Method for producing and purifying trifluoroethylene

Abstract

The present invention relates to a process for the purification of fluorocarbons from a mixture containing fluorocarbons and hydrogen, comprising the step of contacting said mixture with a membrane M1 to form a stream F1 containing fluorocarbons and a stream F2 containing hydrogen.The present invention also relates to a process for the production of trifluoroethylene.The present invention also relates to a process for the separation of hydrofluoroolefins or hydrofluoroalkanes from nitrogen by membrane separation.The present invention also relates to a process for the separation of trifluoroethylene from chlorotrifluoroethylene or hydrofluorocarbons.

Description

[Technical field]

[0001] The present invention relates to a process for the production and purification of hydrofluoroolefins, in particular to a process for the production of trifluoroethylene (VF3) and the purification of the latter. [Background technology]

[0002] Fluoroolefins such as VF3 are known and have been used as monomers or comonomers for the preparation of fluorocarbon polymers which exhibit remarkable properties, particularly excellent chemical resistance and good heat resistance.

[0003] Trifluoroethylene is a gas under standard pressure and temperature conditions. The main risks associated with the use of this product, as with other halogenated olefins, are associated with its flammability, its tendency to self-polymerize if not stabilized, its explosiveness due to its chemical instability, and its presumed susceptibility to peroxidation. Trifluoroethylene exhibits the distinctive feature of being extremely flammable, with a lower explosion limit (LEL) of about 10% and an upper explosion limit (UEL) of about 30%. However, the main danger is associated with the tendency of VF3 to decompose violently and explosively under the given pressure conditions in the absence of oxygen but in the presence of an energy source.

[0004] Considering the main risks mentioned above, the synthesis and also the storage of VF3 poses particular problems and strict safety regulations are imposed throughout these processes. In the known routes for preparing trifluoroethylene, chlorotrifluoroethylene (CTFE) and hydrogen are used as starting materials in the gas phase in the presence of a catalyst. A method for the production of trifluoroethylene by hydrocracking CTFE in the gas phase in the presence of a catalyst based on a group VIII metal at atmospheric pressure and at relatively low temperatures is known from WO 2013 / 128102. In this document, the purification of the crude mixture resulting from the reaction and containing trifluoroethylene consists of a series of washing and distillation steps. In particular, gases such as hydrogen and nitrogen are separated from VF3 using an absorption column fed with ethanol. The hydrogen and nitrogen are discharged from the top of the column, while the reaction products (VF3, CTFE, etc.) are dissolved in ethanol and directed to a desorption section in order to separate them from the ethanol. This stage requires the use of large amounts of ethanol, which affects the environmental balance of the entire process (treatment of the solvent used is required, high energy costs). In addition, compounds such as trifluoroethylene and chlorotrifluoroethylene can be difficult to separate, so there is a need to employ more efficient and more environmentally friendly processes. Summary of the Invention

[0005] According to a first aspect, the present invention relates to a method for purifying fluorocarbons from a mixture comprising fluorocarbons and hydrogen, comprising step (a) of contacting said mixture with a membrane M1 to form a stream F1 comprising fluorocarbons and a stream F2 comprising hydrogen.

[0006] The present invention makes it possible to use more efficient and more environmentally friendly processes, since the use of the membranes described in this patent application offers advantages in efficiency and environmental compatibility, since it does not require the absorption solvents normally used to separate fluorocarbons from hydrogen. The present invention also offers advantages in terms of production costs (no need to treat waste solvents) and process simplification.

[0007] According to a preferred embodiment, said membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, cellulose, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene and tetrafluoroethylene / perfluorovinyl ether copolymers optionally substituted with SO3H groups.

[0008] According to a preferred embodiment, the fluorocarbon is fluoromethane, difluoromethane, trifluoromethane, trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, fluoroethane, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, 1,1,1-trifluoroethane, 2-chloro-1,1,2-trifluoroethane, Ethane, 1-chloro-1,1,2-trifluoroethane, 2-chloro-1,1,1-trifluoroethane, 3,3,3-trifluoropropene, hexafluoropropene, 1,1,1,3,3,3-hexafluoropropane, 1,1,2,2,3,3-hexafluoropropane, 1,1,1,2,2,3-hexafluoropropane, 1,1,1,2,3,3-hexafluoropropane, 1,1,2,2,3-pentafluoropropane, 1,1,1,2,2-pentafluoropropane, 1,1,2,3,3-pentafluoropropane, 1,1,1,2,3 -Pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 2-chloro-1,1,1,2-tetrafluoropropane, 3-chloro-1,1,1,3-tetrafluoropropane, 2,3-dichloro-1,1,1-trifluoropropane, 1,1,3,3,3-pentafluoropropene, 1,1,2,3,3-pentafluoropropene, 1,2,3,3,3-pentafluoropropene, 2-chloro-3,3,3-trifluoropropene, 1-chloro-3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, 1,3 ,3,3-tetrafluoropropene, 1,1,2,3-tetrafluoropropene, 1,1,3,3-tetrafluoropropene, 1,2,3,3-tetrafluoropropene, 1,1,3-trifluoropropene, 1,1,2-trifluoropropene, 3,3,3-trifluoropropene, 1,2,3-trifluoropropene, 2,3,3-trifluoropropene, 1,3,3-trifluoropropene, 1,1-difluoropropene, 1,2-difluoropropene, 2,3-difluoropropene and 3,3-difluoropropene.

[0009] According to a preferred embodiment, the fluorocarbon is selected from the group consisting of trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, 2-chloro-1,1,2-trifluoroethane, 1-chloro-1,1,2-trifluoroethane, 2-chloro-1,1,1-trifluoroethane, difluoromethane, trifluoromethane, 2,3,3,3-tetrafluoropropene, 1,3,3, The fluoropropene is selected from the group consisting of 3-tetrafluoropropene, 1-chloro-3,3,3-trifluoropropene, 2-chloro-3,3,3-trifluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 3-chloro-1,1,1,3-tetrafluoropropane, 2-chloro-1,1,1,2-tetrafluoropropane, 2,3-dichloro-1,1,1-trifluoropropane, hexafluoropropene, 1,2,3,3,3-pentafluoropropene, 3,3,3-trifluoropropene and 1,1,1,2,3,3-hexafluoropropane.

[0010] According to a preferred embodiment, the fluorocarbon is selected from the group consisting of trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, difluoromethane, trifluoromethane, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, hexafluoropropene, 1,2,3,3,3-pentafluoropropene, 3,3,3-trifluoropropene and 1,1,1,2,3,3-hexafluoropropane.

[0011] According to a preferred embodiment, said membrane M1 has a selectivity greater than 5, said selectivity being calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of said fluorocarbons through said membrane M1.

[0012] According to a preferred embodiment, said membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose, and polyimide.

[0013] According to a preferred embodiment, said mixture and said stream F1 also contain nitrogen and said method comprises a step (b) of contacting said stream F1 with a membrane M1' to form said fluorocarbon-containing stream F3 and nitrogen-containing stream F4.

[0014] According to a preferred embodiment, said membrane M1' is made from a material selected from the group consisting of polypropylene, polymethylpentene or polyalkylsiloxane.

[0015] According to a second aspect, the present invention provides a method for separating a mixture comprising hydrofluoroolefins and nitrogen, comprising contacting said mixture with a membrane M3 to form a stream F7 comprising said hydrofluoroolefins and a stream F8 comprising nitrogen, said membrane M3 being made from a material comprising siloxane functional groups.

[0016] According to a preferred embodiment, the film M3 has the formula -[-(R)(R')Si-O] n -functional groups, where R and R' are hydrogen, C1-C 20 Alkyl, C3-C 10 Cycloalkyl, C6-C 12 aryl, and n is an integer greater than 50, preferably greater than 100, especially greater than 1000.

[0017] According to a preferred embodiment, said membrane M3 is made from a polyalkylsiloxane.

[0018] According to a preferred embodiment, said membrane M3 is made from polydimethylsiloxane.

[0019] According to a preferred embodiment, the hydrofluoroolefin is selected from the group consisting of trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, 3,3,3-trifluoropropene, hexafluoropropene, 1,1,3,3,3-pentafluoropropene, 1,1,2,3,3-pentafluoropropene, 1,2,3,3,3-pentafluoropropene, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, 1,1,2,3 - selected from the group consisting of tetrafluoropropene, 1,1,3,3-tetrafluoropropene, 1,2,3,3-tetrafluoropropene, 1,1,3-trifluoropropene, 1,1,2-trifluoropropene, 3,3,3-trifluoropropene, 1,2,3-trifluoropropene, 2,3,3-trifluoropropene, 1,3,3-trifluoropropene, 1,1-difluoropropene, 1,2-difluoropropene, 2,3-difluoropropene and 3,3-difluoropropene.

[0020] According to a preferred embodiment, the hydrofluoroolefin is selected from the group consisting of trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, hexafluoropropene, 1,2,3,3,3-pentafluoropropene and 3,3,3-trifluoropropene.

[0021] According to a third aspect, the present invention provides a process for the separation of a mixture comprising a hydrofluoroalkane and nitrogen, comprising the step of contacting said mixture with a membrane M3' to form a stream F7' comprising said hydrofluoroalkane and a stream F8' comprising nitrogen, said membrane M3' being made of a polyolefin.

[0022] According to a preferred embodiment, said membrane M3' is made from a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, polyhexene, polypentene and polybutene.

[0023] According to a preferred embodiment, the hydrofluoroalkane is selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, fluoromethane, difluoromethane, trifluoromethane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,3,3-hexafluoropropane and 3,3,3-trifluoropropene.

[0024] According to a fourth aspect, the invention provides a method for the production of trifluoroethylene in a reactor equipped with a fixed catalyst bed comprising a catalyst, comprising step A) reacting chlorotrifluoroethylene with hydrogen in the gas phase in the presence of the catalyst to produce a stream comprising trifluoroethylene, chlorotrifluoroethylene and unreacted hydrogen, and step B) contacting the stream comprising trifluoroethylene, chlorotrifluoroethylene and possibly hydrogen with a membrane M2 to form a stream F5 comprising trifluoroethylene and possibly hydrogen, and a stream F6 comprising chlorotrifluoroethylene and possibly hydrogen.

[0025] According to a preferred embodiment, said membrane M2 is made from a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethylmethacrylate, cellulose and polyvinylidene fluoride.

[0026] According to a preferred embodiment, said membrane M2 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyimide, and cellulose acetate.

[0027] According to a preferred embodiment, the membrane M2 has a selectivity greater than 9, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of trifluoroethylene through the membrane M2, and the membrane M2 has a selectivity greater than 20, calculated by the ratio of the permeability coefficient of chlorotrifluoroethylene to the permeability coefficient of trifluoroethylene through the membrane M2.

[0028] According to a particular embodiment, said membrane M2 is made from polypropylene or polymethylpentene.

[0029] According to another preferred embodiment, the membrane M2 has a selectivity greater than 100, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of chlorotrifluoroethylene through the membrane M2, and the membrane M2 has a selectivity greater than 10, calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of chlorotrifluoroethylene through the membrane M2.

