JP7816751B2 - Gas separation membrane, gas separation membrane module, manufacturing method thereof, and gas separation method using same - Google Patents

Description

The present invention relates to gas separation membranes and gas separation membrane modules, as well as methods for producing the same. Furthermore, the present invention relates to gas separation methods using gas separation membranes and gas separation membrane modules.

In recent years, Japan has been undertaking various initiatives to achieve the Sustainable Development Goals (SDGs), with one of the main targets being the reduction of greenhouse gas emissions to virtually zero by 2025, thereby achieving so-called carbon neutrality. Greenhouse gases are gases that have increased primarily due to human activity, and examples include carbon dioxide, methane, chlorofluorocarbons, and carbon monoxide. Of these, carbon dioxide is considered to have the greatest impact on global warming. Therefore, if it were possible to separate carbon dioxide from the various mixed gases emitted by industry and control its release so that it does not enter the atmosphere, it would be possible to make a significant contribution to achieving carbon neutrality.

On the other hand, materials made of polymer compounds are known to have unique gas permeabilities. A mixed gas containing desired gas components can be passed through a membrane made of a specific polymer compound to separate and obtain the desired gas. Such membranes are called gas separation membranes, and attempts are being made to use them industrially. In particular, exhaust gases generated from thermal power plants, steelworks blast furnaces, various factories, etc. contain large amounts of carbon dioxide, making these facilities large-scale sources of carbon dioxide. Therefore, the separation and recovery of carbon dioxide from exhaust gases has been actively studied both inside and outside these facilities. In this case, separation of desired gas components using gas separation membranes can be performed with a simple operation and requires a relatively small amount of energy, and therefore has attracted much attention as a means to solve environmental problems.
Patent Document 1 discloses a gas separation membrane having a support including a porous layer, a polyimide layer, and a cellulose layer in this order, with the cellulose layer using a specific cellulose compound. Patent Document 1 discloses a gas separation membrane laminated in the order of a protective layer, a cellulose layer, a polyimide layer, a resin layer, and a support, with the protective layer preferably being made of a silicone resin, polyimide, cellulose resin, polyethylene oxide, or the like, the support having a porous layer on the polyimide layer side, and the use of a specific cellulose layer and a specific polyimide layer makes it possible to obtain a gas separation membrane with high separation selectivity.
Patent Document 2 discloses a gas separation membrane composed of a polymer membrane containing a water-soluble polymer and an amine compound selected from the group consisting of specific amine compounds and polyethyleneamines. Patent Document 2 discloses that carbon dioxide can be separated from other gases with high selectivity by adsorbing and desorbing carbon dioxide with the specific amine compound.

JP 2018-12089 A Japanese Patent Application Laid-Open No. 2018-144022

The gas separation membrane of Patent Document 1 is characterized by the selection of a polyimide layer and a specific cellulose layer in consideration of separation selectivity and gas permeability during gas separation. Meanwhile, Patent Document 2 discloses that a polymer membrane containing a specific amine compound or polyethylene polyamine in a water-soluble polymer matrix has gas separation functionality. Patent Documents 1 and 2 do not acknowledge the phenomenon that these gas separation membranes and polymer membranes deteriorate as gas separation is performed using them, and therefore do not address the lifespan of these gas separation membranes or polymer membranes. However, as mentioned above, gas separation membranes are intended for long-term use in facilities such as thermal power plants, steelworks blast furnaces, and various factories, where large amounts of industrially produced mixed exhaust gases containing greenhouse gases may be generated. Therefore, it is important that gas separation membranes combine excellent separation selectivity and permeability as a basic premise, and also possess properties that enable them to be used as long as possible in these facilities.

The inventors focused on the phenomenon that conventional gas separation membranes, such as the gas separation membranes and polymer membranes disclosed in Patent Documents 1 and 2, deteriorate relatively quickly during gas separation. The present invention aims to provide a gas separation membrane and gas separation membrane module that can be used for a long period of time and is easy to maintain by suppressing deterioration of the gas separation membrane, as well as methods for manufacturing these and a gas separation method using a gas separation membrane.

The present invention provides a gas separation membrane having a porous support membrane, a functional layer, and a protective layer, characterized in that the porous support membrane has, on one side thereof, a protective layer containing a crosslinked siloxane or a crosslinked mixture of a siloxane and a polyolefin, and the other side thereof has a functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines.
The water-soluble polymer is preferably at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.
The siloxanes are represented by the following formula (1):
(wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), is preferably a polymer or copolymer having as a constituent unit at least one of the following:
Furthermore, the porous support membrane is preferably a hollow fiber membrane.

Furthermore, the present invention relates to a gas separation method in which a mixed gas containing at least carbon dioxide is brought into contact with one side of the gas separation membrane of the present invention that has the protective layer, carbon dioxide is selectively passed through the gas separation membrane, and carbon dioxide is extracted from the other side that has the functional layer.

The present invention provides a method for producing a gas separation membrane having a porous support membrane, a functional layer, and a protective layer, comprising the steps of: applying a mixture containing siloxanes, optionally a polyolefin, and a crosslinking agent to one surface of the porous support membrane, and heating the mixture to form the protective layer; and then applying an aqueous solution containing water-soluble polymers, at least one amine compound selected from water-soluble alkanolamines, and water to the other surface of the porous support membrane, and drying the mixture to form the functional layer.
The water-soluble polymer is preferably at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.
The siloxanes have the following formula (1):
(wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), is preferably a polymer or copolymer having as a constituent unit at least one of the following:
Furthermore, the porous support membrane is preferably a hollow fiber membrane.

The present invention provides a gas mixture inlet for introducing a gas mixture containing at least carbon dioxide;
a carbon dioxide outlet for discharging the carbon dioxide separated from the mixed gas;
a separated gas outlet for discharging a separated mixed gas from which carbon dioxide has been separated;
The gas separation membrane module is characterized in that one or more gas separation membranes are disposed inside a module container comprising: a hollow fiber membrane; a functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines, disposed on one side of the hollow fiber membrane; and a protective layer containing a crosslinked siloxane or a crosslinked mixture of a siloxane and a polyolefin, disposed on the other side of the hollow fiber membrane.
The water-soluble polymer is preferably at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.
The siloxanes have the following formula (1):
(wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), is preferably a polymer or copolymer having as a constituent unit at least one of the following:

Furthermore, the present invention provides a gas separation membrane module according to the present invention, which includes introducing a mixed gas containing at least carbon dioxide through the mixed gas inlet,
bringing the mixed gas into contact with two surfaces of the gas separation membrane to selectively pass carbon dioxide through the gas separation membrane;
carbon dioxide is removed from one side of the gas separation membrane;
The extracted carbon dioxide is discharged from the carbon dioxide discharge port.
The method for separating carbon dioxide from a mixed gas includes the steps of separating the carbon dioxide from the mixed gas and discharging the separated mixed gas from the separated gas outlet.

The present invention provides a gas mixture inlet for introducing a gas mixture containing at least carbon dioxide;
a carbon dioxide outlet for discharging the carbon dioxide separated from the mixed gas;
a separated gas outlet for discharging a separated mixed gas from which carbon dioxide has been separated;
Inside the module container,
A functional layer is provided on one surface of the hollow fiber membrane,
The method for producing a gas separation membrane module includes disposing one or more hollow fiber membranes inside the module container, applying a mixture containing a siloxane, optionally a polyolefin, and a crosslinking agent to two surfaces of the hollow fiber membranes and heating the mixture to form the protective layer, and then applying an aqueous solution containing water-soluble polymer, at least one amine compound selected from water-soluble alkanolamines, and water to one surface of the hollow fiber membranes and drying the mixture to form the functional layer.
The water-soluble polymer is preferably at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.
The siloxanes have the following formula (1):
(wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), is preferably a polymer or copolymer having as a constituent unit at least one of the following:

The present invention can provide gas separation membranes and gas separation membrane modules that combine high gas separation selectivity and permeability, and have long life with minimal deterioration during gas separation operations.

