Gas separation membranes and gas separation membrane modules

Abstract

A gas separation membrane that has a separation function layer in at least one part thereof. The gas separation layer has a fibrous or film-like shape. The separation function layer comprises a matrix and particles.　Provided are a gas separation membrane and a gas separation membrane module that prevent damage to the gas separation membrane during operation, have long-term stability, and can exhibit excellent separation characteristics.

Description

[Technical Field]

[0001] The present invention relates to a gas separation membrane and a gas separation membrane module. [Background technology]

[0002] Membrane separation is known as a separation method for selectively separating and purifying specific components from various mixed gases. Compared to other separation and purification methods, membrane separation utilizes pressure and concentration differences, which means it uses less thermal energy and is therefore more energy-efficient, drawing attention. However, gas separation processes require heat and chemical resistance, and there have been challenges in finding a stable supply of gas separation membranes that can meet these requirements. [Prior art documents] [Patent documents]

[0003] Patent Document 1 describes a separation membrane made of a polymer matrix and a carbon nanotube nonwoven fabric.

[0004] Patent Document 2 discloses a material in which carbon is used as a matrix and various materials are added as reinforcing materials. [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-237127 [Patent Document 2] Special Publication No. 2011-527231 Summary of the Invention [Problem to be solved by the invention]

[0005] The separation membrane disclosed in Patent Document 1 can ensure mechanical durability by reinforcing the polymer matrix with a nonwoven fabric, but due to the low heat resistance of the polymer matrix, its heat resistance as a gas separation membrane is insufficient.

[0006] The separation membrane disclosed in Patent Document 2 has the problem that simply combining the matrix and reinforcing material tends to cause peeling at the interface, resulting in breakdown during long-term operation and making stable operation impossible due to gas leakage.

[0007] An object of the present invention is to provide a gas separation membrane and a gas separation membrane module that can prevent damage to the gas separation membrane during operation and can stably exhibit excellent separation performance for a long period of time. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the gas separation membrane of the present invention has the following configuration: A gas separation membrane having a separation function layer at least in a portion thereof, The shape of the gas separation membrane is hollow fiber It is in the form The separation functional layer is a gas separation membrane made of a matrix and particles, the matrix being a carbonized polymer compound, and the carbon element ratio of the matrix being 70 atomic % or more and 100 atomic % or less.

[0009] The gas separation membrane module of the present invention has the following configuration: The gas separation membrane module has the above gas separation membrane housed in a case.

[0010] The gas separation membrane of the present invention preferably contains particles at least some of which have an aspect ratio of 10 or more.

[0011] In the gas separation membrane of the present invention, it is preferable that the absolute value of the orientation coefficient F of particles having an aspect ratio of 10 or more relative to the reference axis is 0.1 or more and 1.0 or less.

[0012] In the gas separation membrane of the present invention, the particles are preferably fibrous.

[0013] In the gas separation membrane of the present invention, the particles are preferably flat.

[0014] In the gas separation membrane of the present invention, the content of particles in the separation functional layer is preferably 10% by volume or less.

[0015] In the gas separation membrane of the present invention, the orientation coefficient F of particles having an aspect ratio of 10 or more relative to the reference axis is preferably +0.1 or more and +1.0 or less.

[0016] In the gas separation membrane of the present invention, the volume ratio of particles that exist independently without contacting other particles to the total volume of all particles is preferably 1% by volume or more.

[0017] The gas separation membrane of the present invention is preferably in the form of a fiber.

[0018] In the gas separation membrane of the present invention, the carbon element ratio of the matrix is ​​preferably 70 atomic % or more and 100 atomic % or less, and when the carbon element ratio of the matrix is ​​X (atomic %) and the carbon element ratio of the particle is Y (atomic %), it is preferable that (|XY| / X) × 100 is 30% or less.

[0019] In the gas separation membrane of the present invention, the matrix is ​​a carbonized polymer compound. do.

[0020] In the gas separation membrane of the present invention, the particles are preferably one or more selected from the group consisting of carbon black, graphite, expanded graphite, carbon nanohorns, carbon nanoribbons, carbon nanotubes, graphene, graphene oxide, and fullerenes. [Effects of the Invention]

[0021] The present invention provides a gas separation membrane and a gas separation membrane module that are capable of suppressing breakage of the gas separation membrane and exhibiting excellent separation performance stably for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention provides a gas separation membrane having a separation functional layer at least in a portion thereof, the gas separation membrane being in a fibrous or film form, and the separation functional layer being composed of a matrix and particles.

[0023] <Gas separation membrane> The gas separation membrane of the present invention has a separation functional layer at least in part. "Having a separation functional layer at least in part" refers to a state in which a layered portion having a separation function (separation functional layer) forms at least a part of the material, and the portion where the separation functional layer is not formed is sufficient as a portion without a separation function as long as it is in a state in which it can control the flow of gas. "A state in which it can control the flow of gas" refers to a state in which gas is substantially impermeable, and the permeability of nitrogen gas as a standard is 0.01 nmol / (m 2 sPa).

[0024] The separation functional layer constituting the gas separation membrane of the present invention is composed of a matrix and particles. The matrix in the separation functional layer refers to the sea portion of a so-called sea-island structure. The particles in the separation functional layer refer to the island portion of the so-called sea-island structure. A conventionally known method can be appropriately applied to determine the sea-island structure, and any method may be selected as long as it can rationally separate the sea portion and the island portion.

[0025] The material of the matrix is ​​not particularly limited, but the carbon element ratio X is preferably 70 atomic % or more and 100 atomic % or less. do.

