufactured by Nikkato Corporation, outer diameter 10 mm, inner diameter 8 mm, length 50 mm, hole diameter 3 μm) having no bottoms at both ends to one end of a substantially cylindrical alumina imperforate tube 3b (manufactured by Nikkato Corporation, outer diameter approximately 8 mm, inner diameter approximately 6 mm, length 100 mm) having no bottoms at both ends, and the end of a substantially cylindrical alumina imperforate tube 3c (manufactured by Nikkato Corporation, outer diameter approximately 8 mm, inner diameter approximately 6 mm, length 50 mm) having a bottom only at one end. Specifically, as shown in Figure 1(b), one end of the alumina non-perforated tube 3b and the end without a bottom of the alumina non-perforated tube 3c were tapered, and the inner diameter edges of both ends of the alumina perforated tube 3a were beveled so that they would contact the tapered surfaces, thereby adjusting the shape of the joints of the tubes and connecting them. Next, a mixture of alumina frit and terpineol was applied to the joints and the cross sections of both ends of the alumina perforated tube 3a (application operation), and the temperature was raised from room temperature to 900 °C in a muffle furnace over 5 hours, held for 3 hours, and then slowly cooled to room temperature (heating operation). The above application and heating operations were repeated to join the tubes, thereby obtaining a substrate 3. The substrate 3 was confirmed to have no defects at the joints using the bubble point method. Specifically, after wetting the substrate 3 with ethanol, nitrogen gas was blown into the end of the alumina imperforate tube 3b, and the pressure was increased to 0.03 MPa. If no bubbles were generated at the joint, it was determined that there were no defects in the joint. If bubbles were generated, the coating and heating operations were repeated until no more bubbles were generated, and the joint was then used in the subsequent steps.

[0123] 2 is an enlarged schematic diagram of a cross section of the gas separation membrane module 1. The gas separation membrane module 1 was manufactured through the following steps.

[0124] (Process for Producing Particle Layer 4) In the process for producing the particle layer 4, the large particle layer 4a and the small particle layer 4b were formed in this order on the surface of the alumina perforated tubes 3a included in the substrate 3 through the following steps, thereby forming the particle layer 4.

[0125] <Manufacturing Process of Large Particle Layer 4a> In the manufacturing process of the large particle layer 4a, a mixture of TiO-SiO-ACA colloidal sol and alumina frit having an average particle diameter of 2 μm was applied to the surface of the alumina porous tubes 3a included in the substrate 3, and then fired to form the large particle layer 4a.

[0126] The TiO2-SiO2-ACA colloidal sol was prepared via the following process. 4.04 g of 2-methoxyethanol, 14.6 g of water, and 1.07 g of 36% concentrated hydrochloric acid were added to a vial and thoroughly stirred at room temperature using a magnetic stirrer. Separately, 4.04 g of 2-methoxyethanol, 0.59 g of titanium(IV) tetra-n-propoxide (TiTP), 0.43 g of tetraethyl orthosilicate (TEOS), and 0.21 g of acetylacetone (ACA) were added to an Erlenmeyer flask and stirred at room temperature using a magnetic stirrer for 5 minutes. The solution in the vial was then added dropwise to the stirred solution in the Erlenmeyer flask at a rate of 1 mL / min using a microtube pump. After the entire amount was added dropwise, the mixture was further stirred at room temperature for 1 hour to prepare a 4 wt% TiO2-SiO2-ACA polymer sol. The molar ratio of the raw materials was TiTP:TEOS:ACA = 1:1:1, and HO / (TiTP + TEOS) = 200. The acid catalyst, 36% concentrated hydrochloric acid, was added so that its content was 1.5% by mass, assuming the total mass including the solvent was 100% by mass. In this step, the ratio of water to metal alkoxide was relatively low, and the reaction temperature was room temperature. Therefore, the hydrolysis reaction rate and condensation polymerization rate of the metal alkoxide were slow, and the resulting condensation polymerization product was thought to be a linear polymer.

[0127] A solution obtained by mixing 71.8 g of 2-methoxyethanol and 3.21 g of 36% concentrated hydrochloric acid was added to 25 g of the TiO2-SiO2-ACA polymer sol obtained in the above step, and the mixture was stirred at 80°C for 12 hours to obtain 100 g of 1 mass % TiO2-SiO2-ACA colloidal sol. Note that the mass ratio of added HCl to the total of TiTP and TEOS was 1.16, and it is believed that the high-temperature, long-term reaction in the presence of the added acid catalyst caused condensation polymerization of the linear polymer in two dimensions as well, resulting in the production of a spherical colloidal sol.

[0128] Alumina frit having an average particle size of 2 μm was added to the TiO2-SiO2-ACA colloidal sol obtained in the above process so that the alumina frit accounted for 10% by mass of the total mass, taking the total mass as 100% by mass, to obtain a sol for forming the large particle layer 4a. The sol for forming the large particle layer 4a was applied to the surface of the alumina porous tube 3a portion of the substrate 3 at room temperature using a Bemcot (coating operation). The solvent in the sol was then evaporated by leaving it in a thermostatic bath at 180°C under an air atmosphere for 10 minutes, and then fired in a tubular furnace at 500°C under an air atmosphere for 15 minutes (firing operation). The mixture was then left again in a thermostatic bath at 180°C under an air atmosphere for 10 minutes, and then left in a drying chamber at room temperature. The above coating and firing operations were repeated once more to form the large particle layer 4a.

[0129] <Production process of small particle layer 4b> In the production process of the small particle layer 4b, a mixture of TiO-SiO-ACA colloidal sol and alumina frit with an average particle diameter of 0.2 μm was applied to the surface of the large particle layer 4a, and then fired to form the small particle layer 4b.

[0130] Alumina frit having an average particle diameter of 0.2 μm was added to the TiO2-SiO2-ACA colloidal sol obtained in the manufacturing process of the large particle layer 4a so that the alumina frit accounted for 10% by mass of the total mass, taking the total mass as 100% by mass, to obtain a sol for forming the small particle layer 4b. The sol for forming the small particle layer 4b was applied to the surface of the large particle layer 4a using a Bemcot (coating operation). The sol was then left to stand in a thermostatic bath at 180°C under an air atmosphere for 10 minutes to volatilize the solvent in the sol, and then fired in a tubular furnace at 500°C under an air atmosphere for 15 minutes (firing operation). The sol was then left to stand again in a thermostatic bath at 180°C under an air atmosphere for 10 minutes, and then left to stand in a drying chamber at room temperature. The above coating and firing operations were repeated once more to form the small particle layer 4b. By the above steps, a particle layer 4 including a large particle layer 4 a and a small particle layer 4 b was formed on the surface of the alumina porous tube 3 a of the substrate 3 .

[0131] (Manufacturing process of intermediate layer 5) In the manufacturing process of intermediate layer 5, the intermediate layer 5 was formed by forming a first intermediate layer 5a, a second intermediate layer 5b, and a third intermediate layer 5c in this order on the surface of the particle layer 4 through the following steps.

[0132] <Manufacturing process of first intermediate layer 5a> In the manufacturing process of the first intermediate layer 5a, a TiO2-ZrO2-ACA colloidal sol having an average particle diameter of approximately 60 nm was applied to the surface of the small particle layer 4b, and then baked to form the first intermediate layer 5a.

