JP2023144364A - Gas separation membrane, gas separation membrane module, and gas producing method - Google Patents

Abstract

To provide a gas separation membrane having improved selective separability between gases with small molecular diameters such as hydrogen and helium and other gases.SOLUTION: Provided is a gas separation membrane having a separation functional layer on a porous support layer, in which the average pore radius R3 [nm] of the separation functional layer determined by the positron beam method and the pore diameter dNKP [nm] of the gas separation membrane determined by Formula 2 and the NKP (Normalized-Knudsen-based Permeance) method satisfy Formula 1. (Here, "i" is hydrogen, nitrogen, or methane, "Pi" is the permeability of the gas i at 25°C [nmol/m2/s/Pa], Mi is the molecular weight of the gas i, and dk,i is the dynamic molecular diameter [nm] of the gas i).SELECTED DRAWING: Figure 1

Description

The present invention relates to a gas separation membrane capable of selectively separating at least one component in a gas mixture, a gas separation membrane module, and a method for producing gas using the same.

In recent years, hydrogen has attracted attention as a clean energy source. Hydrogen is obtained by reforming and gasifying fossil fuels such as natural gas and coal, and removing unnecessary gases from a mixed gas containing hydrogen and carbon dioxide as main components. Hydrogen is also obtained by decomposing water using electricity or a photocatalyst, and extracting only hydrogen from a mixed gas containing hydrogen, oxygen, and water vapor. Hydrogen is also used in the Haber-Bosch process to synthesize ammonia. This is a method of synthesizing ammonia by reacting hydrogen and nitrogen at high temperature and pressure, but it requires a process to separate and recover unreacted hydrogen and nitrogen at the production plant.

Pressure swing adsorption (PSA) has been used to separate hydrogen from other gases. However, the problem with the PSA method is the cost involved in regenerating the adsorbent. As a low-cost method of concentrating a specific gas from a mixed gas, membrane separation methods that utilize differences in gas permeability of materials to selectively permeate target gases are attracting attention.

Another area where membrane separation methods are attracting attention is humidity control processes that use membranes that selectively transmit water vapor. Adsorption methods and freezing methods have been used as humidity control processes, but there are issues such as the cost of regenerating the adsorbent and the increased size of the equipment. The membrane separation method is attracting attention as a new humidity control process because it is easy to operate and the equipment can be easily miniaturized.

As a low-cost method of concentrating a specific gas from a mixed gas, membrane separation methods that utilize differences in gas permeability of materials to selectively permeate target gases are attracting attention.

Patent Document 1 discloses that the functional layer surface of a polyaramid gas separation membrane having a single-layer structure is brought into contact with a non-solvent containing a fluorine-based nonionic surfactant, swollen, and then dried. Techniques for improving He/N2 selectivity have been disclosed.

Patent Document 2 discloses a technique for obtaining a gas separation membrane with fewer defects by impregnating a porous support layer with a semipermeable membrane layer containing an amorphous resin as a main component.

Patent Document 3 discloses that by laminating a second separation membrane with a high content of fluorine atoms on a first separation layer that has a selective separation property of gases, the selective separation property of carbon dioxide/methane is high and impurities are separated. A technique has been disclosed that allows a film to be obtained with little performance deterioration due to gas exposure.

Japanese Patent Application Publication No. 3-186327 JP2017-74580A JP2019-162565A

However, the conventional techniques, that is, the techniques described in Patent Documents 1 to 3, cannot efficiently increase the permeation resistance of other gases such as carbon dioxide, oxygen, nitrogen, and methane; There is a problem in that high permeability for gases with small molecular diameters such as ammonia and high selective separation from other gases such as carbon dioxide, oxygen, nitrogen, and methane cannot be achieved at the same time.

In particular, in the techniques described in Patent Documents 2 and 3, the selective separation performance is insufficient because the permeation resistance for other gases such as carbon dioxide, oxygen, nitrogen, and methane is insufficient. In the technique described in Patent Document 1, although high selective separation performance can be obtained by the described treatment, there is a drawback that permeability is significantly reduced.

The present invention has been made in view of the above-mentioned conventional circumstances, and aims to provide high permeability to gases with small molecular diameters, such as hydrogen, helium, water vapor, and ammonia, and to other gases such as carbon dioxide, oxygen, nitrogen, and methane. The purpose of the present invention is to provide a gas separation membrane that can achieve both high selective separation from gas.

The present inventors conducted extensive studies to solve the above problems, and as a result, succeeded in significantly improving the performance of gas separation membranes, particularly the selective separation performance, and completed the present invention.

That is, the gist of the present invention is the following configuration.
(1)
A gas separation membrane having at least a porous support layer and a separation functional layer on the porous support layer,
The average pore radius R ₃ [nm] of the separation functional layer determined by the positron beam method, and the pore diameter d of the gas separation membrane determined by Equation 2 and the NKP (Normalized-Knudsen-based Permeance) method. A gas separation membrane in which _NKP [nm] satisfies formula 1.

(Here, "i" is either H ₂ , N ₂ , or CH ₄ , "P _i " is the permeability of gas i at 25°C [nmol/m ₂ /s/Pa], and P _He is the permeability of He gas at 25°C [nmol/m ₂ /s/Pa], M _i is the molecular weight of gas i, M _He is the molecular weight of He gas, and d _k,i is the dynamic coefficient of gas i. is the molecular diameter [nm], and d _k,He is the dynamic molecular diameter [nm] of He gas.)
(2)
The gas separation membrane according to (1) above, which contains 0.10% by weight or more of a component that can be eluted in water or hexane (hereinafter referred to as eluted component) in 100% by weight of the gas separation membrane.
(3)
The eluted component contains a surfactant or an organosilicon compound,
The gas separation membrane according to (2) above, which contains 0.05% by weight or more of the surfactant or the organosilicon compound in 100% by weight of the gas separation membrane.
(4)
The gas separation membrane according to (3) above, wherein the surfactant has a molecular weight of 100 or more and 500 or less.
(5)
The gas separation membrane according to any one of (1) to (4) above, wherein the average pore radius R ₃ [nm] is 0.20 or more and 0.50 or less.
(6)
The gas separation membrane according to any one of (1) to (5) above, wherein the pore diameter d _NKP [nm] is 0.30 or more and 0.60 or less.
(7)
The sum of the peak intensities of surfactants or organosilicon compounds in a region of 0 to 50 nm in depth from the surface of the functional layer detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is X1, and the functional layer is (1) to (1), wherein X1/X2 is 0.01 or more and 0.5 or less, where X2 is the sum of the peak intensities of surfactants or organosilicon compounds in a region from the surface to a depth of 1000 to 1050 nm. 6) The gas separation membrane according to any one of 6).
(8)
A gas separation membrane in which the gas separation membrane according to any one of (1) to (7) above, the supply side channel material, and the permeate side channel material are wrapped around a central pipe that accumulates permeated gas. module.
(9)
A gas production method using the gas separation membrane module according to (8) above,
A gas production method including the following steps 1 and 2.

Step 1: A step of supplying a mixed gas containing gas A, which is at least one of hydrogen, helium, water vapor, and ammonia, and a gas B other than the gas A, to one surface of the gas separation membrane.