FIG. 1 shows an example of a process for producing a gas separation membrane of the present invention. FIG. 2 is a diagram showing an example of the gas separation membrane module of the present invention. FIG. 3 is a cross-sectional view of an example of a gas separation membrane used in the present invention. FIG. 4 is a graph showing the change over time in carbon dioxide permeation flux when carbon dioxide is separated from a mixed gas containing 30 ppm of sulfur dioxide (Examples and Comparative Examples). FIG. 5 is a graph showing the change over time in carbon dioxide selectivity when carbon dioxide is separated from a mixed gas containing 30 ppm of sulfur dioxide (Examples and Comparative Examples). FIG. 6 is a graph showing the change over time in carbon dioxide permeation flux when carbon dioxide is separated from a mixed gas containing 300 ppm of sulfur dioxide (Examples and Comparative Examples). FIG. 7 is a graph showing the change over time in carbon dioxide selectivity when carbon dioxide is separated from a mixed gas containing 300 ppm of sulfur dioxide (Examples and Comparative Examples).

Embodiments of the present invention will be described in more detail below, but the present invention is not limited to the following embodiments.

One embodiment of the present invention is a gas separation membrane having a porous support membrane, a functional layer, and a protective layer. The gas separation membrane is characterized in that one surface of the porous support membrane has a protective layer containing a crosslinked siloxane or a crosslinked mixture of a siloxane and a polyolefin, and the other surface of the porous support membrane has a functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines.

In this embodiment, a gas separation membrane refers to a membrane intended to extract a desired gas component from a gas mixture containing at least two gas components. In this specification, a gas separation membrane is also sometimes referred to as a gas separation membrane, and the two terms are used interchangeably. A gas separation membrane may have the function of filtering (separating) solids or liquids from a gas mixture containing the solids or liquids. The gas separation membrane of this embodiment has at least the following three components: a porous support membrane, a functional layer, and a protective layer.

The gas separation membrane of the embodiment includes a porous support membrane as a component. In the embodiment, "porous" refers to a structure having multiple holes (pores), preferably a large number of pores. Porous materials include microporous, mesoporous, and macroporous materials depending on the size of the pores, and any of these materials may be used for the porous support membrane of the embodiment. Any material may be used as the porous material, including activated carbon, zeolite, mesoporous silica, and pumice, as well as natural fibers (cotton, linen, wool, etc.), chemical fibers (polyester, polyolefin, polyamide, acetate, promix, rayon, aramid, polyacrylonitrile, etc.), and other thermoplastic resins (polyvinyl alcohol, polysulfone, polyvinylidene fluoride, etc.). In the embodiment, the porous support membrane is a support member for attaching or supporting the functional layer and protective layer described below. The support membrane refers to a plate-like, hard or soft membrane having a specific area. In this embodiment, the shape of the support membrane is not limited to a plate, and it may be a rolled-up plate, spherical, cylindrical, or other shape, and can be freely formed depending on the use of the gas separation membrane of this embodiment. The support membrane can have a variety of thicknesses ranging from micrometers to millimeters, depending on the use of the gas separation membrane of this embodiment. The thickness of the support membrane is preferably 50 μm to 1 cm, more preferably 100 μm to 5 mm, and particularly preferably 300 μm to 1 mm.

The use of hollow (straw-shaped) hollow fiber membranes with micropores in the wall surface as the porous support membrane is particularly advantageous, as it allows for a larger membrane area per volume. Hollow fiber membranes have two surfaces: an inner surface and an outer surface. In this embodiment, ultrafiltration (UF) hollow fiber membranes and microfiltration (MF) hollow fiber membranes can be used as the porous support membrane. Examples of hollow fiber membrane materials include polyethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, and polyethylene tetrafluoride. Such UF hollow fiber membranes and MF hollow fiber membranes are commercially available.

The gas separation membrane of the embodiment comprises a functional layer and a protective layer as its constituent elements. The functional layer is a constituent element that defines the gas separation membrane of the embodiment. It is a layer that has the function of selectively allowing (or preventing) the permeation of a desired gas from a gas mixture containing the desired gas, thereby separating the desired gas, or conversely, the function of selectively allowing (or preventing) the permeation of an undesired gas (gas separation function). On the other hand, the protective layer is preferably a layer that has the function of preventing or suppressing the permeation of gases that would reduce the gas separation function of the functional layer. A specific gas can reduce the gas separation function of the functional layer in various ways, including the gas structurally deteriorating the functional layer, the gas physically adhering to the surface of the functional layer and preventing contact between the gas mixture and the functional layer, or the gas chemically reacting with a substance constituting the functional layer, thereby losing the gas separation function of the functional layer. In the embodiment, the protective layer is preferably a layer that can prevent or suppress the permeation of gases that would reduce or inactivate the gas separation function of the functional layer. In the gas separation membrane of the embodiment, a protective layer is provided on one surface of the porous support membrane, and a functional layer is provided on the other surface of the porous support membrane. Here, the one surface of the porous support membrane refers to one of the two widest surfaces of the membrane, and the other surface of the porous support membrane refers to the surface opposite the one surface. In the embodiment, it is preferable that the protective layer and the functional layer are not stacked in contact with each other, but are provided on separate surfaces with the porous support membrane interposed between them.

In an embodiment, the protective layer preferably contains a crosslinked siloxane or a mixed crosslinked siloxane and polyolefin. Here, the siloxane refers to a compound having repeating siloxane bonds, and may be an oligomer or a polymer.
Here, the siloxanes are represented by the following formula (1):
(wherein _R1 and _R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group). Examples of such siloxanes include polydimethylsiloxane, polydiphenylsiloxane, polymethyl(3,3,3-trifluoropropyl)siloxane, poly(1-trimethylsilyl-1-propyne), polydi(trifluoropropyl)siloxane, and mixtures thereof. The protective layer contains a crosslinked product of siloxanes obtained by crosslinking these siloxanes. The protective layer may also contain a mixed crosslinked product of siloxanes and, in some cases, a polyolefin. In this specification, the term "crosslinked product of siloxanes" is intended to include a mixed crosslinked product of siloxanes and polyolefin. Polyolefin refers to an oligomer or polymer obtained by polymerizing an olefin or alkene, and examples thereof include polyethylene, polypropylene, poly-1-hexene, poly-1-octene, polyvinyl acetate, poly-4-methyl-1-pentene, as well as mixtures or copolymers thereof.

