JP2019042681A - Separation membrane for treating acid gas-containing gas - Google Patents

Abstract

To provide a separation membrane for treating acid gas-containing gas which exhibits excellent gas separation performance and throughput of gas.SOLUTION: A separation membrane 100 for treating acid gas-containing gas separates acid gas from acid gas-containing gas, and includes a support body 10 which has a plurality of inorganic porous layers of which pore sizes are different from each other, and a hydrocarbon group-containing polysiloxane network structure 20 which has affinity for the acid gas. The support body 10 includes a first layer 11 of which a pore size is minimum among the plurality of inorganic porous layers and which is arranged on a surface side. The hydrocarbon group-containing polysiloxane network structure 20 is introduced as an intermediate layer 21 and a separation layer 22 into pores 11a of the first layer 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an acid gas-containing gas treatment separation membrane for separating an acid gas from an acid gas-containing gas.

  In the industrial field, the medical field, the food field, and the like, technological development for obtaining high-concentration gas is actively performed. For example, the exhaust gas discharged from factories and power plants contains nitrogen and carbon dioxide. If carbon dioxide can be selectively separated from this exhaust gas, the utility value of the treated gas will increase, and it will be a countermeasure against global warming. Can also contribute. In addition, air contains about 20% oxygen, but if oxygen can be selectively separated from air, a large amount of oxygen can be efficiently used without depending on methods such as electrolysis of water that consumes a lot of energy. Can be obtained. Therefore, research and development have been conventionally conducted on gas separation membranes that selectively separate a specific gas from a mixed gas.

  As a typical film forming method of the gas separation layer, there is a film forming method by a sol-gel method using a metal alkoxide as a raw material (see, for example, Patent Document 1). In the porous composite of Patent Document 1, a suspension (sol) containing silicon alkoxide is applied to a porous support and dried and fired to form silica particles (gel) on the surface of the porous support. To do.

  A method of forming a gas separation layer by a gas phase reaction (CVD method) of a source gas is also known (see, for example, Patent Document 2). In forming a gas separation layer on the surface of an α-alumina porous body, the gas separation material of Patent Document 2 vents oxygen gas through the α-alumina porous body in the presence of a silica precursor gas, The alumina porous body is heated to form a silica film as a gas separation layer.

JP 2002-293656 A International Publication No. 2014/007140

  In order to obtain a gas separation membrane having excellent gas separation performance and gas throughput, an inorganic porous support having an appropriate structure is selected, and a method for forming a gas separation layer on the inorganic porous support is selected. It is necessary to devise. In this regard, the gas separation membrane obtained by using the sol-gel method of Patent Document 1 is manufactured by a so-called dipping method, so that a large-scale manufacturing apparatus is unnecessary and can be implemented relatively easily. When the raw material liquid is applied, the raw material liquid permeates excessively into the inorganic porous support, and as a result, the pores of the inorganic porous support are clogged, resulting in a processing capability (gas permeation flow rate) as a gas separation membrane. It was inferior.

  Since the gas separation material of Patent Document 2 forms a gas separation membrane by the CVD method, the raw material gas may penetrate deep into the pores of the inorganic porous support, resulting in a decrease in air permeability. It was. Further, in the CVD method, when the length of the inorganic porous support serving as a reaction field of the source gas becomes a certain length or more, a gas phase reaction (film formation) at a position away from the inflow portion of the source gas becomes difficult. In such a case, a uniform membrane cannot be formed on the entire inorganic porous support, and the processing performance (gas separation capability) as a gas separation membrane may be insufficient.

  This invention is made | formed in view of the said problem, and it aims at providing the separation membrane for acidic gas containing gas processing excellent in gas separation performance and gas throughput.

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 acid gas-containing gas treatment separation membrane for separating an acid gas from an acid gas-containing gas,
A support having a plurality of inorganic porous layers having different pore diameters;
A hydrocarbon group-containing polysiloxane network having an affinity for the acid gas;
With
In the support, a first layer having a minimum pore diameter among the plurality of inorganic porous layers is disposed on the surface side, and the hydrocarbon group-containing polysiloxane network structure is formed in the pores of the first layer. The body is introduced as an intermediate layer and a separation layer.

  According to the separation membrane for acid gas-containing gas treatment of this configuration, a support having a plurality of inorganic porous layers having different pore diameters is used as a base, and a plurality of inorganic porous layers are formed on the surface side. When the hydrocarbon layer-containing polysiloxane network structure is introduced into the support by disposing the first layer having the smallest pore diameter, the raw material silane alkoxide solution permeates the support excessively. There is nothing. As a result, the generated separation membrane for acid gas-containing gas treatment has sufficient air permeability and high treatment capacity (gas permeation flow rate). Further, since the hydrocarbon group-containing polysiloxane network structure is introduced into the pores of the first layer on the surface side of the support as an intermediate layer and a separation layer, the acidic gas-containing gas to be treated is a hydrocarbon group-containing polysiloxane. Efficient contact with the siloxane network. As a result, the acidic gas-containing gas treatment separation membrane can exhibit excellent treatment performance (gas separation ability).

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
In the support, the hydrocarbon group-containing polysiloxane network structure is preferably not introduced into the pores of layers other than the first layer.

  According to the separation membrane for acid gas-containing gas treatment of this configuration, the hydrocarbon group-containing polysiloxane network structure is not introduced into the pores of the layers other than the first layer, so that only near the surface of the support. Therefore, after the acidic gas-containing gas to be treated comes into contact with the hydrocarbon group-containing polysiloxane network structure, it is quickly discharged outside through the inorganic porous support. As a result, the acidic gas-containing gas treatment separation membrane can achieve both excellent gas permeation flow rate and gas separation ability.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
In the support, the hydrocarbon group-containing polysiloxane network structure is preferably introduced inward from the opening positions of the pores of the first layer.

  According to the separation membrane for treatment of acid gas-containing gas of this configuration, the hydrocarbon group-containing polysiloxane network structure is introduced inside the opening positions of the pores of the first layer, so that the intermediate layer and the separation layer Completely fits inside the pore. Therefore, even if the introduction amount of the hydrocarbon group-containing polysiloxane network structure to the support is minimal, the acid gas-containing gas does not form pores while being in contact with almost all the hydrocarbon group-containing polysiloxane network structure. It is possible to achieve maximum processing efficiency.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
In the support, the hydrocarbon group-containing polysiloxane network structure is preferably configured as a reaction product of a hydrocarbon group-containing trialkoxysilane and tetraalkoxysilane.