[0026] The larger the carbon element ratio X of the matrix, the more excellent the film performance, chemical resistance, and heat resistance, and therefore it is preferable that the carbon element ratio X is 80 atomic % or more.

[0027] On the other hand, the smaller the carbon content, the more flexible and resistant to breakage the matrix becomes, and therefore the longer-term durability improves. Therefore, the carbon element ratio X of the matrix is ​​preferably 99 atomic % or less, and more preferably 92 atomic % or less.

[0028] The constituent elements of the matrix 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 above element ratios can be determined by various analytical methods, and can be analyzed using energy dispersive X-ray spectroscopy, etc.

[0029] It is also used in matrices charcoal As the base material, a carbide of a polymer compound is used from the viewpoint that it is easy to control the carbon element ratio X of the matrix mentioned above. This is what we aim to achieve.For example, the resin may be obtained by baking a polymer compound containing at least one of the thermoplastic resins and thermosetting resins. In particular, it is preferable to select phenol resin, polyacrylonitrile, polyimide, etc.

[0030] Here, having a separation function means having the ability to create a difference in permeation rate for gases, and refers to a separation factor of 1.2 or more based on the permeation rate ratio between CO2 and CH4 (CO2 / CH4).

[0031] The particles, when combined with the matrix, have the effect of suppressing damage to the separation functional layer. In addition, it is also a preferred embodiment that the particles further have a gas permeability function or a gas separation function, as long as they can exert the effect of suppressing damage to the separation functional layer.

[0032] The material of the particles is not particularly limited, but the closer the carbon element ratio Y of the particles is to the carbon element ratio X of the matrix, the better the adhesion to the matrix and the greater the tendency for strength to be improved. From this perspective, (|XY| / X) × 100, an index of the similarity of the carbon element ratios between the matrix and the particles, is preferably 30% or less. (|XY| / X) × 100 is preferably 20% or less, and more preferably 0% to 10%. Here, the constituent elements other than carbon are not particularly limited, provided that the above-mentioned effects are exhibited, but may contain oxygen, nitrogen, boron, sulfur, silicon, etc., as well as alkali metals, alkaline earth metals, etc. The above elemental amounts are analyzed by applying energy dispersive X-ray spectroscopy or the like to a transmission electron microscope capable of observing minute regions of the matrix and particles, and adjusting appropriately so that signals are detected so that elemental ratios can be calculated for all elements except hydrogen.

[0033] The particles used in the gas separation membrane of the present invention preferably have a carbon element ratio Y of 60 atomic % or more and 100 atomic % or less. A larger carbon element ratio Y is preferable because it results in better membrane performance, chemical resistance, and heat resistance, and is more preferably 70 atomic % or more, and even more preferably 80 atomic % or more. On the other hand, a smaller carbon element ratio tends to result in greater flexibility and resistance to breakage, thereby improving the effect of preventing breakage of the membrane, which ensures long-term durability, so the carbon element ratio Y of the particles is more preferably 99 atomic % or less.

[0034] The particles used in the gas separation membrane of the present invention can be selected from various materials such as polymer compounds, biological materials, inorganic materials, etc., and can be used alone or in combination. When the particles of the present invention are polymer compounds, examples of the polymer compounds include polyester, polyamide, polyimide, polyether, polyphenylene sulfide, polyether ether ketone, and copolymers mainly composed of these.

[0035] The particles used in the gas separation membrane of the present invention are preferably made of an inorganic material. Inorganic materials tend to have a high elastic modulus, which makes them more likely to exhibit a reinforcing effect when combined with a matrix, and they also tend to have high heat resistance and chemical resistance. Examples of inorganic materials include, but are not limited to, carbon compounds such as silicon carbide, boron carbide, and carbon nitride, and materials primarily composed of carbon elements. These materials may be used in combination, such as by coating the surface of the material with carbon to satisfy the carbon element ratio.

[0036] Furthermore, the particles in the separation functional layer constituting the gas separation membrane of the present invention are preferably one or more selected from the group consisting of carbon black, graphite, expanded graphite, carbon nanohorns, carbon nanoribbons, carbon nanotubes, graphene, graphene oxide, and fullerenes. These materials are easy to make the carbon element ratio similar to that of the matrix, and therefore are likely to exhibit a reinforcing effect when combined with the matrix. Among these materials, from the viewpoint of their large specific surface area and the tendency to increase the adhesive interface that exhibits the reinforcing effect of the matrix constituting the separation functional layer by the particles, one or more selected from the group consisting of carbon black, carbon nanohorns, carbon nanoribbons, carbon nanotubes, graphene, graphene oxide, and fullerenes is more preferred, and one or more selected from the group consisting of carbon black, carbon nanotubes, graphene, graphene oxide, and fullerenes is even more preferred from a cost perspective.

[0037] Furthermore, it is preferable that at least a portion of the particles contained in the separation functional layer of the present invention have an aspect ratio of 10 or greater. Because a larger average aspect ratio facilitates the combined effect of the matrix and particles, the average aspect ratio of the particles is more preferably 300 or greater, even more preferably 800 or greater, and particularly preferably 1,500 or greater. While there is no particular upper limit to the average aspect ratio of the particles, it is preferable that the average aspect ratio of the particles in the separation functional layer be 2,000 or less, in order to facilitate fine dispersion of the particles in the separation functional layer and, particularly when forming the separation functional layer using a liquid, to form a uniform separation functional layer while maintaining the fluidity of the liquid. Here, the aspect ratio is calculated by extracting a single particle dispersed in a matrix using a 3D microscope and calculating the ratio (Ll / Ls) of the length Ls of the shortest portion to the length Ll of the longest portion from the 3D data of the particle. The length Ls of the shortest portion generally corresponds to the thickness of the thinnest portion in the case of graphene, for example, and the diameter of the thinnest portion in the case of carbon nanotubes. Furthermore, the length Ll of the longest part is measured by extracting the part of the flat plate shape where the longest distance can be measured using the edge as the reference, and for carbon nanotubes, it corresponds to the length from end to end of a single bent carbon nanotube. The 3D microscopy is not particularly limited as long as it allows for separation and observation of the matrix and particles, but it is preferable to appropriately select an analytical method that allows for separation, observation, and analysis of the matrix and particles as electronic information, such as slice & view, which cuts out cross sections with an ion beam and then observes them successively with a scanning electron microscope, or a method using a transmission electron microscope to apply computed tomography.

