Ammonia separation membrane and ammonia separation method using same

Abstract

The purpose of the present invention is to provide: an ammonia separation membrane having a different composition from conventional ammonia separation membranes; and an ammonia separation method using the ammonia separation membrane. The present invention is an ammonia separation membrane characterized by comprising a metal cyanide complex represented by formula (1) and a porous oxide body, the porous oxide body having an amorphous pore shape. AxM1 [M2 (CN) w] y.zH2O (1) [In the formula, M1 and M2 represent metal atoms such as vanadium, A represents atoms such as hydrogen, x represents 0-4, y represents 0.1-2, z represents 0-6, and w represents a numerical value of 4-8. ]

Description

Technical Field

[0001] The present invention relates to an ammonia separation membrane and an ammonia separation method using the same. Background Art

[0002] Ammonia is required to be managed in various fields. For example, in semiconductor manufacturing or inside fuel cells, there is a need to remove ammonia as an impurity, and in the Haber-Bosch method, which is a method of synthesizing ammonia from nitrogen and hydrogen, there is a need to separate the generated ammonia from the mixed gas with the raw material gas.

[0003] For example, Patent Document 1 describes a method for separating ammonia by selectively permeating ammonia from a mixed gas containing at least ammonia, hydrogen, and nitrogen using a zeolite membrane. In addition, Patent Document 2 discloses an ammonia separation method, which includes a membrane separation step for separating at least one component among hydrogen, nitrogen, and ammonia using a gas separation membrane having a silicon dioxide-containing layer stacked on a ceramic substrate.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2018 / 230737 Pamphlet

[0007] Patent Document 2: Japanese Patent Application Publication No. 2008-247654 Summary of the invention

[0008] Problems to be solved by the invention

[0009] An object of the present invention is to provide an ammonia separation membrane having a composition different from that of conventional ammonia separation membranes such as those disclosed in Patent Documents 1 and 2, and an ammonia separation method using the same.

[0010] Means for solving problems

[0011] The present invention which has achieved the above-mentioned object is as follows.

[0012] [1] An ammonia separation membrane comprising a metal cyanide complex represented by the following formula (1) and an oxide porous body,

[0013] The pore shape of the above-mentioned oxide porous body is amorphous.

[0014] A x M 1 [M 2 (CN) w ] y ·zH2O(1)

[0015] [Wherein,

[0016] M 1 represents one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium and calcium,

[0017] M 2 represents one or more metal atoms selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum and copper,

[0018] A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium,

[0019] x represents 0 to 4, y represents 0.1 to 2, z represents 0 to 6, and w represents a value of 4 to 8. ]

[0020] [2] The ammonia separation membrane according to [1], wherein the oxide porous body has two or more layers having different pore diameters.

[0021] [3] The ammonia separation membrane according to [1] or [2], wherein the oxide porous body has two or more layers having different pore diameters,

[0022] The metal cyanide complex is formed inside the layer (S1) having the smallest average pore diameter and / or adjacent to the layer (S1).

[0023] [4] The ammonia separation membrane according to any one of [1] to [3], wherein the outermost layer on one side of the oxide porous body is a layer (S1) having the smallest average pore diameter.

[0024] [5] The ammonia separation membrane according to any one of [1] to [4], wherein the average pore diameter of the layer (S1) having the smallest average pore diameter is 0.5 μm or less.

[0025] [6] An ammonia separation membrane according to any one of [1] to [5], wherein the metal cyanide complex is formed inside the layer having an average pore diameter of 0.5 μm or less of the oxide porous body and / or on the surface of the layer having an average pore diameter of 0.5 μm or less.

[0026] [7] A method for producing an ammonia separation membrane comprising a metal cyanide complex represented by the following formula (1) and an oxide porous body, wherein:

[0027] The porous oxide body has an amorphous pore shape and has two or more layers with different pore diameters.

[0028] The method comprises the following steps:

[0029] Containing A p [M 2 (CN) w ] and an aqueous solution Sa containing one or more metals selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium and calcium, namely M 1 A step of impregnating at least one of the solutions Sb of a hydrophobic solvent of the above-mentioned oxide porous body with the smallest average pore diameter (S1) or the layer with an average pore diameter of 0.5 μm or less, wherein A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, and M 2 represents one or more metal atoms selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum and copper, p represents a value of 1 to 4, and w represents a value of 4 to 8; and

[0030] A process of bringing a layer (S1) having the smallest average pore diameter or a layer having an average pore diameter of less than 0.5 μm of the oxide porous body impregnated with any one of the aqueous solution Sa and the solution Sb in the impregnation process into contact with another solution of the aqueous solution Sa and the solution Sb other than the solution used in the impregnation process.

[0031] A x M 1 [M 2 (CN) w ] y ·zH2O(1)

[0032] [In the formula, A, M 1 、M 2 , w are the same as above. x represents a value of 0 to 4, y represents a value of 0.1 to 2, and z represents a value of 0 to 6.]

[0033] [8] A method for producing an ammonia separation membrane comprising a metal cyanide complex represented by the following formula (1') and an oxide porous body, wherein:

[0034] The porous oxide body has an amorphous pore shape and has two or more layers with different pore diameters.

[0035] The method comprises the following steps:

[0036] Make Fe 3+ [Fe 3+ A step of impregnating at least the layer (S1) with the smallest average pore diameter or the layer with an average pore diameter of 0.5 μm or less in the above-mentioned oxide porous body with an aqueous solution of a metal cyanide complex represented by (CN)6]; and

[0037] The metal cyanide complex Fe 3+ [Fe 3+ The step of reducing the above-mentioned porous oxide body in an aqueous solution of (CN)6].

[0038] A x M 11 [M 21 (CN)6] y ·zH2O(1')

[0039] [wherein, A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, and M 11 and M 21 is iron (III), x represents a value of 0 to 4, y represents a value of 0.1 to 2, and z represents a value of 0 to 6.]

