Fluid separation membrane and fluid separation membrane module

Abstract

The present invention can provide a fluid separation membrane that exhibits a high separation performance and a high durability with an improved brittleness, and relates to a fluid separation membrane that has a separation-functional layer, wherein: the carbon element ratio of the separation-functional layer is 40-98 atom% and the separation-functional layer has, in the interior thereof, voids having an average pore diameter of 3-150 nm.

Description

Fluid separation membrane and fluid separation membrane module

[0001] The present invention relates to a fluid separation membrane and a fluid separation membrane module.

[0002] Separation of specific components from various mixed gases and liquids has traditionally been achieved by cryogenic separation, PSA (Pressure Sensitive Adsorption), and chemical / physical absorption. However, these technologies require cryogenic conditions and regeneration procedures, necessitating a significant amount of energy for separation. On the other hand, membrane separation has the advantages of low energy consumption and the ability to miniaturize the equipment.

[0003] Examples of materials proposed for separation membranes include organic polymer membranes and inorganic membranes such as zeolite membranes, silica membranes, and carbon membranes. Among these, carbon membranes are expected to be put to practical use because they exhibit excellent separation performance and can be used in environments where heat resistance and chemical resistance are required, where organic membranes cannot be used. Typical carbon membranes have pores of different sizes, known as ultramicropores (<0.7 nm) and micropores (0.7 nm to 2.0 nm) (M. Rungta, et al., Carbon, 115 (2017), pp. 237-248). Ultramicropores primarily contribute to separation selectivity, while micropores enhance the transport properties within the membrane, enabling excellent separation performance while achieving both high permeability and high separation factor.

[0004] Separation membranes using a carbon membrane as a separation functional layer are broadly classified into two types: free-standing carbon membranes that do not use a porous support, and tubular or monolithic composite carbon membranes in which a carbon membrane is formed on the surface of a porous support. Examples of composite carbon membranes that have been proposed include a porous ceramic composite hollow fiber membrane in which a thin carbon film is supported on the surface of a porous ceramic hollow fiber membrane (see, for example, Patent Document 1), and a carbon membrane for fluid separation that has a core layer with a cocontinuous porous structure and a skin layer formed around the core layer that does not substantially have a cocontinuous porous structure (see, for example, Patent Document 2).

[0005] Japanese Patent Application Laid-Open No. 08-299769 International Publication No. 2016 / 13676

[0006] In gas purification facilities using separation membranes, the greater the partial pressure difference across the separation membrane, the higher the permeation rate. Therefore, from the viewpoint of energy efficiency, separation and purification under high-pressure conditions are often desired, and separation membranes that can withstand high pressures are required. For example, in natural gas purification plants, the application of membrane separation methods utilizing high supply pressures of several MPa or more is being considered to separate and remove carbon dioxide, an impurity, from methane gas, the main component. In addition, in the chemical industry, membrane separation methods are beginning to be used in processes such as separating and purifying water, an impurity contained in alcohol or acetic acid, and efficient separation and purification requires a large pressure difference between the upstream and downstream sides of the separation membrane.

[0007] However, the conventional fluid separation membranes described in Patent Documents 1 and 2 have the problem that they are prone to defects and breakage due to the influence of vibrations during use and stresses generated by dimensional changes due to fluctuations in pressure and temperature. Furthermore, defects and breakage of the separation membrane may occur during processing and assembly in the manufacturing process of the separation membrane module, and these problems are particularly pronounced in highly brittle carbon membranes. When a separation membrane is defective or broken, the fluid to be separated leaks downstream of the separation membrane, reducing separation selectivity, and therefore there is a demand for separation membranes with high durability.

[0008] Therefore, an object of the present invention is to provide a highly durable fluid separation membrane that has high separation performance and improved brittleness.

[0009] The present invention, which solves the above-mentioned problems, has the following configuration.

[0010] A fluid separation membrane having a separation functional layer, wherein the carbon element ratio of the separation functional layer is 40 atomic % or more and 98 atomic % or less, and the separation functional layer has voids therein with an average pore diameter of 3 nm or more and 150 nm or less.

[0011] The present invention provides a highly durable fluid separation membrane with high separation performance and improved brittleness. The separation functional layer in the fluid separation membrane of the present invention has a plurality of voids with an average pore size of 3 nm to 150 nm, which increases fluid diffusibility and results in a fluid separation membrane with higher permeability than conventionally known carbon membranes. Furthermore, the dispersion of voids within the separation functional layer increases toughness and suppresses the progression of defects such as cracks, resulting in a fluid separation membrane with excellent durability.

[0012] 1 is a scanning transmission electron microscope photograph of a cross section of the fluid separation membrane of Example 1. FIG 2 is a scanning transmission electron microscope photograph of the separation functional layer in the fluid separation membrane of Example 1.

[0013] The present invention relates to a fluid separation membrane having a separation functional layer, wherein the carbon element ratio of the separation functional layer is 40 atomic % or more and 98 atomic % or less, and the separation functional layer has voids therein with an average pore diameter of 3 nm or more and 150 nm or less.

[0014] <Fluid Separation Membrane> The fluid separation membrane of the present invention is a fluid separation membrane having a separation functional layer. A fluid separation membrane is one that can selectively permeate specific components and has a separation functional layer that performs the separation function. The fluid separation membrane of the present invention may be a free-standing membrane that does not have a porous support layer, or a composite membrane that has a porous support layer. A composite membrane with a porous support layer, i.e., a fluid separation membrane in which a separation functional layer is formed on at least a portion of the porous support layer, is preferred because it allows the separation functional layer to be made thinner while ensuring mechanical strength, thereby increasing the permeability of the fluid separation membrane.

[0015] When the fluid separation membrane of the present invention is a composite membrane having a porous support layer, the porous support layer is not particularly limited as long as it is porous, does not hinder fluid permeation, and has continuous pores, and conventionally known materials can be appropriately selected. Examples of materials suitable for the porous support layer include materials with continuous pores derived from a phase separation structure, materials with a structure in which multiple particles are connected, materials such as woven fabrics and nonwoven fabrics in which fibrous materials are folded and appropriately bonded as necessary, and materials with a co-continuous porous structure in which the voids and the material constituting the support are continuous with each other. These materials are preferably selected from the perspective of not hindering fluid permeation and performing the function of supporting the separation function layer. Among these, materials with a co-continuous porous structure are more preferred because the voids and the material constituting the porous support layer are continuous with each other and the curvature of the interface is lower than that of a particle-connected porous support layer, so they do not hinder fluid permeation, and the material constituting the porous support layer has a high stress dispersion effect, resulting in increased compressive strength.

