Separation membrane and method for producing same

Abstract

Provided is a separation membrane comprising a separation layer having an amorphous structure, the separation layer containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond, for example, and (B) a metal ion, the polymer being obtained by polymerizing a precursor containing a compound represented by general formula (1). (In the formula, each X independently represents a group represented by formula (2) or a monovalent hydrocarbon group having 1-8 carbon atoms, and at least one of the X represents a group represented by formula (2). (In the formula, R1 is an alkylene group having 1-8 carbon atoms, R2 is each independently a monovalent hydrocarbon group having 1-8 carbon atoms, R3 is a hydrogen atom or an alkyl group having 1-4 carbon atoms, n is an integer of 1-3, and a wavy line represents a binding end)

Description

TECHNICAL FIELD

[0001] The present application relates to a separation membrane and a method for manufacturing the same. BACKGROUND

[0002] A separation method using a porous separation membrane is inexpensive and has high separation ability compared to separation methods such as filtration, evaporation, crystallization, solvent extraction, and distillation. A porous separation membrane separates target substances using molecular sieving.

[0003] Silicon-based materials are excellent in mechanical strength, heat resistance, and chemical stability, and are used as materials for porous inorganic separation membranes. However, in the case where a silicon-based material is used as a material for a separation membrane, densification of pores occurs under high-temperature water vapor, and the permeability of the separation membrane decreases. In order to alleviate this densification, a separation membrane including a separation layer in which metal ions are doped in a silicon-based material has been developed (Patent Document 1).

[0004] In addition, with respect to a carbon dioxide (CO2) recovery and storage technology using a silicon-based material, a separation membrane including a separation layer using a polymer in which a compound including a urea group and an alkoxysilyl group is polymerized, a separation membrane including a separation layer using a polymer in which a compound including an amino group and an alkoxysilyl group is polymerized (Patent Documents 2 and 3) are known.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-151708

[0008] Patent Document 2: Japanese Patent Application Publication No. 2021-186712

[0009] Patent Document 3: Japanese Patent Application Publication No. 2022-21175 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] In Patent Document 1, pores are formed in the separation layer by doping metal ions. However, the size of the pores formed is small, and the permeability of carbon dioxide, which is a relatively large molecule, is low. Furthermore, it is difficult to form uniform pores in the separation layer and to improve gas selectivity.

[0012] In addition, as in Patent Documents 2 and 3, with respect to a separation membrane using an existing organosilicon compound having an amino group or a urea group, it is difficult to achieve sufficient carbon dioxide permeability and CO2 / N2 selectivity.

[0013] The present application has been achieved in view of the above-described actual circumstances, and aims to provide a separation membrane capable of realizing high carbon dioxide permeability and gas selectivity.

[0014] Means for solving the problem

[0015] The present inventors have intensively studied in order to achieve the above-described object, and as a result, have found that a separation membrane having a separation layer containing a polymer having an isocyanuric acid skeleton and a siloxane bond and metal ions exhibits high carbon dioxide permeability and CO2 / N2 selectivity, and have completed the present application.

[0016] That is, the present application provides:

[0017] 1. A separation membrane comprising a separation layer having an amorphous structure, the separation layer containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) metal ions;

[0018] 2. The separation membrane according to 1, wherein the (A) component is a polymer obtained by polymerizing a precursor containing a compound represented by the following general formula (1),

[0019] [Chemical Formula 1]

[0020]

[0021] (In the formula, X's are each independently a group represented by the following formula (2) or a monovalent hydrocarbon group having 1 to 8 carbon atoms, and at least one of the X's is a group represented by the following formula (2).)

[0022] [Chemical Formula 2]

[0023]

[0024] (In the formula, R 1 is an alkylene group having 1 to 8 carbon atoms, R 2 's are each independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, R 3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 3. The line with a wavy line indicates a binding end.)

[0025] 3. The separation membrane according to 2, wherein the (A) component is a polymer obtained by polymerizing a precursor containing tris[3-(trimethoxysilyl)propyl]isocyanurate;

[0026] 4. The separation membrane according to any one of 1 to 3, wherein the metal in the (B) component is one or more selected from the group consisting of nickel, copper, silver, cobalt, and zinc;

[0027] 5. A method for producing a separation membrane, comprising: (I) a metal-doped polymer sol preparation step of preparing a metal-doped polymer sol containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) metal ions; (II) a coating step of coating the metal-doped polymer sol directly or via an intermediate layer on a porous support; and (III) a firing step of firing the metal-doped polymer sol coated in the coating step to form a separation layer having an amorphous structure.

[0028] 6. The method for producing a separation membrane according to 5, wherein the metal-doped polymer sol preparation step is performed by mixing a sol of the (A) polymer and a metal salt that is a supply source of the (B) metal ions.

[0029] 7. The method for producing a separation membrane according to 5 or 6, wherein the (A) component is a polymer obtained by polymerizing a precursor containing a compound represented by the following general formula (1),

[0030] [Chem. 3]

[0031]

[0032] (In the formula, X's are each independently a group represented by the following formula (2) or a monovalent hydrocarbon group having 1 to 8 carbon atoms, and at least one of the X's is a group represented by the following formula (2).)