As mentioned above, the protective layer is preferably a layer that has the function of preventing or suppressing the permeation of gases that degrade or deactivate the function of the functional layer. When a gas mixture containing gases such as sulfur oxides (SOx) and nitrogen oxides (NOx) is separated using a conventional gas separation membrane, the gas separation performance of the functional layer of the gas separation membrane rapidly deteriorates. To prevent or suppress such a deterioration in gas separation function, in this embodiment, a protective layer is provided on the side opposite the functional layer via a porous support membrane. When a mixed gas is passed through the gas separation membrane of this embodiment from the side on which the protective layer is provided, the permeation of gases that degrade the gas separation function of the functional layer (e.g., SOx and NOx) is prevented, thereby preventing these gases from coming into contact with the functional layer. To enable the protective layer to perform this function, the thickness of the protective layer can be set to approximately 0.1 μm to several hundred μm, for example, 0.5 μm to 500 μm, preferably 1 μm to 200 μm, and more preferably 10 μm to 100 μm. If the protective layer is too thick, the permeability to mixed gases may decrease, making efficient gas separation difficult. On the other hand, if the protective layer is too thin, it will be difficult to uniformly and evenly cover the surface of the porous support membrane with the protective layer.

In this embodiment, the functional layer preferably contains a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines. A water-soluble polymer is a polymer compound that is soluble or readily soluble in water. In this embodiment, it is preferable to use at least one water-soluble polymer selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.

On the other hand, alkanolamines are compounds having a hydroxy group and an amino group in an alkane skeleton. The alkanolamines used in this embodiment are preferably water-soluble. Examples of such water-soluble alkanolamines include methanolamine, ethanolamine, propanolamine, heptaminol, dimethylethanolamine, N-methylethanolamine, N-(2-aminoethyl)ethanolamine, N-[2-(dimethylamino)ethyl], N-methylethanolamine, N-[2-(diethylamino)ethyl]ethanolamine, N-(1,2-dihydroxy-n-propyl)piperazine, N-[(1-hydroxymethyl, 2-hydroxy)-n-propyl]piperazine, N Examples of such compounds include N-[(1-hydroxy, 2-hydroxymethyl)-n-propyl]piperazine, N-(1,2-dihydroxy-n-propyl)-N'-methyl-piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]-N'-methyl-piperazine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), and pentaethylenehexamine (PEHA).

The reason why a water-soluble polymer and a water-soluble alkanolamine are used in this embodiment is that, when forming the functional layer, the water-soluble polymer and the water-soluble alkanolamine are dissolved in water, and the solution is applied to the surface of a porous support membrane and dried to obtain a functional layer in which the alkanolamine is dispersed in a water-soluble polymer matrix. In this embodiment, the functional layer in which the water-soluble alkanolamine is dispersed in a water-soluble polymer matrix exhibits a carbon dioxide separation function in particular. In other words, the functional layer in which the water-soluble alkanolamine is dispersed in a water-soluble polymer matrix functions to selectively allow carbon dioxide to permeate. Here, the water-soluble alkanolamine may be contained in the water-soluble polymer matrix at 1 wt % to 90 wt %, and to more effectively exhibit the carbon dioxide separation function, the water-soluble alkanolamine is contained in the water-soluble polymer matrix at 10 wt % to 80 wt %, preferably 30 wt % to 70 wt %, and more preferably 40 wt % to 60 wt %. The thickness of the functional layer can be 0.001 μm to 1000 μm, preferably 0.1 μm to 100 μm, and more preferably 0.3 μm to 5 μm. If the functional layer is too thick, gas permeability decreases, while if the functional layer is too thin, defects tend to occur in the functional layer.
In this embodiment, the stacking order of the porous support membrane, protective layer, and functional layer is an important technical feature. To separate a desired gas from a mixed gas using the gas separation membrane of this embodiment, the mixed gas is first brought into contact with the protective layer, which blocks gases that reduce the gas separation function of the functional layer, the mixed gas passes through the porous support membrane, and finally the undesired gas is separated by the functional layer, and the desired gas is obtained from the surface on the functional layer side. Therefore, the stacking order of the layers of the gas separation membrane of this embodiment is important.

A second embodiment of the present invention is a gas separation method in which a mixed gas containing at least carbon dioxide is contacted with one side of the gas separation membrane of one embodiment of the present invention, which has the protective layer, to selectively pass carbon dioxide through the gas separation membrane, and carbon dioxide is extracted from the other side, which has the functional layer. The gas separation method of the embodiment is preferably carried out using the gas separation membrane of the above-mentioned one embodiment. As described above, the gas separation membrane of one embodiment has a protective layer on one side of a porous support membrane and a functional layer on the other side. When a mixed gas containing at least carbon dioxide is contacted with the one side having the protective layer, gases contained in the mixed gas that cannot permeate the protective layer are prevented from permeating by the protective layer, and gases that have difficulty permeating the protective layer are suppressed from permeating by the protective layer. Such gases may reduce the gas separation function of the functional layer. Such gases are blocked by the protective layer and removed from the mixed gas, while the remaining mixed gases permeate through the porous support membrane. The mixed gas that permeates the porous support membrane reaches the functional layer. The functional layer contains alkanolamines that exhibit a carbon dioxide separation function (selective carbon dioxide permeability), and only carbon dioxide from the mixed gas that reaches the functional layer permeates the functional layer. In this way, carbon dioxide can be extracted from the other side of the gas separation membrane of one embodiment. The gas separation method of this embodiment can be performed over a wide temperature range, from low temperatures (e.g., 0°C) to high temperatures (e.g., 100°C).
The gas separation method of this embodiment makes it possible to separate carbon dioxide from a mixed gas containing carbon dioxide with excellent separation ability. The gas separation membrane of one embodiment preferably has a protective layer that prevents or suppresses the permeation of gases that would degrade the function of the functional layer, making it less likely that the function of the functional layer will deteriorate or be deactivated, and enabling the treatment of large amounts of mixed gas and the treatment of mixed gas over a long period of time.

A third embodiment of the present invention is a method for producing a gas separation membrane having a porous support membrane, a functional layer, and a protective layer. The method includes the steps of: applying a mixture containing siloxanes, optionally a polyolefin, and a crosslinking agent to one side of the porous support membrane, heating the mixture to form the protective layer; and then applying an aqueous solution containing a water-soluble polymer, at least one amine compound selected from water-soluble alkanolamines, and water to the other side of the porous support membrane, and drying the mixture to form the functional layer. The gas separation membrane produced by the third embodiment has a functional layer and a protective layer on the porous support membrane. This embodiment includes the steps of first applying a mixture containing siloxanes, optionally a polyolefin, and a crosslinking agent to one side of the porous support membrane, heating the mixture to form the protective layer. Here, "porous" refers to a structure having multiple holes (pores), preferably a structure having numerous pores. Porous materials include microporous materials, mesoporous materials, and macroporous materials depending on the pore size, and any of these materials may be used for the porous support membrane of this embodiment. Any material may be used as the porous material, including activated carbon, zeolite, mesoporous silica, and pumice, as well as natural fibers (cotton, linen, wool, etc.), chemical fibers (polyester, polyolefin, polyamide, acetate, promix, rayon, aramid, polyacrylonitrile, etc.), and other thermoplastic resins (polyvinyl alcohol, polysulfone, polyvinylidene fluoride, etc.). In this embodiment, the porous support membrane is a support member for attaching or supporting the protective layer and functional layer described below. The support membrane refers to a plate-like hard or soft membrane having a specific area. However, in this embodiment, the shape of the support membrane is not limited to a plate-like shape and may be a rolled-up plate-like membrane, a spherical shape, a cylindrical shape, or other shape, and can be freely formed depending on the use form of the gas separation membrane of this embodiment. The support membrane can have a thickness ranging from micrometers to millimeters depending on the intended use of the gas separation membrane of the embodiment. The thickness of the support membrane is preferably 50 μm to 1 cm, more preferably 100 μm to 5 mm, and particularly preferably 300 μm to 1 mm. Using a hollow (straw-shaped) hollow fiber membrane with micropores in the wall as the porous support membrane is particularly advantageous, as it allows for a large membrane area per volume. Hollow-shaped hollow fiber membranes have two surfaces: an inner surface and an outer surface. Ultrafiltration (UF) hollow fiber membranes and microfiltration (MF) hollow fiber membranes can be used as the porous support membrane. Examples of hollow fiber membrane materials include polyethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, and polyethylene tetrafluoride. Such UF hollow fiber membranes and MF hollow fiber membranes are commercially available.