[0133] A TiO2-ZrO2-ACA colloidal sol with an average particle size of approximately 60 nm was prepared via the following process. 23.29 g of 1-propanol, 0.34 g of water, and 0.50 g of 36% concentrated hydrochloric acid were added to a vial and thoroughly stirred by treating with an ultrasonic cleaner for 5 minutes. Separately, 23.29 g of 1-propanol, 0.91 g of zirconium(IV) tetra-n-butoxide (ZrTB), and 1.09 g of TiTP were added to an Erlenmeyer flask in this order and stirred at 500 rpm for 5 minutes using a magnetic stirrer at room temperature. 0.57 g of ACA was then added to the Erlenmeyer flask and stirred for 5 minutes. Then, using a microtube pump, the solution in the vial was added dropwise to the stirred solution in the Erlenmeyer flask at a rate of 2 mL / min. After the entire amount was added, the mixture was further stirred at room temperature for 1 hour. A mixture of 1.5 g of 36% concentrated hydrochloric acid and 148.5 g of water was then added to the Erlenmeyer flask. The solution was then heated until boiling, and after boiling, the mixture was boiled and stirred for an additional 6 hours to prepare a TiO2-ZrO2-ACA colloidal sol with an average particle size of approximately 60 nm. Note that, because the solvent volatilizes during boiling and stirring, water was added every 15 minutes to maintain the liquid volume before boiling.

[0134] The substrate 3 on which the particle layer 4 was formed was left standing in a 180°C thermostatic chamber under air for 10 minutes or more (heating operation). Next, while the substrate 3 was still hot, the TiO2-ZrO2-ACA colloidal sol with an average particle diameter of approximately 60 nm obtained in the above process was applied to the surface of the small particle layer 4b using a Bemcott (coating operation). The application was performed while ensuring that the sound of the solvent in the sol evaporating could be heard. The substrate was then left standing in a 180°C thermostatic chamber under air for 10 minutes, and then baked in a 500°C tubular furnace under air for 15 minutes (baking operation). The above heating, coating, and baking operations were repeated a total of eight times to form a first intermediate layer 5a on the surface of the small particle layer 4b. The average pore diameter of the first intermediate layer 5a was measured by nanoperm porometry and found to be 2.6 nm.

[0135] <Manufacturing process of second intermediate layer 5b> In the manufacturing process of the second intermediate layer 5b, a TiO2-ZrO2-ACA colloidal sol having an average particle size of approximately 30 nm was applied to the surface of the first intermediate layer 5a, and then the resultant was baked to form the second intermediate layer 5b.

[0136] A TiO2-ZrO2-ACA colloidal sol with an average particle size of approximately 30 nm was prepared via the following process. 24.02 g of 1-propanol, 0.17 g of water, and 0.50 g of 36% concentrated hydrochloric acid were added to a vial and thoroughly stirred by treating with an ultrasonic cleaner for 5 minutes. Separately, 24.02 g of 1-propanol, 0.45 g of ZrTB, and 0.55 g of TiTP were added to an Erlenmeyer flask in this order and stirred at 500 rpm for 5 minutes using a magnetic stirrer at room temperature. 0.29 g of ACA was then added to the Erlenmeyer flask and stirred for 5 minutes. Then, using a microtube pump, the solution in the vial was added dropwise to the stirred solution in the Erlenmeyer flask at a rate of 2 mL / min. After the entire amount was added, the mixture was further stirred at room temperature for 1 hour. A mixture of 1.5 g of 36% concentrated hydrochloric acid and 148.5 g of water was then added to the Erlenmeyer flask. The solution was then heated to a boil, and after boiling, the mixture was boiled and stirred for an additional 6 hours to prepare a TiO2-ZrO2-ACA colloidal sol with an average particle size of approximately 30 nm. Because the solvent volatilized during boiling and stirring, water was added every 15 minutes to maintain the liquid volume before boiling.

[0137] The substrate 3, which had been formed up to the first intermediate layer 5a, was left standing in a 180°C thermostatic chamber under air for 10 minutes or more (heating operation). Next, while the substrate 3 was still hot, the TiO2-ZrO2-ACA colloidal sol with an average particle size of approximately 30 nm obtained in the above process was applied to the surface of the first intermediate layer 5a using a Bemcott (coating operation). The application was performed while ensuring that the sound of the solvent in the sol evaporating could be heard. The substrate was then left standing in a 180°C thermostatic chamber under air for 10 minutes, and then baked in a 500°C tubular furnace under air for 15 minutes (baking operation). The above heating, coating, and baking operations were repeated a total of eight times to form a second intermediate layer 5b on the surface of the first intermediate layer 5a. The average pore diameter of the second intermediate layer 5b was measured by nanoperm porometry and found to be 1.8 nm.

[0138] <Manufacturing Process of Third Intermediate Layer 5c> The substrate 3 on which the second intermediate layer 5b had been formed was left standing in a 180°C thermostatic chamber under air for 10 minutes or more (heating operation). Next, while the substrate 3 was still hot, a TiO2-SiO2-ACA colloidal sol with an average particle size of approximately 15 nm was applied to the surface of the second intermediate layer 5b using a Bemcott (coating operation). The colloidal sol used was the same as that used to form the particle layer 4. The application was performed while ensuring that the sound of the solvent in the sol evaporating could be heard. The substrate was then left standing in a 180°C thermostatic chamber under air for 10 minutes, and then baked in a 500°C tubular furnace under air for 15 minutes (baking operation). The heating, coating, and baking operations were repeated a total of eight times to form the third intermediate layer 5c on the surface of the second intermediate layer 5b. Through the above steps, an intermediate layer 5 including a first intermediate layer 5a, a second intermediate layer 5b, and a third intermediate layer 5c was formed on the surface of the particle layer 4 of the substrate 3. The average pore diameter of the third intermediate layer 5c at this time was measured by nanoperm porometry and was found to be 0.8 nm.

[0139] (Manufacturing Process of Gas Separation Membrane 2) In the manufacturing process of the gas separation membrane 2, the TiO2-Al2O3-ACA-DEA sol (separate mixture) was applied onto the surface of the third intermediate layer 5c, and then fired to form the gas separation membrane 2.

[0140] The TiO2-Al2O3-ACA-DEA sol (separate mixture) was prepared by separately mixing and coordinating TiTP and ACA, and mixing and coordinating aluminum sec-butoxide (AlSB) and diethanolamine (DEA), followed by a subsequent mixing step. Specifically, 1.5098 g of ACA was dispersed in 95.66 g of absolute ethanol, followed by adding 4.2857 g of TiTP and stirring for 12 hours at room temperature using a magnetic stirrer to obtain Solution A. Also, 1.1029 g of DEA was dispersed in 95.66 g of absolute ethanol, followed by adding 3.7143 g of AlSB and stirring for 12 hours at room temperature using a magnetic stirrer to obtain Solution B. Solution A and Solution B were then mixed and stirred for 1 hour at room temperature using a magnetic stirrer to obtain Solution C. In addition, 4.00 g of 36% concentrated hydrochloric acid and 2.7165 g of water were added to 191.33 g of absolute ethanol and mixed for 10 minutes using an ultrasonic cleaner. The resulting solution was added dropwise at 2 mL / min using a microtube pump to Solution C, which was being stirred at room temperature using a magnetic stirrer. After the entire amount was added dropwise, the mixture was stirred for an additional 6 hours to prepare a TiO2-Al2O3-ACA-DEA sol (separate mixture). The molar ratio of the raw materials was TiTP:AlSB:ACA:DEA:HO = 1:1:1:1:10. The 36% concentrated hydrochloric acid used as the acid catalyst was adjusted to 1% by mass when the total mass, including the solvent, was taken as 100% by mass.