[0030] According to a particular embodiment, said membrane M2 is made of polyimide or cellulose acetate.

[0031] According to a preferred embodiment, the catalyst comprises 0.01% to 5% by weight of palladium on alumina; preferably the alumina comprises at least 90% alpha-alumina.

[0032] According to a preferred embodiment, said step A) is carried out at a fixed catalyst bed temperature between 50°C and 250°C.

[0033] According to a preferred embodiment, step B) is carried out at a temperature between 0°C and 150°C, advantageously between 0°C and 125°C, preferably between 5°C and 100°C.

[0034] According to this fourth aspect, the invention provides a method for separating a mixture comprising trifluoroethylene and chlorotrifluoroethylene, comprising contacting said mixture with a membrane M2 to form a stream F5 comprising trifluoroethylene and a stream F6 comprising chlorotrifluoroethylene, said membrane M2 being made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethyl methacrylate, cellulose and polyvinylidene fluoride.

[0035] According to a preferred embodiment, said membrane M2 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyimide, and cellulose acetate.

[0036] According to a fifth aspect, the present invention provides a process for the separation of a mixture comprising trifluoroethylene and a hydrofluorocarbon, comprising the step of contacting said mixture with a membrane M4 to form a stream F9 comprising trifluoroethylene and a stream F10 comprising said hydrofluorocarbon.

[0037] According to a preferred embodiment, said membrane M4 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, cellulose, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene, and tetrafluoroethylene / perfluorovinyl ether copolymers optionally substituted with SO3H groups.

[0038] According to a preferred embodiment, said membrane M4 is selected from a film, a laminate, a hollow fiber, and a coated fiber.

[0039] According to a preferred embodiment, said membrane M4 is made from a material selected from the group consisting of polyolefins, polyethers, polyimides and cellulose.

[0040] According to a preferred embodiment, said membrane M4 is made from a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0041] According to a preferred embodiment, said membrane M4 is made from a material selected from the group consisting of polypropylene and polymethylpentene.

[0042] According to a preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, fluoromethane, difluoromethane, trifluoromethane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane and 1,1,1,2,3,3-hexafluoropropane.

[0043] Preferably, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane and 1,1,2-trifluoroethane.

[0044] Preferably, the membrane M4 has a selectivity greater than 10, advantageously greater than 15, preferably greater than 20, more preferentially greater than 25 and in particular greater than 30, the selectivity being calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of the hydrofluoroalkane through the membrane M4.

[0045] According to a particularly preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane, and the membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0046] According to a particularly preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane, and the membrane M4 is made of a material selected from the group consisting of polypropylene and polymethylpentene, preferably polymethylpentene.

[0047] According to this fifth aspect, the invention also provides a process for the production of trifluoroethylene, comprising a step A1) of forming a stream comprising trifluoroethylene and 1,1,1,2-tetrafluoroethane by a dehydrofluorination step of 1,1,1,2-tetrafluoroethane or a reaction step between chlorodifluoromethane and chlorofluoromethane, and a step B1) of separating the stream comprising trifluoroethylene and hydrofluorocarbons using a membrane M4 according to the fifth aspect of the invention to form a stream F9' comprising trifluoroethylene and a stream F10' comprising said hydrofluorocarbons.

[0048] According to a preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane, and the membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0049] According to a preferred embodiment, the hydrofluorocarbon is 1,1,1,2-tetrafluoroethane and the membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] [Separation of hydrogen from fluorocarbons] According to a first aspect, the present invention relates to a method for purifying fluorocarbons from a mixture comprising fluorocarbons and hydrogen, said method comprising step (a) contacting said mixture with a membrane M1 to form a stream F1 comprising fluorocarbons and a stream F2 comprising hydrogen.

[0051] Preferably, the mixture comprises a molar content of H2 of less than 50%, preferably less than 25%, based on the total molar amount of the mixture. Preferably, the mixture comprises a molar content of H2 of more than 1%, preferably more than 5%, in particular more than 10%, based on the total molar amount of the mixture.

[0052] Preferably, the mixture is in gaseous form.

[0053] The process thus makes it possible to produce a stream F1 rich in fluorocarbons relative to the initial mixture before contacting the membrane. Preferably, said stream F1 has a reduced molar content of hydrogen relative to said mixture. According to a preferred embodiment, said stream F1 comprises at least 25% by weight of fluorocarbons, advantageously at least 30% by weight of fluorocarbons, preferably at least 35% by weight of fluorocarbons, more preferentially at least 40% by weight of fluorocarbons, in particular at least 45% by weight of fluorocarbons and more particularly at least 50% by weight of fluorocarbons, based on the total weight of said stream F1.

[0054] Preferably, said stream F1 comprises less than 20% by weight of hydrogen, based on the total weight of said stream F1. Advantageously, said stream F1 comprises less than 15% by weight, preferably less than 10% by weight, in particular less than 5% by weight and more particularly less than 1% by weight of hydrogen, based on the total weight of said stream F1.

[0055] In the process, stream F2 is enriched in hydrogen. According to a preferred embodiment, said stream F2 has an increased molar content of hydrogen with respect to said mixture. Preferably, said stream F2 comprises at least 25% by weight of hydrogen, more preferentially at least 50% by weight of hydrogen, in particular at least 75% by weight of hydrogen, more particularly at least 80% by weight of hydrogen, preferably at least 95% by weight of hydrogen, based on the total weight of said stream F2.

[0056] Fluorocarbon refers to a compound that contains at least one fluorine atom and at least one carbon atom. Fluorocarbons can be, for example, hydrofluoroalkanes, hydrofluoroolefins, hydrochlorofluoroalkanes, or hydrochlorofluoroolefins. The term hydrofluoroalkane refers to an alkane compound that contains hydrogen atoms and one or more fluorine atoms as substituents of the carbon atoms. The term hydrofluoroolefin refers to an olefin that contains at least one carbon-carbon double bond and hydrogen atoms and one or more fluorine atoms as substituents of the carbon atoms. The term hydrochlorofluoroalkane refers to an alkane compound that contains hydrogen atoms, one or more chlorine atoms, and one or more fluorine atoms as substituents of the carbon atoms. The term hydrochlorofluoroolefin refers to an olefin that contains at least one carbon-carbon double bond and hydrogen atoms, one or more chlorine atoms, and one or more fluorine atoms as substituents of the carbon atoms.

[0057] Preferably, the fluorocarbon contains 1, 2, 3, or 4 carbon atoms.

[0058] Preferably, the fluorocarbon is fluoromethane, difluoromethane, trifluoromethane, trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, fluoroethane, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, 1,1,1-trifluoroethane, 2-chloro-1,1,2-trifluoroethane. , 1-chloro-1,1,2-trifluoroethane, 2-chloro-1,1,1-trifluoroethane, 3,3,3-trifluoropropene, hexafluoropropene, 1,1,1,3,3,3-hexafluoropropane, 1,1,2,2,3,3-hexafluoropropane, 1,1,1,2,2,3-hexafluoropropane, 1,1,1,2,3,3-hexafluoropropane, 1,1,2,2,3-pentafluoropropane, 1,1,1,2,2-pentafluoropropane, 1,1,2,3,3-pentafluoropropane, 1,1,1,2,3-pentafluoropropane pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 2-chloro-1,1,1,2-tetrafluoropropane, 3-chloro-1,1,1,3-tetrafluoropropane, 2,3-dichloro-1,1,1-trifluoropropane, 1,1,3,3,3-pentafluoropropene, 1,1,2,3,3-pentafluoropropene, 1,2,3,3,3-pentafluoropropene, 2-chloro-3,3,3-trifluoropropene, 1-chloro-3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, 1,3, It is selected from the group consisting of 3,3-tetrafluoropropene, 1,1,2,3-tetrafluoropropene, 1,1,3,3-tetrafluoropropene, 1,2,3,3-tetrafluoropropene, 1,1,3-trifluoropropene, 1,1,2-trifluoropropene, 3,3,3-trifluoropropene, 1,2,3-trifluoropropene, 2,3,3-trifluoropropene, 1,3,3-trifluoropropene, 1,1-difluoropropene, 1,2-difluoropropene, 2,3-difluoropropene and 3,3-difluoropropene.

[0059] In particular, the fluorocarbons are trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, 2-chloro-1,1,2-trifluoroethane, 1-chloro-1,1,2-trifluoroethane, 2-chloro-1,1,1-trifluoroethane, difluoromethane, trifluoromethane, 2,3,3,3-tetrafluoropropene, 1 ... The fluoropropene may be selected from the group consisting of fluoropropene, 1-chloro-3,3,3-trifluoropropene, 2-chloro-3,3,3-trifluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 3-chloro-1,1,1,3-tetrafluoropropane, 2-chloro-1,1,1,2-tetrafluoropropane, 2,3-dichloro-1,1,1-trifluoropropane, hexafluoropropene, 1,2,3,3,3-pentafluoropropene, 3,3,3-trifluoropropene, and 1,1,1,2,3,3-hexafluoropropane.

[0060] More particularly, the fluorocarbon is selected from the group consisting of trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, 2-chloro-1,1,2-trifluoroethane, 1-chloro-1,1,2-trifluoroethane, 2-chloro-1,1,1-trifluoroethane, difluoromethane and trifluoromethane.

[0061] In this patent application, the term membrane refers to a membrane that is selectively permeable to one or more compounds, allowing different compounds to move through the membrane at different flow rates. The membrane restricts the movement of molecules through the membrane, with some molecules moving more slowly than others or being completely excluded (i.e., impermeable). For example, a membrane may be selectively permeable to fluorocarbons and impermeable (or weakly permeable) to hydrogen.

[0062] The permeability coefficient of a membrane depends on its ability to restrict or not restrict the diffusion of these compounds through the membrane. Membranes can selectively separate components over a wide range of solubility parameters and molecular sizes, from polymeric materials to simple ionic or covalent compounds. The property that determines the performance quality of a membrane is primarily its selectivity. Membrane separation processes are characterized by the splitting of a feed stream into two streams: retentate and permeate. The retentate is the portion of the feed that does not (or only slightly) pass through the membrane, and the permeate is the portion of the feed that does pass through the membrane.

[0063] In this patent application, the retentate stream can be one of the streams described depending on the membrane used and the compound under consideration.

[0064] Unlike distillation processes, membrane separation does not require phase separation, which generally allows for significant energy savings compared to distillation processes. Capital costs can also be reduced because membrane separation processes generally have no moving parts, no complex control schemes, and fewer ancillary equipment items compared to other separation processes known in the art.

[0065] Membranes can be manufactured to have extremely high selectivity for the components being separated. Generally, selectivity values ​​are much higher than typical values ​​for relative volatility in distillation operations. Membrane separation processes also allow the recovery of minor but valuable components from the main stream without significant energy costs. Membrane separation processes are potentially environmentally friendly because the membrane approach requires the use of relatively simple and non-hazardous materials.

[0066] According to a preferred embodiment, said membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, cellulose, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene, and tetrafluoroethylene / perfluorovinyl ether copolymers optionally substituted with SO3H groups.

