Method for producing carbon dioxide separation membrane and carbon dioxide separation membrane

Abstract

To provide: a method for producing a carbon dioxide separation membrane enabling efficient separation of carbon dioxide from a carbon dioxide mixed gas even in a high temperature environment; and the carbon dioxide separation membrane.SOLUTION: A method for producing a carbon dioxide separation membrane according to the present invention includes: a precursor preparation step of mixing an amine precursor which is an amine-based polymer having at least one of a primary amine group and a secondary amine group, and a silicone precursor which is a silicone-based polymer having an epoxy group to polymerize the epoxy group and the primary amine group or the secondary amine group through an epoxy ring-opening reaction to chemically bond the amine precursor and the silicone precursor to thereby generate an amine-silicone precursor; and a separation layer formation step of applying the amine-silicone precursor generated in the precursor preparation step to a porous support and firing the amine-silicone precursor to generate a separation membrane.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for producing a carbon dioxide separation membrane and a carbon dioxide separation membrane for separating carbon dioxide from a mixed gas containing carbon dioxide.

Background Art

[0002] In recent years, a technique for selectively separating carbon dioxide in a mixed gas using a separation membrane has been developed. This technique can be used to separate and recover carbon dioxide from off-gas from oil fields, exhaust gas from waste incineration or thermal power generation, natural gas, or a mixed gas obtained by gasifying coal.

[0003] When separating carbon dioxide from a mixed gas, for example, since the molecular sizes of nitrogen and carbon dioxide, which are contained in large amounts in the mixed gas, are close to each other, separation based on molecular size, that is, separation by a molecular sieve, is difficult. Therefore, a polymer membrane that utilizes the affinity for carbon dioxide is generally used for carbon dioxide separation.

[0004] As a separation membrane that utilizes the affinity for carbon dioxide, a separation membrane using an amine compound has been developed. For example, Patent Document 1 proposes a polymer membrane containing a polymer of a predetermined functional polymerizable monomer and an amine compound.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The mixed gas as described above is often at a high temperature. When a polymer separation membrane such as that in Patent Document 1 is used for separating a high-temperature mixed gas, since the energy of carbon dioxide is high at high temperatures, it is difficult to capture, and the affinity is difficult to manifest. Therefore, it is difficult to efficiently separate carbon dioxide in a high-temperature environment.

[0007] Also, for example, factory exhaust gas is at a high temperature of about 150°C, but generally conventional polymer separation membranes have poor heat resistance and are difficult to use in a high-temperature environment.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a carbon dioxide separation membrane and a carbon dioxide separation membrane that can efficiently separate carbon dioxide from a carbon dioxide mixed gas even in a high-temperature environment.

Means for Solving the Problems

[0009] To achieve the above object, a method for manufacturing a carbon dioxide separation membrane according to a first aspect of the present invention is mixing an amine precursor, which is an amine-based polymer having at least one of a primary amine group and a secondary amine group, and a silicone precursor, which is a silicone-based polymer having an epoxy group, and polymerizing the epoxy group with the primary amine group or the secondary amine group by an epoxy ring-opening reaction to chemically bond the amine precursor and the silicone precursor to generate an amine-silicone precursor in a precursor preparation step; including a separation layer formation step of applying the amine-silicone precursor generated in the precursor preparation step to a porous support and firing it to generate a separation membrane.

[0010] Also, the amine precursor may be selected from the group consisting of polyallylamine, polyethyleneimine, and polyvinylamine. This may also be the case.

[0011] Also, the silicone precursor Selected from the group consisting of epoxypropoxypropyl-terminated polydimethylsiloxane, polydiglycidoxypropylsiloxane, polymethylglycidoxypropylsiloxane, and silicone having a hybrid structure thereof may be the case.

[0012] Also, in the precursor preparation step, the amine precursor, the silicone precursor, and a solvent are mixed and stirred to generate an amine-silicone precursor, the solvent is selected from the group consisting of methanol, ethanol, propanol, aqueous methanol solution, aqueous ethanol solution, and aqueous propanol solution may be the case.

