Gas Separation Method

Abstract

To provide a novel method for separating fluorocarbons.SOLUTION: A method for separating a fluorocarbon gas includes supplying, to a porous membrane, a mixed gas that contains two or more types of fluorocarbon gases having molecular diameters different from each other, and separating a gas composition or a single gas in which the mixing ratio of one type of fluorocarbon gas selected from the two or more types of fluorocarbon gases is improved. The porous membrane contains zeolite.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a gas separation method and apparatus. [Background technology]

[0002] As a method for separating fluorocarbons, a method of distilling a mixture of fluorocarbons is known. Patent Document 1 describes a method of mixing a mixture containing 2,3,3,3-tetrafluoropropene and hexafluoropropene with an extraction solvent to obtain a mixture for extraction, and then distilling the mixture for extraction to obtain a distillate containing hexafluoropropene as a main component and a distillate containing 2,3,3,3-tetrafluoropropene. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-002602 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to provide a new method for separating fluorocarbon gases. [Means for solving the problem]

[0005] The present disclosure provides the following aspects. [1] The method includes supplying a mixed gas containing two or more fluorocarbon gases having different molecular diameters to a porous membrane, and separating a gas composition or a single gas in which a mixture ratio of one fluorocarbon gas selected from the two or more fluorocarbon gases is improved; The method for separating fluorocarbon gases, wherein the porous membrane contains zeolite. [2] The method for separating a fluorocarbon gas according to [1], wherein the average pore diameter of the porous membrane is 2 Å or more and 10 Å or less. [3] The method for separating a fluorocarbon gas according to [1] or [2], wherein the porous membrane includes a porous membrane formed by a hydrothermal synthesis method. [4] The method for separating a fluorocarbon gas according to any one of [1] to [3], wherein the zeolite comprises one or more types selected from the group consisting of A-type zeolite, CHA-type zeolite, and ZSM-5-type zeolite. [5] The method for separating a fluorocarbon gas according to any one of [1] to [4], wherein the molecular diameter of the one kind of fluorocarbon gas is 2 Å or more and 7 Å or less. [6] The method for separating fluorocarbon gases according to any one of [1] to [5], wherein a difference between a molecular diameter of the one fluorocarbon gas and a molecular diameter of the other fluorocarbon gas is 0.1 Å or more and 3 Å or less. [7] The method for separating a fluorocarbon gas according to any one of [1] to [6], wherein the mixed gas is supplied to the porous membrane at a temperature of 20° C. or higher and 300° C. or lower. [8] The method for separating a fluorocarbon gas according to any one of [1] to [7], wherein the mixed gas is supplied to the porous membrane under a differential pressure of 0.1 MPa or more. [9] The method for separating a fluorocarbon gas according to any one of [1] to [8], wherein the porous membrane further includes a porous support.

[10] The method for separating a fluorocarbon gas according to any one of [1] to

[10] , wherein the mixed gas contains difluoromethane and pentafluoroethane.

[11] The method for separating a fluorocarbon gas according to any one of [1] to

[10] , wherein supplying the mixed gas to the porous membrane includes permeating at least a part of the mixed gas through the porous membrane.

[12] A porous membrane is provided, The porous membrane comprises zeolite, which separates a gas composition having an improved mixture ratio of one fluorocarbon gas from a mixed gas containing two or more fluorocarbon gases having different molecular diameters, or a single gas. Effect of the Invention

[0006] According to the present invention, a new method for separating fluorocarbon gases can be provided. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating a separation device in one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (First embodiment: gas separation method) The gas separation method of the present disclosure includes: The method includes supplying a mixed gas containing two or more fluorocarbon gases having different molecular diameters to a porous membrane and separating one fluorocarbon gas selected from the two or more fluorocarbon gases; The porous membrane contains zeolite.

[0009] The present disclosure can provide a new method and apparatus for separating fluorocarbons. Fluorocarbons are used as mixed gases for refrigerants and other applications, and attempts have been made to separate them by distillation, but distillation requires a large energy load and separation is difficult due to azeotropy and the like. In addition, since the difference in molecular diameter between various fluorocarbons is small, it is not easy to efficiently separate and regenerate them even by membrane separation.