  According to the separation membrane for acid gas-containing gas treatment of this configuration, since an appropriate alkoxysilane is used as a raw material for the hydrocarbon group-containing polysiloxane network structure, a gas separation membrane having excellent acid gas separation performance and Become.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
In the support, the hydrocarbon group-containing polysiloxane network structure preferably includes a metal salt having an affinity for the acidic gas.

  According to the separation membrane for treating an acidic gas-containing gas of this configuration, the acidic gas contained in the acidic gas-containing gas is attracted to the metal salt, so that the separation performance of the gas separation membrane can be further enhanced.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The pore diameter of the first layer is preferably 120 to 200 nm.

  According to the acidic gas-containing gas treatment separation membrane of this configuration, when the pore diameter of the first layer is 120 to 200 nm, the silane alkoxide solution serving as the raw material of the hydrocarbon group-containing polysiloxane network structure is It remains in the vicinity of the surface, and as a result, a thin and uniform hydrocarbon group-containing polysiloxane network structure is formed on the support as an intermediate layer and a separation layer. Such an acid gas-containing gas treatment separation membrane has a further improved gas separation ability.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The pore diameter of the layer positioned below the first layer is preferably 1 to 1.7 μm.

  According to the acidic gas-containing gas treatment separation membrane of this configuration, the gas permeation flow rate of the gas separation membrane is kept higher by the pore diameter of the layer located below the first layer being 1 to 1.7 μm. be able to. Moreover, since the pore diameter of the layer located below the first layer is sufficiently larger than the pore diameter of the first layer, the pressure loss when the acid gas-containing gas to be treated is vented is small, and the gas for gas treatment This will increase the life of the separation membrane.

In the separation membrane for treatment of acid gas-containing gas according to the present invention,
The support preferably has an effective length of 50 mm or more.

  According to the acidic gas-containing gas treatment separation membrane of this configuration, even if the effective length of the support is 50 mm or more, the hydrocarbon group-containing polysiloxane network structure is uniformly introduced near the entire surface of the support. . As a result, the acidic gas-containing gas treatment separation membrane can achieve both excellent gas permeation flow rate and gas separation ability.

It is a schematic diagram of the separation membrane for acidic gas containing gas processing. It is a schematic block diagram of the gas permeation rate measuring apparatus used for the separation performance confirmation test. It is a graph which shows the change of each characteristic in the middle of preparation of the separation membrane for acid gas containing gas processing.

  The separation membrane for treatment of acid gas-containing gas of the present invention uses a mixed gas containing acid gas and methane gas and / or nitrogen gas (hereinafter sometimes referred to as “acid gas-containing gas”) as a treatment target. However, in this specification, a mixed gas of acid gas and methane gas will be described as an example. Here, the acidic gas is a gas that shows acidity when dissolved in water, and examples thereof include carbon dioxide and hydrogen sulfide. In the present specification, carbon dioxide is assumed as the acidic gas, and the following description will be given. Accordingly, the acidic gas-containing gas treatment separation membrane of the present invention will be described as a carbon dioxide separation membrane for separating carbon dioxide. However, as a methane gas separation membrane for separating methane gas, a nitrogen gas separation membrane for separating nitrogen gas, or a carbon dioxide / (methane gas and / or nitrogen gas) separation membrane capable of simultaneously separating carbon dioxide and methane gas and / or nitrogen gas. It is also possible to configure. Hereinafter, the separation membrane for treatment of acid gas-containing gas may be simply referred to as “separation membrane”. Note that the present invention is not intended to be limited to the configurations described below.

<Separation membrane for acid gas containing gas treatment>
FIG. 1 is a schematic diagram of an acid gas-containing gas treatment separation membrane 100 of the present invention. FIG. 1A shows the entire acidic gas-containing gas processing separation membrane 100, and FIG. 1B shows a part of the cross section of the acidic gas-containing gas processing separation membrane 100. The acidic gas-containing gas treatment separation membrane 100 includes an inorganic porous support 10 serving as a base, and a hydrocarbon group-containing polysiloxane network 20 having an affinity for acidic gas.

[Inorganic porous support]
The inorganic porous support 10 is composed of a plurality of inorganic porous layers having different pore diameters. FIG. 1 shows an inorganic porous support 10 including a first layer 11 located on the surface side and a second layer 12 located below the first layer 11. Note that the sizes of the first layer 11 and the second layer 12 shown in FIG. 1B are exaggerated for convenience of explanation, and do not reflect the actual scale of the structure as it is. The inorganic porous support 10 used in the present invention only needs to have at least a two-layer structure. The pore diameter (D1 in the figure) of the first layer 11 is set to nano order, and is preferably 120 to 200 nm. The thickness of the first layer 11 (A1 in the figure) is preferably 10 to 80 μm. If the pore diameter and thickness of the first layer 11 are in the above ranges, when the inorganic porous support 10 is produced, the silane alkoxide solution that is the raw material of the hydrocarbon group-containing polysiloxane network structure 20 described later is inorganic. The acidic gas-containing gas treatment separation membrane 100 that remains in the vicinity of the surface of the porous support 10 and has a thin and uniform intermediate layer and separation layer can be obtained. The pore diameter (D2 in the figure) of the second layer 12 is set to the micron order, and is preferably 1 to 1.7 μm. The thickness of the second layer 12 (A2 in the figure) is preferably 1 to 2 mm. If the pore diameter and thickness of the second layer 12 are in the above ranges, the gas permeation flow rate of the acidic gas-containing gas treatment separation membrane 100 can be maintained large. In addition, since the pore diameter of the second layer 12 is sufficiently larger than the pore diameter of the first layer 11, the pressure loss when the acidic gas-containing gas to be treated is passed through the acidic gas-containing gas treatment separation membrane 100 is reduced. This can lead to a longer life of the separation membrane 100 for gas treatment containing acid gas.

  The first layer 11 and the second layer 12 of the inorganic porous support 10 are made of, for example, materials such as silica-based ceramics, silica-based glass, alumina-based ceramics, stainless steel, titanium, and silver. Among these, alumina-based ceramics are suitable as a material for the inorganic porous support 10 because they are excellent in heat resistance, easy to process, and relatively inexpensive. The inorganic porous support 10 is provided with an inflow portion into which gas flows and an outflow portion from which gas flows out. For example, the gas inflow portion is the outer surface 10a of the inorganic porous support, and the gas outflow portion is an opening 10b provided on one end side of the inorganic porous support. The opening 10b provided on one end side of the inorganic porous support 10 may be a gas inflow portion, and the outer surface 10a of the inorganic porous support 10 may be a gas outflow portion. Innumerable pores 11a are formed on the outer surface 10a of the inorganic porous support 10, and gas flows between the outside and the inside of the inorganic porous support 10 through the pores 11a. Can do. Here, the effective length of the inorganic porous support 10 is 50 mm or more when the length in the tube axis direction of the portion through which the gas can flow out of the outer surface 10a of the inorganic porous support 10 is defined as the effective length. It is preferable to set.

