Gas separation membrane, method for manufacturing a gas separation membrane, and gas separation apparatus

Abstract

To provide a gas separation membrane and a method for manufacturing the same, which have a high gas selectivity and high gas permeability for carbon dioxide contained in the atmosphere and industrial exhaust gases, and which also have sufficient mechanical strength, as well as a gas separation apparatus with excellent carbon dioxide separation performance. [Solution] A gas separation membrane comprising a separation layer having the function of selectively separating carbon dioxide, and a support layer located on the opposite side from the space to which the mixed gas is supplied, and containing an organopolysiloxane, wherein when the thickness of the separation layer is tA [nm] and the thickness of the support layer is tB [nm], the separation layer and the support layer satisfy equations (1) and (2), and when an XPS spectrum is obtained for the separation layer by X-ray photoelectron spectroscopy and the C1s peak is waveform-separated, the intensity ratio I(CN) / I(CC) satisfies equation (3). 1 <tA+tB<1000 (1) 0.01 <tA / tB<0.20 (2) 0.03

Description

[Technical Field]

[0001] This invention relates to a gas separation membrane, a method for manufacturing a gas separation membrane, and a gas separation apparatus. [Background technology]

[0002] To achieve carbon neutrality and carbon negative emissions, technologies are being considered to capture and recover carbon dioxide emitted from thermal power plants and boiler facilities, as well as carbon dioxide from the atmosphere. One such technology is membrane separation, which uses gas separation membranes to separate carbon dioxide.

[0003] For example, Patent Document 1 discloses a gas separation membrane comprising a support membrane having at least a porous support layer, and a crosslinked polyamide separation functional layer provided on the support membrane, wherein the separation membrane contains a substance having affinity for carbon dioxide, and the content of the affinity substance is 10% to 70% by weight relative to 100% by weight of the total weight of the separation membrane. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-042719 [Overview of the project] [Problems that the invention aims to solve]

[0005] The gas separation membrane described in Patent Document 1 is a separation membrane for concentrating and recovering carbon dioxide from a mixed gas containing carbon dioxide at a high concentration, for example, about 50 mol%, and the supply pressure of the mixed gas is also high at 3 atmospheres. For this reason, when the carbon dioxide concentration or pressure of the supplied mixed gas is low, specifically when concentrating carbon dioxide contained in atmospheric carbon dioxide or industrial exhaust gas, the separation performance of the gas separation membrane cannot be fully utilized.

[0006] Therefore, even in such cases, the challenge lies in realizing a gas separation membrane that has a high gas selectivity and high gas permeability for carbon dioxide, as well as excellent mechanical strength. [Means for solving the problem]

[0007] The gas separation membrane according to an application example of the present invention is A gas separation membrane having the function of separating carbon dioxide from a mixed gas supplied at a supply pressure of 0.5 atmospheres or more and 2.0 atmospheres or less, wherein the carbon dioxide concentration is greater than 0 volume% and 10 volume% or less. A separation layer is provided on the side of the space to which the mixed gas is supplied, and contains a polymer having CN bonds and CC bonds, and has the function of selectively separating carbon dioxide. A support layer containing an organopolysiloxane is located on the opposite side from the space to which the mixed gas is supplied, Equipped with, When the thickness of the separation layer is tA [nm] and the thickness of the support layer is tB [nm], The separation layer and the support layer satisfy the following equations (1) and (2): When the XPS spectrum was obtained from the aforementioned separation layer by X-ray photoelectron spectroscopy and the C1s peak was waveform-separated, The intensity ratio I(CN) / I(CC) of the peak intensity I(CC) derived from the CN bond to the peak intensity I(CN) derived from the CC bond satisfies the following equation (3). 1 <tA+tB<1000 (1) 0.01 <tA / tB<0.20 (2) 0.03 <I(C-N) / I(C-C)<0.50 (3)

[0008] The method for producing a gas separation membrane according to an application example of the present invention is: A method for producing a gas separation membrane according to an application example of the present invention, A step of contacting one side of a film containing organopolysiloxane with a solution containing an amine, A step of applying energy to the film that has been brought into contact with the aforementioned solution, It holds.

[0009] The gas separation device according to the application example of the present invention is a gas separation membrane according to the application example of the present invention, a fixing part that fixes the gas separation membrane and has an internal space formed on the support layer side of the gas separation membrane, and an exhaust part that decompresses the internal space so as to create a negative pressure in the external space on the separation layer side of the gas separation membrane. It is provided with.

Brief Description of Drawings

[0010] [Figure 1] It is a cross-sectional view schematically showing the gas separation membrane according to the embodiment. [Figure 2] It is a process diagram showing the configuration of the manufacturing method of the gas separation membrane according to the embodiment. [Figure 3] It is a cross-sectional view schematically showing the schematic configuration of the gas separation device according to the embodiment. [Figure 4] It is Table 1 showing the configuration of the gas separation membranes of each example and each comparative example and the evaluation results of the gas separation membranes. [Figure 5] It is an example of the XPS spectrum (C1s) in the vicinity of the C1s peak.

Modes for Carrying Out the Invention

[0011] Hereinafter, the gas separation membrane, the manufacturing method of the gas separation membrane, and the gas separation device according to the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

[0012] 1. Outline of Gas Separation Membrane First, the configuration of the gas separation membrane according to the embodiment will be described.

[0013] FIG. 1 is a cross-sectional view schematically showing the gas separation membrane 1 according to the embodiment. In FIG. 1 of the present application, the X-axis, the Y-axis, and the Z-axis are set as three axes orthogonal to each other and are indicated by arrows respectively. And the base end side of the arrow indicating each axis is "minus" and the tip side is "plus".