[0067] Preferably, said membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethylmethacrylate, cellulose, and polyvinylidene fluoride.

[0068] In this patent application, the term polyolefin refers especially to polyethylene, polypropylene, polymethylpropene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene, and polyethylbutene.

[0069] In the present patent application, the term polyether refers in particular to the monomer units -[-O-Ar-]- or -[-Ar 1 -O-Ar 2 -]-, where Ar, Ar 1 and Ar 2 may be, independently of one another, one or more C1-C 10 is an aromatic ring containing 6 to 12 carbon atoms, optionally substituted by alkyl functional groups; preferably, Ar is a phenyl group, optionally substituted by one, two, three or four C1-C3 alkyl functional groups. In particular, the polyether is poly[oxy(2,6-dimethyl-1,4-phenylene)] or poly(phenylene oxide).

[0070] In this patent application, the cellulose is preferably cellulose acetate.

[0071] When the selectivity is greater than 2, it can be considered that there is a separation between hydrogen and said fluorocarbon. The higher the selectivity, the more efficient the separation. The process is particularly efficient when the selectivity is greater than 5, preferably greater than 9, in particular greater than 20.

[0072] If the permeability coefficient of the membrane M1 for hydrogen is greater than the permeability coefficient of the membrane M1 for the fluorocarbon, the selectivity is calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of the fluorocarbon under consideration through the membrane M1, i.e., selectivity = [permeability coefficient of hydrogen] / [permeability coefficient of the fluorocarbon]. Alternatively, if the permeability coefficient of the membrane M1 for fluorocarbon is greater than the permeability coefficient of the membrane for hydrogen, the selectivity is calculated by the ratio of the permeability coefficient of the fluorocarbon under consideration to the permeability coefficient of hydrogen through the membrane, i.e., selectivity = [permeability coefficient of the fluorocarbon] / [permeability coefficient of hydrogen].

[0073] Preferably, said membrane M1 has a selectivity greater than 4, advantageously greater than 5, preferably greater than 6, more preferentially greater than 7, in particular greater than 8, and more particularly greater than 9, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of said fluorocarbon through the membrane. In particular, the selectivity of said membrane M1 can be greater than 10, or greater than 12, or greater than 14, or greater than 16, or greater than 18, or greater than 20, or greater than 22, or greater than 24, or greater than 26, or greater than 28, or greater than 30, or greater than 32, or greater than 34, or greater than 36, or greater than 38, or greater than 40, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of said fluorocarbon through the membrane M1.

[0074] Alternatively, the membrane M1 has a selectivity greater than 4, advantageously greater than 5, preferably greater than 6, more preferentially greater than 7, in particular greater than 8, and more particularly greater than 9, calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of hydrogen through the membrane M1. In particular, the selectivity of the membrane M1 can be greater than 10, or greater than 12, or greater than 14, or greater than 16, or greater than 18, or greater than 20, or greater than 22, or greater than 24, or greater than 26, or greater than 28, or greater than 30, or greater than 32, or greater than 34, or greater than 36, or greater than 38, or greater than 40, calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of hydrogen through the membrane M1.

[0075] Step (a) may be carried out over a wide temperature and pressure range.

[0076] Preferably, step (a) of contacting said mixture with said membrane M1 is carried out at a pressure of from 0.1 bara to 30 bara, advantageously from 0.2 bara to 25 bara, preferably from 0.3 bara to 20 bara, more preferentially from 0.4 bara to 15 bara, in particular from 0.5 bara to 10 bara and more particularly from 0.5 bara to 5 bara.

[0077] Preferably, step (a) of contacting the mixture with the membrane M1 is carried out at a temperature of from 0°C to 150°C, advantageously from 0°C to 125°C, preferably from 5°C to 100°C, more preferentially from 10°C to 75°C, in particular from 10°C to 50°C.

[0078] During the process, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The pressure difference expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the pressure difference is between 1 and 3000 kPa, preferably between 50 and 2000 kPa, in particular between 100 and 1000 kPa, more particularly between 100 and 500 kPa.

[0079] According to a particular embodiment, the fluorocarbon is trifluoroethylene.Preferably, when the fluorocarbon is trifluoroethylene, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose and polyimides.

[0080] According to another particular embodiment, the fluorocarbon is 2,3,3,3-tetrafluoropropene.Preferably, when the fluorocarbon is 2,3,3,3-tetrafluoropropene, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0081] According to another particular embodiment, the fluorocarbon is pentafluoroethane.Preferably, when the fluorocarbon is pentafluoroethane, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0082] According to another particular embodiment, the fluorocarbon is hexafluoropropene.Preferably, when the fluorocarbon is hexafluoropropene, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0083] According to another particular embodiment, the fluorocarbon is 1,1,1,2,3-pentafluoropropene.Preferably, when the fluorocarbon is 1,1,1,2,3-pentafluoropropene, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0084] According to another particular embodiment, the fluorocarbon is 1,1-difluoroethylene.Preferably, when the fluorocarbon is 1,1-difluoroethylene, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0085] According to another particular embodiment, the fluorocarbon is 1,2-difluoroethylene (E and / or Z). Preferably, when the fluorocarbon is 1,2-difluoroethylene (E and / or Z), the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0086] According to another particular embodiment, the fluorocarbon is chlorotrifluoroethylene.Preferably, when the fluorocarbon is chlorotrifluoroethylene, the membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluoride, cellulose and polyimides; in particular, the membrane M1 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluoride, cellulose acetate and polyimides.

[0087] According to a preferred embodiment, in the process, hydrogen is preferably in anhydrous form. According to a preferred embodiment, fluorocarbon is preferably in anhydrous form. The term anhydrous means that the weight content of water is less than 1000 ppm, advantageously less than 500 ppm, preferably less than 200 ppm, in particular less than 100 ppm, based on the total weight of the compound under consideration.

[0088] The mixture used in this process and contacted with the membrane M1 may also contain nitrogen. If this mixture is subjected to step (a) of the process, the stream F1 also contains nitrogen. The stream F1 may be subjected to a second membrane purification step. The process includes step (b) of contacting the stream F1 with a membrane M1' to form a stream F3 containing the fluorocarbons and a stream F4 containing nitrogen.

[0089] According to a first embodiment, the membrane M1' may be more permeable to the fluorocarbon than to nitrogen, thus having a selectivity greater than 2, advantageously greater than 3, preferably greater than 4, more preferentially greater than 5, in particular greater than 6 and more particularly greater than 7, calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of nitrogen through the membrane M1'.

[0090] Preferably, in this embodiment, the fluorocarbon is a hydrofluoroolefin or a hydrochlorofluoroolefin. In particular, the fluorocarbon is a hydrofluoroolefin. More particularly, step b) can be carried out under the conditions described below in embodiment 1 according to the method for separating nitrogen from a fluorocarbon.

[0091] Preferably, in this embodiment, the membrane M1' is made of a polyolefin, a polyether or contains siloxane functional groups. Preferably, the second membrane is made of polypropylene, polymethylpentene or a polyalkylsiloxane. The polyalkylsiloxane is preferably polydimethylsiloxane.

[0092] Alternatively, according to a second embodiment, the membrane M1' is more permeable to nitrogen than to fluorocarbons. Thus, the membrane M1' has a selectivity greater than 2, advantageously greater than 3, preferably greater than 4, more preferentially greater than 5, in particular greater than 6 and more particularly greater than 7, calculated by the ratio of the permeability coefficient of nitrogen to the permeability coefficient of the fluorocarbon through the membrane M1'. In particular, the selectivity of the membrane M1' can be greater than 10, or greater than 12, or greater than 14, or greater than 16, or greater than 18, or greater than 20, or greater than 22, or greater than 24, or greater than 26, or greater than 28, or greater than 30, or greater than 32, or greater than 34, or greater than 36, or greater than 38 or greater than 40, calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of nitrogen through the membrane M1'. Preferably, in this embodiment, the fluorocarbon is a hydrofluoroalkane or a hydrochlorofluoroalkane, in particular a hydrofluoroalkane. More particularly, step b) can be carried out under the conditions described below in embodiment 2 according to the method for separating nitrogen from fluorocarbons. In particular, in this embodiment, the membrane M1' is made of polyolefin. More particularly, the membrane M1' is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpropene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene and polyethylbutene. Desirably, the membrane M1' is made of a material selected from the group consisting of polypropylene and polymethylpentene.

[0093] Alternatively, according to a third embodiment, when the mixture comprises nitrogen, hydrogen and a fluorocarbon, step (a) of the method makes it possible to separate nitrogen and hydrogen simultaneously from the fluorocarbon. Thus, in this embodiment, the method comprises a step (a) of contacting the mixture with a membrane M1″ to form a stream F1′ comprising fluorocarbons and a stream F2′ comprising hydrogen and nitrogen. The membrane M1″ may have a selectivity calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of nitrogen through the membrane M1″, of greater than 5, advantageously greater than 10, preferably greater than 15, more preferentially greater than 20, in particular greater than 25 and more particularly greater than 30, and the first membrane may have a selectivity calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of hydrogen through the membrane M1″, of greater than 5, advantageously greater than 10, preferably greater than 15, more preferentially greater than 20, in particular greater than 25 and more particularly greater than 30. Alternatively, said membrane M1" may have a selectivity calculated by the ratio of the permeability coefficient of nitrogen to the permeability coefficient of said fluorocarbon through said membrane M1", which is greater than 5, advantageously greater than 10, preferably greater than 15, more preferentially greater than 20, in particular greater than 25 and more particularly greater than 30, and said membrane M1" may have a selectivity calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of said fluorocarbon through said membrane M1", which is greater than 5, advantageously greater than 10, preferably greater than 15, more preferentially greater than 20, in particular greater than 25 and more particularly greater than 30.

[0094] Alternatively, according to a fourth embodiment, if the mixture comprises nitrogen, hydrogen and fluorocarbons, the nitrogen can be separated from the fluorocarbons and hydrogen before step (a) of the process. In this case, the process comprises a step of contacting the mixture with a membrane M1' to form a stream F1" comprising fluorocarbons and hydrogen and a stream F2" comprising nitrogen. The stream F1" is then subjected to step (a) of the process, i.e. the stream F1" is contacted with the membrane M1 as described above according to the first aspect of the invention.

[0095] In this case, the membrane M1' may have a selectivity calculated by the ratio of the permeability coefficient of the fluorocarbon to the permeability coefficient of nitrogen through the membrane, which is greater than 2, advantageously greater than 3, preferably greater than 4, more preferably greater than 5, in particular greater than 6, and more particularly greater than 7, and the membrane M1' may have a selectivity calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of nitrogen through the membrane, which is greater than 2, advantageously greater than 3, preferably greater than 4, more preferably greater than 5, in particular greater than 6, and more particularly greater than 7. Alternatively, according to this fourth embodiment, the membrane M1' may have a selectivity calculated by the ratio of the permeability coefficient of nitrogen to the permeability coefficient of the fluorocarbon through the membrane, which is greater than 2, advantageously greater than 3, preferably greater than 4, more preferably greater than 5, in particular greater than 6, and more particularly greater than 7, and the membrane M1' may have a selectivity calculated by the ratio of the permeability coefficient of nitrogen to the permeability coefficient of hydrogen .... Thus, in this embodiment, the membrane M1' may be made of a material as described above in the first or second embodiment, depending on the fluorocarbon under consideration.