  Examples of the configuration of the inorganic porous support 10 include a cylindrical structure having a gas flow path therein, a circular tube structure, a tubular structure, a spiral structure, and a large number of flow paths such as lotus holes in one element. Monolithic structure with a solid structure, a continuous structure in which continuous pores that are intricately interlaced are formed, a solid porous structure in which a porous body is formed into a columnar shape, and a hollow porous structure in which a porous body is formed into a cylindrical shape And a honeycomb structure in which honeycomb structures are arranged in a tubular shape. It is also possible to form the inorganic porous support 10 by preparing a solid flat body or bulk body made of an inorganic porous material and forming a gas flow path by hollowing out a part thereof. It is.

[Hydrocarbon group-containing polysiloxane network]
The hydrocarbon group-containing polysiloxane network structure 20 forms an intermediate layer 21 and a separation layer 22 inside the pores 11 a of the first layer 11 of the inorganic porous support 10. Here, the intermediate layer 21 and the separation layer 22 are not necessarily present in a layered form. For example, in the inside of the pores 11a of the first layer 11, the intermediate layer 21 and the separation layer 22 are mixed substantially evenly, or one of the intermediate layer 21 and the separation layer 22 is present more than the other, In this specification, the state where the other is scattered in the layer is also treated as the intermediate layer 21 and the separation layer 22.

  The hydrocarbon group-containing polysiloxane network structure 20 is introduced inside the opening positions of the pores 11a of the first layer 11 of the inorganic porous support 10 as shown in FIG. It is not introduced into the pores 12a of the bilayer 12. That is, the hydrocarbon group-containing polysiloxane network structure 20 is formed as the intermediate layer 21 and the separation layer 22 only in the first layer 11 of the inorganic porous support 10. Such an acidic gas-containing gas treatment separation membrane 100 is configured to minimize the amount of the hydrocarbon group-containing polysiloxane network structure 20 introduced into the inorganic porous support 10 while keeping the acidic gas-containing gas treatment separation membrane 100. When the acidic gas-containing gas is allowed to pass through, the acidic gas-containing gas passes through the pores 11a while being in contact with almost all the hydrocarbon group-containing polysiloxane network structure 20 in the first layer 11, and is acidic in the first layer 11. The gas after the gas is separated further passes through the pores 12a of the second layer 12, so that the maximum processing efficiency can be realized. Further, in the separation membrane 100 for treating an acidic gas-containing gas of the present invention, the hydrocarbon group-containing polysiloxane network structure 20 remains only in the vicinity of the surface of the inorganic porous support 10, so that the acidic gas-containing gas to be treated is present. After contacting with the hydrocarbon group-containing polysiloxane network structure 20, it is quickly discharged to the outside through the inorganic porous support 10. As a result, the acidic gas-containing gas treatment separation membrane 100 can achieve both excellent gas permeation flow rate and gas separation ability. Hereinafter, the intermediate layer 21 and the separation layer 22 constituting the hydrocarbon group-containing polysiloxane network structure 20 will be described.

  The intermediate layer 21 is provided mainly to stabilize the inner surface of the pores 11a of the first layer 11 of the inorganic porous support 10 and to facilitate the introduction of a separation layer 22 described later. For example, when the size of the pores 11a of the first layer 11 of the inorganic porous support 10 is relatively large, a liquid mixture (sol) containing the material for forming the separation layer 22 is directly applied to the surface of the inorganic porous support 10. When applied, the mixed solution may permeate excessively into the pores 11a and not stay near the surface of the inorganic porous support 10, and film formation may be difficult. Therefore, by providing the inorganic porous support 10 with the intermediate layer 21, the inlet of the pores 11a is narrowed by the intermediate layer 21, and the application of the mixed liquid becomes easy. In addition, since the inner surface of the pores 11a of the inorganic porous support 10 is equalized by the intermediate layer 21, peeling and cracking of the separation layer 22 introduced thereafter can be suppressed.

  The intermediate layer 21 is configured to include a silane compound. The intermediate layer 21 of this embodiment 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 tetraalkoxysilane of the formula (1) and a hydrocarbon group-containing trialkoxysilane of the formula (2) are subjected to a sol-gel reaction, for example, a hydrocarbon group having a molecular structure represented by the following formula (3) A containing polysiloxane network structure is obtained.

The hydrocarbon group-containing trialkoxysilane of formula (2), which is one of the raw materials of the hydrocarbon group-containing polysiloxane network structure of formula (3), has different characteristics depending on 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 hydrocarbon group-containing polysiloxane network structure of the formula (3) from the reaction between the tetraalkoxysilane of the formula (1) and the hydrocarbon group-containing trialkoxysilane of the formula (2), the tetraalkoxy is synthesized. When silane (referred to as A) and hydrocarbon group-containing trialkoxysilane (referred to as B) are set to an optimum blending ratio, a separation membrane excellent in carbon dioxide or methane gas separation performance is formed. Is possible.

In introducing the intermediate layer 21 into the pores 11a, the mixing ratio (A1 / B1) of the tetraalkoxysilane (A1) to the hydrocarbon group-containing trialkoxysilane (B1) is 30/70 to 99.9 by weight. /0.1, preferably 60/40 to 99.9 / 0.1, the tetraalkoxysilane of the formula (1) and the hydrocarbon group-containing trialkoxysilane of the formula (2) are blended. In this case, since the intermediate layer 21 contains a hydrocarbon group derived from a hydrocarbon group-containing trialkoxysilane, the intermediate layer 21 is more flexible than a general network structure and maintains a certain degree of rigidity by the tetraalkoxysilane. However, overall flexibility and flexibility can be improved. As a result, the intermediate layer 21 is stabilized and the film formability of the separation layer 22 described later is improved. In the hydrocarbon group-containing polysiloxane network structure of the formula (3), the hydrocarbon group R ₅ is present in the polysiloxane network structure and forms a certain organic-inorganic composite. In addition, since the intermediate layer 21 contains a hydrocarbon group similarly to the later-described separation layer 22, it also has an ability to selectively attract carbon dioxide.

