JP2015174066A - Separation membrane for treating acidic gas-containing gas and manufacturing method of separation membrane for treating acidic gas-containing gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane for treating acidic gas-containing gas which optimizes a middle layer disposed on a support and, thereby, can efficiently obtain methane gas from digestion gas containing acidic gas such as carbon dioxide and methane gas.SOLUTION: A separation membrane for treating acidic gas-containing gas includes: an inorganic porous support; an intermediate layer which contains a silica fine particle connection body formed on the surface of the inorganic porous support; and a separation layer which contains a hydrocarbon group-containing polysiloxane network structure formed on the intermediate layer. The silica fine particle connection body is a single structure obtained by sintering reaction of colloidal silica and the hydrocarbon group-containing polysiloxane network structure is a composite structure obtained by sol-gel reaction of tetra-alkoxysilane and hydrocarbon group-containing trialkoxysilane.

Description

  The present invention is for effectively using digestive gas containing, for example, acid gas and methane gas obtained by biological treatment of garbage and the like, and in particular, acid gas or methane gas contained in digestion gas. The present invention relates to a separation membrane for acid gas-containing gas treatment to be separated and a method for producing the same.

  When the garbage is biologically treated, digestive gas in which acid gas (carbon dioxide, hydrogen sulfide, etc.) and flammable gas (methane gas, etc.) are mixed is generated. Since this digestion gas can be combusted as it is, it can be used as a fuel for thermal power generation, for example. Recently, from the viewpoint of effective use of energy, methane gas, which is a combustible component, is extracted from the digestion gas, and this is used. It is used as a raw material for city gas and as a raw material for hydrogen used in fuel cells.

Conventionally, as a technique for separating methane gas from mixed gas such as digestion gas, separation membranes are arranged in two stages, and gas other than methane gas in the mixed gas is stepped by passing the mixed gas through the separation membrane of each stage. There is a methane concentrator that separates the methane gas and increases the concentration of methane gas (see, for example, Patent Document 1). The methane concentrator of Patent Document 1 separates a gas A having a molecular diameter smaller than that of methane gas from a mixed gas. However, as a separation membrane, the permeability coefficient ratio A / methane between gas A and methane is 5 or more and gas A transmittance is using an inorganic porous membrane having a ^{1 × 10 -9 (mol · m} -2 · s -1 · Pa -1) or more properties. It is said that by using such a separation membrane, a gas having a high methane concentration can be recovered in a high yield.

  In obtaining high-concentration methane gas from the mixed gas, if carbon dioxide is separated from the mixed gas, the concentration of methane gas in the mixed gas will be relatively increased, and as a result, high-concentrated methane gas can be obtained. It becomes. As a technique for separating carbon dioxide from a mixed gas, in a separation membrane made of an amorphous oxide having a plurality of pores formed by cyclic siloxane bonds, nitrogen (N) having basicity in the side chain of Si and There has been a gas separation filter using a functional group containing silicon (Si) combined (for example, see Patent Document 2). According to the gas separation filter of Patent Document 2, acidic gas such as carbon dioxide efficiently passes through narrow pores, so that separation performance can be improved.

JP 2008-260739 A JP 2000-279773 A

In order to concentrate the methane gas in the mixed gas using the separation membrane, it is necessary to develop a separation membrane capable of efficiently transmitting carbon dioxide contained in the mixed gas. In this regard, the methane concentrator of Patent Document 1 uses a separation membrane that separates the gas A having a molecular diameter smaller than that of methane gas, and the gas A includes carbon dioxide. Then, according to an embodiment of the document, as permeability coefficient ratio _CO 2 / CH ₄ of carbon dioxide and methane, the value of 3.3 to 20 is shown. However, at such a permeation coefficient ratio, the loss of methane gas is large, and if a complicated apparatus configuration such as a separation membrane having two stages as in Patent Document 1 and recirculation of non-permeate gas is used, it is a practical level. However, it was difficult to concentrate methane gas sufficiently.

  The gas separation filter of Patent Document 2 intends to improve the carbon dioxide separation performance by introducing a functional group containing basic nitrogen (N) and silicon (Si) on the surface of the separation membrane. It is. In order to exhibit sufficient carbon dioxide separation performance, it is important to form a uniform membrane while introducing a sufficient number of functional groups on the surface of the separation membrane. However, in the separation membrane of Patent Document 2, the number of functional groups that can be introduced is determined by the molecular structure of the raw material (the number of reaction sites), and the carbon dioxide separation performance is improved only by improving the separation membrane itself. Has its limits. In addition, when the number of functional groups introduced into the separation membrane increases, steric hindrance is likely to occur in the molecular structure, which may adversely affect uniform membrane formation.

  In addition, the separation membrane used in Patent Document 1 and Patent Document 2 is prepared by applying a liquid (sol-like) separation film forming material to a support and heat-treating it. Here, in order to improve the film-forming property of the separation membrane on the support, an intermediate layer is provided in advance on the support. In this case, it is important for the intermediate layer to properly select the weight of the intermediate layer forming material and the support in consideration of the relationship between the constituent material of the separation membrane and the support. However, in Patent Document 1 and Patent Document 2, the technical idea of selecting the intermediate layer forming material in consideration of the constituent material of the separation membrane is not seen, and the basis weight on the support is not examined. .

  The present invention has been made in view of the above problems, and it is possible to efficiently obtain methane gas from digestion gas containing acidic gas such as carbon dioxide and methane gas while optimizing the intermediate layer provided on the support. It is an object of the present invention to provide a separation membrane for treating acidic gas-containing gas and a method for producing the same.

The characteristic structure of the separation membrane for acid gas-containing gas treatment according to the present invention for solving the above problems is as follows.
An inorganic porous support;
An intermediate layer comprising a silica fine particle conjugate formed on the surface of the inorganic porous support;
A separation layer comprising a hydrocarbon group-containing polysiloxane network formed on the intermediate layer;
It is in having.

  According to the separation membrane for acid gas-containing gas treatment of this configuration, the silica fine particle combination contained in the intermediate layer and the hydrocarbon group-containing polysiloxane network structure contained in the separation layer are materials of the same system. Since the molecular structures are similar, the silica fine particle conjugate and the hydrocarbon group-containing polysiloxane network have high affinity for each other. Therefore, when an intermediate layer is formed on the surface of the inorganic porous support and a separation layer is formed thereon, no interfacial delamination or cracking occurs between the intermediate layer and the separation layer, and the two adhere firmly. A stable separation membrane for acid gas-containing gas treatment can be configured. When a digestion gas containing an acid gas such as carbon dioxide and methane gas is passed through the separation membrane for treatment of acid gas-containing gas, carbon dioxide in the digestion gas is selectively converted into a hydrocarbon group-containing polysiloxane network structure. It is attracted to the surface and passes through the separation membrane as it is. As a result, the methane gas component in the digestion gas is concentrated, and a high concentration of methane gas can be obtained efficiently.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The silica fine particle combination is a single structure obtained by a sintering reaction of colloidal silica,
The hydrocarbon group-containing polysiloxane network structure is preferably a composite structure obtained by a sol-gel reaction of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane.