Step 2: A step of obtaining a gas having a larger molar ratio of gas A/gas B than the mixed gas from the other side of the gas separation membrane.

According to the present invention, it is possible to provide a gas separation membrane, a gas separation membrane module, and a gas production method using the same, which have high selective separation properties for gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia. can.

FIG. 1 is an example of a cross-sectional view of a gas separation membrane. FIG. 2 is a partially exploded perspective view showing one embodiment of the gas separation membrane module of the present invention.

1. Gas Separation Membrane The gas separation membrane of the present invention is a gas separation membrane having at least a porous support layer and a separation functional layer on the porous support layer, wherein the separation functional layer is determined by a positron beam method. Gas separation in which the average pore radius R ₃ [nm] and the pore diameter d _NKP [nm] of the gas separation membrane, which is determined by Equation 2 and the NKP (Normalized-Knudsen-based Permeance) method, satisfy Equation 1. It is a membrane.

(Here, "i" is either H ₂ , N ₂ , or CH ₄ , "P _i " is the permeability of gas i at 25°C [nmol/m ₂ /s/Pa], and P _He is the permeability of He gas at 25°C [nmol/m ₂ /s/Pa], M _i is the molecular weight of gas i, M _He is the molecular weight of He gas, and d _k,i is the dynamic coefficient of gas i. is the molecular diameter [nm], and d _k,He is the dynamic molecular diameter [nm] of He gas.)
As shown in FIG. 1, the gas separation membrane (51) of this embodiment includes at least a porous support layer (52) and a separation functional layer (53) on the porous support layer. Moreover, it may have a base material (54).

The separation functional layer means a component having the highest gas selective separation property among the components constituting the gas separation membrane.

Further, the gas separation membrane of the present invention is not limited to a specific shape, and may take a flat membrane shape, a hollow fiber shape, or other shapes.

The positron beam method is one of the positron annihilation lifetime measurement methods, and measures the time from when a positron enters a sample until it annihilates, and from the annihilation time, the size of the vacancy, approximately 0.1 to 10 nm, is determined. This is a method for non-destructively evaluating information regarding the number density and further the distribution of pore size. This method differs from the usual positron annihilation method in that it uses a positron beam instead of a radioactive isotope ( ²² Na) as a positron source, and makes it possible to measure thin films with a thickness of several hundred nanometers. The average pore radius R ₃ [nm] of the separation functional layer is determined from the positron annihilation life τ when positrons are implanted at an intensity of 1 keV from the surface having the separation functional layer.

The average pore radius R ₃ [nm] of the separation functional layer of the gas separation membrane of the present invention is determined from the following equation 3 based on the positron extinction lifetime τ described above. Equation 3 shows the relationship when it is assumed that orthopositronium (o-Ps) exists in holes with an average hole radius R ₃ in an electronic layer with a thickness ΔR, and ΔR is empirically 0.166 nm. (The details are described in Nakanishi et al., Journal of Polymer Science, Part B: Polymer Physics, Vol. 27, p. 1419, John Wiley & Sons, Inc. (1989)).

The average pore radius R ₃ [nm] is preferably 0.20 or more and 0.50 or less, more preferably 0.22 or more and 0.40 or less, and even more preferably 0.24 or more and 0.32 or less. When the average pore radius R ₃ [nm] is 0.20 or more, it is possible to increase the permeability of the gas that you want to pass through the membrane, and when it is 0.50 or less, it is possible to increase the permeability of the gas that you want to pass through the membrane. It becomes possible to express selective separation properties.

The pore diameter d _NKP [nm] of the gas separation membrane of the present invention is determined from the following equation (2) based on the NKP (Normalized-Knudsen-based Permeance) method. The NKP method measures the membrane permeation flow rate of many types of non-condensable gases with different molecular diameters, plots the gas dynamic molecular diameter on the horizontal axis and the membrane permeation flow rate on the vertical axis, and calculates the curve using (Equation 2). This is a method of calculating the pore diameter d _NKP [nm] by fitting. In this specification, four types of gases, He, H ₂ , N ₂ , and CH ₄ are used as non-condensable gases (Lie Meng et al., Journal of Membrane Science, Vol. 496, p. 211-218, Department of The details are described in Chemical Engineering, Graduate School of Engineering, Hiroshima University (2015)).

The pore diameter d _NKP [nm] is preferably 0.30 or more and 0.60 or less, more preferably 0.32 or more and 0.50 or less, and even more preferably 0.35 or more and 0.40 or less. When the pore diameter d _NKP [nm] is 0.30 or more, it can be used as a membrane that permeates gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia, and when it is 0.60 or less, it can be used as a membrane that permeates gas molecules. It is possible to exhibit selective separation depending on the diameter.

Generally, the separation functional layer of a gas separation membrane has a pore size distribution. Ideally, it would be ideal to have only suitable pores with an appropriate size pore that has excellent selective separation of the target gas, but in reality, it often has coarse pores with low selective separation. It is important to reduce the contribution of coarse pores.

In a membrane in which the contribution of coarse pores in the separation functional layer is reduced, the pore diameter d _NKP [ calculated by the NKP method with respect to the pore diameter (2R ₃ ) calculated from the average pore radius R ₃ [nm] of the separation functional layer nm] becomes smaller. The pore diameter d _NKP [nm] calculated by the NKP method is 0.40 times or more and 0.90 times or less of the pore diameter (2R ₃ ) calculated from the average pore radius R ₃ [nm] of the separation functional layer. That is, it is preferable that Formula 1 is satisfied, more preferably 0.50 times or more and 0.85 times or less, and even more preferably 0.60 times or more and 0.80 times or less. When "pore diameter d _NKP / pore diameter (2R ₃ )" is 0.40 times or more, it is possible to increase the permeation of gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia, and "pore diameter d _NKP /pore diameter (2R ₃ )" is 0.80 times or less, the selective separation property can be increased.

Methods for reducing the contribution of coarse pores in the separation functional layer, that is, methods for satisfying formula 1, include coating the surface of the separation functional layer, adsorption of foreign substances to the functional layer and/or porous support layer, and methods for manufacturing. Examples include increasing the density of the support membrane through improvements and consolidating the porous support layer through pressurization. Using these methods, it is important to provide gas permeation resistance to locations other than the separation functional layer in order to reduce the contribution of coarse pores.

Since coarse pores have low gas permeation resistance, gas permeability is extremely high. On the other hand, proper pores have much higher gas permeation resistance and lower gas permeability than coarse pores. When gas permeation resistance is applied to locations other than the separation functional layer using the method described above, gas permeation through coarse pores is greatly suppressed, but the effect on permeation through appropriate pores is small, so gas permeation through coarse pores is It becomes possible to reduce the contribution of gas permeation, and the selective separation performance of the entire membrane improves.

(1-1) Base material The gas separation membrane of the present invention may have a base material. The base material does not need to have the ability to separate and permeate gases selectively, but only needs to be able to provide strength to the entire gas separation membrane by supporting the separation functional layer.

The resin constituting the base material is not particularly limited, but includes polyester polymers, polyamide polymers, polyolefin polymers, polysulfide polymers, and mixtures and copolymers thereof. Among these, polyester polymers and polysulfide polymers with high mechanical strength and thermal stability are particularly preferred as resins constituting the base material.