[0038] The shape of the particles of the present invention is not particularly limited, but the particle shape is preferably fibrous or tabular.

[0039] When a liquid coating process is employed during the formation of the separation functional layer, fibrous particles tend to be oriented in the flow direction, and this orientation provides reinforcement in a specific direction, particularly in the fiber axis direction, while improving bending rigidity in the direction perpendicular to the fiber axis, making them preferable. Examples of fibrous particles include cellulose nanofibers, carbon nanohorns, carbon nanoribbons, carbon nanotubes, synthetic resin fibers, glass fibers, carbon fibers, silicon carbide fibers, metal fibers, and whiskers.

[0040] On the other hand, when a liquid coating process is used to form the separation functional layer, flat particles tend to be oriented in the flow direction, and when the orientation direction is the MD, they tend to exhibit reinforcement in both the MD and TD directions, making them preferable. Examples of flat particles include graphene, graphene oxide, talc, and mica.

[0041] When the separation functional layer of the present invention contains particles with an aspect ratio of 10 or more, it is preferable that the absolute value of the orientation coefficient F of the particles with an aspect ratio of 10 or more relative to the reference axis is 0.1 or more and 1.0 or less. Orienting the particles in a specific direction is a preferred embodiment, as it facilitates the development of a reinforcing effect when combined with a matrix. While the direction in which the particles are oriented is arbitrary, it is preferable to appropriately devise a manufacturing method so that the particles are oriented in the direction in which the most reinforcing effect is required. When a method of forming the separation functional layer using a liquid is selected, any orientation state can be set by forming the separation functional layer while flowing the liquid along the set orientation direction.

[0042] Here, the orientation coefficient F of the particles in the separation functional layer of the present invention is F=(3cos 2φ is expressed as φ-1) / 2, where φ is the orientation angle, and focusing on a single particle extracted by three-dimensional microscopic photography of the separation functional layer described above, the three-dimensional data is approximately fitted to an ellipsoid using the least squares method, and the major axis of the obtained ellipsoid is defined as D. If the shape of the gas separation membrane of the present invention is fibrous, the fiber axis is used as the reference axis, and the orientation angle φ is calculated from the projection length Dcosφ of the major axis D of the ellipsoid onto the reference axis. Furthermore, if the shape of the gas separation membrane of the present invention is film-like, the normal to the film surface is used as the reference axis, and the major axis of the obtained ellipsoid is defined as D. Then, the ellipsoid is rotated 90° from the major axis D in the direction of the shortest minor axis of the ellipsoid, with the center of the ellipsoid as the reference, and the orientation angle φ is calculated from the projection length Dcosφ of the major axis D of the ellipsoid onto the reference axis.

[0043] Here, the orientation coefficient F is such that +1.0 indicates full orientation, -0.5 indicates perpendicular orientation, and 0.0 indicates no orientation, and can quantitatively express the orientation state of the particles.

[0044] Here, the orientation coefficient F is calculated for particles with an aspect ratio of 10 or more. Ten particles with an aspect ratio of 10 or more are selected at random, and the orientation coefficient is calculated for each particle relative to the same reference axis, and the average of the 10 points is defined.

[0045] When the gas separation membrane of the present invention has a fibrous shape, if the particles in the separation functional layer are oriented within the separation functional layer, breakage can be suppressed when tensile force is applied to the separation functional layer due to vibration of the gas flow during operation, etc., and therefore the absolute value of the orientation coefficient F of the particles relative to the reference axis is preferably 0.1 or more and 1.0 or less, and more preferably 0.2 or more and 1.0 or less.

[0046] Furthermore, when the gas separation membrane of the present invention is in the form of a film, if the particles in the separation functional layer are oriented within the separation functional layer, breakage can be suppressed when tensile force is applied to the separation functional layer due to vibration of the gas flow during operation, etc., and therefore the absolute value of the orientation coefficient F of the particles relative to the reference axis is preferably 0.1 or more and 1.0 or less, and more preferably 0.2 or more and 1.0 or less.

[0047] Furthermore, when the gas separation membrane of the present invention has a fibrous shape, the orientation coefficient F of the particles relative to the reference axis is preferably +0.1 or more and +1.0 or less. The higher the orientation coefficient F, the more the particles are oriented in the fiber axis direction, which serves as the reference axis, relative to the reference axis. This makes it easier for the particles to exert a reinforcing effect on the separation function layer, and is particularly effective in reinforcing the fiber in the tensile direction, making it possible to provide a gas separation membrane that can be operated stably for long periods of time without damage or breakage. For this reason, the orientation coefficient F is more preferably +0.2 or more and +1.0 or less, even more preferably +0.5 or more and +1.0 or less, and particularly preferably +0.65 or more and +1.0 or less.