  According to the acidic gas-containing gas treatment separation membrane of this configuration, the silica fine particle combination forming the intermediate layer uses colloidal silica as a raw material, and forms a single structure by a sintering reaction. Since this single structure has a stable structure derived from colloidal silica, the inorganic porous support can be stabilized. As a result, the separation layer forming material (sol) applied to the surface of the inorganic porous support when forming the separation layer can be prevented from excessively penetrating into the inorganic porous support. The hydrocarbon group-containing polysiloxane network structure forming the separation layer is made from tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane as raw materials, and these are subjected to sol-gel reaction to form a composite structure. ing. This composite structure has a characteristic that combines a stable structure derived from tetraalkoxysilane and a high affinity for carbon dioxide derived from a hydrocarbon group-containing trialkoxysilane. Therefore, when digestion gas is allowed to pass through the composite structure, carbon dioxide is selectively attracted, and the methane gas component in the digestion gas can be efficiently concentrated.

In the separation membrane for acid gas containing gas treatment according to the present invention,
The tetraalkoxysilane is tetramethoxysilane or tetraethoxysilane,
The hydrocarbon group-containing trialkoxysilane is preferably one in which an alkyl group having 1 to 6 carbon atoms or a phenyl group is bonded to the Si atom of trimethoxysilane or triethoxysilane.

  According to the separation membrane for acid gas-containing gas treatment of this configuration, since the significant combination is selected as tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane, a stable structure and high carbon dioxide affinity Thus, a composite structure having both can be efficiently obtained. An acid gas-containing gas treatment separation membrane in which this composite structure is combined with a single structure derived from colloidal silica can be used as one having excellent carbon dioxide or methane gas separation performance and high reliability.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
It is preferable that a metal salt having an affinity for acidic gas is added to the separation layer.

  According to the separation membrane for treatment of acid gas containing gas of this configuration, the affinity of the separation membrane for carbon dioxide is synergistically added to the separation layer by adding a metal salt having affinity for acid gas (including carbon dioxide). Can be enhanced.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The metal salt is an acetate, nitrate, carbonate, borate, or phosphate of at least one metal selected from the group consisting of Li, Na, K, Mg, Ca, Ni, Fe, and Al. Preferably there is.

  According to the separation membrane for treatment of acid gas containing gas of this configuration, the above significant metal salt is selected as the metal salt having affinity with acid gas (including carbon dioxide). When carbon dioxide is passed, carbon dioxide in the digestion gas is surely attracted, and carbon dioxide selectively permeates the separation membrane. As a result, the methane gas component in the digestion gas is concentrated, and a high concentration methane gas can be obtained.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The basis weight of the intermediate layer is 0.1 to 3.0 mg / cm ² ,
The basis weight of the separation layer is preferably 0.1 to 4.0 mg / cm ² .

  According to the separation membrane for acid gas-containing gas treatment of this configuration, the basis weight of the intermediate layer and the separation layer is set in the above-mentioned appropriate range, so that the separation membrane is stabilized by the intermediate layer and the dioxide dioxide by the separation layer. Excellent separation performance of carbon or methane gas can be achieved at a high level.

In the separation membrane for acid gas containing gas treatment according to the present invention,
The inorganic porous support preferably has fine pores of 4 to 200 nm.

  According to the separation membrane for gas treatment containing an acidic gas of this configuration, since the inorganic porous support has fine pores of the appropriate size, it is easy to form a stable intermediate layer, and the separation performance of the separation layer It is possible to constitute a separation membrane that is not impaired.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The distance that the tetraalkoxysilane or the hydrocarbon group-containing trialkoxysilane soaks in the depth direction from the surface of the inorganic porous support is preferably 50 μm or less.

  According to the acidic gas-containing gas treatment separation membrane of this configuration, since the penetration amount of tetraalkoxysilane or hydrocarbon group-containing trialkoxysilane into the inorganic porous support is suppressed, the inorganic porous support The micropores are not clogged excessively. Therefore, when the digestion gas is passed through the separation membrane, the gas passage amount (digestion gas processing amount) can be maintained. In addition, the amount of the intermediate layer and separation layer forming material (sol) applied to the inorganic porous support can be reduced, which can contribute to the reduction of the manufacturing cost of the separation membrane.

In order to solve the above-mentioned problems, the characteristic configuration of the method for producing a separation membrane for acid gas-containing gas treatment according to the present invention is
(A) A preparatory step of preparing a first mixed liquid in which colloidal silica and an organic solvent are mixed, and a second mixed liquid in which tetraalkoxysilane, hydrocarbon group-containing trialkoxysilane, acid catalyst, water, and organic solvent are mixed. When,
(B) a first coating step of coating the first mixed liquid on the surface of the inorganic porous support;
(C) An intermediate layer forming step of heat-treating the inorganic porous support after the first application step and forming an intermediate layer containing a silica fine particle combination on the surface of the inorganic porous support;
(D) a second coating step of coating the second mixed solution on the intermediate layer;
(E) a separation layer forming step of heat-treating the inorganic porous support having undergone the second coating step to form a separation layer containing a hydrocarbon group-containing polysiloxane network structure on the intermediate layer;
It is to include.

  According to the method for producing a separation membrane for acid gas-containing gas processing of this configuration, the silica fine particle conjugate contained in the intermediate layer and the hydrocarbon group-containing polysiloxane network contained in the separation layer have a high affinity for each other. Therefore, the intermediate layer is formed on the surface of the inorganic porous support by the first coating step and the intermediate layer forming step, and the separation layer is formed on the intermediate layer by the second coating step and the separation layer forming step. When the film is formed, interfacial peeling or cracking does not occur between the intermediate layer and the separation layer, and both are firmly adhered to each other, and a stable separation membrane for acid gas-containing gas treatment can be constituted. When a digestion gas containing an acid gas such as carbon dioxide and methane gas is passed through the separation membrane for treatment of acid gas-containing gas, carbon dioxide in the digestion gas is selectively converted into a hydrocarbon group-containing polysiloxane network structure. It is attracted to the surface and passes through the separation membrane as it is. As a result, the methane gas component in the digestion gas is concentrated, and a high concentration of methane gas can be obtained efficiently.

In the method for producing an acid gas-containing separation membrane for gas treatment according to the present invention,
The first coating step and the intermediate layer forming step are preferably repeated a plurality of times with both steps as a set.

  According to the method for producing a separation membrane for acid gas-containing gas processing of this configuration, a stronger and more stable intermediate layer is formed by repeating the first coating step and the intermediate layer forming step multiple times with both steps as a set. can do.

In the method for producing an acid gas-containing separation membrane for gas treatment according to the present invention,
The second coating step and the separation layer forming step are preferably repeated a plurality of times with both steps as a set.

  According to the manufacturing method of the separation membrane for acid gas-containing gas processing of this configuration, the second coating step and the separation layer forming step are repeated multiple times with both steps as a set, so that the separation layer is stronger and has higher separation performance. Can be formed.

FIG. 1 is a schematic configuration diagram of a gas permeation rate measuring apparatus used in a separation performance confirmation test.

  Hereinafter, the embodiment regarding the manufacturing method of the separation membrane for acidic gas containing gas processing concerning this invention and the separation membrane for acidic gas containing gas processing is described. However, the present invention is not intended to be limited to the configuration described below.

<Separation membrane for acid gas containing gas treatment>
The acidic gas-containing gas treatment separation membrane of the present invention is for treating digestion gas obtained by biological treatment of, for example, garbage. Digestion gas is a mixed gas containing acid gas (mainly carbon dioxide and hydrogen sulfide etc.) and methane gas. In this specification, digestion gas contains carbon dioxide and methane gas. Handle as a mixed gas. Accordingly, in the following description, carbon dioxide is taken as an example of the acidic gas, and the acidic gas-containing gas processing separation membrane is described as a carbon dioxide separation membrane that selectively attracts carbon dioxide for convenience. However, the separation membrane for treatment of acid gas-containing gas of the present invention can also be configured as a methane gas separation membrane that selectively attracts methane gas, and moreover, carbon dioxide / methane that can simultaneously separate carbon dioxide and methane gas. A methane gas separation membrane can also be used. Hereinafter, the separation membrane for treatment of acid gas-containing gas may be simply referred to as “separation membrane”.