[0010] As a method for separating fluorocarbons, for example, a method using a silicone resin as described in JP-A-1-42444 and a method using a fluorine-based resin as described in Journal of Membrane Science 652 (2022) 120467 are also known. However, in these methods, separation is performed by utilizing the dissolution-diffusion effect in which the gas to be separated dissolves in the membrane itself, and the effect of the pores of the separation medium is small. The separation method in the present disclosure differs from conventional separation methods in that fluorocarbon gas is permeated through the pores of zeolite, which is a separation medium, and gas separation is performed by the molecular sieve effect. Therefore, according to the present disclosure, a new separation method for fluorocarbons can be provided.

[0011] (mixed gas) The mixed gas contains two or more kinds of fluorocarbon gases, and the two or more kinds of fluorocarbon gases have different molecular diameters. The fluorocarbon gases may be typically gaseous (gaseous) fluorocarbons at 1 atmosphere and room temperature (25° C.).

[0012] The fluorocarbon is a compound containing a carbon atom and a fluorine atom bonded to the carbon atom, and representative examples include hydrochlorofluorocarbons, hydrofluorocarbons, and hydrofluoroolefins.

[0013] Examples of the hydrochlorofluorocarbon include chlorodifluoromethane and chlorotrifluoroethane.

[0014] Examples of the hydrofluorocarbon include hydrofluorocarbons having one carbon atom, such as difluoromethane; hydrofluorocarbons having two carbon atoms, such as difluoroethane (e.g., 1,1-difluoroethane, 1,2-difluoroethane, particularly 1,1-difluoroethane), trifluoroethane (e.g., 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, particularly 1,1,1-trifluoroethane), tetrafluoroethane (e.g., 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, particularly 1,1,1,2-tetrafluoroethane) and pentafluoroethane; and hydrofluorocarbons having three carbon atoms, such as tetrafluoropropene and hexafluoropropene.

[0015] Examples of hydrofluoroolefins include 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z; DR-2), and trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E).

[0016] The fluorocarbon may preferably have 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms.

[0017] Among the fluorocarbons contained in the mixed gas, the content of fluorocarbons having 1 to 5 carbon atoms may be, for example, 80 mol % or more and 100 mol % or less, or 90 mol % or more and 100 mol % or less, based on the total amount of fluorocarbons.

[0018] The two or more kinds of fluorocarbon gases may include, for example, a fluorocarbon having one carbon atom and a fluorocarbon having two carbon atoms, preferably difluoromethane and pentafluoroethane, and more preferably difluoromethane and pentafluoroethane. In another embodiment, the two or more kinds of fluorocarbon gases may include a fluorocarbon having one carbon atom and a fluorocarbon having three carbon atoms, preferably difluoromethane (R32) and tetrafluoropropene (particularly, 2,3,3,3-tetrafluoropropene, R1234yf), and more preferably difluoromethane (R32) and tetrafluoropropene (particularly, 2,3,3,3-tetrafluoropropene, R1234yf).

[0019] The two or more fluorocarbon gases have different molecular diameters.

[0020] In one embodiment, the molecular diameter of one type of fluorocarbon (fluorocarbon to be separated) contained in the mixed gas is preferably 2 Å or more and 7 Å or less, more preferably 3 Å or more and 5 Å or less, and even more preferably 3.2 Å or more and 4.4 Å or less. The molecular diameter of one type of fluorocarbon (fluorocarbon to be separated) contained in the mixed gas is preferably 2 Å or more, more preferably 3 Å or more, and even more preferably 3.2 Å or more, and may be preferably 7 Å or less, more preferably 5 Å or less, and even more preferably 4.4 Å or less.

[0021] In the same embodiment, the molecular diameter of the other fluorocarbon contained in the mixed gas is, for example, more than 4 Å, and may be 4.2 Å or more and 10 Å or less, or 4.4 Å or more and 8 Å or less. Also, the molecular diameter of the carbon of the other fluorocarbon contained in the mixed gas may be, for example, more than 4 Å, preferably 4.2 Å or more, and may be, for example, 10 Å or less, preferably 8 Å or less.

[0022] In the same embodiment, the difference in molecular diameter between one fluorocarbon and another fluorocarbon contained in the mixed gas may be preferably 0.1 Å or more, more preferably 0.2 Å or more and 3 Å or less, and even more preferably 0.3 Å or more and 2 Å or less.