[0048] Furthermore, when the gas separation membrane of the present invention is in the form of a film, the orientation coefficient F of the particles relative to the reference axis is preferably +0.1 or more and +1.0 or less. The higher the orientation coefficient F, the more the particles are oriented relative to the reference axis, making it easier to exhibit the reinforcing effect of the particles on the separation function layer, and particularly the reinforcing effect against external forces from the normal direction of the film surface is excellent, making it possible to provide a gas separation membrane that can be operated stably for long periods of time without breakage, which is preferable. For this reason, the orientation coefficient F is more preferably +0.2 or more and +1.0 or less, even more preferably +0.5 or more and +1.0 or less, and particularly preferably +0.65 or more and +1.0 or less.

[0049] In addition, in the separation functional layer constituting the gas separation membrane of the present invention, the elastic modulus of the particles is preferably higher than that of the matrix. When the elastic modulus of the particles is higher than that of the matrix, the effect of preventing damage to the separation functional layer when combined is exerted, thereby preventing damage during operation as a gas separation membrane and enabling stable use for a long period of time.

[0050] Here, the elastic modulus of the particles being higher than that of the matrix means that the ratio of the elastic modulus of the particles to that of the matrix (hereinafter referred to as the elastic modulus ratio) is in the range of 10 to 20000. The higher the elastic modulus of the particles, the easier it is to obtain a reinforcement effect and prevent breakage, but on the other hand, the lower the elastic modulus of the particles, the more flexibly they deform and the more they can absorb instantaneous impact forces, so the elastic modulus ratio is more preferably 200 to 15,000.

[0051] The elastic modulus ratio is defined as the ratio of the elastic modulus of the point showing the highest elastic modulus to the point showing the lowest elastic modulus in the elastic modulus mapping image obtained by observing a 1 μm × 1 μm area of ​​the cross section of the separation functional layer using an atomic force microscope, and the point showing the lowest elastic modulus and forming a sea is taken as the elastic modulus of the matrix. The average value of the elastic modulus ratios obtained by analyzing the elastic modulus ratios at each observation point for 10 or more samples is taken as the elastic modulus ratio in this invention.

[0052] The surfaces of the particles used in the present invention may be chemically modified with carboxyl groups, amide groups, etc., which is preferable because the chemical bonds further improve adhesion to the matrix. On the other hand, the fewer functional groups on the surface of the particles, the better the chemical resistance. Therefore, it is preferable that the ratio of O═CO components derived from carboxyl groups and O═CN components derived from amide bonds to the total bond components of carbon elements is 0.1% to 30%.

[0053] The particles in the separation functional layer constituting the gas separation membrane of the present invention may be of one type, or two or more types may be used in combination. When two or more types of particles are used in combination, it is preferable to contain particles with an aspect ratio of 10 or more. The larger the amount of particles with an aspect ratio of 10 or more added, the easier it is to obtain the combined effect of the matrix and the particles, so it is preferable. With a total of 100% by volume of all particles, the content of particles with an aspect ratio of 10 or more is more preferably 50% by volume or more, and even more preferably 80% by volume or more.

[0054] In the separation functional layer constituting the gas separation membrane of the present invention, the volume ratio of particles that exist apart from other particles to the total volume of all particles is preferably 1% by volume or more, and more preferably 5% by volume or more. When the volume ratio of particles that exist independently without contact with other particles is within the above preferred range, the combined effect of the matrix and the particles is easily obtained.

[0055] In the gas separation membrane of the present invention, the volume percentage of particles that exist independently and are not in contact with other particles is determined by identifying particles that exist independently and are not in contact with other particles from the three-dimensional data of particles extracted by three-dimensional microscopic photography of the separation functional layer described above, and calculating their volume percentage. Taking variation into consideration, data containing 10 or more particles is used. If there are not 10 or more particles in one data point, data obtained from another observation field is added, and the separation functional layer containing a total of 10 or more particles is observed to determine the volume percentage.

[0056] Among the particles that exist independently without contacting other particles, it is preferable to include particles with an aspect ratio of 10 or more, as this makes it easier to increase the adhesive interface that exerts the strengthening effect of the matrix that constitutes the separation functional layer by the particles.

[0057] The size of the particles in the separation functional layer is not particularly limited, but it is preferable that the length Ls of the shortest part is 0.3 nm or more and 10 μm or less. When Ls is 0.3 nm or more, handling is easy while ensuring a sufficient specific surface area. On the other hand, when Ls is 10 μm or less, the specific surface area is large and adhesion to the matrix is ​​improved, thereby improving the strength of the separation membrane. From the above viewpoint, Ls of the particles is preferably 0.3 nm or more and 1 μm or less, and more preferably 1 nm or more and 100 nm or less.

[0058] The particle content in the separation functional layer constituting the gas separation membrane of the present invention is not particularly limited, but a content of 10% by volume or less per 100% by volume of the separation functional layer is preferred because it provides a sufficient matrix reinforcement effect. A low particle content improves particle dispersion in the matrix, which may result in a separation functional layer with excellent membrane thickness uniformity. On the other hand, a high content increases the particle content per unit volume of the separation functional layer, which may facilitate the reinforcement effect and improve the strength of the separation functional layer. From these perspectives, the particle content in the separation functional layer is more preferably 0.3 to 9% by volume, and even more preferably 0.5 to 5% by volume.

[0059] Here, the particle content in the separation functional layer constituting the gas separation membrane of the present invention is defined as the volume percentage of particles in the volume of the separation functional layer within the observation field, based on the three-dimensional data of the particles extracted by three-dimensional microscopic photography of the separation functional layer described above.