  The separation membrane for acid gas-containing gas treatment is constituted by forming an intermediate layer on an inorganic porous support serving as a base, and further forming a separation layer thereon. Examples of the material for the inorganic porous support include silica-based ceramics, silica-based glass, alumina-based ceramics, stainless steel, titanium, and silver. The inorganic porous support has a structure in which an inflow portion into which gas flows and an outflow portion from which gas flows out are provided. For example, the gas inflow portion can be an opening provided in the inorganic porous support, and the gas outflow portion can be the outer surface of the inorganic porous support. It is also possible to use the outer surface of the porous support and the gas outflow part as an opening provided in the inorganic porous support. Since innumerable micropores are formed on the outer surface of the inorganic porous support, gas can flow from the entire outer surface. Examples of the configuration of the inorganic porous material include a cylindrical structure in which a gas flow path is provided, a circular pipe structure, a spiral structure, and a monolith structure in which continuous passages intricately formed are formed. Further, an inorganic porous support may be configured by preparing a solid flat plate or a bulk body made of an inorganic porous material and forming a gas flow path by hollowing out a part thereof. . The fine pore size of the inorganic porous support is preferably 4 to 200 nm. The intermediate layer is provided in order to stabilize the surface of the inorganic porous support and facilitate formation of the separation layer. For example, when a liquid mixture (sol) containing a material for forming a separation layer, which will be described later, is directly applied to the surface of an inorganic porous support having a relatively large micropore size, the liquid mixture penetrates excessively into the micropores. In addition to the surface of the inorganic porous support, it may be difficult to form a separation layer. Therefore, by providing an intermediate layer on the surface of the inorganic porous support, the entrance of the micropores is narrowed by the intermediate layer, and the application of the mixed liquid becomes easy. Moreover, since the surface of the inorganic porous support is equalized by the intermediate layer, separation and cracking of the separation layer can be suppressed. Hereinafter, an intermediate layer and a separation layer having a function of separating carbon dioxide or methane gas in the separation membrane for treatment of acid gas-containing gas of the present invention will be described.

[Middle layer]
The intermediate layer is configured to include a silane compound. The intermediate layer of the present embodiment includes a silica fine particle combined body. The silica fine particle bonded body is obtained by a sintering reaction of colloidal silica.

Colloidal silica is obtained by dispersing silica fine particles (silica sol) mainly composed of silicic acid (SiO ₂ ) in a solvent. The particle diameter of the silica fine particles is usually adjusted to about 10 to 300 nm. Examples of the solvent in which the silica fine particles are dispersed include water, methanol, ethanol, propanol, ethylene glycol, dimethylacetamide, ethyl acetate, toluene, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. As such colloidal silica, for example, colloidal silica “Snowtex (registered trademark)” series sold by Nissan Chemical Industries, Ltd. can be used.

  When colloidal silica is heated, the dispersion medium of silica fine particles evaporates and the silica fine particles come into surface contact, and when further heated, the silica fine particles are fused on the surface (sintering reaction). Thereby, a silica fine particle combination in which silica fine particles are three-dimensionally connected is obtained. The silica fine particle bonded body has a continuous structure by surface fusion of silica fine particles and a porous structure by a space between silica fine particles. Therefore, the silica fine particle bonded body forms an amorphous inorganic porous body mainly composed of silicic acid. Hereinafter, the silica fine particle combination is referred to as a “single structure” in order to distinguish it from a composite polysiloxane network structure described later.

(Separation layer)
The separation layer includes a hydrocarbon group-containing polysiloxane network structure. The hydrocarbon group-containing polysiloxane network structure is obtained by a sol-gel reaction of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane.

  Tetraalkoxysilane is a tetrafunctional alkoxysilane represented by the following formula (1).

A preferred tetraalkoxysilane in formula (1) is tetramethoxysilane (TMOS) in which R _{1 to} R ₄ are the same methyl group or tetraethoxysilane (TEOS) in which the same ethyl group is used.

  The hydrocarbon group-containing trialkoxysilane containing a hydrocarbon group is a trifunctional alkoxysilane represented by the following formula (2).

A preferred hydrocarbon group-containing trialkoxysilane is represented by the formula (2), in which R _{6 to} R ₈ are trimethoxysilane having the same methyl group or triethoxysilane having the same ethyl group to the Si atom of 1 to 6 carbon atoms. In which an alkyl group or a phenyl group is bonded. For example, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxy Examples include silane, hexyltrimethoxysilane, hexyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane.

  When a tetrafunctional alkoxysilane of the formula (1) and a trifunctional alkoxysilane of the formula (2) are subjected to a sol-gel reaction, for example, a composite polysiloxane network structure represented by the following formula (3) is obtained. can get. Hereinafter, the composite polysiloxane network structure is referred to as “composite structure”.

In the composite structure of the formula (3), the hydrocarbon group R ₅ is present in the polysiloxane network structure, and forms a certain organic-inorganic composite.

Here, the trifunctional alkoxysilane of the formula (2) has different characteristics due to the difference in R ₅ . For example, methyltrimethoxysilane or methyltriethoxysilane (having a hydrocarbon group with 1 carbon atom) has an affinity mainly for carbon dioxide, and the number of carbon atoms in the Si atom of trimethoxysilane or triethoxysilane Those having 2 to 6 alkyl groups or phenyl groups bonded thereto (hydrocarbon groups having 2 to 6 carbon atoms) mainly have affinity for methane gas. In synthesizing the composite structure of the formula (3) from the reaction between the tetrafunctional alkoxysilane of the formula (1) and the trifunctional alkoxysilane of the formula (2), a tetrafunctional alkoxysilane (this A) and a trifunctional alkoxysilane (referred to as B) are set to an optimum blending ratio, whereby a separation membrane having excellent carbon dioxide or methane gas separation performance can be formed. Such an appropriate blending ratio is 1/9 to 9/1 in terms of A / B molar ratio, and a preferred blending ratio is 3/7 to 7/3 in terms of A / B molar ratio, more preferable blending ratio A / B is 4/6 to 6/4 in molar ratio. With such a blending ratio, a composite structure having both a stable structure and high carbon dioxide affinity can be obtained efficiently.

  In order to increase the selectivity of carbon dioxide or methane gas, it is also effective to adjust the composition of the trifunctional alkoxysilane (B) of the formula (2) that is one of the raw materials. For example, when increasing the selectivity (affinity) for carbon dioxide, increase the content of methyltrimethoxysilane or methyltriethoxysilane in the trifunctional alkoxysilane to increase the selectivity (affinity) for methane gas. In the case of increasing the content, the content of the trimethoxysilane or triethoxysilane contained in the trifunctional alkoxysilane having a C2-6 alkyl group or phenyl group bonded to the Si atom is increased. That is, after setting the blending ratio (A / B) of the tetrafunctional alkoxysilane (A) and the trifunctional alkoxysilane (B) to the above appropriate range, the trifunctional alkoxysilane (B) , Methyltrimethoxysilane or methyltriethoxysilane (referred to as B1), and a trimethoxysilane or triethoxysilane Si atom bonded to an alkyl group or phenyl group having 2 to 6 carbon atoms (this is referred to as B2) )) And the mixing ratio (B1 / B2) is optimized. In such a trifunctional alkoxysilane (B), an appropriate blending ratio of B1 / B2 is 1/9 to 9/1 by molar ratio, and a preferable blending ratio is 3/7 to 7 by mole ratio of B1 / B2. / 3, and a more preferable blending ratio is 4/6 to 6/4 in terms of a molar ratio of B1 / B2.