[0023] The molecular diameter of the fluorocarbon gas may be a value calculated by the following formula, assuming that the shape of the fluorocarbon molecule is a hard sphere. d=(ma / (3×2 1 / 2 ηπ)) 1 / 2 …(x1) In the formula (x1), d represents the molecular diameter, m represents the mass of one molecule, a represents the molecular velocity, and η represents the viscosity coefficient. a is calculated using the following formula: a = (γRT / M) 1 / 2 …(x2) where γ is the specific heat ratio, approximated as 1.333, R is the gas constant, T is the absolute temperature, and M is the molar mass. Alternatively, η may be measured by the capillary method.

[0024] The molecular diameter of the fluorocarbon contained in the mixed gas may be preferably 2 Å or more and 10 Å or less, and more preferably 3 Å or more and 8 Å or less.

[0025] The amount of permeation of 1 fluorocarbon contained in the mixed gas through the zeolite is preferably 10 -10 (mol / (m 2 ·s·Pa) or more 10 -4 (mol / (m 2 s·Pa) or less, more preferably 10 -9 (mol / (m 2 ·s·Pa) or more 10 -5 (mol / (m 2 s Pa) or less, more preferably 10 -8 (mol / (m 2 ·s·Pa) or more 10 -6 (mol / (m 2 s Pa).

[0026] The boiling points of the fluorocarbons contained in the mixed gas may be, at 1 atmospheric pressure, for example, preferably from −80° C. to −20° C., more preferably from −60° C. to −30° C., and even more preferably from −50° C. to −30° C. In addition, the difference in boiling point between one fluorocarbon and another fluorocarbon contained in the mixed gas may be, at 1 atmospheric pressure, for example, preferably from 0° C. to 20° C., and more preferably from 0° C. to 10° C.

[0027] The mixed gas may be an azeotropic mixture or a pseudo-azeotropic mixture of fluorocarbons. According to the gas separation method of the present disclosure, even if it is an azeotropic mixture or a pseudo-azeotropic mixture, a specific fluorocarbon can be separated. Examples of such azeotropic mixtures or pseudo-azeotropic mixtures include mixtures in which the difference between the boiling point of the fluorocarbon to be separated and the boiling point of the other fluorocarbon is 1°C or more and 20°C or less, or even 3°C or more and 18°C ​​or less.

[0028] The content of fluorocarbon in the mixed gas may be, for example, 80 mol % or more and 100 mol % or less, or 90 mol % or more and 100 mol % or less, based on the total amount of the mixed gas.

[0029] The mixed gas may contain other compounds in addition to fluorocarbons. The boiling points of such other compounds may be, for example, −100° C. or lower, or −150° C. or lower. Such other compounds are typically contained in the mixture as gases.

[0030] The other compounds include nitrogen, oxygen, carbon dioxide, water, and the like.

[0031] In one embodiment, the gas separation method of the present disclosure may include supplying a mixed gas containing difluoromethane and pentafluoroethane to a porous membrane to separate difluoromethane. (Porous membrane) The porous membrane is a membrane having a plurality of pores and contains zeolite. Zeolite is typically a porous metal oxide based on aluminosilicate, and any zeolite that has been assigned a framework code by the International Zeolite Society can be used.

[0032] Specific examples of the above zeolite include A-type, ferrierite, MCM-22, ZSM-5, mordenite, L-type, Y-type, X-type, and beta-type, and preferred examples include A-type, CHA-type, and ZSM-5-type.

[0033] In one embodiment, the formula of the zeolite is M n+ 2 / n O (Al2O3) (SiO2) x yH2O (wherein M n+ represents an n-valent metal cation, n represents an integer of 1 to 5, x represents an integer of 2 or more, for example, an integer of 2 to 10, and y represents an integer of 1 or more, for example, an integer of 1 to 50).

[0034] The silica / alumina ratio in the zeolite may be preferably 1.25 or more and 100 or less, more preferably 5 or more and 50 or less, and even more preferably 10 or more and 30 or less. The silica / alumina ratio is determined by the above formula M n+ 2 / n O (Al2O3) (SiO2) x -y corresponds to x in H2O.

[0035] The average pore diameter of the zeolite pores may be preferably 2 Å or more and 10 Å or less, more preferably 3 Å or more and 8 Å or less, and even more preferably 3 Å or more and 6 Å or less. When the average pore diameter of the zeolite pores is in this range, the separation efficiency of the fluorocarbon gas can be increased.

[0036] The average pore size of the pores in the above-mentioned zeolite can be calculated by measuring the nitrogen gas adsorption / desorption isotherm and using the BJH method based on the pressure and the amount of nitrogen adsorbed and desorbed.