The protective layer formed on one side of the porous support film preferably contains a crosslinked siloxane or a crosslinked mixture of siloxanes and polyolefin. Therefore, a mixture containing siloxanes (oligomers or polymers) with repeating siloxane bonds and a crosslinker is first prepared. This mixture is then applied to one side of the porous support film and heated to crosslink the siloxanes, forming a protective layer containing the crosslinked siloxanes. When forming the protective layer, a mixture containing a polyolefin in addition to the siloxanes and crosslinker may also be applied. When a mixture containing siloxanes, polyolefin, and a crosslinker is applied to one side of the porous support film and heated, a protective layer containing a crosslinked mixture of siloxanes and polyolefin is formed. The mixture of siloxanes and a crosslinker can be applied to one side of the porous support film by conventional methods such as spraying, casting, dipping, screen printing, doctor blade coating, and spin coating. Heating to crosslink the siloxanes (and optionally the polyolefin) can be carried out using conventionally known heating means such as an oven or dryer.

The siloxanes used in the embodiment include those represented by the following formula (1):
(wherein _R1 and _R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group.) Examples of such siloxanes include polydimethylsiloxane, polydiphenylsiloxane, polymethyl(3,3,3-trifluoropropyl)siloxane, poly(1-trimethylsilyl-1-propyne), polydi(trifluoropropyl)siloxane, and mixtures thereof. Furthermore, as a crosslinking agent for siloxanes, metal catalysts such as platinum, tin, titanium, etc., and acyl or alkyl organic peroxides such as dicumyl peroxide, 1,1-di(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, etc. can be used.

The protective layer formed in this process preferably functions to prevent or inhibit the permeation of gases that would impair or deactivate the functionality of the functional layer. When the mixed gas to be separated contains gases, particularly sulfur oxides (SOx) and nitrogen oxides (NOx), a protective layer is provided on one side of the porous support membrane to prevent a rapid deterioration in the gas separation performance of the functional layer of the gas separation membrane. When a mixed gas is passed through the gas separation membrane manufactured in this embodiment from the side on which the protective layer is provided, the permeation of gases that would impair the gas separation function of the functional layer (e.g., SOx and NOx) is prevented, thereby preventing these gases from reaching the functional layer. In this embodiment, the thickness of the protective layer can be approximately 0.1 μm to several hundred μm, for example, 0.55 μm to 500 μm, preferably 1 μm to 200 μm, and more preferably 10 μm to 100 μm.

This embodiment then includes a step of applying an aqueous solution containing a water-soluble polymer, at least one amine compound selected from water-soluble alkanolamines, and water to the other surface of the porous support membrane, followed by drying to form a functional layer. Here, a water-soluble polymer refers to a polymer compound that is soluble or readily soluble in water. In this embodiment, it is preferable to use at least one water-soluble polymer selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.

On the other hand, alkanolamines are compounds having a hydroxy group and an amino group in an alkane skeleton. The alkanolamines used in this embodiment are preferably water-soluble. Examples of such water-soluble alkanolamines include methanolamine, ethanolamine, propanolamine, heptaminol, dimethylethanolamine, N-methylethanolamine, N-(2-aminoethyl)ethanolamine, N-[2-(dimethylamino)ethyl], N-methylethanolamine, N-[2-(diethylamino)ethyl]ethanolamine, N-(1,2-dihydroxy-n-propyl)piperazine, N-[(1-hydroxymethyl, 2-hydroxy)-n-propyl]piperazine, N Examples of such compounds include N-[(1-hydroxy, 2-hydroxymethyl)-n-propyl]piperazine, N-(1,2-dihydroxy-n-propyl)-N'-methyl-piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]-N'-methyl-piperazine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), and pentaethylenehexamine (PEHA).

The water-soluble alkanolamines should be contained in the water-soluble polymer matrix at 1% to 90% by weight. To more effectively achieve carbon dioxide gas separation functionality, the content should be 10% to 80% by weight, preferably 30% to 70% by weight, and more preferably 40% to 60% by weight. Therefore, to form such a functional layer, 0.1% to 50%, preferably 1% to 30%, of the water-soluble alkanolamine and 0.01% to 20%, preferably 0.1% to 10%, of the water-soluble polymer can be dissolved in water by weight, and this mixed aqueous solution can be applied to the other side of the porous support membrane.

The solvent used to dissolve the water-soluble polymer and water-soluble alkanolamine contains water as the primary component, and may include, for example, methanol, ethanol, propanol, acetone, dimethylacetamide, tetrahydrofuran, or a mixture of one or more of these. In this specification, the term "water" used to dissolve the water-soluble polymer and water-soluble alkanolamine includes the case where the water-soluble polymer and water-soluble alkanolamine contain the above-mentioned components in addition to the primary component water. The water-soluble polymer and water-soluble alkanolamine are dissolved in water, and the mixture is preferably stirred thoroughly by a known method (e.g., stirring with a stirrer or stirrer blade, stirring with a shaker, or ultrasonic stirring) to obtain a substantially uniform aqueous mixture. This aqueous mixture can then be applied to the surface of a porous support film and dried to form a functional layer in which the alkanolamine is dispersed within the water-soluble polymer matrix. The aqueous mixture can be applied to the porous support film by conventional methods such as spraying, casting, dipping, screen printing, doctor blade coating, and spin coating. The applied mixed aqueous solution can be dried by known methods such as leaving it in the atmosphere or drying it in various ovens or dryers. It can also be dried under an inert gas such as helium, argon, or nitrogen. The thickness of the functional layer thus formed can be 0.001 μm to 1000 μm, preferably 0.1 μm to 100 μm, and more preferably 0.3 μm to 5 μm. In this embodiment, the functional layer in which water-soluble alkanolamines are dispersed within a water-soluble polymer matrix is particularly capable of exhibiting a carbon dioxide gas separation function (selective carbon dioxide permeability).

In this embodiment, it is important to first form a protective layer on one side of the porous support film, and then form a functional layer on the other side of the porous support film. By forming the protective layer and the functional layer on both sides of the porous support film in this order, both layers can be provided stably without unevenness.
FIG. 1 shows the steps and the order of the steps in the method for producing a gas separation membrane of this embodiment.