[0014] In the gas separation membrane 1 shown in Figure 1, the positive Z-axis side is defined as "up" and the negative Z-axis side as "down". A mixed gas is supplied to the top of the gas separation membrane 1. In the gas separation membrane 1 shown in Figure 1, carbon dioxide is separated by permeation from top to bottom.

[0015] The gas separation membrane 1 shown in Figure 1 has the function of separating carbon dioxide by permeation from a mixed gas supplied at a supply pressure of 0.5 atmospheres to 2.0 atmospheres, where the carbon dioxide concentration is greater than 0 volume% and 10 volume% or less. Technology for separating carbon dioxide from a mixed gas supplied at such a relatively low carbon dioxide concentration and a pressure relatively close to atmospheric pressure is considered to be in particularly high demand when achieving carbon neutrality or carbon minus. For example, the atmosphere and industrial exhaust gases are typical examples of the above mixed gases. The gas separation membrane 1 according to this embodiment makes it possible to efficiently separate carbon dioxide from such mixed gases.

[0016] The gas separation membrane 1 shown in Figure 1 comprises a sheet-like support layer 3 extending along the XY plane and a separation layer 4 provided on one side of the support layer 3.

[0017] The separation layer 4 is positioned on the supply side of the mixed gas. The separation layer 4 contains a polymer having CN and CC bonds and has the function of preferentially permeating carbon dioxide.

[0018] Support layer 3 is positioned on the opposite side from the supply side of the mixed gas. Support layer 3 contains organopolysiloxane.

[0019] Here, let the thickness of the separation layer 4 be tA [nm] and the thickness of the support layer 3 be tB [nm]. In this case, the separation layer 4 and the support layer 3 satisfy the following equations (1) and (2). 1 <tA+tB<1000 (1) 0.01 <tA / tB<0.20 (2)

[0020] Furthermore, when an XPS spectrum is obtained for the separation layer 4 by X-ray photoelectron spectroscopy, and the C1s peak included in the XPS spectrum is waveform-separated, the intensity ratio I(CN) / I(CC) of the peak intensity I(CC) originating from the CN bond to the peak intensity I(CN) originating from the CC bond satisfies the following equation (3). 0.03 <I(C-N) / I(C-C)<0.50 (3)

[0021] With this configuration, a gas separation membrane 1 can be realized that has a high gas selectivity and high gas permeability for carbon dioxide contained in the atmosphere and industrial exhaust gases, and also has sufficient mechanical strength.

[0022] The gas separation membrane according to the present invention may take the form of a sheet (flat plate) as shown in Figure 1, or it may be spiral, tubular, hollow fiber, or the like.

[0023] 1.1.Support layer The support layer 3 is in the form of a sheet and supports the separation layer 4. As a result, even if the separation layer 4 does not have sufficient mechanical properties, the support layer 3 supports the separation layer 4, making it possible to realize a gas separation membrane 1 with sufficient mechanical properties.

[0024] Support layer 3 contains organopolysiloxane. Organopolysiloxane consists of monofunctional M units with three organic substituents attached to a silicon atom, difunctional D units with two substituents, and trifunctional T units with one substituent, all of which are combined to form the support layer. In other words, organopolysiloxane contains very few tetrafunctional Q units without organic substituents. As a result, organopolysiloxane has relatively long interatomic distances between its Si-O and Si-C bonds, resulting in a large free volume. This allows for good diffusion of carbon dioxide molecules and good gas permeability to carbon dioxide. Therefore, support layer 3 containing organopolysiloxane mechanically supports the separation layer 4 without significantly hindering its gas permeability, thus maximizing the gas selectivity of the separation layer 4.

[0025] The constituent material of the support layer 3 may include other materials as long as organopolysiloxane is the main component (more than 50% by mass). Examples of other materials include polymer materials other than organopolysiloxane, ceramic materials, and metallic materials.

[0026] On the other hand, the content of organopolysiloxane in the constituent material of the support layer 3 is preferably 70% by mass or more, and more preferably 90% by mass or more.

[0027] Specific examples of organopolysiloxanes include polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, polysulfone / polyhydroxystyrene / polydimethylsiloxane copolymer, dimethylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / diphenylsiloxane / methylvinylsiloxane copolymer, methyl-3,3,3-trifluoropropylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / methylphenylsiloxane / methylvinylsiloxane copolymer, diphenylsiloxane / dimethylsiloxane copolymer with vinyl terminus, polydimethylsiloxane with vinyl terminus, polydimethylsiloxane with H terminus, and dimethylsiloxane-methylhydrosiloxane copolymer. These also include forms in which crosslinked reaction products are formed. Furthermore, the constituent materials of the support layer 3 may be a composite of one or more of these materials, or a composite material in which organopolysiloxane is the main component (more than 50% by mass) and other resin components are used in combination.

[0028] Of these, the organopolysiloxane contained in the support layer 3 is preferably polydimethylsiloxane. Since polydimethylsiloxane contains more Si-C bonds and is chemically stable, a support layer 3 with better carbon dioxide gas permeability and superior stability can be obtained.

[0029] The thickness tB of the support layer 3 is preferably 30 nm to 950 nm, more preferably 50 nm to 500 nm, and even more preferably 100 nm to 300 nm. This ensures that the support layer 3 has the necessary and sufficient mechanical properties to serve as the base layer of the gas separation membrane 1.