[0037] The porosity of the zeolite can be calculated by measuring the nitrogen gas adsorption / desorption isotherm and using the t-plot method based on the pressure and the amount of nitrogen adsorbed and desorbed.

[0038] The thickness of the zeolite in the porous membrane may be preferably 0.1 μm or more and 100 μm or less, more preferably 0.5 μm or more and 50 μm or less, and further preferably 1 μm or more and 10 μm or less.

[0039] The porous membrane may include a zeolite and may further include a porous support. In such an embodiment, the porous membrane may include a porous support and a zeolite disposed on the porous support, and preferably includes a porous support and a porous zeolite membrane disposed on the porous support.

[0040] The porous membrane includes a porous support, which can enhance the stability of the porous membrane. In addition, when a mixed gas is supplied to the porous membrane, the permeability of the mixed gas to the zeolite membrane can be increased, which is expected to enhance the separation efficiency.

[0041] The porous support may be either an inorganic porous support or an organic porous support.

[0042] Such an inorganic porous support may preferably be composed of an inorganic material such as silica, alumina, zirconia, silicon carbide, silicon nitride, and mixtures thereof. More preferably, the inorganic porous support may be a porous alumina support.

[0043] The organic porous support may preferably be made of a heat-resistant polymer. Examples of such heat-resistant polymers include polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyimide, polytetrafluoroethylene, polyvinylidene fluoride, and derivatives thereof. In the present disclosure, a heat-resistant polymer may be understood as a polymer having a glass transition temperature of 100° C. or higher, and preferably a polymer having a glass transition temperature of 200° C. or higher.

[0044] The average pore size of the pores in the porous support may be preferably 10 nm or more and 500 nm or less, more preferably 15 nm or more and 300 nm or less, and even more preferably 20 nm or more and 200 nm or less.

[0045] The porous membrane may further include a porous intermediate layer between the porous support and the zeolite. By including such a porous intermediate layer, the continuity of the pore size between the zeolite and the porous support can be improved, and it is expected that the permeability of the mixed gas in the porous membrane can be further increased.

[0046] The porous intermediate layer may be made of either an inorganic material or an organic material, and is preferably made of an inorganic material. Examples of such inorganic materials include silica, alumina, zirconia, silicon carbide, silicon nitride, and mixtures thereof. Examples of the organic material include heat-resistant polymer materials, and specific examples thereof include polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyimide, polytetrafluoroethylene, polyvinylidene fluoride, and derivatives thereof.

[0047] The average pore size of the pores in the porous intermediate layer may be preferably 0.5 nm or more and 30 nm or less, more preferably 0.7 nm or more and 20 nm or less, and even more preferably 1 nm or more and 10 nm or less.

[0048] In the present disclosure, when the porous membrane includes a porous support or an intermediate layer, the average pore diameter of the porous membrane means the average pore diameter of the zeolite pores, and the pore diameter of the porous support or intermediate layer is not taken into consideration in the measurement and calculation of the average pore diameter of the porous membrane.

[0049] The method for producing such a porous membrane includes a hydrothermal synthesis method. Typically, in the hydrothermal synthesis method, a raw material composition containing a silicon compound, an aluminum compound, a metal compound (but not containing a silicon compound or an aluminum compound), water, and a structure directing agent used as necessary is subjected to a hydrothermal synthesis reaction to synthesize a zeolite. During the hydrothermal synthesis reaction, seed crystals may be present.

[0050] As the silicon compound, silica sol, fumed silica, precipitated silica, aluminosilicate, alkoxysilane, etc. can be used.

[0051] As the aluminum compound, aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminosilicate, metallic aluminum, pseudoboehmite, alumina sol, aluminum alkoxide, etc. can be used.

[0052] As the metal compound, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, etc. can be used.

[0053] Examples of the structure-directing agent that can be used include structure-directing agents that direct CHA-type zeolites, such as N,N,N-trialkyladamantanammonium cation, N,N,N-trimethylbenzylammonium cation, N-alkyl-3-quinuclidinol cation, N,N,N-trialkylexoaminonorbornane cation, and N,N,N-trialkylcyclohexylammonium cation, N,N,N-trimethylbenzylammonium cation, N,N,N-trialkylcyclohexylammonium cation; structure-directing agents that direct ZSM-5-type zeolites, such as tetrapropylammonium cation, tetraethylammonium cation; and structure-directing agents that direct A-type zeolites, such as tetramethylammonium cation.