A fourth embodiment of the present invention provides a gas mixture inlet for introducing a gas mixture containing at least carbon dioxide;
a carbon dioxide outlet for discharging the carbon dioxide separated from the mixed gas;
a separated gas outlet for discharging a separated mixed gas from which carbon dioxide has been separated;
and a gas separation membrane module having one or more gas separation membranes disposed inside the module container. In the gas separation membrane module of this embodiment, the gas separation membrane has a protective layer containing a crosslinked siloxane or a crosslinked mixture of a siloxane and a polyolefin on one side of the hollow fiber membrane, and a functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines on the other side of the hollow fiber membrane. A gas separation membrane module of a fourth embodiment of the present invention comprises, as a component, a module container having a mixed gas inlet for introducing a mixed gas containing at least carbon dioxide, a carbon dioxide outlet for discharging carbon dioxide separated from the mixed gas, and a separated gas outlet for discharging a separated mixed gas in which carbon dioxide has been separated from the mixed gas. The module container is a housing in which one or more gas separation membranes described below can be disposed. The module container may have any shape, such as a prismatic shape such as a rectangular parallelepiped or a cube, a cylindrical shape, or a spherical shape, and may be made of a material such as metal, plastic, or resin. The module container includes a mixed gas inlet for introducing a mixed gas containing at least carbon dioxide, a carbon dioxide outlet for discharging carbon dioxide separated from the mixed gas, and a separated gas outlet for discharging the separated mixed gas in which carbon dioxide has been separated from the mixed gas. The mixed gas introduced into the module container from the mixed gas inlet permeates one or more gas separation membranes, which will be described later, arranged inside the module container, where it is separated into carbon dioxide and a separated gas from which the carbon dioxide has been separated. The carbon dioxide is discharged from the carbon dioxide outlet, and the separated gas is discharged from the separated gas outlet.
An example of a gas separation membrane module of this embodiment is shown in Figure 2. In Figure 2, 1 is a gas separation membrane module, 2 is a module container, 21 is a mixed gas inlet, 22 is a carbon dioxide outlet, 23 is a separated gas outlet, and 24 is a sweep gas inlet.

The gas separation membrane placed inside the module container has a protective layer containing a crosslinked siloxane or a crosslinked mixture of a siloxane and a polyolefin on one side of the hollow fiber membrane, and a functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines on the other side of the hollow fiber membrane. The hollow fiber membrane used as a support for the gas separation membrane is a hollow (straw-shaped) membrane with micropores in the wall. The hollow fiber membrane has two surfaces: an inner surface and an outer surface. The thickness of the hollow fiber membrane can vary from micrometers to millimeters, for example, 10 μm to 1 mm, preferably 30 μm to 800 μm, and more preferably 50 μm to 500 μm. Ultrafiltration (UF) hollow fiber membranes and microfiltration (MF) hollow fiber membranes can be used. Examples of materials for hollow fiber membranes include polyethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, and polyethylene tetrafluoride. Such UF hollow fiber membranes and MF hollow fiber membranes are commercially available.

The gas separation membrane used in this embodiment has a protective layer containing a crosslinked siloxane or a mixed crosslinked siloxane and polyolefin on one surface of the hollow fiber membrane. The protective layer is preferably a layer having a function of preventing or suppressing the permeation of gases that would reduce the gas separation function of the functional layer. In this embodiment, the protective layer preferably contains a crosslinked siloxane or a mixed crosslinked siloxane and polyolefin. Here, siloxanes refer to compounds having repeating siloxane bonds, and may be oligomers or polymers. Here, siloxanes are compounds represented by the following formula (1):
(wherein _R1 and _R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group.) Examples of such siloxanes include polydimethylsiloxane, polydiphenylsiloxane, polymethyl(3,3,3-trifluoropropyl)siloxane, poly(1-trimethylsilyl-1-propyne), polydi(trifluoropropyl)siloxane, and mixtures thereof. In addition, as a crosslinking agent for siloxanes, metal catalysts such as platinum, tin, titanium, etc., and acyl or alkyl organic peroxides such as dicumyl peroxide, 1,1-di(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, etc. can be used. The protective layer contains a crosslinked product of these siloxanes. The protective layer may contain a mixed crosslinked product of the siloxanes and, optionally, a polyolefin.

On the other hand, the gas separation membrane used in this embodiment has a functional layer on both sides of the hollow fiber membrane, which contains a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines. The functional layer is a layer that has the function of separating a desired gas from a gas mixture containing the desired gas, or conversely, the function of separating undesired gases (gas separation function). Here, a water-soluble polymer refers to a polymer compound that is soluble or easily soluble in water. In this embodiment, it is preferable to use at least one water-soluble polymer selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.

On the other hand, alkanolamines are compounds having a hydroxy group and an amino group in an alkane skeleton, and the alkanolamines used in this embodiment are preferably water-soluble. Examples of such water-soluble alkanolamines include methanolamine, ethanolamine, propanolamine, heptaminol, dimethylethanolamine, N-methylethanolamine, N-(2-aminoethyl)ethanolamine, N-[2-(dimethylamino)ethyl], N-methylethanolamine, N-[2-(diethylamino)ethyl]ethanolamine, N-(1,2-dihydroxy-n-propyl)piperazine, N-[(1-hydroxymethyl,2-hydroxy)-n-propyl]piperazine, N Examples of such compounds include N-[(1-hydroxy, 2-hydroxymethyl)-n-propyl]piperazine, N-(1,2-dihydroxy-n-propyl)-N'-methyl-piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]-N'-methyl-piperazine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), and pentaethylenehexamine (PEHA).

In this embodiment, the functional layer is a layer in which water-soluble alkanolamines are dispersed within a water-soluble polymer matrix. Such a functional layer is particularly capable of separating carbon dioxide gas. The water-soluble alkanolamines may be contained in the water-soluble polymer matrix at a concentration of 1% to 90% by weight. To more effectively separate carbon dioxide gas, the water-soluble alkanolamines are contained at 10% to 80% by weight, preferably 30% to 70% by weight, and more preferably 40% to 60% by weight. The thickness of the functional layer can be 0.001 μm to 1000 μm, preferably 0.1 μm to 100 μm, and more preferably 0.3 μm to 5 μm.
In this embodiment, the structure in which a protective layer is formed on one surface of the hollow fiber membrane and a functional layer is formed on the second surface is an important technical feature. The gas separation membrane module of this embodiment is used in such a way that a mixed gas is first brought into contact with the protective layer of the gas separation membrane arranged inside, the protective layer blocks gases that reduce the gas separation function of the functional layer, the mixed gas passes through the hollow fiber membrane, and finally the functional layer separates undesired gases, obtaining the desired gas from the surface facing the functional layer. Therefore, the order of construction of the layers of the gas separation membrane used in this embodiment is important. Note that in this embodiment, it is particularly preferable that a functional layer is formed on the inner surface of the hollow fiber membrane and a protective layer is formed on the outer surface. However, depending on the use mode of the gas separation membrane module, a functional layer may be provided on the outer surface of the hollow fiber membrane and a protective layer may be formed on the inner surface.
Figure 3 shows an example of a gas separation membrane used in this embodiment. Figure 3 shows a cross-sectional view of a gas separation membrane in which a functional layer is formed on the inner surface of a hollow fiber membrane and a protective layer is formed on the outer surface. In the gas separation membrane of Figure 3, a mixed gas containing sulfur oxides or nitrogen oxides, including carbon dioxide, nitrogen, and sulfur dioxide, is first brought into contact with the protective layer side of the gas separation membrane. The protective layer blocks gases (sulfur oxides, nitrogen oxides, etc.) that reduce the gas separation function of the functional layer, while other gases pass through the hollow fiber membrane. Next, the functional layer separates gases (nitrogen, etc.) other than the desired gas (carbon dioxide), allowing carbon dioxide to be obtained from the functional layer side.

One or more gas separation membranes using such hollow fiber membranes are arranged inside the module container. The gas separation membranes may be arranged in any manner inside the module container, such as in regular parallel rows, in a circular arrangement, or with or without gaps inside the module container.