[0060] The thickness of the separation functional layer constituting the gas separation membrane of the present invention is not particularly limited, but a thicker layer is preferable because it is more resistant to damage from external forces and allows for stable use of the separation membrane for a long period of time, while a thinner layer is preferable because it reduces fluid permeation resistance and increases throughput per unit area. From these perspectives, the thickness of the separation functional layer is preferably in the range of 100 nm to 1,000 μm, and more preferably in the range of 200 nm to 10 μm. 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 obtained by analyzing 10 cross-sections of the gas separation membrane.

[0061] The gas separation membrane of the present invention may be a so-called composite membrane having a support supporting the separation functional layer in addition to the separation functional layer. In a composite membrane, the support supporting the separation functional layer ensures mechanical strength and durability, preventing breakage during actual use and enabling stable operation for a long period of time. In addition, even when high pressure is applied, the support is effective in bearing the pressure, making it possible to provide a gas separation membrane that can be operated in a high-pressure environment.

[0062] Here, the support is not particularly limited as long as it is a material that does not hinder gas permeation and also functions to support the separation functional layer, and conventionally known porous materials can be appropriately selected. Examples of porous materials suitable for the support include materials with closed cells derived from a sea-island structure, materials with a structure in which multiple particles are connected, nonwoven fabrics in which fibrous materials are folded over and, if necessary, moderately bonded, and materials with a continuous pore structure in which voids and the material constituting the support are continuous with each other. These materials are preferably selected appropriately from the perspective of not hindering fluid permeation and functioning to support the separation functional layer. Among these, materials with a continuous pore structure are more preferred because, since the voids and the material constituting the support are continuous with each other, they do not hinder gas permeation and are highly effective in dispersing stress resulting from the pressure exerted on the separation functional layer by the material constituting the support, resulting in increased pressure resistance of the gas separation membrane.

[0063] The shape of the gas separation membrane of the present invention is not particularly limited, and can be any shape, such as a fiber or film. A fibrous gas separation membrane has the advantage of being able to have a larger membrane area per unit volume than a film-like shape. Furthermore, 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 gas membrane separation.

[0064] When the gas 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 gas separation membrane having a hollow cross-section, i.e., a hollow fiber shape, is preferred because it allows for pressure resistance while controlling the flow of the supplied gas and the separated gas. When the gas separation membrane is shaped like a hollow fiber, a higher hollow ratio is preferred because it reduces pressure loss and does not interfere with the gas flow, while a lower hollow ratio is preferred because it increases pressure resistance. From these perspectives, a hollow ratio is preferably in the range of 10 to 90%, more preferably 20 to 60%. The hollow fiber may have a single hollow portion or multiple hollow portions.

[0065] The gas separation membrane module of the present invention is a configuration in which the gas separation membrane of the present invention is housed in a case. The gas separation membrane module is formed with a flow path that controls the flow of mixed gases and guides gas that has permeated the gas separation membrane. It is preferable to use a case or a sealant for the purpose of controlling the flow of these gases. 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. [Example]

[0066] EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these. Evaluations in each example and comparative example were carried out by the following methods. (gas separation membrane module) A gas separation membrane module was created by bundling 20 10 cm long gas separation membranes together and placing them in an acrylic pipe case (inner diameter 12 mm, wall thickness 3 mm). The ends of the bundled fluid separation membranes were fixed to the inner surface of the case with an epoxy resin adhesive and both ends of the case were sealed. (Gas separation membrane rupture rate in pressure / decompression tests) Five gas separation membrane modules were prepared for each Example and Comparative Example, and it was confirmed that the gas separation membrane had no rupture during fabrication. The presence or absence of rupture in the gas separation membrane was evaluated as follows. If rupture in the gas separation membrane was visually observed through the acrylic pipe case, it was determined that there was a rupture. If no rupture was visually observed, all but one of the inlet and outlet ports for the gas to be separated of the gas separation membrane module was sealed, and the entire gas separation membrane module was immersed in water with compressed air of 0.2 MPaG supplied through the unsealed inlet and outlet port for the gas to be separated. If bubbles were generated from the opening of the gas separation membrane, it was determined that there was a rupture, and if no bubbles were generated, it was determined that there was no rupture.

[0067] For each gas separation membrane module that showed no rupture, a pressure-decompression test was conducted in which 10 sets of operations were repeated, each set consisting of supplying compressed air at 2.0 MPaG to the supply side, holding the pressure for 1 minute, and then releasing to atmospheric pressure. After the pressure-decompression test, the presence or absence of rupture in the gas separation membrane was again determined, and the percentage of modules with ruptures out of five gas separation membrane modules was taken as the gas separation membrane rupture rate. (Decrease in separation factor after pressure / decompression test) The gas permeation rate of the gas separation membrane module before the pressure-decompression test was measured, and the separation factor was calculated based on the ratio of the CO2 and CH4 permeation rates (CO2 / CH4). The pressure-decompression test was then performed, and one gas separation membrane module that had not been fractured during the test was randomly selected and its gas permeation rate was measured again to calculate the separation factor. The rate of decrease in the separation factor before and after the pressure-decompression test was calculated as 1 - (separation factor after pressure-decompression test / separation factor before pressure-decompression test). A rate of decrease in the separation factor of less than 0.1 was judged "excellent," a rate of decrease of 0.1 to less than 0.3 was judged "good," and a rate of decrease of 0.3 or more was judged "passable."

[0068] The gas permeation rate was measured by external pressure at a measurement temperature of 25°C in accordance with the pressure sensor method of JIS K 7126-1 (2006), measuring the pressure change per unit time on the permeation side for CO2 and CH4. Here, the pressure difference between the feed side and the permeation side was set to 0.11 MPa (82.5 cmHg). Next, the permeation rate Q of the permeated gas was calculated using the following formula, and the separation factor α was calculated as the ratio of the permeation rates of the gases of each component. Note that STP means standard conditions. The membrane area was calculated from the outer diameter and length of the fluid separation membrane in the region contributing to gas permeation.

