WO2024214595A1 - 気体分離用複合膜およびそれを用いた気体分離システム - Google Patents

気体分離用複合膜およびそれを用いた気体分離システム Download PDF

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WO2024214595A1
WO2024214595A1 PCT/JP2024/013613 JP2024013613W WO2024214595A1 WO 2024214595 A1 WO2024214595 A1 WO 2024214595A1 JP 2024013613 W JP2024013613 W JP 2024013613W WO 2024214595 A1 WO2024214595 A1 WO 2024214595A1
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composite membrane
gas
gas separation
separation
permeability
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French (fr)
Japanese (ja)
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小川久美子
新名清輝
広沢洋帆
武内紀浩
水野耀介
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東レ株式会社
人工光合成化学プロセス技術研究組合
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/10—Spiral-wound membrane modules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides

Definitions

  • the present invention relates to a composite membrane for gas separation capable of selectively separating at least one component from a gas mixture, and a gas separation system using the same.
  • Hydrogen is obtained by reforming and gasifying fossil fuels such as natural gas and coal, and removing unnecessary gases from the mixed gas containing hydrogen and carbon dioxide as its main components. It can also be obtained by decomposing water using electricity or photocatalysis, and extracting only the hydrogen from the mixed gas containing hydrogen, oxygen, and water vapor. Hydrogen is also used in the Haber-Bosch process, which synthesizes ammonia. This is a method of synthesizing ammonia by reacting hydrogen and nitrogen at high temperature and pressure, but a process is required to separate and recover the unreacted hydrogen and nitrogen at the production plant.
  • Membrane separation which exploits differences in the gas permeability of materials to selectively allow the target gas to pass through, has been attracting attention as a low-cost method for concentrating a specific gas from a gas mixture.
  • Patent Document 1 proposes a method of improving the selective separation of gases by attaching a surfactant to a single-layer hollow fiber membrane.
  • Non-Patent Document 1 describes a technology for improving the selective separation of helium and carbon dioxide by applying a polyphenylene oxide coating to the surface of a polyamide composite membrane.
  • Non-Patent Document 2 describes a method for improving the selective separation of methane and other gases by applying a polydimethylsiloxane coating to the surface of an RO membrane.
  • the present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a composite membrane for gas separation that has high permeability to gases with small molecular diameters, such as hydrogen, helium, water vapor, and ammonia, and high selective separation ability from other gases, such as oxygen, nitrogen, and methane, as well as a composite module for gas separation, a gas separation system, and a method for purifying helium (He) or hydrogen (H 2 ) that use the same.
  • gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia
  • other gases such as oxygen, nitrogen, and methane
  • the inventors conducted extensive research to solve the above problems, and as a result, significantly improved the performance of composite membranes for gas separation, particularly their selective separation properties.
  • the present invention has the following features:
  • the separating functional layer is mainly composed of a crosslinked aromatic polyamide or polyimide.
  • a composite membrane for gas separation having at least a porous support layer, a separation functional layer, and a coating layer in this order, wherein the separation functional layer is mainly composed of a crosslinked aromatic polyamide, and the coating layer is mainly composed of silicone.
  • the coating layer has an average pore diameter Rc of 0.6 nm or more and 1.2 nm or less.
  • a spiral-type composite membrane module for gas separation in which the composite membrane for gas separation according to any one of (1) to (14), a feed-side flow path material, and a permeate-side flow path material are wound around a central tube.
  • a gas separation system comprising the spiral-type composite membrane module for gas separation according to (15).
  • the present invention provides a composite membrane for gas separation that has high selectivity for separating gases with small molecular diameters, such as hydrogen, helium, water vapor, and ammonia, a spiral-type composite membrane module for gas separation, and a gas separation system using the same.
  • FIG. 1 is a cross-sectional view of a composite membrane for gas separation according to one embodiment of the present invention.
  • FIG. 2 is a partially exploded perspective view of a spiral-type composite membrane module for gas separation.
  • the composite membrane for gas separation of the present invention is a composite membrane for gas separation having at least a porous support layer, a separation functional layer and a coating layer in this order, and has a helium permeability of 1.0 nmol/ m2 /s/Pa or more at 25°C, and when nanoperm porometry analysis is performed under conditions of a temperature of 40°C with helium as a non-condensable gas and H2O as a condensable gas, the helium permeability at a relative humidity of 90% is 90% or more of the helium permeability at a relative humidity of 20%.
  • the composite membrane for gas separation of the present invention will be described in detail below.
  • the composite membrane for gas separation (51) of this embodiment comprises at least a porous support layer (52), a separation functional layer (53), and a coating layer (54) in this order. It may also have a substrate (55). Furthermore, this composite membrane for gas separation has a helium permeability of 1.0 nmol/ m2 /s/Pa or more at 25°C, and when nanoperm porometry analysis is performed at a temperature of 40°C with helium as the non-condensable gas and H2O as the condensable gas, the helium permeability at a relative humidity of 90% is 90% or more of the helium permeability at a relative humidity of 20%.
  • the composite membrane for gas separation of the present invention may have a substrate.
  • the substrate does not need to have a selective gas separation capability, but only needs to support the separation functional layer and provide strength to the entire composite membrane for gas separation.
  • the resin constituting the substrate is not particularly limited, but examples include polyester polymers, polyamide polymers, polyolefin polymers, polysulfide polymers, and mixtures or copolymers of these. Among these, polyester polymers and polysulfide polymers, which have high mechanical strength and thermal stability, are particularly preferred as the resin constituting the substrate.
  • the form of the substrate is not particularly limited, but nonwoven fabrics or woven/knitted fabrics such as long-fiber nonwoven fabrics and short-fiber nonwoven fabrics are preferred, and it is particularly preferred to use long-fiber nonwoven fabrics.
  • long-fiber nonwoven fabric refers to nonwoven fabrics with an average fiber length of 300 mm or more and an average fiber diameter of 3 to 30 ⁇ m.
  • the composite membrane for gas separation of the present invention has a porous support layer.
  • the porous support layer may be any layer that can permeate hydrogen or helium.
  • the porous support layer may support the separation functional layer and provide strength to the composite membrane for gas separation as a whole.
  • the porous support layer may or may not have selective gas separation and permeation ability, but it is more preferable to have selective permeation ability, since this increases the selectivity of the composite membrane for gas separation.
  • the size and distribution of the pores in the porous support layer are not particularly limited, but for example, the pore size may be uniform throughout the entire porous support layer, or may gradually increase from the surface of the porous support layer that contacts the separation functional layer to the other surface.
  • the material of the porous support layer is not particularly limited, but examples include homopolymers or copolymers such as polysulfone, polyethersulfone, polyamide, polyaramid, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide, which can be used alone or in combination.
  • cellulose polymers include cellulose acetate and cellulose nitrate
  • vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile.
