Process for the purification of 1,1,1,2,3,3-hexafluoropropane

Abstract

The present invention relates to a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and at least one contaminant selected from the group consisting of hydrogen, nitrogen and oxygen; said process comprising a step (a) of contacting said mixture with a membrane to form a stream comprising said 1,1,1,2,3,3-hexafluoropropane and a stream comprising said at least one contaminant.

Description

Title of the invention: Process for the purification of 1,1,1,2,3,3-hexafluoropropane Technical field

[0001] The present invention relates to a process for purifying hydrofluoroalkanes. Preferably, the present invention relates to a process for purifying hydrofluoroalkanes by membrane separation. Technological background of the invention

[0002] 1,1,1,2,3,3-Hexafluoropropane (HFC-236ea) is a hydrofluorocarbon and has been described as a raw material for manufacturing 1,1,1,2,3-pentafluoropropene or as an intermediate in the manufacture of 1,1,1,2,3-pentafluoropropane and / or 2,3,3,3-tetrafluoropropene. Examples include US 5679875, US 539600, US 8359964 and US 8389779).

[0003] It can be prepared by high temperature pyrolysis of chlorodifluoromethane (CHC1F2) in the presence of 1,1,1,2-tetrafluoroethane. For example, document WO 1996029296 can be cited.

[0004] 1,1,1,2,3,3-Hexafluoropropane can also be prepared according to a process in which at least one tetrafluorochloropropene is obtained from the dechlorofluorination of 1,1,1,2,2-pentafluoro-3,3-dichloropropane (HCFC-225ca) and / or 1,1,2,2,3-pentafluoro-1,3-dichloropropane (HCFC-225cb) with hydrogen in the presence of a catalyst consisting of a metal oxide. Then the tetrafluorochloropropene(s) produced (1,1,1,2-tetrafluoro-3-chloro-2-propene (HCFO-1224yd), 1,1,2,3-tetrafluoro-1-chloro-2-propene (HCFO-1224ye) and 1,1,2,3-tetrafluoro-3-chloro-1-propene (HCFO-1224yc)) is or are then fluorinated in the presence of a catalyst to produce HFC-236ea. Examples include US 5532418.

[0005] Finally, according to US 5563304, 1,1,1,2,3,3-hexafluoropropane can be prepared by reacting 1,2,3,3,3-pentafluoropropene (HFO-1225ye) with hydrogen fluoride at an elevated temperature, over a catalyst selected from the group comprising aluminum fluoride, fluorinated aluminum oxide, aluminum fluoride-supported metals, fluorinated aluminum oxide-supported metals, and catalysts comprising trivalent chromium.

[0006] 1,1,1,2,3,3-Hexafluoropropane can in particular be prepared by catalytic hydrogenation of hexafluoropropene. This reaction is generally carried out in excess of hydrogen. The hydrogen is generally removed by several distillation steps and drying steps prior to distillation.

[0007] 1,1,1,2,3,3-hexafluoropropane can be used as a cleaning agent in the semiconductor industry. In this type of application, 1,1,1,2,3,3-hexafluoropropane must be of high purity. There is therefore a need to provide a method for purifying 1,1,1,2,3,3-hexafluoropropane that can remove certain contaminants from its preparation processes. Summary of the invention

[0008] According to a first aspect, the present invention relates to a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and hydrogen; said process comprising a step (a) of contacting said mixture with a membrane M1 to form a stream F1 comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2 comprising hydrogen, characterized in that said membrane M1 is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyvinylidene fluoride, a cellulose-based material and poly(methyl methacrylate).

[0009] According to a preferred embodiment, said membrane M1 is made of a material selected from the group consisting of polyolefin and polyether.

[0010] According to a preferred embodiment, said membrane M1 is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0011] According to a preferred embodiment, said membrane M1 has a selectivity greater than 100; said selectivity being calculated by the ratio between the permeability of hydrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane M1; preferably the selectivity is greater than 250, in particular greater than 500.

[0012] According to a preferred embodiment, said mixture contains less than 100 ppm of water based on the total weight of said mixture.

[0013] According to a preferred embodiment, the mass content of hydrogen in said mixture is less than 25% by weight based on the total weight of said mixture.

[0014] According to a preferred embodiment, said mixture is obtained from a hydrogenation reaction of hexafluoropropene, optionally previously purified, preferably by distillation.

[0015] According to another aspect, the present invention relates to a process for producing 1,1,1,2,3,3-hexafluoropropane comprising the steps of:

[0016] A. Gas phase hydrogenation of hexafluoropropene in the presence of hydrogen and a hydrogenation catalyst to form an Al stream comprising 1,1,1,2,3,3-hexafluoropropane and unreacted hydrogen; B. Optionally purification of the Al stream to form a purified A2 stream; C. Implementation of the purification method according to the present invention from said stream Al or said stream A2.