[0016] The material of the porous support layer is not particularly limited and can be selected from conventionally known materials. Examples of such materials include porous inorganic materials such as alumina, silica, cordierite, zirconia, titania, Vycor glass, zeolite, magnesia, and sintered metal; porous organic materials containing at least one polymer selected from the group consisting of homopolymers and copolymers of polysulfone, polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide; and porous carbon materials obtained by carbonizing porous organic materials made of carbonizable resins. Thermoplastic or thermosetting resins can be used as carbonizable resins. Examples of thermoplastic resins include polyphenylene ether, polyvinyl alcohol, polyacrylonitrile, phenolic resin, aromatic polyester, polyamic acid, aromatic polyimide, aromatic polyamide, polysiloxane, polyvinylidene fluoride, cellulose acetate, polyetherimide, and copolymers thereof. Examples of thermosetting resins include unsaturated polyester resins, alkyd resins, melamine resins, urea resins, polyimide resins, diallyl phthalate resins, lignin resins, urethane resins, phenolic resins, polyfurfuryl alcohol resins, and copolymers thereof. These may be used alone or in combination. In particular, from the viewpoints of cost and productivity, it is preferable to use polyacrylonitrile or aromatic polyimide.

[0017] The material constituting the porous support layer is preferably a porous inorganic material or a porous carbon material from the viewpoints of heat resistance, chemical resistance, and mechanical strength. As the porous carbon material, a porous carbon material obtained by carbonizing a porous organic material made of a carbonizable resin is more preferable from the viewpoint of easy control of the carbon element ratio of the porous support layer described below. When the main constituent elements constituting the separation function layer and the porous support layer are the same, this is preferred because the chemical properties of the separation function layer and the porous support layer are similar and therefore the interfacial adhesion is excellent.

[0018] The constituent elements of the porous support layer are not particularly limited, but the carbon element ratio of the porous support layer is preferably 60 atomic % or more and 98 atomic % or less. A higher carbon element ratio in the porous support layer reduces the amount of functional groups contained in the porous support layer, improving chemical resistance and maintaining strength over the long term. Therefore, the carbon element ratio of the porous support layer is more preferably 70 atomic % or more. On the other hand, a lower carbon element ratio in the porous support layer reduces brittleness and increases resistance to breakage. Therefore, the carbon element ratio of the porous support layer is more preferably 95 atomic % or less. In the present invention, the carbon element ratio of the porous support layer refers to the percentage of carbon atoms when the total number of atoms of all elements calculated by wide-scan analysis using X-ray photoelectron spectroscopy is taken as 100 atomic %. For X-ray photoelectron spectroscopy measurement, the fluid separation membrane is fractured, surface contamination is removed by argon gas cluster ion etching, or the like, and the observation surface is analyzed by adjusting the measurement area to cover only the porous support layer.

[0019] <Separation functional layer> The separation functional layer in the fluid separation membrane of the present invention is a layer having a carbon element ratio of 40 atomic % or more and 98 atomic % or less and having voids with an average pore size of 3 nm or more and 150 nm or less. Here, the separation functional layer refers to a layer-like region composed of a matrix and voids and surrounded by an interface other than the boundary between the matrix and the voids, and is a region that performs the function of separating fluids.

[0020] The carbon element ratio of the separation functional layer in the fluid separation membrane of the present invention is 40 atomic % or more and 98 atomic % or less. The higher the carbon element ratio of the separation functional layer, the better the chemical resistance and the longer-term stable separation performance can be exhibited. Therefore, the carbon element ratio of the separation functional layer is preferably 55 atomic % or more, more preferably 70 atomic % or more. On the other hand, the lower the carbon element ratio of the separation functional layer, the lower the brittleness and the higher the resistance to breakage. Therefore, the carbon element ratio of the separation functional layer is preferably 95 atomic % or less, more preferably 92 atomic % or less. In addition, the carbon element ratio of the separation functional layer in the present invention means the proportion of carbon atoms when wide scan analysis is performed by X-ray photoelectron spectroscopy and the total number of atoms of all elements calculated is taken as 100 atomic %. During X-ray photoelectron spectroscopy measurement, surface contamination is removed from the separation functional layer in the fluid separation membrane by argon gas cluster ion etching or the like, and the observation surface is analyzed by adjusting the measurement range to only the separation functional layer.

[0021] The constituent elements of the separation functional layer other than carbon are not particularly limited, and may contain hydrogen, oxygen, nitrogen, boron, sulfur, silicon, etc., and may also contain alkali metals, alkaline earth metals, etc. The separation functional layer in the fluid separation membrane of the present invention preferably has a silicon element ratio of 0.1 atomic % or more and 20 atomic % or less. Since the higher the silicon element ratio of the separation functional layer, the lower the brittleness tends to be, so the silicon element ratio of the separation functional layer is more preferably 0.4 atomic % or more. On the other hand, the lower the silicon element ratio of the separation functional layer, the better the chemical resistance, so the carbon element ratio of the separation functional layer is more preferably 10 atomic % or less. In this invention, the silicon element ratio means the proportion of silicon atoms when wide scan analysis is performed by X-ray photoelectron spectroscopy and the total number of atoms of all elements calculated is taken as 100 atomic %. During X-ray photoelectron spectroscopy measurement, surface contamination is removed from the separation functional layer in the fluid separation membrane by argon gas cluster ion etching, etc., and the observation surface is analyzed by adjusting so that only the separation functional layer is the measurement area. The material for the separation functional layer in the present invention is not particularly limited as long as it has the carbon element ratio described above, and any conventionally known material can be selected as appropriate. However, from the viewpoint of ease of controlling the carbon element ratio, it is preferable that the separation functional layer be a material obtained by carbonizing an organic material made of a carbonizable resin.

[0022] The carbonizable resin may be a thermoplastic resin or a thermosetting resin. Examples of thermoplastic resins include polyphenylene ether, polyvinyl alcohol, polyacrylonitrile, phenolic resin, aromatic polyester, polyamic acid, aromatic polyimide, aromatic polyamide, polysiloxane, polyvinylidene fluoride, cellulose acetate, polyetherimide, and copolymers thereof. Examples of thermosetting resins include unsaturated polyester resin, alkyd resin, melamine resin, urea resin, polyimide resin, diallyl phthalate resin, lignin resin, urethane resin, phenolic resin, polyfurfuryl alcohol resin, and copolymers thereof. These may be used alone or in combination.

[0023] As the carbonizable resin, it is preferable to use polyphenylene ether, polyamic acid, aromatic polyimide, aromatic polyamide, polysiloxane, or polyetherimide from the viewpoint of the separation performance of the carbon membrane, and it is more preferable to use a copolymer thereof from the viewpoint of easily forming voids in the separation functional layer by forming a phase separation structure.

[0024] A dissipative resin that dissipates during the manufacturing process may be used together with the carbonizable resin. Examples of dissipative resins include polyolefins such as polyethylene, polypropylene, and polystyrene, acrylic resins, methacrylic resins, polyacetal, polyvinylpyrrolidone, aliphatic polyesters, aromatic polyesters, aliphatic polyamides, and polycarbonates. Two or more of these may be used.