  • the material for the porous support layer is preferably a homopolymer or copolymer such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, or polyphenylene sulfide sulfone.
  • Cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone are more preferred because they have high chemical, mechanical, and thermal stability, with polysulfone and cellulose acetate being particularly preferred.
  • the thickness of the substrate and the porous support layer affects the strength of the composite semipermeable membrane and the packing density when it is made into an element. From the viewpoint of obtaining good mechanical strength and packing density, the total thickness of the substrate and the porous support layer is preferably 30 to 300 ⁇ m, more preferably 100 to 220 ⁇ m.
  • the thickness of the porous support layer is preferably 20 to 100 ⁇ m. More preferably, it is 23 ⁇ m to 50 ⁇ m, and even more preferably 27 ⁇ m to 40 ⁇ m.
  • the thickness of the substrate and the porous support layer can be obtained by calculating the average thickness of 20 points measured at 20 ⁇ m intervals in a direction perpendicular to the thickness direction (membrane surface direction) by cross-sectional observation.
  • the thickness of the substrate or the composite semipermeable membrane may be measured with a thickness gauge.
  • the thickness of the separation functional layer is very thin compared to the thickness of the porous support layer and can be ignored, so the thickness of the separation functional layer provided on the porous support layer can be considered as the thickness of the porous support layer. Therefore, the thickness of the composite semipermeable membrane is measured with a digital thickness gauge, and the thickness of the porous support layer can be calculated by subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane.
  • a digital thickness gauge a PEACOCK manufactured by Ozaki Seisakusho Co., Ltd. can be used.
  • the material of the separation functional layer in the composite membrane for gas separation of the present invention is not particularly limited, but it is preferable to use cellulose, polyimide, polyamide, etc., and a composite membrane having a separation functional layer containing polyamide is preferable.
  • the separation functional layer is mainly composed of polyamide, it can be formed by performing interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide on a porous support layer.
  • polyamide is the main component
  • polyamide accounts for 50% by weight or more, and the amount of polyamide in a 100% by weight separation functional layer is preferably 80% by weight or more, and more preferably 90% by weight or more and 100% by weight or less.
  • the polyamide in the separation functional layer may be a wholly aromatic polyamide, a wholly aliphatic polyamide, or a mixture of aromatic and aliphatic portions, but to achieve higher performance, it is preferable that it is wholly aromatic.
  • polyfunctional amines are polyfunctional aromatic amines or polyfunctional aliphatic amines.
  • Polyfunctional aromatic amines refer to aromatic amines having two or more amino groups selected from primary amino groups and secondary amino groups in one molecule, at least one of which is a primary amino group.
  • Polyfunctional aliphatic amines refer to aliphatic amines having two or more amino groups selected from primary amino groups and secondary amino groups in one molecule.
  • examples of polyfunctional aromatic amines include polyfunctional aromatic amines in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions, such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine.
  • polyfunctional aliphatic amines examples include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, piperazine, 2-methylpiperazine, 2,4-dimethylpiperazine, 2,5-dimethylpiperazine, and 2,6-dimethylpiperazine. These polyfunctional amines may be used alone or in combination of two or more.
  • polyfunctional acid halide is specifically a polyfunctional aromatic acid halide or a polyfunctional aliphatic acid halide.
  • a polyfunctional acid halide is an acid halide that has at least two halogenated carbonyl groups in one molecule.
  • an example of a trifunctional acid halide is trimesic acid chloride
  • examples of bifunctional acid halides are biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, etc.
  • the polyfunctional acid halide is preferably a polyfunctional acid chloride, and in consideration of the selectivity and heat resistance of the composite membrane for gas separation, it is preferable that the polyfunctional acid chloride has 2 to 4 carbonyl chloride groups in one molecule.
  • trimesoyl chloride is more preferred from the viewpoints of ease of availability and ease of handling.
  • These polyfunctional acid halides may be used alone or in combination of two or more kinds.
  • polycondensation reaction is specifically interfacial polycondensation.
  • the separation functional layer of the present invention preferably contains crosslinked aromatic polyamide as the main component.
  • Crosslinked aromatic polyamide can be formed by performing interfacial polycondensation between a polyfunctional aromatic amine and a polyfunctional aromatic acid halide.
  • the thin film may have a pleated structure with concave and convex portions.
  • the surface area of the membrane that has the separation function increases relative to the membrane area, thereby increasing the gas permeability.
  • the composite membrane for gas separation of the present invention has a coating layer on a separation functional layer.
  • the separation functional layer has a small number of regions with extremely high gas permeability due to coarse pores, defects, etc. In such regions, the contribution of separation by molecular sieves is small, and the selective separation property for gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia is low. Reducing the contribution of regions with low selective separation property due to coarse pores, defects, etc. is important for improving the selective separation property of the entire membrane.
  • the coating layer significantly suppresses the permeation of oxygen, nitrogen, methane, etc., but has little effect on the permeation of light gases such as hydrogen and helium, greatly improving selective separation.
  • the coating layer does not necessarily have to cover the entire surface of the separation functional layer. There may be cases where the coating layer is partially missing due to unevenness in the coating when forming the coating layer, or the coating layer may be formed only on surfaces with particularly large pores and defects.
  • the coating layer can penetrate into the separation functional layer and the support layer.
  • the coating layer components penetrate into the support layer, they block the gas permeation path, which tends to reduce the permeability.
  • the adhesive strength between the functional layer and the support layer, or between the support layer and the substrate may be reduced, or the support layer structure may be destroyed, causing gas to leak through the gaps and reducing selectivity. Therefore, it is preferable that the coating layer penetrates into the support layer as little as possible.
  • the penetration depth of the coating layer into the support layer depends on the structure of the coating layer and the support layer, but it is possible to map the elements contained only in the support layer and only in the coating layer using TEM-EDX (transmission electron microscope-energy dispersive X-ray spectroscopy), or to perform component analysis in the depth direction using TOF-SIMS (time-of-flight secondary ion mass spectrometry).
  • TEM-EDX transmission electron microscope-energy dispersive X-ray spectroscopy
  • TOF-SIMS time-of-flight secondary ion mass spectrometry
  • the support layer is polysulfone and the coating layer is silicone
  • the S contained in the polysulfone and the Si contained in the coating layer are mapped using TEM-EDX, and the penetration depth is determined within the overlapping range.
  • the overlap of Si and S i.e., the penetration thickness, is preferably 0 to 150 nm, more preferably 0 to 130 nm, and even more preferably 0
  • the average pore diameter Rc [nm] of the coating layer formed by the positron beam method is preferably 0.6 nm or more and 1.2 nm or less, more preferably 0.7 nm or more and 1.0 nm or less, and even more preferably 0.75 nm or more and 0.85 nm or less.