In order to further enhance the separation performance of carbon dioxide or methane gas, it is preferable to add (dope) a metal salt having affinity for carbon dioxide to the composite structure of the above formula (3). The metal salt includes acetate, nitrate, carbonate, borate, or phosphate of at least one metal selected from the group consisting of Li, Na, K, Mg, Ca, Ni, Fe, and Al. Can be mentioned. Of these, magnesium acetate or magnesium nitrate is preferred. The metal salts such as magnesium acetate are effective in improving the carbon dioxide separation efficiency because of their good affinity with carbon dioxide. Further, due to the synergistic effect with the hydrocarbon group R ₅ (particularly when R ₅ is a methyl group) contained in the polysiloxane network structure, it becomes possible to separate carbon dioxide with high efficiency. The method of adding the metal salt is performed, for example, by an impregnation method in which the composite structure is immersed in an aqueous solution containing the metal salt, and the metal salt is impregnated alone or with other substances inside the composite structure.

<Method for producing separation membrane for treatment of acid gas-containing gas>
The separation membrane for treatment of acid gas-containing gas of the present invention is produced by performing the following steps (a) to (e). Hereinafter, each step will be described in detail.

(A) Preparatory process As a preparatory process, the 1st liquid mixture (silica sol) which mixed colloidal silica and the organic solvent is prepared. The first liquid mixture is used in the “first coating step” of the next step. The first mixed liquid is preferably prepared so that the concentration of silica fine particles (silica solid content concentration) is 1 to 10% by weight, more preferably 2 to 7% by weight, and further preferably 3 to 5%. . When the silica solid content concentration is less than 1% by weight, the number of coating times (number of steps) of the mixed solution increases and the production efficiency decreases. In addition, since the viscosity of the liquid mixture becomes small, problems such as liquid dripping occur during application. When the silica solid content concentration exceeds 10%, the viscosity of the mixed solution increases, so that it is difficult to form a uniform coating film, and it becomes difficult to obtain a dense and uniform separation membrane. As the organic solvent, for example, methanol, ethanol, propanol, butanol, benzene, toluene and the like are used. Of these, methanol or ethanol is preferred.

  In the preparation step, a second mixed liquid is further prepared by mixing tetraalkoxysilane, hydrocarbon group-containing trialkoxysilane, acid catalyst, water, and organic solvent. A 2nd liquid mixture is used in the below-mentioned "2nd application | coating process." The compounding amounts of tetraalkoxysilane, hydrocarbon group-containing trialkoxysilane, acid catalyst, water, and organic solvent are 0 for the total amount of 1 mol of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane. It is preferable to adjust to 0.005 to 0.1 mol, water 0.5 to 10 mol, and organic solvent 5 to 60 mol. When the compounding amount of the acid catalyst is less than 0.005 mol, the hydrolysis rate becomes low and the time required for producing the separation membrane becomes long. When the compounding amount of the acid catalyst is more than 0.1 mol, the hydrolysis rate becomes excessive, and it becomes difficult to obtain a uniform separation membrane. When the amount of water is less than 0.5 mol, the hydrolysis rate is low, and the sol-gel reaction described below does not proceed sufficiently. When the amount of water is more than 10 mol, the hydrolysis rate becomes excessive, and the pore size is enlarged, so that it is difficult to obtain a dense separation membrane. When the blending amount of the organic solvent is less than 5 mol, the concentration of the second mixed solution becomes high, and it becomes difficult to obtain a dense and uniform separation membrane. When the blending amount of the organic solvent is more than 60 mol, the concentration of the second mixed solution is lowered, the number of coating times (number of steps) of the mixed solution is increased, and the production efficiency is lowered. As the acid catalyst, for example, nitric acid, hydrochloric acid, sulfuric acid and the like are used. Of these, nitric acid or hydrochloric acid is preferred. As the organic solvent, for example, methanol, ethanol, propanol, butanol, benzene, toluene and the like are used. Of these, methanol or ethanol is preferred. When preparing the second mixed solution, a metal salt having an affinity for carbon dioxide can be blended. The compounding amount of the metal salt is adjusted to 0.01 to 0.3 mol in the above compounding conditions. As the metal salt having an affinity for carbon dioxide, those described in the above item “Separation membrane for treatment of acid gas-containing gas” can be used.

スキーム１によれば、初めに、テトラエトキシシランの一部のエトキシ基が加水分解され、脱アルコール化することによりシラノール基が生成する。また、テトラエトキシシランの一部のエトキシ基は加水分解されず、そのまま残存し得る。次いで、一部のシラノール基が近傍のシラノール基と会合し、脱水することにより重縮合する。その結果、シラノール基又はエトキシ基が残存したシロキサン骨格が形成される。上記の加水分解反応、及び脱水・重縮合反応は混合液系内で略均等に進行するため、シラノール基又はエトキシ基はシロキサン骨格中に略均等に分散した状態で存在する。金属塩を添加する場合は、ゾル−ゲル反応時にポリシロキサンに取り込まれた金属塩もポリシロキサン結合中に略均等に分散すると考えられる。この段階では、シロキサンの分子量はそれほど大きいものではなく、ポリマーよりもむしろオリゴマーの状態にある。従って、シラノール基又はエトキシ基含有シロキサンオリゴマーは、有機溶媒を含む第二混合液に溶解した状態にある。 In the second mixed solution, first, a sol-gel reaction in which tetraalkoxysilane repeats hydrolysis and polycondensation proceeds. As the tetraalkoxysilane, those described in the above-mentioned item “Separation membrane for treatment of acid gas-containing gas” can be used. For example, when tetraethoxysilane (TEOS) is used as an example of tetraalkoxysilane, the sol-gel reaction is considered to proceed as shown in Scheme 1 below. This scheme 1 is one model representing the progress of the sol-gel reaction, and does not always reflect the actual molecular structure as it is.

According to Scheme 1, first, a part of ethoxy groups of tetraethoxysilane are hydrolyzed and dealcoholized to produce silanol groups. Further, some ethoxy groups of tetraethoxysilane are not hydrolyzed and can remain as they are. Next, some silanol groups associate with neighboring silanol groups and are polycondensed by dehydration. As a result, a siloxane skeleton in which silanol groups or ethoxy groups remain is formed. Since the hydrolysis reaction and the dehydration / polycondensation reaction proceed substantially evenly in the mixed liquid system, silanol groups or ethoxy groups exist in a state of being dispersed substantially evenly in the siloxane skeleton. When a metal salt is added, it is considered that the metal salt taken into the polysiloxane during the sol-gel reaction is also dispersed substantially uniformly in the polysiloxane bond. At this stage, the molecular weight of the siloxane is not very high and is in an oligomer rather than a polymer. Therefore, the silanol group or ethoxy group-containing siloxane oligomer is in a state of being dissolved in the second mixed liquid containing the organic solvent.