[0030] The thickness tB of the support layer 3 is measured, for example, by depth profiling using X-ray photoelectron spectroscopy, which involves irradiating the back side of the support layer 3 (the side opposite to the side in contact with the separation layer 4) with X-rays. Depth profiling using X-ray photoelectron spectroscopy can be performed using ion beam sputtering and elemental analysis by X-ray photoelectron spectroscopy. The average value of the thicknesses measured at 10 locations on the support layer 3 is then defined as the thickness tB of the support layer 3.

[0031] Furthermore, the gas permeability of carbon dioxide through the support layer 3 is preferably set higher than that of the carbon dioxide gas permeability through the separation layer 4. This allows the support layer 3 to mechanically support the separation layer 4 while providing good gas permeability to the gas separation membrane 1.

[0032] The gas permeability of carbon dioxide through support layer 3 is 1 × 10⁻⁶. -5 cm 3 (STP) / cm 2 It is preferable that the sec·cmHg (10 GPUs) be 10 or more, more preferably 30 GPUs or more, even more preferably 100 GPUs or more, and particularly preferably 200 GPUs or more.

[0033] The support layer 3 can be manufactured by methods for manufacturing sheets or films. It can also be manufactured by a method in which the support layer is formed on a sacrificial layer and then the sacrificial layer is removed.

[0034] Furthermore, the support layer 3 may be a porous layer. This results in a support layer 3 with particularly good gas permeability to carbon dioxide.

[0035] The porous layer has pores, and its average inner diameter is called the "average pore diameter." The average pore diameter of the support layer 3 is preferably 0.2 μm or less, more preferably 0.01 μm to 0.15 μm, even more preferably 0.01 μm to 0.09 μm, and particularly preferably 0.01 μm to 0.07 μm. This ensures sufficient gas permeability of carbon dioxide through the support layer 3 while suppressing the separation layer 4 from escaping to the downstream side of the support layer 3. If the average pore diameter of the porous layer falls below the lower limit, the gas permeability of carbon dioxide through the support layer 3 may decrease. On the other hand, if the average pore diameter of the porous layer exceeds the upper limit, the separation layer 4 may escaping to the downstream side of the support layer 3.

[0036] The average pore size of the porous layer is measured using a through-pore diameter evaluation device after removing the separation layer 4 from the gas separation membrane 1 and extracting the support layer 3 on its own. An example of a through-pore diameter evaluation device is a palm porometer manufactured by PMI.

[0037] The porosity of the porous layer is preferably between 20% and 90%, and more preferably between 30% and 80%. This allows the porous layer to achieve both good gas permeability and sufficient rigidity.

[0038] The porosity of the porous layer is measured using the aforementioned through-pore diameter evaluation device after removing the separation layer 4 from the gas separation membrane 1.

[0039] Furthermore, the support layer 3 may be a composite material of the above-mentioned polymer material and fibers. The fibers may be used in the form of fibrous pieces such as chopped strands, but preferably they are used in the form of fabrics such as woven fabrics, nonwoven fabrics, or mesh fabrics. This further enhances the mechanical properties of the support layer 3.

[0040] 1.2. Separation layer The separation layer 4 is provided on the upper surface 31 (one side) of the support layer 3. The separation layer 4 has gas selectivity for carbon dioxide relative to nitrogen.

[0041] The separation layer 4 may be a layer formed on the upper surface 31 of the support layer 3. Alternatively, one side of a single film may be modified so that the modified portion becomes the separation layer 4 and the remaining portion becomes the support layer 3.

[0042] The constituent material of separation layer 4 includes polymers having CN bonds and CC bonds. Of these, the CN bonds are attached to functional groups that exhibit high affinity for carbon dioxide, such as amino groups and nitro groups. Therefore, polymers having CN bonds contribute to the realization of separation layer 4, which has the function of selectively separating carbon dioxide.

[0043] The constituent material of the separation layer 4 may be, for example, a polymer whose molecular structure itself has CN bonds and CC bonds, or a material obtained by subsequently adding (modifying) at least one of the CN bonds and CC bonds to an organopolysiloxane that serves as a base polymer (polymer). Of these, it is preferable that the constituent material of the separation layer 4 is a modified organopolysiloxane. By modifying the organopolysiloxane, a gas separation membrane 1 is obtained in which the support layer 3 and the separation layer 4 are integrated. Such a gas separation membrane 1 has particularly good mechanical strength because delamination at the interface is less likely to occur. Furthermore, by selecting an organopolysiloxane with high gas permeability to carbon dioxide and modifying it, a gas separation membrane 1 that achieves a high degree of balance between gas permeability and gas selectivity can be realized.

[0044] Examples of polymers whose molecular structure itself contains CN and CC bonds include polyimides and epoxy resins. In the case of epoxy resins, CN bonds can be introduced into the molecular structure by selecting a curing agent.

[0045] On the other hand, as mentioned above, the organopolysiloxane, which serves as the base polymer, contains M units, D units, and T units as basic structural units, and has good gas permeability to carbon dioxide. Therefore, the separation layer 4 can be manufactured by modifying a monolayer containing the organopolysiloxane raw material by introducing CN and CC bonds into a portion of its thickness. In other words, the separation layer 4 may be a resin layer formed by modifying a portion of a monolayer containing polydimethylsiloxane. With such a configuration, a gas separation membrane 1 can be realized in which a separation layer 4 with high gas selectivity for carbon dioxide, formed by modification, and a support layer 3, which is an unmodified portion with high gas permeability to carbon dioxide, are integrated.