[0013] Also, the ratio of the amine precursor to the silicone precursor mixed in the precursor preparation step is such that the weight ratio obtained by dividing the weight of the amine precursor by the weight of the silicone precursor is 0.1 or more and 1.0 or less. may be the case.

[0014] Also, the porous support is a ceramic porous support made of alumina or a carbon porous body may be the case.

[0015] The carbon dioxide separation membrane according to the second aspect of the present invention comprises a porous support having a plurality of pores, and a separation layer formed on the support and composed of a polymer of a silicone-based polymer having an epoxy group and an amine-based polymer having at least one of a primary amine group and a secondary amine group, which is polymerized by an epoxy ring-opening reaction.

Advantages of the Invention

[0016] According to the present invention, carbon dioxide can be efficiently separated in a high temperature range.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

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Figure 5

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Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0018] Hereinafter, the separation membrane 10 which is a carbon dioxide separation membrane according to the present embodiment will be described. As shown in the conceptual diagram of FIG. 1, the separation membrane 10 according to the present embodiment includes a separation layer 11 and a support 12. In order to reduce the permeation resistance of the separation membrane and increase the permeability, the separation membrane 10 according to the present embodiment does not form an intermediate layer that can increase the permeation resistance, and the separation layer 11 is formed by directly coating the support 12 with a coating liquid that becomes the material of the separation layer 11.

[0019] (Support) The support 12 is a porous base material having a plurality of pores. In order to perform carbon dioxide separation for a high-temperature mixed gas, it is preferable to use a support with high heat resistance. Therefore, the support 12 is preferably an inorganic porous body.

[0020] Examples of the inorganic porous body that can be the support 12 include ceramics composed of metal oxides such as alumina (α-Al2O3, γ-Al2O3), silicon dioxide (SiO2), mullite (3Al2O3·2SiO2 to 2Al2O3·SiO2), titanium dioxide (TiO2), and zirconia, or composites thereof.

[0021] The support 12 according to the present embodiment is a ceramic porous support mainly composed of α-alumina, which is inexpensive, easily available, and excellent in heat resistance and strength.

[0022] The shape of the support 12 is not particularly limited, but a cylindrical shape or a plate shape is preferable. Also, if the pore diameter of the support 12 is too large, the coating liquid for forming the separation layer 11 will enter the pores of the support 12, resulting in defects in the separation layer 11. Therefore, it is preferable to select a support 12 with an appropriate pore diameter in consideration of the viscosity of the coating liquid. The average pore diameter of the support 12 according to the present embodiment is preferably about 1 nm to 200 nm. (Separation layer)

[0023] The separation layer 11 is formed of an amine-silicone polymer produced by chemical crosslinking of an amine-based polymer and a silicone-based polymer. Although the detailed separation characteristics of the separation layer 11 will be described later, the separation membrane 10 functions as a carbon dioxide permeable membrane due to the affinity based on the primary amine group or secondary amine group contained in the amine-based polymer.

[0024] The amine precursor of the amine-silicone polymer is an amine-based polymer containing at least one of a primary amine group and a secondary amine group. Also, the amine precursor may contain a tertiary amine. Specifically, the amine precursor is polyallylamine, polyethyleneimine, polyvinylamine, etc.

[0025] The silicone precursor of the amine-silicone polymer is a silicone-based polymer having an epoxy group. The silicone precursor may have an epoxy group at the terminal or in the side chain. Specifically, the silicone precursor is silicone having an epoxypropoxypropyl-terminated polydimethylsiloxane, polydiglycidoxypropylsiloxane, polymethylglycidoxypropylsiloxane, and a hybrid structure thereof.

[0026] (Method for manufacturing a separation membrane) Hereinafter, with reference to the flowchart of FIG. 2, a method for manufacturing the separation membrane 10 according to the present embodiment will be described. The method for manufacturing the separation membrane 10 according to the present embodiment includes a precursor preparation step of preparing an amine-silicone polymer using an amine precursor and a silicone precursor, and a separation layer forming step of applying and firing the amine-silicone polymer on the support 12 to form a separation layer 11.

[0027] First, as the precursor preparation step, an amine-silicone polymer that is a material for the separation layer 11 is prepared. In the present embodiment, polyallylamine (PAA) mainly composed of a primary amine is used as the amine precursor.