[0033] [Chem. 4]

[0034]

[0035] (In the formula, R 1 is an alkylene group having 1 to 8 carbon atoms, R 2 's are each independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, R 3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 3.)

[0036] 8. The method for producing a separation membrane according to 7, wherein the (A) component is a polymer obtained by polymerizing a precursor containing tris[3-(trimethoxysilyl)propyl]isocyanurate;

[0037] 9. The method for producing a separation membrane according to any one of 5 to 8, wherein the metal in the (B) component is one or more selected from the group consisting of nickel, copper, silver, cobalt, and zinc.

[0038] Effects of the Invention

[0039] The separation membrane of the present application is excellent in carbon dioxide permeability and gas selectivity, and is therefore useful for separation, recovery, and storage processes of carbon dioxide from a mixed gas and a mixed organic solvent. Attached Figure Description

[0040] Figure 1 This is a schematic cross-sectional view illustrating an example of the separation membrane involved in the present invention.

[0041] Figure 2 The graphs representing the characteristics of nickel-doped TTPI and TTPI are shown below: (a) results from UV-Vis spectrophotometry, and (b) results from Fourier transform infrared spectrophotometry (wavenumbers 500–2000 cm⁻¹). -1 (c) and (d) are the results of the X-ray photoelectron spectroscopy.

[0042] Figure 3 The figures representing the properties of nickel-doped TTPI powder and TTPI powder are as follows: (a) shows the X-ray diffraction results of the powder sintered at 250°C, and (b) shows the transmission electron microscope image.

[0043] Figure 4 The N2 adsorption-desorption isotherms are for nickel-doped TTPI powder and TTPI powder.

[0044] Figure 5 This is a schematic diagram illustrating the mechanism of Ni-TTPI network formation with Ni / N molar ratios of 0, 0.25, and 0.50.

[0045] Figure 6 A coordinate graph representing the CO2 adsorption-desorption isotherms of nickel-doped TTPI powder and TTPI powder.

[0046] Figure 7 The graph represents the permeability of the separation membrane, and the coordinate graph represents the relationship between gas molecule size and gas permeability.

[0047] Figure 8 The graphs representing the permeability of the separation membranes are as follows: (a) is a graph showing the temperature dependence of the CO2 and N2 permeability and the CO2 / N2 permeability ratio of the separation membrane obtained in Comparative Example 1; (b) is a graph showing the temperature dependence of the CO2 and N2 permeability and the CO2 / N2 permeability ratio of the separation membrane obtained in Example 1; (c) is a graph showing the temperature dependence of the CO2 and N2 permeability and the CO2 / N2 permeability ratio of the separation membrane obtained in Example 2; and (d) is a graph showing the temperature dependence of the CO2 and N2 permeability and the CO2 / N2 permeability ratio of the separation membrane obtained in Example 3. Detailed Implementation

[0048] The present invention will now be described in detail.

[0049] (1) Separation membrane

[0050] The separation membrane of the present application includes a separation layer having an amorphous structure, which contains (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) a metal ion. Further, in the present application, the so-called amorphous structure means a state in which a network structure formed by the siloxane bond in the polymer being combined in a network and a network structure formed by the nitrogen atom in the isocyanuric acid skeleton and the metal ion being coordinated and bonded, and a large number of fine pores constituted by the gaps of the network are formed in the separation layer.

[0051] The structure of the separation membrane of the present application is not particularly limited as long as it has the above-described separation layer, and for example, the structure shown in the following can be exemplified. Figure 1 Figure 1 A schematic cross-sectional view of the separation membrane 10 involved in one embodiment of the present application is shown in the following. The separation membrane 10 is constituted of a support 11, an intermediate layer 12 formed on the support 11, and a separation layer 13 formed on the intermediate layer 12.

[0052] (Support)

[0053] In order to improve the mechanical strength and shape stability of the separation membrane 10, it is preferable that the separation membrane 10 includes the support 11. The support 11 preferably has both the support function of the separation layer 13 and the liquid permeability. As a specific example of such a support, a porous support can be exemplified.

[0054] The material of the support is not particularly limited, but for example, ceramics such as α-alumina (AI2O3), silica (SiO2), and zirconia (ZrO2) can be exemplified.

[0055] The shape of the support is also not particularly limited, but for example, a tubular shape, a cylindrical shape, a plate shape, and the like can be exemplified.

[0056] The average pore diameter of the porous support is not particularly limited, but it is preferably 1 μm or less, and more preferably 100 nm or less. In addition, the average pore diameter of the porous support is preferably 0.1 nm or more, more preferably greater than 2 nm, further preferably greater than 3 nm, and particularly preferably greater than 5 nm. As long as it is a porous support having such an average pore diameter, both the support function of the separation layer and the liquid permeability are favorably possessed, and the CO2 permeability and the gas selectivity of the separation layer are not affected. In the present application, the average pore diameter is a value measured using a Nano Palm Porometer.

[0057] The thickness of the support is not particularly limited, and it is preferably 0.5 to 5 mm, and more preferably 1 to 3 mm.

[0058] (Intermediate Layer)

[0059] ​The separation membrane 10 preferably has an intermediate layer 12 between the separation layer 13 and the support 11. The raw material of the intermediate layer is not particularly limited, but for example, particles of metal oxides such as alumina, silica, zirconia, mixtures of these, and the like can be cited. The average particle diameter of the metal oxide particles is not particularly limited, and can be selected from the range conventionally known to be able to form the desired average pore diameter.