[0025] When carbonizable resins generally used as precursors of separation functional layers are carbonized, it is difficult to form voids with an average pore size of 3 nm or more and 150 nm or less. If small pore size voids are present in the precursor resin layer of the separation functional layer, the layer softens and becomes fluid when the glass transition point is exceeded during the carbonization process, and deforms in a direction that reduces the specific surface area, resulting in the preferential disappearance of voids with small pore sizes, i.e., large specific surface areas. This makes it difficult to maintain voids with a pore size of 150 nm or less inside the separation functional layer after carbonization. On the other hand, if large voids with an average pore size exceeding 150 nm are present in the separation functional layer, the number of voids is substantially reduced within the separation functional layer, resulting in insufficient stress dispersion and making the fluid separation membrane more susceptible to damage due to local stress concentration, making it difficult to achieve the effects of the present invention.

[0026] In the present invention, the method for forming voids with an average pore size of 3 nm or more and 150 nm or less inside the separation functional layer is not particularly limited, but examples include a method of adding an elimination resin to the precursor resin of the separation functional layer and removing the burnt-off resin in a carbonization process, and a method of phase-separating a copolymer containing a partially thermally decomposable molecular skeleton and then carbonizing it.

[0027] The pore size of the separation functional layer can be appropriately selected depending on the material to be separated. Among the pores contained in the separation functional layer, those with a pore size of less than 3 nm are considered pores, and those with a pore size of 3 nm or more and 150 nm or less are considered voids.

[0028] The matrix of the separation functional layer preferably has pores with a pore diameter of less than 3 nm, and more preferably has pores of 0.3 nm to 2.0 nm. The peak diameter of the pores in the portion of the separation functional layer other than the voids is desirably adjusted appropriately according to the size of the substance to be separated. For example, when separating carbon dioxide and methane, the peak diameter of the pores in the separation functional layer is preferably 0.3 nm to 0.7 nm. The peak diameter of the pores in the separation functional layer in the present invention is determined in accordance with JIS Z 8831-3 (2010) by measuring the adsorption isotherm by adsorbing and desorbing carbon dioxide into the fluid separation membrane and analyzing it based on the GCMC method. Here, when the fluid separation membrane is a composite membrane having a porous support layer, the peak diameter of the pores in the separation functional layer may be evaluated by peeling off only the separation functional layer portion.

[0029] If it is difficult to calculate a clear peak diameter using the above method, the peak diameter of the pores in the separation functional layer is replaced by the pore diameter dNKP calculated based on the normalized Knudsen-based permeance method (NKP method). The NKP method is a method in which the permeabilities of many types of non-condensable gases with different molecular diameters are measured, the kinetic molecular diameter of the gas is plotted on the horizontal axis and the permeability on the vertical axis, and the pore diameter dNKP [nm] is calculated by curve fitting using (Equation 1). In this specification, four types of gases, He, Ar, N2, and CH4, are used as non-condensable gases (details are described in Lie Meng et al., Journal of Membrane Science, Vol. 496, pp. 211-218, Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University (2015)).

[0030]

[0031] The average pore size of the voids in the separation functional layer of the present invention is preferably 3 nm or more and 50 nm or less. Since a large pore size of the voids reduces pressure loss and improves fluid permeability, the average pore size of the voids is more preferably 5 nm or more, and even more preferably 10 nm or more. On the other hand, a small pore size of the voids allows the voids to be highly dispersed inside the separation functional layer, which tends to improve brittleness, so the average pore size of the voids is more preferably 30 nm or less, and even more preferably 20 nm or less.

[0032] Here, the separation functional layer in the cross section of the fluid separation membrane is observed using a technique that can observe the cross section as a two-dimensional image, such as a scanning electron microscope or a transmission electron microscope, and three fields of view are observed at a magnification that includes 30 or more voids within the observation area, excluding voids that are cut off at the edge of the observation area, and the circular equivalent diameter of each void is calculated, and the median value in each field of view is taken as the void pore size. Here, the average void pore size is taken as the arithmetic mean of the obtained medians.

[0033] The average void fraction of the separation functional layer in the cross section of the fluid separation membrane of the present invention is preferably 5% or more and 60% or less. Here, the average void fraction of the separation functional layer is calculated by observing the separation functional layer in the cross section of the fluid separation membrane using a technique that can observe the cross section as a two-dimensional image, such as a scanning electron microscope or a transmission electron microscope, at a magnification that includes 30 or more voids in the observation area, and using the following formula to define the area of ​​the entire observation area as A and the area of ​​the void portion as B.

[0034] Average void fraction (%) = B / A x 100 The higher the average void fraction, the smaller the pressure loss as a gas or liquid flow path and the higher the flow rate, while the lower the average void fraction, the stronger the material is against forces applied in the cross-sectional direction, such as compression or bending, which is advantageous for ease of handling and use under pressurized conditions. Taking these factors into consideration, it is more preferable that the average void fraction of the separation functional layer is 8% or more and 30% or less.

[0035] The shape of the fluid separation membrane of the present invention is not particularly limited, and can be any shape, such as a fiber or film. A fiber form has the advantage that a larger membrane area per unit volume can be obtained compared to a film form. In addition, since the membrane has high resistance to forces applied in the cross-sectional direction, it is possible to operate at high pressures, which is preferable because it enables highly efficient membrane separation.

[0036] When the fluid separation membrane of the present invention is fibrous, the cross-sectional shape of the fiber is not limited in any way and can be any shape, such as a round cross-section, a multi-lobed cross-section such as a triangular cross-section, a flat cross-section, or a hollow cross-section. In particular, a hollow cross-section of the fluid separation membrane, i.e., a hollow fiber shape, is preferred because it allows for pressure resistance while controlling the flow of the supplied fluid and the separated fluid. A higher area ratio of the cross-sectional area X of the hollow portion to the cross-sectional area Y of the hollow fiber (hollow area ratio: 100 × X / Y) reduces pressure loss and prevents fluid flow, while a lower ratio increases pressure resistance. From these perspectives, the hollow area ratio is preferably 5% or more and 70% or less. Here, the cross-sectional area Y of the hollow fiber is the cross-sectional area including the cross-sectional area X of the hollow portion. The hollow fiber may have multiple hollow portions, in which case the sum of the cross-sectional areas of the hollow portions is taken as the cross-sectional area X of the hollow portions. The thickness of the separation functional layer in the fluid separation membrane of the present invention is not particularly limited and can be appropriately set depending on the application, etc.

[0037] In the case of a free-standing membrane without a porous support layer, the thickness of the separation functional layer is preferably 800 μm or less, more preferably 500 μm or less, from the viewpoint of increasing fluid permeability, and is preferably 10 μm or more, more preferably 50 μm or more, from the viewpoint of ensuring mechanical strength and suppressing defects.

[0038] In the case of a composite membrane having a porous support layer, from the viewpoint of increasing fluid permeability, the thickness of the separation functional layer is preferably 5 μm or less, more preferably 3 μm or less. Furthermore, from the viewpoint of ensuring mechanical strength and suppressing defects, the thickness of the separation functional layer is preferably 0.1 μm or more, more preferably 0.3 μm or more. Here, the thickness of the separation functional layer is defined by measuring the thickness of the thinnest part constituting the separation functional layer using a microscope or the like, and is calculated as the average thickness of the separation functional layer obtained by analyzing 10 cross-sections of the fluid separation membrane.