[0040] [9] The method according to [8], wherein the reduction treatment is a treatment using a reducing gas atmosphere.

[0041]

[10] The method according to [8], wherein the reduction treatment is a treatment using light.

[0042]

[11] An ammonia separation method, comprising: selectively permeating ammonia from a mixed gas containing ammonia using the ammonia separation membrane according to any one of [1] to [6].

[0043] Effects of the Invention

[0044] According to the present invention, it is possible to provide an ammonia separation membrane having a composition different from that of Patent Documents 1 and 2 and an ammonia separation method using the same. In addition, according to the present invention, compared with Patent Documents 1 and 2, there are also the following preferred advantages: the number of steps in the separation membrane manufacturing is small, it can be manufactured from safe materials, or heating is not required and energy costs can be reduced, etc., and the ammonia separation membrane can be easily manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic diagram showing the crystal structure of a metal cyanide complex.

[0046] Figure 2 This is a photograph in lieu of a drawing showing a cross-sectional TEM image of the ammonia separation membrane of Example 1.

[0047] Figure 3 This is a photograph in lieu of a drawing showing a cross-sectional TEM image of the ammonia separation membrane of Example 2.

[0048] Figure 4 This is a photograph in lieu of a drawing showing a cross-sectional TEM image of an ammonia separation membrane made of the same raw material as in Example 1.

[0049] Figure 5 This is a diagram showing the results of analyzing the cross section of the ammonia separation membrane of Example 4 by EPMA. DETAILED DESCRIPTION

[0050] 1. Ammonia separation membrane

[0051] The ammonia separation membrane of the present invention is an oxide porous body on which a metal cyanide complex represented by a predetermined formula is formed, and the pore shape of the oxide porous body is amorphous. The oxide porous body and the metal cyanide complex are described below.

[0052] 1-1. Porous oxide body

[0053] The ammonia separation membrane of the present invention comprises an oxide porous body and a metal cyanide complex, and the metal cyanide complex is preferably formed in at least a portion of the oxide porous body. The oxide of the porous body is preferably a metal oxide, and specifically, B2O3, SiO2, GeO2, Al2O3, V2O5, As2O5, Sb2O5, ZrO2, TiO2, ZnO, PbO, ThO2, BeO, CdO, Ta2O5, Nb2O5, WO3, ScO2, La2O3, Y2O3, SnO2, Ga2O3, In2O3, PbO2, MgO, Li2O, BaO, CaO, SrO, Na2O, K2O, Rb2O, HgO, Cs2O, Ag2O, TeO2, Tl2O, Cr2O3 can be cited, and at least one of them is preferably included. The oxide porous body preferably contains at least Al2O3. It should be noted that in the present invention, the term "metal" is used to include semi-metals such as Si and Ge.

[0054] The porous oxide body may be composed of one layer or may have two or more layers having different pore diameters. The porous oxide body preferably has two or more layers having different pore diameters.

[0055] In the oxide porous body, the metal cyanide complex is preferably formed in a layer with a small pore diameter. By setting it in this way, the metal cyanide complex can be densely formed, and the ammonia separation performance can be improved. From this point of view, the metal cyanide complex is preferably formed in a layer of the oxide porous body with an average pore diameter of less than 0.5 μm. The metal cyanide complex is formed in a layer with an average pore diameter of less than 0.5 μm, including the metal cyanide complex formed inside the layer and / or adjacent to the layer. The metal cyanide complex is formed adjacent to the layer with an average pore diameter of less than 0.5 μm, which may be formed in contact with at least any surface of the layer, or in contact with a surface treatment layer formed on at least any surface of the layer. Preferably, the metal cyanide complex is formed in contact with at least any surface of the layer. In this case, when the oxide porous body is formed of one layer, the average pore diameter of the oxide porous body can be set to 0.5 μm or less. When the oxide porous body has two or more layers with different pore diameters, it is preferred to have at least one layer with an average pore diameter of 0.5 μm or less, and a metal cyanide complex is formed in at least one layer of the layers with an average pore diameter of 0.5 μm or less. The average pore diameter of the layer with the metal cyanide complex is preferably 0.3 μm or less, and the lower limit of the average pore diameter of the layer with the metal cyanide complex may be, for example, 0.001 μm or more.

[0056] In addition, when the oxide porous body has two or more layers with different pore diameters, it is also preferred that a metal cyanide complex is formed inside the layer (S1) with the smallest average pore diameter and / or adjacent to the layer (S1). The so-called metal cyanide complex formed adjacent to the layer (S1) may be formed in contact with at least one surface of the layer (S1), or in contact with a surface treatment layer formed on at least one surface of the layer (S1). Preferably, the metal cyanide complex is formed in contact with at least one surface of the layer. As the surface treatment layer, for example, sodium hexacyanoferrate (II), potassium hexacyanoferrate (III), polyethyleneimine, etc. can be listed.

[0057] It is further preferred that the layer (S1) having the smallest average pore diameter is the outermost layer on one side of the oxide porous body, and a metal cyanide complex is formed inside the layer (S1) and / or adjacent to the layer (S1). In this case, the metal cyanide complex is formed adjacent to the layer (S1), which may be formed in contact with the outer surface of the layer (S1), or may be formed via a surface treatment layer provided on the outer surface of the layer (S1).

[0058] The layer (S1) having the smallest average pore diameter preferably has the following average pore diameter, composition, and thickness, and it is preferred that these requirements are satisfied alone or in combination.

[0059] The average pore size of the layer (S1) is preferably 0.001 to 0.5 μm, more preferably 0.001 to 0.3 μm, further preferably 0.001 to 0.1 μm, and particularly preferably 0.001 to 0.05 μm. The average pore size of the layer (S1) can be measured by a capillary condensation method or a mercury intrusion method.