[0096] In this first aspect of the invention, said membranes M1, M1' and M1" are each independently selected from films, laminates, hollow fibres and coated fibres. The membrane is selected depending on its selectivity with respect to the compounds to be separated. The membrane may be provided on an inert support.

[0097] Hereinafter, this patent application describes a method for separating nitrogen from fluorocarbons. Certain embodiments described in this aspect of the invention may be combined with the first aspect of the invention.

[0098] Generally, step b) is carried out at a pressure of 0.1 bara to 30 bara, advantageously 0.2 bara to 25 bara, preferably 0.3 bara to 20 bara, more preferentially 0.4 bara to 15 bara, in particular 0.5 bara to 10 bara, more particularly 0.5 bara to 5 bara. Preferably, step b) is carried out at a temperature of 0° C. to 150° C., advantageously 0° C. to 125° C., preferably 5° C. to 100° C., more preferentially 10° C. to 75° C., in particular 10° C. to 50° C. During the performance of this step, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The pressure difference expressed here corresponds to the pressure difference existing between the inlet and the outlet of the membrane. Preferably, the pressure difference is 1 to 3000 kPa, preferably 50 to 2000 kPa, in particular 100 to 1000 kPa, more particularly 100 to 500 kPa.

[0099] [Separation of nitrogen from fluorocarbons] [Embodiment 1] According to another aspect of the invention, a method for separating a mixture containing hydrofluoroolefins and nitrogen is provided. According to a preferred embodiment, said method comprises a step of contacting said mixture with a membrane M3 to form a stream F7 containing said one hydrofluoroolefin and a stream F8 containing nitrogen. Preferably, said membrane M3 is made of a material containing siloxane functional groups.

[0100] Preferably, the film M3 has the formula -[-(R)(R')Si-O] n -functional groups, where R and R' are hydrogen, C1-C 20 Alkyl, C3-C 10 Cycloalkyl, C6-C 12 aryl, and n is an integer greater than 50, preferably greater than 100, especially greater than 1000.

[0101] Preferably, said membrane M3 is made of polyalkylsiloxane. According to the invention, in the polyalkylsiloxane compound, the term alkyl means C1-C 10 Refers to alkyl-type groups.

[0102] In particular, said membrane M3 is made from polydimethylsiloxane.

[0103] According to a preferred embodiment, said membrane M3 is selected from a film, a laminate, a hollow fiber, and a coated fiber.

[0104] Preferably, the hydrofluoroolefin is trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, 3,3,3-trifluoropropene, hexafluoropropene, 1,1,3,3,3-pentafluoropropene, 1,1,2,3,3-pentafluoropropene, 1,2,3,3,3-pentafluoropropene, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, 1,1,2,3-tetrafluoropropene, fluoropropene, 1,1,3,3-tetrafluoropropene, 1,2,3,3-tetrafluoropropene, 1,1,3-trifluoropropene, 1,1,2-trifluoropropene, 3,3,3-trifluoropropene, 1,2,3-trifluoropropene, 2,3,3-trifluoropropene, 1,3,3-trifluoropropene, 1,1-difluoropropene, 1,2-difluoropropene, 2,3-difluoropropene and 3,3-difluoropropene.

[0105] In particular, the hydrofluoroolefin is selected from the group consisting of trifluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, hexafluoropropene, 1,2,3,3,3-pentafluoropropene and 3,3,3-trifluoropropene.

[0106] Preferably, the process is carried out at a pressure of 0.1 bara to 30 bara, advantageously 0.2 bara to 25 bara, preferably 0.3 bara to 20 bara, more preferentially 0.4 bara to 15 bara, in particular 0.5 bara to 10 bara, more particularly 0.5 bara to 5 bara. Preferably, this stage is carried out at a temperature of 0° C. to 150° C., advantageously 0° C. to 125° C., preferably 5° C. to 100° C., more preferentially 10° C. to 75° C., in particular 10° C. to 50° C. During the process, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The pressure difference expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the pressure difference is 1 to 3000 kPa, preferably 50 to 2000 kPa, in particular 100 to 1000 kPa, more particularly 100 to 500 kPa.

[0107] Preferably, the membrane M3 has a selectivity greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8 and in particular greater than 9, the selectivity being calculated by the ratio of the permeability coefficient of the hydrofluoroolefin to the permeability coefficient of nitrogen through the membrane M3.

[0108] According to a particularly preferred embodiment, said hydrofluoroolefin is trifluoroethylene and said membrane M3 is made from polydimethylsiloxane.

[0109] According to another particularly preferred embodiment, said hydrofluoroolefin is 2,3,3,3-tetrafluoropropene and said membrane M3 is made from polydimethylsiloxane.

[0110] According to another particularly preferred embodiment, said hydrofluoroolefin is hexafluoropropene and said membrane M3 is made from polydimethylsiloxane.

[0111] According to another particularly preferred embodiment, said hydrofluoroolefin is 1,1,1,2,3-pentafluoropropene and said membrane M3 is made from polydimethylsiloxane.

[0112] According to another particularly preferred embodiment, said hydrofluoroolefin is 1,1-difluoroethylene and said membrane M3 is made from polydimethylsiloxane.

[0113] According to another particularly preferred embodiment, said hydrofluoroolefin is 1,2-difluoroethylene and said membrane M3 is made from polydimethylsiloxane.

[0114] In this embodiment, the process makes it possible to make stream F7 rich in hydrofluoroolefins, relative to the starting mixture. Stream F8, for its part, is rich in nitrogen, relative to the initial mixture.

[0115] [Embodiment 2] According to another aspect of the present invention, a method for separating a mixture comprising a hydrofluoroalkane and nitrogen is provided.

[0116] According to a preferred embodiment, the method comprises a step of contacting the mixture with a membrane M3' to form a stream F7' comprising the hydrofluoroalkane and a stream F8' comprising nitrogen.

[0117] Preferably, said membrane M3' is made from a polyolefin.

[0118] According to a preferred embodiment, said membrane M3' is selected from a film, a laminate, a hollow fiber, and a coated fiber.

[0119] Preferably, said membrane M3' is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpropene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene and polyethylbutene, in particular said membrane is made of polypropylene or polymethylpentene.

[0120] According to a preferred embodiment, the hydrofluoroalkane is selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, fluoromethane, difluoromethane, trifluoromethane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane and 1,1,1,2,3,3-hexafluoropropane.

[0121] Preferably, the membrane M3' has a selectivity greater than 10, advantageously greater than 15, preferably greater than 20, more preferentially greater than 25 and in particular greater than 30, the selectivity being calculated by the ratio of the permeability coefficient of nitrogen to the permeability coefficient of the hydrofluoroalkane through the membrane M3'.

[0122] In a particularly preferred embodiment, said hydrofluoroalkane is pentafluoroethane and said membrane M3' is made from polypropylene or polymethylpentene, preferably polymethylpentene.

[0123] Preferably, the process is carried out at a pressure of 0.1 bara to 30 bara, advantageously 0.2 bara to 25 bara, preferably 0.3 bara to 20 bara, more preferentially 0.4 bara to 15 bara, in particular 0.5 bara to 10 bara, more particularly 0.5 bara to 5 bara. Preferably, this stage is carried out at a temperature of 0° C. to 150° C., advantageously 0° C. to 125° C., preferably 5° C. to 100° C., more preferentially 10° C. to 75° C., in particular 10° C. to 50° C. During the process, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The pressure difference expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the pressure difference is 1 to 3000 kPa, preferably 50 to 2000 kPa, in particular 100 to 1000 kPa, more particularly 100 to 500 kPa.

[0124] In this embodiment, the process makes it possible to make stream F7' rich in hydrofluoroalkanes, relative to the starting mixture. Stream F8', for its part, is rich in nitrogen, relative to the initial mixture.

[0125] Preferably, in embodiment 1 and embodiment 2, nitrogen is in anhydrous form. Preferably, in embodiment 1 and embodiment 2, hydrofluoroolefin and hydrofluoroalkane are in anhydrous form. The term anhydrous means that the weight content of water is less than 1000 ppm, advantageously less than 500 ppm, preferably less than 200 ppm, in particular less than 100 ppm, based on the total weight of the compound under consideration.

[0126] [Method of producing trifluoroethylene] This patent application describes, in the first, second and third aspects of the invention, a method for separating hydrogen and / or nitrogen from fluorocarbons. This method is particularly advantageous in the purification of fluorocarbons such as trifluoroethylene. As mentioned above, trifluoroethylene is used as a monomer or comonomer in the manufacture of fluorocarbon polymers that exhibit notable properties, particularly excellent chemical resistance and good heat resistance. Trifluoroethylene is also used as a refrigerant. These applications require high trifluoroethylene purity while employing efficient and environmentally friendly processes.

[0127] Thus, according to a fourth aspect, the present invention provides a method for the preparation of trifluoroethylene. The present invention provides a method for the preparation of trifluoroethylene in a reactor equipped with a fixed catalyst bed comprising a catalyst, comprising a step A) of reacting chlorotrifluoroethylene with hydrogen in the presence of the catalyst in the gas phase to produce a stream comprising trifluoroethylene, chlorotrifluoroethylene and unreacted hydrogen, and a step B) of contacting the stream comprising trifluoroethylene, chlorotrifluoroethylene and possibly hydrogen with a membrane M2 to form a stream F5 comprising trifluoroethylene and possibly hydrogen and a stream F6 comprising chlorotrifluoroethylene and possibly hydrogen. Preferably, the stream comprising trifluoroethylene, chlorotrifluoroethylene and hydrogen used in step B) is the said stream comprising trifluoroethylene, chlorotrifluoroethylene and unreacted hydrogen produced in step A). ​​Hydrogen can be present in stream F5 or stream F6, depending on the membrane M2 used.

[0128] Surprisingly, it has been demonstrated by this patent application that trifluoroethylene can be separated from chlorotrifluoroethylene and / or hydrogen, both of which are starting materials in the membrane separation process.

[0129] Said membrane M2 has proved to be particularly effective in removing a large part of chlorotrifluoroethylene, one of the unreacted starting reactants in step A) of the process. The permeability coefficient of membrane M2 for trifluoroethylene is significantly different from that for chlorotrifluoroethylene and possibly also for hydrogen. Step B) therefore makes it possible to remove a significant amount of chlorotrifluoroethylene and possibly hydrogen from the trifluoroethylene stream (stream F5), which can facilitate the latter purification operation. For example, trifluoroethylene is generally separated from chlorotrifluoroethylene by cryogenic distillation. By carrying out step B) of the process, the subsequent distillation can be facilitated, for example, so that it can be carried out in a small plant. Step B) can be carried out immediately after step A), or said stream resulting from step A) can be treated after steps i), ii) and iii) described below, before carrying out step B). In this case, the stream subjected to step B) contains trifluoroethylene and chlorotrifluoroethylene, hydrogen having been removed by step iii) described below.