The form of the base material is not particularly limited, but nonwoven fabrics such as long fiber nonwoven fabrics and short fiber nonwoven fabrics or woven or knitted fabrics are preferred.

The base material preferably has an air permeability of 0.5 cc/cm ² /sec or more and 5.0 cc/cm ² /sec or less. When the air flow rate of the base material is within the above range, the polymer solution that will become the porous support layer is impregnated into the base material, improving the adhesion with the base material and improving the physical stability of the porous support layer. can be increased.

The thickness of the base material is preferably within the range of 10 to 200 μm, more preferably within the range of 30 to 120 μm. In the present invention, the thickness refers to the average value of the thickness of 20 points measured at 20 μm intervals in the film surface direction on a cross section in the thickness direction (a cross section perpendicular to the film surface direction) of a film-like sample, unless otherwise specified. be.

(1-2) Porous support layer The gas separation membrane of the present invention has a porous support layer. The porous support layer may or may not have selective gas separation properties. The porous support layer may be disposed on the base material, and the base material and the porous support layer on the base material are collectively referred to as a support film.

The size and distribution of the pores in the porous support layer are not particularly limited; It may gradually increase in size over the surface.

The material of the porous support layer is not particularly limited, but examples include homopolymers such as polysulfone, polyethersulfone, polyamide, polyaramid, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide; Alternatively, copolymers can be used alone or in blends. Among these, homopolymers or copolymers such as polysulfone, polyethersulfone, and polyaramid are particularly preferred as materials for the porous support layer because they have high chemical, mechanical, and thermal stability. The porous support layer preferably contains 50% by mass or more and 100% by mass or less of these materials in 100% by mass of the porous support layer.

The thickness of the base material and the porous support layer influences the strength of the gas separation membrane and the packing density when it is made into a gas separation membrane module. In order to obtain sufficient mechanical strength and packing density, the total thickness of the base material and the porous support layer, that is, the thickness of the support film consisting of the base material and the porous support layer, must be 30 μm or more and 300 μm or less. The thickness is preferably 50 μm or more and 250 μm or less. Further, the thickness of the porous support layer is preferably 10 μm or more and 200 μm or less.

(1-3) Separation functional layer The gas separation membrane of the present invention has a separation functional layer.

The separation functional layer preferably contains crosslinked polyamide as a main component. The crosslinked polyamide constituting the separation functional layer can be formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional halide on a porous support layer.

In the present invention, "containing crosslinked polyamide as a main component" means that crosslinked polyamide accounts for 60% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more and 100% by weight or less in 100% by weight of the separation functional layer. means.

The crosslinked polyamide in the separation functional layer may be a fully aromatic polyamide, a fully aliphatic polyamide, or a combination of aromatic and aliphatic portions; It is preferable that there be.

The polyfunctional amine is specifically a polyfunctional aromatic amine or a polyfunctional aliphatic amine. A polyfunctional aromatic amine has two or more amino groups of at least one of a primary amino group and a secondary amino group in one molecule, and at least one of the amino groups is a primary amino group. means an aromatic amine which is a class amino group. Moreover, the polyfunctional aliphatic amine means an aliphatic amine having two or more amino groups of at least one of a primary amino group and a secondary amino group in one molecule.

For example, polyfunctional aromatic amines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m- Polyfunctional aromatic amines such as diaminopyridine and p-diaminopyridine in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions; 1,3,5-triamino Benzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, 2,4-diaminothioanisole, 1,3-diaminothioanisole, 1, 3-Diamino-5-(dimethylphosphino)benzene, (3,5-diaminophenyl)dimethylphosphine oxide, (2,4-diaminophenyl)dimethylphosphine oxide, 1,3-diamino-5-(methylsulfonyl)benzene , 1,3-diamino-4-(methylsulfonyl)benzene, 1,3-diamino-5-nitrosobenzene, 1,3-diamino-4-nitrosobenzene, 1,3-diamino-5-(hydroxyamino)benzene , 1,3-diamino-4-(hydroxyamino)benzene and the like.

In addition, polyfunctional aliphatic amines include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, piperazine, 2-methylpiperazine, 2,4-dimethylpiperazine, 2,5 -dimethylpiperazine, 2,6-dimethylpiperazine, and the like.

These polyfunctional amines may be used alone or in combination of two or more.

Moreover, the polyfunctional acid halide specifically refers to a polyfunctional aromatic acid halide or a polyfunctional aliphatic acid halide.

The polyfunctional acid halide is also expressed as a polyfunctional carboxylic acid derivative, and refers to an acid halide having at least two halogenated carbonyl groups in one molecule. For example, examples of trifunctional acid halides include trimesic acid chloride, and examples of difunctional acid halides include biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid dichloride, and oxalyl chloride. Examples include chloride.

Considering the reactivity with polyfunctional amines, the polyfunctional acid halide is preferably a polyfunctional acid chloride, and considering the selective separation property and heat resistance of the gas separation membrane, A polyfunctional acid chloride having 2 to 4 carbonyl chloride groups is preferred.

Among these, trimesic acid chloride is more preferred from the viewpoint of ease of availability and handling. These polyfunctional acid halides may be used alone or in combination of two or more.

Moreover, the polycondensation reaction specifically refers to interfacial polycondensation.

Here, it is preferable that at least one of the polyfunctional amine and the polyfunctional acid halide contains a trifunctional or higher functional compound.

The gas separation membrane of the present invention preferably has a membrane permeation flux of water of 0.01 (m ³ /m ² /day) or more and 0.50 (m ³ /m ² /day) or less, and preferably 0.02 (m ³ /m ² /day) or more and 0.30 (m ³ /m ² /day) or less, more preferably 0.05 (m ³ /m ² /day) or more and 0.20 (m ³ /m 2 /day) or more. m ² /day) or less is more preferable. The permeation flux of water is 0.50 (m ³ /m ² /day) or less, which suppresses coarse pores and defects in the membrane surface and allows gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia to be It is possible to express higher selective separation against. When the permeation flux of water is 0.01 (m ³ /m ² /day) or more, the permeability to gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia can be increased.

(1-4) Components eluted in water or hexane The gas separation membrane of the present invention preferably contains 0.10% by weight or more of components eluted in water or hexane in 100% by weight of the gas separation membrane. The content is more preferably .50% by weight or more, and even more preferably 1.00% by weight or more. By containing 0.10% by weight or more of components eluted in water or hexane in 100% by weight of the gas separation membrane, sufficient gas permeation resistance can be imparted to the gas separation membrane to improve selective separation performance. can. In order not to significantly reduce gas permeability, the content of components eluted in water or hexane in 100% by weight of the gas separation membrane is preferably 20.0% by weight or less.

In this specification, the gas separation membrane containing 0.10% by weight or more of a component eluted in water or hexane (hereinafter referred to as eluted component) means that the gas separation membrane is This is synonymous with the fact that when cleaning the separation membrane, the cleaning solution after cleaning contains 0.10 parts by weight or more of eluted components based on 100 parts by weight of the gas separation membrane before cleaning.