[0060] The layer (S1) is preferably at least one of Al2O3, ZrO2, SiO2, TiO2 and Y2O3, more preferably at least one of γ-Al2O3, ZrO2, SiO2 and TiO2, and further preferably γ-Al2O3.

[0061] The thickness of the layer (S1) is preferably 0.1 to 10 μm.

[0062] In addition, when the oxide porous body has two or more layers with different pore diameters, the layer (S1) with the smallest average pore diameter is the outermost layer on one side of the oxide porous body, and a metal cyanide complex is formed inside the layer (S1) and / or adjacent to the layer (S1), the two or more layers of the oxide porous body are preferably arranged in the order of the size of the average pore diameter. In this case, that is, the layer (S1) with the smallest average pore diameter is the outermost layer on one side of the oxide porous body, and the layer with the largest average pore diameter (hereinafter, layer (B1)) becomes the outermost layer on the other side.

[0063] Average pore size D of layer (B1) B1 For example, it is 0.1 μm or more, preferably 1.0 μm or more, more preferably 1.5 μm or more, further preferably 5 μm or more, further preferably 7 μm or more, and may be 300 μm or less, preferably 60 μm or less, and more preferably 20 μm or less. B1 For example, it is 0.1 to 300 μm, preferably 1.0 to 60 μm, more preferably 1.5 to 20 μm, further preferably 5 to 20 μm, and particularly preferably 7 to 20 μm. B1 For example, it can be measured by mercury intrusion porosimetry.

[0064] The thickness of the layer (B1) is, for example, 0.1 to 5 mm, or preferably 0.2 to 3 mm.

[0065] Furthermore, it is preferred that α-Al 2 O 3 be contained in the layer (B1), and it is particularly preferred that 50% or more of α-Al 2 O 3 be contained, and it is further preferred that 80% or more of α-Al 2 O 3 be contained.

[0066] It is preferred that one or more layers are further included between the layer (S1) having the smallest average pore diameter and the layer (B1) having the largest average pore diameter.

[0067] Specific examples of the layer in direct contact with layer (B1) (hereinafter referred to as layer (B2)) include Al2O3, ZrO2, SiO2, TiO2, Y2O3, etc., preferably Al2O3, and more preferably α-Al2O3.

[0068] The average pore diameter D2 of the layer (B2) directly in contact with the layer (B1) is, for example, 0.01 μm or more and 20 μm or less (0.01 to 20 μm), preferably 0.05 μm or more and 10 μm or less (0.05 to 10 μm), more preferably 0.1 μm or more and 5 μm or less (0.1 to 5 μm), and further preferably 0.15 μm to 5 μm.

[0069] In addition, the average pore size of the layer (S1) with the smallest average pore size, which is in direct contact with the side surface of the above-mentioned layer (B1), is, for example, 0.01μm to less than 0.15μm, and preferably exceeds 0.05μm to 0.14μm. The layer preferably contains Al2O3, more preferably contains α-Al2O3, and further preferably more than 80 mass% of the side surface of the layer (S1) is α-Al2O3.

[0070] The shape of the oxide porous body is not particularly limited, and may be planar, cylindrical, monolithic, or honeycomb, preferably cylindrical or monolithic. The outermost layer in the honeycomb shape refers to the outermost layer in the internal pores of the honeycomb.

[0071] In addition, the porous oxide body only needs to have an amorphous pore shape in at least a portion. In the case where the porous oxide body has two or more layers with different pore diameters, the pore shape of the layer (S1) with the smallest average pore diameter is preferably amorphous, or the pore shape of the layer with an average pore diameter of 0.5 μm or less is amorphous. In the case where the porous oxide body has two or more layers with different pore diameters, it is more preferred that a metal cyanide complex is formed in the layer (S1) with an amorphous pore shape, or a metal cyanide complex is formed in a layer with an amorphous pore shape and an average pore diameter of 0.5 μm or less. In addition, the amorphously formed pores are preferably pores formed by the aggregate structure of particles, and the pores are preferably not linear through holes, that is, the amorphous pores here cannot connect the entrance and exit of the pores in a straight line.

[0072] 1-2. Metal cyanide complex

[0073] The metal cyanide complex is represented by the following formula (1).

[0074] A x M 1 [M 2 (CN) w ] y·zH2O(1)

[0075] In the above formula (1),

[0076] M 1 represents one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium and calcium,

[0077] M 2 represents one or more metal atoms selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum and copper,

[0078] A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, and cesium,

[0079] x represents a value of 0 to 4, y represents a value of 0.1 to 2, z represents a value of 0 to 6, and w represents a value of 4 to 8.

[0080] The metal cyanide complex may contain a solvent other than water, other ions as impurities, or other materials not shown in the composition as impurities or a binder.

[0081] Metal cyanide complexes were identified 1 and M 2 In the case of 1 -M 2 Cyanide complex.

[0082] M 1 More preferably, it is one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, nickel, copper and zinc, further preferably, it is one or more metal atoms selected from the group consisting of manganese, iron, cobalt, nickel, copper and zinc, further preferably, it is one or more metal atoms selected from the group consisting of iron (especially iron (III)), zinc and cobalt.

[0083] M 2 Preferred are one or more metal atoms selected from the group consisting of manganese, iron, ruthenium, cobalt and platinum, more preferably one or more metal atoms selected from the group consisting of iron and cobalt, and most preferably iron.

[0084] A is preferably one or two or more atoms selected from the group consisting of sodium, ammonium, rubidium, cesium and potassium, and more preferably one or both of sodium and potassium.

[0085] x is preferably 0 to 2.5, more preferably 0 to 2. x may be greater than 0 and 2.5 or less, or greater than 0 and 2 or less.

[0086] y is preferably 0.4-1.3, more preferably 0.5-1.

[0087] When the value of y is small, it means that [M 2 (CN) w ] less, in this case, the metal M 1 becomes [M 2 (CN) w ] is present in excess. In this case, it becomes easy to 1 The structure of the surrounding adsorption ligands, especially the adsorption amount of NH3 increases.