[0028] The silicone precursor has a function of supporting a network in a polymer of an amine-based polymer and a silicone-based polymer that are chemically crosslinked, and contributes to improving the mechanical strength and heat resistance of the separation layer 11. In the present embodiment, both a material having an epoxy group at the terminal of polydimethylsiloxane (PDMS) (PDMS-ET: PDMS-epoxy-terminated) and a material having an epoxy group in the side chain (PDMS-ES: PDMS-epoxy-side-chain) can be used as the silicone precursor.

[0029] PDMS-ET is, for example, epoxypropoxypropyl-terminated polydimethylsiloxane. PDMS-ES is formed, for example, by hydrolyzing and polycondensing the following GMDES ((3-Glycidoxypropyl)methyldiethoxysilane).

Chem.

[0030] A solvent is added to and mixed with the above amine precursor and silicone precursor (step S11). The solvent is a liquid that can dissolve both the amine precursor and the silicone precursor, and may be any substance that can be dried at a heat treatment temperature (170°C in this embodiment) described later. The solvent is, for example, alcohols, and methanol, ethanol, propanol, aqueous methanol solution, aqueous ethanol solution, aqueous propanol solution, etc. can be used. The amount of the solvent to be mixed is 50 to 80 mass percent of the total amount.

[0031] The above amine precursor, silicone precursor, and solvent are stirred in a water bath at room temperature to 100°C. In this embodiment, it is stirred in a 50°C water bath for 1 hour (step S12). As a result, an epoxy ring-opening reaction occurs, the amine group and the epoxy group are bonded, and an amine-silicone polymer is formed. Although the details of the mixing ratio of the amine precursor and the silicone precursor will be described later, it is generally 0.1 or more and 1.0 or less in terms of weight ratio (amine precursor / silicone precursor). By adjusting the mixing ratio, it becomes possible to control the separation characteristics of the separation membrane 10.

[0032] Subsequently, as the separation layer formation step, a separation layer 11 is formed on the support 12. The amine-silicone polymer prepared in the precursor preparation step is applied onto the support 12 at room temperature using a nonwoven fabric (Bencot (trade name), Asahi Kasei Corporation) (step S13), and dried in a room temperature atmosphere (step S14). Then, the applied amine-silicone polymer is heat-treated (baked) at 170°C for 1 hour in a nitrogen (N2) atmosphere (step S15). By drying in step S14 and heat crosslinking by heat treatment in step S15, the applied amine-silicone polymer is gelled (solidified) to form the separation layer 11. In this embodiment, the heat treatment temperature is 170°C, but it is not limited thereto, and it may be determined in consideration of the decomposition temperature of the amine of the amine precursor. For example, when polyethyleneimine is used as the amine precursor, it is considered that heat treatment may be performed at about 200°C. Through the above steps, the separation membrane 10 is formed.

[0033] As described above, by applying an amine-silicone polymer onto the support 12 to form the separation layer 11, a separation membrane 10 provided with a separation layer 11 of a hybrid polymer in which an amine-based polymer and a silicone-based polymer are polymerized can be manufactured. As shown in FIG. 3, a separation layer 11 of about 400 nm is formed on the support 12, and the separation membrane 10 is configured. Incidentally, the amine-silicone polymer constituting the separation layer 11 penetrates into the support 12 in a range of about 2.2 μm from the surface of the separation layer 11.

[0034] Since the formed separation layer 11 has a primary amine group or a secondary amine group, the separation membrane 10 functions as a carbon dioxide selective membrane. Further, since the amine-based polymer of the separation layer 11 is chemically bonded to the silicone-based polymer, the separation membrane 10 has high heat resistance and can separate carbon dioxide in a high temperature environment.

[0035] (Example 1) In this example, epoxypropoxypropyl-terminated polydimethylsiloxane (PDMS-ET) having an epoxy group at the terminal as a silicone precursor and polyallylamine as an amine precursor were used. The weight ratio of the amine precursor to the silicone precursor (hereinafter, the value Am / Si obtained by dividing the weight of the amine precursor by the weight of the silicone precursor is used as a value representing the weight ratio of the amine precursor to the silicone precursor) was changed as shown in the table of FIG. 4 to form the separation membrane 10. Then, the relationship between the molecular size and the permeability was measured for each formed separation membrane 10. The gas temperature for the measurement was 150°C.