  The separation layer 22 mainly has a function of selectively attracting and separating carbon dioxide from a mixed gas containing carbon dioxide and methane gas and / or nitrogen gas. The separation layer 22 is obtained by a sol-gel reaction of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane.

The tetraalkoxysilane and the hydrocarbon group-containing trialkoxysilane are the tetraalkoxysilane represented by the above formula (1) and the hydrocarbon group-containing trialkoxy represented by the formula (2) used for introducing the intermediate layer 21. The same silane can be used. A preferred tetraalkoxysilane is the same as the intermediate layer, and in formula (1), R _{1 to} R ₄ are the same methyl group tetramethoxysilane (TMOS) or the same ethyl group tetraethoxysilane (TEOS). It is. For even preferred hydrocarbon group-containing trialkoxysilane is similar to the intermediate layer 21, in the formula (2), triethoxysilane R ₆ to R ₈ is a trimethoxysilane or identical ethyl group are the same methyl group And an alkyl group having 1 to 6 carbon atoms or a phenyl group bonded to the Si atom.

  Also in the separation layer 22, the molecular structure represented by the above-described formula (3) is obtained by causing a sol-gel reaction between the tetraalkoxysilane of the formula (1) and the hydrocarbon group-containing trialkoxysilane of the formula (2). A hydrocarbon group-containing polysiloxane network having the following structure is obtained. In introducing the separation layer 22 into the pores 11a, the blending ratio (A2 / B2) of the tetraalkoxysilane (A2) to the hydrocarbon group-containing trialkoxysilane (B2) is 0/100 to 70/30 by weight. The tetraalkoxysilane of the formula (1) and the hydrocarbon group-containing trialkoxysilane of the formula (2) are blended so that the ratio is preferably 40/60 to 70/30. Further, when the intermediate layer 21 and the separation layer 22 are introduced, the tetraalkoxysilane is such that the blending ratio (A1 / B1) when the intermediate layer is introduced is greater than the blending ratio (A2 / B2) when the separation layer is introduced. And a hydrocarbon group-containing trialkoxysilane. In this case, since the separation layer 22 contains more hydrocarbon groups derived from the hydrocarbon group-containing trialkoxysilane than the intermediate layer 21, the acidic gas in the mixed gas is selectively attracted to the separation layer 22, Separation of the acidic gas from the mixed gas can be performed efficiently.

  It is preferable to add a metal salt having an affinity for carbon dioxide to the hydrocarbon group-containing polysiloxane network structure of the above formula (3). Thereby, the said metal salt is contained in the separation layer 22, and the separation performance of the separation membrane 22 can further be improved. Of course, the metal salt can be added to the intermediate layer 21. As the metal salt, acetate, nitrate, carbonate, borate, or phosphoric acid of at least one metal selected from the group consisting of Li, Na, K, Cs, Mg, Ca, Ni, Fe, and Al Salt. Of these, magnesium nitrate or magnesium acetate is preferred. Since the above metal salts including magnesium nitrate have good affinity with carbon dioxide, they are effective in improving the separation efficiency of carbon dioxide. The addition of the metal salt to the hydrocarbon group-containing polysiloxane network structure 20 is easy by previously mixing the metal salt with the raw material of the hydrocarbon group-containing polysiloxane network structure. Impregnation in which the inorganic porous support 10 into which the siloxane network structure 20 is introduced is immersed in an aqueous solution containing a metal salt, and the metal salt is impregnated alone or together with other substances inside the hydrocarbon group-containing polysiloxane network structure 20. It can also be done by law.

<Method for producing separation membrane for treatment of acid gas-containing gas>
The acidic gas-containing gas treatment separation membrane 100 of the present invention is manufactured by the following steps (a) to (e).

(A) Preparatory process As a preparatory process, the compounding ratio (A1 / B1) of tetraalkoxysilane (A1) and hydrocarbon group containing trialkoxysilane (B1) is 30 / 70-99.9 / 0.1 by weight ratio. A first mixed solution is prepared by mixing the alkoxysilane, acid catalyst, water, and organic solvent prepared in the above step. The first liquid mixture is used in the “first coating step” of the next step. Each compounding amount of alkoxysilane (tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane), acid catalyst, water, and organic solvent is based on 1 mol of the total amount of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane. The acid catalyst is preferably adjusted to 0.001 to 0.1 mol, water 0.5 to 60 mol, and organic solvent 5 to 60 mol. When the compounding amount of the acid catalyst is less than 0.001 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, a sol-gel reaction product accompanied by a hydrolysis reaction does not grow sufficiently. When the amount of water is more than 60 mol, the film formability is deteriorated. When the blending amount of the organic solvent is less than 5 mol, the concentration of the first 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 first 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 the first mixed solution is prepared, first, a sol-gel reaction in which tetraalkoxysilane repeats hydrolysis and polycondensation starts. 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.

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。ここで、第一混合液中で進行する加水分解反応を「第一加水分解反応」とする。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。上記の第一加水分解反応、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。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、有機溶媒を含む第一混合液に溶解した状態にある。

According to Scheme 1, first, a part of ethoxy groups of tetraethoxysilane are hydrolyzed and dealcoholized to produce silanol groups. Here, the hydrolysis reaction proceeding in the first mixed solution is referred to as “first hydrolysis reaction”. 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 first hydrolysis reaction and the dehydration / polycondensation reaction proceed substantially evenly in the mixed liquid system, the silanol group or ethoxy group exists in a substantially uniformly dispersed state in the siloxane skeleton. 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 first mixed liquid containing the organic solvent.

  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.

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メチル基もポリシロキサン結合中に略均等に存在する。そして、反応がさらに進行すると、微細化されたポリシロキサン網目構造体が液中に分散した懸濁液の状態となる。

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 uniformly in the generated polysiloxane bond, and therefore methyl groups derived from methyltriethoxysilane are also present almost uniformly in the polysiloxane bond. When the reaction further proceeds, a finely divided polysiloxane network structure is in a suspension state dispersed in the liquid.