[0088] z is preferably 0.5-5.5, more preferably 1-5.

[0089] With M 2 The number of coordinated cyano groups is generally 6 (ie, w is preferably 6), but a part of them may be substituted with nitro groups or the like, and there is no problem as long as the number of cyano groups is 4 to 8, ie, w is 4 to 8.

[0090] The crystal structure of metal cyanide complexes is generally Figure 1 The face-centered cubic structure shown in FIG. 1 is not necessarily limited thereto. The metal cyanide complex easily coordinates and adsorbs NH3 at the exposed metal part. In addition, it can be expected that NH3 is also adsorbed at the pore sites with a size of less than 1 nm contained inside. Since these adsorptions do not have a significant impact on its crystal structure, there is no large volume change caused by adsorption and desorption.

[0091] 2. Method for manufacturing ammonia separation membrane

[0092] The method for producing an ammonia separation membrane of the present invention comprises a step of producing a porous oxide body and a step of forming a metal cyanide complex in the porous oxide body.

[0093] 2-1. Production process of porous oxide body

[0094] When the oxide porous body consists of one layer (B1), for example, a commercially available alumina substrate containing alumina and SiO2 can be used, for example, alumina substrates A-12, A-13, A-16 etc. manufactured by Hagi Glass can be used.

[0095] In addition, in the case where the oxide porous body is composed of two layers, the oxide porous body preferably uses the above-mentioned commercially available alumina substrate as the first porous layer and has a layer (second porous layer) in contact with the first porous layer on at least one surface of the first porous layer. By applying a slurry containing a commercially available metal oxide and a solvent to form the second porous layer to at least one surface of the first porous layer, and performing a heat treatment at a temperature of about 500 to 1600°C for about 30 minutes to 10 hours, a laminated body in which the first porous layer and the second porous layer are stacked can be obtained. In the case where the oxide porous body is composed of three or more layers, it is sufficient to repeatedly apply a slurry containing a metal oxide and a solvent and perform a heat treatment. The method for applying the slurry is not particularly limited, and examples thereof include dip coating, spray coating, roller coating, rod coating, spin coating, slit coating, brush coating, and the like.

[0096] Examples of the solvent include water, an organic solvent, and a mixture thereof. The concentration of the metal oxide in the slurry is, for example, 2 mass % or more and 15 mass % or less.

[0097] 2-2. Metal cyanide complex formation step

[0098] (Method 1)

[0099] Metal cyanide complexes can be prepared by combining 2 Anionic metal cyanide complex (M 2 The aqueous solution (containing M 2 The aqueous solution of the salt of the raw material) and the metal atom M 1 The metal cation (M 1 The aqueous solution (containing M 1 The method is produced by mixing an aqueous solution of a salt of a raw material and supplying M from one main surface of the porous oxide body. 1 The raw material is supplied from the other main surface of the oxide porous body. 2 Use raw materials and make M 1 Use raw materials and M 2 The raw materials are contacted and reacted on the surface or inside of the porous oxide body to form a metal cyanide complex on the surface or inside of the porous oxide body. 1 Use raw materials and M 2 After the raw material phase is contacted, for example, preferably for about 30 seconds to 120 hours, the porous oxide body is removed from M 1 Use raw materials and M 2 The solution may be taken out from the aqueous solution of the raw material, washed as necessary, and then dried.

[0100] Such a metal cyanide complex formation step requires fewer steps for separation membrane production, has high raw material safety, and does not require heating, thereby reducing energy costs and is simple.

[0101] M 2 The counter ions in the aqueous solution of the raw material (with M 2 The cations that form salts with the raw materials are not particularly limited, but examples thereof include hydrogen ions, lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, and ammonium ions, preferably potassium ions or sodium ions, and more preferably potassium ions. 1 The counter ions in the aqueous solution of the raw material (with M 1 The anion that forms the salt with the raw material is not particularly limited, but examples thereof include Cl - 、NO 3- 、SO4 2- Inorganic ions.

[0102] M 2 The metal M in the aqueous solution of the raw material 2 The ion concentration is preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more, further preferably 0.2 mol / L or more, and is further preferably 1.5 mol / L or less, more preferably 1.2 mol / L or less, further preferably 1.0 mol / L or less (i.e., preferably 0.05 to 1.5 mol / L, more preferably 0.1 to 1.2 mol / L, further preferably 0.2 to 1.0 mol / L).

[0103] M 1 The metal M in the aqueous solution of the raw material 1 The ion concentration is preferably 0.0005 mol / L or more, more preferably 0.001 mol / L or more, further preferably 0.05 mol / L or more, and is further preferably 1.0 mol / L or less, more preferably 0.9 mol / L or less, further preferably 0.8 mol / L or less (i.e., preferably 0.0005 to 1.0 mol / L, more preferably 0.001 to 0.9 mol / L, further preferably 0.05 to 0.9 mol / L, and particularly preferably 0.05 to 0.8 mol / L).

[0104] It is also preferred to appropriately adjust the metal M 1 Ion concentration and metal M 2 The ratio of ion concentration, metal M 2 Ion concentration / metal M 1 The molar ratio of ion concentration (hereinafter, M 2 / M 1 The ratio is preferably 0.1 to 1000. 2 / M 1The ratio is more preferably 0.5 or more, further preferably 3.0 or more, further preferably 5.0 or more, and more preferably 700 or less, further preferably 300 or less, further preferably 50 or less, further preferably 15 or less. By adjusting M 2 / M 1 By changing the ratio or the metal species, the formation location of the metal cyanide complex in the oxide porous body can be controlled. 2 / M 1 The ratio is preferably 0.1 to 1000, more preferably 0.5 to 700, further preferably 3.0 to 300, further preferably 5.0 to 50, particularly preferably 5.0 to 15).