[0036] The structure of the polymerized hybrid polymer is as follows.

Chemical formula

[0037] Due to the different forms of amine groups in the separation layer 11 and the different densities of the polymer matrix structures, as shown in FIG. 4, the permeabilities of each molecule are different. More specifically, as the weight ratio of the amine precursor to the silicone precursor, Am / Si, increases, the structure becomes denser. Regarding carbon dioxide, the separation membrane 10 with Am / Si = 0.33 showed a higher permeability than the separation membrane 10 with Am / Si = 1 in terms of the weight ratio of the amine precursor to the silicone precursor. When separating carbon dioxide from a mixed gas, the weight ratio of the amine precursor to the silicone precursor may be determined based on the selectivity and permeability of carbon dioxide in consideration of the components contained in the mixed gas.

[0038] In addition, when Am / Si = 3 in this example, the amine-silicone polymer did not solidify sufficiently and remained in a liquid state. If the solidification of the amine-silicone polymer constituting the separation layer 11 is insufficient, when pressure is applied to the separation layer 11 by the mixed gas, the amine-silicone polymer may escape into the pores of the support 12 and may not function as the separation membrane 10. Therefore, it is considered that the weight ratio of the amine precursor to the silicone precursor in this example is preferably Am / Si = 1.0 or less.

[0039] (Example 2) In this example, polymethylglycidoxypropylsiloxane, which is PDMS-ES having an epoxy group in the side chain as a silicone precursor, was used, and polyallylamine was used as an amine precursor. The separation membrane 10 was formed by changing the weight ratio of the amine precursor and the silicone precursor as shown in the table of FIG. 5. Then, the relationship between the molecular size and the transmittance was measured for each formed separation membrane 10. The gas temperature for the measurement was set at 150°C.

[0040] The structure of the polymerized hybrid polymer is as follows. [Chemical formula]

[0041] Due to the different forms of amine groups in the separation layer 11 and the different densities of the polymer matrix structure, as shown in FIG. 5, the transmittance of each molecule is different. Regarding carbon dioxide, a high transmittance was shown when Am / Si = 0.1. When separating carbon dioxide from a mixed gas, the weight ratio of the amine precursor and the silicone precursor may be determined based on the selectivity and transmittance of carbon dioxide in consideration of the components contained in the mixed gas.

[0042] As shown in FIG. 6, even when the weight ratio of the amine precursor and the silicone precursor is the same between the terminal crosslinked type and the side chain crosslinked type, the ease of molecular permeation is different. As in the measurement results (FIG. 7) of Example 1 and Example 2 described above, in the separation membrane 10 according to the present invention, the separation characteristics of carbon dioxide can be adjusted by the mixing ratio of the amine precursor having an amine group and the silicone precursor having an epoxy group, and the difference in the crosslinked structure.

[0043] FIG. 8 is a diagram showing the separation performance of a conventional separation membrane and the separation membranes according to Examples 1 and 2. FIG. 8(A) is a diagram showing the separation performance at 130° C. or lower, and FIG. 8(B) is a diagram showing the separation performance at 150° C. or higher. The symbols in FIGS. 8(A) and (B) represent the types of materials of the separation membranes, where PDMS represents Polydimethylsiloxane, PVA represents Polyvinyl alcohol, PI represents Polyimide, PBI represents Polybenzimidazole, PIM represents Polymers of Intrinsic Microporosity, and CMS represents Carbon Molecular Sieve.

[0044] In the graph of FIG. 8(B), the data of the separation membranes according to Examples 1 and 2 above are plotted in the upper right region, indicating that high permeability and high selectivity can be achieved simultaneously. Therefore, by using the separation membrane 10 according to this embodiment, carbon dioxide can be efficiently separated in a high temperature region.