  In the preparation step, the blending ratio (A2 / B2) of the tetraalkoxysilane (A2) and the hydrocarbon group-containing trialkoxysilane (B2) is 0/100 to 70 / weight ratio in addition to the first mixed liquid. A second mixed solution obtained by mixing alkoxysilane adjusted to 30 with an acid catalyst, water, and an organic solvent is further prepared. A 2nd liquid mixture is used in the below-mentioned "2nd application | coating process." Each compounding amount of alkoxysilane (tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane), acid catalyst, water, and organic solvent is based on 1 mol of the total amount of tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane. The acid catalyst is preferably adjusted to 0.005 to 0.1 mol, water 0.017 to 3 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. The blending amount of water is set to be smaller than that of the first mixed solution, but when the blending amount of water is less than 0.017 mol, the hydrolysis rate becomes small and the sol-gel reaction described later does not proceed sufficiently. When the amount of water is more than 3 mol, it becomes difficult to obtain a dense and uniform 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 and the organic solvent, those similar to the first mixed liquid can be used. 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. When a metal salt is added, it is considered that the metal salt taken into the polysiloxane during the sol-gel reaction is dispersed substantially evenly in the polysiloxane bond.

  In preparing the first mixed liquid and the second mixed liquid, the blending ratio (A1 / B1) at the time of preparing the first mixed liquid is larger than the blending ratio (A2 / B2) at the time of preparing the second mixed liquid. Thus, tetraalkoxysilane and hydrocarbon group-containing trialkoxysilane are blended. With such a composition, the separation membrane finally obtained contains more hydrocarbon groups derived from the hydrocarbon group-containing trialkoxysilane in the separation layer than in the intermediate layer. The balance between the separation performance and the film formability is good.

  The reaction of the second mixed solution is the same as in the above-described scheme 1 and scheme 2. The hydrolysis reaction that proceeds in the second mixed solution is referred to as “second hydrolysis reaction”. Here, when the first hydrolysis reaction and the second hydrolysis reaction are compared, the amount of water contained in the first mixed solution is set to be greater than the amount of water contained in the second mixed solution. The hydrolysis reaction has a higher hydrolysis rate than the second hydrolysis reaction. When the hydrolysis rate increases, the polymerization of the hydrocarbon group-containing polysiloxane network obtained by the sol-gel reaction proceeds, and the inner surface of the pores 11a of the inorganic porous support 10 may be stabilized. it can.

  Although the preparation step is performed as described above, in the preparation of the first mixed solution, it is preferable to mix water in a plurality of times. In this case, since a 1st hydrolysis reaction can be advanced reliably, the inner surface of the pore 11a of the inorganic porous support body 10 can be stabilized more. In preparation of the first mixed liquid and the second mixed liquid, the acid catalyst should be mixed in a plurality of times, or the hydrocarbon group-containing trialkoxysilane which is easily hydrolyzed is mixed at the end. Is preferred. 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 mixed solution 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. Furthermore, when the amount of water used for the preparation of the first mixed solution is W1 and the amount of water used for the preparation of the second mixed solution is W2, the ratio (W1 / W2) between them is 10 in terms of mole. It is preferable to set to ~ 20. In this case, the intermediate 21 layer is further stabilized, and the gas selectivity and gas permeability of the separation layer 22 can be improved.

(B) First Application Step As the first application step, the first mixed liquid (suspension of the refined polysiloxane network structure) obtained in the preparation step is applied to the inorganic porous support 10. Examples of the method for applying the first mixed liquid to the inorganic porous support 10 include a 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 outer surface 10 a of the inorganic porous support 10. A specific procedure of the dipping method will be described.
First, the inorganic porous support 10 is immersed in the first mixed solution. The dipping time is preferably 5 seconds to 10 minutes so that the first mixed liquid sufficiently adheres to the inorganic porous support 10. If the immersion time is shorter than 5 seconds, the film thickness is not sufficient, and if it exceeds 10 minutes, the film thickness becomes too large. Next, the inorganic porous support 10 is pulled up from the first mixed solution. The pulling speed is preferably 0.1 to 7 mm / second. When the pulling speed is slower than 0.1 mm / second, the film thickness is not sufficient, and when it is faster than 7 mm / second, the film thickness becomes too large. Next, the pulled up inorganic porous support 10 is dried. The drying conditions are preferably 15 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 completed, a fine polysiloxane network structure adhered to the inside of the pores 11a of the first layer 11 of the inorganic porous support 10 is obtained. In addition, the adhesion amount of the refined polysiloxane network structure to the inorganic porous support 10 can be increased by repeating a series of steps of dipping, pulling up and drying the inorganic porous support 10 a plurality of times. it can. Moreover, since the first mixed solution can be uniformly applied to the inorganic porous support 10 by repeating a series of procedures, the finally obtained separation membrane 100 for gas treatment containing acid gas can be made more stable. Can do.

(C) Intermediate layer forming step As the intermediate layer forming step, the inorganic porous support 10 that has completed the first application step is heat-treated, and fine particles are formed inside the pores 11a of the first layer 11 of the inorganic porous support 10. The intermediate layer 21 having the hydrocarbon group-containing polysiloxane network structure as a main material is formed by fixing or fusing the converted polysiloxane network structure. 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 10 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 30 to 300 ° C, more preferably 50 to 200 ° C. If the heat treatment temperature is lower than 30 ° 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 6 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 6 hours, the film may be deteriorated by heating for a long time. When the heat treatment is finished, the inorganic porous support 10 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 21 is formed inside the pores 11a of the first layer 11 of the inorganic porous support after cooling. Here, the basis weight of the intermediate layer 21 is preferably adjusted to 1 to ²⁰ g / m ² . When the basis weight is less than 1 g / m ² , the intermediate layer 21 is insufficient and the separation layer 22 cannot be stabilized. If the basis weight exceeds 20 g / m ² , the intermediate layer 21 becomes excessive and the pores 11a may be blocked. In addition, 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 set as a set. An intermediate layer 21 having a denser and uniform film quality can be formed inside the pores 11a of the first layer 11.
Since the hydrocarbon group-containing polysiloxane network structure contained in the intermediate layer 21 contains hydrocarbon groups derived from the hydrocarbon group-containing trialkoxysilane, it has more flexibility than a general network structure. . Therefore, the intermediate layer 21 is improved in overall flexibility and flexibility while maintaining a certain degree of rigidity by the tetraalkoxysilane. When the flexibility of the intermediate layer 21 is improved, the film formability of the intermediate layer 21 is improved. Thereby, the crack and peeling of the intermediate layer 21 are prevented, and the amount of the raw material liquid of the separation layer 22 infiltrated into the inorganic porous support 10 is reduced. In addition, since the hydrocarbon group contained in the hydrocarbon group-containing polysiloxane network structure attracts the acidic gas, the intermediate layer 21 has a certain degree of separation performance of acidic gas as the separation layer 22.