A fifth embodiment of the present invention is a method for separating carbon dioxide from a mixed gas, comprising the steps of: introducing a mixed gas containing at least carbon dioxide through the mixed gas inlet of the gas separation membrane module of the fourth embodiment; contacting the mixed gas with one surface of the gas separation membrane to selectively pass carbon dioxide through the gas separation membrane; extracting carbon dioxide from the second surface of the gas separation membrane; discharging the extracted carbon dioxide through the carbon dioxide outlet; and discharging a separated mixed gas in which carbon dioxide has been separated from the mixed gas through the separated gas outlet. First, a mixed gas containing at least carbon dioxide is introduced into the module container through the mixed gas inlet of the gas separation membrane module of the fourth embodiment. The introduced mixed gas is brought into contact with one surface of the gas separation membrane, i.e., the surface on which the protective layer is formed, allowing the mixed gas to permeate the gas separation membrane. Of the mixed gas that comes into contact with the protective layer, gases whose permeation is prevented or suppressed by the protective layer are unable to permeate the hollow fiber membrane and become separated gases. Meanwhile, the gas that has permeated the protective layer permeates the hollow fiber membrane and reaches the second surface of the gas separation membrane, i.e., the functional layer. Of the mixed gas that reaches the functional layer, only carbon dioxide permeates the functional layer, while the other gases cannot permeate and become separated gases. In this way, carbon dioxide is extracted from the surface on which the functional layer is formed. The extracted carbon dioxide is discharged through a carbon dioxide outlet, and the remaining separated gas after carbon dioxide has been separated from the mixed gas is discharged through a separated gas outlet. In this way, carbon dioxide can be selectively separated from a mixed gas using the gas separation membrane module of the fourth embodiment. The gas separation method of this embodiment can be performed over a wide temperature range, from low temperatures (e.g., 0°C) to high temperatures (e.g., 100°C).

A sixth embodiment of the present invention provides a gas mixture inlet for introducing a gas mixture containing at least carbon dioxide;
a carbon dioxide outlet for discharging the carbon dioxide separated from the mixed gas;
a separated gas outlet for discharging a separated mixed gas from which carbon dioxide has been separated;
Inside the module container,
A protective layer is provided on one side of the hollow fiber membrane,
This is a method for producing a gas separation membrane module in which one or more gas separation membranes having functional layers are arranged on two surfaces of the hollow fiber membranes. In this embodiment, the method first includes a step of arranging one or more hollow fiber membranes inside a module container. Here, the module container is a housing capable of arranging one or more hollow fiber membranes inside. The module container may have any shape, such as a prismatic shape such as a rectangular parallelepiped or cube, a cylindrical shape, or a sphere, and may be made of metal, plastic, resin, or the like. The module container includes a mixed gas inlet for introducing a mixed gas containing at least carbon dioxide, a carbon dioxide outlet for discharging carbon dioxide separated from the mixed gas, and a separated gas outlet for discharging a separated mixed gas in which carbon dioxide has been separated from the mixed gas. One or more hollow fiber membranes are arranged inside such a module container. Here, the hollow fiber membrane is a hollow (straw-shaped) membrane having micropores in the wall surface. The hollow hollow fiber membrane has two surfaces, an inner surface and an outer surface. The thickness of the hollow fiber membrane can vary from micrometers to millimeters, for example, 10 μm to 1 mm, preferably 30 μm to 800 μm, and more preferably 50 μm to 500 μm. Ultrafiltration (UF) hollow fiber membranes and microfiltration (MF) hollow fiber membranes can be used. Examples of hollow fiber membrane materials include polyethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, and polyethylene tetrafluoride. Commercially available UF and MF hollow fiber membranes are available. The hollow fiber membranes may be arranged in any manner within the module container, such as in a regular array, a circular arrangement, or with or without gaps within the module container.

This embodiment then includes a step of applying a mixture containing siloxanes, optionally a polyolefin, and a crosslinking agent to one surface of the hollow fiber membranes placed inside the module container, followed by heating to form a protective layer. A mixture containing siloxanes, which are compounds (oligomers or polymers) having repeating siloxane bonds, and a crosslinking agent can be applied and heated to crosslink the siloxanes, forming a protective layer containing a crosslinked product of the siloxanes. When forming the protective layer, a mixture containing a polyolefin in addition to the siloxanes and crosslinking agent may be applied. When a mixture containing siloxanes, a polyolefin, and a crosslinking agent is applied to one surface of the hollow fiber membrane and heated, a protective layer containing a crosslinked mixture of the siloxanes and the polyolefin is formed. The mixture of siloxanes and a crosslinking agent can be applied to one surface of the hollow fiber membrane by a conventionally known method, such as spraying, casting, dipping, screen printing, doctor blade coating, or spin coating. Heating for crosslinking the siloxanes (and optionally the polyolefin) can be carried out by appropriately using a conventionally known heating means such as an oven, a dryer, etc. The siloxanes used in the embodiment include those represented by the following formula (1):
(wherein _R1 and _R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group.) Examples of such siloxanes include polydimethylsiloxane, polydiphenylsiloxane, polymethyl(3,3,3-trifluoropropyl)siloxane, poly(1-trimethylsilyl-1-propyne), polydi(trifluoropropyl)siloxane, and mixtures thereof. In addition, as a crosslinking agent for siloxanes, metal catalysts such as platinum, tin, titanium, etc., and acyl or alkyl organic peroxides such as dicumyl peroxide, 1,1-di(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, etc. can be used. The protective layer formed in this process preferably has the function of preventing or suppressing the permeation of gases that degrade or deactivate the function of the functional layer. When the mixed gas to be separated contains gases, particularly sulfur oxides (SOx) and nitrogen oxides (NOx), a protective layer is first provided on the outer surface of the hollow fiber membrane to prevent the gas separation performance of the functional layer of the gas separation membrane from rapidly deteriorating. By providing a protective layer on the hollow fiber membrane of this embodiment, when the mixed gas is passed through the side on which the protective layer is provided, the permeation of gases that degrade the gas separation function of the functional layer (e.g., SOx and NOx) is prevented, thereby preventing these gases from coming into contact with the functional layer. In this embodiment, the thickness of the protective layer can be approximately 0.1 μm to several hundred μm, for example, 0.5 μm to 500 μm, preferably 1 μm to 200 μm, and more preferably 10 μm to 100 μm.

This embodiment then includes a step of applying an aqueous solution containing a water-soluble polymer, at least one amine compound selected from water-soluble alkanolamines, and water to the second surface of the hollow fiber membrane, followed by drying to form the functional layer. Here, a water-soluble polymer refers to a polymer compound that is soluble or readily soluble in water. In this embodiment, it is preferable to use at least one water-soluble polymer selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof.

On the other hand, alkanolamines are compounds having a hydroxy group and an amino group in an alkane skeleton. The alkanolamines used in this embodiment are preferably water-soluble. Examples of such water-soluble alkanolamines include methanolamine, ethanolamine, propanolamine, heptaminol, dimethylethanolamine, N-methylethanolamine, N-(2-aminoethyl)ethanolamine, N-[2-(dimethylamino)ethyl], N-methylethanolamine, N-[2-(diethylamino)ethyl]ethanolamine, N-(1,2-dihydroxy-n-propyl)piperazine, N-[(1-hydroxymethyl, 2-hydroxy)-n-propyl]piperazine, N Examples of suitable water-soluble alkanolamines include N-[(1-hydroxy,2-hydroxymethyl)-n-propyl]piperazine, N-(1,2-dihydroxy-n-propyl)-N'-methyl-piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]piperazine, N-[1,2-bis(hydroxymethyl)-n-propyl]-N'-methyl-piperazine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), and pentaethylenehexamine (PEHA). The water-soluble alkanolamines may be contained in an amount of 1% to 90% by weight within the water-soluble polymer matrix, and in order to more effectively exhibit the carbon dioxide gas separation function, the amount is 10% to 80% by weight, preferably 30% to 70% by weight, and more preferably 40% to 60% by weight. To form such a functional layer, 0.1%-50%, preferably 1%-30%, of a water-soluble alkanolamine and 0.01%-20%, preferably 0.1%-10%, of a water-soluble polymer are dissolved in water by weight, and this mixed aqueous solution can be applied to both sides of the hollow fiber membrane.