[0060] The intermediate layer 12 can be formed by appropriately applying a colloidal sol containing these particles to the surface of the support 11, and performing firing. By providing such an intermediate layer, the surface of the support is homogenized, and at the same time, the difference in the coefficient of thermal expansion between the support and the separation layer is moderated, and the shape stability of the separation membrane is improved.

[0061] The average pore diameter of the intermediate layer 12 is not particularly limited, and is preferably smaller than the average pore diameter of the support 11, and larger than the average pore diameter of the separation layer 13, and for example, is preferably 0.5 to 5 nm, more preferably 0.5 to 3 nm, and even more preferably 1 to 2 nm.

[0062] The thickness of the intermediate layer is not particularly limited, and is preferably 1 to 1000 nm.

[0063] In the present embodiment, the intermediate layer is one layer, but can also be two or more layers. In the case where two or more intermediate layers are formed, the same raw material can be used, or different raw materials can be used. Further, the intermediate layer can not be provided.

[0064] (Separation Layer)

[0065] The separation layer 13 is formed on the support 11 directly or via the intermediate layer 12, and separates target substances using pores that allow the target substances to pass through. The separation layer contains (A) a polymer having an isocyanuric acid skeleton and a siloxane bond, and (B) metal ions, and has an amorphous structure. The metal ions contained in the separation layer and the nitrogen atoms from the isocyanuric acid skeleton in the polymer form coordinate bonds, with the metal ions serving as electron acceptors and the nitrogen atoms serving as electron donors, respectively. By combining the nitrogen atoms that are electron donors in the polymer having a siloxane bond with carbon atoms that have a smaller electronegativity than the nitrogen atoms, a shift in charge occurs between the nitrogen atoms and the carbon atoms, and the formation of coordinate bonds is promoted.

[0066] The separation layer 13 preferably forms a network structure in which the siloxane bonds are combined in a network (hereinafter also referred to as "siloxane network"), and a network structure in which the nitrogen atoms in the isocyanuric acid skeleton are coordinated with the metal ions (hereinafter also referred to as "coordinate bond network"). By using a separation layer in which such a siloxane network and coordinate bond network are formed, a large number of pores that selectively allow CO2 to pass through are formed, and thus a separation membrane having excellent CO2 permeability and CO2 / N2 selectivity can be obtained.

[0067] [Component (A)]

[0068] The component (A) is a polymer having an isocyanuric acid skeleton and a siloxane bond (hereinafter also referred to as "polymer (A)").

[0069] As the component (A), there is no particular limitation as long as it has the above structure, and, for example, a polymer obtained by polymerizing a precursor containing a compound represented by the following general formula (1) (hereinafter also referred to as "compound (1)") is preferred.

[0070] [Chemical Formula 5]

[0071]

[0072] (In the formula, X's are each independently a group represented by the following formula (2) or a monovalent hydrocarbon group having 1 to 8 carbon atoms, and at least one of X's is a group represented by the following formula (2).)

[0073] [Chemical Formula 6]

[0074]

[0075] (In the formula, R 1 is an alkylene group having 1 to 8 carbon atoms, R 2 's are each independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, R 3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 3. The line with a wavy line indicates a binding end.)

[0076] In formula (1), the monovalent hydrocarbon group having 1 to 8 carbon atoms as X can be linear, branched, or cyclic, and as specific examples thereof, there can be mentioned linear or branched alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, and the like; cyclic alkyl groups such as cyclopentyl group, cyclohexyl group, and the like; alkenyl groups such as vinyl group, allyl group, 3-butenyl group, 5-hexenyl group, 7-octenyl group, and the like; aryl groups such as phenyl group, and the like, among which X is preferably a group having 1 to 3 carbon atoms, and more preferably vinyl group or allyl group, and further preferably allyl group.

[0077] However, at least one of X's is a group represented by the above formula (2), and X's are preferably all groups represented by the above formula (2).

[0078] In formula (2), as the alkylene group having 1 to 8 carbon atoms as R 1 , there can be mentioned methylene group, ethylene group, trimethylene group, propylene group, tetramethylene group, hexamethylene group, octamethylene group, and the like, among which R 1 is preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an alkylene group having 3 carbon atoms, and further preferably trimethylene group.

[0079] as R 2 A monovalent hydrocarbon group having 1 to 8 carbon atoms, the same groups exemplified in X can be exemplified, wherein R 2 A group having 1 to 6 carbon atoms is preferable, and a methyl group, a vinyl group, a phenyl group are more preferable.

[0080] A monovalent hydrocarbon group having 1 to 8 carbon atoms, the same groups exemplified in X can be exemplified, wherein R 3 As a specific example of an alkyl group having 1 to 4 carbon atoms, straight chain, branched chain are both possible, and as a specific example thereof, a straight chain or branched chain alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, and the like can be exemplified, wherein R 3 A methyl group or an ethyl group is preferable, and a methyl group is further preferable.

[0081] n is an integer of 1 to 3, and 3 is preferable.