[0141] The substrate 3, which had been molded up to the intermediate layer 5, was left standing in a tubular furnace at 180°C under a nitrogen atmosphere for 10 minutes (heating operation). Next, while the substrate 3 was still hot, TiO2-Al2O3-ACA-DEA sol (separately mixed) was applied to the surface of the third intermediate layer 5c using a Bemcot (application operation). The application was performed while ensuring that the sound of the solvent in the sol evaporating could be heard. The substrate was then left standing in a tubular furnace at 180°C under a nitrogen atmosphere for 10 minutes, and then calcined in a tubular furnace heated to 300°C under a nitrogen atmosphere for 15 minutes (calcination operation). The heating, application, and calcination operations were repeated a total of five times to form a gas separation membrane 2. The gas separation membrane module 1 of Example 1 was obtained through these steps. The average pore diameter of the gas separation membrane 2 of Example 1, measured by the NKP method, was 0.52 nm. In the manufacturing process of the gas separation membrane 2, calcination is carried out in a nitrogen atmosphere, thereby further suppressing the loss of the organic ligands due to combustion.

[0142] (For physical property measurements: TiO2-Al2O3-ACA-DEA gel (separate mixture)) In order to evaluate the physical properties of the gas separation membrane formed in Example 1 above, TiO2-Al2O3-ACA-DEA gel (separate mixture) was prepared through the following process and used as a sample for measuring the physical properties described below. In the TiO2-Al2O3-ACA-DEA gel (separate mixture) below, a composite metal network derived from TiO2 and Al2O3 is formed, and it is believed that Ti and Al are coordinated by the organic ligands ACA and DEA. Therefore, the TiO2-Al2O3-ACA-DEA gel (separate mixture) below can be used as a sample that shows how the state of the gel changes upon calcination when a gas separation membrane is formed on the outermost surface of a gas separation membrane module.

[0143] The petri dish containing the TiO2-Al2O3-ACA-DEA sol (separate mixture) obtained above was placed on a hot plate heated to 40°C in an air atmosphere to volatilize the solvent in the sol, thereby obtaining a TiO2-Al2O3-ACA-DEA gel (separate mixture).

[0144] (For measuring physical properties: TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 300°C) In order to evaluate the physical properties of the gas separation membrane formed in Example 1 above, TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 300°C was prepared through the following steps and used as a sample for measuring physical properties as described below. Note that the calcination temperature of 300°C is the same as the calcination temperature used in forming the gas separation membrane described above, and therefore the TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 300°C below can be used as a sample that represents the state of the gas separation membrane formed on the outermost surface of a gas separation membrane module.

[0145] The TiO-AlO-ACA-DEA gel (separate mixture) placed in an alumina vessel was left to stand in a tubular furnace at 180°C under a nitrogen atmosphere for 10 minutes, and then fired in a tubular furnace heated to 300°C under a nitrogen atmosphere for 15 minutes to obtain a TiO-AlO-ACA-DEA powder (separate mixture) fired at 300°C.

[0146] (For measuring physical properties: TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 500°C) In order to evaluate the physical properties of the gas separation membrane formed in Example 1 above, TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 500°C was prepared through the following steps and used as a sample for measuring physical properties described below. Note that the calcination temperature of 500°C is higher than the calcination temperature used in forming the gas separation membrane described above, and therefore the TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 500°C below can be used as a sample that represents the state of a gas separation membrane formed on the outermost surface of a gas separation membrane module when exposed to high temperatures.

[0147] The TiO-AlO-ACA-DEA gel (separate mixture) placed in an alumina vessel was left to stand in a tubular furnace at 180°C under a nitrogen atmosphere for 10 minutes, and then fired in a tubular furnace heated to 500°C under a nitrogen atmosphere for 15 minutes to obtain a TiO-AlO-ACA-DEA powder (separate mixture) fired at 500°C.

[0148] A gas separation membrane module of Example 2 was produced in the same manner as in Example 1, except that in the formation of gas separation membrane 2, the amount of ACA was changed from 1.5098 g to 3.0197 g in the step of obtaining the TiO-AlO-ACA-DEA sol (separate mixture) of Example 1. The molar ratio of the raw materials was TiTP:AlSB:ACA:DEA:HO=1:1:2:1:10.

[0149] A gas separation membrane module of Example 3 was produced in the same manner as in Example 1, except that in the formation of gas separation membrane 2, the amount of DEA added was changed from 1.1029 g to 2.2057 g in the step of obtaining the TiO-AlO-ACA-DEA sol (separate mixture) of Example 1. The molar ratio of the raw materials was TiTP:AlSB:ACA:DEA:HO=1:1:1:2:10.

[0150] Example 4 A gas separation membrane module of Example 4 was produced in the same manner as in Example 1, except that in forming the gas separation membrane 2, a TiO2-Al2O3-ACA-DEA sol (mixed all at once) prepared through the following steps was used instead of the TiO2-Al2O3-ACA-DEA sol (mixed separately) used in Example 1, and the number of coating and heating operations was set to 3 to 5 in total.

[0151] The TiO2-Al2O3-ACA-DEA sol (lump mixture) was prepared by mixing TiTP, AlSB, ACA, and DEA all at once. Specifically, 4.2857 g of TiTP, 3.7143 g of AlSB, 1.5098 g of ACA, and 1.1029 g of DEA were added to 191.33 g of absolute ethanol, followed by stirring at room temperature for 1 hour using a magnetic stirrer to obtain Solution D. Alternatively, 4.00 g of 36% concentrated hydrochloric acid and 2.7165 g of water were added to 191.33 g of absolute ethanol, and the mixture was mixed for 10 minutes using an ultrasonic cleaner. The resulting solution was then added dropwise at 2 mL / min using a microtube pump to Solution D, which was being stirred at room temperature using a magnetic stirrer. After the entire amount was added dropwise, the mixture was stirred for an additional 6 hours to obtain the TiO2-Al2O3-ACA-DEA sol (lump mixture). The molar ratio of the raw materials was TiTP:AlSB:ACA:DEA:HO=1:1:1:1:10. The amount of 36% concentrated hydrochloric acid used as the acid catalyst was 1% by mass when the total mass including the solvent was 100% by mass.

[0152] (For physical property measurement: TiO2-Al2O3-ACA-DEA gel (lump mixture)) TiO2-Al2O3-ACA-DEA gel (lump mixture) was prepared from TiO2-Al2O3-ACA-DEA sol (lump mixture) by the same method as that used to obtain TiO2-Al2O3-ACA-DEA gel (separate mixture), and used as a sample for measuring physical properties described below.

[0153] (For physical property measurements: TiO2-Al2O3-ACA-DEA 300°C calcined powder (lump mixture)) TiO2-Al2O3-ACA-DEA 300°C calcined powder (lump mixture) was prepared from the TiO2-Al2O3-ACA-DEA gel (lump mixture) in the same manner as for obtaining the TiO2-Al2O3-ACA-DEA 300°C calcined powder (separate mixture), and used as a sample for measuring the physical properties described below.

[0154] (For physical property measurements: TiO2-Al2O3-ACA-DEA 500°C calcined powder (lump mixture)) TiO2-Al2O3-ACA-DEA 500°C calcined powder (lump mixture) was prepared from the TiO2-Al2O3-ACA-DEA gel (lump mixture) in the same manner as for obtaining the TiO2-Al2O3-ACA-DEA 500°C calcined powder (separate mixture), and used as a sample for measuring the physical properties described below.