[0054] The above silicon compound, aluminum compound, metal compound, water and, if necessary, a structure directing agent can be used appropriately depending on the desired structure of the zeolite.

[0055] The temperature of the hydrothermal synthesis reaction may be preferably 80°C or higher and 200°C or lower, more preferably 100°C or higher and 180°C or lower, and further preferably 120°C or higher and 160°C or lower.

[0056] The hydrothermal synthesis reaction is preferably carried out in a closed vessel.

[0057] In one embodiment, when the porous membrane includes a porous support and / or an intermediate layer, the porous membrane can be produced by applying zeolite seed crystals onto the porous support and / or the intermediate layer, and immersing the porous support and / or the intermediate layer to which the seed crystals have been applied in the raw material composition to perform hydrothermal synthesis.

[0058] (Contact method) By supplying a mixed gas containing the fluorocarbon gas to the porous membrane, at least one type of fluorocarbon gas can permeate the pores of the porous membrane and separate the fluorocarbon gas. The fluorocarbon gas can be supplied to the porous membrane as a gas (vapor).

[0059] In one embodiment, the method allows the porous membrane to selectively permeate only a specific fluorocarbon gas, so that the specific fluorocarbon gas can be separated from a mixed gas containing two or more fluorocarbon gases. In a preferred embodiment, the method allows the separation of a fluorocarbon gas having one carbon atom from a mixed gas containing two or more fluorocarbon gases having different molecular diameters.

[0060] The mixed gas may be supplied to the porous membrane by, for example, a column method, which can be carried out by fixing the porous membrane to a vessel (column) and flowing the mixed gas into the vessel (column).

[0061] In one embodiment, the temperature during the above supply may be, for example, 5° C. or higher and 500° C. or lower, and further may be 10° C. or higher and 300° C. or lower. The pressure (gauge pressure) during the above supply may be 0.05 MPaG or higher and 20 MPaG or lower, and may be 0.1 MPaG or higher and 10 MPaG or lower. When the pressure during the supply is within the above range, the fluorocarbon can easily permeate the porous membrane, the separation efficiency can be improved, and the pore structure of the porous membrane can be maintained.

[0062] The flow rate of the mixed gas may be 0.001 kg / hour or more and 1,000 kg / hour / minute or less, 0.005 kg / hour or more and 500 kg / hour or less, and further 0.01 kg / hour or more and 100 kg / hour or less.

[0063] By recovering only the fluorocarbon gas that has permeated the porous membrane, a specific fluorocarbon gas can be recovered. In this embodiment, the method for separating a fluorocarbon gas according to the present disclosure can also be understood as a method for recovering a fluorocarbon gas.

[0064] (Second embodiment: composite material) The technical scope of the present disclosure also includes a composite material containing the porous membrane and a fluorocarbon. By supplying the mixed gas to the porous membrane, at least a part of the fluorocarbon contained in the mixed gas can remain in the porous membrane, and such a composite material can be produced.

[0065] The fluorocarbon and the porous membrane in this embodiment have the same meaning as the fluorocarbon and the porous membrane in the first embodiment.

[0066] In such a composite material, the fluorocarbon preferably includes a fluorocarbon having one carbon atom, and more preferably includes one or more types selected from chlorodifluoromethane and difluoromethane.

[0067] In a preferred embodiment, the content of fluorocarbons having one carbon atom in the composite material is greater than the content of fluorocarbons having two or more carbon atoms, and more preferably, the total content of one or more selected from chlorodifluoromethane and difluoromethane is greater than the content of the other fluorocarbons.

[0068] The composite material may contain a resin in addition to the fluorocarbon and the porous membrane, such as an acrylic resin, a polyurethane resin, a polyolefin resin, a polyester resin, a polyamide resin, a polyimide resin, a vinyl chloride resin, a styrene resin, a vinyl ether resin, a polyvinyl alcohol resin, a polycarbonate resin, a polyethersulfone resin, and a polysulfone resin.

[0069] The composite material may contain additives such as emulsifiers, antifoaming agents, surfactants, leveling agents, thickeners, viscoelasticity modifiers, defoamers, wetting agents, dispersants, preservatives, plasticizers, penetrating agents, fragrances, bactericides, miticides, fungicides, ultraviolet absorbers, antioxidants, antistatic agents, flame retardants, dyes, and pigments.