  • the average pore diameter Rc [nm] of the coating layer 0.6 nm or more it is possible to maintain as high a permeability as possible for gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia, and by making it 1.2 nm or less, it is possible to effectively suppress the permeation of oxygen, nitrogen, methane, etc. caused by coarse pores and defects in the functional layer.
  • the positron beam method is one of the positron annihilation lifetime measurement methods, and is a method for non-destructively evaluating information on the size, number density, and distribution of vacancies of about 0.1 to 10 nm from the time of annihilation of a positron incident on a sample.
  • the positron beam method uses a positron beam instead of a radioisotope ( 22Na ) as a positron source, which is different from the usual positron annihilation method and enables the measurement of thin films of about several hundred nm thick.
  • the average vacancy diameter Rc [nm] of the coating layer is calculated from the positron annihilation lifetime ⁇ when a positron is implanted with a strength of 1 keV from the surface having the coating layer.
  • the average pore diameter Rc [nm] of the coating layer of the composite membrane for gas separation of the present invention is calculated from the following formula 3 based on the above-mentioned positron annihilation lifetime ⁇ .
  • Formula 3 shows the relationship when it is assumed that orthopositronium (o-Ps) is present in pores of average pore diameter Rc in an electron layer of thickness ⁇ R, and ⁇ R has been empirically determined to be 0.166 nm (details are described in Nakanishi et al., Journal of Polymer Science, Part B: Polymer Physics, Vol. 27, p. 1419, John Wiley & Sons, Inc. (1989)).
  • Materials that can be used to form the coating layer include organic materials such as silicone resins, polyolefin resins, polyvinyl alcohol, and polyurethane, as well as metal-organic frameworks such as MOFs (Metal Organic Frameworks), and metal-based materials using palladium or palladium alloys as hydrogen permeable materials.
  • organic materials such as silicone resins, polyolefin resins, polyvinyl alcohol, and polyurethane
  • metal-organic frameworks such as MOFs (Metal Organic Frameworks)
  • metal-based materials using palladium or palladium alloys as hydrogen permeable materials include metal-organic frameworks such as MOFs (Metal Organic Frameworks), and metal-based materials using palladium or palladium alloys as hydrogen permeable materials.
  • Polysiloxanes are preferred from the viewpoints of ease of availability, ease of handling, and the fact that they are materials whose average pore diameter Rc [nm] satisfies the above-mentioned range.
  • the thickness of the coating layer is preferably 0.2 ⁇ m to 2.0 ⁇ m, more preferably 0.5 ⁇ m to 1.5 ⁇ m, and even more preferably 0.7 ⁇ m to 1.2 ⁇ m. By making it 0.2 ⁇ m or more, it is possible to prevent defects in the coating layer caused by unevenness in the separation functional layer or uneven thickness of the coating. By making it 2.0 ⁇ m or less, it is possible to reduce the reduction in gas permeability caused by the coating layer and maintain a high gas permeability.
  • the thickness of the coating layer can be determined by observing the cross-section of the composite membrane for gas separation using a scanning electron microscope and analyzing the cross-sectional image obtained. The freeze fracturing method is used to prepare the observation sample. Specifically, the sample is frozen using a refrigerant such as liquid nitrogen, and the cross-section is exposed using a razor or microtome. Image analysis software such as ImageJ and Mac-View can be used for image analysis.
  • the Si -peak in the region at a depth of 0 to 50 nm from the surface on the coating layer side detected by time-of-flight secondary ion mass spectrometry is preferably 10,000 counts or more, more preferably 15,000 counts or more, and even more preferably 20,000 counts or more.
  • TOF-SIMS time-of-flight secondary ion mass spectrometry
  • the composite membrane for gas separation of the present invention has a helium permeability at 25° C. of preferably 1.10 to 1.65 times, more preferably 1.20 to 1.60 times, and even more preferably 1.30 to 1.50 times, the hydrogen permeability.
  • the kinetic molecular diameter (also called the dynamic molecular diameter) of helium is 0.260 nm, and that of hydrogen is 0.289 nm, with helium molecules being slightly smaller than hydrogen.
  • the helium permeability is 1.10 times or more the hydrogen permeability
  • selective separation from gases with larger molecular diameters can be achieved by screening according to the molecular diameter of the gas, and when it is 1.65 times or less, it is possible to prevent a decrease in hydrogen permeability due to excessively small pores and inhibition of hydrogen permeation due to low hydrogen solubility.
  • the hydrogen permeability at 25°C is preferably from 1 nmol/ m2 /s/Pa to 100 nmol/ m2 /s/Pa, more preferably from 5 nmol/ m2 /s/Pa to 60 nmol/ m2 /s/Pa, and even more preferably from 10 nmol/ m2 /s/Pa to 40 nmol/ m2 /s/Pa.
  • a hydrogen permeability of 1 nmol/ m2 /s/Pa or more can reduce the membrane area required for hydrogen separation, and a hydrogen permeability of 100 nmol/ m2 /s/Pa or less can suppress membrane surface polarization when hydrogen permeation is performed under high pressure conditions, preventing a decrease in separation performance.
  • the helium permeability at a relative humidity of 90% is 90% to 100% of the helium permeability at a relative humidity of 20%, more preferably 95% or more, even more preferably 96% or more, and particularly preferably 97% or more.
  • Nanoperm porometry is an analytical technique that can measure the pore size distribution of 0.5 nm to 50 nm in relation to the capillary condensation diameter by supplying a mixture of condensable and non-condensable gases to a measurement sample, changing the relative pressure of the condensable gas, and measuring the change in the amount of non-condensable gas that permeates from the sample.
  • the capillary condensation diameter is 1.2 nm at a temperature of 40°C and a relative humidity of 20%, and is 20 nm at a temperature of 40°C and a relative humidity of 90%.
  • the contribution of capillary condensation diameters of about 1.2 nm to about 20 nm to the helium permeability is 10% or less, which means that there are few coarse pores of nano size or larger.
  • the helium permeability at a relative humidity of 90% and that at a relative humidity of 20% may differ only by an error level, and the helium permeability at a relative humidity of 90% may be 100% or more of the helium permeability at a relative humidity of 20%. In this case, it is defined as 100%.
  • the helium permeability at 25°C in the present invention is set to 1.0 nmol/ m2 /s/Pa or more.
  • the pore diameter d NKP [nm] of the composite membrane for gas separation which is determined by the average pore radius Rf [nm] of the separating functional layer and formula 2, preferably satisfies formula 1.
  • i is any one of H2 , N2 , and CH4
  • Pi is the permeability of gas i at 25°C [nmol/ m2 /s/Pa]
  • PHe is the permeability of helium gas at 25°C [nmol/ m2 /s/Pa]
  • Mi is the molecular weight of gas i
  • MHe is the molecular weight of helium gas
  • dk ,i is the kinetic molecular diameter of gas i [nm]
  • dk ,He is the kinetic molecular diameter of helium gas [nm].