[0039] The separation membrane module of the present invention contains the fluid separation membrane of the present invention housed in a case. The separation membrane module is formed with flow paths that control the flow of fluids and guide the fluids that have permeated the fluid separation membrane. It is preferable to use a case or a sealant for the purpose of controlling the flow of these fluids. The material of the case is not particularly limited, but is preferably selected appropriately depending on the usage environment, such as pressure resistance and heat resistance, and examples thereof include metal, resin, carbon, and composites of these.

[0040] The mixed gases and mixed liquids to be separated by the purification equipment including the separation membrane module of the present invention are not particularly limited, and examples include carbon dioxide separation and storage systems from exhaust gases of power plants, blast furnaces, etc., removal of sulfur components from gasified fuel gas in integrated coal gasification combined cycle power generation, purification of biogas and natural gas, purification of hydrogen from organic hydrides, etc. In other words, in the separation membrane module of the present invention, the fluid separation membrane is preferably a gas separation membrane.

[0041] The purification facility of the present invention includes a separation membrane module of the present invention disposed in at least a portion of a process. The purification facility preferably includes, in addition to the separation membrane module, a pretreatment facility, a purified fluid recovery facility, a by-product fluid recovery facility, etc. The pretreatment facility is a facility for removing impurities from a fluid to be separated before separation and adjusting the composition of the fluid to be separated before separation. The purified fluid recovery facility is a facility for recovering a purified fluid obtained by removing unnecessary components from the fluid to be separated before separation, and further purifying the purified fluid as necessary or supplying it to a pipeline, etc. The by-product fluid recovery facility is a facility for recovering a by-product fluid removed from the fluid to be separated before separation and, for example, discharging the by-product fluid after detoxifying it. In the purification facility of the present invention, the separation membrane module, the pretreatment facility, the purified fluid recovery facility, and the by-product fluid recovery facility are preferably connected by piping, etc., so that the fluid to be separated before separation is continuously separated into a purified fluid and a by-product fluid. The purification facility can use a combination of multiple separation membrane modules depending on the processing volume of the fluid to be separated. The number of separation membrane modules in the purification facility is preferably 10 or more from the viewpoint of enabling efficient purification, and is preferably 1000 or less from the viewpoint of downsizing and maintainability of the purification facility. The multiple separation membrane modules may be connected in series or in parallel with respect to the fluid to be separated.

[0042] A method for producing a purified fluid that at least partially uses such purification equipment may include a separate purification step or an additional step before or after the purification step in the separation membrane module of the present invention, or may produce a fluid by mixing with a purified fluid purified in a different purification step. Examples of separate purification steps or different purification steps include distillation, adsorption, and absorption. Also, examples of additional steps include component adjustment by mixing with another fluid.

[0043] The purified fluid obtained by the production method of the present invention is purified using the separation membrane module of the present invention, which has high separation performance, and therefore energy consumption in the above-mentioned additional process is reduced, making it suitable for use in various industrial applications as a fluid with low environmental impact.

[0044] <Method for Producing Fluid Separation Membrane> The method for producing a fluid separation membrane of the present invention will be specifically described using a hollow fiber fluid separation membrane having a separation functional layer made of a carbon material obtained by carbonizing a polymer compound as an example, but is not limited to this. An example of a method for producing a composite membrane having a porous support layer includes a method having a step of forming a precursor resin layer of the separation functional layer on the porous support layer (step 1) and a step of carbonizing by heating and baking (step 3). An example of a method for producing a free-standing membrane without a porous support layer includes a method having a step of molding a precursor resin of the fluid separation membrane (step 2) and a step of carbonizing by heating and baking (step 3). However, the method for producing a fluid separation membrane in the present invention is not limited to the following. [Step 1] Step 1 is a step of forming a precursor resin layer of the separation functional layer on the porous support layer when producing a composite hollow fiber membrane having a porous support layer. The material of the porous support layer is not particularly limited, and conventionally known materials can be appropriately selected. Examples include porous inorganic materials such as alumina, silica, cordierite, zirconia, titania, vycor glass, zeolite, magnesia, and sintered metal; porous organic materials containing at least one polymer selected from the group consisting of homopolymers and copolymers such as polysulfone, polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide; and porous carbon materials obtained by carbonizing porous organic materials made of carbonizable resins.

[0045] The precursor resin of the separation functional layer can be a thermoplastic resin or a thermosetting resin. Examples of thermoplastic resins include polyphenylene ether, polyvinyl alcohol, polyacrylonitrile, phenolic resin, aromatic polyester, polyamic acid, aromatic polyimide, polyimide siloxane, aromatic polyamide, polysiloxane, polyvinylidene fluoride, cellulose acetate, polyetherimide, and copolymers thereof. Examples of thermosetting resins include unsaturated polyester resin, alkyd resin, melamine resin, urea resin, polyimide resin, diallyl phthalate resin, lignin resin, urethane resin, phenolic resin, polyfurfuryl alcohol resin, and copolymers thereof. These may be used alone or in combination.

[0046] There are no particular limitations on the method for forming voids inside the separation functional layer, but examples include a method of adding an elimination resin to the separation functional layer or its precursor resin layer.

[0047] The eliminable resin is a resin that can be removed at any stage, such as after lamination of the precursor resin layer, during heating and baking, or after heating and baking. The method for removing the eliminable resin is not particularly limited, and preferred methods include chemical removal by depolymerization using chemicals, dissolution and removal by adding a solvent that dissolves the eliminable resin, and removal by lowering the molecular weight of the eliminable resin through thermal decomposition by heating. These methods can be used alone or in combination, and when combined, they can be performed simultaneously or separately.

[0048] As a chemical removal method, a method of hydrolysis using an acid or alkali is preferred from the viewpoints of economy and ease of handling. Examples of resins that are susceptible to hydrolysis by an acid or alkali include polyester, polycarbonate, and polyamide.

[0049] Preferred examples of the method of removing the eliminable resin by adding a solvent that dissolves the eliminable resin include a method in which a solvent is continuously supplied to the mixed carbonizable resin and eliminable resin to dissolve and remove the eliminable resin, and a method in which the two are mixed in a batchwise manner to dissolve and remove the eliminable resin.

[0050] Specific examples of the disappearing resin suitable for the method of removing by adding a solvent include polyolefins such as polyethylene, polypropylene, and polystyrene, acrylic resins, methacrylic resins, polyvinylpyrrolidone, aliphatic polyesters, polycarbonates, etc. Among these, amorphous resins are more preferable in terms of solubility in solvents, and examples thereof include polystyrene, methacrylic resins, and polycarbonates.

[0051] Methods for reducing the molecular weight of the eliminable resin and removing it by thermal decomposition include a method in which a mixture of the carbonizable resin and the eliminable resin is heated batchwise to cause thermal decomposition, and a method in which a mixture of the carbonizable resin and the eliminable resin is continuously supplied to a heat source and heated to cause thermal decomposition. Specific examples of such eliminable resins include polyolefins such as polyethylene, polypropylene, and polystyrene, acrylic resins, methacrylic resins, polyacetal, polyvinylpyrrolidone, polysiloxane, aliphatic polyesters, aromatic polyesters, aliphatic polyamides, and polycarbonates, and these may be used alone or in a mixed state.