[0045] As described above, the separation membrane 10 according to this embodiment chemically bonds an amine-based polymer, which has a high affinity for carbon dioxide but poor heat resistance, to a silicone-based polymer with high heat resistance, thereby realizing carbon dioxide separation at high temperatures.

[0046] In the above embodiment, no intermediate layer is formed, but this is not restrictive. For example, when higher mechanical strength is required, an intermediate layer may be formed.

[0047] Also, in the above embodiment, the alumina support 12 is used, but this is not restrictive. FIG. 9 is a cross-sectional photograph of a separation membrane 10 formed by forming a separation layer 11 similar to that in the above embodiment using a carbon support. As shown in FIG. 9, a separation layer 11 of about 400 nm is formed on the support 12 to constitute the separation membrane 10. The amine-silicone polymer constituting the separation layer 11 penetrates into the support 12 in a range of about 1 μm from the surface of the separation layer 11.

[0048] FIG. 10 is a diagram showing the measurement results of the separation performance of the separation membrane 10 at 150° C. using the support 12 which is a carbon porous body. The carbon support of this example has a diameter of 0.2 to 0.4 mm, a bulk specific gravity of about 1.0 g / cm3, a pore diameter of 0.2 μm, a pressure resistance of 20 MPa or more, and a bending radius of about 10 mm. The separation layer 11 was formed by wetting one side of a nonwoven fabric with an amine-silicone polymer similar to that in the above embodiment, applying it while sandwiching the carbon support on the wet surface, and then performing a heat treatment. As shown in FIG. 10, it can be seen that even when using a carbon support, the separation performance of carbon dioxide can be exhibited in a high-temperature environment.

Industrial Applicability

[0049] The present invention is suitable for the separation of carbon dioxide, and is particularly suitable for a separation membrane that separates carbon dioxide from a high-temperature mixed gas such as industrial exhaust gas.

Explanation of Signs

[0050] 10 Separation membrane, 11 Separation layer, 12 Support

Claims

1. A precursor preparation step of mixing an amine precursor, which is an amine-based polymer having at least one of a primary amine group and a secondary amine group, and a silicone precursor, which is a silicone-based polymer having an epoxy group, and polymerizing the epoxy group with the primary amine group or the secondary amine group by an epoxy ring-opening reaction to chemically bond the amine precursor and the silicone precursor to produce an amine-silicone precursor; A separation layer forming step of applying the amine-silicone precursor produced in the precursor preparation step to a porous support and firing it to produce a separation layer, A method for producing a carbon dioxide separation membrane, characterized by comprising the above steps.

2. The amine precursor is selected from the group consisting of polyallylamine, polyethyleneimine, and polyvinylamine, The method for producing a carbon dioxide separation membrane according to claim 1, characterized by the above.

3. The silicone precursor is selected from the group consisting of epoxypropoxypropyl-terminated polydimethylsiloxane, polydiglycidoxypropylsiloxane, polymethylglycidoxypropylsiloxane, and silicones having a hybrid structure thereof, The method for producing a carbon dioxide separation membrane according to claim 1, characterized by the above.

4. In the precursor preparation step, the amine precursor, the silicone precursor, and a solvent are mixed and stirred to produce an amine-silicone precursor, The solvent is selected from the group consisting of methanol, ethanol, propanol, aqueous methanol solution, aqueous ethanol solution, and aqueous propanol solution, The method for producing a carbon dioxide separation membrane according to claim 1, characterized by the above.

5. The ratio of the amine precursor and the silicone precursor mixed in the precursor preparation step is such that the weight ratio obtained by dividing the weight of the amine precursor by the weight of the silicone precursor is 0.1 or more and 1.0 or less, The method for producing a carbon dioxide separation membrane according to claim 1, characterized by the above.

6. The porous support is a ceramic porous support made of alumina or a carbon porous body, The method for producing a carbon dioxide separation membrane according to claim 1, characterized by the above.

7. A support that is a porous body having a plurality of pores, A separation layer comprising a polymer of a silicone-based polymer having an epoxy group, which is formed on the support and polymerized by an epoxy ring-opening reaction, and an amine-based polymer having at least one of a primary amine group and a secondary amine group. A carbon dioxide separation membrane characterized by the above.

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