[0130] Thus, relative to the stream used in step B), said stream F5 is enriched in trifluoroethylene. Said stream F6, relative to the stream used in step B), is enriched in chlorotrifluoroethylene.

[0131] Preferably, said stream F6, comprising chlorotrifluoroethylene and possibly hydrogen, is recovered and recycled to stage A). Stream F5 comprising trifluoroethylene can be purified as explained below. Said stage B) makes it possible to remove all or part of the chlorotrifluoroethylene and, optionally, the hydrogen that has not reacted in stage A). This stage therefore makes it possible to limit the amount of unreacted starting material in the subsequent purification stages, thus facilitating the purification of trifluoroethylene as explained above.

[0132] According to a preferred embodiment, the method is carried out in a continuous mode.

[0133] According to a preferred embodiment, hydrogen is in anhydrous form. According to a preferred embodiment, chlorotrifluoroethylene is in anhydrous form. By carrying out the process in the presence of anhydrous hydrogen and / or chlorotrifluoroethylene, the life of catalyst can be effectively increased, and thus the overall productivity of the process can be improved. In this patent application, the term anhydrous means that the weight content of water is less than 1000 ppm, advantageously less than 500 ppm, preferably less than 200 ppm, in particular less than 100 ppm, based on the total weight of the compound under consideration.

[0134] Step A) of the process for the preparation of trifluoroethylene is carried out in the presence of a catalyst. Preferably, the catalyst is based on a metal from groups 8 to 10 of the periodic table of the elements. In particular, the catalyst is based on a metal selected from the group consisting of Pd, Pt, Rh and Ru; preferably palladium. Preferably, the catalyst is supported. The support is preferably selected from the group consisting of activated carbon, aluminum-based supports, calcium carbonate and graphite. Preferably, the support is aluminum-based. In particular, the support is alumina. The alumina can be α-alumina. Preferably, the alumina comprises at least 90% α-alumina. It has been observed that when the alumina is α-alumina, the conversion rate of the hydrocracking reaction is improved. Thus, the catalyst is more particularly palladium supported on alumina, advantageously palladium supported on alumina comprising at least 90% α-alumina, preferably palladium supported on α-alumina. Preferably, the palladium comprises from 0.01% to 5% by weight based on the total weight of the catalyst, preferably from 0.1% to 2% by weight based on the total weight of the catalyst. In particular, the catalyst comprises from 0.01% to 5% by weight of palladium supported on alumina; preferably, the alumina comprises at least 90% alpha-alumina; more preferably, the alumina is alpha-alumina.

[0135] The catalyst is preferably activated before being used in step A). ​​Preferably, the activation of the catalyst is carried out in the presence of a reducing agent at an elevated temperature. According to a particular embodiment, the reducing agent is hydrogen, carbon monoxide, nitric oxide, formaldehyde, C1-C6 alkanes and C1-C 10 Hydrohalocarbons, or mixtures thereof; preferably hydrogen and C1-C 10 hydrohalocarbons, or mixtures thereof; in particular selected from the group consisting of hydrogen, chlorotrifluoroethylene, trifluoroethylene, chlorotrifluoroethane, trifluoroethane and difluoroethane, or mixtures thereof. Preferably, activation of the catalyst is carried out at a temperature between 100° C. and 400° C., in particular between 150° C. and 350° C. In particular, activation of the catalyst is carried out in the presence of hydrogen as a reducing agent, at a temperature between 100° C. and 400° C., in particular between 150° C. and 350° C.

[0136] Said catalyst used in the process can be regenerated. This regeneration step can be carried out at a catalyst bed temperature range between 90°C and 450°C. Preferably, the regeneration step is carried out in the presence of hydrogen. By carrying out the regeneration step, it is possible to improve the reaction yield compared to the initial yield before regeneration. According to a preferred embodiment, the regeneration step can be carried out at a catalyst bed temperature of between 90°C and 300°C, preferably between 90°C and 250°C, more preferentially between 90°C and 200°C, in particular between 90°C and 175°C, more particularly between 90°C and 150°C. In particular, carrying out the regeneration step at low temperatures, for example between 90°C and 200°C or between 90°C and 175°C or between 90°C and 150°C, allows desorption of compounds harmful to the activity of the catalyst and / or makes it possible to limit phase transformations that alter the structure of the catalyst. According to another preferred embodiment, the regeneration step can be carried out at a catalyst bed temperature above 200°C, advantageously above 230°C, preferably above 250°C and in particular above 300°C. The regeneration step can be carried out periodically depending on the productivity or reaction rate obtained in step a). The regeneration step can advantageously be carried out at a catalyst bed temperature between 200° C. and 300° C., preferably between 205° C. and 295° C., more preferentially between 210° C. and 290° C., in particular between 215° C. and 290° C., more particularly between 220° C. and 285° C., desirably between 225° C. and 280° C., more desirably between 230° C. and 280° C. Alternatively, the regeneration step can be carried out at a temperature between 300° C. and 450° C., preferably between 300° C. and 400° C. The regenerated catalyst can be reused in step A) of the process.

[0137] The process comprises a step of reacting chlorotrifluoroethylene (CTFE) with hydrogen to produce a stream comprising trifluoroethylene, as described above. This hydrocracking step is carried out in the gas phase in the presence of a catalyst. Preferably, the hydrocracking step is carried out in the gas phase in the presence of a preactivated catalyst. The hydrocracking step consists of simultaneously introducing hydrogen, CTFE and, optionally, an inert gas such as nitrogen, in the gas phase, preferably in the presence of the catalyst, which is activated. Preferably, said step A) is carried out at a fixed catalyst bed temperature between 50° C. and 250° C. Said step A) can be carried out at a fixed catalyst bed temperature between 50° C. and 240° C., advantageously between 50° C. and 230° C., preferably between 50° C. and 220° C., more preferentially between 50° C. and 210° C., in particular between 50° C. and 200° C. Said step A) can also be carried out at a fixed catalyst bed temperature between 60° C. and 250° C., advantageously between 70° C. and 250° C., preferably between 80° C. and 250° C., more preferentially between 90° C. and 250° C., in particular between 100° C. and 250° C., and more particularly between 120° C. and 250° C. Said step A) can also be carried out at a fixed catalyst bed temperature between 60° C. and 240° C., advantageously between 70° C. and 230° C., preferably between 80° C. and 220° C., more preferentially between 90° C. and 210° C., in particular between 100° C. and 200° C., more particularly between 100° C. and 180° C., desirably between 100° C. and 160° C., and particularly preferably between 120° C. and 160° C.

[0138] The H2 / CTFE molar ratio is between 0.5 / 1 and 2 / 1, preferably between 1 / 1 and 1.2 / 1. If an inert gas such as nitrogen is present in step A), the nitrogen / H2 molar ratio is between 0 / 1 and 2 / 1, preferably between 0 / 1 and 1 / 1. Step A) is preferably carried out at a pressure of 0.05 MPa to 1.1 MPa, more preferably 0.05 MPa to 0.5 MPa, in particular at atmospheric pressure. The contact time, calculated as the ratio of the volume of catalyst (in liters) to the total flow rate of the gas mixture (in standard liters / second) at the inlet of the reactor, is between 1 and 60 seconds, preferably between 5 and 45 seconds, in particular between 10 and 30 seconds, more particularly between 15 and 25 seconds. In the hydrocracking step (step A) of the process, a stream comprising trifluoroethylene is produced. The stream may also comprise unreacted chlorotrifluoroethylene and hydrogen. The stream may also comprise nitrogen. The stream may also contain HCl or HF or a mixture of the two. The stream may also contain organic impurities (such as F143, F133, and other organics).

[0139] In step B), a stream F5 containing trifluoroethylene and possibly hydrogen and a stream F6 containing chlorotrifluoroethylene and possibly hydrogen are formed.

[0140] Preferably, the membrane M2 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, cellulose, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene, and tetrafluoroethylene / perfluorovinyl ether copolymers optionally substituted with SO3H groups.

[0141] Preferably, said membrane M2 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethylmethacrylate, cellulose and polyvinylidene fluoride, the terms polyolefins and polyethers being defined above in relation to the first aspect of the invention. Preferably, the cellulose is cellulose acetate.

[0142] In particular, said membrane M2 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), cellulose acetate, polyvinylidene fluoride and polyimide.

[0143] Preferably, step B) is carried out at a pressure of 0.1 bara to 30 bara, advantageously 0.2 bara to 25 bara, preferably 0.3 bara to 20 bara, more preferentially 0.4 bara to 15 bara, in particular 0.5 bara to 10 bara, and more particularly 0.5 bara to 5 bara. During the carrying out of step B), a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The pressure difference expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the pressure difference is 1 to 3000 kPa, preferably 50 to 2000 kPa, in particular 100 to 1000 kPa, and more particularly 100 to 500 kPa. It has been observed that the pressure difference can affect the value of the permeability coefficient of chlorotrifluoroethylene. Thus, if the selectivity is calculated as the ratio of the permeability coefficient of trifluoroethylene to that of chlorotrifluoroethylene, to obtain a selectivity of more than 5, the pressure difference is about 2.5 bar. If the selectivity is calculated as the ratio of the permeability coefficient of trifluoroethylene to that of chlorotrifluoroethylene, then to obtain a selectivity of more than 10, a differential pressure of about 3.5 bar is required.

[0144] Preferably, step B) is carried out at a temperature of from 0° C. to 150° C., advantageously from 0° C. to 125° C., preferably from 5° C. to 100° C., more preferentially from 10° C. to 75° C., in particular from 10° C. to 50° C.

[0145] Preferably, said membrane M2 has a selectivity, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of trifluoroethylene through said membrane M2, of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8 and in particular greater than 9.

[0146] Preferably, said membrane M2 has a selectivity, calculated by the ratio of the permeability coefficient of chlorotrifluoroethylene to the permeability coefficient of trifluoroethylene through said membrane M2, of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8 and in particular greater than 9.

[0147] In particular, said membrane M2 has a selectivity, calculated by the ratio of the permeability coefficient of chlorotrifluoroethylene to the permeability coefficient of trifluoroethylene through said membrane M2, of greater than 10, or greater than 12, or greater than 14, or greater than 16, or greater than 18, or greater than 20, or greater than 22, or greater than 24.

[0148] Thus, in order to efficiently separate chlorotrifluoroethylene and hydrogen from trifluoroethylene, said membrane M2 has a selectivity calculated as the ratio of the permeability coefficient of hydrogen to the permeability coefficient of trifluoroethylene passing through the membrane of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8, in particular greater than 9, and said membrane M2 has a selectivity calculated as the ratio of the permeability coefficient of chlorotrifluoroethylene to the permeability coefficient of trifluoroethylene passing through the membrane of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8, in particular greater than 9.

[0149] In particular, said membrane M2 has a selectivity calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of trifluoroethylene passing through the membrane of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8 and in particular greater than 9, and said membrane M2 has a selectivity calculated by the ratio of the permeability coefficient of chlorotrifluoroethylene to the permeability coefficient of trifluoroethylene passing through the membrane of greater than 10, or greater than 12, or greater than 14, or greater than 16, or greater than 18, or greater than 20, or greater than 22, or greater than 24.