[0046] Furthermore, organopolysiloxanes are polymers that contain many chemical bonds such as Si-O bonds, Si-C bonds, and CH bonds. When a portion of a monolayer containing organopolysiloxane is modified as described above, some of these chemical bonds can be cleaved first, and then another structure can be introduced at the bonding sites formed by the cleavage. In this way, structures containing CN bonds and CC bonds can be introduced. This results in a support layer 3 containing organopolysiloxane and a separation layer 4 in which CN bonds and CC bonds have been introduced into the organopolysiloxane.

[0047] The thickness tA [nm] of the separation layer 4 satisfies the relationship between the thickness tB [nm] of the support layer 3 and the following equations (1) and (2). 1 <tA+tB<1000 (1) 0.01 <tA / tB<0.20 (2)

[0048] Equation (1) above specifies that the sum of the layer thickness tA [nm] of the separation layer 4 and the layer thickness tB [nm] of the support layer 3, tA + tB, is greater than 1 nm and less than 1000 nm. Furthermore, the sum of the layer thicknesses tA + tB is preferably between 10 nm and 500 nm, and more preferably between 50 nm and 300 nm. By satisfying this relationship, a gas separation membrane 1 with high gas permeability of carbon dioxide and sufficient mechanical strength can be realized. Note that if the sum of the layer thicknesses tA + tB falls below the lower limit, the mechanical strength of the gas separation membrane 1 decreases. On the other hand, if the sum of the layer thicknesses tA + tB exceeds the upper limit, the gas permeability of carbon dioxide in the gas separation membrane 1 decreases.

[0049] Equation (2) above specifies that the ratio tA / tB of the thickness of the separation layer 4 to the thickness tB [nm] of the support layer 3 is greater than 0.01 and less than 0.20. Furthermore, the ratio tA / tB of the layer thicknesses is preferably 0.03 or more and 0.18 or less, and more preferably 0.05 or more and 0.16 or less. By satisfying this relationship, a gas separation membrane 1 with a high gas selectivity for carbon dioxide and sufficient mechanical strength can be realized. Note that if the ratio tA / tB of the layer thicknesses falls below the lower limit, the gas selectivity for carbon dioxide in the gas separation membrane 1 decreases. On the other hand, if the ratio tA / tB of the layer thicknesses exceeds the upper limit, the gas permeability of carbon dioxide in the gas separation membrane 1 decreases.

[0050] The thickness tA of the separation layer 4 is measured, for example, by depth profiling using X-ray photoelectron spectroscopy, in which X-rays are irradiated from the surface side of the separation layer 4 (the side opposite to the side in contact with the support layer 3). Depth profiling using X-ray photoelectron spectroscopy can be performed using ion beam sputtering and elemental analysis by X-ray photoelectron spectroscopy. The average value of the thicknesses measured at 10 locations on the separation layer 4 is then defined as the thickness tA of the separation layer 4.

[0051] Furthermore, the gas separation membrane 1 is subjected to X-ray photoelectron spectroscopy (XPS) by irradiating it with X-rays from the surface side of the separation layer 4. For X-ray photoelectron spectroscopy, for example, the PHI X-tool X-ray photoelectron spectroscopy analyzer manufactured by ULVAC-PHI is used. The X-ray irradiation conditions are a beam diameter of 11 μm, an incident angle of 45°, an AlKα source, an accelerating voltage of 15 kV, and an output of 25 W. The analysis conditions are a pass energy of 55 eV. The analysis software used is MultiPak manufactured by ULVAC-PHI. Waveform separation processing of the XPS spectrum by the analysis software is performed as follows.

[0052] First, the acquired XPS spectrum is imported into the analysis software, and the peak positions are corrected. Next, the C1s peak located at 282-290 eV is subjected to waveform separation using a Gaussian function as the fitting function. Waveform separation separates the CC peak, CN peak, and CO peak as the main peaks. The intensity of the separated CC peak is recorded as "Peak Intensity I(CC)". The CC peak is usually located around 285.0 eV. The intensity of the separated CN peak is also recorded as "Peak Intensity I(CN)". The CN peak is usually located around 285.5-286.0 eV. Next, the ratio of Peak Intensity I(CN) to Peak Intensity I(CC) is calculated as "Intensity Ratio I(CN) / I(CC)".

[0053] In separation layer 4, this intensity ratio I(CN) / I(CC) satisfies the relationship expressed by the following equation (3). 0.03 <I(C-N) / I(C-C)<0.50 (3)

[0054] Equation (3) above specifies that the ratio of peak intensity I(CN) to peak intensity I(CC), I(CN) / I(CC), is greater than 0.03 and less than 0.50. Furthermore, the intensity ratio I(CN) / I(CC) is preferably 0.05 or more and 0.30 or less, and more preferably 0.07 or more and 0.20 or less. By satisfying this relationship, the amount of CN bonds can be optimized in relation to the amount of CC bonds, resulting in a good balance between affinity for carbon dioxide and carbon dioxide desorption in the separation layer 4. This increases the gas selectivity of carbon dioxide in the gas separation membrane 1. Note that if the intensity ratio I(CN) / I(CC) falls below the lower limit, the affinity for carbon dioxide in the separation layer 4 decreases, and therefore the gas selectivity of carbon dioxide in the gas separation membrane 1 decreases. On the other hand, if the intensity ratio I(CN) / I(CC) exceeds the upper limit, the carbon dioxide desorption in the separation layer 4 decreases, and therefore the gas selectivity of carbon dioxide in the gas separation membrane 1 decreases.