スキーム２によれば、シロキサンオリゴマーのシラノール基又はエトキシ基と、メチルトリエトキシシランのエトキシ基とが反応し、脱アルコール化することによりポリシロキサン結合が生成する。ここで、シロキサンオリゴマーのシラノール基又はエトキシ基は、上述のようにシロキサン骨格中に略均等に分散しているため、シロキサンオリゴマーのシラノール基又はエトキシ基とメチルトリエトキシシランのエトキシ基との反応（脱アルコール化）も略均等に進行すると考えられる。その結果、生成したポリシロキサン結合中にはメチルトリエトキシシラン由来のシロキサン結合が略均等に生成し、従って、メチルトリエトキシシラン由来のエチル基もポリシロキサン結合中に略均等に存在する。金属塩を添加する場合は、ゾル−ゲル反応時にポリシロキサンに取り込まれた金属塩もポリシロキサン結合中に略均等に分散すると考えられる。 Next, the reaction between the siloxane oligomer and the hydrocarbon group-containing trialkoxysilane starts. As the hydrocarbon group-containing trialkoxysilane, those described in the item “Separation membrane for gas treatment containing acid gas” described above can be used. For example, when methyltriethoxysilane is used as an example of a hydrocarbon group-containing trialkoxysilane, the reaction is considered to proceed as shown in Scheme 2 below. Note that Scheme 2 is a model representing the progress of the reaction, and does not necessarily reflect the actual molecular structure as it is.

According to Scheme 2, the silanol group or ethoxy group of the siloxane oligomer reacts with the ethoxy group of methyltriethoxysilane, and the dealcoholization is performed to form a polysiloxane bond. Here, since the silanol group or ethoxy group of the siloxane oligomer is dispersed almost uniformly in the siloxane skeleton as described above, the reaction between the silanol group or ethoxy group of the siloxane oligomer and the ethoxy group of methyltriethoxysilane ( (Dealcoholization) is also considered to proceed substantially evenly. As a result, siloxane bonds derived from methyltriethoxysilane are formed almost evenly in the generated polysiloxane bond, and therefore, ethyl groups derived from methyltriethoxysilane are also present almost uniformly in the polysiloxane bond. When a metal salt is added, it is considered that the metal salt taken into the polysiloxane during the sol-gel reaction is also dispersed substantially uniformly in the polysiloxane bond.

  In the preparation of the second mixed solution, it is preferable to devise such as mixing the acid catalyst in a plurality of times, or mixing the hydrocarbon group-containing trialkoxysilane which is easily hydrolyzed at the end. For example, the composition is prepared so that the pH of the mixed solution always falls within the range of 0.8 to 2.5. In this case, since the pH of the second mixed liquid does not vary greatly, hydrolysis of the hydrocarbon group-containing trialkoxysilane does not proceed rapidly, and the sol-gel reaction can proceed in a stable state.

(B) 1st application | coating process As a 1st application | coating process, the 1st liquid mixture (the colloidal solution or suspension of a silica particle) obtained at the preparation process is apply | coated to an inorganic porous support body. Examples of the method of applying the first mixed liquid to the inorganic porous support include a dipping method (internal dipping method), a spray method, and a spin method. Among these, the dipping method is a preferable coating method because the mixed solution can be uniformly and easily applied to the surface of the inorganic porous support. A specific procedure of the dipping method will be described.
First, a tubular inorganic porous support is prepared. The inorganic porous support is placed in an upright state, and the first mixed liquid is injected from the upper opening and discharged from the lower opening. Thereby, a 1st liquid mixture adheres to the internal surface of an inorganic porous support body. Next, the inorganic porous support is dried. The drying conditions are preferably 25 to 40 ° C. and 0.5 to 3 hours. If the drying time is less than 0.5 hours, sufficient drying cannot be performed, and the drying state hardly changes even if the drying time exceeds 3 hours. When the drying is finished, a product in which silica fine particles are adhered to the inner surface (including the inner surfaces of some of the fine pores) of the inorganic porous support is obtained. In addition, the amount of silica fine particles attached to the inorganic porous support can be increased by repeating the injection of the first mixed liquid into the inorganic porous support a plurality of times. Moreover, since the first mixed liquid can be uniformly applied to the inorganic porous support by repeating a series of procedures, the finally obtained separation membrane for treatment of acid gas-containing gas can be further stabilized. .

(C) Intermediate layer forming step As the intermediate layer forming step, the inorganic porous support after the completion of the first coating step is heat-treated to form a silica fine particle bonded body on the surface of the inorganic porous support. For the heat treatment, for example, a heating means such as a calciner is used. A specific procedure for the heat treatment will be described.
First, the inorganic porous support is heated up to a heat treatment temperature described later. The temperature raising time is preferably 1 to 24 hours. If the temperature rising time is shorter than 1 hour, it is difficult to obtain a uniform film due to a rapid temperature change, and if it is longer than 24 hours, the film may be deteriorated by heating for a long time. After the temperature rise, heat treatment (firing) is performed for a certain time. The heat treatment temperature is preferably 25 to 600 ° C, and more preferably 25 to 500 ° C. If the heat treatment temperature is lower than 25 ° C., sufficient heat treatment cannot be performed, and thus a dense film cannot be obtained. If the heat treatment temperature is higher than 600 ° C., the film may be deteriorated by heating at a high temperature. The heat treatment time is preferably 0.5 to 10 hours, and more preferably 5 to 7 hours. If the heat treatment time is shorter than 0.5 hours, sufficient heat treatment cannot be performed, so that a dense film cannot be obtained. If the heat treatment time is longer than 10 hours, the film may be deteriorated by heating for a long time. After the heat treatment is finished, the inorganic porous support is cooled to room temperature. The cooling time is preferably 5 to 10 hours. If the cooling time is shorter than 5 hours, the film may be cracked or peeled off due to a rapid temperature change, and if it is longer than 10 hours, the film may be deteriorated. An intermediate layer is formed on the inner surface (including the inner surfaces of some of the micropores) of the inorganic porous support after cooling. The mid layer has a basis weight adjusted to 0.1 to 3.0 mg / cm ² , preferably 0.3 to 1.5 mg / cm ² . After the “intermediate layer forming step”, the process returns to the “first applying step” described above, and the first applying step and the intermediate layer forming step are repeated as a set. In addition, an intermediate layer having a denser and uniform film quality can be formed.

(D) Second coating step As the second coating step, a second mixed solution (a colloidal solution or suspension of hydrocarbon group-containing polysiloxane fine particles) is formed on the inorganic porous support on which the intermediate layer has been formed by the intermediate layer forming step. Apply. Since the 2nd liquid mixture apply | coated at a 2nd application | coating process is apply | coated to an inorganic porous support body via an intermediate | middle layer, the amount of permeation of the 2nd liquid mixture to an inorganic porous support body (inorganic porous support body) Distance from which the tetraalkoxysilane or hydrocarbon group-containing trialkoxysilane permeates in the depth direction from the surface of the substrate can be suppressed to 50 μm or less. Accordingly, the fine pores of the inorganic porous support are not excessively blocked, and when the digestion gas is passed through the separation membrane for acid gas-containing gas treatment completed by the separation layer forming step described later, Digestion gas throughput) can be maintained. In addition, since the amount of the intermediate layer and separation layer forming material (sol) applied to the inorganic porous support can be reduced, the production cost of the separation membrane for acid gas-containing gas treatment can be reduced. . The method and conditions for applying the second mixed solution are the same as in the first application step. Also in the second coating step, the amount of the hydrocarbon group-containing polysiloxane fine particles attached to the inorganic porous support can be increased by repeating the injection of the second mixed liquid into the inorganic porous support a plurality of times. . Moreover, since the second mixed liquid can be uniformly applied to the inorganic porous support by repeating a series of procedures, the separation performance of the finally obtained separation membrane for treatment of acid gas-containing gas is further improved. be able to.