[0070] (Third embodiment: separation device) A separation device according to one embodiment of the present disclosure will be described below, but the present disclosure is not limited to this embodiment.

[0071] The device of the present disclosure comprises: A porous membrane is provided, The porous membrane contains zeolite that separates a gas composition having an improved mixture ratio of one fluorocarbon gas from a mixed gas containing two or more fluorocarbon gases with different molecular diameters, or a single gas.

[0072] FIG. 1 is a schematic diagram illustrating a two-stage separation device as an example of the separation device of the present disclosure.

[0073] In the separation apparatus of Fig. 1, a mixed gas containing two or more fluorocarbon gases with different molecular diameters is stored in a gas tank 1. The mixed gas is supplied to a first-stage separation module 4a through a pressure regulator 2a and a mass flow controller 3a. In one embodiment, the pressure can be controlled by the pressure regulator 2a, but is not limited to such an embodiment. The pressure regulator 2a can be omitted.

[0074] The separation module 4a includes a porous membrane 10a, and the mixed gas is supplied to the porous membrane 10a. At this time, pressure control may be performed by the retentate side back pressure valve 6a. Typically, pressure reduction control can be performed by the retentate side back pressure valve 6a. The retentate side gas back pressure valve 6a may be omitted.

[0075] The gas that does not permeate the porous membrane 10a (hereinafter also referred to as "first retention side gas") is recovered in the retention side gas recovery pipe 11 through the pressure regulator 2c. The first retention side gas may be recovered in the gas tank 1. In one embodiment, the flow rate of the first retention side gas may be controlled by a mass flow controller.

[0076] In the two-stage separation device, the gas that has permeated the porous membrane 10a (hereinafter also referred to as the "first permeating gas") is measured in terms of the amount of permeation by the mass flow meter 5a, and is supplied to the second-stage separation module 4b through the pressure regulator 2b and the mass flow controller 3b. In one embodiment, the pressure can be controlled by the pressure regulator 2b, but is not limited to such an embodiment. The pressure regulator 2b can also be omitted.

[0077] The second-stage separation module 4b is equipped with a porous membrane 10b, and the first permeable gas is supplied to the porous membrane 10b. At this time, pressure control may be performed by the retentate gas back pressure valve 6b. Typically, pressure reduction control can be performed by the retentate gas back pressure valve 6a. The retentate gas back pressure valve 6b may be omitted.

[0078] Of the first permeable gas, the gas that has not permeated the porous membrane 10b (hereinafter also referred to as "second retained side gas") has its gas composition analyzed by a gas composition analyzer 8b, and is then circulated to the gas tank 1. In another embodiment, the second retained side gas may be separately recovered by a retained side gas recovery pipe. In yet another embodiment, the second retained side gas may be separately circulated between the mass flow meter 5 and the pressure regulator 2b. In one embodiment, the gas composition analyzer 8b can be omitted.

[0079] Among the first permeable gases, the gas that has permeated the porous membrane 10b (hereinafter also referred to as "second permeable gas") passes through the pressure regulator 2d, and the gas composition is analyzed by the gas composition analyzer 8a, and then the gas is collected in the collection pipe 9. In one embodiment, the amount of the gas that has permeated the porous membrane 10b may be measured using a mass flow meter. In another embodiment, the gas composition analyzer 8a can be omitted.

[0080] In this embodiment, a two-stage separation device has been described, but the present invention is not limited thereto and can be modified as appropriate, for example, a one-stage, three-stage, four-stage or more stage separation device may be used. In the case of a one-stage separation device, the first permeable gas may be recovered by a recovery pipe, and the first retaining side gas may be recovered by a retaining side gas recovery pipe or circulated to the gas tank 1.

[0081] In the case of an n-stage system (n is 3 or more), the permeable gas that has permeated the n-1th separation module may be supplied to the separation module via a pressure regulator and a mass flow controller, and separated into an nth permeable gas that has permeated the porous membrane and an nth retentate gas that has not permeated the porous membrane through a porous membrane contained in the separation module. Gas separation can be performed by recovering the nth permeable gas after gas composition analysis that may be performed as necessary. In addition, the nth retentate gas may be circulated to the gas tank 1 or recovered in the retentate gas recovery pipe after gas analysis that may be performed as necessary. EXAMPLES

[0082] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these.