[0155] A gas separation membrane module of Comparative Example 1 was produced in the same manner as in Example 1, except that in forming gas separation membrane 2, a TiO-AlO-DEA sol prepared via the steps described below was used instead of the TiO-AlO-ACA-DEA sol (separately mixed) used in Example 1, and the number of application and heating operations was set to a total of four. The average pore diameter of the gas separation membrane of Comparative Example 1, as measured by the NKP method, was 0.44 nm.

[0156] The TiO2-Al2O3-DEA sol was prepared via the following process. Specifically, 2.2057 g of DEA was dispersed in 191.53 g of absolute ethanol, followed by the addition of 4.2857 g of TiTP and 3.7143 g of AlSB. The mixture was stirred at room temperature for 1 hour using a magnetic stirrer to obtain Solution E. 4.00 g of 36% concentrated hydrochloric acid and 2.7165 g of water were added to 191.33 g of absolute ethanol, and the mixture was mixed for 10 minutes using an ultrasonic cleaner. The resulting solution was then added dropwise at 2 mL / min using a microtube pump to Solution E, which was being stirred at room temperature using a magnetic stirrer. After the entire amount was added dropwise, the mixture was stirred for an additional 6 hours to prepare the TiO2-Al2O3-DEA sol. The molar ratio of the raw materials was TiTP:AlSB:DEA:HO = 1:1:2:10. The amount of 36% concentrated hydrochloric acid used as the acid catalyst was 1% by mass when the total mass including the solvent was taken as 100% by mass.

[0157] (For physical property measurement: TiO2-Al2O3-DEA gel) TiO2-Al2O3-DEA gel was prepared from TiO2-Al2O3-DEA sol by the same method as that for obtaining TiO2-Al2O3-ACA-DEA gel (separate mixture), and used as a sample for measuring physical properties described below.

[0158] (For physical property measurements: TiO2-Al2O3-DEA powder calcined at 300°C) TiO2-Al2O3-DEA powder calcined at 300°C was prepared from the TiO2-Al2O3-DEA gel in the same manner as for obtaining the TiO2-Al2O3-ACA-DEA powder calcined at 300°C (separate mixture), and used as a sample for measuring the physical properties described below.

[0159] (For physical property measurements: TiO2-Al2O3-DEA powder calcined at 500°C) TiO2-Al2O3-DEA powder calcined at 500°C was prepared from the TiO2-Al2O3-DEA gel in the same manner as for obtaining the TiO2-Al2O3-ACA-DEA powder calcined at 500°C (separate mixture), and used as a sample for measuring the physical properties described below.

[0160] A gas separation membrane module of Comparative Example 2 was produced in the same manner as in Example 1, except that in forming gas separation membrane 2, TiO2-Al2O3-ACA sol prepared via the steps below was used instead of the TiO2-Al2O3-ACA-DEA sol (separately mixed) used in Example 1, and the number of application and heating operations was set to a total of 5. The average pore diameter of the gas separation membrane of Comparative Example 2, measured by the NKP method, was 2.60 nm.

[0161] The TiO2-Al2O3-ACA sol was prepared via the following process. Specifically, 3.0197 g of ACA was dispersed in 191.53 g of absolute ethanol, followed by the addition of 4.2857 g of TiTP and 3.7143 g of AlSB. The mixture was stirred at room temperature for 1 hour using a magnetic stirrer to obtain Solution F. 4.00 g of 36% concentrated hydrochloric acid and 2.7165 g of water were added to 191.33 g of absolute ethanol, and the mixture was mixed for 10 minutes using an ultrasonic cleaner. The resulting solution was then added dropwise at 2 mL / min using a microtube pump to Solution F, which was being stirred at room temperature using a magnetic stirrer. After the entire amount was added dropwise, the mixture was stirred for an additional 6 hours to obtain the TiO2-Al2O3-ACA sol. The molar ratio of the raw materials was TiTP:AlSB:ACA:HO = 1:1:2:10. The amount of 36% concentrated hydrochloric acid used as the acid catalyst was 1% by mass when the total mass including the solvent was taken as 100% by mass.

[0162] (For physical property measurement: TiO2-Al2O3-ACA gel) TiO2-Al2O3-ACA gel was prepared from TiO2-Al2O3-ACA sol in the same manner as for obtaining TiO2-Al2O3-ACA-DEA gel (separate mixture), and used as a sample for measuring physical properties described below.

[0163] (For physical property measurements: TiO2-Al2O3-ACA powder calcined at 300°C) TiO2-Al2O3-ACA powder calcined at 300°C was prepared from the TiO2-Al2O3-ACA gel in the same manner as for obtaining the TiO2-Al2O3-ACA-DEA powder calcined at 300°C (separate mixture), and used as a sample for measuring the physical properties described below.

[0164] (For physical property measurements: TiO2-Al2O3-ACA powder calcined at 500°C) TiO2-Al2O3-ACA powder calcined at 500°C was prepared from the TiO2-Al2O3-ACA gel in the same manner as for obtaining the TiO2-Al2O3-ACA-DEA powder calcined at 500°C (separate mixture), and used as a sample for measuring the physical properties described below.

[0165] Reference Example 1 (For measuring physical properties: TiO2 powder fired at 500°C) For comparison with the various fired powders obtained above, TiO2 powder fired at 500°C was prepared through the following steps and used as a sample for measuring the physical properties described below.

[0166] A TiO sol prepared in the same manner as in Comparative Example 1, except that AlSB and DEA were not added, was placed in a petri dish and placed on a hot plate heated to 40°C in an air atmosphere to volatilize the solvent in the sol, thereby preparing a TiO gel. The TiO gel was then placed in an alumina vessel and fired in a tubular furnace heated to 500°C in an air atmosphere for 30 minutes, yielding a TiO powder fired at 500°C.

[0167] Reference Example 2 (Al2O3 powder fired at 800°C for measuring physical properties) For comparison with the various fired powders obtained above, Al2O3 powder fired at 800°C was prepared through the following steps and used as a sample for measuring the physical properties described below.

[0168] An AlO sol prepared in the same manner as in Comparative Example 1, except that TiTP and DEA were not added, was placed in a Petri dish and placed on a hot plate heated to 40°C in an air atmosphere to volatilize the solvent in the sol, thereby preparing an AlO gel. The AlO gel was then placed in an alumina vessel and fired in a tubular furnace heated to 800°C in an air atmosphere for 30 minutes, yielding an AlO powder fired at 800°C.

[0169] [Measurement of Physical Properties] The gel and the calcined powder obtained above were subjected to the following measurements of physical properties.