[0052] The method for forming the precursor resin layer is not particularly limited, and examples include a method of coating the precursor resin on the surface of a porous support. Examples of precursor resin coating methods include dip coating, spraying, casting, and vapor deposition, with dip coating being preferred because it is a relatively easy manufacturing method. Dip coating methods are broadly divided into melting and solution methods. In the melting method, the precursor resin is melted and laminated at a temperature above its melting point, and then cooled to a temperature below its melting point to produce a fluid separation membrane. In the solution method, the precursor resin is dissolved in a solvent and laminated, and then appropriately dried to remove the solvent to produce a fluid separation membrane. In either method, additives may be added to enhance the performance of the fluid separation membrane and other high-performance features.

[0053] [Step 2] Step 2 is a step of molding a precursor resin for a fluid separation membrane when producing a free-standing hollow fiber membrane that does not have a porous support layer.

[0054] The method for molding the precursor resin is not particularly limited, but when the fluid separation membrane is fibrous, the spinning method described below can be appropriately selected. If the precursor resin is a thermoplastic resin, it can be heated to a temperature equal to or higher than the softening temperature of the resin and then melt-spinned. Furthermore, when the precursor resin is soluble in a solvent, dry spinning, dry-wet spinning, wet spinning, or the like can be appropriately selected as solution spinning.

[0055] Melt spinning is a method of forming fibers by extruding a precursor resin that has been heated and melted (in a fluidized state) using a kneading extruder or the like through a die, and then winding it up while cooling. This method is faster than solution spinning and has superior productivity. In addition, since no solvent volatilizes, the cost of safety measures during the process can be reduced, making it preferable because it allows for low-cost production.

[0056] In addition, solution spinning is a method of forming fibers by measuring a spinning dope containing a pre-prepared precursor resin and a solvent and extruding it through a spinneret, and it is possible to precisely control the phase separation state. In particular, dry-wet spinning and wet spinning using a coagulation bath are more preferred modes because they allow precise control of the phase separation state of the precursor resin by appropriately combining heat-induced phase separation, non-solvent-induced phase separation, etc., which will be described later.

[0057] The precursor resin for the fluid separation membrane can be a thermoplastic resin or a thermosetting resin. Examples of thermoplastic resins include polyphenylene ether, polyvinyl alcohol, polyacrylonitrile, phenolic resin, aromatic polyester, polyamic acid, aromatic polyimide, polyimidesiloxane, aromatic polyamide, polysiloxane, polyvinylidene fluoride, cellulose acetate, polyetherimide, and copolymers thereof. Examples of thermosetting resins include unsaturated polyester resin, alkyd resin, melamine resin, urea resin, polyimide resin, diallyl phthalate resin, lignin resin, urethane resin, phenolic resin, polyfurfuryl alcohol resin, and copolymers thereof. These may be used alone or in combination.

[0058] There are no particular limitations on the method for forming voids inside the separation functional layer of the fluid separation membrane, but examples include a method in which a elimination resin is added to a precursor resin or a spinning dope made of a precursor resin and a solvent.

[0059] The eliminable resin is a resin that can be removed at any stage, such as during or after spinning of the precursor resin, or during or after heating and baking. There are no particular limitations on the method for removing the eliminable resin, and preferred methods include chemical removal by depolymerization using chemicals, dissolution removal by adding a solvent that dissolves the eliminable resin, and removal by heating to reduce the molecular weight of the eliminable resin through thermal decomposition. These methods can be used alone or in combination, and when used in combination, they can be performed simultaneously or separately.

[0060] As a chemical removal method, a method of hydrolysis using an acid or alkali is preferred from the viewpoints of economy and ease of handling. Examples of resins that are susceptible to hydrolysis by an acid or alkali include polyester, polycarbonate, and polyamide.

[0061] Preferred examples of the method of removing the eliminable resin by adding a solvent that dissolves the eliminable resin include a method in which a solvent is continuously supplied to the mixed carbonizable resin and eliminable resin to dissolve and remove the eliminable resin, and a method in which the two are mixed in a batchwise manner to dissolve and remove the eliminable resin.

[0062] Specific examples of the disappearing resin suitable for the method of removing by adding a solvent include polyolefins such as polyethylene, polypropylene, and polystyrene, acrylic resins, methacrylic resins, polyvinylpyrrolidone, aliphatic polyesters, polycarbonates, etc. Among these, amorphous resins are more preferable in terms of solubility in solvents, and examples thereof include polystyrene, methacrylic resins, and polycarbonates.

[0063] Methods for reducing the molecular weight of the eliminable resin and removing it by thermal decomposition include a method in which a mixture of the carbonizable resin and the eliminable resin is heated batchwise to cause thermal decomposition, and a method in which a mixture of the carbonizable resin and the eliminable resin is continuously supplied to a heat source and heated to cause thermal decomposition. Specific examples of such eliminable resins include polyolefins such as polyethylene, polypropylene, and polystyrene, acrylic resins, methacrylic resins, polyacetal, polyvinylpyrrolidone, polysiloxane, aliphatic polyesters, aromatic polyesters, aliphatic polyamides, and polycarbonates, and these may be used alone or in a mixed state.

[0064] [Step 3] Step 3 is a step in which a molded body in which a precursor resin layer is laminated on the porous support layer produced in Step 1, or a molded body of the precursor resin of the fluid separation membrane produced in Step 2, is subjected to an infusibilization treatment as necessary, and then heated and baked to carbonize the precursor resin, thereby producing a fluid separation membrane.

[0065] In this step, the precursor resin is preferably heated in an inert gas atmosphere. Examples of inert gases include helium, nitrogen, and argon. The flow rate of the inert gas may be any amount that can sufficiently reduce the oxygen concentration in the heating device, and it is preferable to select an optimum value appropriately depending on the size of the heating device, the amount of raw material supplied, the carbonization temperature, and the like. There is no upper limit to the flow rate of the inert gas, but it is preferable to set it appropriately in accordance with the temperature distribution and the design of the heating device from the viewpoints of economy and minimizing temperature changes in the heating device.

[0066] Furthermore, by heating in a mixed gas atmosphere of the above-mentioned inert gas and active gas, the surface of the separation functional layer can be chemically etched, and the size of the pore diameter on the surface of the separation functional layer can be controlled. Examples of active gases include oxygen, carbon dioxide, water vapor, air, and combustion gas. The concentration of the active gas in the inert gas is preferably 0.1 ppm or more and 100 ppm or less.

[0067] The calcination temperature in this step can be set arbitrarily within a range that improves the permeation rate and separation coefficient of the separation membrane, but the calcination temperature is preferably 500°C or higher and 850°C or lower.