(D) Second coating step As the second coating step, a second mixed liquid (a suspension of a refined polysiloxane network structure) is formed on the inorganic porous support 10 on which the intermediate layer 21 has been formed by the intermediate layer forming step. ) Is applied. Since the 2nd liquid mixture apply | coated at a 2nd application | coating process is apply | coated to the inorganic porous support body 10 via the intermediate | middle layer 21, the excessive penetration of the 2nd liquid mixture to the inorganic porous support body 10 is carried out. Can be suppressed. Therefore, the pores 11a of the first layer 11 of the inorganic porous support 10 are not clogged excessively, and the mixed gas passes through the separation membrane 100 for gas treatment containing acid gas completed by the separation layer forming step described later. In this case, it is possible to maintain the gas passage amount (mixed gas processing amount). Moreover, since the application amount of the forming material (sol) of the intermediate layer 21 and the separation layer 22 applied to the inorganic porous support 10 can be reduced, the production cost of the separation membrane 100 for acid gas-containing gas treatment can be reduced. Can also contribute. 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, a series of steps of immersing, pulling up, and drying the inorganic porous support 10 in the second mixed solution is repeated a plurality of times, thereby refining the polysiloxane that has been refined onto the inorganic porous support 10. The adhesion amount of the network structure can be increased. Moreover, since the second mixed liquid can be uniformly applied to the inorganic porous support 10 by repeating a series of procedures, the separation performance of the separation membrane 100 for gas treatment with acidic gas finally obtained is further improved. Can be improved.

(E) Separation layer forming step As the separation layer forming step, the inorganic porous support 10 that has completed the second coating step is heat-treated, and fine particles are formed inside the pores 11a of the first layer 11 of the inorganic porous support 10. The separated polysiloxane network structure is fixed or fused to form the separation layer 22 using the hydrocarbon group-containing polysiloxane network structure as a main material. The heat treatment method and conditions are the same as those in the intermediate layer forming step. The basis weight of the separation layer 22 is preferably adjusted to 0.2 to 1.5 g / m ² . When the basis weight is less than 0.2 g / m ² , the separation layer 22 is insufficient, so that sufficient gas separation performance cannot be obtained. When the basis weight exceeds 1.5 g / m ² , the gas permeability may be reduced. After the “separation layer forming step”, the process returns to the “second application step” described above, and when the second application step and the separation layer formation step are repeated as a set, the inorganic porous support 10 A denser and more uniform separation layer 22 can be formed in the pores 11a of the first layer 11.

  By carrying out the above steps (a) to (e), the intermediate gas layer 21 and the separation layer 22 are introduced into the pores 11 a of the first layer 11. Is completed. The hydrocarbon group-containing polysiloxane network structure contained in each of the intermediate layer 21 and the separation layer 22 was composed of the same family of materials except that the mixing ratio of the tetraalkoxysilane and the hydrocarbon group-containing trialkoxysilane was different. Therefore, they have a high affinity for each other. Therefore, no interfacial peeling or cracking occurs between the intermediate layer 21 and the separation layer 22, and both are firmly adhered to each other, and a stable separation membrane 100 for gas treatment containing acid gas can be configured.

  When a mixed gas containing an acidic gas such as carbon dioxide and methane gas is passed through the completed separation membrane 100 for treating an acidic gas-containing gas, the separation layer 22 is more hydrocarbon group-containing trialkoxysilane than the intermediate layer 21. Therefore, the acidic gas in the mixed gas is selectively attracted to the separation layer and passes through the separation membrane as it is. As a result, the methane gas component in the mixed gas is concentrated, and high-concentration 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. When the separation layer has a site that attracts methane gas (hydrocarbon group having an ethyl group or more carbon number), when a mixed gas containing carbon dioxide and methane gas is passed, the methane gas is selectively contained in the separation layer. Attracted, methane gas passes through the pores as they are. 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.

  As the inorganic porous support, an alumina ceramic tubular body (tubular structure) having a plurality of inorganic porous layers having different pore diameters was used (Test Examples 1 to 6 shown in Table 2 described later). Applying an alkoxide solution for forming an intermediate layer (first mixed solution) and an alkoxide solution for forming a separation layer to an alumina-based ceramic tubular body, and a hydrocarbon group-containing polysiloxane network structure in the pores of the first layer, which is the outermost layer Was introduced. The raw materials of the intermediate layer and the separation layer are tetraethoxysilane (Shin-Etsu Chemical LS-2430, manufactured by Shin-Etsu Chemical Co., Ltd.) as tetraalkoxysilane, and methyltriethoxysilane (Shin-Etsu Chemical Co., Ltd., Shin-Etsu Chemical) as a hydrocarbon group-containing trialkoxysilane. Silicone LS-1890), nitric acid (reagent special grade 69.5%, manufactured by Wako Pure Chemical Industries, Ltd.) as an acid catalyst, and ethanol (reagent special grade 99.5%, manufactured by Wako Pure Chemical Industries, Ltd.) were used as an organic solvent.

<Preparation of the first mixture>
A mixed solution of 0.007 g of nitric acid, 36.31 g of ethanol and 35.47 g of water was stirred for 30 minutes, and then 8.21 g of tetraethoxysilane was added and stirred for 2 hours, whereby an alkoxide solution for forming an intermediate layer (first A base solution of (mixed solution) was prepared. The pH of the base solution was 3.85. The molar concentration ratio of each component contained in the base solution is 0.003 for nitric acid, 20 for ethanol, and 50 for water, assuming that tetraethoxysilane is 1. Methyltriethoxysilane was added to 40 g of this base solution, and this was stirred for 2.5 hours to prepare an alkoxide solution for forming an intermediate layer (first mixed solution). The addition amount (content) of methyltriethoxysilane was set such that the ratio of methyltriethoxysilane in all alkoxysilanes contained in the first mixed solution was 0.5 to 60% by weight. Therefore, the blending ratio (A1 / B1) of tetraethoxysilane (A1) and methyltriethoxysilane (B1) is 40/60 to 99.5 / 0.5 by weight.

<Preparation of second mixed solution>
A mixed solution of 0.04 g of nitric acid, 63.16 g of ethanol and 2.47 g of water was stirred for 30 minutes, then 8.57 g of tetraethoxysilane was added and stirred for 1 hour, and then 4.89 g of methyltriethoxysilane was added. Then, 0.88 g of magnesium nitrate hexahydrate was added and the mixture was stirred for 2 hours to prepare an alkoxide solution for forming a separation layer (second mixed solution). The pH of the second mixed solution was 1.59. The molar concentration ratio of each component contained in the second liquid mixture is 0.01 for nitric acid, 20 for ethanol, 2 for water, 6 for magnesium nitrate, assuming that the total amount of tetraethoxysilane and methyltriethoxysilane is 1. Hydrate is 0.05. The proportion of methyltriethoxysilane in all alkoxysilanes contained in the second mixed solution was set to a constant 36% by weight. Therefore, the blending ratio (A2 / B2) of tetraethoxysilane (A2) and methyltriethoxysilane (B2) is 64/36 in weight ratio.