[0170] (1) Thermogravimetric Differential Thermal Analysis (TG-DTA) Apparatus: STA200RV (Hitachi High-Tech Science Corporation) Measurement conditions Sample amount: 14 mg to 60 mg Atmosphere: N2 (200 mL / min) Protective gas: N2 (100 mL / min) Pan: Quartz Heating condition: 5°C / min Measurement mode: Performed in quasi-isothermal measurement (measurement mode in which the temperature is kept constant when the weight loss rate exceeds 65 μg / min, and the temperature rise is resumed when the weight loss rate falls below 20 μg / min)

[0171] 3(a) shows the TG-DTG curve of the TiO2-Al2O3-ACA-DEA gel (separately mixed) of Example 1, and FIG. 3(b) shows the TG-DTG curve of the TiO2-Al2O3-ACA gel of Comparative Example 2. For reference, when the organic ligands DEA and ACA were subjected to thermogravimetric differential thermal analysis, only one peak appeared in the differential thermogravimetric curve (DTG) of DEA, and the peak temperature T L(DEA) In the case of ACA, only one peak appears in the differential thermogravimetric curve (DTG), and the peak temperature T L(ACA) The peak temperature T of the DEA and ACA gels was approximately 120°C. These peaks are considered to be due to the thermal decomposition of the organic ligands. On the other hand, the differential thermogravimetric curves (DTG) of the TiO2-Al2O3-ACA-DEA gel (separately mixed) of Example 1 in Fig. 3(a) and the TiO2-Al2O3-ACA gel of Comparative Example 2 in Fig. 3(b) show that the peak temperatures T LIn the region at higher temperatures than the above, multiple peaks were observed.

[0172] 3(a) of the TiO2-Al2O3-ACA-DEA gel (separate mixture) of Example 1, the peak in the temperature range below 100°C is attributed to the solvent in the gel, the peak in the temperature range of 100°C or higher but less than 130°C is attributed to the free ACA in the gel, the peak in the temperature range of 130°C or higher but less than 250°C is attributed to the free DEA in the gel and / or the coordinated ACA in the gel, and the peak in the temperature range of 250°C or higher is attributed to the coordinated ACA in the gel and / or the coordinated DEA in the gel. That is, the TiO2-Al2O3-ACA-DEA gel (separate mixture) of Example 1 exhibits multiple peaks in the differential thermogravimetry curve (DTG), and for example, the peaks at peak temperatures of about 150°C, about 180°C, and about 200°C are all attributed to T M >T L(ACA) It was confirmed that the peak temperatures of about 260°C, about 300°C, about 350°C, and about 430°C all satisfied T M >T L(ACA) and T M >T L(DEA) It was confirmed that the above conditions were met.

[0173] Similarly, when the multiple peaks in the differential thermogravimetry curve (DTG) of the TiO2-Al2O3-ACA gel of Comparative Example 2 in Figure 3(b) are examined, it is believed that the peaks in the temperature range below 100°C are due to the solvent in the gel, the peaks in the temperature range from 100°C to less than 130°C are due to the free ACA in the gel, and the peaks in the temperature range above 130°C are due to the coordinated ACA in the gel. That is, the TiO2-Al2O3-ACA gel of Comparative Example 2 exhibits multiple peaks in the differential thermogravimetry curve (DTG), and for example, the peaks at peak temperatures of about 150°C, about 180°C, about 200°C, about 260°C, about 300°C, about 340°C, about 380°C, about 410°C, and about 450°C are all due to T M >T L(ACA)The reason for the presence of multiple peaks is thought to be that the pores in the gas separation membrane can take on a variety of states depending on the pore diameter, the Ti / Al ratio contained in the composite metal oxide that forms the pores, and other factors, and therefore the stable states of the organic ligands coordinated to the metals are all different in a complex manner.

[0174] (2) X-ray Diffraction Analysis (XRD Analysis) XRD analysis was carried out using the following apparatus and conditions: Apparatus: D8 ADVANCE (manufactured by Bruker Japan Co., Ltd.) Measurement conditions Sample filling method: capillary method Tube: Mo tube X-ray intensity: 50 kV, 50 mA Measurement angle: 2θ = 5 to 130° Step width: 0.0204

[0175] Figure 4 shows various X-ray diffraction spectra obtained by XRD analysis. Figure 4(a) shows the X-ray diffraction spectrum of the TiO powder calcined at 500°C in Reference Example 1, and Figure 4(b) shows the X-ray diffraction spectrum of the AlO powder calcined at 800°C in Reference Example 2. Sharp diffraction peaks due to crystalline regions were observed in Figures 4(a) and (b). This confirmed that the calcined powder obtained by solatizing TiTP and AlSB alone without using organic ligands has many crystalline regions. Since no halo due to amorphous regions was observed in Figure 4(a), the crystallinity of the TiO powder calcined at 500°C was calculated to be 100% using the following formula (1). From FIG. 4(b), a halo due to the amorphous region was observed in the range of 2θ = 18 to 22°, and diffraction peaks due to multiple other crystalline regions were observed. Therefore, the crystallinity of the AlO powder fired at 800°C was calculated to be 90% using the following formula (1).

[0176] <Method for calculating crystallinity> 100×Ic / (Ic+Ia) Formula (1) Ic: the sum of integrated intensities of diffraction peaks due to crystalline regions in the X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane Ia: the sum of integrated intensities of halos due to amorphous regions in the X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane

[0177] On the other hand, Figures 4(c) to (f) show the X-ray diffraction spectra of the sintered powders prepared in Example 1 and Comparative Example 1. Compared with the X-ray diffraction spectra of Figures 4(a) and 4(b), the diffraction peaks due to the crystalline regions have disappeared or decreased, and further, halos due to the amorphous regions have been observed.

[0178] Specifically, Figure 4(c) shows the X-ray diffraction spectrum of the TiO2-Al2O3-ACA-DEA powder (separately mixed) calcined at 300°C in Example 1. In the X-ray diffraction spectrum in Figure 4(c), sharp diffraction peaks due to crystalline regions disappear, and halos due to amorphous regions are observed in the 2θ = 10-14°, 18-22°, and 26-30° ranges. Therefore, the calcined powder of Example 1, which contains ACA and DEA as two organic ligands, is considered to have very few crystalline regions and is composed almost entirely of amorphous regions. Furthermore, since no diffraction peaks due to crystalline regions were observed in the X-ray diffraction spectrum in Figure 4(c), the crystallinity of the TiO2-Al2O3-ACA-DEA powder (separately mixed) calcined at 300°C in Example 1 was calculated to be 0% using the above formula (1). That is, the gas separation membrane obtained in Example 1 exhibited halos due to amorphous regions in the ranges of 2θ = 10 to 14°, 18 to 22°, and 26 to 30°, and its crystallinity was 0%.

[0179] Figure 4(e) shows the X-ray diffraction spectrum of the TiO2-Al2O3-DEA powder calcined at 300°C in Comparative Example 1. In the X-ray diffraction spectrum in Figure 4(e), the intensity of the sharp diffraction peaks due to the crystalline regions was reduced, but some remained. Furthermore, halos due to the amorphous regions were observed in the 2θ = 10-14°, 18-22°, and 26-30° ranges. Therefore, the calcined powder of Comparative Example 1, which contains only DEA as the organic ligand, is considered to contain both crystalline and amorphous regions. Since the X-ray diffraction spectrum in Figure 4(e) shows halos due to the amorphous regions and diffraction peaks due to the crystalline regions, the crystallinity of the TiO2-Al2O3-DEA powder calcined at 300°C in Comparative Example 1 was calculated to be 21% using the above formula (1). That is, the gas separation membrane obtained in Comparative Example 1 exhibited halos due to amorphous regions in the ranges of 2θ = 10 to 14°, 18 to 22°, and 26 to 30°, and its crystallinity was 21%.