[0068] The precursor resin may be subjected to an infusibility treatment, if necessary, before being subjected to the carbonization treatment. The method of infusibility treatment is not particularly limited, and known methods can be used. Specific methods include a method of causing oxidative crosslinking by heating in the presence of oxygen, a method of forming a crosslinked structure by irradiating with high-energy rays such as electron beams or gamma rays, and a method of forming a crosslinked structure by impregnating and mixing a substance having a reactive group. Among these, the method of causing oxidative crosslinking by heating in the presence of oxygen is preferred because it is a simple process and can keep production costs low. These methods may be used alone or in combination, and may be used simultaneously or separately.

[0069] (Average void fraction and average void diameter of separation functional layer) Using a field emission electron microscope JEM-F200 manufactured by JEOL Ltd., the cross section of the separation functional layer of a fluid separation membrane thinned by a focused ion beam (FIB) method was observed by scanning transmission electron microscopy (STEM) at an acceleration voltage of 200 kV. STEM images were obtained at the center of the separation functional layer in the film thickness depth direction. Next, the obtained STEM images were binarized by image processing using image analysis software "MultiImageTool" (manufactured by System Infrontia Corporation) to extract voids.

[0070] After excluding voids that were cut off at the edge of the observation area, three fields of view were observed at a magnification that included 30 or more voids within the observation area, the circle equivalent diameter of each void was calculated, and the median value in each field of view was taken as the void diameter. The average void diameter was taken as the arithmetic mean of the obtained medians.

[0071] The average void fraction of the separation functional layer was calculated by observing the separation functional layer in the cross section of the fluid separation membrane in three fields of view at a magnification that included 30 or more voids within the observation area, and using the following formula, where A is the area of ​​the entire observed area and B is the area of ​​the void portion.

[0072] Average void ratio (%) = B / A x 100 (element ratio) Al Kα was measured using a scanning dual X-ray photoelectron spectrometer PHI Quantes manufactured by ULVAC-PHI, Inc. １，２Wide scan analysis was performed using an X-ray source with a 1486.6 eV X-ray beam. The ratio of carbon atoms and the ratio of silicon atoms were defined as the carbon element ratio and the silicon element ratio, respectively, when the calculated total number of atoms of all elements was taken as 100 atomic %. The observation surface was analyzed after removing surface contamination by argon gas cluster ion etching.

[0073] (Measurement of Gas Permeation Rate) Modules were fabricated using the fluid separation membranes obtained in each Example and Comparative Example, and the gas permeation rate Q was measured. Carbon dioxide and methane were used as measurement gases, and the pressure change per unit time on the permeation side of carbon dioxide and methane was measured by an external pressure method at a measurement temperature of 25°C in accordance with the pressure sensor method of JIS K7126-1 (2006). The pressure difference between the supply side and the permeation side was set to 0.11 MPa.

[0074] Next, the gas permeation rate Q was calculated using the following formula: The ratio of the gas permeation rates Q of the individual components was defined as the separation factor α. Here, the membrane area was calculated from the outer diameter and length of the region contributing to gas permeation.

[0075] Gas permeation rate Q = [permeation gas amount (nmol)] / [membrane area (m ２ ) × time (s) × pressure difference (Pa)]. The gas permeation rate Q of carbon dioxide is 30 nmol / (m ２ .Pa.s) or more, it is marked "S"; ２ ・Pa・s) or more 30nmol / (m ２ If the gas permeation rate Q is less than 10 nmol / (m ２ ・Pa・s) or more 20nmol / (m ２ If the gas permeation rate Q is less than 5 nmol / (m ２ ・Pa・s) or more 10nmol / (m ２ If the gas permeation rate Q is less than 5 nmol / (m ２ If the viscosity was less than 1.5 Pa·s, the result was rated as "D".

[0076] (Separation Factor of Carbon Dioxide and Methane) The gas permeation rates Q of carbon dioxide and methane were measured, and the separation factor of carbon dioxide and methane was calculated as (permeation rate of carbon dioxide) / (permeation rate of methane). When the separation factor of carbon dioxide and methane was 40 or more, it was judged as "S", when the separation factor was 25 or more and less than 40, it was judged as "A", when the separation factor was 15 or more and less than 25, it was judged as "B", and when the separation factor was less than 15, it was judged as "C".

[0077] (Brittleness measurement) A pressing test was performed using an indenter with a tip diameter of 10 μm in the direction perpendicular to the surface of the separation functional layer. When a load was applied, the fracture state of the pressurized part was observed using a scanning electron microscope. If no cracks were observed even at a pressure of 4 GPa, it was judged as "S", if cracks were observed at a pressure of 3 GPa or more but less than 4 GPa, it was judged as "A", if cracks were observed at a pressure of 2 GPa or more but less than 3 GPa, it was judged as "B", if cracks were observed at a pressure of 1 GPa or more but less than 2 GPa, it was judged as "C", and if cracks were observed at a pressure of less than 2 GPa, it was judged as "D". (Production Example 1) 10 parts by weight of polyacrylonitrile (PAN) (MW 150,000) manufactured by Polysciences, 10 parts by weight of polyvinylpyrrolidone (PVP) (MW 40,000) manufactured by Sigma-Aldrich, and 80 parts by weight of dimethyl sulfoxide (DMSO) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were mixed and stirred at 100°C to prepare a spinning dope.

[0078] The obtained spinning dope was cooled to 25°C, and then a concentric triple spinneret was used to simultaneously discharge an 80 wt% aqueous solution of DMSO from the inner tube, the spinning dope from the middle tube, and a 90 wt% aqueous solution of DMSO from the outer tube, and then the resulting mixture was introduced into a coagulation bath of pure water at 25°C and wound up on a roller to obtain a raw fiber. The obtained raw fiber was washed with water and then dried at 25°C for 24 hours using a circulation dryer to produce a precursor of a hollow fiber-shaped porous carbon fiber.

[0079] The obtained porous carbon fiber precursor was passed through an electric furnace at 250°C and heated in an air atmosphere for 1 hour to perform an infusible treatment, thereby obtaining an infusible yarn. Subsequently, the infusible yarn was carbonized at a carbonization temperature of 650°C to obtain a porous carbon fiber of Production Example 1 having an outer diameter of 300 μm and an inner diameter of 100 μm. Furthermore, when the cross section of the porous carbon fiber was observed, a continuous porous structure was confirmed on the inner surface. (Example 1) Using the porous carbon fiber obtained in Production Example 1 as a porous support layer, a precursor resin solution containing an aromatic polyimide copolymer and a thermally decomposable disappearing resin was applied by a dip coating method, the solvent was removed, and then the porous support layer was dried at 120°C for 3 hours in a circulating dryer, thereby obtaining a precursor of a fluid separation membrane in which a precursor resin layer was formed on the outer surface of the porous support layer. Subsequently, the fluid separation membrane precursor was calcined at 650°C in a nitrogen atmosphere to produce a fluid separation membrane.

[0080] As a result of evaluation using the above-mentioned method, the peak diameter of the pores in the separation function layer was 0.52 nm, the average pore diameter of the voids in the separation function layer was 15 nm, the average void ratio of the separation function layer was 18%, the carbon element ratio of the separation function layer was 86 atomic %, the silicon element ratio of the separation function layer was 1.2 atomic %, the film thickness of the separation function layer was 0.8 μm, and the carbon element ratio of the porous support layer was 80 atomic %.