(E) Separation layer formation step As the separation layer formation step, the inorganic porous support after the second coating step is heat-treated to form a hydrocarbon group-containing polysiloxane network structure on the surface of the inorganic porous support. . A specific procedure for the heat treatment will be described.
First, the inorganic porous support is heated up to a heat treatment temperature described later. The temperature raising time is preferably 1 to 24 hours. If the temperature rising time is shorter than 1 hour, it is difficult to obtain a uniform film due to a rapid temperature change, and if it is longer than 24 hours, the film may be deteriorated by heating for a long time. After the temperature rise, heat treatment (firing) is performed for a certain time. The heat treatment temperature is preferably 25 to 300 ° C, and more preferably 25 to 150 ° C. If the heat treatment temperature is lower than 25 ° C., sufficient heat treatment cannot be performed, so that a dense film cannot be obtained. If the heat treatment temperature is higher than 300 ° C., the film may be deteriorated by heating at a high temperature. The heat treatment time is preferably 0.5 to 10 hours, and more preferably 5 to 7 hours. If the heat treatment time is shorter than 0.5 hours, sufficient heat treatment cannot be performed, so that a dense film cannot be obtained. If the heat treatment time is longer than 10 hours, the film may be deteriorated by heating for a long time. After the heat treatment is finished, the inorganic porous support is cooled to room temperature. The cooling time is preferably 5 to 10 hours. If the cooling time is shorter than 5 hours, the film may be cracked or peeled off due to a rapid temperature change, and if it is longer than 10 hours, the film may be deteriorated. A separation layer is formed on the surface of the inorganic porous support after cooling (including the inner surfaces of some of the micropores). The separation layer, the basis weight is adjusted to 0.1~4.0mg / cm ^2, it is preferably adjusted to 0.5-2.0 mg / cm ^2. After the “separation layer forming step”, the process returns to the “second application step” described above, and when the second coating step and the separation layer forming step are repeated as a set, the surface of the inorganic porous support is obtained. In addition, it is possible to form a separation layer having a finer and more uniform film quality.

  By carrying out the above steps (a) to (e), the separation membrane for acid gas-containing gas treatment of the present invention is produced. In this separation membrane, a separation layer having a site (methyl group) that attracts a specific gas (carbon dioxide in this embodiment) is formed on an inorganic porous support as a base. The separation layer is formed on the surface of the inorganic porous support via the intermediate layer. Here, the silica fine particle combination contained in the intermediate layer and the hydrocarbon group-containing polysiloxane network structure contained in the separation layer are materials of the same family and have similar molecular structures. The body and the hydrocarbon group-containing polysiloxane network have high affinity for each other. Therefore, interface peeling or cracking does not occur between the intermediate layer and the separation layer, and both are firmly adhered to each other, and a stable separation membrane for acid gas-containing gas treatment can be constituted. When a digestion gas containing an acid gas such as carbon dioxide and methane gas is passed through the separation membrane for treatment of acid gas-containing gas, carbon dioxide in the digestion gas is selectively converted into a hydrocarbon group-containing polysiloxane network structure. It is attracted to the surface and passes through the separation membrane as it is. As a result, the methane gas component in the digestion gas is concentrated, and a high concentration of methane gas can be obtained efficiently. The concentrated methane gas can be used as a raw material for city gas and a raw material for hydrogen used in fuel cells. In addition, when the separation layer has a site that attracts methane gas (hydrocarbon group having an ethyl group or more carbon number), when the digestion gas containing carbon dioxide and methane gas is passed, methane gas is selectively used in the gas induction layer. The methane gas permeates through the pores as it is. Therefore, in this case, methane gas that has permeated through the separation membrane can be recovered and used as a raw material for city gas or a raw material for hydrogen used in a fuel cell.

  Hereinafter, the Example regarding the separation membrane for acidic gas containing gas processing of this invention is described.

<Preparation of separation membrane>
A carbon dioxide separation membrane as a separation membrane was produced according to the “method for producing a separation membrane for treatment of acid gas-containing gas” described in the above embodiment. In the examples, colloidal silica “Snowtex (registered trademark)” series manufactured by Nissan Chemical Industries, Ltd. (for details, refer to the description of each example) is used as the colloidal silica used for forming the intermediate layer, and an organic solvent. 2-propanol (Wako Pure Chemical Industries, Ltd. reagent special grade 99.5%) was used. Further, common to all Examples and Comparative Examples, tetraethoxysilane (Shin-Etsu Chemical LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.) is used as tetraalkoxysilane, and methyltriethoxysilane (hydrocarbon group-containing trialkoxysilane ( Shin-Etsu Chemical Co., Ltd. Shin-Etsu Silicone LS-1890) is used, nitric acid (reagent grade 69.5%, manufactured by Wako Pure Chemical Industries, Ltd.) is used as the acid catalyst, and ethanol (Wako Pure Chemical Industries, Ltd.) is used as the organic solvent. Reagent special grade 99.5%) was used. Table 1 shows the composition of the raw materials used in Examples 1 to 4 and Comparative Examples 1 and 2.

[Example 1]
Prior to the production of the separation membrane, an intermediate layer forming silica sol (first mixed solution) and a separating layer forming alkoxide solution (second mixed solution) were prepared. In accordance with the composition shown in Table 1, a silica sol for forming an intermediate layer was prepared by stirring a mixed liquid of colloidal silica and 2-propanol for 2 hours. As the colloidal silica, colloidal silica (trade name: Snowtex (registered trademark) OXS) manufactured by Nissan Chemical Industries, Ltd. was used. Also, according to the formulation shown in Table 1, a mixture of water, nitric acid and ethanol was stirred for 30 minutes, then tetraethoxysilane was added and stirred for 1 hour, then methyltriethoxysilane was added and stirred for 2.5 hours. Then, magnesium acetate hexahydrate was added and stirred for 2 hours to prepare a separation layer forming alkoxide solution (second mixed solution).
The silica sol for forming an intermediate layer and the alkoxide solution for forming a separation layer prepared as described above were applied to an inorganic porous support to produce a carbon dioxide separation membrane having an intermediate layer and a separation layer. As an inorganic porous support, a ceramic filter “Cefilt (registered trademark)” (φ3-37 hole, molecular weight cut off 10,000) manufactured by NGK Corporation was used. This inorganic porous support is an alumina-based ceramic tubular body having a monolith structure. First, a silica sol for forming an intermediate layer was applied to the inner surface of the inorganic porous support by a dipping method (internal dipping method). Specifically, a silicone tube was connected to the top of the inorganic porous support, and a part of the tube was held between clips. After 200 g of the intermediate layer forming silica sol was poured into the tube, the clip was removed, and the intermediate layer forming silica sol was injected into the inorganic porous support to adhere to the inner surface of the inorganic porous support. Injection of the silica sol for forming the intermediate layer into the inorganic porous support was performed twice. After standing at room temperature for 1 hour, this series of operations was repeated twice, and heat treatment was performed in a calciner. The heat treatment was performed by heating from room temperature (25 ° C.) to 500 ° C. over 5 hours, holding at 500 ° C. for 2 hours, and cooling to 25 ° C. over 5 hours. The above operation (inner coating) was performed only once, and an intermediate layer was formed on the inner surface of the inorganic porous support. The coating amount of the intermediate layer was 175 mg, and the basis weight was 0.63 mg / cm ² . Next, an alkoxide solution for forming a separation layer was applied to the inner surface of the inorganic porous support having the intermediate layer formed thereon by a dipping method (internal dipping method). The dipping method was performed in the same manner as in the intermediate layer. The heat treatment conditions for the separation layer were heating from room temperature (25 ° C.) to 150 ° C. over 5 hours, holding at 150 ° C. for 2 hours, and cooling to 25 ° C. over 5 hours. The above operation (coating) was repeated 4 times to form a separation layer on the intermediate layer. The coating amount of the separation layer was 383 mg, and the basis weight was 1.37 mg / cm ² . Thus, the separation membrane of Example 1 was completed. For the separation membrane of Example 1, from the component analysis of Si by SEM-EDS, the penetration amount of the alkoxide solution into the tubular body (tetraalkoxysilane or hydrocarbon group-containing trialkoxy in the depth direction from the surface of the inorganic porous support) The distance by which silane soaked was 10 μm.