[0105] (Method 2)

[0106] As another method for forming a metal cyanide complex on the surface or inside of a porous oxide body, there is a method comprising the following steps: preparing the same M as in the above method 1; 2 The aqueous solution Sa of the raw material (specifically, M 2 The aqueous solution of the salt of the raw material) and the M containing the same 1 A non-aqueous hydrophobic organic solvent solution Sb (specifically, M 1 The method further comprises the following steps of: an impregnation step of impregnating at least a portion of the oxide porous body with the aqueous solution Sa or the solution Sb; and a step of bringing a portion of the oxide porous body impregnated with the aqueous solution Sa or the solution Sb in the impregnation step into contact with another solution of the aqueous solution Sa or the solution Sb other than the solution used in the impregnation step. In the impregnation step, the portion impregnated with the aqueous solution Sa or the solution Sb is preferably a layer (S1) with the smallest average pore diameter or a layer with an average pore diameter of less than 0.5 μm. As described above, the solution used in the impregnation step may be the aqueous solution Sa or the solution Sb, but it is preferred that: after at least a portion of the oxide porous body is impregnated in the solution Sb, the portion of the oxide porous body impregnated in the solution Sb is brought into contact with the same M1 as in the method 1. 2 The aqueous solution Sa of the raw material is contacted. 2 The aqueous solution Sa of the raw material is specifically A p [M 2 (CN) w ](p represents a value from 1 to 4, A, M 2 and w as described above). By using 1 The raw materials used are dissolved in a non-aqueous hydrophobic organic solvent to obtain a solution Sb and M2 By dissolving the raw material in water and bringing the two into contact with each other, M 1 With M 2 The reaction site is limited to the vicinity of the interface between the organic solvent and water. In particular, when the above-mentioned oxide porous body has two or more layers with different pore diameters, it is preferred that: the above-mentioned solution Sb is impregnated into at least the layer (S1) with the smallest average pore diameter or the layer with an average pore diameter of 0.5 μm or less in the above-mentioned oxide porous body, and the layer (S1) of the oxide porous body impregnated with the above-mentioned solution Sb or the layer with an average pore diameter of 0.5 μm or less is brought into contact with the above-mentioned aqueous solution Sa. By doing so, the metal cyanide complex represented by the above-mentioned formula (1) can be uniformly formed inside or on the surface of the layer (S1) of the oxide porous body or the layer with an average pore diameter of 0.5 μm or less. In method (2), the average pore diameter of the layer (S1) is more preferably 0.5 μm or less.

[0107] As the above-mentioned non-aqueous hydrophobic solvent, an organic solvent that is immiscible with water, for example, aliphatic monohydric alcohols having more than 5 carbon atoms such as pentanol, hexanol, heptanol, and octanol, aliphatic hydrocarbons such as hexane, and aromatic hydrocarbons such as benzene and toluene can be used. In addition, these solvents can be used alone or in combination of multiple types.

[0108] In method 2, with M 1 The anions used as the raw materials to form the salts are preferably organic ions, and examples thereof include CH3COO - etc. carboxylate ions.

[0109] In method 2, with M 2 The cations that form salts with the raw materials may be, for example, sodium ions.

[0110] In method 2, M 1 The metal M in the hydrophobic solvent of the raw material 1 The ion concentration is preferably 0.0001 to 0.05 mol / L, more preferably 0.0003 to 0.01 mol / L, and even more preferably 0.0005 to 0.005 mol / L.

[0111] In method 2, M 2 The metal M in the aqueous solution of the raw material 2 The ion concentration is preferably 0.001 to 0.5 mol / L, more preferably 0.005 to 0.3 mol / L, and even more preferably 0.01 to 0.1 mol / L.

[0112] In method 2, it is also preferred to appropriately adjust the metal M 1 Ion concentration and metal M 2 The ratio of ion concentration, metal M 2Ion concentration / metal M 1 The molar ratio of ion concentration (hereinafter, M 2 / M 1 The ratio is preferably 1 to 100, more preferably 10 to 80, further preferably 20 to 70, particularly preferably 30 to 60.

[0113] The porous oxide body immersed in the solution Sb is mixed with M 2 After contacting with the aqueous solution Sa of the raw material, the mixture is allowed to stand for about 1 to 10 days, for example, and washed as necessary and then dried.

[0114] (Method 3)

[0115] As another method for forming a metal cyanide complex on the surface or inside of the porous oxide body, Fe 3+ [Fe 3+ (CN)6] is impregnated into at least a portion of an oxide porous body with an aqueous solution of a metal cyanide complex represented by [(CN)6], and the oxide porous body impregnated with the aqueous solution in at least a portion thereof is subjected to a reduction treatment. In particular, when the oxide porous body has two or more layers with different pore diameters, it is preferred that: at least the layer (S1) with the smallest average pore diameter or the layer with an average pore diameter of 0.5 μm or less in the oxide porous body is impregnated with the aqueous solution, and the oxide porous body impregnated with the metal cyanide complex in at least the layer (S1) with the smallest average pore diameter or the layer with an average pore diameter of 0.5 μm or less is subjected to a reduction treatment. By doing so, the metal cyanide complex represented by the following formula (1') can be uniformly formed inside or on the surface of the layer (S1) of the oxide porous body or the layer with an average pore diameter of 0.5 μm or less.

[0116] A x M 11 [M 21 (CN)6] y ·zH2O(1')

[0117] [wherein, A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, and M 11 and M 21 is iron (III), x represents a value of 0 to 4, y represents a value of 0.1 to 2, and z represents a value of 0 to 6.]

[0118] Fe 3+ [Fe 3+ (CN)6] By making M 2 The anionic metal cyanide complex of the raw material is used as M 1 Raw metal M 1The cation is obtained by reacting in water, by 1 and M 2 The metals are all set to trivalent iron ions, so that Fe[Fe(CN)6] can exist as an aqueous solution of Fe[Fe(CN)6] without precipitation. Specifically, as long as M 2 The salts and M 1 Just dissolve the salts of the raw materials in water to react.