[0081] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "S", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "S". The evaluation results are shown in Table 1.

[0082] A scanning transmission electron microscope photograph of the cross section of the obtained fluid separation membrane is shown in Figure 1. The deposited protective film was applied during the scanning transmission electron microscope observation and does not constitute the fluid separation membrane of the present invention.

[0083] FIG. 2 shows a scanning transmission electron microscope photograph of the separation functional layer in the obtained fluid separation membrane.

[0084] Example 2 A fluid separation membrane was produced in the same manner as in Example 1, except that a siloxane polymer was added to the precursor resin solution of Example 1.

[0085] The obtained fluid separation membrane had a peak pore diameter of 0.54 nm in the separation function layer, an average pore diameter of voids in the separation function layer of 19 nm, an average void ratio of 23% in the separation function layer, a carbon element ratio of 72 atomic % in the separation function layer, a silicon element ratio of 4.6 atomic % in the separation function layer, a thickness of 1.1 μm in the separation function layer, and a carbon element ratio of 82 atomic % in the porous support layer.

[0086] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "S", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "S". The evaluation results are shown in Table 1.

[0087] Example 3 A fluid separation membrane was produced in the same manner as in Example 1, except that the molecular weight of the thermally decomposable disappearing resin contained in the precursor resin solution was reduced.

[0088] The obtained fluid separation membrane had a peak pore diameter of 0.51 nm in the separation functional layer, an average pore diameter of 5 nm in the voids in the separation functional layer, an average void ratio of 12%, a carbon element ratio of 90 atomic % in the separation functional layer, a silicon element ratio of 0.5 atomic % in the separation functional layer, a thickness of 0.9 μm in the separation functional layer, and a carbon element ratio of 85 atomic % in the porous support layer.

[0089] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "A", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "S". The evaluation results are shown in Table 1.

[0090] Example 4 A fluid separation membrane was produced in the same manner as in Example 1, except that the amount of the thermally decomposable disappearing resin contained in the precursor resin solution was increased.

[0091] The obtained fluid separation membrane had a peak diameter of pores in the separation function layer of 0.54 nm, an average pore size of voids in the separation function layer of 23 nm, an average void ratio of 35%, a carbon element ratio of 78 atomic % in the separation function layer, a silicon element ratio of 0.9 atomic % in the separation function layer, a thickness of 1.3 μm in the separation function layer, and a carbon element ratio of 82 atomic % in the porous support layer.

[0092] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "S", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "A". The evaluation results are shown in Table 1.

[0093] Example 5 A fluid separation membrane was produced in the same manner as in Example 1, except that the molecular weight of the thermally decomposable eliminative resin contained in the precursor resin solution was increased and the amount of the thermally decomposable eliminative resin added was reduced.

[0094] The obtained fluid separation membrane had a peak pore diameter of 0.51 nm in the separation functional layer, an average pore diameter of 52 nm in the voids in the separation functional layer, an average void ratio of 6%, a carbon element ratio of 87 atomic % in the separation functional layer, a silicon element ratio of 0.5 atomic % in the separation functional layer, a thickness of 1.1 μm in the separation functional layer, and a carbon element ratio of 83 atomic % in the porous support layer.

[0095] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "A," a carbon dioxide / methane separation factor α of "S," and a brittleness measurement of "B." The evaluation results are shown in Table 1.

[0096] Example 6 A fluid separation membrane was produced in the same manner as in Example 1, except that a porous alumina tube having an outer diameter of 8 mm was used as the porous support layer.

[0097] The obtained fluid separation membrane had a peak pore diameter of 0.52 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 20 nm, an average void fraction of 16%, a carbon element ratio of 83 atomic %, a silicon element ratio of 0.6 atomic %, and a thickness of 1.0 μm in the separation functional layer.

[0098] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "S", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "A". The evaluation results are shown in Table 1.

[0099] Example 7 A fluid separation membrane was produced in the same manner as in Example 1, except that the amount of the thermally decomposable disappearing resin contained in the precursor resin solution was increased.

[0100] The obtained fluid separation membrane had a peak pore diameter of 0.57 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 17 nm, an average void ratio of 63% in the separation functional layer, a carbon element ratio of 81 atomic % in the separation functional layer, a silicon element ratio of 0.2 atomic % in the separation functional layer, a thickness of 1.2 μm in the separation functional layer, and a carbon element ratio of 79 atomic % in the porous support layer.

[0101] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "S", a carbon dioxide / methane separation factor α of "B", and a brittleness measurement of "B". The evaluation results are shown in Table 1.

[0102] Example 8 A fluid separation membrane was produced in the same manner as in Example 1, except that the calcination temperature of the precursor of the fluid separation membrane was increased.

[0103] The obtained fluid separation membrane had a peak diameter of pores in the separation function layer of 0.50 nm, an average pore size of voids in the separation function layer of 19 nm, an average void ratio of 25%, a carbon element ratio of 94 atomic % in the separation function layer, a silicon element ratio of 0.2 atomic % in the separation function layer, a film thickness of 1.1 μm in the separation function layer, and a carbon element ratio of 90 atomic % in the porous support layer.

[0104] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "A," a carbon dioxide / methane separation factor α of "S," and a brittleness measurement of "B." The evaluation results are shown in Table 1.

[0105] Example 9 A fluid separation membrane was produced in the same manner as in Example 1, except that the calcination temperature of the precursor of the fluid separation membrane was increased.

[0106] The obtained fluid separation membrane had a peak pore diameter of 0.49 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 14 nm, an average void ratio of 19%, a carbon element ratio of 97 atomic % in the separation functional layer, a silicon element ratio of 0.0 atomic % in the separation functional layer, a film thickness of 1.0 μm in the separation functional layer, and a carbon element ratio of 94 atomic % in the porous support layer.

[0107] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "B", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "C". The evaluation results are shown in Table 1.

[0108] Example 10 A fluid separation membrane was produced in the same manner as in Example 1, except that the calcination temperature of the precursor of the fluid separation membrane was lowered.

[0109] The obtained fluid separation membrane had a peak diameter of pores in the separation function layer of 0.54 nm, an average pore size of voids in the separation function layer of 15 nm, an average void ratio of 14%, a carbon element ratio of 60 atomic % in the separation function layer, a silicon element ratio of 0.5 atomic % in the separation function layer, a thickness of 1.2 μm in the separation function layer, and a carbon element ratio of 77 atomic % in the porous support layer.

[0110] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "A", a carbon dioxide / methane separation factor α of "A", and a brittleness measurement of "A". The evaluation results are shown in Table 1.

[0111] Example 11 A fluid separation membrane was produced in the same manner as in Example 1, except that the calcination temperature of the fluid separation membrane precursor was lowered and the amount of thermally decomposable disappearance resin added to the precursor resin solution was reduced.

[0112] The obtained fluid separation membrane had a peak pore diameter of 0.55 nm in the separation function layer, an average pore diameter of voids in the separation function layer of 12 nm, an average void ratio of 7%, a carbon element ratio of 47 atomic % in the separation function layer, a silicon element ratio of 2.6 atomic % in the separation function layer, a thickness of 1.5 μm in the separation function layer, and a carbon element ratio of 73 atomic % in the porous support layer.