[0055] 1.3. Other Configurations The gas separation membrane 1 according to the embodiment has been described above, but any layer may be provided downstream of the support layer 3. For example, a porous plate with higher rigidity than the support layer 3 may be provided downstream of the support layer 3. The porous plate has a large number of through holes formed in it so that the pressure loss of the gas passing through it is smaller than that of the support layer 3. This allows the gas separation membrane 1 to be supported without hindering the gas selective function of carbon dioxide in the gas separation membrane 1.

[0056] Examples of materials that can be used to construct a perforated plate include ceramic materials, metallic materials, and polymer materials. Furthermore, the perforated plate may be a composite material of these materials with other materials.

[0057] Examples of ceramic materials include alumina, cordierite, mullite, silicon carbide, and zirconia. Examples of metallic materials include stainless steel.

[0058] Examples of the polymer material include polyolefin resins such as polyethylene and polypropylene, fluorine-containing resins such as polytetrafluoroethylene, polyvinyl fluoride, and polyvinylidene fluoride, polystyrene, cellulose acetate, polyurethane, polyacrylonitrile, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, polyaramid, and the like.

[0059] 1.4. Characteristics of the gas separation membrane The carbon dioxide gas permeability R of the gas separation membrane 1 CO2 is preferably 200×10 -6 cm 3 (STP) / cm 2 ·sec·cmHg or more (200 GPU or more), and more preferably 250 GPU or more. Thereby, the gas separation membrane 1 with high carbon dioxide separation efficiency can be obtained. In addition, it is possible to reduce the input amount of energy required for separation, specifically, to realize the gas separation membrane 1 that can reduce the pressure difference between the upstream side and the downstream side of the gas separation membrane 1. The carbon dioxide gas permeability R CO2 is measured by the method described later.

[0060] Also, the carbon dioxide gas permeability of the support layer 3 is preferably 1,000 GPU or more and 100,000 GPU or less. Within this range, it is possible to suppress the inhibition of the carbon dioxide gas selection function in the separation layer 4. Also, within this range, the ease of manufacturing the support layer 3 can be relatively enhanced.

[0061] Let the nitrogen gas permeability of the gas separation membrane 1 be R N2 and the carbon dioxide gas permeability be R CO2 . At this time, the gas selectivity ratio R CO2 / R N2 of the gas separation membrane 1 is preferably 20 or more, more preferably 50 or more, and even more preferably 100 or more. When the gas selectivity ratio R CO2 / R N2 is within the above range, the gas separation membrane 1 can efficiently separate and recover carbon dioxide in the mixed gas. On the other hand, when the gas selectivity ratio R CO2 / R N2While an upper limit does not necessarily have to be set, it is preferable that it be 200 or less from the viewpoint of improving the ease of manufacturing the gas separation membrane 1.

[0062] 2. Method for manufacturing gas separation membranes Next, a method for manufacturing the gas separation membrane according to the embodiment will be described. In the following description, the method for manufacturing the gas separation membrane 1 shown in Figure 1 will be used as an example.

[0063] Figure 2 is a process diagram showing the configuration of a method for manufacturing a gas separation membrane according to an embodiment. The method for manufacturing the gas separation membrane shown in Figure 2 comprises a solution contact step S102 and an energy application step S104. This manufacturing method allows for the efficient production of the gas separation membrane 1. Each step will be described below.

[0064] 2.1. Solution contact process In the solution contact step S102, a solution containing an amine is brought into contact with one side of a film containing an organopolysiloxane. The film containing the organopolysiloxane is, for example, a film with a thickness corresponding to the sum of the thicknesses of the support layer 3 and the separation layer 4 to be manufactured. By fixing such a film and supplying a solution so that the solution comes into contact with one side, the organopolysiloxane exposed on that side comes into contact with the amine.

[0065] Examples of amines include monoamines, polyamines, or derivatives thereof.

[0066] Examples of monoamines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, and allyl isopropylamine.

[0067] Examples of polyamines include diamines and triamines. Diamines include aliphatic diamines such as ethylenediamine (EDA), propylenediamine, tetramethylenediamine (TMDA), hexamethylenediamine (HMDA), octamethylenediamine (OMDA), dodecamethylenediamine (DMDA), norbornanediamine, and 1,3-bisaminomethylcyclohexane; and aromatic diamines such as orthoxylendiamine, metaxylenediamine (MXDA), paraxylenediamine (PXDA), diaminodiphenylmethane, diaminodiphenyl ether, diaminodiphenyl sulfone, and methylenebischloroaniline. Triamines include aliphatic triamines such as diethylenetriamine.

[0068] Of the amines mentioned above, polyamines are preferably used in this process, and diamines are also preferably used.

[0069] The solvent for the amine-containing solution can be any solvent capable of dissolving the amine, such as water, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), methanol, ethanol, isopropanol (IPA), methyl ethyl ketone (MEK), ethyl acetate, butyl acetate, toluene, acetone, cyclohexanone, hexane, polyethylene glycol, etc., and one or a mixture of two or more of these can be used.

[0070] The amine concentration in the solution containing the amine is not particularly limited, but is preferably 0.1% by mass or more and 90% by mass or less, and more preferably 1% by mass or more and 50% by mass or less.

[0071] The temperature of the solution containing the amine is not particularly limited, but is preferably between 10°C and 80°C, and more preferably between 20°C and 60°C.

[0072] Furthermore, when a solution containing amines penetrates the membrane, the thickness tA of the separation layer 4 can be adjusted according to the penetration depth. The penetration depth can be appropriately adjusted, for example, according to the contact time of the solution.