[0119] After impregnating the layer (S1) or the layer having an average pore size of 0.5 μm or less with an aqueous solution of Fe[Fe(CN)6], the porous oxide body is subjected to a reduction treatment so that the surface of the layer (S1) or the layer having an average pore size of 0.5 μm or less is reduced, thereby making it possible to reduce the surface of the porous oxide body. x Fe[Fe(CN)6] y The metal cyanide complex represented by zH2O is formed on the surface of the layer (S1) or the surface of the layer having an average pore size of 0.5 μm or less. After the reduction treatment, it is preferably washed with water or the like to remove the remaining Fe[Fe(CN)6].

[0120] The reduction method is not particularly limited, but reduction using a reducing agent or light can be cited, and reduction using hydrogen or the like and reduction using light containing ultraviolet rays can be cited preferably. Reduction using hydrogen can include drying the oxide porous body impregnated with an aqueous solution of Fe[Fe(CN)6] in a hydrogen stream for about 1 to 10 days. In the case of light reduction, the wavelength of the light is not particularly limited, but preferably includes light of 500 nm or less, more preferably includes light of 450 nm or less, and further preferably includes light of 400 nm or less, and preferably irradiates such light for about 10 to 180 minutes.

[0121] In method 3, with M 1 The anions used to form salts include Cl - 、NO 3- 、SO4 2- Inorganic ions such as ions such as carboxylate ions or hydroxycarboxylate ions, preferably NO 3- or hydroxycarboxylate ions (particularly citrate ions).

[0122] In method 3, with M 2 Examples of cations that form salts with the raw materials include hydrogen ions, lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, and ammonium ions, and potassium ions are preferred.

[0123] In using M 2 The salts of the raw materials and M 1 In the water reacted with the salt of the raw material, preferably: metal M 1The ion concentration is 0.05 to 15% by mass, and the metal M 2 The ion concentration is 0.001 to 8 mass %, and the metal M 1 Ions and Metals 2 The mass ratio of ions (M 1 / M 2 ) is 1.5 to 5, more preferably: metal M 1 The ion concentration is 0.1 to 10 mass %, and the metal M 2 The ion concentration is 0.05 to 6 mass %, and the metal M 1 Ions and Metals 2 The mass ratio of ions (M 1 / M 2 ) is 1.5~5.

[0124] 3. Ammonia separation method

[0125] The present invention also includes an ammonia separation method, which uses the above-mentioned ammonia separation membrane to selectively permeate ammonia from a mixed gas containing ammonia. The mixed gas containing ammonia is supplied from one side of the ammonia separation membrane, and a pressure difference or a concentration difference is set between the one side and the other side, so that ammonia is selectively permeated from the mixed gas containing ammonia to the other side.

[0126] According to the ammonia separation method of the present invention, the separation coefficient S of ammonia calculated by the following formula can be set to 1.5 or more, preferably 3.0 or more, and more preferably 5.0 or more. The upper limit of the separation coefficient is infinite when only ammonia completely permeates, but in practice, the separation coefficient sometimes becomes less than about 100,000, and even if it is less than 1000 or less than 100, it is effective for the separation of ammonia.

[0127] Separation factor S = (ammonia concentration of gas after permeation of separation membrane / nitrogen concentration of gas after permeation of separation membrane) / (ammonia concentration of supplied mixed gas / nitrogen concentration of supplied mixed gas)

[0128] The ratio of ammonia in the mixed gas containing ammonia is, for example, 3 to 50% by volume, preferably 5 to 30% by volume. Gases other than ammonia in the mixed gas include, for example, hydrogen and nitrogen, and the mixed gas preferably contains 50% by volume or more of nitrogen, more preferably 70% by volume or more.

[0129] In addition, in the preferred embodiment of the ammonia separation membrane, the layer (S1) with the smallest average pore size as described above is the outermost layer on one side of the oxide porous body, and a metal cyanide complex is formed inside the layer (S1) and / or adjacent to the layer (S1). When using such an ammonia separation membrane to separate ammonia, it is preferred to supply a mixed gas containing ammonia from the side of the layer (S1) with the smallest average pore size.

[0130] This application claims priority based on Japanese Patent Application No. 2022-078202 filed on May 11, 2022. The entire contents of the specification of Japanese Patent Application No. 2022-078202 filed on May 11, 2022 are incorporated herein by reference.

[0131] Example

[0132] The present invention is not limited to the following embodiments, and can be implemented with appropriate changes within the scope of the above and the following gist, which are all included in the technical scope of the present invention.

[0133] Example 1

[0134] Cobalt chloride (CoCl2, M 1 Raw materials) and potassium hexacyanoferrate (III) (K3[Fe(CN)6], M 2 The raw materials) were dissolved in water to adjust the concentrations to 0.06 M and 0.6 M. x M 1 [M 2 (CN) w ] y When expressed as zH2O, Co is equivalent to M 1 , Fe is equivalent to M 2 , K is equivalent to A, M 1 Use raw materials and M 2 M 2 / M 1 The ratio is 10.

[0135] Next, a cylindrical oxide porous body was produced according to the following procedure.

[0136] First, a cylindrical porous alumina tube with an outer diameter of 10 mm, an inner diameter of 7 mm, and a length of 10 cm is prepared. The outermost surface of the porous alumina tube is a layer containing more than 90% by mass of α-alumina. The pore diameter is measured by mercury intrusion method, and the result is that the pore diameter is about 0.1 μm. Then, an alumina sol (Alumina Sol-10A manufactured by KAWAKEN Fine Chemicals Co., Ltd.) is used to dip-coat the porous alumina tube at both ends in a manner that the alumina sol does not enter the inner surface of the tube, and then heat-treated to obtain an oxide porous body. The pore diameter of the outermost layer of the obtained oxide porous body is measured by capillary condensation method, and the result is about 8 nm. In addition, the outermost layer of the outer peripheral surface of the oxide porous body is a γ-alumina layer, and its film thickness is about 2 μm.