  • the average pore radius Rf [nm] of the separation functional layer can be calculated from pore size analysis of the separation functional layer observed by a positron beam method or a scanning transmission electron microscope (hereinafter, "STEM").
  • the positron beam method is one of the positron annihilation lifetime measurement methods, and is a method for non-destructively evaluating information on the size, number density, and distribution of vacancies of about 0.1 to 10 nm from the time of annihilation of a positron incident on a sample.
  • the positron beam method uses a positron beam instead of a radioisotope ( 22Na ) as a positron source, which is different from the usual positron annihilation method and enables the measurement of thin films of about several hundred nm thick.
  • the average vacancy radius Rf [nm] of the separation functional layer is calculated from the positron annihilation lifetime ⁇ when a positron is implanted with a strength of 1 keV from the surface having the separation functional layer.
  • the sample with the substrate and support layer removed is transferred to a grid for TEM observation and measured using scanning electron microscopy (SEM) with the STEM and a secondary electron detector attached to the STEM device.
  • SEM scanning electron microscopy
  • the acquired STEM image is deconvoluted using DeConvHAADF (HREM research inc.) to highlight the pores and polyamide structure.
  • binarization is performed using ImageJ, and particle size analysis is performed to quantitatively analyze the number and diameter of pores in each region. From this analysis, the diameter and area of each pore can be calculated as the number of pixels in the image.
  • the average pore radius Rf [nm] of the separation functional layer is preferably 0.2 nm or more and 0.4 nm or less, more preferably 0.22 nm or more and 0.35 nm or less, and even more preferably 0.24 nm or more and 0.30 nm or less.
  • the average pore radius Rf [nm] of the separation functional layer is 0.2 nm or more, the permeability of the gas to be transmitted through the membrane can be increased, and when it is 0.4 nm or less, it is possible to express selective separation properties according to the molecular diameter of the gas.
  • the pore size d NKP [nm] of the composite membrane for gas separation of the present invention is calculated based on the NKP (Normalized-Knudsen-based Permance) method from the following (Equation 2).
  • the NKP method is a method in which the membrane permeation flow rates of many kinds of non-condensable gases with different molecular diameters are measured, the kinetic molecular diameter of the gas is plotted on the horizontal axis and the membrane permeation flow rate is plotted on the vertical axis, and the pore size d NKP [nm] is calculated by curve fitting using (Equation 2).
  • non-condensable gases helium, hydrogen, N2 , and CH4 (details are described in Lie Meng et al., Journal of Membrane Science, Vol. 496, pp. 211-218, Department of Chemical Engineering, graduate School of Engineering, Hiroshima University (2015)).
  • the separation functional layer of a composite membrane for gas separation has a pore size distribution. Ideally, it would have only appropriate pores with the appropriate pore size for excellent selective separation of the target gas, but in reality, it often has coarse pores with low selective separation, and in order to improve selective separation, it is important to reduce the contribution of coarse pores.
  • the pore diameter d NKP [nm] calculated by the NKP method is smaller than the pore diameter (2Rf) calculated from the average pore radius Rf [nm] of the separation functional layer.
  • the pore diameter d NKP [nm] calculated by the NKP method is preferably 0.60 times or more and 0.90 times or less than the pore diameter (2Rf) calculated from the average pore radius Rf [nm] of the separation functional layer, that is, it satisfies formula 1, more preferably 0.65 times or more and 0.85 times or less, and even more preferably 0.70 times or more and 0.80 times or less.
  • the permeation of gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia can be increased, and by making the "pore diameter d NKP / pore diameter (2Rf)" 0.90 times or less, the selective separation can be increased.
  • Methods for reducing the contribution of coarse pores in the separation functional layer include coating the surface of the separation functional layer, adsorption of different substances to the functional layer and/or the porous support layer, densifying the support membrane by improving the manufacturing method, and compacting the porous support layer by applying pressure. Using these methods to provide gas permeation resistance to areas other than the separation functional layer is important for reducing the contribution of coarse pores.
  • the contact angle between the surface of the coating layer and pure water in air is preferably 50° or more and 130° or less.
  • a contact angle of 50° or more can suppress gas permeation through the coarse pores, and can significantly suppress the permeation of oxygen, nitrogen, methane, etc.
  • a contact angle of 130° or less can suppress a decrease in the permeability of light gases such as hydrogen and helium, and can exhibit high selective separation properties.
  • a contact angle of 80° or more and 130° or less is more preferable, and a contact angle of 100° or more and 130° or less is particularly preferable.
  • the contact angle here refers to the static contact angle.
  • 3.0 ⁇ L of distilled water was dropped onto the coating layer side of the composite membrane for gas separation, and the contact angle (the angle between the tangent of the droplet and the solid surface) was measured 1 second after the water droplet was dropped.
  • the contact angle the angle between the tangent of the droplet and the solid surface
  • ⁇ S is the surface tension of the coating layer
  • ⁇ L is the surface tension of pure water
  • ⁇ SL is the interfacial tension between the coating layer and pure water.
  • the contact angle can be measured using a commercially available device, for example, a Contact Angle meter (manufactured by Kyowa Interface Science Co., Ltd.).
  • the contact angle gradually decreases over time.
  • the contact angle 1 second after a drop of pure water lands on the surface of the coating layer is X and the contact angle 30 seconds after is Y, the following formula 6 holds true.
  • Y/X is preferably 0.8 or more and 1 or less, more preferably 0.9 or more and 1 or less, and particularly preferably 0.95 or more and 1 or less.
  • Y/X is in this range, it is possible to promote the permeation of light gases such as hydrogen and helium, and to suppress the permeation of gases such as oxygen and nitrogen, thereby achieving high selective separation properties.
  • the method of forming the support membrane includes a step of preparing a polymer solution by dissolving a polymer, which is a component of the porous support layer, in a good solvent for the polymer, a step of applying the polymer solution to the substrate, and a step of wet-coagulating the polymer by immersing the polymer solution in a coagulation bath.
  • the coagulated polymer corresponds to the porous support layer.
  • a polymer solution is obtained by dissolving it in N,N-dimethylformamide (DMF). Water is preferably used as the coagulation bath.
  • DMF N,N-dimethylformamide
  • Aramid an example of a polymer
  • a polymer can be obtained by solution polymerization or interfacial polymerization using acid chlorides and diamines as monomers.
  • aprotic organic polar solvents such as N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethylacetamide (DMAc) can be used as the solvent.
  • DMF N-dimethylformamide
  • NMP N-methylpyrrolidone
  • DMAc dimethylacetamide
  • acid chlorides and diamines are used as monomers to produce polyamide, hydrogen chloride is produced as a by-product.