[0017] According to another aspect, the present invention relates to a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and at least one contaminant selected from the group consisting of nitrogen and oxygen or a mixture thereof; said process comprising a step (a) of contacting said mixture with a membrane Ml' to form a stream F1' comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2' comprising said at least one contaminant.

[0018] According to a preferred embodiment, said membrane Ml' is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyaramide, polyamide, polysulfone, polyvinylidene fluoride, poly(methyl methacrylate), polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylenetetrafluoroethylene or tetrafluoroethylene / perfluorovinylether copolymer optionally substituted by an SO3H group, a cellulose-based material and a material containing a siloxane functional group.

[0019] According to a preferred embodiment, said contaminant is oxygen and said membrane Ml' is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyvinylidene fluoride, a cellulose-based material, polyalkylsiloxane and poly(methyl methacrylate).

[0020] According to a preferred embodiment, said membrane Ml' is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), cellulose acetate, polyimide and polydimethylsiloxane.

[0021] According to a preferred embodiment, said contaminant is nitrogen and said membrane M1' is made of a material selected from the group consisting of polyolefin and polyether, preferably polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] or poly(phenylene oxide); in particular polypropylene, poly(phenylene oxide), or polymethylpentene.

[0022] According to a preferred embodiment, the mass content of said contaminant in said mixture is less than 5% based on the total weight of said mixture, preferably less than 1% based on the total weight of said mixture.

[0023] According to another aspect, the present invention relates to a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane, nitrogen, hydrogen and optionally oxygen; said process comprising a step (a) of contacting said mixture with a membrane M2 to form a stream F3 comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F4 comprising nitrogen, hydrogen and optionally oxygen; said membrane M2 being made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide). Detailed description of the invention

[0024] Separation of 1.1.1.2.3.3-hexafluoropropane from hydrogen

[0025] According to a first aspect, the present invention relates to a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and hydrogen. Said process comprises a step (a) of contacting said mixture with a membrane M1 to form a stream F1 comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2 comprising hydrogen.

[0026] Preferably, said mixture comprises a molar hydrogen content of less than 50%, preferably less than 25%, in particular less than 15% based on the total amount in moles of the mixture. Preferably, said mixture comprises a molar hydrogen content of greater than 0.5%, preferably greater than 1% based on the total amount in moles of the mixture.

[0027] Preferably, said mixture is in gaseous form.

[0028] The present process thus makes it possible to produce a flow Fl enriched in 1,1,1,2,3,3-hexafluoropropane compared to the initial mixture before contacting with the membrane. Preferably, said flow Fl has a reduced molar hydrogen content compared to said mixture.

[0029] According to a preferred embodiment, said stream F1 comprises at least 25% by weight of 1,1,1,2,3,3-hexafluoropropane, advantageously at least 30% by weight of 1,1,1,2,3,3-hexafluoropropane, preferably at least 35% by weight of 1,1,1,2,3,3-hexafluoropropane, more preferably at least 40% by weight of 1,1,1,2,3,3-hexafluoropropane, in particular at least 45% by weight of 1,1,1,2,3,3-hexafluoropropane, more particularly at least 50% by weight of 1,1,1,2,3,3-hexafluoropropane based on the total weight of said stream F1.

[0030] 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 of hydrogen, preferably less than 10% by weight, in particular less than 5% by weight, more particularly less than 1% by weight of hydrogen based on the total weight of said stream F1.

[0031] In the present method, the stream F2 is enriched with hydrogen. According to a preferred embodiment, said stream F2 has an increased molar content of hydrogen relative to said mixture. Preferably, said stream F2 comprises at least 25% by weight of hydrogen, more preferably 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.

[0032] In the present application, the term membrane refers to a membrane that is selectively permeable to one or more compounds such that it allows different compounds to migrate therethrough at different flow rates. The membrane restricts the movement of molecules passing through it such that some molecules move more slowly than others or are completely excluded (i.e., impermeable). For example, the membrane may be selectively permeable to hydrogen and impermeable (or weakly permeable) to 1,1,1,2,3,3-hexafluoropropane.

[0033] The permeability of a membrane depends on its ability to limit or not the diffusion of these compounds through it. Membranes can selectively separate components over a wide range of solubility parameters and molecular sizes, from macromolecular materials to simple ionic or covalent compounds. The determining property for membrane performance is mainly selectivity. The membrane separation process is characterized by the fact that a feed stream is divided into two streams: retentate and permeate. The retentate is the part of the feed that does not pass (or only slightly) through the membrane, while the permeate is the part of the feed that passes through the membrane.