[0180] Next, to evaluate the thermal stability of the gas separation membrane, the X-ray diffraction spectra of various powders calcined at 500 °C were also examined. First, Figure 4(d) is the X-ray diffraction spectrum of the TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 500 °C in Example 1. The X-ray diffraction spectrum in Figure 4(d) is almost unchanged from the X-ray diffraction spectrum in Figure 4(c) when calcined at 300 °C, indicating that the amorphous structure was maintained. Therefore, it was confirmed that the gas separation membrane of Example 1 is resistant to structural changes even when exposed to high temperatures and has excellent thermal stability. Note that, since no diffraction peaks attributable to crystalline regions were observed in the X-ray diffraction spectrum in Figure 4(d), the crystallinity of the TiO2-Al2O3-ACA-DEA powder (separate mixture) calcined at 500 °C in Example 1 was calculated to be 0% using the above formula (1).

[0181] Figure 4(f) shows the X-ray diffraction spectrum of the TiO2-Al2O3-DEA powder of Comparative Example 1 calcined at 500°C. The X-ray diffraction spectrum of Figure 4(f) shows increased diffraction peak intensity compared to Figure 4(e), which shows the X-ray diffraction spectrum of the powder calcined at 300°C. Therefore, it is believed that the calcined powder of Comparative Example 1, which contains only DEA as an organic ligand, tends to partially collapse its amorphous regions and form new crystalline regions when exposed to high temperatures. Since the X-ray diffraction spectrum of Figure 4(f) shows halos due to amorphous regions and diffraction peaks due to crystalline regions, the crystallinity of the TiO2-Al2O3-DEA powder of Comparative Example 1 calcined at 500°C was calculated to be 48% using the above formula (1).

[0182] Generally, when the crystalline region increases, the grain boundary of the crystal becomes a large gap, and the gas separation ability is thought to decrease. As mentioned above, when only one kind of organic ligand is used, some of the uncoordinated metals among Ti and / or Al remain, so when exposed to high temperatures, the amorphous region cannot be maintained and changes to a crystalline region, which is thought to lead to a decrease in gas separation ability. However, when two kinds of organic ligands are used, both Ti and Al can be sufficiently coordinated, so it is thought that the originally unstable amorphous region can be maintained even when exposed to high temperatures.

[0183] (3) Nitrogen adsorption / desorption test Nitrogen adsorption / desorption test was carried out using the following equipment and conditions: Equipment: BELSORP MAX (manufactured by Microtrac BEL Co., Ltd.) Measurement conditions Adsorbate: N2 Adsorption temperature: 77K Pretreatment method: Vacuum suction, 180°C, 12 hours

[0184] Figure 5 shows various nitrogen adsorption / desorption isotherms obtained by nitrogen adsorption / desorption tests. Figure 5(a) shows the nitrogen adsorption / desorption isotherm for the TiO2-Al2O3-ACA-DEA powder (separately mixed) calcined at 300°C in Example 1, and Figure 5(b) shows the nitrogen adsorption / desorption isotherm for the TiO2-Al2O3-ACA-DEA powder (separately mixed) calcined at 500°C in Example 1. Both the nitrogen adsorption / desorption isotherms in Figures 5(a) and 5(b) exhibited hysteresis, i.e., they were Type IV, in which the amount of nitrogen adsorbed when the nitrogen partial pressure was increased (during adsorption) differed from the amount of nitrogen adsorbed when the nitrogen partial pressure was decreased (during desorption). However, the difference in the amount of nitrogen adsorbed between adsorption and desorption was relatively small. Therefore, it was confirmed that the TiO2-Al2O3-ACA-DEA 300°C calcined powder (separately mixed) of Example 1 can maintain a relatively stable structure and has excellent thermal stability even when exposed to a high temperature of 500°C. Furthermore, since the amount of nitrogen adsorption observed in the nitrogen adsorption / desorption isotherms of Figures 5(a) and (b) is greater than, for example, the amount of nitrogen adsorption in Figures 5(c) and (e), it is considered that the specific surface areas of the TiO2-Al2O3-ACA-DEA 300°C calcined powder (separately mixed) of Example 1 and the TiO2-Al2O3-ACA-DEA 500°C calcined powder (separately mixed) are both greater than the TiO2-Al2O3-DEA 300°C calcined powder of Comparative Example 1 and the TiO2-Al2O3-ACA 300°C calcined powder of Comparative Example 2.

[0185] On the other hand, Figure 5(c) shows the nitrogen adsorption / desorption isotherm of the TiO2-Al2O3-DEA powder calcined at 300°C in Comparative Example 1, and Figure 5(d) shows the nitrogen adsorption / desorption isotherm of the TiO2-Al2O3-DEA powder calcined at 500°C in Comparative Example 1. The nitrogen adsorption / desorption isotherm in Figure 5(c) shows that the amount of nitrogen adsorbed was very small, confirming that the specific surface area of ​​the TiO2-Al2O3-DEA powder calcined at 300°C in Comparative Example 1 was very small. Furthermore, the shape of the nitrogen adsorption / desorption isotherm in Figure 5(d) was significantly different from that of the isotherm in Figure 5(c), confirming that it was a type IV isotherm with hysteresis. Here, in the nitrogen adsorption / desorption isotherm in FIG. 5(d), the difference in the amount of nitrogen adsorbed during adsorption and desorption is large, and it was confirmed that the structure of the TiO-AlO-DEA powder calcined at 500°C in Comparative Example 1 changed when exposed to high temperatures, resulting in an increase in mesopores (pores with an average pore diameter of approximately 2.0 nm to 50 nm).

[0186] 5(e) shows the nitrogen adsorption / desorption isotherm of the TiO2-Al2O3-ACA powder calcined at 300°C in Comparative Example 2. The nitrogen adsorption / desorption isotherm in Fig. 5(e) is a Langmuir type, in which the amount of nitrogen adsorption is large in the low nitrogen partial pressure region and does not change significantly in the high nitrogen partial pressure region. Generally, a Langmuir type adsorption isotherm suggests the presence of micropores (pores with an average pore diameter of approximately 2.0 nm or less). Therefore, it is believed that the TiO2-Al2O3-ACA powder calcined at 300°C in Comparative Example 2 has micropores.

[0187] [Evaluation] The gas separation membrane modules obtained in the Examples and Comparative Examples were subjected to the following gas separation performance evaluation test.

[0188] <Gas Separation Performance> FIG. 6 is a schematic diagram of a gas permeation device 10 used in a gas separation performance evaluation test. As shown in FIG. 6, the gas separation membrane module 1 obtained in each of the examples and comparative examples was installed inside a test cell 15. During the test, the internal temperature of the test cell 15 was controlled at 150°C using a temperature controller 16a, a high-temperature K thermocouple 16b, and a mantle heater 16c. He, H 2 , CO 2 , N 2 , CH 4 , and CF 4 gases were introduced through a gas inlet 11 located upstream of the gas flow path connected to the test cell 15, and the gas pressure was controlled within a range of 0.15 to 0.2 MPa using a pressure regulator 12 and an upstream pressure gauge 13a installed between the test cell 15 and the gas inlet 11. The downstream side of the gas flow path connected to the interior of the gas separation membrane module 1 was connected to a downstream exhaust port 18a of the gas separation membrane module and set to atmospheric pressure (0.1 MPa), creating a pressure difference with the upstream side. This pressure difference causes the gas introduced into the test cell 15 to permeate the gas separation membrane module 1. The flow rate of the gas permeating the gas separation membrane module 1 was measured by a fully automatic soap film flowmeter 17 installed between the inside of the gas separation membrane module 1 and the downstream exhaust port 18a of the gas separation membrane module. The pressure of the gas permeating the gas separation membrane module 1 was measured by a downstream pressure gauge 13b installed between the gas separation membrane module 1 and the downstream exhaust port 18a of the gas separation membrane module. The downstream side of the gas flow path connected to the test cell 15 was connected to the test cell downstream exhaust port 18b, and the test cell downstream stop valve 14c was closed to allow the entire amount of the introduced gas to permeate the gas separation membrane module 1.