[0082] As a specific example of the compound (1), for example, tris[3-(trimethoxysilyl)propyl]isocyanurate (TTPI), allyl bis[3-(trimethoxysilyl)propyl]isocyanurate, diallyl[(3-trimethoxysilyl)propyl]isocyanurate, and the like can be exemplified, wherein tris[3-(trimethoxysilyl)propyl]isocyanurate is preferable.

[0083] Further, the compound (1) can be used alone as one kind, or two or more kinds can be used in combination.

[0084] The polymer of the component (A) can be obtained by hydrolytic condensation of a precursor containing the compound (1). Further, the precursor can contain, within a range not impairing the effects of the present application, a compound other than the compound (1) that can be hydrolytically condensed, and as such a compound, for example, a silane compound having a hydrolyzable group, and the like can be exemplified.

[0085] As the silane compound having a hydrolyzable group, there is no particular limitation as long as it is a silane compound having 1 to 4 chlorine groups or alkoxy groups as hydrolyzable groups on a silicon atom.

[0086] As specific examples thereof, tetra- chlorosilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiisopropoxysilane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylisopropoxysilane, ethyltrichlorosilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrichlorosilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrichlorosilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrichlorosilane, hexyltrimethoxysilane, hexyltriethoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, cyclohexyltrichlorosilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, propylmethyldichlorosilane, propylmethyldimethoxysilane, propylmethyldiethoxysilane, hexylmethyldichlorosilane, hexylmethyldimethoxysilane, hexylmethyldiethoxysilane, phenylmethyldichlorosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, diphenyldichlorosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, dimethylphenylchlorosilane, dimethylphenylmethoxysilane, dimethylphenylethoxysilane, and partial hydrolysates thereof, and the like can be given, but from the viewpoint of workability, easiness of distilling off of a by-product, and easiness of obtaining of a raw material, methoxysilane, ethoxysilane is preferred.

[0087] Further, the above silane compound can be used alone or two or more kinds thereof can be used in combination.

[0088] The proportion of the compound (1) in the precursor is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 100 mol% with respect to the total number of moles of the precursor.

[0089] [ (B) Component]

[0090] The (B) component is a metal ion, and as the metal, nickel, copper, silver, cobalt, zinc, and the like (as the metal ion, Ni 2+ , Cu 2+ , Ag + , Co 2+ , Zn 2+ , and the like) can be given, and one kind thereof can be used alone or two or more kinds thereof can be used in combination, but nickel is preferred.

[0091] From the viewpoint of the CO2 / N2 selectivity of the separation membrane, the molar ratio of the metal ion to the nitrogen atom from the isocyanuric acid skeleton in the polymer (A) in the separation layer (metal ion / nitrogen atom) is preferably 0.01 or more and 0.75 or less, more preferably 0.10 or more and 0.60 or less, further preferably 0.125 or more and 0.50 or less. Furthermore, from the viewpoint of taking into account the CO2 permeability of the separation membrane, most preferably 0.125 or more and 0.25 or less.

[0092] The average pore diameter of the separation layer is not particularly limited, and is preferably smaller than the average pore diameter of the intermediate layer, for example, preferably less than 1 nm, more preferably less than 0.5 nm. The lower limit is not particularly limited, and is preferably 0.1 nm or more.

[0093] The thickness of the separation layer is preferably 100 nm or more and 1000 nm or less. If the separation layer is 1000 nm or less, the separation efficiency is excellent because a long time or a high pressure is not required for the separation of CO2. In addition, if the separation layer is 100 nm or more, the permeation of a gas other than CO2 is suppressed, and thus the CO2 selectivity is further improved.

[0094] (2) Method for producing a separation membrane

[0095] A method for producing a separation membrane according to the present application will be described below. As the method for producing a separation membrane according to the present application, a method including the following steps is exemplified, for example, as long as a separation membrane having the above-described separation layer is obtained.

[0096] (I) Metal-doped polymer sol preparation step of preparing a metal-doped polymer sol containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) a metal ion

[0097] (II) Coating step of coating the above-described metal-doped polymer sol directly or via an intermediate layer on a porous support

[0098] (III) Firing step of firing the above-described metal-doped polymer sol coated in the above-described coating step to form a separation layer having an amorphous structure

[0099] Step (I): Metal-doped polymer sol preparation step

[0100] This step is a step of preparing a metal-doped polymer sol containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) a metal ion.

[0101] The metal-doped polymer sol can be obtained by mixing a sol of (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) a metal salt that is a supply source of a metal ion.

[0102] The sol of the polymer (A) is preferably obtained by hydrolysis condensation of a precursor containing the compound (1). In this case, the sol of the polymer (A) can be prepared by dispersing the obtained polymer (A) in a solvent after the polymer (A) is synthesized by the hydrolysis condensation in advance, or a sol containing the polymer (A) after the hydrolysis condensation reaction is completed can be directly used. In the present application, the sol containing the polymer (A) after the hydrolysis condensation reaction is completed is preferably directly used.

[0103] When the hydrolysis condensation is performed, a hydrolysis catalyst can be used. As the hydrolysis catalyst, conventionally known catalysts can be used, and a catalyst (acidic catalyst) whose aqueous solution shows acidity of pH 2 to 7 is preferably used, and a solid acid such as acidic or weakly acidic inorganic salt, ion exchange resin, hydrogen halide, sulfonic acid, carboxylic acid, or the like is particularly preferably used.