[0069] Permeation rate Q = [gas permeation flow rate (cm 3 ·STP)] / [Membrane area (cm 2 ) x time (s) x pressure difference (cmHg) The ratio of the gas permeation rates Q of CO2 and CH4, (permeation rate of CO2) / (permeation rate of CH4), was calculated as the separation factor α. [Preparation Example 1] Preparation of 10.0 wt% aromatic polyimide (PI) solution and slurry Aromatic polyimide (hereinafter referred to as aromatic PI) "Matrimid (registered trademark)" 5218 was dissolved in N-methylpyrrolidone (NMP) to prepare a 10.0 wt % aromatic polyimide solution (hereinafter referred to as aromatic PI solution).

[0070] Here, "Matrimid®" 5218 is a condensation product of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 5(6)-amino-1-(4'-aminophenyl)-1,3,3'-trimethylindane.

[0071] Carbon nanotube powder (FT7000 series manufactured by CNano) was added to the prepared aromatic PI solution to a concentration of 0.30% by volume, followed by the addition of a dispersant. The mixture was then stirred and dispersed using a rotation-revolution mixer to prepare a slurry. [Preparation Example 2] Preparation of 10.0 wt% polyacrylonitrile (PAN) solution and slurry Polyacrylonitrile (PAN) (MW 150,000) was dissolved in dimethyl sulfoxide (DMSO) to prepare a 10.0 wt % PAN solution.

[0072] Carbon nanotube powder (FT7000 series manufactured by CNano) was added to the prepared PAN solution to a concentration of 0.35% by volume, and a dispersant was then added. The mixture was stirred and dispersed using a rotation-revolution mixer to prepare a slurry. [Preparation Example 3] Preparation of 10.0 wt% cellulose acetate solution and slurry Cellulose acetate (acetylation degree 55%) was dissolved in N-methylpyrrolidone (NMP) to prepare a 10.0 wt % cellulose acetate solution. Chopped polyethylene terephthalate (PET) fibers were added to the prepared cellulose acetate solution to a concentration of 0.40% by volume, and a dispersant was then added. The mixture was stirred and dispersed using a rotation-revolution mixer to prepare a slurry. [Preparation Example 4] Preparation of 8.0 wt% aromatic PI solution and slurry Aromatic PI "Matrimid (registered trademark)" 5218 was dissolved in N-methylpyrrolidone (NMP) to prepare an 8.0 wt % aromatic PI solution.

[0073] Carbon nanotube powder (FT7000 series manufactured by CNano) was added to the prepared aromatic PI solution to a concentration of 0.03% by volume, followed by the addition of a dispersant. The mixture was then stirred and dispersed using a rotation-revolution mixer to prepare a slurry. [Example 1] 10 parts by weight of polyacrylonitrile (PAN) (MW 150,000), 10 parts by weight of polyvinylpyrrolidone (PVP) (MW 40,000), and 80 parts by weight of dimethyl sulfoxide (DMSO) were mixed and stirred at 100°C to prepare a spinning dope.

[0074] The obtained spinning dope was cooled to 25°C, and then a concentric triple spinneret was used to simultaneously discharge an 80 wt% aqueous DMSO solution from the inner tube, the spinning dope from the middle tube, and a 90 wt% aqueous DMSO solution from the outer tube.Then, the spinning dope was introduced into a coagulation bath and wound up on a roller to obtain a raw fiber, which was then dried in a circulating hot air dryer to produce a hollow fiber-shaped porous carbon support precursor.

[0075] The porous carbon support precursor was then passed through an electric furnace and heated in an air atmosphere to perform an infusibilization treatment. The infusibilized fibers were then carbonized to produce hollow fiber-shaped porous carbon supports. Both the outer and inner surfaces (the surfaces of the hollow portions) of the produced porous carbon support were open, and when the cross section of the hollow fiber was observed, a bicontinuous porous structure was observed.

[0076] A porous carbon support was immersed in the slurry prepared in Preparation Example 1 and then withdrawn at a rate of 10 mm / min by dip coating. The support was then immersed in water to remove the solvent, and dried in a circulating hot air dryer to obtain a coated yarn in which an aromatic PI containing carbon nanotubes was laminated on the surface of the porous carbon support. The coated yarn was then carbonized at 700°C to produce a gas separation membrane in which a carbon membrane, whose precursor was an aromatic PI containing carbon nanotubes, was laminated on the surface of the porous carbon support.

[0077] Three-dimensional data obtained by 3D microscopy of the separation functional layer of the gas separation membrane revealed a particle content of 3.1% by volume, an average particle aspect ratio of 1,725, an orientation coefficient F of particles with an aspect ratio of 10 or more relative to the reference axis of +0.76, an absolute value of the orientation coefficient F of particles with an aspect ratio of 10 or more relative to the reference axis of 0.76, a volume fraction of particles with an aspect ratio of 10 or more of 98%, and a volume fraction of particles that exist independently without contact with other particles of 43% by volume. The average aspect ratio was calculated by averaging the aspect ratios of 10 randomly selected particles that exist independently without contact with other particles. Furthermore, elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope revealed that the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.6%, with (|XY| / X) × 100 being 9.2%.

[0078] The rate of breakage of the gas separation membrane in the pressure-decompression test was 0, and the rate of decrease in the separation factor after the pressure-decompression test was "excellent." The evaluation results are shown in Table 1.