The solvent used to dissolve the water-soluble polymer and water-soluble alkanolamine contains water as a primary component, and may include, for example, methanol, ethanol, propanol, acetone, dimethylacetamide, tetrahydrofuran, or a mixture of one or more of these. The water-soluble polymer and water-soluble alkanolamine are dissolved in water, and the resulting mixture is preferably thoroughly stirred by a known method (e.g., stirring with a stirrer, a stirring blade, a shaker, or ultrasonic stirring) to obtain a substantially uniform aqueous mixture. This aqueous mixture can then be applied to both surfaces of a hollow fiber membrane and dried to form a functional layer in which the alkanolamine is dispersed within the water-soluble polymer matrix. The aqueous mixture can be applied to the porous support membrane by conventional methods such as spraying, casting, dipping, screen printing, doctor blade coating, and spin coating. The applied aqueous mixture can be dried by known methods such as leaving it in the air or drying it in various ovens or dryers. It can also be dried under an inert gas such as helium, argon, or nitrogen. The thickness of the functional layer thus formed can be 0.001 μm to 1000 μm, preferably 0.1 μm to 100 μm, and more preferably 0.3 μm to 5 μm.

In this embodiment, it is important to first form a protective layer on one surface of the hollow fiber membrane, and then form a functional layer on the second surface of the hollow fiber membrane. By forming the protective layer and functional layer on the inner and outer surfaces of the hollow fiber membrane in this order, both layers can be formed stably and without unevenness. In this embodiment, it is particularly preferable that the functional layer be formed on the inner surface of the hollow fiber membrane and the protective layer be formed on the outer surface. However, depending on the use of the manufactured gas separation membrane module, the functional layer may be formed on the outer surface of the hollow fiber membrane and the protective layer may be formed on the inner surface.

The gas separation membrane of this embodiment has a protective layer on one side of the porous support membrane, which preferably prevents or suppresses the permeation of gases that degrade the function of the functional layer. This makes it possible to prevent or minimize deterioration of the functional layer due to gases that may be contained in the mixed gas and that degrade the function of the functional layer. This makes it possible to process large amounts of mixed gas using the gas separation membrane, extending the life of the gas separation membrane. It is also possible to obtain a gas separation membrane module using the gas separation membrane of this embodiment. Gas separation membranes and gas separation membrane modules can be manufactured using a manufacturing method with a relatively small number of steps. A gas separation method using a gas separation membrane and a gas separation membrane module makes it possible to selectively and efficiently separate desired gases.

Embodiments of the present invention are described in detail below. The present invention is not limited to the following examples, as long as they do not depart from the gist of the invention.

[Manufacturing Example 1: Gas Separation Membrane and Gas Separation Membrane Module]

10 g of a base agent of polydimethylsiloxane (SYLGARD184, Toray Dow Corning Co., Ltd.) was mixed with 1 g of a catalyst (crosslinking agent). This mixed liquid was applied to the outer surface of a hollow fiber membrane (product name: Microza LP-1053, Asahi Kasei Corporation, effective area: 4.4 cm ² ) with an inner pore diameter of 1.4 mm. This hollow fiber membrane was placed in an oven, and the temperature was raised to 80°C to form a protective layer (thickness: 10 μm) in which the polydimethylsiloxane was crosslinked.
Next, 2 g of polyvinyl alcohol (weight average molecular weight: 60,000, Wako Pure Chemical Industries, Ltd.) was dissolved in 198 g of water, and 1 g of N-(2-aminoethyl)-ethanolamine was added thereto and stirred to obtain a mixed aqueous solution. The obtained mixed aqueous solution was passed through the inside of the hollow fiber membrane on which the protective layer had been formed, contacted therewith, and allowed to dry for 12 hours under room temperature atmospheric conditions to form a functional layer (thickness: 0.8 μm). The content of N-(2-aminoethyl)-ethanolamine in the functional layer was 50% relative to the weight of polyvinyl alcohol. In this way, a hollow fiber membrane-type gas separation membrane was obtained.
One of the obtained gas separation membranes was placed inside a stainless steel module container equipped with a mixed gas inlet, a separated gas outlet, a carbon dioxide outlet, and an inlet for supplying a sweep gas to sweep away the carbon dioxide that had permeated the gas separation membrane, thereby obtaining a gas separation membrane module.

Example 1: Separation of mixed gases
Cylinders containing carbon dioxide, nitrogen, and sulfur dioxide (SO ₂ ) were prepared, and these were connected via appropriate equipment such as flow meters so that they were mixed just before being introduced into the gas separation membrane module. Using a mass flow controller, a mixed gas containing 10% carbon dioxide, 90% nitrogen, and 30 ppm sulfur dioxide (SO ₂ ) was prepared. This mixed gas was introduced into the mixed gas inlet of the gas separation membrane module at a set temperature of 40 ° C and a feed rate of approximately 50 mL / min. At the same time, helium (sweep gas) was introduced, and the mixed gas was brought into contact with the outer surface (feed side) of the gas separation membrane. Carbon dioxide discharged from the inner surface (permeation side) of the gas separation membrane was discharged from the carbon dioxide outlet, and the separated gas was discharged from the separated gas outlet. The flow rate of the gas discharged from each outlet was measured with a flow meter, and the gas components were analyzed by gas chromatography to calculate the permeation flux and carbon dioxide selectivity of each gas.
The gas separation conditions are as follows:
Mixed gas supply rate: about 50 mL/min Set temperature: 40°C
Mixed gas: carbon dioxide/nitrogen = 10/90 (vol/vol) containing 30 ppm _SO2 Permeation side sweep gas: helium Relative humidity: 90%
Pressure: Feed side: 155 kPa, Permeation side: 105 kPa
The formulas for calculating the permeation flux Q (carbon dioxide) and Q (nitrogen) (unit: GPU [1×10 ⁻⁶ cm ³ (STP)/(s·cm ² ·cmHg)]) and the carbon dioxide selectivity are as follows:

(In the formula, Q: permeation flux, n: gas volume, A: hollow fiber membrane area, t: time, Δp: difference in partial pressure between the feed side (outside the hollow fiber membrane) and the permeation side (inside the hollow fiber membrane).)

(In the formula, α(CO ₂ /N ₂ ): selectivity coefficient of carbon dioxide, Q _(CO2) : permeation flux of carbon dioxide, and Q _(N2) : permeation flux of nitrogen.)

The gas chromatography analysis conditions were as follows:
Supply side: TCD detector GC7870A (Agilent Technology),
Column: HayeSep Q x 0.5m MS5A x 6 feet HayeSep Q x 6 feet MS5A x 6 feet,
Transmission side: PDHID detector GC7870A (Agilent Technology),
Column: SHINCARBON x 4 m HayeSep Q x 0.5 m
He sweep gas volume: 10 mL/min

The change in carbon dioxide permeation flux over time is shown in Figure 4, and the change in carbon dioxide selectivity (carbon dioxide permeability/nitrogen permeability) over time is shown in Figure 5.