[0137] A stopper is placed at one end of the cylindrical porous oxide body, and the inside of the porous oxide body is kept hollow, and then immersed in the aqueous cobalt chloride solution. The aqueous potassium hexacyanoferrate (III) solution is added to the inner side of the cylindrical porous oxide body. After the cylindrical porous oxide body is left to stand for 1 day in this state, the stopper is removed and washed with water and air-dried. By repeating these operations again, a cylindrical porous oxide body formed with a metal cyanide complex, i.e., an ammonia separation membrane, is produced. The metal cyanide complex formed is K 3a-2 Co[Fe(CN)6] a ·z 1 H2O (where a>2 / 3).

[0138] The ammonia separation performance of the ammonia separation membrane produced in Example 1 was evaluated by the following method.

[0139] (1) Evaluation of ammonia separation performance

[0140] A mixed gas of ammonia and nitrogen (ammonia 9.6 vol%, nitrogen 90.4 vol%) was supplied at 50 mL / min from the side of the cylindrical porous body. At this time, the pressure difference applied to the tube wall of the cylindrical porous body was adjusted to 100 kPa using a back pressure valve and a vacuum pump. The concentrations of ammonia and nitrogen were calculated for the gas after passing through the cylindrical porous body using a mass spectrometer (device name: BELMASS, Microtrac BEL Co., Ltd.), and the separation coefficient S was calculated according to the following formula.

[0141] S = (ammonia concentration of permeated gas / nitrogen concentration of permeated gas) / (ammonia concentration of supply gas / nitrogen concentration of supply gas)

[0142] The separation coefficient S of Example 1 was 3.7, and the ammonia separation membrane of the present invention was able to selectively separate ammonia from the mixed gas containing ammonia. On the other hand, the dispersion coefficient calculated assuming the Knudsen state was 1.3.

[0143] Example 2

[0144] The sample was prepared in the same manner as in Example 1 except that cobalt chloride was replaced with iron (III) nitrate nonahydrate, potassium hexacyanoferrate (III) was replaced with sodium hexacyanoferrate (II), and the film formation (metal cyanide complex formation step) was set to only one time. The metal cyanide complex formed was Na 4b-3 Fe[Fe(CN)6] b ·z 2 H2O (where b>3 / 4).

[0145] (2) Cross-sectional TEM observation and elemental analysis of ammonia separation membrane

[0146] The ammonia separation membranes of Examples 1 and 2 were subjected to TEM observation and elemental analysis using TEM-EDX.

[0147] The results of the TEM observation and the elemental analysis using TEM-EDX performed in (2) above are shown in FIG. Figure 2 , Figure 3 In addition, Figure 4 The example in which the same raw materials as in Example 1 are used and the formation site of the metal cyanide complex is changed is shown. Figure 2 and Figure 4 The "Co-K" in FIG. 1 is an EDX map attributed to the electron transition of Co to K nuclei, indicating the existence position of Co. Figure 3 The “Fe-K” in FIG. 1 is an EDX map attributed to the electron transition from Fe to K nuclei, indicating the existence position of Fe.

[0148] according to Figure 2 It is known that a metal cyanide complex is formed in the oxide porous body of the ammonia separation membrane produced in Example 1, and the metal cyanide complex is formed in the layer having the smallest average pore diameter. Figure 3 It is found that the metal cyanide complex is formed in the oxide porous body of the ammonia separation membrane produced in Example 2, and the metal cyanide complex is formed inside the layer with the smallest average pore diameter. Figure 4 It can be seen that the metal cyanide complex having the same composition as that of Example 1 is formed inside the layer having the smallest average pore diameter in the oxide porous body of the ammonia separation membrane.

[0149] Example 3

[0150] Cobalt acetate ((CH3COO)2Co, M 1 The raw materials) were mixed with 1-octanol to prepare a solution of 1 mM. Then, sodium hexacyanoferrate (Na4[Fe(CN)6], M 2 The raw material) was dissolved in water to adjust the concentration to 0.05 M. The metal cyanide complex formed was prepared by mixing with water. x M 1 [M 2 (CN) w ] y When expressed as zH2O, Co is equivalent to M 1 , Fe is equivalent to M 2 , Na is equivalent to A.

[0151] The oxide porous body prepared by the same method as in Example 1 is immersed in the 1-octanol solution of cobalt acetate. After the 1-octanol solution of cobalt acetate is infiltrated into the oxide porous body, the oxide porous body is taken out and plugged at both ends. The plugged oxide porous body is immersed in the sodium hexacyanoferrate (II) aqueous solution. After the cylindrical oxide porous body is left to stand for 5 days in this state, the plug is removed, washed with water, and air-dried to produce a cylindrical oxide porous body formed with a metal cyanide complex, i.e., an ammonia separation membrane. The metal cyanide complex formed is Na 3c-2 Co[Fe(CN)6] c ·z 3 H2O (where c>2 / 3). The ammonia separation membrane obtained in Example 3 was also confirmed to have formed a metal cyanide complex on the surface or inside the layer having the smallest average pore size (ie, the γ-alumina layer having a pore size of 8 nm).

[0152] The ammonia separation performance was evaluated by the same method as in Example 1. As a result, the separation coefficient S of Example 3 was 9.7.

[0153] Example 4

[0154] Iron (III) nitrate 9 hydrate (Fe(NO3)3·9H2O, M 1 Raw materials) and potassium hexacyanoferrate (III) (K3[Fe(CN)6], M 2 The raw materials were dissolved in water to adjust the mixture to 0.01 M.