[0073] 2.2. Energy Transfer Process In the energy transfer step S104, energy is transferred to the membrane that has been contacted with a solution containing an amine. When energy is transferred, some of the chemical bonds in the organopolysiloxane, such as Si-O bonds, Si-C bonds, and CH bonds, are cleaved. Some of the chemical bonds in the amine are also cleaved. Then, structures derived from the amine bind to the binding sites formed on the organopolysiloxane after cleavage. This introduces CN bonds and CC bonds to the organopolysiloxane over a wide area, enabling the formation of the separation layer 4.

[0074] Examples of structures derived from amines include alkylamino groups. Alkylamino groups contain CN and CC bonds. Preferably, the alkylamino group has 2 to 18 carbon atoms. By adjusting the number of carbon atoms within this range, the intensity ratio I(CN) / I(CC) can be controlled.

[0075] Methods for contacting the amine-containing solution include, for example, coating, spraying, and immersion.

[0076] Methods for supplying energy include various treatments such as ultraviolet irradiation, plasma irradiation, and heating. Of these, ultraviolet irradiation or plasma irradiation is preferred, and ultraviolet irradiation is more preferred.

[0077] Furthermore, the intensity ratio I(CN) / I(CC) can be controlled according to the energy imparted. For example, since CN bonds have lower energy than CC bonds, CN bonds tend to be more easily cleaved than CC bonds. Therefore, the ratio of CC bonds to CN bonds can be adjusted according to the energy imparted.

[0078] Furthermore, using ultraviolet light or plasma allows for efficient cleavage of chemical bonds in organopolysiloxanes and amines while suppressing temperature increases. This enables efficient introduction of amine-derived structures and modification of the membrane while minimizing thermal denaturation. Examples of ultraviolet light generating devices include ultraviolet lamps and light-emitting diodes.

[0079] The method for generating plasma is not particularly limited, but an atmospheric pressure plasma device is preferably used. Furthermore, the method for irradiating with plasma is not particularly limited, but by using a method that involves transporting the plasma generated at the plasma generation site and irradiating it (plasma jet method), deterioration of the workpiece due to discharge, etc., can be suppressed.

[0080] 3. Applications of gas separation membranes The gas separation membrane 1 according to this embodiment can be used for the separation and recovery of carbon dioxide from a mixed gas containing carbon dioxide, the separation and purification of carbon dioxide, and the like. In particular, the use of the gas separation membrane 1 is effective in techniques for separating and recovering carbon dioxide contained in the atmosphere (direct air recovery (DAC)).

[0081] 4. Gas separation device Next, a gas separation apparatus according to an embodiment will be described. Figure 3 is a cross-sectional view showing the schematic configuration of the gas separation apparatus 5 according to this embodiment.

[0082] The gas separation device 5 shown in Figure 3 comprises a gas separation membrane 1, a fixed part 52, piping 53, and an exhaust part 54.

[0083] The fixing part 52 fixes the gas separation membrane 1. The fixing part 52 also has a perforated plate 51 that supports the gas separation membrane 1. The perforated plate 51 has numerous through holes. In addition, the fixing part 52 has an internal space 522 located on the support layer 3 side of the gas separation membrane 1.

[0084] The exhaust section 54 exhausts the gas from the internal space 522 via the piping 53. This reduces the pressure in the internal space 522, creating a negative pressure relative to the external space 524 located on the separation layer 4 side of the gas separation membrane 1.

[0085] With this configuration, the mixed gas G1 supplied to the external space 524 can be permeated through the gas separation membrane 1, and the permeate gas G2 can be recovered. The mixed gas G1 is a gas mixture in which the carbon dioxide concentration is greater than 0 volume% and less than or equal to 10 volume%, and is supplied at a supply pressure of 0.5 atmospheres to 2.0 atmospheres. In the permeate gas G2, the carbon dioxide concentration is higher than that of the mixed gas G1. As a result, carbon dioxide can be separated and recovered from the mixed gas G1.

[0086] Furthermore, the gas separation membrane 1 has a high gas selectivity and high gas permeability for carbon dioxide contained in the atmosphere and industrial exhaust gases, and also possesses sufficient mechanical strength. Therefore, a gas separation device 5 with excellent carbon dioxide separation performance can be realized.

[0087] 4. Effects of the above embodiment The gas separation membrane 1 according to the above embodiment has the function of separating carbon dioxide from a mixed gas supplied at a supply pressure of 0.5 atmospheres to 2.0 atmospheres, where the carbon dioxide concentration is greater than 0 volume% and 10 volume% or less. The gas separation membrane 1 also comprises a separation layer 4 and a support layer 3. The separation layer 4 is located on the side where the mixed gas is supplied and contains a polymer having CN bonds and CC bonds, and has the function of selectively separating carbon dioxide. The support layer 3 is located on the side opposite to the side where the mixed gas is supplied and contains an organopolysiloxane. Furthermore, when the thickness of the separation layer 4 is tA [nm] and the thickness of the support layer 3 is tB [nm], the separation layer 4 and the support layer 3 satisfy the following equations (1) and (2). When an XPS spectrum is obtained for the separation layer 4 by X-ray photoelectron spectroscopy and the C1s peak is waveform-separated, the intensity ratio I(CN) / I(CC) of the peak intensity I(CC) derived from the CN bond to the peak intensity I(CC) derived from the CC bond satisfies the following equation (3). 1 <tA+tB<1000 (1) 0.01 <tA / tB<0.20 (2) 0.03 <I(C-N) / I(C-C)<0.50 (3)

[0088] With this configuration, a gas separation membrane 1 can be realized that has a high gas selectivity and high gas permeability for carbon dioxide contained in the atmosphere and industrial exhaust gases, and also has sufficient mechanical strength.