[0113] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "B", a carbon dioxide / methane separation factor α of "A", and a brittleness measurement of "B". The evaluation results are shown in Table 1.

[0114] Example 12 A fluid separation membrane was produced in the same manner as in Example 1, except that a siloxane polymer was added to the coating solution of Example 1 and the calcination temperature of the precursor of the fluid separation membrane was lowered.

[0115] The obtained fluid separation membrane had a peak pore diameter of 0.52 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 27 nm, an average void ratio of 21%, a carbon element ratio of 67 atomic % in the separation functional layer, a silicon element ratio of 8.2 atomic % in the separation functional layer, a thickness of 1.2 μm in the separation functional layer, and a carbon element ratio of 80 atomic % in the porous support layer.

[0116] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "A", a carbon dioxide / methane separation factor α of "A", and a brittleness measurement of "S". The evaluation results are shown in Table 1.

[0117] Example 13 A fluid separation membrane was produced in the same manner as in Example 1, except that the thickness of the precursor resin coating in step 1 was increased.

[0118] The obtained fluid separation membrane had a peak pore diameter of 0.53 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 18 nm, an average void ratio of 20% in the separation functional layer, a carbon element ratio of 83 atomic % in the separation functional layer, a silicon element ratio of 1.4 atomic % in the separation functional layer, a thickness of 4.1 μm in the separation functional layer, and a carbon element ratio of 79 atomic % in the porous support layer.

[0119] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "B", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "S". The evaluation results are shown in Table 1.

[0120] Example 14 A fluid separation membrane was produced in the same manner as in Example 1, except that the thickness of the precursor resin coating in step 1 was increased.

[0121] The obtained fluid separation membrane had a peak pore diameter of 0.53 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 22 nm, an average void ratio of 21%, a carbon element ratio of 80 atomic % in the separation functional layer, a silicon element ratio of 2.0 atomic % in the separation functional layer, a thickness of 8.5 μm in the separation functional layer, and a carbon element ratio of 77 atomic % in the porous support layer.

[0122] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "C", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "A". The evaluation results are shown in Table 1.

[0123] Example 15 A spinning dope was prepared by reducing the solvent content of the precursor resin solution of Example 1 to increase the solids concentration, and using a concentric triple spinneret, an 80 wt % NMP aqueous solution was discharged from the inner tube, the spinning dope from the middle tube, and a 90 wt % NMP aqueous solution from the outer tube, all of which were simultaneously discharged. The spinning dope was then introduced into a coagulation bath of pure water at 25° C. and wound up on a roller to obtain a raw fiber. The obtained raw fiber was washed with water and then dried at 25° C. for 24 hours using a circulating dryer to produce a hollow fiber precursor for a fluid separation membrane.

[0124] The fluid separation membrane precursor was then passed through an electric furnace at 250° C. and heated in an air atmosphere for 1 hour to effect infusibilization, and then fired at 650° C. in a nitrogen atmosphere to produce a fluid separation membrane.

[0125] The obtained fluid separation membrane had a peak pore diameter of 0.54 nm in the separation functional layer, an average pore diameter of voids in the separation functional layer of 16 nm, an average void fraction of 20% in the separation functional layer, a carbon element ratio of 84 atomic %, a silicon element ratio of 0.6 atomic %, and a thickness of 52 μm in the separation functional layer.

[0126] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "D", a carbon dioxide / methane separation factor α of "S", and a brittleness measurement of "A". The evaluation results are shown in Table 1.

[0127] Comparative Example 1 A fluid separation membrane was produced in the same manner as in Example 1, except that no thermally decomposable disappearance resin was added to the precursor resin solution and the skeleton of the aromatic polyimide copolymer was partially changed.

[0128] The separation functional layer of the obtained fluid separation membrane had no voids with a pore size of 3 nm or more and 150 nm or less. The peak pore diameter of the separation functional layer was 0.52 nm, the carbon element ratio of the separation functional layer was 85 atomic %, the silicon element ratio of the separation functional layer was 0.3 atomic %, the thickness of the separation functional layer was 1.2 μm, and the carbon element ratio of the porous support layer was 82 atomic %.

[0129] The resulting fluid separation membrane had a carbon dioxide gas permeation rate Q of "D", a carbon dioxide / methane separation factor α of "A", and a brittleness measurement of "D". The evaluation results are shown in Table 1.

[0130]

[0131] The fluid separation membrane of the present invention can be suitably used in carbon dioxide separation and storage systems from exhaust gases of power plants, blast furnaces, etc., removal of sulfur components from gasified fuel gas in integrated coal gasification combined cycle power generation, purification of biogas and natural gas, and hydrogen purification from organic hydrides.

[0132] 1: Separation functional layer 2: Porous support layer 3: Deposition protective film 4: Void 5: Matrix

Claims

1. A fluid separation membrane having a separation functional layer, wherein the carbon element ratio of the separation functional layer is 40 atomic % or more and 98 atomic % or less, and the separation functional layer has voids therein having an average pore diameter of 3 nm or more and 150 nm or less.

2. The fluid separation membrane according to claim 1, wherein the average void ratio of the separation functional layer is 5% or more and 60% or less.

3. The fluid separation membrane according to claim 1, wherein the average pore size of the voids is 3 nm or more and 50 nm or less.

4. The fluid separation membrane according to claim 1, wherein the separation functional layer has a peak pore diameter of 0.3 nm or more and 2.0 nm or less.

5. The fluid separation membrane according to claim 1, wherein the average void ratio of the separation functional layer is 8% or more and 30% or less.

6. The fluid separation membrane according to claim 1, wherein the carbon element ratio of said separation functional layer is 55 atomic % or more and 95 atomic % or less.

7. The fluid separation membrane according to claim 1, wherein the silicon element ratio of said separation functional layer is from 0.1 atomic % to 20 atomic %.

8. The fluid separation membrane according to claim 1, wherein the separation functional layer is formed on at least a portion of a porous support layer.

9. The fluid separation membrane according to claim 8, wherein the thickness of the separation functional layer is from 0.1 μm to 5 μm.

10. The fluid separation membrane according to claim 8, wherein the carbon element ratio of said porous support layer is 60 atomic % or more and 98 atomic % or less.

11. The fluid separation membrane of claim 8, wherein the porous support layer has a bicontinuous pore structure.

12. The fluid separation membrane of claim 1, wherein said fluid separation membrane is in the form of a hollow fiber.

13. The fluid separation membrane of claim 1, wherein said fluid separation membrane is a gas separation membrane.

14. A separation membrane module having the fluid separation membrane according to claim 1 in a case.

15. A purification facility comprising the separation membrane module according to claim 14.

16. A biogas or natural gas purification facility comprising the separation membrane module according to claim 14.

17. A purification facility comprising a combination of 10 to 1,000 separation membrane modules according to claim 14.

18. A purified fluid separated using the separation membrane module according to claim 14.

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