  • inorganic neutralizing agents such as calcium hydroxide, calcium carbonate, and lithium carbonate, as well as organic neutralizing agents such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine, and diethanolamine are used.
  • the separation functional layer made of polyamide is formed by forming polyamide on the support membrane through interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide.
  • the process for forming the separation functional layer includes the following steps. (a) applying an aqueous solution containing a polyfunctional amine onto a porous support layer; (b) after step (a), applying to the porous support layer an organic solvent solution containing a polyfunctional acid halide.
  • the concentration of the polyfunctional amine in the aqueous polyfunctional amine solution is preferably in the range of 0.1% by weight to 20% by weight, more preferably in the range of 0.5% by weight to 15% by weight. If the concentration of the polyfunctional amine is in this range, sufficient selective separation properties and gas permeability can be obtained.
  • the polyfunctional amine aqueous solution may contain surfactants, organic solvents, alkaline compounds, antioxidants, etc., as long as they do not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide.
  • the surfactant has the effect of improving the wettability of the support membrane surface and reducing the interfacial tension between the polyfunctional amine aqueous solution and the non-polar solvent.
  • the application of the polyfunctional amine aqueous solution to the porous support layer is preferably performed uniformly and continuously on the porous support layer.
  • Application means contacting the polyfunctional amine aqueous solution with the porous support layer, specifically coating the surface of the porous support layer with the polyfunctional amine aqueous solution, or immersing the support film in the polyfunctional amine aqueous solution.
  • Coating methods include dripping, spraying, and roller application.
  • the time from when the aqueous solution of a polyfunctional amine is applied onto the porous support layer until the liquid is drained or until the aqueous solution of a polyfunctional acid halide is applied is preferably from 1 second to 10 minutes, and more preferably from 10 seconds to 3 minutes.
  • the solution After applying the polyfunctional amine aqueous solution to the porous support layer, the solution is drained so that no droplets remain on the porous support layer. Areas where droplets remain can become membrane defects and reduce separation performance, but draining the solution can prevent this.
  • Methods that can be used include holding the support membrane vertically after applying the polyfunctional amine aqueous solution to allow excess aqueous solution to flow naturally, or spraying an air current such as nitrogen from an air nozzle to forcibly drain the solution.
  • the concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01% by weight to 10% by weight, and more preferably in the range of 0.02% by weight to 2.0% by weight.
  • a concentration of 0.01% by weight or more ensures a sufficient reaction rate, while a concentration of 10% by weight or less can suppress the occurrence of side reactions.
  • the organic solvent is preferably one that is immiscible with water, dissolves the polyfunctional acid halide, and does not destroy the support film, and is inactive against the polyfunctional amine compound and the polyfunctional acid halide.
  • Preferred examples include hydrocarbon compounds such as n-hexane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, isooctane, isodecane, and isododecane, or mixtures thereof.
  • the method for applying the polyfunctional acid halide solution to the porous support layer may be the same as the method for applying the polyfunctional amine aqueous solution to the porous support layer. However, since it is preferable to apply the polyfunctional acid halide solution to only one side of the porous support layer, it is preferable to apply it by coating rather than immersion.
  • the porous support layer that has been contacted with the organic solvent solution of the polyfunctional acid halide may be heated.
  • the temperature for the heat treatment is 50°C or higher and 180°C or lower, preferably 60°C or higher and 160°C or lower. Heating at 60°C or higher can compensate for the decrease in reactivity that accompanies the consumption of monomers in the interfacial polymerization reaction by using heat to promote the reaction. Heating at 160°C or lower can prevent the solvent from completely volatilizing, which would result in a significant decrease in reaction efficiency.
  • the heat treatment time for each time is preferably 5 seconds or higher and 600 seconds or lower. A time of 5 seconds or longer can provide a reaction promotion effect, and a time of 600 seconds or less can prevent the solvent from completely volatilizing.
  • a polyfunctional halide may be added during the interfacial polycondensation reaction to promote consumption of the polyfunctional amine.
  • the coating layer is preferably formed by contacting the separation functional layer with a solution or emulsion containing a substance that forms a coating layer.
  • the contact method is not particularly limited, but it is preferable to coat the separation functional layer with a solution or emulsion containing a substance that forms a coating layer, since it is easy to control the thickness of the coating layer.
  • Other contact methods include application from the porous support layer side and immersion of the membrane in a solution.
  • the coating method is not particularly limited, but microgravure, bar coating, spin coating, etc., which are suitable for thin film coating, are preferred.
  • Solvents for the solution or emulsion containing the substance that forms the coating layer include water, alcohols such as ethanol, 2-butanol, and isopropanol, alkanes such as pentane, hexane, heptane, octane, nonane, decane, and dodecane, benzene, toluene, and chloroform, with water, ethanol, and hexane being preferred because they cause less deterioration of the separation functional layer and the porous support layer.
  • the pH of the aqueous solution is preferably in the range of 3 to 11 in order to minimize deterioration of the composite membrane for gas separation.
  • the material forming the coating layer may be an organic material such as silicone resin, polyolefin resin, polyvinyl alcohol, or polyurethane, or a metal-organic framework such as MOF (Metal Organic Framework), or a metal-based material using palladium or a palladium alloy as a hydrogen permeable material.
  • organic material such as silicone resin, polyolefin resin, polyvinyl alcohol, or polyurethane, or a metal-organic framework such as MOF (Metal Organic Framework), or a metal-based material using palladium or a palladium alloy as a hydrogen permeable material.
  • MOF Metal Organic Framework
  • reagents examples include methyltris(methylethylketoxime)silane, vinyltris(methylethylketoxime)silane, aminoethylaminopropyltrimethoxysilane, ⁇ -aminopropyltriethoxysilane, octamethylcyclotetrasiloxane, cyclic siloxane ester, polydimethylsiloxane, etc.
  • a polymer obtained by polymerizing one type of monomer a polymer obtained by polymerizing two or more types of monomers, or a solution containing a commercially available mixture may be contacted.
  • the TSE series manufactured by Momentive Performance Materials, Inc. silicone resin, silicone oligomer, and silicone emulsion manufactured by Shin-Etsu Silicone Co., Ltd. may be used.
  • the spiral-type composite membrane module for gas separation of the present invention is a composite membrane module for gas separation in which the composite membrane for gas separation of the present invention described above, the feed-side flow path material, and the permeate-side flow path material are wrapped around a central tube that accumulates the permeating gas, and will be described in detail below.
  • FIG. 2 is a partially exploded perspective view of the spiral-type composite membrane module for gas separation (50).
  • the spiral-type composite membrane module for gas separation (50) includes a central tube (56), a composite membrane for gas separation (51), a feed-side flow path material (57), and a permeate-side flow path material (58).
  • the central tube (56) is a hollow cylindrical member with a through hole formed on the side.
  • the material of the central tube (56) may be any material that does not deteriorate depending on the pressure, temperature, or type of gas on the supply side during use of the module.