[0104] As specific examples of the acidic catalyst, hydrogen fluoride, hydrochloric acid, nitric acid, sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, formic acid, acetic acid, maleic acid, benzoic acid, lactic acid, phosphoric acid, cation exchange resin having sulfonic acid or carboxylic acid group on the surface, or the like can be given.

[0105] The amount of the hydrolysis catalyst used is not particularly limited, and 0.0002 to 0.5 mol per 1 mol of silicon atoms in the precursor is preferable in order to make the reaction proceed rapidly while considering the ease of removal of the catalyst after the reaction.

[0106] The amount of water required for the hydrolysis condensation reaction is not particularly limited, and 0.1 to 200 mol of water per 1 mol of silicon atoms in the precursor is preferable in order to make the reaction sufficiently proceed while preventing deactivation of the catalyst.

[0107] The reaction temperature at the time of the hydrolysis condensation is not particularly limited, and -10 to 150°C is preferable in order to improve the reaction rate while preventing decomposition of the organic functional group. The reaction time is not particularly limited, but 0.5 to 24 hours is preferable.

[0108] Further, an organic solvent can be used at the time of the hydrolysis condensation. As specific examples of the organic solvent that can be used, methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, xylene, or the like can be given.

[0109] Next, a metal-doped polymer sol is prepared by adding a metal salt to the obtained sol of the polymer (A) and stirring.

[0110] As the metal salt, a metal salt that becomes a supply source of the metal ion of the component (B) is used, and as specific examples thereof, for example, metal salts of the metal ions of the components (B) listed in Table 1 can be given.

[0111] As for the amount of the metal salt to be added, the metal ion is added in a molar ratio (metal ion / nitrogen atom) to the nitrogen atom from the isocyanuric acid skeleton in the polymer (A) in a range described above.

[0112] From the viewpoint of efficiently producing a uniform separation layer, the concentration of the metal-doped polymer in the metal-doped polymer sol is preferably 0.1 to 0.5 mass %.

[0113] Further, in the case where the intermediate layer is provided in the separation membrane of the present application, the intermediate layer forming step can be performed after the metal-doped polymer sol preparation step, or can be performed before the metal-doped polymer sol preparation step. Alternatively, the metal-doped polymer sol preparation step and the intermediate layer forming step can be performed in parallel.

[0114] As the intermediate layer forming step, for example, the following method can be mentioned: after forming the first intermediate layer by coating the surface of the support 11 with the SiO2-ZrO2 sol mixed with the α-alumina particles and firing, further coating the first intermediate layer with the SiO2-ZrO2 sol and firing to form the second intermediate layer, thereby forming the intermediate layer 12 on the support 11.

[0115] The firing conditions in the intermediate layer forming step are preferably set to, for example, a firing temperature of 400 to 600°C, preferably 400 to 500°C, and a firing time of 10 to 30 minutes in the air.

[0116] Step (II): Coating step

[0117] This step is a step of coating the metal-doped polymer sol obtained in the above step (I) on a porous support directly or via an intermediate layer.

[0118] The coating method and the coating amount are not particularly limited, and can be appropriately selected from known methods such as a dipping method, a brush coating, and the like, and the coating is preferably performed to a desired thickness.

[0119] Step (III): Firing step

[0120] This step is a step of firing the metal-doped polymer sol coated in the above coating step to form a separation layer.

[0121] The firing conditions are, for example, preferably a firing temperature of 200 to 400°C and a firing time of 30 to 60 minutes in a non-active gas atmosphere such as nitrogen or argon. If the range is such, the CO2 permeability and the CO2 / N2 selectivity of the separation membrane can be further improved.

[0122] Example

[0123] The following synthesis examples, comparative synthesis examples, examples, and comparative examples more specifically illustrate the present application, but the present application is not limited by the following examples.

[0124] [Synthesis Examples 1 to 3, Comparative Synthesis Example 1]

[0125] Step (I):

[0126] To TTPI (KBM-9659: manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in ethanol, water and nitric acid were added to cause hydrolysis and condensation of TTPI. At this time, the molar ratio was TTPI / H2O / HNO3 = 1 / 300 / 1. Then, by stirring at 25°C for 12 hours, a sol of the hydrolysis condensate of TTPI (TTPI sol) was prepared. In addition, the concentration of the TTPI sol was prepared to be 5 mass% using ethanol.

[0127]

[0128] At this time, nickel-doped TTPI sols in which the molar ratio of nickel to nitrogen atoms in TPPI (Ni / N) was 0.125 (Ni-TPPI 0.125: Synthesis Example 1), 0.25 (Ni-TPPI 0.25: Synthesis Example 2), and 0.50 (Ni-TPPI 0.50: Synthesis Example 3) were prepared. In addition, as a TPPI sol to which no metal salt was added, a sol (TTPI: Comparative Synthesis Example 1) in which the TPPI sol obtained in the above-mentioned Step (I) was diluted to 0.1 mass% using ion exchange water was prepared.