[0089] In the gas separation membrane 1 according to the above embodiment, the separation layer 4 may be a resin layer that has been modified by introducing CN bonds and CC bonds into a part of the thickness direction of the membrane containing organopolysiloxane.

[0090] With this configuration, a gas separation membrane 1 is obtained in which the support layer 3 and the separation layer 4 are integrated. Such a gas separation membrane 1 has particularly good mechanical strength because delamination at the interface is less likely to occur. Furthermore, by selecting an organopolysiloxane with high gas permeability to carbon dioxide and modifying it, a gas separation membrane 1 that achieves a high degree of balance between gas permeability and gas selectivity can be realized.

[0091] In the gas separation membrane 1 according to the above embodiment, the gas permeability of nitrogen is R N2 Let R be the gas permeability of carbon dioxide. CO2 In this case, the gas selectivity ratio R CO2 / R N2 However, if it is 20 or more, the gas permeability of carbon dioxide is R CO2 However, it is preferable to have 200 GPUs or more.

[0092] This configuration makes it possible to realize a gas separation membrane 1 with high carbon dioxide separation efficiency. Furthermore, it reduces the amount of energy input required for separation.

[0093] In the gas separation membrane 1 according to the above embodiment, the organopolysiloxane contained in the support layer 3 may be polydimethylsiloxane.

[0094] With this configuration, since polydimethylsiloxane contains more Si-C bonds and is chemically stable, a support layer 3 is obtained that has better carbon dioxide gas permeability and superior stability.

[0095] The method for manufacturing a gas separation membrane according to the above embodiment is a method for manufacturing a gas separation membrane 1 according to the above embodiment, and comprises a solution contact step S102 and an energy impartment step S104. In the solution contact step S102, a solution containing an amine is brought into contact with one side of a membrane containing an organopolysiloxane. In the energy impartment step S104, energy is imparted to the membrane that has been in contact with the solution containing the amine.

[0096] With this configuration, a gas separation membrane 1 can be efficiently manufactured that has a high gas selectivity and high gas permeability for carbon dioxide contained in the atmosphere or industrial exhaust gas, and also has sufficient mechanical strength.

[0097] In the method for manufacturing a gas separation membrane according to the above embodiment, the energy application step may include a process of irradiating the membrane with ultraviolet light.

[0098] This configuration allows for efficient cleavage of chemical bonds in organopolysiloxanes and amines while suppressing temperature increases. Therefore, it is possible to efficiently introduce amine-derived structures and modify the membrane while minimizing thermal denaturation.

[0099] The gas separation apparatus 5 according to the above embodiment comprises a gas separation membrane 1 according to the above embodiment, a fixing part 52, and an exhaust part 54. The fixing part 52 fixes the gas separation membrane 1. An internal space 522 is formed on the support layer 3 side of the fixing part 52 to the gas separation membrane 1. The exhaust part 54 reduces the pressure of the internal space 522 so that it becomes a negative pressure relative to the external space 524 on the separation layer 4 side of the gas separation membrane 1.

[0100] With this configuration, a gas separation device 5 with excellent carbon dioxide separation performance can be realized.

[0101] Although the gas separation membrane, method for manufacturing the gas separation membrane, and gas separation apparatus according to the present invention have been described above based on preferred embodiments, the present invention is not limited thereto.

[0102] For example, the gas separation membrane and gas separation apparatus according to the present invention may be configured such that each part of the embodiment is replaced with a component having a similar function, or any component may be added to the embodiment.

[0103] Furthermore, the method for manufacturing a gas separation membrane according to the present invention may be modified by adding any desired steps to the above embodiment. [Examples]

[0104] Next, specific embodiments of the present invention will be described. 5. Fabrication of gas separation membrane 5.1. Example 1 First, a PDMS sheet was prepared. The PDMS sheet was a 30 μm thick sheet made of unsubstituted polydimethylsiloxane. Next, an aqueous ethylenediamine solution was applied to one side of the PDMS sheet. Then, one side of the PDMS sheet was irradiated with ultraviolet light at a wavelength of 365 nm for 1 hour. This introduced alkylamino groups to one side of the PDMS sheet, obtaining a gas separation membrane.

[0105] 5.2. Examples 2-6 and Comparative Examples 1-6 A gas separation membrane was obtained in the same manner as in Example 1, except that the configuration of the gas separation membrane was changed as shown in Table 1 (Figure 4).

[0106] Figure 4 is Table 1, which shows the configuration of the gas separation membrane for each example and comparative example, and the evaluation results of the gas separation membrane.

[0107] 6. Measurement of the layer thickness of the gas separation membrane For each example and comparative example of a gas separation membrane, the thickness of the support layer and the separation layer were measured by depth profiling using X-ray photoelectron spectroscopy. Next, based on the measurement results, the sum of the separation layer thickness tA [nm] and the support layer thickness tB [nm], tA + tB, and the ratio of the separation layer thickness tA [nm] to the support layer thickness tB [nm], tA / tB, were calculated. The calculation results are shown in Table 1 (Figure 4).

[0108] 6. X-ray photoelectron spectroscopy analysis of gas separation membranes X-ray photoelectron spectroscopy analysis was performed on the gas separation membranes of each example and comparative example to obtain XPS spectra. Waveform separation processing was then performed on the XPS spectra using analysis software to obtain peak intensities I(CC) and I(CN). The intensity ratio I(CN) / I(CC) was also calculated. The calculated intensity ratio I(CN) / I(CC) is shown in Table 1 (Figure 4).