  • G1 indicates the mixed gas
  • G2 indicates the permeated gas
  • G3 indicates the concentrated gas.
  • the composite membrane for gas separation (51) is as described above.
  • the composite membrane for gas separation (51) is superimposed on a feed-side passage material (57) and a permeate-side passage material (58) and is spirally wound around a central tube (56).
  • a single spiral module can be equipped with multiple composite membranes for gas separation (51).
  • the spiral-type composite membrane module for gas separation (50) has a roughly cylindrical appearance with its major axis aligned along the longitudinal direction of the central tube (56).
  • the gas separation composite membranes (51) are stacked so that the coating layer sides (supply side) face each other and the porous support layer or substrate sides (permeation side) face each other.
  • a supply-side flow passage material (57) is inserted between the surfaces of the gas separation composite membrane (51) on the separation functional layer side, and a permeation-side flow passage material (58) is inserted between the surfaces on the permeation side.
  • the supply side flow path is open at both longitudinal ends of the central tube (56).
  • a supply side inlet is provided at one end of the spiral-type composite gas separation membrane module (50), and a supply side outlet is provided at the other end.
  • the supply side flow path is sealed at the end on the inner side in the winding direction, i.e., the end on the central tube side. The seal is formed by folding the composite gas separation membrane, gluing the composite gas separation membrane with a hot melt or chemical adhesive, or fusing the composite gas separation membranes together using a laser, etc.
  • the feed side flow passage material (57) and the permeate side flow passage material (58) are spacers that secure a flow passage between the composite membranes for gas separation.
  • the permeate side flow passage material and the feed side flow passage material may be the same material or different materials.
  • the permeate side flow passage material and the feed side flow passage material are collectively referred to as "flow passage material”.
  • the flow path material may be a porous sheet such as a net, nonwoven fabric, woven fabric, knitted fabric, or film.
  • One or both sides of the sheet may be provided with protrusions made of resin or the like.
  • protrusions may be directly attached to the composite membrane for gas separation, and these protrusions may be used as the flow path material.
  • the shape of the protrusions may be dots, curved, or linear. If the protrusions are curved or linear, the flow of gas can be controlled along the shape.
  • the composition of the protrusions need only be such that they do not deteriorate depending on the pressure, temperature, or type of gas supplied during use.
  • the flow path material is preferably made of a thermoplastic resin.
  • the thermoplastic resin is preferably polyester, nylon, polyphenylene sulfide, polyethylene, polypropylene, polysulfone, polyethersulfone, ABS (acrylonitrile-butadiene-styrene) resin, or a UV-curable resin.
  • the thickness of at least one of the feed side flow path material and the permeation side flow path material, and preferably both, is preferably 1000 ⁇ m or less, more preferably 700 ⁇ m or less, and particularly preferably 400 ⁇ m or less.
  • the above-mentioned composite membrane for gas separation is capable of selectively permeating gases with small molecular diameters, such as hydrogen, helium, water vapor, and ammonia, and is applied to a gas separation system.
  • the gas separation system includes the following steps. (1) A step of supplying a mixed gas containing gas A as a permeable component and gas B as a non-permeable component to one side of a composite membrane for gas separation. (2) A step of obtaining a gas having a molar ratio of gas A/gas B greater than that of the mixed gas from the other surface of the composite gas separation membrane.
  • this separation system makes it possible to obtain a permeable gas with a reduced concentration of gas B from a mixture of gases A and B by taking advantage of the difference in the permeability of the gas separation composite membrane to gas A and to the unwanted component gas B.
  • Gas B is not limited to a specific type, but the mixed gas preferably contains at least one gas selected from the group consisting of oxygen, nitrogen, and methane as gas B.
  • the composite gas separation membrane can efficiently separate gases with small molecular diameters, such as hydrogen, helium, water vapor, and ammonia, due to the large difference in permeability between the permeability of gases with small molecular diameters, such as hydrogen, helium, water vapor, and ammonia, and the permeability of oxygen, nitrogen, and methane.
  • the mixed gas may also contain water vapor.
  • Water vapor adheres to the membrane and causes a decrease in the selective separation of light gases.
  • the composite membrane for gas separation described above exhibits excellent selective gas separation even when the feed gas contains water vapor.
  • the above-mentioned spiral composite membrane module for gas separation can be used.
  • the pressure vessels can be connected in series and/or parallel and can be housed in the pressure vessel for use.
  • the feed gas may be pressurized by a compressor and supplied to the gas separation composite membrane (its element), or the permeate side of the gas separation composite membrane may be depressurized by a pump.
  • multiple elements may be connected in series.
  • either the permeable gas or non-permeable gas of the upstream element may be supplied to the downstream element.
  • the permeable gas or non-permeable gas of the downstream element may be mixed with the supply gas of the upstream element.
  • the permeable gas or non-permeable gas may be supplied to the subsequent element, which may be pressurized by a compressor.
  • the gas supply pressure is not particularly limited, but is preferably 0.1 MPa to 10 MPa.
  • a pressure of 0.1 MPa or more increases the gas permeation rate, and a pressure of 10 MPa or less can prevent the composite gas separation membrane and its element components from being deformed by pressure.
  • the value of "supply side pressure/permeation side pressure” is also not particularly limited, but is preferably 1.01 to 100,000, more preferably 1.10 to 1,000, and particularly preferably 1.50 to 100.
  • a value of "supply side pressure/permeation side pressure" of 1.01 or more can increase the gas permeation rate, and a value of 100,000 or less can reduce the power costs of increasing the pressure on the supply side and reducing the pressure on the permeation side.
  • the gas supply temperature is not particularly limited, but is preferably 0°C to 200°C, and more preferably 15°C to 180°C.
  • a temperature of 15°C or higher provides good gas permeability, while a temperature of 180°C or lower prevents thermal deformation of the components that make up the gas separation composite membrane element.
  • the composite membrane for gas separation of the present invention has excellent separation performance and can be suitably used for, for example, separating hydrogen gas from a mixed gas containing hydrogen and nitrogen, etc., separating hydrogen gas from a mixed gas containing hydrogen and oxygen, nitrogen, ammonia, etc., separating helium from a mixed gas containing helium and oxygen, nitrogen, etc., purifying helium and hydrogen, etc.
  • Porous Support Membrane Unless otherwise specified, the temperature conditions are room temperature (25° C.). A 16 wt% solution of polysulfone (PSf) in dimethylformamide (DMF) was cast to a thickness of 200 ⁇ m at 25° C. on a polyester nonwoven fabric (air permeability 2.0 cc/cm 2 /sec) made of long fibers as a substrate, and the substrate was immediately immersed in pure water and left for 5 minutes to form a porous support layer. In this way, a porous support membrane having a substrate and a porous support layer was produced.