(A) Into a 500 mL beaker according to ISO 3819 (established in 1985), put 3 g of a gas separation membrane cut into squares of 1 cm on each side, use 300 g of water or hexane at a temperature of 25 °C as a cleaning liquid, and use a beaker with a diameter of 8 mm and a total length of 40 mm. Stir at 200 rpm for 1 hour using a polytetrafluoroethylene stirrer.

The following method is used to quantify the eluted components.

After performing the cleaning method (A), the cleaning liquid is filtered using one type of general filter paper described in the JIS standard. 100 g of the filtered cleaning solution is collected in an eggplant flask, and volatile components are removed from the cleaning solution by freeze-drying. The weight of the eluted component is calculated as W2 - W1, where the weight of the eggplant flask is W1, and the combined weight of the eggplant flask and residue after freeze-drying is W2, and at this time, the eluted component is 100 parts by weight per 100 parts by weight of the gas separation membrane. It is calculated as x (W2-W1) parts by weight.

Since the gas separation membrane contains the eluted component, in addition to the gas permeation resistance that the separation functional layer originally has, gas permeation resistance due to the presence of the eluted component is imparted. As a result, gas permeation through the coarse pores with low gas permeation resistance and low gas selective separation performance is suppressed, and the gas selective separation performance of the entire membrane is improved.

The separation functional layer has a small number of regions with extremely high gas permeability, such as coarse pores and defects. In such a region, the contribution of separation by molecular sieves is small, and the selective separation of gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia is low. It is important to reduce the contribution of regions with low selective separation such as large pores and defects in improving the selective separation of the membrane as a whole.

When the porous support layer contains an eluted component, the presence of the eluted component in the voids of the porous support layer increases the gas permeation resistance of the porous support layer. The high gas permeation resistance of the porous support layer makes it possible to suppress gas permeation through the coarse pores and defect areas of the separation functional layer. Although it greatly suppresses the permeation of carbon dioxide, oxygen, nitrogen, methane, etc., it has little effect on the permeation of gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia, so it can greatly improve selective separation. .

If the separation functional layer contains eluted components, gas permeation through the large pores and defects can be prevented by forming a coating layer of the eluted components on top of the separation functional layer, or by filling the large pores and defects with amphiphilic molecules. can be suppressed. Although it greatly suppresses the permeation of carbon dioxide, oxygen, nitrogen, methane, etc., it has little effect on the permeation of gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia, so it can greatly improve selective separation. .

In the gas separation membrane of the present invention, the eluted component contains a surfactant or an organosilicon compound, and the surfactant or the organosilicon compound may be contained in an amount of 0.05% by weight or more in 100% by weight of the gas separation membrane. The content is preferably 0.30% by weight or more, more preferably 0.50% by weight or more. In order not to significantly reduce gas permeability, the content of the surfactant or organosilicon compound in 100% by weight of the gas separation membrane is preferably 10.0% by weight or less.

A surfactant suitable as an elution component is a molecule that has both a hydrophilic group with high affinity for water and a hydrophobic group with high affinity with oil in one molecule.

According to the 2nd edition of the Standard Chemical Terminology Dictionary (Maruzen Publishing), a hydrophilic group refers to a "polar atomic group that interacts strongly with water," and "ionic hydrophilic groups include sulfate groups, sulfonic acid groups, etc." The nonionic hydrophilic groups include hydroxyl groups, oxyethylene groups, and amide groups.''

Furthermore, according to the 2nd edition of the Standard Chemical Terminology Dictionary (Maruzen Publishing), hydrophobic groups are described as "functional groups that do not mix with water and have low affinity for water," and are the opposite of hydrophilic groups. It means a nonpolar atomic group. Examples of hydrophobic groups include linear or branched aliphatic groups, or fluoroaliphatic groups in which some or all of their hydrogens are replaced by fluorine.

Specific names of surfactants include phosphatidylcholine, sphingomyelin, sodium lauryl sulfate, sodium hexadecyl sulfate, sodium laurylbenzenesulfonate, lauryltrimethylammonium chloride, cetyltrimethylammonium brolide, didecyldimethylammonium chloride, nonafluoro- Examples include 1-butane sulfate, lithium heptafluoro-1-octane sulfate, stearyldimethylaminoacetic acid betaine, potassium lauroylglutamate, stearyl alcohol, sorbitan monooleate, sorbitan trioleate, and the like.

Further, the surfactant preferably has a molecular weight of 100 or more and 500 or less, more preferably 200 or more and 400 or less. Specific examples include lauryltrimethylammonium chloride, cetyltrimethylammonium brolide, didecyldimethylammonium chloride, lithium heptafluoro-1-octane sulfate, stearyldimethylaminoacetic acid betaine, and potassium lauroylglutamate.

The surfactant in the eluted component can be identified and quantified by analyzing the washing solution obtained by the washing method (A) using LC-MS/MS (liquid chromatography tandem mass spectrometry). .

An organosilicon compound suitable as an eluent component refers to a compound in which one or more carbon atoms of an organic compound are replaced with a silicon atom. Examples include silane, which is a silicon compound in which the carbon of a saturated hydrocarbon is replaced with silicon, siloxane having a siloxane bond (Si--O--Si), and polysiloxane, which is a polymer made by linking siloxane bonds.

The organosilicon compound in the eluted component can be identified and quantified by analyzing the washing solution obtained by the washing method (A) by ¹ H-NMR.

The gas separation membrane of the present invention has a peak intensity of a surfactant or an organosilicon compound detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) at a depth of 0 to 50 nm from the surface of the separation functional layer. X1 is the sum of the peak intensities of the surfactant or organosilicon compound in a region of 1000 to 1050 nm in depth from the surface of the separation functional layer, and X1/X2 is 0.01 or more and 0.5 or less. It is preferably 0.03 or more and 0.3 or less, and even more preferably 0.05 or more and 0.2 or less. When X1/X2 is 0.5 or less, the surfactant or organosilicon compound is unevenly distributed in the porous support layer, effectively increasing permeation resistance and reducing the contribution of permeation from coarse pores. . When X1/X2 is 0.01 or more, it becomes possible to suppress permeation from the coarse pores due to penetration of the surfactant or organosilicon compound into the coarse pores.

Examples of means for adjusting X1/X2 to a suitable range include a method of applying a solution containing a surfactant or an organosilicon compound from the porous support layer side or the base material side, and a method of bringing it into contact.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) uses pulsed primary ions to irradiate a sample surface placed in an ultra-high vacuum, and collects secondary ions sputtered and emitted from the sample surface. This is an analysis method that obtains the mass distribution of secondary ions from the distribution of flight times. By detecting the secondary ion intensity while sputtering progresses, it is possible to know the concentration distribution of the detected element in the depth direction of the sample.

In this specification, peak intensities X1 and X2 are both peak intensities when focusing on surfactants or organosilicon compounds that are the same component. If we focus on the surfactant as X1 without considering combinations such as X1 being a surfactant and X2 being an organosilicon compound, or combinations such as X1 and X2 being different surfactants or organosilicon compounds, the same as X2. When paying attention to the surfactant and paying attention to an organosilicon compound as X1, pay attention to the same organosilicon compound as X2. Specifically, combinations such as X1 and X2 are both sodium hexadecyl sulfate, and X1 and X2 are both polydimethylsiloxane are allowed, but there are also combinations in which X1 is sodium hexadecyl sulfate and X2 is polydimethylsiloxane, and X1 is sodium hexadecyl sulfate. A combination in which X2 is sodium lauryl sulfate is not permitted.