[0129] (Properties of nickel-doped TTPI sols)

[0130]

[0131] The nickel-doped TTPI sols and the TTPI sol were detected to have peaks in the range of 200 to 212 nm indicating ligand internal migration (n→σ*) of the free electron of the amino group. In the nickel-doped TTPI sol, two peaks at 400 nm and 600 nm were detected. In addition, as the nickel ratio increased, the two peaks at 400 nm and 600 nm shifted to the high wavelength side due to a change in the state of the free electron of the amino group.

[0132] In Figure 2 The measurement results by Fourier transform infrared spectroscopy (FT-IR) (wavelength 500 to 2000 cm -1 The nickel-doped TTPI sols obtained in the above-mentioned Synthesis Examples 1 to 3 and the TTPI sol obtained in Comparative Synthesis Example 1 were each coated on a KBr plate, fired at 250°C under a N2 atmosphere, and then measured using a Fourier transform infrared spectrophotometer FT / IR-4100 (manufactured by JASCO Corporation).

[0133] isocyanuric acid skeleton shows a peak at a wave number of 1550 to 1650 cm -1 with an increase in the amount of nickel doping, a peak becomes broad and large in intensity at a wave number of 1610 to 1620 cm -1 It is considered that this is because the coordination bonding of the amino group with the metal ion is promoted by the hydrolysis and condensation reaction of TTPI.

[0134] In Figure 2 (c) and (d) show the results of X-ray photoelectron spectroscopy (XPS) measurement. The nickel-doped TTPI sol obtained in Synthesis Examples 1 to 3 and the TTPI sol obtained in Comparative Synthesis Example 1 were each coated on a silicon wafer, and after firing at 250°C, measurement was performed using an X-ray photoelectron spectrometer (ESCA 3400-HSE manufactured by Shimadzu Corporation).

[0135] As shown in Figure 2 (c), the peak of the N (1s) bond energy shifts due to nickel doping, and the increase in the bond energy is considered to be due to nitrogen as an electron donor for coordination bonding.

[0136] In addition, as shown in Figure 2 (d), in the Ni (2p) bond energy of the nickel-doped TTPI (Ni-TPPI 0.25) containing the nitrogen atom coordinated to nickel, two peaks at 874 eV and 857 eV are considered to be due to the presence of Ni-OH.

[0137] From the measurement results obtained by UV-Vis, FT-IR, and XPS, it was found that coordination bonding was formed between the isocyanuric acid skeleton and the nickel ion in all of the nickel-doped TTPI sols having different nickel ratios.

[0138] (Properties of nickel-doped TTPI powder)

[0139] The nickel-doped TTPI sol obtained in Synthesis Examples 1 to 3 and the TTPI sol obtained in Comparative Synthesis Example 1 were dried at 180°C, pulverized, and fired at 250°C for 30 minutes under a N2 atmosphere. Then, for the resulting powder, property evaluation was performed using X-ray diffraction (XRD) and a transmission electron microscope (TEM) photographic image.

[0140] Note that the XRD analysis was performed using an XRD D2 PHASER (manufactured by Bruker Corporation), and the transmission electron microscope was a TEM JEOL2010 (manufactured by JEOL Ltd.).

[0141] In Figure 3(a) shows the results of measurement by XRD of the calcined nickel-doped TTPI powder and the TTPI powder. At 8° and 20° in the 2θ angle, broad peaks characteristic of the siloxane network (Si-O-Si) are shown, and in the nickel-doped TTPI powder, a peak of Ni(OH)2is observed at 15°.

[0142] It is known that as the Ni / N molar ratio increases, the first peak at 8° shifts to lower angles, and the second peak at 20° becomes broader, and thus a more amorphous structure is formed.

[0143] In Figure 3 (b) shows TEM images of the calcined nickel-doped TTPI powder and the TTPI powder. The upper row is a low-resolution TEM image, and the lower row is a high-resolution TEM image. In the case where the nickel ratio is 0.25 or more, the nickel is distributed unevenly, and a large number of dark spots representing non-coordinated nickel that does not form a coordination bond with the amino group are confirmed.

[0144] In Figure 4 N2adsorption isotherms (-196°C) of the calcined nickel-doped TTPI powder and the TTPI powder are shown in (c). Note that the measurement was performed using a BELMAX (manufactured by BEL JAPAN Co., Ltd.). In addition, from the N2adsorption / desorption isotherm, the results of calculation of the BET (Brunauer-Emmett-Teller) specific surface area and the total pore volume are shown in Table 1.

[0145] [Table 1]

[0146]

[0147] As shown in Table 1, the nickel-doped TTPI powder has a larger BET specific surface area and a larger total pore volume than the TTPI powder. In these metal-doped TTPI powders, pores are formed by coordination bonds between the amino group within the TTPI molecule as an electron donor and the metal ion as an electron acceptor.

[0148] In addition, the BET specific surface area and the total pore volume become the largest in the case of the Ni-TTPI0.25powder, and on the other hand, if the Ni / N ratio is further increased to 0.5, both the surface area and the pore volume decrease. This is considered to be due to the aggregation of excess nickel that does not form a coordination bond with the TTPI to form nanoparticles, which obstructs the pore structure. In Figure 5 The mechanism of formation of the Ni-TTPI network at Ni / N molar ratios of 0, 0.25, and 0.50 is schematically shown in (d).