  • PSf polysulfone
  • DMF dimethylformamide
  • TMC trimesoyl chloride
  • TMC trimesoyl chloride
  • Composite separation membrane R The porous support membrane obtained in A was immersed in a 2.0 wt % m-phenylenediamine (m-PDA) aqueous solution for 2 minutes. The porous support membrane was slowly pulled up vertically, and excess aqueous solution was removed from the surface of the porous support layer by blowing nitrogen from an air nozzle.
  • m-PDA m-phenylenediamine
  • TMC trimesoyl chloride
  • Composite separation membrane S The porous support membrane obtained in A was immersed in a 4.0 wt % m-phenylenediamine (m-PDA) aqueous solution for 2 minutes. The porous support membrane was slowly pulled up vertically, and excess aqueous solution was removed from the surface of the porous support layer by blowing nitrogen from an air nozzle.
  • m-PDA m-phenylenediamine
  • TMC trimesoyl chloride
  • TMC trimesoyl chloride
  • the permeation rate Q of the permeated gas was calculated by the following formula, and the gas permeability was determined by the arithmetic mean when five arbitrary points were taken and measured for the same membrane. Then, the selectivity was calculated as the ratio of the permeation rates of the gases of each component.
  • STP means standard conditions.
  • Q [gas permeation flow rate ( m3 ⁇ STP)]/[membrane area ( m2 ) ⁇ time (s) ⁇ pressure difference (Pa)]
  • a separation membrane was held between the supply cell and the permeation cell of a test cell having a supply cell and a permeation cell.
  • H 2 O was used as a condensable gas
  • helium was used as a non-condensable gas.
  • a total of 21 helium permeation rates were measured at a measurement temperature of 40° C. and a relative humidity of 0% to 95% at intervals of about 5%. In the measurement results, the value closer to 20% of the two points sandwiching a relative humidity of 20% was taken as the helium permeation rate at 20%, and the value closer to 90% of the two points sandwiching a relative humidity of 90% was taken as the helium permeation rate at 90%.
  • the supply side was set to 190 kPa and the permeation side to 100 kPa, the flow rate was measured using a flow meter, and the helium permeability was calculated.
  • Helium permeability at each humidity was determined as the arithmetic average of measurements taken at three random points on the same membrane.
  • the test sample was measured with a barium difluoride scintillation counter using a photomultiplier tube at a total count of 5 million using a thin film positron annihilation lifetime measurement device equipped with a positron beam generator (this device is described in detail in, for example, Radiation Physics and C Helium mistry, 58,603, Pergamon (2000)) at a beam intensity of 1 keV, room temperature, and vacuum, and analyzed by POSI TRONFIT. From the average positron annihilation lifetime ⁇ of the fourth component obtained by analysis, the average pore diameter Rc was calculated by Equation 3, and Rf [nm] was calculated by Equation 4. Rc and Rf were determined by the arithmetic mean of measurements taken at five arbitrary points on the same film.
  • TOF SIMS 5 ION TOF
  • the Si - peak intensity of the separation membrane was measured at intervals of 2.5 nm or less, and the average Si - peak intensity in the region from the coating layer side surface to a depth of 0 to 50 nm was calculated.
  • the Si - peak intensity was determined as the arithmetic mean of measurements taken at five arbitrary points on the same membrane.
  • the coating layer thickness was measured at three points, the center, the right end, and the left end of the image, and the coating layer thickness in the cross-sectional image obtained was calculated by the arithmetic mean of the three points.
  • the same procedure was carried out for five slice samples, and three visual fields were observed for each sample, and the coating layer thickness was determined by the arithmetic mean of a total of 15 data points.
  • the sample was sliced in the cross-sectional direction using the focused ion beam (FIB) method and observed using an analytical electron microscope (JEOL JEM-F200).
  • Element mapping was performed at an acceleration voltage of 200 kV using an energy dispersive X-ray spectroscopy (EDX) detector (JEOL JED2300T 100 mm2 silicon drift (SDD) type) at a 200 kV acceleration voltage.
  • EDX energy dispersive X-ray spectroscopy
  • SDD silicon drift
  • the contact angle was measured according to ISO 19403-1 (2017) by dropping 3.0 ⁇ L of distilled water onto the separation functional layer side of the composite membrane for gas separation, and measuring the contact angle (the angle between the tangent of the droplet and the solid surface) 1 second after the water droplet was dropped.
  • the contact angle 1 second after the pure water landed on the surface of the coating layer was defined as X, and the contact angle 30 seconds later was defined as Y, giving the Y/X value.
  • the support layer thickness was obtained by subtracting the coating layer thickness obtained in G above and the thickness of the substrate alone from the thickness of the gas separation composite membrane after the coating layer was formed.
  • the thickness of the gas separation composite membrane was measured using a PEACOCK digital thickness gauge manufactured by Ozaki Seisakusho Co., Ltd. 20 points were measured in the width direction, and the average value was calculated.
  • the coating layer, functional layer, and support layer of the gas separation composite membrane were peeled off from the substrate, and the thickness of the substrate was measured in the same manner.
  • Support layer thickness ( ⁇ m) composite membrane thickness for gas separation ( ⁇ m) - substrate thickness ( ⁇ m) - coating layer thickness ( ⁇ m)
  • the sample was transferred to a grid for TEM observation, and the sample was prepared so that the separation functional layer could be observed from the side that was in contact with the support layer.
  • the prepared sample was photographed using a field emission transmission electron microscope (Hitachi High-Tech HF5000) under the condition of an acceleration voltage of 200 kV, and a STEM image with a magnification of 100,000 was obtained.
  • the obtained image was then analyzed with image processing software to calculate the pore size.
  • Example 1 The composite separation membrane P obtained in B. was cut into a circle with a membrane area of 25 cm2 .
  • TSE389 (manufactured by Momentive Performance Materials) was dissolved in hexane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a 16 wt% TSE389 hexane solution. 1 mL of the solution was dropped onto the surface of the separation functional layer, and spin-coated at a speed of 1000 rpm for 30 seconds to form a coating layer.
  • the composite membrane for gas separation was obtained by air-drying at 25°C for 12 hours or more. The obtained composite membrane for gas separation was evaluated, and the results were as shown in Table 1.
  • Example 2 A composite membrane for gas separation was produced by forming a coating layer of polydimethylsiloxane by carrying out the same treatment as in Example 1, except that a 5.0 wt % solution of TSE389 (manufactured by Momentive Performance Materials, Inc.) was used. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 3 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 1, except that the composite separation membrane was designated as Q and the coating solution was a 0.8 wt% hexane solution of KBM602 (manufactured by Shin-Etsu Silicone Co., Ltd.). The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 4 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 3, except that the coating solution was a 1.5 wt % hexane solution of TSE382 (manufactured by Momentive Performance Materials, Inc.). The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 5 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 3, except that the coating solution was a 6.0 wt% hexane solution of TSE387 (manufactured by Momentive Performance Materials, Inc.). The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 6 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 3, except that the coating solution was a 4.0 wt% hexane solution of TSE387. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 7 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 3, except that the coating solution was a hexane solution of 8.0 wt% TSE322 (manufactured by Momentive Performance Materials, Inc.). The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 8 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 6, except that the composite separation membrane was R. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 1.