[0150] The membrane M2 is therefore more permeable to hydrogen and chlorotrifluoroethylene than to trifluoroethylene, which allows an advantageous separation of the stream resulting from step A. This embodiment, with the selectivities mentioned above, is preferably obtained when the membrane M2 is made of a material consisting of polyolefins, in particular polypropylene or polymethylpentene.

[0151] Alternatively, the membrane M2 is more permeable to hydrogen and trifluoroethylene than to chlorotrifluoroethylene, which allows an advantageous separation of the stream resulting from step A. This embodiment has the selectivities stated below and is preferably obtained when the membrane M2 is made of a polyimide or cellulose material, in particular polyimide or cellulose acetate.

[0152] Preferably, said membrane M2 has a selectivity, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of chlorotrifluoroethylene through said membrane M2, of greater than 10, advantageously greater than 20, preferably greater than 50, more preferentially greater than 75 and in particular greater than 100.

[0153] Preferably, said membrane M2 has a selectivity, calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of chlorotrifluoroethylene through said membrane M2, of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8 and in particular greater than 9.

[0154] In particular, said membrane M2 has a selectivity of more than 10, or more than 12, or more than 14, calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of chlorotrifluoroethylene through said membrane M2.

[0155] Thus, in order to efficiently separate chlorotrifluoroethylene from hydrogen and trifluoroethylene, said membrane M2 has a selectivity calculated as the ratio of the permeability coefficient of hydrogen to the permeability coefficient of chlorotrifluoroethylene through the membrane of greater than 10, advantageously greater than 20, preferably greater than 50, more preferentially greater than 75 and in particular greater than 100, and said membrane M2 has a selectivity calculated as the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of chlorotrifluoroethylene through the membrane of greater than 5, advantageously greater than 6, preferably greater than 7, more preferentially greater than 8 and in particular greater than 9.

[0156] In particular, said membrane M2 has a selectivity calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of chlorotrifluoroethylene through the membrane of greater than 10, advantageously greater than 20, preferably greater than 50, more preferentially greater than 75 and in particular greater than 100, and said membrane M2 has a selectivity calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of chlorotrifluoroethylene through the membrane of greater than 10, or greater than 12, or greater than 14.

[0157] According to a preferred embodiment, the stream F5 comprises at least 25% by weight of trifluoroethylene, advantageously at least 30% by weight, preferably at least 35% by weight, more preferentially at least 40% by weight, in particular at least 45% by weight and more particularly at least 50% by weight of trifluoroethylene, based on the total weight of the stream F5. According to a particularly preferred embodiment, the stream F5 comprises at least 55% by weight of trifluoroethylene, advantageously at least 60% by weight, preferably at least 70% by weight, more preferentially at least 80% by weight, in particular at least 90% by weight and more particularly at least 95% by weight of trifluoroethylene, based on the total weight of the stream F5.

[0158] Said stream F5 may contain small amounts of chlorotrifluoroethylene. Preferably, said stream F5 contains a weight content of chlorotrifluoroethylene of less than 40%, preferably less than 30%, more preferentially less than 20%, in particular less than 10% and more particularly less than 5%, based on the total weight of said stream F5.

[0159] The method may comprise additional steps i) to iv), which may be carried out starting from stream F5 or from said stream resulting from step A). ​​As explained above, step B) may be carried out starting from said stream resulting from step A) or from said stream resulting from step A) pretreated to remove certain products by steps i), ii) and optionally iii).

[0160] The method comprises: i) removing HF and / or HCl to form a gas mixture; ii) drying the gas mixture resulting from step i); iii) optionally treating the gas mixture dried in step ii) to remove hydrogen and inert gases and form a gas stream F11; iv) distilling the gas mixture dried in step ii) or the gas stream F11 resulting from step iii), or the stream F5. may include.

[0161] Stream F5 resulting from step B) or said stream resulting from step A) used in step i) is preferably in gaseous form. HCl and HF are removed by passing either of said streams through water in a wash column and then washing with a dilute base such as NaOH or KOH. The remainder of the gas mixture consisting of reactants (H2 and CTFE, if present), dilute nitrogen, if present, trifluoroethylene and organic impurities is directed to a dryer to remove traces of wash water.

[0162] Drying can be carried out using products such as calcium, sodium or magnesium sulfate, calcium chloride, potassium carbonate, silica gel or zeolites, In one embodiment, molecular sieves (zeolites) such as silipolite are used for drying.

[0163] If the gas mixture thus dried contains hydrogen or inert substances, step iii) is preferably carried out, which can be carried out according to various techniques such as absorption / desorption or membrane separation.

[0164] The gas mixture thus dried is optionally subjected to a step of separating hydrogen and inert substances from the remainder of the other products present in the gas mixture by absorption / desorption in the presence of an alcohol containing 1 to 4 carbon atoms, preferably ethanol, at atmospheric pressure and, for absorption, at a temperature below ambient temperature, preferably below 10° C., even more preferably at −25° C. In one embodiment, the absorption of the organic substances is carried out in a countercurrent column containing ethanol cooled to −25° C. The ethanol flow rate is adjusted depending on the flow rate of the organic substances to be absorbed. The hydrogen and inert gases, which are insoluble in ethanol at this temperature, are removed at the top of the absorption column. The organic substances are then recovered in the form of said stream F11 by heating ethanol to its boiling point (desorption).

[0165] Alternatively, the dry gas mixture obtained in step ii) is subjected to step (a) according to the first aspect of the invention, if hydrogen and possibly nitrogen are present. This embodiment makes it possible to remove hydrogen and possibly nitrogen. The dry gas mixture obtained in step ii) is then contacted with said membrane M1 under the conditions described in the first aspect of the invention. This embodiment is preferably obtained with said membrane M1 as described in this patent application and made of a material selected from the group consisting of polyolefins, polyethers, polyvinylidene fluorides, cellulose and polyimides, in particular as explained above, made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyvinylidene fluorides, cellulose and polyimides. The obtained stream F11 comprises trifluoroethylene and possibly chlorotrifluoroethylene. Stream F11 is then subjected to step iv) or step B) to separate the chlorotrifluoroethylene and trifluoroethylene possibly present therein.

[0166] If the gas mixture dried in step ii) does not contain hydrogen, inert compounds, step iii) cannot be carried out and the gas mixture dried in step ii) is distilled in step iv).

[0167] As mentioned above, the stream resulting from step A) can be pretreated with steps i), ii) and optionally iii) described above before carrying out step B) described above. In this case, stream F5 containing trifluoroethylene is recovered and subjected to step iv) to remove other organic compounds and obtain high purity trifluoroethylene. Stream F6 can be recovered and recycled to step A).

[0168] According to step iv), the gas mixture dried in step ii) or said gas stream F11 obtained in step iii) if it is carried out, or stream F5 obtained in step B) if it is carried out in particular after steps i), ii) and iii), is distilled to form a stream F12 comprising trifluoroethylene, which is recovered. According to a preferred embodiment, distillation step iv) is carried out at a pressure below 3 bara, preferably between 0.5 bara and 3 bara, in particular between 0.9 bara and 2 bara. Carrying out the distillation at a pressure below 3 bara makes it possible to make the process safer, since above 3 bara trifluoroethylene is explosive. Said stream F12 is preferably recovered at the top of the distillation column. Before being recovered, stream F12 can optionally be subjected to partial condensation at the top of the distillation column. When partial condensation is carried out, stream F12 is brought to a temperature of -50°C to -70°C. The temperature is adjusted depending on the pressure applied in step iv). Partial condensation makes it possible to improve the efficiency of the distillation by limiting the content of additional compounds in stream F12. The distillation of stage iv) also forms a stream F13 possibly containing residual chlorotrifluoroethylene and organic impurities resulting from the hydrocracking reaction (stage A). This stream F13 is generally recovered at the bottom of the distillation column. Said stream F13 can be recycled to stage A) after an optional purification treatment.

[0169] As explained above, in this fourth aspect, the present invention provides a method for separating trifluoroethylene from chlorotrifluoroethylene according to step B) described above.The present invention therefore provides a method for separating a mixture comprising trifluoroethylene and chlorotrifluoroethylene, comprising the step of contacting said mixture with said membrane M2 to form a stream F5 comprising trifluoroethylene and a stream F6 comprising chlorotrifluoroethylene.

[0170] Preferably, said membrane M2 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethylmethacrylate, cellulose and polyvinylidene fluoride. Preferably, said membrane M2 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyimides and cellulose acetate. The method is carried out according to the conditions described for step B) above. The method is carried out with membrane M2 as described in step B).

[0171] Thus, in this fourth aspect, the present invention provides a process for the production of trifluoroethylene according to various embodiments. For example, the present invention provides a process for the production of trifluoroethylene in a reactor comprising a fixed catalyst bed comprising a catalyst, the process comprising: - A) reacting chlorotrifluoroethylene with hydrogen in the gas phase in the presence of a catalyst to produce a stream comprising trifluoroethylene and unreacted hydrogen and chlorotrifluoroethylene; and - B) contacting said stream resulting from step A) with a membrane M2 to form a stream F5 comprising trifluoroethylene and possibly hydrogen, and a stream F6 comprising chlorotrifluoroethylene and possibly hydrogen; - i) removing HF and / or HCl from stream F5 to form a gas mixture; - ii) drying the gas mixture resulting from step i); - iii) optionally treating the gas mixture dried in step ii) to remove hydrogen and inert gases and form a gas stream F11; - iv) distilling the gas mixture dried in step ii) or the gas stream F11 resulting from step iii) to recover a stream F12 comprising trifluoroethylene. The present invention provides a method comprising:

[0172] The present invention also relates to a process for the production of trifluoroethylene in a reactor equipped with a fixed catalyst bed containing a catalyst, comprising the steps of: - A) reacting chlorotrifluoroethylene with hydrogen in the gas phase in the presence of a catalyst to produce a stream comprising trifluoroethylene and unreacted hydrogen and chlorotrifluoroethylene; - i) removing HF and / or HCl from the stream resulting from step A) to form a gas mixture; - ii) drying the gas mixture resulting from step i); - iii) optionally treating the gas mixture dried in step ii) to remove hydrogen and inert gases and form a gas stream F11; - B) contacting said gas stream F11 or said gas mixture resulting from step i) with a membrane M2 to form a stream F5 comprising trifluoroethylene and possibly hydrogen, and a stream F6 comprising chlorotrifluoroethylene and possibly hydrogen; - iv) distilling said stream F5 to recover a stream F12 comprising trifluoroethylene The present invention provides a method comprising:

[0173] [Separation of trifluoroethylene from hydrofluorocarbons] According to a fifth aspect, the present invention provides a process for the separation of a mixture comprising trifluoroethylene and a hydrofluorocarbon, comprising the step of contacting said mixture with a membrane M4 to form a stream F9 comprising trifluoroethylene and a stream F10 comprising said hydrofluorocarbon.

[0174] Preferably, the hydrofluorocarbon is a hydrofluoroalkane.