[Example 2]
An intermediate layer forming silica sol (first mixed solution) and a separating layer forming alkoxide solution (second mixed solution) are prepared, and these are applied and heat-treated on an alumina ceramic tubular body having a monolith structure as an inorganic porous support. And the carbon dioxide separation membrane provided with the intermediate | middle layer and separation layer of Example 2 was produced.
According to the formulation shown in Table 1, the intermediate layer forming silica sol and the separation layer forming alkoxide solution used in Example 2 were prepared in the same procedure as in Example 1. As the colloidal silica, colloidal silica (trade name: Snowtex (registered trademark) OXS) manufactured by Nissan Chemical Industries, Ltd. was used. Further, the intermediate layer coating operation was performed once and the separation layer coating operation was performed four times according to the same production procedure and production conditions as in Example 1 to complete the separation membrane of Example 2. In the separation membrane of Example 2, the coating amount of the intermediate layer was 145 mg, the basis weight was 0.52 mg / cm ² , the coating amount of the separation layer was 371 mg, and the basis weight was 1.33 mg / cm ² . The amount of the alkoxide solution soaked into the tubular body was 13 μm.

Example 3
An intermediate layer forming silica sol (first mixed solution) and a separating layer forming alkoxide solution (second mixed solution) are prepared, and these are applied and heat-treated on an alumina ceramic tubular body having a monolith structure as an inorganic porous support. And the carbon dioxide separation membrane provided with the intermediate | middle layer and separation layer of Example 3 was produced.
According to the formulation shown in Table 1, an intermediate layer forming silica sol and a separating layer forming alkoxide solution used in Example 3 were prepared in the same procedure as in Example 1. As the colloidal silica, colloidal silica (trade name: IPA-ST) manufactured by Nissan Chemical Industries, Ltd. was used. Further, the intermediate layer coating operation was performed twice and the separation layer coating operation was performed four times according to the same manufacturing procedure and manufacturing conditions as in Example 1 to complete the separation membrane of Example 3. The separation membrane of Example 3 had an intermediate layer coating amount of 149 mg and a basis weight of 0.53 mg / cm ² , a separation layer coating amount of 419 mg and a basis weight of 1.50 mg / cm ² . The amount of the alkoxide solution soaked into the tubular body was 25 μm.

Example 4
An intermediate layer forming silica sol (first mixed solution) and a separating layer forming alkoxide solution (second mixed solution) are prepared, and these are applied and heat-treated on an alumina ceramic tubular body having a monolith structure as an inorganic porous support. And the carbon dioxide separation membrane provided with the intermediate | middle layer and separation layer of Example 4 was produced.
In accordance with the formulation shown in Table 1, the intermediate layer forming silica sol and the separation layer forming alkoxide solution used in Example 4 were prepared in the same procedure as in Example 1. As the colloidal silica, colloidal silica (trade name: IPA-ST-UP) manufactured by Nissan Chemical Industries, Ltd. was used. Further, the intermediate layer coating operation was performed twice and the separation layer coating operation was performed four times according to the same manufacturing procedure and manufacturing conditions as in Example 1 to complete the separation membrane of Example 4. The separation membrane of Example 4 had an intermediate layer coating amount of 151 mg and a basis weight of 0.54 mg / cm ² , a separation layer coating amount of 427 mg and a basis weight of 1.53 mg / cm ² . The amount of the alkoxide solution soaked into the tubular body was 28 μm.

[Comparative Example 1]
An alkoxide solution for forming a separation layer was prepared, and this was applied and heat-treated on an alumina-based ceramic tubular body having a monolith structure that was an inorganic porous support to produce a carbon dioxide separation membrane of Comparative Example 1. Comparative Example 1 is a separation membrane having no intermediate layer.
According to the formulation of Table 1, a mixture of water, nitric acid and ethanol was stirred for 30 minutes, then tetraethoxysilane was added and stirred for 1 hour, then methyltriethoxysilane was added and stirred for 2.5 hours, Magnesium acetate hexahydrate was added and stirred for 2 hours to prepare a separation layer forming alkoxide solution.
The separation layer forming alkoxide solution was applied to the inner surface of the inorganic porous support by a dipping method (internal dipping method). The dipping method was performed in the same manner as in the case of the separation layer in Example 1. The heat treatment conditions for the separation layer were heating from room temperature (25 ° C.) to 150 ° C. over 5 hours, holding at 150 ° C. for 2 hours, and cooling to 25 ° C. over 5 hours. The above operation (coating) was repeated 8 times to form a separation layer on the inner surface of the inorganic porous support to complete the separation membrane of Comparative Example 1. The separation membrane of Comparative Example 1 did not have an intermediate layer, the coating amount of the separation layer was 655 mg, and the basis weight was 2.35 mg / cm ² . Moreover, the penetration amount of the alkoxide solution to the tubular body was 156 μm, and the penetration amount was larger than those in Examples 1 to 4.

[Comparative Example 2]
An alkoxide solution for forming a separation layer was prepared, and this was applied to an alumina-based ceramic tubular body having a monolith structure as an inorganic porous support and heat-treated to prepare a carbon dioxide separation membrane of Comparative Example 2. Comparative Example 2 is a separation membrane that does not have an intermediate layer.
According to the formulation shown in Table 1, the separation layer forming alkoxide solution used in Comparative Example 2 was prepared in the same procedure as Comparative Example 1. Further, the separation membrane of Comparative Example 2 was completed by the same production procedure and production conditions as Comparative Example 1. The separation membrane of Comparative Example 2 did not have an intermediate layer, the coating amount of the separation layer was 736 mg, and the basis weight was 2.64 mg / cm ² . Moreover, the penetration amount of the alkoxide solution to the tubular body was 123 μm, and the penetration amount was larger than in Examples 1 to 4.

<Separation performance confirmation test>
About the separation membrane of Examples 1-4 and Comparative Examples 1 and 2, the confirmation test regarding the separation performance of a carbon dioxide was done. In this confirmation test, the gas permeation rate [P (CO ₂ )] when carbon dioxide permeates the separation membrane and the gas permeation rate [P (N ₂ )] when nitrogen permeates the same separation membrane. It was measured. Here, the gas molecular diameter of nitrogen is 3.64 cm, and the gas molecular diameter of carbon dioxide is 3.3 cm. For this reason, carbon dioxide having a gas molecular diameter smaller than that of nitrogen easily passes through the separation membrane. Therefore, carbon dioxide can be separated from digestion gas containing carbon dioxide by utilizing different properties depending on such gas and further appropriately setting the structure of the membrane.