2. Method for Manufacturing a Gas Separation Membrane Next, the method for manufacturing a gas separation membrane of the present invention will be described by giving an example.

(2-1) Formation of support membrane A laminate of a base material and a porous support layer is referred to as a support membrane, and this case will be explained. In the examples listed below, the method for forming the support film includes the step of preparing a polymer solution by dissolving the polymer that is a component of the porous support layer in a good solvent for that polymer, and applying the polymer solution to the base material. and wet coagulating the polymer by immersing the polymer solution in a coagulation bath. The solidified polymer corresponds to the porous support layer.

When at least one of polysulfone and polyethersulfone is used as the polymer, a polymer solution is obtained by dissolving it in N,N-dimethylformamide (DMF). Water is preferably used as the coagulation bath.

Aramid, which is an example of a polymer, can be obtained by solution polymerization or interfacial polymerization using acid chloride and diamine as monomers. In solution polymerization, an aprotic organic polar solvent such as DMF, N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), etc. can be used as a solvent. When polyamide is produced using acid chloride and diamine as monomers, hydrogen chloride is produced as a by-product. When neutralizing hydrogen chloride, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate, and lithium carbonate, and organic neutralizing agents such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine, and diethanolamine are used. used.

(2-2) Formation of separation functional layer (polyamide polycondensation)
Next, the process of forming the separation functional layer will be explained. The separation functional layer is formed by forming polyamide on the support membrane through interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide.

More specifically, the step of 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 the step (a), a step of applying an organic solvent solution containing a polyfunctional acid halide to the porous support layer.

In step (a), the concentration of the polyfunctional amine in the aqueous polyfunctional amine solution is preferably in the range of 0.1% by weight or more and 20% by weight or less, more preferably 0.5% by weight or more and 15% by weight. It is within the following range. When the concentration of the polyfunctional amine is within this range, sufficient selective separation 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. good. 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 nonpolar solvent.

It is preferable to apply the polyfunctional amine aqueous solution to the porous support layer uniformly and continuously. Coating refers to contacting a porous support layer with a polyfunctional amine aqueous solution, and specifically, coating the surface of a porous support layer with a polyfunctional amine aqueous solution, or coating a polyfunctional amine aqueous solution on a support membrane. immersion in water, etc. Coatings include dropping, spraying, roller coating, and the like.

The time from applying the polyfunctional amine aqueous solution on the porous support layer to draining it or applying the polyfunctional acid halide (that is, the contact time between the porous support layer and the polyfunctional amine aqueous solution) is , preferably 1 second or more and 10 minutes or less, and more preferably 10 seconds or more and 3 minutes or less.

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. Locations where droplets remain may become membrane defects and reduce separation performance, but this can be prevented by draining. A method can be used, such as a method in which the support film after applying the polyfunctional amine aqueous solution is held vertically to allow excess aqueous solution to flow down naturally, or a method in which a stream of nitrogen or the like is sprayed from an air nozzle to forcefully drain the liquid.

In step (b), the concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01% by weight or more and 10% by weight or less, and 0.02% by weight or more and 2.0% by weight. More preferably, it is within the following range. This is because by setting the content to 0.01% by weight or more, a sufficient reaction rate can be obtained, and by setting the content to 10% by weight or less, the occurrence of side reactions can be suppressed.

The organic solvent is preferably one that is immiscible with water, dissolves the polyfunctional acid halide, does not destroy the support film, and is inert to the polyfunctional amine compound and polyfunctional acid halide. It's fine as long as it exists. Preferred examples include hydrocarbon compounds such as n-hexane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, isooctane, isodecane, isododecane, or mixtures thereof. .

The method for applying the polyfunctional acid halide solution to the porous support layer may be performed in the same manner 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 the solution by coating rather than by dipping.

At this time, the porous support layer in contact with the organic solvent solution of the polyfunctional acid halide may be heated. The heat treatment temperature is 50°C or higher and 180°C or lower, preferably 60°C or higher and 160°C or lower. By heating at 60° C. or higher, the reduction in reactivity due to monomer consumption in the interfacial polymerization reaction can be compensated for by the effect of promoting the reaction due to heat. By heating at 160° C. or lower, it is possible to prevent the solvent from completely volatilizing and the reaction efficiency from significantly decreasing. Moreover, it is preferable that the heat treatment time of each time is 5 seconds or more and 600 seconds or less. By setting the time to 5 seconds or more, a reaction promotion effect can be obtained, and by setting the time to 600 seconds or less, complete volatilization of the solvent can be prevented.

Further, a polyfunctional halide may be added during the interfacial polycondensation reaction to promote consumption of the polyfunctional amine.

(chemical modification)
The obtained gas separation membrane may be chemically treated to chemically convert the terminal amino groups or terminal carboxyl groups of the polyamide.

For example, by introducing a nitro group structure that has low affinity for carbon dioxide, it is possible to improve the selective separation of carbon dioxide from gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia. Specifically, it is preferable to bring a water-soluble oxidizing agent into contact with the gas separation membrane, and examples of the water-soluble oxidizing agent include hydrogen peroxide, peracetic acid, sodium perborate, potassium peroxymonosulfate, etc. can.

The means for reacting the water-soluble oxidizing agent with the polyamide is not particularly limited, but for example, a method of immersing the polyamide gas separation membrane in an aqueous solution containing the water-soluble oxidizing agent is preferred.

The concentration of the water-soluble oxidizing agent is preferably 0.1% to 10% by weight, more preferably 0.5% to 3% by weight.

The pH of the aqueous solution containing the water-soluble oxidizing agent is not particularly limited as long as it can sufficiently exhibit the oxidizing power of the oxidizing agent, but it is preferably in the range of 1.5 to 7.0.

As for the chemical treatment method, it is preferable to use an aqueous solution containing a water-soluble oxidizing agent at a temperature of 10° C. or more and 100° C. or less, more preferably a temperature of 20° C. or more and 80° C. or less. By setting the temperature to 20°C or higher, the efficiency of the reaction can be improved, and by setting the temperature to 80°C or lower, decomposition of the oxidizing agent can be suppressed.

The contact time between the aqueous solution containing a water-soluble oxidizing agent and the polyamide is preferably 30 seconds to 1 day, and more preferably 1 minute to 30 minutes in consideration of both practicality and reaction efficiency.

After the polyamide comes into contact with an aqueous solution containing a water-soluble oxidizing agent, the polyamide is brought into contact with a reducing agent in order to stop the oxidation reaction. Here, the reducing agent is not particularly limited as long as it causes a redox reaction with the oxidizing agent used, but sodium bisulfite, sodium sulfite, or sodium thiosulfate is preferably used because of ease of acquisition and handling. preferable. Further, they are preferably used as a 0.01 to 1% by weight aqueous solution.

The contact time between the reducing agent and the polyamide is sufficient as long as it can stop the oxidation reaction, and is usually preferably from 1 minute to 20 minutes.