[0083] Example 1 Fluorocarbon gas, adjusted to a given pressure and flow rate using a pressure regulator and mass flow controller (MFC), was passed through a membrane module equipped with a ZSM-5 zeolite membrane (Esep). A pressure regulator and mass flow meter (MFM) were used to check the pressure and flow rate on the permeation side and retention side. A vacuum pump was connected to the permeation side, and measurements were performed under reduced pressure conditions as necessary. The permeability of single component gases was calculated from the flow rate.

[0084] The fluorocarbons used were R32 (difluoromethane) and R125 (1,1,1,2,2-pentafluoroethane). The molecular diameter of R32 is 3.9 Å, and the molecular diameter of R125 is 4.4 Å.

[0085] The molecular diameter of the above fluorocarbons was determined using the values ​​described in Wanigarathna, JADK (2018). Adsorption-based fluorocarbon separation in zeolites and metal organic frameworks. Doctoral thesis, Nanyang Technological University, Singapore.

[0086] The zeolite used was ZSM-5 type zeolite (pore size 5.5 Å). The pore size of the zeolite membrane, the temperature and feed side differential pressure during measurement, the permeation amount (R32 and R125), and the permeability ratio are shown in the table below.

[0087] [Table 1]

[0088] Examples 1 to 3 are examples of the present disclosure, and are examples in which fluorocarbons are supplied to a porous membrane containing zeolite. In all of the examples, it was confirmed that the permeation amount of R32 (difluoromethane) was greater than the permeation amount of R125 (1,1,1,2,2-pentafluoroethane), and the ratio of the permeation amount of R32 to the permeation amount of R125 was 6 to 28 times. From this, it can be said that a mixed gas containing two or more kinds of fluorocarbon gases can be supplied to a porous membrane containing zeolite, and one kind of fluorocarbon gas selected from the two or more kinds of fluorocarbon gases can be separated. [Explanation of symbols]

[0089] 1 Gas Tank 2a, 2b, 2c, 2d pressure regulator 3a, 3b Mass flow controller 4a, 4b Separation module 5 Mass Flow Meter 6a, 6b Back pressure retention valve 7 Pressure reducing booster 8a, 8b Gas composition analyzer 9 Separated gas recovery piping 10a, 10b porous membrane 11 Retention side gas recovery piping

Claims

1. The method includes supplying a mixed gas containing two or more fluorocarbon gases having different molecular diameters to a porous membrane, and separating a gas composition or a single gas in which a mixture ratio of one fluorocarbon gas selected from the two or more fluorocarbon gases is improved; The porous membrane contains zeolite, The silica / alumina ratio of the zeolite is 5-100.

2. 2. The method for separating a fluorocarbon gas according to claim 1, wherein the average pore size of the porous membrane is from 2 Å to 10 Å.

3. The method for separating a fluorocarbon gas according to claim 1 , wherein the porous membrane includes a porous membrane formed by a hydrothermal synthesis method.

4. 2. The method for separating a fluorocarbon gas according to claim 1, wherein the zeolite comprises one or more types selected from ZSM-5 type zeolites.

5. 2. The method for separating fluorocarbon gases according to claim 1, wherein the molecular diameter of the one fluorocarbon gas is 2 Å or more and 7 Å or less.

6. 2. The method for separating fluorocarbon gases according to claim 1, wherein a difference between a molecular diameter of the one fluorocarbon gas and a molecular diameter of the other fluorocarbon gas is 0.1 Å or more and 3 Å or less.

7. 2. The method for separating a fluorocarbon gas according to claim 1, wherein the mixed gas is supplied to the porous membrane at a temperature of 20° C. or more and 300° C. or less.

8. 2. The method for separating a fluorocarbon gas according to claim 1, wherein the mixed gas is supplied to the porous membrane under a differential pressure of 0.1 MPa or more.

9. The method for separating fluorocarbon gases according to claim 1 , wherein the porous membrane further comprises a porous support.

10. The method for separating a fluorocarbon gas according to any one of claims 1 to 9, wherein the mixed gas contains difluoromethane and pentafluoroethane.

11. 2. The method for separating fluorocarbon gases according to claim 1, wherein supplying the mixed gas to the porous membrane includes permeating at least a portion of the mixed gas through the porous membrane.

12. A porous membrane is provided, The porous membrane contains zeolite that separates a gas composition having an improved mixture ratio of one fluorocarbon gas from a mixed gas containing two or more fluorocarbon gases having different molecular diameters, or a single gas; The silica / alumina ratio of the zeolite is between 5 and 100.

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