  FIG. 1 is a schematic configuration diagram of a gas permeation rate measuring apparatus 10 used in a separation performance confirmation test. The gas transmission rate measuring device 10 includes a gas cylinder 1, a pressure gauge 2, a chamber 3, and a mass flow meter 4. The separation membrane 5 is installed inside the chamber 3. The separation membrane 5 to be tested is a tubular body (Examples 1 to 4) in which an intermediate layer and a separation layer are formed on the inner surface of an alumina tube having a monolith structure, or a tubular body in which only a separation layer is formed (Comparative Example 1 and 2).

Carbon dioxide or nitrogen, which is a measurement gas, is filled in the gas cylinder 1 in advance. Here, it demonstrates as what filled the gas cylinder 1 with the carbon dioxide. The pressure of the carbon dioxide discharged from the gas cylinder 1 is adjusted by the pressure gauge 2 and supplied to the chamber 3 on the downstream side. In this confirmation test, the supply pressure of carbon dioxide was adjusted to 0.1 MPa at room temperature. The separation membrane 5 which is a tubular body is configured such that one end (front end side) 5a is sealed and carbon dioxide can flow into the inside of the separation membrane 5 from the other end (base end side) 5b. One end 5a of the separation membrane 5 is completely sealed by an epoxy resin (two-component epoxy adhesives “AV138” and “HV998” manufactured by Nagase ChemteX Corporation), and the other end 5b is made of carbon dioxide by the epoxy resin. Sealed so as not to block the inlet. Further, an O-ring 7 is attached to one end 5 a and the other end 5 b of the separation membrane 5, and the separation membrane 5 is fixed inside the chamber 3. A heat-resistant glass tube 6 (Pyrex (registered trademark) tube (external diameter: 8 mm, internal diameter: 6 mm, length: 10 mm) manufactured by Corning) is connected to the chamber 3, and the gas discharged from the inside of the separation membrane 5 to the outside is It is guided to the mass flow meter 4 through the heat resistant glass tube 6. As the mass flow meter 4, a thermal mass flow meter (mass flow meter “5410”) manufactured by Cofrock was used. The measurement conditions were a flow rate range of 500 mL / min and an accuracy with respect to the full-scale (FS) maximum flow rate of ± 1% (20 ° C.). From the flow rate [mL / min] of carbon dioxide measured with the mass flow meter 4, the gas permeation rate of carbon dioxide [P (CO ₂ )] (m ³ / (m ² × s (seconds) × Pa)) was calculated. . For nitrogen, the gas permeation rate [P (N ₂ )] (m ³ / (m ² × s (seconds) × Pa)) was calculated by the same procedure as described above. The carbon dioxide gas permeation rate [P (CO ₂ )] and the nitrogen gas permeation rate [P (N ₂ )] are compared with the permeation rate ratio [α (CO ₂ / N ₂ )]. Separation performance was evaluated. The results of the separation performance confirmation test are shown in Table 2.

  As shown in Table 2, the separation membrane including the intermediate layer and the separation layer of Examples 1 to 4 had excellent carbon dioxide permeability to nitrogen. In contrast, the separation membranes of Comparative Examples 1 and 2 having only the separation layer without providing the intermediate layer did not have sufficient carbon dioxide permeability to nitrogen. When Examples and Comparative Examples were compared, a difference of about 3 to 14 times in the permeation rate ratio between carbon dioxide and nitrogen was confirmed.

  As mentioned above, since the separation membrane for gas treatment of an acid gas of the present invention is excellent in at least carbon dioxide separation performance, carbon dioxide is efficiently produced from digestion gas obtained by biological treatment of garbage etc. It was suggested that methane gas could be concentrated to useful concentrations by separating well.

  The separation membrane for treatment of acid gas-containing gas and the method for producing the same of the present invention can be used in city gas production facilities, hydrogen supply facilities for fuel cells, and the like. Furthermore, the present invention can also be applied to exhaust gas, natural gas, gas by-produced in petroleum refining, etc. discharged from factories and power plants.

DESCRIPTION OF SYMBOLS 1 Gas cylinder 2 Pressure gauge 3 Chamber 4 Mass flow meter 5 Separation membrane 6 Heat-resistant glass tube 7 O-ring 10 Gas permeation rate measuring device

Claims (11)

An inorganic porous support;
An intermediate layer comprising a silica fine particle conjugate formed on the surface of the inorganic porous support;
A separation layer comprising a hydrocarbon group-containing polysiloxane network formed on the intermediate layer;
An acid gas-containing separation membrane for gas treatment. The silica fine particle combination is a single structure obtained by a sintering reaction of colloidal silica,
The separation membrane for acid gas-containing gas treatment according to claim 1, wherein the hydrocarbon group-containing polysiloxane network structure is a composite structure obtained by a sol-gel reaction of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane. . The tetraalkoxysilane is tetramethoxysilane or tetraethoxysilane,
The said hydrocarbon group containing trialkoxysilane is a gas atom processing gas-containing gas treatment according to claim 2, wherein an alkyl group or phenyl group having 1 to 6 carbon atoms is bonded to Si atom of trimethoxysilane or triethoxysilane. Separation membrane.   The separation membrane for acid gas-containing gas treatment according to any one of claims 1 to 3, wherein a metal salt having an affinity for acid gas is added to the separation layer.   The metal salt is an acetate, nitrate, carbonate, borate, or phosphate of at least one metal selected from the group consisting of Li, Na, K, Mg, Ca, Ni, Fe, and Al. The separation membrane for acidic gas containing gas treatment according to claim 4. The basis weight of the intermediate layer is 0.1 to 3.0 mg / cm ² ,
The basis weight of the separating layer, acid gas-containing gas treating separation membrane according to any one of claims 1 to 5 is 0.1~4.0mg / cm ^2.   The said inorganic porous support body is a separation membrane for acidic gas containing gas processing as described in any one of Claims 1-6 which has a 4-200 nm micropore.   The acidic gas according to any one of claims 1 to 7, wherein a distance that the tetraalkoxysilane or the hydrocarbon group-containing trialkoxysilane penetrates in a depth direction from the surface of the inorganic porous support is 50 µm or less. Separation membrane for gas treatment. (A) A preparatory step of preparing a first mixed liquid in which colloidal silica and an organic solvent are mixed, and a second mixed liquid in which tetraalkoxysilane, hydrocarbon group-containing trialkoxysilane, acid catalyst, water, and organic solvent are mixed. When,
(B) a first coating step of coating the first mixed liquid on the surface of the inorganic porous support;
(C) An intermediate layer forming step of heat-treating the inorganic porous support after the first application step and forming an intermediate layer containing a silica fine particle combination on the surface of the inorganic porous support;
(D) a second coating step of coating the second mixed solution on the intermediate layer;
(E) a separation layer forming step of heat-treating the inorganic porous support having undergone the second coating step to form a separation layer containing a hydrocarbon group-containing polysiloxane network structure on the intermediate layer;
The manufacturing method of the separation membrane for acidic gas containing gas processing including this.   The manufacturing method of the separation membrane for acidic gas containing gas treatment of Claim 9 which repeats said 1st application | coating process and said intermediate | middle layer formation process several times by setting both processes as a set.   The method for producing a separation membrane for acid gas-containing gas treatment according to claim 9 or 10, wherein the second coating step and the separation layer forming step are repeated a plurality of times with both steps as a set.

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