[0175] Preferably, said membrane M4 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, cellulose, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene, and tetrafluoroethylene / perfluorovinyl ether copolymers optionally substituted with SO3H groups.

[0176] Preferably, said membrane M4 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyvinylidene fluorides and celluloses.

[0177] According to a preferred embodiment, said membrane M4 is selected from a film, a laminate, a hollow fiber and a coated fiber.

[0178] The term polyolefin refers in particular to polyethylene, polypropylene, polymethylpropene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene and polyethylbutene.

[0179] The term polyether refers in particular to the monomer units -[-O-Ar-]- or -[-Ar 1 -O-Ar 2 -]-, where Ar, Ar 1 and Ar 2 may be, independently of one another, one or more C1-C 10 is an aromatic ring containing 6 to 12 carbon atoms, optionally substituted by alkyl functional groups; preferably, Ar is a phenyl group, optionally substituted by one, two, three or four C1-C3 alkyl functional groups. In particular, the polyether is poly[oxy(2,6-dimethyl-1,4-phenylene)] or poly(phenylene oxide).

[0180] Preferably, the cellulose is cellulose acetate.

[0181] Preferably, said membrane M4 is made from a material selected from the group consisting of polyolefins, polyethers, polyimides and cellulose.

[0182] In particular, said membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide). In particular, said membrane M4 is made of polypropylene or polymethylpentene.

[0183] According to a preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, fluoromethane, difluoromethane, trifluoromethane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane and 1,1,1,2,3,3-hexafluoropropane.

[0184] Preferably, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane and 1,1,2-trifluoroethane.

[0185] Preferably, the membrane M4 has a selectivity greater than 10, advantageously greater than 15, preferably greater than 20, more preferentially greater than 25 and in particular greater than 30, the selectivity being calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of the hydrofluorocarbons through the membrane M4.

[0186] In a particularly preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane, and the membrane M4 is made of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] or poly(phenylene oxide).

[0187] In a particularly preferred embodiment, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane, and the membrane M4 is made of polypropylene or polymethylpentene, preferably polymethylpentene.

[0188] Thus, relative to the starting mixture, stream F9 is enriched in trifluoroethylene, while stream F10 is enriched in hydrofluorocarbons relative to the starting mixture.

[0189] Preferably, the process is carried out at a pressure of 0.1 bara to 30 bara, advantageously 0.2 bara to 25 bara, preferably 0.3 bara to 20 bara, more preferentially 0.4 bara to 15 bara, in particular 0.5 bara to 10 bara, more particularly 0.5 bara to 5 bara. During the process, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The pressure difference expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the pressure difference is 1 to 3000 kPa, preferably 50 to 2000 kPa, in particular 100 to 1000 kPa, more particularly 100 to 500 kPa. Preferably, the process is carried out at a temperature of 0° C. to 150° C., advantageously 0° C. to 125° C., preferably 5° C. to 100° C., more preferentially 10° C. to 75° C., in particular 10° C. to 50° C.

[0190] This method for separating trifluoroethylene from hydrofluorocarbons can be integrated into an overall process for the production of trifluoroethylene.The invention therefore also provides a method for the production of trifluoroethylene, comprising a step A1) of forming a stream comprising trifluoroethylene and 1,1,1,2-tetrafluoroethane by dehydrofluorination of 1,1,1,2-tetrafluoroethane or by reaction of chlorodifluoromethane with chlorofluoromethane, and a step B1) of separating the stream comprising trifluoroethylene and hydrofluorocarbons according to a fifth aspect of the invention using a membrane M4 to form a stream F9' comprising trifluoroethylene and a stream F10' comprising said hydrofluorocarbons.

[0191] Preferably, the hydrofluorocarbon is a hydrofluoroalkane selected from the group consisting of pentafluoroethane, 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane, and the membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0192] In particular, the hydrofluorocarbon is 1,1,1,2-tetrafluoroethane and the membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0193] Step A1) of the preparation of trifluoroethylene can be the thermal dehydrofluorination of 1,1,1,2-tetrafluoroethane (HFC-134a) in the absence or presence of a catalyst.

[0194] [Thermal decomposition of HFC-134a (thermal dehydrofluorination in the absence of a catalyst)] In the absence of a catalyst, the dehydrofluorination of 1,1,1,2-tetrafluoroethane is carried out at a temperature above 500° C., advantageously above 550° C., preferably above 600° C., more preferentially above 650° C., in particular above 700° C., and more particularly above 800° C. The residence time is between 0.1 and 100 seconds, advantageously between 0.1 and 75 seconds, preferably between 0.5 and 50 seconds, more preferentially between 0.5 and 10 seconds, in particular between 0.5 and 5 seconds. The pressure can be between 1 bara and 50 bara, preferably between 1 bara and 25 bara, in particular between 1 bara and 10 bara. The reaction can be carried out in the presence of a diluent, such as nitrogen, helium or argon, preferably nitrogen.

[0195] In this embodiment, the output stream from step A1) preferably contains 1,1,1,2-tetrafluoroethane in addition to trifluoroethylene. The output stream from step A1) may also contain tetrafluoroethylene and 1,1,2,2-tetrafluoroethane. HF is also present in the output stream from step A1). HF can be removed before carrying out step B1). HF can be removed by conventional techniques known to those skilled in the art, such as sparging with water or an alkaline or caustic solution.

[0196] In this embodiment, step B1) of the process is carried out starting from a stream comprising trifluoroethylene, 1,1,1,2-tetrafluoroethane, and possibly tetrafluoroethylene and 1,1,2,2-tetrafluoroethane. Step B1) is carried out with a membrane M4 as defined above, forming a stream F9' comprising trifluoroethylene and a stream F10' comprising 1,1,1,2-tetrafluoroethane. Preferably, said membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)], and poly(phenylene oxide). Step B1) is carried out as indicated above in connection with the separation of trifluoroethylene from hydrofluorocarbons according to the fifth aspect of the invention. Preferably, the 1,1,1,2-tetrafluoroethane is in anhydrous form. The term anhydrous is defined above in this patent application.

[0197] [Catalytic dehydrofluorination of HFC-134a] As mentioned above, in another embodiment, step A1) uses the dehydrofluorination of 1,1,1,2-tetrafluoroethane in the presence of a catalyst in the gas phase. Thus, 1,1,1,2-tetrafluoroethane is contacted in the gas phase with a catalyst based on a metal in the form of an oxide, halide or oxyhalide. The metal is selected from the group consisting of chromium, aluminum, cobalt, zinc, nickel, potassium, silver, cesium, sodium, calcium, titanium, vanadium, zirconium, molybdenum, tin, lead, magnesium and manganese. More particularly, the catalyst can be based on a metal in the form of an oxide, fluoride or oxyfluoride, said metal being selected from the group consisting of chromium, aluminum, cobalt, zinc, nickel, potassium, silver, cesium and sodium. Desirably, the catalyst is based on a metal in the form of an oxide, fluoride or oxyfluoride, said metal being selected from chromium and aluminum. The catalyst may be bulk (unsupported) or supported on a support based on carbon (graphite, activated carbon) or aluminum (alumina, alumina fluoride, aluminum fluoride). The catalytic dehydrofluorination of HFC-134a is preferably carried out at a temperature of from 50° C. to 500° C., advantageously from 100° C. to 450° C., preferably from 150° C. to 450° C., in particular from 200° C. to 450° C. The catalytic dehydrofluorination of HFC-134a is preferably carried out at a pressure of from 1 bara to 20 bara, preferably from 1 bara to 15 bara, in particular from 3 bara to 10 bara. The catalytic dehydrofluorination of HFC-134a is preferably carried out with a contact time of from 0.5 seconds to 60 seconds, preferably from 1 second to 45 seconds, in particular from 5 seconds to 30 seconds. In this embodiment of the catalytic dehydrofluorination of HFC-134a, the output stream from step A1) contains, in addition to trifluoroethylene, 1,1,1,2-tetrafluoroethane and HF. The output stream may also contain one or more of the following compounds: 1,1,2,2-tetrafluoroethane (HFC-134), 2-chloro-1,1,1-trifluoroethane (HCFC-133a), or 2-chloro-1,1-difluoroethylene (HCFO-1122). HF can be removed before carrying out step B1).HF can be removed by conventional techniques known to those skilled in the art, such as sparging with water or an alkaline or caustic solution.

[0198] In this embodiment, step B1) of the process is carried out starting from a stream comprising trifluoroethylene, 1,1,1,2-tetrafluoroethane, and possibly 2-chloro-1,1,1-trifluoroethane, 2-chloro-1,1-difluoroethylene, or 1,1,2,2-tetrafluoroethane. Step B1) is carried out using a membrane M4 as described above, forming a stream F9' comprising trifluoroethylene and a stream F10' comprising 1,1,1,2-tetrafluoroethane. Preferably, said membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)], and poly(phenylene oxide). Step B1) is carried out as indicated above in connection with the separation of trifluoroethylene from hydrofluorocarbons according to the fifth aspect of the invention. Preferably, the 1,1,1,2-tetrafluoroethane is in anhydrous form. The term anhydrous is defined above in this patent application.

[0199] [Reaction of HCFC-22 and HCFC-31] Alternatively, step A1) is a reaction step by pyrolysis of chlorodifluoromethane (HCFC-22) and chlorofluoromethane (HCFC-31). The molar ratio of HCFC-22 / HCFC-31 is between 1:0.01 and 1:4.0, preferably between 0.1 and 1.5. Step A1) is carried out at a temperature between 400° C. and 1200° C., preferably between 600° C. and 900° C., in particular between 710° C. and 900° C. Step A1) is carried out at a pressure between 1 and 3.0 MPa, preferably between 1 and 1.5 MPa. The reactants, i.e. HCFC-22 and HCFC-31, can be heated and mixed before carrying out the reaction. HCFC-22 can be heated to a temperature between 25° C. and 600° C., preferably between 100° C. and 500° C. HCFC-31 can be heated to a temperature between 25° C. and 1200° C., preferably between 100° C. and 800° C. The contact time is 0.01 to 10 seconds, preferably 0.2 to 3.0 seconds. In addition to trifluoroethylene, the output stream contains 1,1,1,2-tetrafluoroethane. The output stream may also contain pentafluoroethane, 1,1,2,2-tetrafluoroethane, or 2-chloro-1,1-difluoroethylene. The output stream may also contain unreacted HCFC-22 and HCFC-31. HF may also be present in the output stream from step A1). HF may be removed before carrying out step B1). HF may be removed by conventional techniques known to those skilled in the art, such as sparging with water or an alkaline or caustic solution.

[0200] In this embodiment, step B1) of the process is carried out starting from a stream comprising trifluoroethylene, 1,1,1,2-tetrafluoroethane, and possibly pentafluoroethane, 1,1,2,2-tetrafluoroethane, chlorofluoromethane, chlorodifluoromethane or 2-chloro-1,1-difluoroethylene. Step B1) is carried out using a membrane M4 as described above, forming a stream F9' comprising trifluoroethylene and a stream F10' comprising 1,1,1,2-tetrafluoroethane. Preferably, said membrane M4 is made of a material selected from the group consisting of polypropylene, polymethylpentene, cellulose acetate, polyimide, poly[oxy(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide). Step B1) is carried out as indicated above in connection with the separation of trifluoroethylene from hydrofluorocarbons according to the fifth aspect of the invention. Preferably, HCFC-22 and HCFC-31 are in anhydrous form. The term anhydrous is defined above in this patent application.