<Formation of intermediate layer and separation layer>
The first mixed liquid was applied to the surface of an alumina-based ceramic tubular body (effective length: 800 mm or 150 mm) by a dipping method. The lifting speed of the dipping method was 5 mm / s, and after the lifting, the film was dried at room temperature for 1 hour. After the application and drying of the first mixed solution was repeated twice, heat treatment was performed in a calciner. The heat treatment was performed by 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 three times to introduce an intermediate layer into the pores of the first layer of the tubular body. Next, the 2nd liquid mixture was apply | coated by the dipping method to the tubular body which introduce | transduced the intermediate | middle layer. The lifting speed of the dipping method was 1 mm / s, and after the lifting, the film was dried at room temperature for 1 hour. After the application and drying of the second mixed solution was repeated twice, heat treatment was performed in a calciner. The heat treatment was performed by 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 twice, and a separation layer was further introduced into the pores of the first layer of the tubular body. In the above layer formation step, the intermediate layer and the separation layer in the separation membrane of each test example had no problem in film formability.

<Analysis of separation membrane>
About the separation membrane formed by said process, the composition of the intermediate | middle layer and the separation layer was calculated | required with the nuclear magnetic resonance absorption measuring apparatus (NMR). In this example, structural analysis by ²⁹ Si NMR method was performed for each of the two intermediate layers formed in the tubular body and the single separated layer. And from the chart which plotted the chemical shift of T unit (trifunctional) and Q unit (tetrafunctional), the ratio (molar ratio) of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) contained in each layer Was calculated. The analysis results are shown in Table 1 below.

  In Table 1, the peak area of Q4 (Siloxane) in the Q unit is normalized as 1, and the peak areas of Q3 (Free silanols), Q2 (Geminal silanols), T3 (Traditional structure), and T2 (Bidental structure) are respectively shown. Calculated. The ratio of the total area of T units to the total area [(T2 + T3) / (T2 + T3 + Q2 + Q3 + Q4)] is the methyltriethoxysilane ratio (molar ratio), and the ratio of the total area of Q units to the total area [(Q2 + Q3 + Q4) / (T2 + T3 + Q2 + Q3 + Q4)] is the tetraethoxysilane ratio (molar ratio). According to Table 1, the ratio (measurement ratio) of tetraethoxysilane and methyltriethoxysilane determined by NMR was substantially the same as the preparation ratio. That is, it was confirmed that the compositions of the first mixed solution and the second mixed solution are reflected as they are in the compositions of the intermediate layer and the separation layer.

<Separation performance confirmation test>
Each separation membrane produced by the above procedure was subjected to a confirmation test regarding carbon dioxide separation performance. In this confirmation test, the gas permeation rate [P (N ₂ )] when nitrogen was permeated through the separation membrane and the gas permeation rate [P (CO ₂ )] when carbon dioxide was permeated through the same separation membrane were determined. 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 a mixed gas containing carbon dioxide by utilizing properties different depending on such gas and further appropriately setting the configuration of the membrane. In this confirmation test, the measurement of the gas permeation rate [P (CH ₃ )] when methane gas permeated through the separation membrane was not performed, but the gas molecule diameter of methane gas (3.8 cm) was the gas molecule of nitrogen. Since it is slightly larger than the diameter (3.64 mm), if it can be confirmed that carbon dioxide and nitrogen can be separated by the separation membrane of the present invention, it is estimated that carbon dioxide and methane gas can also be separated.

  FIG. 2 is a schematic configuration diagram of the gas permeation rate measuring apparatus 200 used in the separation performance confirmation test. The gas transmission rate measuring device 200 includes a gas cylinder 1, a pressure gauge 2, a chamber 3, and a mass flow meter 4. The separation membrane 100 is installed inside the chamber 3.

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 100, which is a tubular body, has one end (front end side) 100a sealed and the other end (base end side) 100b connected to the heat-resistant glass tube 5. The heat-resistant glass tube 5 was a Pyrex (registered trademark) tube (outer diameter 8 mm, inner diameter 6 mm, length 10 mm) manufactured by Corning. However, one end side of the heat-resistant glass tube 5 is reduced in diameter so that the outer diameter is 7 mm or less so that it can be inserted into the separation membrane 100 (inner diameter 7 mm). The connection point between the separation membrane 100 and the heat-resistant glass tube 5 is bonded with an adhesive (adhesive “Cemedine (registered trademark) C” manufactured by Cemedine Co., Ltd.), and further epoxy resin (two liquid manufactured by Nagase ChemteX Corporation). Adhesive epoxy adhesives “AV138” and “HV998”). When the chamber 3 is filled with carbon dioxide, the carbon dioxide permeates into the tube from the surface of the separation membrane 100 that is a tubular body, passes through the heat-resistant glass tube 5 and flows into the mass flow meter 4. 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 10 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 P (CO ₂ ) [m ³ / m ² · s (seconds) · Pa] of carbon dioxide was calculated. For nitrogen, the gas permeation rate P (N ₂ ) [m ³ / m ² · s (seconds) · Pa] was calculated in the same procedure as above. Then, the carbon dioxide separation performance was evaluated from the transmission rate ratio α (CO ₂ / N ₂ ), which is the ratio of the gas transmission rate P (CO ₂ ) of carbon dioxide and the gas transmission rate P (N ₂ ) of nitrogen. Table 2 below shows the structure of the support used in the separation membranes of Test Examples 1 to 6 (pore diameter and thickness, effective length of each layer) and the permeation rate and the permeation rate ratio of the separation membranes of Test Examples 1 to 6. Show.