[0079] [Table 1]

[0080] [Example 2] A gas separation membrane module was produced in the same manner as in Example 1, except that in the preparation of the slurry in Preparation Example 1, the carbon nanotube powder was added at 0.02% by volume.

[0081] At this time, from the 3D data obtained by 3D microscopic photography of the separation functional layer, the particle content was 0.2 volume %, the average particle aspect ratio was 1,648, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.78, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.78, the volume fraction of particles with an aspect ratio of 10 or more was 97%, and the volume fraction of particles that existed independently without contact with other particles was 35 volume %. Furthermore, elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope revealed that the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.5%, and in this case (|XY| / X) × 100 was 9.1%.

[0082] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.2, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are also shown in Table 1. [Example 3] A gas separation membrane module was produced in the same manner as in Example 1, except that the pulling speed in the dip coating method was changed to 5 mm / min and the carbonization temperature of the coated yarn was changed to 600°C.

[0083] At this time, from the 3D data obtained by 3D microscopic photography of the separation functional layer, the particle content was 3.7 volume %, the average particle aspect ratio was 1,773, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.57, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.57, the volume fraction of particles whose aspect ratio was 10 or more was 99%, and the volume fraction of particles that existed independently without contact with other particles was 39 volume %. Furthermore, from elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, the carbon element ratio X of the matrix was 86.4%, and the carbon element ratio Y of the particles was 98.7%, and in this case (|XY| / X) × 100 was 14.2%.

[0084] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.0, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are also shown in Table 1. [Example 4] A gas separation membrane module was produced in the same manner as in Example 1, except that the slurry prepared in Preparation Example 2 was used instead of Preparation Example 1, the pull-up speed in the dip coating method was changed to 5 mm / min, and the carbonization temperature of the coated yarn was changed to 600°C.

[0085] At this time, 3D data obtained by 3D microscopy of the separation functional layer showed that the particle content was 3.4 volume %, the average particle aspect ratio was 1,680, the orientation coefficient F of particles with an aspect ratio of 10 or more relative to the reference axis was +0.54, the absolute value of the orientation coefficient F of particles with an aspect ratio of 10 or more relative to the reference axis was 0.54, the volume fraction of particles with an aspect ratio of 10 or more was 98%, and the volume fraction of particles that existed independently without contact with other particles was 36 volume %.In addition, elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope showed that the carbon element ratio X of the matrix was 78.2%, and the carbon element ratio Y of the particles was 98.5%, and in this case (|XY| / X) × 100 was 26.0%.

[0086] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.2, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are also shown in Table 1. [Example 5] A gas separation membrane module was produced in the same manner as in Example 1, except that the slurry prepared in Preparation Example 3 was used instead of Preparation Example 1, the pull-up speed in the dip coating method was changed to 5 mm / min, and the coated yarn was used as a gas separation membrane without being carbonized.

[0087] At this time, 3D data obtained by 3D microscopy of the separation functional layer showed that the particle content was 4.2% by volume, the average particle aspect ratio was 1,592, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.55, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.55, the volume fraction of particles with an aspect ratio of 10 or more was 97%, and the volume fraction of particles that existed independently without contact with other particles was 31% by volume. Furthermore, elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope showed that the carbon element ratio X of the matrix was 61.4%, and the carbon element ratio Y of the particles was 71.6%, and in this case (|XY| / X) × 100 was 16.6%.

[0088] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.2, and the rate of decrease in the separation factor after the pressure-decompression test was "acceptable." The evaluation results are also shown in Table 1. [Example 6] A gas separation membrane module was produced in the same manner as in Example 1, except that in the preparation of the slurry in Preparation Example 1, carbon black powder was added instead of carbon nanotube powder.

[0089] At this time, from the 3D data obtained by 3D microscopic photography of the separation functional layer, the particle content was 2.9 volume %, the average aspect ratio of the particles was 6, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.08, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.08, the volume fraction of particles with an aspect ratio of 10 or more was 3%, and the volume fraction of particles that existed independently without contact with other particles was 35 volume %. Furthermore, from elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 99.1%, and in this case (|XY| / X) × 100 was 9.7%.

[0090] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.6, and the rate of decrease in the separation factor after the pressure-decompression test was "acceptable." The evaluation results are also shown in Table 1. [Example 7] A gas separation membrane module was produced in the same manner as in Example 1, except that in the preparation of the slurry in Preparation Example 1, a powder mixture of carbon nanotubes and carbon black in a weight ratio of 2:1 was added instead of carbon nanotube powder.

[0091] At this time, 3D data obtained by 3D microscopic photography of the separation functional layer showed that the particle content was 3.4 volume %, the average particle aspect ratio was 1,173, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.48, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.48, the volume fraction of particles with an aspect ratio of 10 or more was 73%, and the volume fraction of particles that existed independently without contact with other particles was 30 volume %. Furthermore, elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope showed that the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.7%, and in this case (|XY| / X) × 100 was 9.3%.

[0092] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.2, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are shown in Table 2.

[0093] [Table 2]

[0094] [Example 8] A gas separation membrane module was produced in the same manner as in Example 1, except that in the preparation of the slurry in Preparation Example 1, a powder mixture of carbon nanotubes and carbon black in a weight ratio of 1:2 was added instead of carbon nanotube powder, and a homogenizer was used instead of a rotation-revolution mixer for stirring and dispersing during the preparation of the slurry.

[0095] At this time, from the three-dimensional data obtained by three-dimensional microscopic photography of the separation functional layer, the particle content was 3.6 volume %, the average aspect ratio of the particles was 655, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.08, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.08, the volume fraction of particles whose aspect ratio was 10 or more was 3%, and the volume fraction of particles that existed independently without contact with other particles was 35 volume %. Furthermore, from elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.7%, and in this case (|XY| / X) × 100 was 9.3%.