[0201] Step B1) is carried out using membrane M4 as described above according to the fifth embodiment of the invention, irrespective of the reaction step selected (catalytic or catalyst-free dehydrofluorination of HFC-134a or reaction of HCFC-22 with HCFC-31).

[0202] Generally, in the present invention, the process for the preparation of trifluoroethylene is carried out in a reactor that is corrosion resistant (taking into account the presence of HF or HCl in the reaction stream). Steps A) or A1) can be carried out in a reactor made of Monel or Inconel or Hastelloy, or in a reactor made of nickel. EXAMPLES

[0203] The permeability coefficients of gaseous compounds through polymers were measured using an Evonik MET cross-flow filtration cell (inner diameter 52 mm, effective surface area 14 cm) for film polymers. 2) and for fibrous polymers, commercially available modules are used. Modules made of PPO fibers are sold by Parker (reference module ST304 - thickness 50 μm, surface area 0.4 m 2 ). The polyimide film is a Dupont Kapton HN film, the polymethylpentene film has the reference MX004 and the silicone has the reference USP Class VI. The films are supplied by Goodfellow.

[0204] In the following examples, except for PPO, the membranes tested had an effective surface area of ​​14 cm 2 The thickness of the film is shown in Table 1 below. [Table 1]

[0205] The permeability coefficient is calculated according to the following formula: P = Q x e x S -1 ×ΔP -1 Where: P: Permeability coefficient (cm 2 ·s -1 ·Pa -1 ) Q: Permeation flow rate (cm 3 / s) e: Film thickness (cm) S: Membrane surface area (cm 2 ) ΔP: pressure difference across the membrane (Pa) (i.e. the pressure difference referred to in this patent application)

[0206] The permeability coefficient is generally calculated using the following conversion formula: -10 ·cm 3 (STP) cm cm 2 ·s -1 cm Hg -1 ) is represented as: P barrer =P×10 10 / (7.500615×10 -4 )

[0207] Thus, from the data of the material (surface area, thickness), the pressure difference across the membrane, and the measured permeate flow rate through the membrane, the permeability coefficient of the compound through the material can be calculated. The permeability coefficient is thus measured by keeping a compound under pressure upstream of the membrane with no outlet on the retentate side and measuring the flow rate of this same compound at atmospheric pressure on the permeate side. The tests were carried out at a temperature of 25° C., except for the silicone, which was carried out at 35° C. To obtain a more accurate value of the permeability coefficient, the tests are repeated several times, possibly at different pressures. Unless otherwise stated, the permeability coefficient remains constant regardless of ΔP (i.e. the pressure difference across the membrane).

[0208] Example 1: Hydrogen / fluorocarbon separation The experimental protocol detailed above was used independently for each compound of the mixture under consideration: hydrogen and the fluorocarbon (trifluoroethylene (VF3), 2,3,3,3-tetrafluoropropene (HFO-1234yf) or pentafluoroethane (HFC-125)). The membranes used were made of polypropylene, polymethylpentene, poly(phenylene oxide) (PPO), polyimide, PVDF or cellulose acetate. The results are given in Table 2 below. The permeability coefficient values ​​are expressed in barrer. The selectivity reported in the table corresponds to the ratio of the permeability coefficients measured for the two entities under consideration. [Table 2]

[0209] As can be seen from the above data, polyolefin or polyether membranes are more permeable to hydrogen than to both fluorocarbons of the hydrofluoroolefin and hydrofluoroalkane types. Thus, polyolefin (polypropylene or polymethylpentene) or polyether (poly(phenylene oxide)) type membranes make it possible to efficiently separate fluorocarbons such as hydrofluoroolefins or hydrofluoroalkanes from hydrogen.

[0210] Example 2: Nitrogen / fluorocarbon separation The experimental protocol detailed above in Example 1 was used independently for each compound of the mixture under consideration: nitrogen and the fluorocarbons (trifluoroethylene (VF3), 2,3,3,3-tetrafluoropropene (HFO-1234yf) or pentafluoroethane (HFC-125)). The membranes used were made of silicone or polymethylpentene. The results are shown in Table 3 below. The permeability coefficient values ​​are expressed in barrer. The selectivity reported in the table corresponds to the ratio of the permeability coefficients measured for the two entities under consideration. [Table 3]

[0211] As can be seen from the above data, the N2 / HFC-125 selectivity calculated by the ratio of the permeability coefficient of nitrogen through the PMP membrane to the permeability coefficient of HFC-125 through the PMP membrane (i.e. selectivity=9.1 / 0.2) is 45.5, which allows the two compounds to be separated efficiently. As demonstrated by the present invention, membranes of polyolefin type (such as polymethylpentene) allow the efficient separation of hydrofluoroalkanes from nitrogen. In addition, membranes made of silicone (such as polydimethylsiloxane) are more permeable to hydrofluoroolefins than to nitrogen. A 10-fold difference is observed between the permeability coefficient of nitrogen and that of hydrofluoroolefins such as VF3 or HFO-1234yf. The obtained VF3 / N2 and HFO-1234yf / N2 selectivities make it possible to confirm that membranes made of silicone efficiently separate hydrofluoroolefins (such as HFO-1234yf and VF3) from nitrogen.

[0212] Example 3: Method for producing trifluoroethylene (VF3) Several compositions containing 29% to 44% trifluoroethylene (VF3), 9% to 16% chlorotrifluoroethylene (CTFE) and 37% hydrogen are contacted with the polyolefin membrane. The compositions are obtained after carrying out the hydrogenolysis reaction of CTFE with hydrogen in the gas phase in the presence of an alumina-supported palladium catalyst under the conditions described in this patent application. The compositions also contain organic impurities.

[0213] The permeability coefficient of the composition is evaluated using a polymethylpentene membrane according to the protocol described above, and the results are shown in Table 4 below. [Table 4]

[0214] The above results show that polyolefin membranes are more permeable to hydrogen and chlorotrifluoroethylene than to trifluoroethylene. Thus, the composition resulting from the hydrocracking reaction of CTFE with H2 is easily separated by a polyolefin type membrane, such as polymethylpentene. A large amount of CTFE and a large amount of hydrogen are removed from the reaction stream and recycled. A stream rich in trifluoroethylene is thus obtained. Alternatively, the above results show that membranes made of polyimide and cellulose acetate are more permeable to hydrogen and VF3 than to chlorotrifluoroethylene. Thus, the composition resulting from the hydrocracking reaction of CTFE with H2 is easily separated by a polyimide or cellulose type, such as cellulose acetate, membrane. A large amount of CTFE is removed from the reaction stream and recycled. A stream rich in trifluoroethylene is also obtained, and hydrogen can be easily separated from trifluoroethylene by membrane separation as described in this patent application or by the absorption / desorption step described above in this patent application.

[0215] The high selectivity of CTFE / VF3 is particularly advantageous since the subsequent purification of trifluoroethylene is easier to carry out due to the low amount of CTFE in the trifluoroethylene stream emerging from the membrane separation step.

[0216] Example 4: Separation of VF3 / hydrofluoroalkanes The experimental protocol detailed above in Example 1 was used independently for each compound of the mixture under consideration: trifluoroethylene and the hydrofluorocarbons (pentafluoroethane (HFC-125) and 1,1,1,2-tetrafluoroethane (HFC-134a)). The membranes used were made of polymethylpentene. The results are shown in Table 5 below. The permeability coefficient values ​​are expressed in barrer. The selectivity reported in the table corresponds to the ratio of the permeability coefficients measured for the two entities under consideration. [Table 5]

[0217] The above results show that polyolefin membranes are more permeable to trifluoroethylene than to hydrofluoroalkanes such as pentafluoroethane or 1,1,2,2-tetrafluoroethane. Therefore, VF3 can be easily separated from hydrofluoroalkanes such as HFC-125 or HFC-134a. Therefore, polyolefin type membranes can be used in the process for producing trifluoroethylene from 1,1,1,2-tetrafluoroethane or in the process for producing 1,1,1,2-tetrafluoroethane. The desired product, i.e., VF3, is efficiently separated from HFC-134a.

Claims

1. 1. A method for producing trifluoroethylene in a reactor equipped with a fixed catalyst bed containing a catalyst, comprising: step A) reacting chlorotrifluoroethylene with hydrogen in the gas phase in the presence of a catalyst to produce a stream containing trifluoroethylene, chlorotrifluoroethylene and unreacted hydrogen; and step B) contacting the stream containing trifluoroethylene, chlorotrifluoroethylene and optionally hydrogen with a membrane M2 to form a stream F5 containing trifluoroethylene and optionally hydrogen, and a stream F6 containing chlorotrifluoroethylene and optionally hydrogen.

2. 2. The method of claim 1, wherein the membrane M2 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethyl methacrylate, cellulose and polyvinylidene fluoride.

3. 3. The method according to claim 2, wherein the membrane M2 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyimide and cellulose acetate.

4. 2. The method of claim 1, wherein the membrane M2 has a selectivity greater than 9, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of trifluoroethylene through the membrane M2, and wherein the membrane M2 has a selectivity greater than 20, calculated by the ratio of the permeability coefficient of chlorotrifluoroethylene to the permeability coefficient of trifluoroethylene through the membrane M2.

5. 5. The method according to claim 4, characterized in that the membrane M2 is made from polypropylene or polymethylpentene.

6. 2. The method of claim 1, wherein the membrane M2 has a selectivity greater than 100, calculated by the ratio of the permeability coefficient of hydrogen to the permeability coefficient of chlorotrifluoroethylene through the membrane M2, and wherein the membrane M2 has a selectivity greater than 10, calculated by the ratio of the permeability coefficient of trifluoroethylene to the permeability coefficient of chlorotrifluoroethylene through the membrane M2.

7. 7. The method according to claim 6, characterized in that the membrane M2 is made of polyimide or cellulose acetate.

8. 2. The method of claim 1, wherein the catalyst comprises 0.01% to 5% by weight of palladium on alumina; preferably, the alumina comprises at least 90% alpha alumina.

9. 2. The process of claim 1, wherein step A) is carried out at a fixed catalyst bed temperature between 50°C and 250°C.

10. 2. A process according to claim 1, characterized in that step B) is carried out at a temperature of from 0°C to 150°C, advantageously from 0°C to 125°C, preferably from 5°C to 100°C.

11. 1. A method for separating a mixture comprising trifluoroethylene and chlorotrifluoroethylene, comprising contacting said mixture with a membrane M2 to form a stream F5 comprising trifluoroethylene and a stream F6 comprising chlorotrifluoroethylene, said membrane M2 being made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polymethyl methacrylate, cellulose and polyvinylidene fluoride.

12. 12. The method according to claim 11, characterized in that the membrane M2 is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), polyimide and cellulose acetate.