[0189] The permeability of each gas determined from the test results is shown in Figure 7. Table 1 shows the configuration of the gas separation membrane module of each example and comparative example, and the gas permeability ratio of H to CH or CF.

[0190]

[0191] As shown in Figure 7 and Table 1, the gas separation membrane modules of the Examples, which had gas separation membranes using two types of organic ligands, and the gas separation membrane modules of the Comparative Examples, which had other gas separation membranes using one type of organic ligand, all exhibited permeability ratios higher than the theoretical permeability ratio based on Knudsen diffusion, demonstrating excellent gas separation ability. In particular, the gas separation membrane modules of Examples 1 to 3 tended to have even better gas separation ability than the gas separation membrane modules of Comparative Examples 1 and 2, and in particular, tended to have an extremely excellent permeability ratio of H to CF. Furthermore, with regard to the permeability ratio of H to CH, the gas separation membrane module of Example 3, in which the molar ratio of the raw materials was TiTP:AlSB:ACA:DEA:HO = 1:1:1:2:10, exhibited the best gas separation ability.

[0192] Variations of the present disclosure are described below. [Appendix 1] A gas separation membrane comprising a composite metal oxide having two or more metals and two or more organic ligands. [Appendix 2] The gas separation membrane according to Appendix 1, wherein the two or more metals are two or more selected from the group consisting of metal elements of Group 2, Group 3, Group 4, Group 13, and Group 14. [Appendix 3] The gas separation membrane according to Appendix 1 or 2, wherein the composite metal oxide contains Ti and Al and / or Zr, and wherein the molar ratio of the total amount of Al and / or Zr to 1 mole of Ti is 0.01 or more and 100 or less. [Appendix 4] The gas separation membrane according to Appendix 3, wherein the molar ratio of the total amount of Al and / or Zr to 1 mole of Ti is 0.05 or more and 20 or less. [Appendix 5] The gas separation membrane according to Appendix 3, wherein the molar ratio of the total amount of Al and / or Zr to 1 mole of Ti is 0.1 or more and 10 or less. [Appendix 6] The gas separation membrane according to Appendix 3, wherein the molar ratio of the total amount of Al and / or Zr to 1 mole of Ti is 0.2 or more and 5 or less. [Appendix 7] The gas separation membrane according to any one of Appendices 1 to 3, wherein the composite metal oxide comprises Ti and Al, and the molar ratio of Al to 1 mole of Ti is 0.01 or more and 100 or less. [Appendix 8] The gas separation membrane according to Appendix 7, wherein the molar ratio of Al to 1 mole of Ti is 0.05 or more and 20 or less. [Appendix 9] The gas separation membrane according to Appendix 7, wherein the molar ratio of Al to 1 mole of Ti is 0.1 or more and 10 or less. [Appendix 10] The gas separation membrane according to Appendix 7, wherein the molar ratio of Al to 1 mole of Ti is 0.2 or more and 5 or less. [Appendix 11] The gas separation membrane according to any one of Appendices 1 to 10, wherein the two or more organic ligands are multidentate ligands. [Appendix 12] The gas separation membrane according to Appendices 11, wherein the multidentate ligand is one or more selected from the group consisting of a dicarbonyl compound, a polyol compound, and a polyol derivative. [Appendix 13] The gas separation membrane according to Appendices 11 or 12, wherein the multidentate ligand comprises a dicarbonyl compound and a polyol compound.[Appendix 14] The gas separation membrane according to any one of Appendices 1 to 13, wherein the composite metal oxide comprises Ti and Al and / or Zr, and the two or more organic ligands are a dicarbonyl compound and a polyol compound, wherein the dicarbonyl compound is coordinated to the Ti and the polyol compound is coordinated to the Al and / or Zr. [Appendix 15] The gas separation membrane according to any one of Appendices 12 to 14, wherein the dicarbonyl compound comprises a 1,3-dicarbonyl compound. [Appendix 16] The gas separation membrane according to Appendices 15, wherein the 1,3-dicarbonyl compound comprises one or more selected from the group consisting of acetylacetone, 6-methyl-2,4-heptanedione, 2,6-dimethyl-3,5-heptanedione, and ethyl acetoacetate. [Appendix 17] The gas separation membrane according to Appendices 15 or 16, wherein the 1,3-dicarbonyl compound comprises acetylacetone. [Appendix 18] The gas separation membrane according to any one of Appendices 12 to 17, wherein the polyol compound comprises a polyalkanolamine. [Appendix 19] The gas separation membrane according to Appendices 18, wherein the polyalkanolamine comprises a dialkanolamine. [Appendix 20] The gas separation membrane according to Appendices 19, wherein the dialkanolamine comprises one or more selected from the group consisting of diethanolamine, N-methyldiethanolamine, diisopropanolamine, and N-ethyldiethanolamine. [Appendix 21] The gas separation membrane according to Appendices 20, wherein the dialkanolamine comprises diethanolamine. [Appendix 22] The gas separation membrane according to any one of Appendices 1 to 21, wherein the average pore diameter measured by the normalized Knudsen-based permeance method (NKP method) is 0.6 nm or less. [Appendix 23] The composite metal gel includes a structure derived from a composite metal gel containing the two or more metals and the two or more organic ligands, and the composite metal gel has a peak temperature T in a differential thermogravimetric curve (DTG) obtained by thermogravimetric differential thermal analysis. M The organic ligand exhibits a peak at a peak temperature T L A peak appears at the peak temperature T M and the peak temperature T L Is T M>T LThe gas separation membrane according to any one of Appendices 1 to 22, satisfying the following. [Appendix 24] The gas separation membrane according to any one of Appendices 1 to 23, having a crystallinity of 20% or less, as represented by the following formula (1): <Method for calculating crystallinity> 100 × Ic / (Ic + Ia) Formula (1) Ic: the sum of integrated intensities of diffraction peaks due to crystalline regions in an X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane Ia: the sum of integrated intensities of halos due to amorphous regions in an X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane [Appendix 25] A method for producing a gas separation membrane, comprising the steps of preparing a mixture containing two or more metal compounds and two or more organic ligands, and heating the mixture. [Appendix 26] The method for producing a gas separation membrane according to Appendices 25, wherein the step of preparing the mixture comprises the steps of mixing each of the metal compounds with one or more of the organic ligands, and then further mixing the resulting mixtures. [Appendix 27] The method for producing a gas separation membrane according to Appendices 25 or 26, wherein the two or more metal compounds are two or more metal alkoxides. [Appendix 28] The method for producing a gas separation membrane according to any one of Appendices 25 to 27, wherein the two or more metal alkoxides are metal alkoxides formed from two or more metals selected from the group consisting of metal elements of Group 2, metal elements of Group 3, metal elements of Group 4, metal elements of Group 13, and metal elements of Group 14. [Appendix 29] The method for producing a gas separation membrane according to Appendices 27 or 28, wherein the two or more metal alkoxides are a titanium alkoxide and an aluminum alkoxide or a zirconium alkoxide, and the molar ratio of the total amount of the aluminum alkoxide and / or zirconium alkoxide to 1 mole of the titanium alkoxide is 0.01 or more and 100 or less. [Appendix 30] The method for producing a gas separation membrane according to Appendix 29, wherein the molar ratio of the total amount of the aluminum alkoxide and / or zirconium alkoxide to 1 mole of the titanium alkoxide is 0.05 or more and 20 or less. [Appendix 31] The method for producing a gas separation membrane according to Appendix 29, wherein the molar ratio of the total amount of the aluminum alkoxide and / or zirconium alkoxide to 1 mole of the titanium alkoxide is 0.1 or more and 10 or less.[Appendix 32] A method for producing a gas separation membrane according to Appendix 29, wherein the molar ratio of the total amount of the aluminum alkoxide and / or zirconium alkoxide to 1 mole of the titanium alkoxide is 0.2 or more and 5 or less. [Appendix 33] A method for producing a gas separation membrane according to Appendix 27 or 28, wherein the two or more metal alkoxides are titanium alkoxide and aluminum alkoxide, and the molar ratio of the aluminum alkoxide to 1 mole of the titanium alkoxide is 0.01 or more and 100 or less. [Appendix 34] A method for producing a gas separation membrane according to Appendix 33, wherein the molar ratio of the aluminum alkoxide to 1 mole of the titanium alkoxide is 0.05 or more and 20 or less. [Appendix 35] A method for producing a gas separation membrane according to Appendix 33, wherein the molar ratio of the aluminum alkoxide to 1 mole of the titanium alkoxide is 0.1 or more and 10 or less. [Appendix 36] A method for producing a gas separation membrane according to Appendix 33, wherein the molar ratio of the aluminum alkoxide to 1 mole of the titanium alkoxide is 0.2 or more and 5 or less. [Appendix 37] The method for producing a gas separation membrane according to any one of Appendices 25 to 36, wherein the two or more organic ligands are multidentate ligands. [Appendix 38] The method for producing a gas separation membrane according to Appendices 37, wherein the multidentate ligand is one or more selected from the group consisting of a dicarbonyl compound, a polyol compound, and a polyol derivative. [Appendix 39] The method for producing a gas separation membrane according to Appendices 37 or 38, wherein the multidentate ligand comprises a dicarbonyl compound and a polyol compound. [Appendix 40] The method for producing a gas separation membrane according to any one of Appendices 25 to 32, wherein the step of preparing a mixture comprises a step of mixing a titanium alkoxide as the metal compound with a dicarbonyl compound as the organic ligand, a step of mixing an aluminum alkoxide and / or a zirconium alkoxide as the metal compound with a polyol compound as the organic ligand, and a step of subsequently further mixing the respective mixtures.