After contact between the reducing agent and the polyamide, it is preferable to rinse the polyamide gas separation membrane with water to wash away any remaining reducing agent.

The presence of the functional group derived from the nitro group can be determined by analyzing the polyamide using X-ray photoelectron spectroscopy (XPS). Specifically, "Journal of Polymer Science", Vol. 26, 559-572 (1988) and "Journal of the Adhesion Society of Japan", Vol. 27, No. 4 (1991), using X-ray photoelectron spectroscopy (XPS).

The N1s peak obtained by XPS is caused by the inner shell electrons of nitrogen atoms. Since the N1s peak is considered to be composed of a component derived from NC and a component derived from NOx (x≧2), the N1s peak is divided into two components, and the component derived from NC is around 400 eV. In addition, since components derived from NOx (x≧2) appear around 406 eV, the presence of nitro groups can be detected.

In addition, by chemically treating at least one of the aromatic rings and nitrogen atoms contained in the obtained polyamide and introducing fluorine atoms, it has an affinity with gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia. It is possible to improve the selective separation of gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia.

Specifically, it is preferable to bring the fluorinating agent into contact with a gas separation membrane having polyamide, and the fluorinating agent is 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2. 2] Octane bis(tetrafluoroborate) (Selectfluor(R)), N-fluorobenzenesulfonimide, 1-fluoropyridinium tetrafluoroborate, and the like.

The method for reacting the fluorinating agent and polyamide is not particularly limited, but for example, a method of immersing a gas separation membrane containing polyamide in an aqueous solution containing a fluorinating agent (hereinafter sometimes referred to as "fluorinating agent aqueous solution") is a method. preferable.

The concentration of the fluorinating agent in the fluorinating agent aqueous solution is preferably 0.01% to 10% by weight, more preferably 0.1% to 1% by weight.

As for the chemical treatment method, it is desirable to treat the fluorinating agent aqueous solution at a temperature of 10°C or more and 100°C or less, more preferably 20°C or more and 80°C or less. By setting the temperature to 10°C or higher, the efficiency of the reaction can be improved, and by setting the temperature to 100°C or lower, decomposition of the fluorinating agent can be suppressed.

The contact time between the fluorinating agent aqueous solution and the gas separation membrane containing polyamide is preferably 30 seconds to 1 day, and more preferably 1 minute to 30 minutes in consideration of both practicality and reaction efficiency.

The presence of the fluorine atoms can be determined by analyzing the polyamide using X-ray photoelectron spectroscopy (XPS). Specifically, "Journal of Polymer Science", Vol. 26, 559-572 (1988) and "Journal of the Adhesion Society of Japan", Vol. 27, No. 4 (1991), using X-ray photoelectron spectroscopy (XPS).

(2-3) Introduction of eluted components In order to introduce eluted components into the gas separation membrane of the present invention, it is preferable to bring a solution or emulsion containing the eluted components into contact with the gas separation membrane. The contacting method is not particularly limited, and may be applied to the separation functional layer side and/or the porous support layer side, dipping, or other known methods.

Examples of the solvent used when introducing the eluted component into the gas separation membrane include water, ethanol, benzene, and hexane, and water is preferable because the gas separation membrane is less likely to deteriorate during the immersion treatment. When water is used as the solvent, the pH of the aqueous solution is preferably in the range of 3 to 11 in order to minimize deterioration of the gas separation membrane.

Preferably, the eluting component contains a surfactant or an organosilicon compound.

When the gas separation membrane is immersed in a solution containing eluted components, the immersion time is preferably 1 minute to 3 hours, and preferably 5 minutes to 2 hours in consideration of the amount of eluted components adsorbed.

After contact with a solution containing an eluted component, it is preferable to drain excess solution to prevent crystal precipitation of the eluted component.

After draining the solution, in order to sufficiently dry the gas separation membrane, it is preferable to air-dry it at 25° C. and a humidity of 70% or less for 12 hours or more.

3. Gas separation membrane module (3-1) Overview,
When the gas separation membrane of the present invention takes a flat membrane shape, it can be applied to a spiral type module or a stack type module, and when it takes a hollow fiber shape, it can be applied to a hollow fiber type module. Describe the module.

The gas separation membrane module of the present invention is a gas separation membrane in which the gas separation membrane of the present invention, the supply side channel material, and the permeate side channel material are wrapped around a central pipe that accumulates permeated gas. This is a module, and the details of this will be explained below.

Note that FIG. 2 is a partially exploded perspective view of the spiral type module (50). As shown in FIG. 2, the spiral type module (50) includes a central pipe (55), a gas separation membrane (51), a supply side channel material (56), and a permeation side channel material (57).

(3-2) Central tube The central tube (55) is a hollow cylindrical member with a through hole formed on the side surface. The material of the center tube (55) may be any material as long as it does not deteriorate depending on the pressure, temperature, or type of gas on the supply side when the module is used.

(3-3) Gas separation membrane The gas separation membrane (51) is as described above. The gas separation membrane (51) is overlapped with the supply side channel material (56) and the permeate side channel material (57), and is spirally wound around the central tube (55).

One spiral-wound module can include multiple gas separation membranes (51). By including these wound members, the spiral module (50) has a generally cylindrical appearance with its long axis in the longitudinal direction of the central tube (55).

The gas separation membranes (51) are stacked so that the surfaces on the separation functional layer side (supply side) face each other and the surfaces on the permeation side face each other.

A supply side channel material (56) is inserted between the surfaces of the gas separation membrane (51) on the separation functional layer side, and a permeate side channel material (57) is inserted between the surfaces on the permeation side.

The supply side flow path is open at both longitudinal ends of the central tube (55). That is, a supply side inlet is provided at one end of the spiral type module (50), and a supply side outlet is provided at the other end. On the other hand, the supply side flow path is sealed at the inner end in the winding direction, that is, at the end on the center tube side. The seal is formed by folding the gas separation membranes, adhering the gas separation membranes together using hot melt or chemical adhesives, or fusing the gas separation membranes together using a laser or the like.

(3-4) Channel material (overview)
The supply side channel material (56) and the permeation side channel material (57) are spacers that secure a channel between the gas separation membranes. The permeation side channel material and the supply side channel material may be the same member or may be different members. Hereinafter, the permeation side channel material and the supply side channel material will be collectively referred to as "channel material."

Examples of the channel material include porous sheets such as nets, nonwoven fabrics, woven fabrics, knitted fabrics, and films. Protrusions made of resin or the like may be provided on one or both sides of the sheet. Alternatively, the protrusions may be directly fixed to the gas separation membrane, and the protrusions may be used as channel materials.

When the channel material has a sheet and a protrusion, the shape of the protrusion may be a dot, a curved line, or a straight line. If the shape is curved or straight, the gas flow can be controlled along the shape. The composition of the protrusion may be one that does not deteriorate depending on the pressure, temperature, or type of gas on the supply side during use.

(material)
The channel material is preferably made of thermoplastic resin. From the perspective of suppressing damage to the gas separation membrane, the thermoplastic resin must be polyester, nylon, polyphenylene sulfide, polyethylene, polypropylene, polysulfone, polyether sulfone, ABS (acrylonitrile-butadiene-styrene) resin, or UV curable resin. is preferred.