[0149] In Figure 6CO2adsorption-desorption isotherms of the calcined nickel-doped TTPI powder and the TTPI powder are shown in the middle. The sample of Ni-TTPI0.25showed higher CO2adsorptivity than TPPI or the nickel-doped powder at a low concentration. On the other hand, under the same conditions, Ni-TTPI0.50formed a result of low CO2adsorption capacity due to the blockage of the fine pores by the uncoordinated nickel particles.

[0150] [Example 1]

[0151] (intermediate layer forming step)

[0152] As the porous support, an α-alumina tube (manufactured by Nikkato Corporation, 100 mm in length, 8 mm in inner diameter, and 10 mm in outer diameter) was used.

[0153] The α-alumina particles having a number average particle diameter of 0.2 μm and the α-alumina particles having a number average particle diameter of 2 μm were mixed with SiO2-ZrO2sol (number average particle diameter: about 10 nm, 2.0 mass%), and a dispersion liquid diluted with ion-exchange water to 10 mass% was applied to the outer surface of the porous support, which was naturally dried, and the excess particles were wiped off, and calcination was performed at 550°C under the atmosphere for 15 minutes. The application and calcination of the above dispersion liquid were repeated three times, and thus the first intermediate layer was formed.

[0154] Next, SiO2-ZrO2sol (number average particle diameter: about 10 nm, 0.5 mass%) was applied to the above first intermediate layer, and calcination was performed at 550°C under the atmosphere for 10 minutes. By repeating the application and calcination of the SiO2-ZrO2sol until the average fine pore diameter measured by Nano Palm Porometer became 1 nm or more and 2 nm or less, the second intermediate layer was formed, and thus the first and second intermediate layers were sequentially formed on the outer surface of the support.

[0155] Step (II):

[0156] Next, as the application step, the 0.1 mass% nickel-doped TTPI sol (Ni-TPPI0.125) obtained in the above Synthesis Example 1 was applied to the second intermediate layer.

[0157] Step (III):

[0158] Next, as the calcination step, the product in which the nickel-doped TTPI sol was applied to the second intermediate layer formed on the support in the above Step (II) was calcined at 250°C under a N2atmosphere for 30 minutes, and thus a separation layer was formed, and a separation membrane was manufactured.

[0159] [Example 2]

[0160] In the process (II), the 0.1 mass% nickel-doped TTPI sol obtained in the above Synthesis Example 1 was changed to the 0.1 mass% nickel-doped TTPI sol (Ni-TPPI 0.25) obtained in the above Synthesis Example 2, and a separation membrane was produced by the same procedure as in Example 1 except for this.

[0161] [Example 3]

[0162] In the process (II), the 0.1 mass% nickel-doped TTPI sol obtained in the above Synthesis Example 1 was changed to the 0.1 mass% nickel-doped TTPI sol (Ni-TPPI 0.50) obtained in the above Synthesis Example 3, and a separation membrane was produced by the same procedure as in Example 1 except for this.

[0163] [Comparative Example 1]

[0164] In the process (II), the 0.1 mass% nickel-doped TTPI sol obtained in the above Synthesis Example 1 was changed to the 0.1 mass% TTPI sol (TPPI) obtained in the above Comparative Synthesis Example 1, and a separation membrane was produced by the same procedure as in Example 1 except for this.

[0165] The permeability of the separation membranes obtained in Examples 1 to 3 and Comparative Example 1 was evaluated for helium, hydrogen, carbon dioxide, nitrogen, methane, carbon tetrafluoride and sulfur hexafluoride. The permeation gas was supplied at a pressure of 200 to 400 kPa from the separation layer 13 side of the separation membrane (Example 1) and the separation layer 13 side of the separation membrane (Example 2) and the separation layer 13 side of the separation membrane (Example 3) and the separation layer 13 side of the separation membrane (Comparative Example 1) at 200°C, and the permeability was evaluated. Further, the permeation flow rate was measured using a membrane flow meter (manufactured by Horiba, Ltd.). Figure 1

[0166] The relationship between the size of the gas molecules and the gas permeability is shown in Table 1. As the size of the permeation gas molecules becomes larger, the permeability decreases. Therefore, it is considered that the gas separation by the separation membranes obtained in Examples 1 to 3 utilizes molecular sieving. Figure 7 The separation membrane using Ni-TTPI 0.25 (Example 2) is porous compared with the separation membrane using TPPI (Comparative Example 1) or the separation membrane using Ni-TTPI 0.125 (Example 1), and thus the gas permeability is further improved. On the other hand, in the case of using Ni-TTPI 0.50 (Example 3), the gas permeability is low, and the membrane structure becomes dense due to the occlusion of the fine pores generated by the nickel particles, which is consistent with the results of the CO2 adsorption of the Ni-TTPI particles described above.

[0167] The permeability of the separation membranes obtained in Examples 1 to 3 and Comparative Example 1 was evaluated for helium, hydrogen, carbon dioxide, nitrogen, methane, carbon tetrafluoride and sulfur hexafluoride. The permeation gas was supplied at a pressure of 200 to 400 kPa from the separation layer 13 side of the separation membrane (Example 1) and the separation layer 13 side of the separation membrane (Example 2) and the separation layer 13 side of the separation membrane (Example 3) and the separation layer 13 side of the separation membrane (Comparative Example 1) at 200°C, and the permeability was evaluated. Further, the permeation flow rate was measured using a membrane flow meter (manufactured by Horiba, Ltd.).