[0193] REFERENCE SIGNS LIST 1 Gas separation membrane module 2 Gas separation membrane 3 Substrate 3a Alumina perforated tube 3b Alumina non-porous tube 3c Alumina non-porous tube 4 Particle layer 4a Large particle layer 4b Small particle layer 5 Intermediate layer 5a First intermediate layer 5b Second intermediate layer 5c Third intermediate layer 10 Gas permeation device 11 Gas inlet 12 Pressure regulator 13a Upstream pressure gauge 13b Downstream pressure gauge 14a Upstream stop valve 14b Gas separation membrane module downstream stop valve 14c Test cell downstream stop valve 15 Test cell 16a Temperature controller 16b High temperature compatible K thermocouple 16c Mantle heater 17 Fully automatic soap film flow meter 18a Gas separation membrane module downstream exhaust port 18b Test cell downstream exhaust port 19 Back pressure regulator

Claims

1. A gas separation membrane comprising a composite metal oxide having two or more metals and two or more organic ligands.

2. The gas separation membrane according to claim 1, wherein the two or more metals are two or more selected from the group consisting of metal elements of Group 2, metal elements of Group 3, metal elements of Group 4, metal elements of Group 13, and metal elements of Group 14.

3. A gas separation membrane as described in claim 1 or 2, wherein the composite metal oxide contains Ti and Al and / or Zr, and the molar ratio of the total amount of Al and / or Zr to 1 mole of Ti is 0.01 or more and 100 or less.

4. The gas separation membrane according to claim 1 or 2, wherein the two or more organic ligands are multidentate ligands.

5. The gas separation membrane according to claim 4, wherein the multidentate ligand is one or more selected from the group consisting of dicarbonyl compounds, polyol compounds, and polyol derivatives.

6. The gas separation membrane described in claim 1 or 2, wherein the composite metal oxide has Ti and Al and / or Zr, the two or more types of organic ligands are a dicarbonyl compound and a polyol compound, the dicarbonyl compound is coordinated to the Ti, and the polyol compound is coordinated to the Al and / or Zr.

7. The gas separation membrane according to claim 1 or 2, which has an average pore size measured by the normalized Knudsen-based permeance method (NKP method) of 0.6 nm or less.

8. The composite metal gel includes a structure derived from a composite metal gel containing the two or more metals and the two or more organic ligands, and the composite metal gel has a peak temperature T M The organic ligand exhibits a peak at a peak temperature T L A peak appears at the peak temperature T M and the peak temperature T L , T M >T L The gas separation membrane according to claim 1 or 2, which satisfies the above.

9. The gas separation membrane according to claim 1 or 2, having a crystallinity of 20% or less, as represented by the following formula (1): <Method of calculating crystallinity> 100×Ic / (Ic+Ia) formula (1) Ic: sum of integrated intensities of diffraction peaks due to crystalline regions in an X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane Ia: sum of integrated intensities of halos due to amorphous regions in an X-ray diffraction spectrum obtained when XRD analysis is performed on the gas separation membrane 10. A method for producing a gas separation membrane, comprising the steps of preparing a mixture containing two or more metal compounds and two or more organic ligands, and heating the mixture.

11. The method for producing a gas separation membrane described in claim 10, wherein the step of preparing the mixture comprises a step of mixing each of the metal compounds with one or more of the organic ligands, and then a step of further mixing the respective mixtures.

12. The method for producing a gas separation membrane according to claim 10 or 11, wherein the two or more metal compounds are two or more metal alkoxides.

13. The method for producing a gas separation membrane described in claim 12, wherein the two or more metal alkoxides are metal alkoxides formed from two or more metals selected from the group consisting of metal elements of Group 2, metal elements of Group 3, metal elements of Group 4, metal elements of Group 13, and metal elements of Group 14.

14. A method for producing a gas separation membrane as described in claim 12 or 13, wherein the two or more metal alkoxides are a titanium alkoxide and an aluminum alkoxide or a zirconium alkoxide, and the molar ratio of the total amount of the aluminum alkoxide and / or zirconium alkoxide to 1 mole of the titanium alkoxide is 0.01 or more and 100 or less.

15. The method for producing a gas separation membrane according to claim 10 or 11, wherein the two or more organic ligands are multidentate ligands.

16. The method for producing a gas separation membrane according to claim 15, wherein the multidentate ligand is one or more selected from the group consisting of dicarbonyl compounds, polyol compounds, and polyol derivatives.

17. The method for producing a gas separation membrane according to claim 10 or 11, wherein the step of preparing the mixture comprises the steps of: mixing a titanium alkoxide as the metal compound with a dicarbonyl compound as the organic ligand; mixing an aluminum alkoxide and / or a zirconium alkoxide as the metal compound with a polyol compound as the organic ligand; and then further mixing the respective mixtures.

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