(thickness)
The thickness of at least one, preferably both, of the supply-side channel material and the permeate-side channel material is preferably 1000 μm or less, more preferably 700 μm or less, and particularly preferably 400 μm or less. By making the channel material thinner in this way, its rigidity against bending is reduced and it becomes less likely to break. Furthermore, by making the channel material thinner, the area of the gas separation membrane that can be filled can be increased while maintaining the volume of the gas separation membrane module.

4. Gas Production Method The gas separation membrane of the present invention is capable of selectively permeating gases with small molecular diameters such as hydrogen, helium, water vapor, and ammonia, and is applied to gas production methods.

The gas production method according to this embodiment includes the following steps.

Step 1: A step of supplying a mixed gas containing gas A, which is at least one of hydrogen, helium, water vapor, and ammonia, and a gas B other than gas A, to one surface of the gas separation membrane of the present invention.

Step 2: Step of obtaining a gas having a larger molar ratio of gas A/gas B than the mixed gas from the other side of the gas separation membrane of the present invention.

In other words, according to this manufacturing method, by utilizing the difference in the permeability of the gas separation membrane to gas A and the permeability to gas B, which is an unnecessary component, gas B is extracted from a mixed gas of gas A and gas B. A permeate gas having a reduced concentration of can be obtained.

Although the gas B is not limited to a specific type, it is preferable that the mixed gas contains, as the gas B, at least one of carbon dioxide, oxygen, nitrogen, and methane, for example. This is because gas separation membranes can efficiently separate hydrogen and helium due to the large difference in permeability between hydrogen and helium and carbon dioxide, oxygen, nitrogen, and methane.

In the gas production method of the present invention, the above-described spiral type gas separation membrane module can be used. Moreover, in the gas production method of the present invention, the pressure vessels can be connected in series and/or in parallel, and can be used by being accommodated in the pressure vessel.

In step 1, the supply gas may be pressurized by a compressor and supplied to the gas separation membrane (its module), or the pressure on the permeate side of the gas separation membrane for gas separation may be reduced by a pump.

Also, a plurality of modules may be connected in series. If multiple modules are used, the downstream module may be supplied with either the permeate gas or the non-permeate gas of the upstream module. Also, the permeate or non-permeate gas of the downstream module may be mixed with the feed gas of the upstream module. The permeate gas or the non-permeate gas may be compressed in a subsequent module, which may be compressed by a compressor.

The gas supply pressure is not particularly limited, but is preferably 0.1 MPa to 10 MPa. Setting the pressure to 0.1 MPa or more increases the gas permeation rate, and setting the pressure to 10 MPa or less can prevent pressure deformation of the gas separation membrane and its module members. The value of "pressure on the supply side/pressure on the permeate side" is also not particularly limited, but is preferably 2 to 20. By setting the value of "supply side pressure/permeation side pressure" to 2 or more, the gas permeation rate can be increased, and by setting it to 20 or less, the power of the supply side compressor or permeation side pump can be increased. Costs can be controlled.

The gas supply temperature is not particularly limited, but is preferably 0°C to 200°C, more preferably 15°C to 180°C. By setting the temperature to 15°C or higher, good gas permeability can be obtained, and by setting the temperature to 180°C or lower, thermal deformation of the members constituting the gas separation membrane module can be prevented. By using the above gas separation membrane, it is possible to supply gas at a temperature of 80°C or higher, 90°C or higher, or 100°C or higher.

5. Applications The gas separation membrane module of the present invention has excellent separation performance and is suitable for, for example, hydrogen gas separation from a mixed gas containing hydrogen and nitrogen, and hydrogen gas separation from a mixed gas containing hydrogen and oxygen. be.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way.

Unless otherwise specified, temperature conditions are room temperature (25° C.).

A. Preparation of gas separation membrane (Gas separation membrane X)
A 18% by weight solution of polysulfone (PSf) in dimethylformamide (DMF) was cast to a thickness of 200 μm at 25° C. on a polyester nonwoven fabric (airflow rate 2.0 cc/cm ² /sec) as a base material, and immediately A porous support layer was formed by immersing it in pure water and leaving it for 5 minutes. In this way, a support membrane having a base material and a porous support layer was produced.

The support membrane was immersed in a 6.0% by weight m-phenylenediamine (m-PDA) aqueous solution for 2 minutes. The support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the porous support layer.

Next, an n-decane solution containing 0.16% by weight of trimesic acid chloride (TMC) was applied so that the surface of the porous support layer was completely wetted, and after standing at 25°C for 30 seconds, it was heated at 60°C. It was left still for 100 seconds. Thereafter, in order to remove excess solution from the separation membrane, the separation membrane was held vertically to allow the solution to flow, and then the liquid was drained by blowing air at 25° C. using a sending device to dry the membrane.

(Gas separation membrane Y)
A 15% by weight solution of polysulfone (PSf) in dimethylformamide (DMF) was cast to a thickness of 200 μm at 25° C. on a polyester nonwoven fabric (airflow rate 2.0 cc/cm ² /sec) as a base material, and immediately A porous support layer was formed by immersing it in pure water and leaving it for 5 minutes. In this way, a support membrane having a base material and a porous support layer was produced.

The support membrane was immersed in a 2.0% by weight m-phenylenediamine (m-PDA) aqueous solution for 2 minutes. The support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the porous support layer.

Subsequently, an n-decane solution containing 0.04% by weight of trimesic acid chloride (TMC) was applied so that the surface of the porous support layer was completely wetted, and allowed to stand at 25° C. for 30 seconds. Thereafter, in order to remove excess solution from the separation membrane, the separation membrane was held vertically to allow the solution to flow, and then the liquid was drained by blowing air at 25° C. using a sending device to dry the membrane.

B. Gas permeability measurement (calculation of pore diameter d _NKP [nm] of gas separation membrane)
A separation membrane was held between the supply side cell and the permeation side cell of a test cell having a supply side cell and a permeation side cell. Using He, H ₂ , O ₂ , and N ₂ as measurement gases, the pressure change on the permeation side of each gas per unit time was measured at a measurement temperature of 25°C in accordance with the pressure sensor method of JIS K7126-1 (2006). was measured. Here, the supply side was set to 100 kPa, the permeation side was set to 0 kPa, and the pressure difference between the supply side and the permeation side was 100 kPa. Subsequently, the permeation rate Q of the permeated gas was calculated using the following formula, and the separation coefficient α was calculated as the ratio of the gas permeation rates of each component. Note that STP means standard conditions.

Q = [Gas permeation flow rate (×10 ⁻⁶ cm ³・STP)]/[Membrane area (cm ² )×Time (s)×Pressure difference (cmHg)
In addition, the dynamic molecular diameters of He, H ₂ , N ₂ , and CH ₄ are plotted on the horizontal axis, and the membrane permeation flow rates of He, H ₂ , N ₂ , and CH ₄ are plotted on the vertical axis, and the left and right sides of (Equation 2) are plotted. The pore diameter d _NKP [nm] that minimizes the sum of squared errors was calculated.