[0168] Figure 8 ​​Temperature dependences of the gas permeabilities of CO2, N2 and the CO2 / N2 permeation selectivity are shown in FIG. 1. (a) to (d) are results obtained using the separation membranes of Comparative Example 1 and Examples 1 to 3, respectively.

[0169] In all of the separation membranes, the higher the measurement temperature T, that is, the lower the reciprocal of the measurement temperature T (1 / T), the higher the permeation rate of N2. It is presumed that this is because (1) the siloxane network of the separation membrane vibrates due to heat, thereby increasing the pore size of the separation membrane, and (2) the kinetic energy of N2 molecules increases, thereby promoting the diffusion of N2 molecules. Thus, the gas permeation mechanism in which the higher the measurement temperature T, the higher the permeation rate is called "activated diffusion".

[0170] On the other hand, with respect to CO2, the higher the Ni / N molar ratio in the Ni-TTPI separation layer, the higher the CO2 permeation rate at low temperatures, presumably because the gas permeation mechanism called "surface diffusion" becomes dominant.

[0171] In surface diffusion, CO2 molecules are adsorbed on the surface of the CO2 separation membrane, thereby creating a gradient of CO2 concentration from the upstream side to the downstream side of the separation membrane, and the molecules move two-dimensionally along the concentration gradient. The lower the measurement temperature T, the lower the energy of CO2 molecules, and the CO2 molecules are easily adsorbed on the surface of the separation membrane, and thus the diffusion movement along the concentration gradient is promoted. Therefore, in surface diffusion, the higher the measurement temperature T, the lower the permeation rate.

[0172] The CO2 / N2 permeation selectivity of the separation membranes obtained in Examples 1 to 3 greatly increases as the temperature decreases from high to low. It is presumed that this is because the gas permeation mechanism of N2 is activated diffusion, and the lower the temperature, the lower the permeation rate, and in the gas permeation mechanism of CO2 in the Ni-TTPI separation layer, the contribution of surface diffusion, in which the permeation rate increases as the temperature decreases, is greater due to the increase in the nickel coordination of the amine to the isocyanuric acid skeleton.

[0173] Note that the present application is not limited to the above-described embodiments, and various modifications can be made within the scope of the patent claim, and embodiments obtained by appropriately combining the technical means disclosed in each of the embodiments are also included in the technical scope of the present application.

[0174] Explanation of Reference Numerals

[0175] 10 separation membrane

[0176] 11 support

[0177] 12 intermediate layer

[0178] 13 separation layer

Claims

1. A separation membrane comprising a separation layer having an amorphous structure, the separation layer containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) metal ions.

2. The separation membrane according to claim 1, wherein, The (A) component is a polymer obtained by polymerizing a precursor containing a compound represented by the following general formula (1), [Chem. 1] wherein each X is independently a group represented by the following formula (2) or a monovalent hydrocarbon group having 1 to 8 carbon atoms, at least one of the X's being a group represented by the following formula (2), [Chem. 2] wherein R 1 is an alkylene group having 1 to 8 carbon atoms, R 2 each independently is a monovalent hydrocarbon group having 1 to 8 carbon atoms, R 3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n is an integer of 1 to 3, and the line with a wavy line indicates a bonding end.

3. The separation membrane according to claim 2, wherein, The (A) component is a polymer obtained by polymerizing a precursor containing tris[3-(trimethoxysilyl)propyl]isocyanurate.

4. The separation membrane according to any one of claims 1 to 3, wherein, The metal in the (B) component is one or more selected from the group consisting of nickel, copper, silver, cobalt, and zinc.

5. A method for producing a separation membrane, comprising: (I) a metal-doped polymer sol preparation step of preparing a metal-doped polymer sol containing (A) a polymer having an isocyanuric acid skeleton and a siloxane bond and (B) metal ions; (II) a coating step of coating the metal-doped polymer sol prepared in the metal-doped polymer sol preparation step directly or via an intermediate layer on a porous support; and (III) a firing step of firing the metal-doped polymer sol coated in the coating step to form a separation layer having an amorphous structure.

6. The method for producing a separation membrane according to claim 5, wherein The metal-doped polymer sol preparation step is performed by mixing a sol of the (A) polymer and a metal salt that is a supply source of the (B) metal ions.

7. The method for producing a separation membrane according to claim 5 or 6, wherein The (A) component is a polymer obtained by polymerizing a precursor containing a compound represented by the following general formula (1), [Chem. 3] wherein each X is independently a group represented by the following formula (2) or a monovalent hydrocarbon group having 1 to 8 carbon atoms, at least one of the X's being a group represented by the following formula (2), [Chem. 4] wherein R 1 is an alkylene group having 1 to 8 carbon atoms, R 2 each independently is a monovalent hydrocarbon group having 1 to 8 carbon atoms, R 3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 3.

8. The method for producing a separation membrane according to claim 7, wherein The (A) component is a polymer obtained by polymerizing a precursor containing tris[3-(trimethoxysilyl)propyl]isocyanurate.

9. The method for producing a separation membrane according to any one of claims 5 to 8, wherein The metal in the (B) component is one or more selected from the group consisting of nickel, copper, silver, cobalt, and zinc.

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