Furthermore, using the gas separation membrane module of Example 1, a mixed gas containing 10% carbon dioxide and 90% nitrogen, and containing 300 ppm of sulfur dioxide (SO ₂ ), was separated. The mixed gas was introduced into the mixed gas inlet of the gas separation membrane module and brought into contact with the outer surface of the gas separation membrane. Carbon dioxide discharged from the inner surface of the gas separation membrane was discharged from the carbon dioxide outlet, and the separated gas was discharged from the separated gas outlet. The gas separation conditions were as described above. The change in carbon dioxide permeation flux over time is shown in Figure 3, and the change in carbon dioxide selectivity (carbon dioxide permeability/nitrogen permeability) over time is shown in Figure 4.

Comparative Manufacturing Example 1: Gas separation membrane and gas separation membrane module without protective layer
Example 1 was repeated except that the protective layer was not formed, to obtain a gas separation membrane having only a functional layer formed thereon. A gas separation membrane module was produced using this gas separation membrane in the same manner as in Example 1, and gas separation was performed under the same conditions as in Example 1. The permeation flux and carbon dioxide selectivity were calculated in the same manner as in Example 1. The change over time in carbon dioxide permeation flux is shown in Figure 4, and the change over time in carbon dioxide selectivity is shown in Figure 5, respectively.

Comparative Example 1: Separation of mixed gases
Furthermore, a mixed gas containing 10% carbon dioxide, 90% nitrogen, and 300 ppm sulfur dioxide (SO ₂ ) was separated using the gas separation membrane module of Comparative Example 1. The change in carbon dioxide permeation flux over time is shown in Figure 6 , and the change in carbon dioxide selectivity (carbon dioxide permeability/nitrogen permeability) over time is shown in Figure 7 .

The gas separation membrane of the present invention and a gas separation membrane module using the same were able to selectively separate carbon dioxide from a mixed gas containing carbon dioxide. The model mixed gas containing 30 ppm SO ₂ used in the examples and comparative examples contained the highest concentration of SO ₂ among exhaust gases emitted from facilities such as factories. However, even when such a mixed gas was contacted with the gas separation membrane (gas separation membrane module) of the present invention, the carbon dioxide permeation flux and selectivity were not lost for a long period of time (Figures 4 and 5). In contrast, the gas separation membrane (gas separation membrane module) of the comparative manufacturing example showed a gradual decrease in carbon dioxide permeation flux over time, and the carbon dioxide selectivity also decreased sharply after 200 hours of use (Figures 4 and 5). Note that the gas separation performed using a model mixed gas containing 300 ppm SO ₂ was a so-called accelerated test, and the gas separation membrane (gas separation membrane module) of the present invention did not show a decrease in carbon dioxide permeation flux and selectivity even in the accelerated test (Figures 6 and 7). This result suggests that the gas separation membrane (gas separation membrane module) of the present invention can maintain its gas separation performance for a long period of time.
The gas separation membrane of the present invention, which has a protective layer on one side of the porous support membrane and a functional layer on the other side, maintains its gas separation performance for a long period of time and has a long life, even if the mixed gas to be separated contains gases that reduce the gas separation performance of the functional layer.

Claims (16)

A gas separation membrane having a porous support membrane, a functional layer, and a protective layer,
The protective layer includes a crosslinked siloxane or a mixed crosslinked siloxane and polyolefin on one surface of the porous support film,
The gas separation membrane as described above, wherein the functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines is provided on the other surface of the porous support membrane. The gas separation membrane of claim 1, wherein the water-soluble polymer is at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof. The siloxanes are represented by the following formula (1):
(wherein _R1 and _R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), The gas separation membrane according to any one of claims 1 to 3, wherein the porous support membrane is a hollow fiber membrane. A gas mixture containing at least carbon dioxide is brought into contact with one surface of the gas separation membrane according to any one of claims 1 to 4, the surface having the protective layer, to selectively pass carbon dioxide through the gas separation membrane;
and extracting carbon dioxide from the other surface having the functional layer.
Gas separation methods. A method for producing a gas separation membrane having a porous support membrane, a functional layer, and a protective layer, comprising:
a method for producing the gas separation membrane, comprising the steps of: applying a mixture containing siloxanes, optionally a polyolefin, and a crosslinking agent to one surface of the porous support membrane, and heating the mixture to form the protective layer; and then applying an aqueous solution containing water-soluble polymers, at least one amine compound selected from water-soluble alkanolamines, and water to the other surface of the porous support membrane, and drying the mixture to form a functional layer. The method for producing a gas separation membrane according to claim 6, wherein the water-soluble polymer is at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof. The siloxanes are represented by the following formula (1):
(wherein _R1 and _R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), The method for producing a gas separation membrane according to any one of claims 6 to 8, wherein the porous support membrane is a hollow fiber membrane. a mixed gas inlet for introducing a mixed gas containing at least carbon dioxide;
a carbon dioxide outlet for discharging the carbon dioxide separated from the mixed gas;
a separated gas outlet for discharging a separated mixed gas from which carbon dioxide has been separated;
A gas separation membrane module in which one or more gas separation membranes are disposed inside a module container comprising:
A protective layer containing a crosslinked siloxane or a mixed crosslinked product of a siloxane and a polyolefin is provided on one surface of the hollow fiber membrane,
The gas separation membrane module is characterized in that it has a functional layer on two surfaces of the hollow fiber membrane, the functional layer containing a water-soluble polymer and at least one amine compound selected from water-soluble alkanolamines. The gas separation membrane module of claim 10, wherein the water-soluble polymer is at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof. The siloxanes are represented by the following formula (1):
(wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group), A mixed gas containing at least carbon dioxide is introduced through the mixed gas inlet of the gas separation membrane module according to any one of claims 10 to 12,
contacting one surface of the gas separation membrane with the mixed gas to selectively pass carbon dioxide through the gas separation membrane;
Carbon dioxide is extracted from the two surfaces of the gas separation membrane;
The extracted carbon dioxide is discharged from the carbon dioxide discharge port.
and discharging the separated gas mixture from the separated gas outlet. a mixed gas inlet for introducing a mixed gas containing at least carbon dioxide;
a carbon dioxide outlet for discharging the carbon dioxide separated from the mixed gas;
a separated gas outlet for discharging a separated mixed gas from which carbon dioxide has been separated;
Inside the module container,
A protective layer is provided on one surface of the hollow fiber membrane,
A method for producing a gas separation membrane module, in which one or more gas separation membranes having functional layers are arranged on two surfaces of the hollow fiber membrane,
One or more hollow fiber membranes are placed inside the module container,
a mixture containing siloxanes, optionally polyolefins, and a crosslinking agent is applied to one surface of the hollow fiber membrane and heated to form the protective layer; and then an aqueous solution containing water-soluble polymers, at least one amine compound selected from water-soluble alkanolamines, and water is applied to the second surface of the hollow fiber membrane and dried to form the functional layer.
A method for producing the gas separation membrane module, comprising the steps of: The method for producing a gas separation membrane module according to claim 14, wherein the water-soluble polymer is at least one selected from the group consisting of polyvinyl alcohols, polyacrylic acids, polyethylene glycols, polyvinylpyrrolidones, polyamines, polysaccharides, and copolymers thereof. The siloxanes are represented by the following formula (1):
(wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or a phenyl group),