  • Example 9 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 6, except that the composite separation membrane was S. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 10 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 9, except that a polyester short fiber nonwoven fabric (air permeability 1.0 cc/ cm2 /sec) was used instead of the long fiber nonwoven fabric when forming the support membrane.
  • the composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 11 A composite membrane for gas separation was produced by forming a coating layer mainly composed of polymethylpentene by carrying out the same process as in Example 6, except that the composite separation membrane was designated as T and polymethylpentene was used instead of TSE387. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 12 A composite membrane for gas separation was produced by forming a coating layer mainly composed of polymethylpentene by carrying out the same process as in Example 11, except that the composite separation membrane was P. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 13 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 6, except that silicone oligomer KR-510 (manufactured by Shin-Etsu Silicone Co., Ltd.) was used as the coating solution. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 14 After dropping 2 mL of the coating solution, a film was placed on the membrane and held for 10 minutes, and then the same process as in Example 6 was carried out except for spin coating to form a coating layer mainly composed of silicone, thereby producing a composite membrane for gas separation.
  • the composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 15 After dropping 2 mL of the coating solution, a film was placed on the membrane and held for 2 minutes, and then the same process as in Example 6 was carried out except for spin coating to form a coating layer mainly composed of silicone, thereby producing a composite membrane for gas separation.
  • the composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 2.
  • Example 16 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone by carrying out the same process as in Example 6, except that the composite separation membrane was T. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 3.
  • Example 17 A composite membrane for gas separation was produced by forming a coating layer mainly composed of poly(1-trimethylsilyl-1-propyne) by carrying out the same process as in Example 16, except that poly(1-trimethylsilyl-1-propyne) was used instead of polydimethylsiloxane.
  • the composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 3.
  • Example 18 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone through the same process as in Example 9, except that the clearance was adjusted during the formation of the support membrane and the support layer thickness was set to 18 ⁇ m. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 4.
  • Example 19 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone through the same process as in Example 9, except that the clearance was adjusted during the formation of the support membrane and the support layer thickness was set to 25 ⁇ m. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 4.
  • Example 20 A composite membrane for gas separation was produced by forming a coating layer mainly composed of silicone through the same process as in Example 9, except that the clearance was adjusted during the formation of the support membrane and the support layer thickness was set to 55 ⁇ m. The composite membrane for gas separation thus obtained was evaluated, and the results are shown in Table 4.
  • Comparative Example 5 The composite separation membrane T was evaluated as a composite membrane for gas separation without forming a coating layer, and the results are shown in Table 5. Since it does not have a coating layer, permeation through the coarse pores was not suppressed, and when nanoperm porometry analysis was performed, the helium permeability at a relative humidity of 90% was 88% of the helium permeability at a relative humidity of 20%, and the selectivity could not be sufficiently improved. The results of Comparative Examples 1 to 5 are shown in Table 5.
  • Example 6 A composite membrane for gas separation was prepared in the same manner as in Example 11, except that polyethersulfone was used instead of polymethylpentene and N-methyl-2-pyrrolidone was used instead of hexane.
  • the obtained composite membrane for gas separation was evaluated, and the results are shown in Table 6. Because the average pore diameter Rc of the coating layer was small and the gas permeability of the coating layer was low, the helium permeability at 25°C was less than 1.0 nmol/m 2 /s/Pa, and the hydrogen permeability was also low.
  • Comparative Example 7 A composite membrane for gas separation was prepared in the same manner as in Comparative Example 6, except that the polyethersulfone was 0.4 wt%. The obtained composite membrane for gas separation was evaluated, and the results were as shown in Table 6. Although the gas permeability could be increased by reducing the thickness of the coating layer, the coating layer was not sufficiently thick, which resulted in defects, and it was not possible to suppress permeation through the coarse pores at the same time, and the selectivity was not sufficiently improved.
  • Example 8 A composite membrane for gas separation was prepared in the same manner as in Example 1, except that 3 mL of a 25.0 wt % TSE389 hexane solution was dropped onto the porous support membrane obtained in A. The composite membrane for gas separation obtained was evaluated, and the results were as shown in Table 6. Since there was no separation functional layer and no pores that would cause sieving according to the molecular diameter of the gas, the selectivity was reduced.
  • Non-Patent Document 2 in which a polydimethylsiloxane coating layer is applied to the surface of a polyamide composite membrane, has a high ratio of helium permeability to hydrogen permeability of 1.83, and has good selectivity, but has a low hydrogen permeability (Table 4). Also, from the image in Non-Patent Document 2, it can be seen that the coating layer penetrates 192 nm into the support layer.
  • Non-Patent Document 1 which has a polyphenylene oxide coating layer on the surface of a polyamide composite membrane, is presumed to have very good selectivity because the nitrogen and methane permeabilities are very low, but the helium permeability and hydrogen permeability are also presumed to be very low (Table 4). It can also be seen that the coating layer penetrates 444 nm into the support layer.
  • the composite membrane for gas separation of the present invention is suitable for use in separating and purifying a specific gas from a mixed gas.

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PCT/JP2024/013613 2023-04-10 2024-04-02 気体分離用複合膜およびそれを用いた気体分離システム WO2024214595A1 (ja)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5386684A (en) * 1976-11-15 1978-07-31 Monsanto Co Multiicomponent membrane for gas separation
JPH05329346A (ja) * 1992-06-01 1993-12-14 Nitto Denko Corp 複合半透膜
JP2022184754A (ja) * 2021-05-31 2022-12-13 東レ株式会社 気体の分離方法
JP2023178968A (ja) * 2022-06-06 2023-12-18 東レ株式会社 気体分離装置および気体分離方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5386684A (en) * 1976-11-15 1978-07-31 Monsanto Co Multiicomponent membrane for gas separation
JPH05329346A (ja) * 1992-06-01 1993-12-14 Nitto Denko Corp 複合半透膜
JP2022184754A (ja) * 2021-05-31 2022-12-13 東レ株式会社 気体の分離方法
JP2023178968A (ja) * 2022-06-06 2023-12-18 東レ株式会社 気体分離装置および気体分離方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PARK, JAE-SUNG ET AL.: "Gas transport properties of PDMS-coated reverse osmosis membranes", JOURNAL OF MEMBRANE SCIENCE, vol. 604, 2020, pages 118009, XP086149733, DOI: 10.1016/j.memsci.2020.118009 *

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