[0109] Figure 5 shows an example of the XPS spectrum (C1s) near the C1s peak. Figure 5 also shows the CC and CN peaks separated by waveform separation processing.

[0110] 7. Evaluation of gas separation membranes The following evaluations were performed on the gas separation membranes of each example and each comparative example.

[0111] 7.1. Gas permeability (CO2 permeability) Test samples were prepared by cutting the gas separation membranes of each example and comparative example into circles with a diameter of 5 cm. Next, a gas permeability measuring device was used to supply a mixed gas, consisting of carbon dioxide and nitrogen in a volume ratio of 5:95, to the upstream side of the test sample. At this time, the total pressure on the upstream side was adjusted to 1.2 atmospheres, the flow rate of the mixed gas to 500 mL / min, and the temperature to 40°C. The gas permeability was measured in accordance with the gas permeability test method (Part 1: Differential pressure method) specified in JIS K 7126-1:2006. A GTR-11A / 31A gas permeability measuring device manufactured by GTR Tech Co., Ltd. was used. In this device, the gas that has permeated through the test sample is introduced into a gas chromatograph, and the gas permeability of each component is measured.

[0112] Next, the CO2 permeability in each gas separation membrane was calculated from the analysis results. The calculation results are shown in Table 1 (Figure 4).

[0113] 7.2. Gas selectivity (CO2 / N2 selectivity ratio) Based on the analysis results described above, the N2 permeability in the gas separation membrane was calculated. Next, the ratio of CO2 permeability to N2 permeability was calculated as the "CO2 / N2 selectivity ratio." The calculation results are shown in Table 1 (Figure 4).

[0114] 7.3. Gas strength (durability) The gas separation membranes of each example and comparative example were set in a gas permeability measuring device, and the downstream side was depressurized so that the pressure difference (differential pressure) between the upstream and downstream sides was 0.1 MPa. This state was then maintained for one week.

[0115] After one week, the gas separation membrane was removed and examined under magnification to check for any damage. The observation results were then evaluated against the following criteria. The evaluation results are shown in Table 1.

[0116] A: No damage was observed in the gas separation membrane. C: Damage was observed in the gas separation membrane.

[0117] As is clear from Table 1, the gas separation membranes of each example were found to have a high gas selectivity and high gas permeability for carbon dioxide, as well as excellent mechanical strength. [Explanation of Symbols]

[0118] 1...Gas separation membrane, 3...Support layer, 4...Separation layer, 5...Gas separation device, 31...Top surface, 51...Perforated plate, 52...Fixing part, 53...Piping, 54...Exhaust part, 522...Internal space, 524...External space, G1...Mixed gas, G2...Permeate gas, S102...Solution contact process, S104...Energy transfer process, tA...Layer thickness, tB...Layer thickness

Claims

1. A gas separation membrane having the function of separating carbon dioxide from a mixed gas supplied at a supply pressure of 0.5 atmospheres or more and 2.0 atmospheres or less, wherein the carbon dioxide concentration is greater than 0 volume% and 10 volume% or less. A separation layer is provided on the side of the space to which the mixed gas is supplied, and contains a polymer having C-N bonds and C-C bonds, and has the function of selectively separating carbon dioxide. A support layer containing an organopolysiloxane is located on the opposite side from the space to which the mixed gas is supplied, Equipped with, When the thickness of the separation layer is tA [nm] and the thickness of the support layer is tB [nm], The separation layer and the support layer satisfy the following equations (1) and (2): When an XPS spectrum is obtained from the aforementioned separation layer by X-ray photoelectron spectroscopy and the C1s peak is waveform-separated, A gas separation membrane characterized in that the intensity ratio I(C-N) / I(C-C) of the peak intensity I(C-C) derived from the C-N bond to the peak intensity I(C-C) derived from the C-C bond satisfies the following formula (3). 1<tA+tB<1000 (1) 0.01<tA / tB<0.20 (2) 0.03<I(CN) / I(CC)<0.50 (3)

2. The gas separation membrane according to claim 1, wherein the separation layer is a resin layer modified by introducing C-N bonds and C-C bonds into a part of the thickness direction of a membrane containing organopolysiloxane.

3. The nitrogen gas permeability is R Ｎ２ Let R be the gas permeability of carbon dioxide. ＣＯ２ In this case, the gas selectivity ratio R ＣＯ２ / R Ｎ２ However, it is 20 or more, The gas permeability of carbon dioxide is R ＣＯ２ The gas separation membrane according to claim 1 or 2, wherein the capacity is 200 GPU or more.

4. The gas separation membrane according to claim 1 or 2, wherein the organopolysiloxane contained in the support layer is polydimethylsiloxane.

5. A method for producing a gas separation membrane according to claim 1 or 2, A step of contacting one side of a film containing organopolysiloxane with a solution containing an amine, A step of applying energy to the film that has been brought into contact with the aforementioned solution, A method for producing a gas separation membrane, characterized by having [a certain characteristic].

6. The method for manufacturing a gas separation membrane according to claim 5, wherein the energy application step includes irradiating the membrane with ultraviolet light.

7. A gas separation membrane according to claim 1 or 2, A fixing portion that fixes the gas separation membrane and has an internal space formed on the support layer side of the gas separation membrane, An exhaust section that reduces the internal space so that the external space on the separation layer side of the gas separation membrane becomes negatively pressurized, A gas separation apparatus characterized by comprising the following:

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