[0155] The porous oxide body prepared by the same method as in Example 1 was immersed in the mixed solution, and the mixed solution was allowed to penetrate into the porous oxide body. After drying in a hydrogen stream for 5 days, the porous oxide body was washed with water to prepare a cylindrical porous oxide body having a metal cyanide complex formed thereon, i.e., an ammonia separation membrane. The formed metal cyanide complex was K 4d-3 Fe[Fe(CN)6] d ·z 4 H2O (where d>3 / 4).

[0156] The ammonia separation performance was evaluated by the same method as in Example 1. The separation coefficient S of Example 4 was 16.

[0157] Figure 5 Elemental analysis results of the ammonia separation membrane obtained in Example 4 using an electron probe microanalyzer (EPMA) are shown in FIG. Figure 5 The upper side shows the distribution of Al, Figure 5 The lower side shows the results of Fe distribution. Figure 5 The left side of the paper is a layer with the smallest average pore size (ie, a γ-alumina layer with a pore size of 8 nm), and a state in which a metal cyanide complex is formed near the γ-alumina layer can be observed.

[0158] Example 5

[0159] Ammonium iron (III) citrate and potassium hexacyanoferrate (III) were dissolved in water to adjust the mixed solutions to 2% and 1%, respectively.

[0160] The oxide porous body prepared by the same method as in Example 1 was immersed in the above-mentioned mixed solution, and after the above-mentioned mixed solution was infiltrated into the above-mentioned oxide porous body, it was irradiated with sunlight for 60 minutes while rotating in the radial direction at a speed of 60 rpm, and then washed with water to prepare a cylindrical oxide porous body formed with a metal cyanide complex, that is, an ammonia separation membrane. The formed metal cyanide complex is K 3e-3 Fe[Fe(CN)6] e ·z 5 H2O (where e>1). In the ammonia separation membrane obtained in Example 5, it was also confirmed that a metal cyanide complex was formed on the surface or inside the layer having the smallest average pore size (ie, the γ-alumina layer having a pore size of 8 nm).

[0161] The ammonia separation performance was evaluated by the same method as in Example 1. The separation factor S of Example 5 was 15.

Claims

1. An ammonia separation membrane, It is characterized in that A metal cyanide complex represented by the following formula (1) and a porous oxide body, The pore shape of the oxide porous body is amorphous. From x M 1 [M 2 (CN) w ] y ·zH 2 O(1) In the formula, M 1 represents one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium and calcium, M 2 represents one or more metal atoms selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum and copper, A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, x represents a value of 0 to 4, y represents a value of 0.1 to 2, z represents a value of 0 to 6, and w represents a value of 4 to 8.

2. The ammonia separation membrane according to claim 1, in, The porous oxide body has two or more layers having different pore diameters.

3. The ammonia separation membrane according to claim 2, in, The porous oxide body has two or more layers having different pore diameters. The metal cyanide complex is formed inside the layer (S1) having the smallest average pore diameter and / or adjacent to the layer (S1).

4. The ammonia separation membrane according to claim 3, in, The outermost layer on one side of the porous oxide body is the layer (S1).

5. The ammonia separation membrane according to claim 3 or 4, in, The average pore diameter of the layer (S1) is 0.5 μm or less.

6. The ammonia separation membrane according to claim 1 or 2, in, The metal cyanide complex is formed inside the layer having an average pore diameter of 0.5 μm or less of the porous oxide body and / or on the surface of the layer having an average pore diameter of 0.5 μm or less.

7. A method for producing an ammonia separation membrane comprising a metal cyanide complex represented by the following formula (1) and an oxide porous body, in, The porous oxide body has an amorphous pore shape and has two or more layers with different pore diameters. The method comprises the following steps: Containing A p [M 2 (CN) w ] and an aqueous solution Sa containing one or more metals selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium and calcium, namely M 1 A step of impregnating at least one of the solutions Sb of a hydrophobic solvent of the oxide porous body into a layer (S1) having the smallest average pore size or a layer having an average pore size of 0.5 μm or less, wherein A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, and M 2 represents one or more metal atoms selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum and copper, p represents a value of 1 to 4, and w represents a value of 4 to 8; and A step of bringing the layer (S1) having the smallest average pore size or the layer having an average pore size of 0.5 μm or less of the oxide porous body impregnated with any one of the aqueous solution Sa and the solution Sb in the impregnation step into contact with another solution of the aqueous solution Sa and the solution Sb other than the solution used in the impregnation step, From x M 1 [M 2 (CN) w ] y ·zH 2 O(1) In the formula, A, M 1 、M 2 , w are the same as above, x represents a value of 0 to 4, y represents a value of 0.1 to 2, and z represents a value of 0 to 6.

8. A method for producing an ammonia separation membrane comprising a metal cyanide complex represented by the following formula (1') and an oxide porous body, in, The porous oxide body has an amorphous pore shape and has two or more layers with different pore diameters. The method comprises the following steps: Make Fe 3+ [Fe 3+ (CN) 6 ] is impregnated into at least the layer (S1) with the smallest average pore diameter or the layer with an average pore diameter of 0.5 μm or less in the oxide porous body with an aqueous solution of the metal cyanide complex represented by ; and The metal cyanide complex Fe 3+ [Fe 3+ (CN) 6 ] is used to reduce the porous oxide body, From x M 11 [M 21 (CN) 6 ] y ·zH 2 O(1') In the formula, A represents one or more atoms selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, and M 11 and M 21 is iron (III), x represents a value of 0 to 4, y represents a value of 0.1 to 2, and z represents a value of 0 to 6.

9. The method according to claim 8, in, The reduction treatment is a treatment using a reducing gas atmosphere.

10. The method according to claim 8, in, The reduction treatment is a treatment using light.

11. A method for separating ammonia, wherein include: Ammonia is selectively permeated from a mixed gas containing ammonia using the ammonia separation membrane according to any one of claims 1 and 2.

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