C. Measurement of average pore radius R ₃ [nm] of separation functional layer by positron beam method The positron annihilation lifetime measurement of the separation functional layer in each example was performed using the positron beam method as follows. That is, the separation functional layer was dried at room temperature under reduced pressure and cut into 1.5 cm x 1.5 cm square pieces to prepare test samples. A thin film compatible positron annihilation lifetime measuring device equipped with a positron beam generator (this device is described in detail in, for example, Radiation Physics and Chemistry, 58, 603, Pergamon (2000)) was used at a beam intensity of 1 keV and at room temperature. The test samples were measured under vacuum with a barium difluoride scintillation counter using a photomultiplier tube at a total count of 5 million, and analyzed using POSI TRONFIT. From the average positron annihilation lifetime τ of the fourth component obtained by the analysis, the average hole radius R ₃ [nm] was calculated using Equation 3.

(Example 1)
After applying an aqueous solution containing 0.5% by weight of polyoxyethylene sorbitan trioleate (Fuji Film Wako Pure Chemical Industries, Ltd.) to the surface of the separation functional layer of gas separation membrane X so that the surface is completely wet, a liquid film is applied. It was covered with a polyethylene film and left to stand for 1 hour. After removing the film, the gas separation membrane was held vertically to allow the aqueous solution to flow in order to remove excess solution from the gas separation membrane. Finally, a gas separation membrane was obtained by air drying at 25° C. for 12 hours or more.

Table 1 summarizes the performance evaluation of this gas separation membrane.

(Example 2)
A gas separation membrane was obtained by performing the same operation as in the example except that sodium lauryl sulfate (Fuji Film Wako Pure Chemical Industries, Ltd.) was used as the aqueous solution.

Table 1 summarizes the performance evaluation of this gas separation membrane.

(Example 3)
A gas separation membrane was obtained by performing the same operation as in Example except that the aqueous solution was an emulsion type silicone (manufactured by Momentive Performance Materials).

Table 1 summarizes the performance evaluation of this gas separation membrane.

(Example 4)
A gas separation membrane was obtained by performing the same operation as in Example 2 except that the aqueous solution was brought into contact with the surface of the base material.

Table 1 summarizes the performance evaluation of this gas separation membrane.

(Example 5)
A gas separation membrane was obtained by performing the same operation as in Example 3 except that the aqueous solution was brought into contact with the surface of the base material.

Table 1 summarizes the performance evaluation of this gas separation membrane.

(Example 6)
A gas separation membrane was obtained by performing the same operation as in Example 1 except that Y was used as the gas separation membrane.

Table 2 summarizes the performance evaluation of this gas separation membrane.

(Example 7)
A gas separation membrane was obtained by performing the same operation as in Example 2 except that Y was used as the gas separation membrane.

Table 2 summarizes the performance evaluation of this gas separation membrane.

(Example 8)
A gas separation membrane was obtained by performing the same operation as in Example 3 except that Y was used as the gas separation membrane.

Table 2 summarizes the performance evaluation of this gas separation membrane.

(Example 9)
A gas separation membrane was obtained by performing the same operation as in Example 4 except that Y was used as the gas separation membrane.

Table 2 summarizes the performance evaluation of this gas separation membrane.

(Example 10)
A gas separation membrane was obtained by performing the same operation as in Example 5 except that Y was used as the gas separation membrane.

Table 2 summarizes the performance evaluation of this gas separation membrane.

(Comparative example 1)
Gas separation membrane X was not subjected to any treatment and its performance was evaluated as it was.

Performance evaluation is summarized in Table 3.

(Comparative example 2)
A gas separation membrane was obtained by performing the same operation as in Example 1 except that polyethylene glycol (PEG) having a molecular weight of 4000 was used as the aqueous solution.

Table 3 summarizes the performance evaluation of this gas separation membrane.

(Comparative example 3)
Gas separation membrane Y was not subjected to any treatment and its performance was evaluated as it was.

Performance evaluation is summarized in Table 3.

(Comparative example 4)
A gas separation membrane was obtained by carrying out the same operation as in Example 6 except that polyethylene glycol (PEG) having a molecular weight of 4000 was used as the aqueous solution.

Table 3 summarizes the performance evaluation of this gas separation membrane.

The gas separation membrane module for gas separation of the present invention is suitably used for separating and purifying a specific gas from a mixed gas.

50: Spiral type module 51: Gas separation membrane 52: Support membrane 53: Separation functional layer 54: Base material 55: Center pipe 56: Supply side channel material 57: Permeate side channel material G1: Mixed gas G2: Permeated gas G3 : Concentrated gas

Claims (9)

A gas separation membrane having at least a porous support layer and a separation functional layer on the porous support layer,
The average pore radius R ₃ [nm] of the separation functional layer determined by the positron beam method, and the pore diameter d of the gas separation membrane determined by Equation 2 and the NKP (Normalized-Knudsen-based Permeance) method. A gas separation membrane in which _NKP [nm] satisfies formula 1.

(Here, "i" is either H ₂ , N ₂ , or CH ₄ , "P _i " is the permeability of gas i at 25°C [nmol/m ₂ /s/Pa], and P _He is the permeability of He gas at 25°C [nmol/m ₂ /s/Pa], M _i is the molecular weight of gas i, M _He is the molecular weight of He gas, and d _k,i is the dynamic coefficient of gas i. is the molecular diameter [nm], and d _k,He is the dynamic molecular diameter [nm] of He gas.) The gas separation membrane according to claim 1, wherein the gas separation membrane contains 0.10% by weight or more of a component eluted in water or hexane (hereinafter referred to as eluted component) in 100% by weight of the gas separation membrane. The eluted component contains a surfactant or an organosilicon compound,
The gas separation membrane according to claim 2, wherein the surfactant or the organosilicon compound is contained in an amount of 0.05% by weight or more in 100% by weight of the gas separation membrane. The gas separation membrane according to claim 3, wherein the surfactant has a molecular weight of 100 or more and 500 or less. The gas separation membrane according to any one of claims 1 to 4, wherein the average pore radius R ₃ [nm] is 0.20 or more and 0.50 or less. The gas separation membrane according to any one of claims 1 to 5, wherein the pore diameter d _NKP [nm] is 0.30 or more and 0.60 or less. The sum of the peak intensities of surfactants or organosilicon compounds in a region from 0 to 50 nm in depth from the surface of the separation functional layer detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is X1, and the separation is Claims 1 to 3, wherein X1/X2 is 0.01 or more and 0.5 or less, where X2 is the total peak intensity of the surfactant or organosilicon compound in a region at a depth of 1000 to 1050 nm from the surface of the functional layer. 6. The gas separation membrane according to any one of 6. A gas separation membrane module, wherein the gas separation membrane according to any one of claims 1 to 7, the supply side channel material, and the permeate side channel material are wrapped around a central pipe that collects permeated gas. A gas production method using the gas separation membrane module according to claim 8,
A gas production method including the following steps 1 and 2.
Step 1: A step of supplying a mixed gas containing gas A, which is at least one of hydrogen, helium, water vapor, and ammonia, and a gas B other than the gas A, to one surface of the gas separation membrane.
Step 2: A step of obtaining a gas having a larger molar ratio of gas A/gas B than the mixed gas from the other side of the gas separation membrane.

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