[0096] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.4, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are also shown in Table 2. [Example 9] A gas separation membrane module was prepared in the same manner as in Example 1, except that the slurry prepared in Preparation Example 4 was used instead of Preparation Example 1, and the pull-up speed in the dip coating method was changed to 2 mm / min.

[0097] At this time, 3D data obtained by 3D microscopy of the separation functional layer showed that the particle content was 0.4 volume %, the average particle aspect ratio was 1,581, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.18, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.18, the volume fraction of particles with an aspect ratio of 10 or more was 98%, and the volume fraction of particles that existed independently without contact with other particles was 39 volume %. Furthermore, elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope showed that the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.5%, and in this case (|XY| / X) × 100 was 9.1%.

[0098] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.4, and the rate of decrease in the separation factor after the pressure-decompression test was "excellent." The evaluation results are also shown in Table 2. [Example 10] A gas separation membrane module was produced in the same manner as in Example 1, except that in the preparation of the slurry in Preparation Example 1, the weight of the carbon nanotube powder added was increased and a homogenizer was used instead of a rotation-revolution mixer for stirring and dispersing during the preparation of the slurry.

[0099] At this time, from the 3D data obtained by 3D microscopic photography of the separation functional layer, the particle content was 8.3 volume %, the average particle aspect ratio was 1,624, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.54, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.54, the volume fraction of particles with an aspect ratio of 10 or more was 99%, and the volume fraction of particles that existed independently without contact with other particles was 0.7 volume %. Furthermore, elemental analysis using an energy dispersive X-ray spectrometer attached to the transmission electron microscope revealed that the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.6%, and in this case (|XY| / X) × 100 was 9.2%.

[0100] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.4, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are also shown in Table 2. [Example 11] A gas separation membrane module was produced in the same manner as in Example 1, except that in the preparation of the slurry in Preparation Example 1, graphene powder was added instead of carbon nanotube powder.

[0101] At this time, from the 3D data obtained by 3D microscopic photography of the separation functional layer, the particle content was 3.2 volume %, the average aspect ratio of the particles was 592, the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was +0.62, the absolute value of the orientation coefficient F of particles whose aspect ratio relative to the reference axis was 10 or more was 0.62, the volume fraction of particles with an aspect ratio of 10 or more was 97%, and the volume fraction of particles that existed independently without contact with other particles was 38 volume %. Furthermore, from elemental analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, the carbon element ratio X of the matrix was 90.3%, and the carbon element ratio Y of the particles was 98.1%, and in this case (|XY| / X) × 100 was 8.6%.

[0102] The rupture rate of the gas separation membrane in the pressure-decompression test was 0.0, and the rate of decrease in the separation factor after the pressure-decompression test was "good." The evaluation results are also shown in Table 2. [Comparative Example 1] A gas separation membrane module was produced in the same manner as in Example 1, except that the carbon nanotube powder in the solution of Preparation Example 1 was not added.

[0103] At this time, the three-dimensional data obtained by three-dimensional microscopic photography of the separation functional layer did not contain any particles.

[0104] The gas separation membrane rupture rate in the pressure-decompression test was 1.0, and all five gas separation membrane modules fabricated were unable to separate gas due to "present" gas separation membrane rupture, making it impossible to evaluate the separation factor after the pressure-decompression test. The evaluation results are also shown in Table 2. [Industrial Applicability]

[0105] The gas separation membrane module of the present invention can suppress rupture of the gas separation membrane during operation of the gas separation membrane module without impairing the gas separation function, and the use of the module of the present invention is not particularly limited, but it can be preferably used, for example, 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.

Claims

1. A gas separation membrane having a separation function layer at least in a portion thereof, The gas separation membrane has a hollow fiber shape, The separation functional layer is a gas separation membrane consisting of a matrix and particles, the matrix being a carbonized polymer compound, the carbon element ratio of the matrix being 70 atomic % or more and 100 atomic % or less, and at least some of the particles having an aspect ratio of 10 or more.

2. 2. The gas separation membrane according to claim 1, wherein the absolute value of the orientation coefficient F of particles having an aspect ratio of 10 or more relative to the reference axis is 0.1 or more and 1.0 or less.

3. 3. The gas separation membrane according to claim 1, wherein the particles are fibrous.

4. 3. The gas separation membrane according to claim 1, wherein the particles are flat.

5. 5. The gas separation membrane according to claim 1, wherein the content of particles in the separation functional layer is 10% by volume or less.

6. 6. The gas separation membrane according to claim 1, wherein the orientation coefficient F of particles having an aspect ratio of 10 or more relative to a reference axis is +0.1 or more and +1.0 or less.

7. 7. The gas separation membrane according to claim 1, wherein the volume ratio of particles that exist independently without contact with other particles to the total volume of all particles is 1% by volume or more.

8. When the carbon element ratio of the matrix is ​​X (atomic %) and the carbon element ratio of the particle is Y (atomic %), (|X-Y| / X) × 100 The gas separation membrane according to any one of claims 1 to 7, wherein the porosity is 30% or less.

9. The gas separation membrane according to any one of claims 1 to 8, wherein the particles are one or more selected from the group consisting of carbon black, graphite, expanded graphite, carbon nanohorns, carbon nanoribbons, carbon nanotubes, graphene, graphene oxide, and fullerenes.

10. A gas separation membrane module having the gas separation membrane according to any one of claims 1 to 9 housed in a case.

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