The separation membranes of Test Examples 1 to 6 all had the ability to selectively separate carbon dioxide from a mixed gas of carbon dioxide and nitrogen. In particular, in the separation membranes of Test Examples 1 and 4 in which the pore diameter of the first layer is 120 nm, the gas permeation rate P (CO ₂ ) of carbon dioxide and the permeation rate ratio α (CO ₂ / N ₂ ) become very large. It showed very good gas separation performance and gas throughput. Also for the separation membranes of Test Examples 2 and 5 in which the pore size of the first layer is 150 nm, the gas permeation rate P (CO ₂ ) of carbon dioxide and the permeation rate ratio α (CO ₂ / N ₂ ) are sufficient. Excellent gas separation performance and gas throughput were exhibited. In the separation membranes of Test Examples 3 and 6 having a three-layer structure, the pore size of the first layer is set to be relatively small, and the pore sizes of the second layer and the third layer are set to be relatively large. Compared to the separation membrane, the gas permeation rate P (CO ₂ ) of carbon dioxide was slightly inferior, but still showed practical gas separation performance and gas throughput. In addition, according to an additional test by the present inventors, it was confirmed that the pore diameter of the first layer in the inorganic porous support can be expanded to 200 nm as a range in which the separation membrane exhibits significant gas separation performance and gas throughput. (Data omitted). In addition, regarding the effective length of the separation membrane, no clear tendency was observed in the comparison between the supports having the same pore diameter (Test Examples 1 and 4, Test Examples 2 and 5, Test Examples 3 and 6), and the separation performance In the range of the effective length of 150 to 800 mm in which the confirmation test was performed, it was confirmed that the carbon dioxide separation ability was above a certain level. In addition, according to the additional test by the present inventors, it has been confirmed that the lower limit of the effective length of the inorganic porous support of the separation membrane having a carbon dioxide separation ability of a certain level or more is 50 mm (data not shown). .

<Separation membrane property change confirmation test>
The separation membrane for treatment of acid gas-containing gas according to the present invention is completed by sequentially forming an intermediate layer and a separation layer on an inorganic porous support, but how the properties as a separation membrane are determined by the formation of each layer. It is very useful information to design a separation membrane for acid gas-containing gas treatment having a multilayer structure. Therefore, a test for confirming the change in the characteristics of the separation membrane was performed in the middle of the production of the separation membrane for treatment of acid gas-containing gas. FIG. 3 is a graph showing changes in each characteristic in the middle stage of production of the separation membrane for treatment of acid gas-containing gas. In this test, a three-layered intermediate layer was formed by coating the inorganic porous support three times with the first mixed solution described in the section “Method for producing separation membrane for gas treatment containing acid gas”, Two separated layers were formed by coating the second mixed solution twice. At this time, the specimen immediately after the formation of each layer was used as a specimen, and the characteristics of each specimen were measured stepwise. The measurement items are (a) carbon dioxide and nitrogen permeation rate, (b) carbon dioxide and nitrogen permeation rate ratio, (c) the amount of permeation of each liquid mixture into the separation membrane, and (d) the separation membrane. The basis weight of each layer was used.

  (A) As shown in FIG. 3 (a), the permeation rate of carbon dioxide and nitrogen decreased as the layer structure increased, but the nitrogen permeation rate decreased compared to the decrease in carbon dioxide permeation rate. The decrease in the permeation rate of the film became more remarkable. This tendency was confirmed not only when the separation layer was formed but also when the intermediate layer was formed. In a separation membrane having a conventional multilayer structure in which an intermediate layer and a separation layer are formed on an inorganic porous support, the decrease in the permeation rate of carbon dioxide and the decrease in the permeation rate of nitrogen during the formation of the intermediate layer are approximately the same. However, surprisingly, in the present invention, a clear difference was recognized from the formation stage of the intermediate layer. That is, it was confirmed that the separation membrane for gas treatment of an acid gas of the present invention has gas separation ability not only in the separation layer but also in the intermediate layer. (B) As shown in FIG. 3B, the transmission rate ratio between carbon dioxide and nitrogen increases as the layer structure increases. In particular, the second layer of the separation layer is formed. As a result, it was confirmed that the transmission speed ratio was greatly increased. (C) As shown in FIG. 3 (c), the amount of each mixed solution entering the separation membrane decreases as the layer structure increases. In particular, the first layer of the intermediate layer is formed. After that, it was confirmed that the penetration of the mixed liquid after that was greatly suppressed. (D) The basis weight of each layer relative to the separation membrane, as shown in FIG. 3D, it was confirmed that the basis weight of each subsequent layer can be greatly reduced after the formation of the first layer of the intermediate layer.

  The separation membrane for treatment of acid gas-containing gas of the present invention can be used in city gas production equipment, hydrogen supply equipment for fuel cells, factory exhaust gas purification equipment, liquefied carbon dioxide production equipment, and the like. It can also be used in CCS, which is being studied as a countermeasure against global warming.

DESCRIPTION OF SYMBOLS 1 Gas cylinder 2 Pressure gauge 3 Chamber 4 Mass flow meter 5 Heat-resistant glass tube 100 Separation membrane 200 Gas permeation rate measuring apparatus

Claims (8)

An acid gas-containing gas treatment separation membrane for separating an acid gas from an acid gas-containing gas,
A support having a plurality of inorganic porous layers having different pore diameters;
A hydrocarbon group-containing polysiloxane network having an affinity for the acid gas;
With
In the support, a first layer having a minimum pore diameter among the plurality of inorganic porous layers is disposed on the surface side, and the hydrocarbon group-containing polysiloxane network structure is formed in the pores of the first layer. Separation membrane for gas treatment with acid gas in which the body is introduced as an intermediate layer and a separation layer.   2. The separation membrane for acid gas-containing gas treatment according to claim 1, wherein in the support, the hydrocarbon group-containing polysiloxane network is not introduced into pores of layers other than the first layer.   The separation membrane for acid gas-containing gas treatment according to claim 1 or 2, wherein the hydrocarbon group-containing polysiloxane network structure is introduced inside the support from the opening position of the pores of the first layer. .   The said support body WHEREIN: The said hydrocarbon group containing polysiloxane network structure is comprised as a reaction material of hydrocarbon group containing trialkoxysilane and tetraalkoxysilane. Separation membrane for processing gas containing acid gas.   The said support body WHEREIN: The said hydrocarbon group containing polysiloxane network structure contains the metal salt which has affinity with the said acidic gas, The separation membrane for acidic gas containing gas treatment as described in any one of Claims 1-4 .   The separation membrane for acid gas-containing gas treatment according to any one of claims 1 to 5, wherein the pore diameter of the first layer is 120 to 200 nm.   The separation membrane for acid gas-containing gas treatment according to any one of claims 1 to 6, wherein a pore diameter of a layer located below the first layer is 1 to 1.7 µm.   The separation membrane for acid gas-containing gas treatment according to any one of claims 1 to 7, wherein the support has an effective length of 50 mm or more.

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