[0034] In the present application, the retentate may be one of the streams described depending on the membrane used and the compounds considered.

[0035] 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 little auxiliary equipment compared to other separation processes known in the art.

[0036] Membranes can be produced with extremely high selectivity for the components to be separated. In general, the selectivity values are well above the typical relative volatility values for distillation operations. Membrane separation processes may also be able to recover minor but valuable components from the main stream without substantial energy cost. Membrane separation processes are potentially better for the environment since the membrane approach requires the use of relatively simple and non-harmful materials.

[0037] According to a preferred embodiment, said membrane M1 is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyvinylidene fluoride, a cellulose-based material and poly(methyl methacrylate). Preferably, said membrane M1 is made of a material selected from the group consisting of polyolefin and polyether. In particular, said membrane M1 is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0038] In the present application, the term polyether refers in particular to a polyarylether comprising the monomeric unit -[-O-Ar-]- or -[-Ar'-O-Ar2-]- in which Ar, Ar1 and Ar2 are independently of each other an aromatic ring comprising from 6 to 12 carbon atoms optionally substituted by one or more C1-C10 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).

[0039] In the present application, the term cellulose refers to a polymer consisting of a linear chain of D-glucose units whose hydroxyl function is optionally, partially or not, substituted. The hydrogen of one or more hydroxyl groups may be substituted by a -C(O)-R or C1-C5 alkyl group optionally substituted by an OH, CO2H, CO2R group; with R = C1-C5 alkyl. Preferably, the cellulose is preferably cellulose acetate.

[0040] In the present application, the term polyolefin refers in particular to polyethylene, polypropylene, polymethylpropene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene and polyethylbutene.

[0041] Generally speaking, it can be considered that there is a separation between hydrogen and 1,1,1,2,3,3-hexafluoropropane when the selectivity is greater than 2. The higher the selectivity, the more efficient the separation. The method is particularly efficient when the selectivity is greater than or equal to 5, preferably greater than or equal to 10, in particular greater than or equal to 20.

[0042] When the permeability of said membrane M1 with respect to hydrogen is greater than the permeability of said membrane M1 with respect to 1,1,1,2,3,3-hexafluoropropane, the selectivity is calculated by the ratio between the permeability of hydrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane considered through said membrane M1, i.e. selectivity = [permeability of hydrogen] / [permeability of 1,1,1,2,3,3-hexafluoropropane].

[0043] Preferably, said membrane M1 has a selectivity greater than 4, advantageously greater than 5, preferably greater than 6, more preferably greater than 7, in particular greater than 8, more particularly greater than 9; said selectivity being calculated by the ratio of the permeability of hydrogen to the permeability of 1,1,1,2,3,3-hexafluoropropane through it.In particular, the selectivity of said membrane Ml may be greater than 10, or greater than 15, or greater than 20, or greater than 25, or greater than 30, or greater than 35, or greater than 40, or greater than 45, or greater than 50, or greater than 55, or greater than 60, or greater than 65, or greater than 70, or greater than 75, or greater than 80, or greater than 85 or greater than 90 or greater than 95 or greater than 100 or greater than 105 or greater than 110 or greater than 115 or greater than 120 or greater than 125 or greater than 130 or greater than 135 or greater than 140 or greater than 145 or greater than 150; said selectivity being calculated by the ratio between the permeability of hydrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane M1; preferably when the latter is made of polyolefin or polyether.

[0044] According to a particular embodiment, said membrane M1 has a selectivity greater than 200, advantageously greater than 250, preferably greater than 300, more preferably greater than 400, in particular greater than 500; said selectivity being calculated by the ratio between the permeability of hydrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane M1; preferably when the latter is made of polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0045] According to a preferred embodiment, in the present process, the mixture of step (a) has a mass water content of less than 1000 ppm, advantageously 500 ppm, preferably less than 200 ppm, more preferably less than 100 ppm, in particular less than 50 ppm, more particularly less than 10 ppm based on the total weight of the mixture.

[0046] According to a preferred embodiment, said mixture of step a) is obtained from a hydrogenation reaction of hexafluoropropene, optionally previously purified, preferably by distillation. This is notably detailed below in the section concerning the production of 1,1,1,2,3,3-hexafluoropropane.

[0047] According to a preferred embodiment, said membrane M1 is chosen from a film, a laminated structure, hollow fibers and coated fibers.

[0048] Step (a) can be carried out over a wide range of temperature and pressure.

[0049] Preferably, step (a) of bringing said mixture into contact with said membrane M1 is carried out at a pressure of 0.1 bara to 30 bara, advantageously of 0.2 bara to 25 bara, preferably of 0.3 bara to 20 bara, more preferably of 0.4 bara to 15 bara, in particular of 0.5 bara to 10 bara, more particularly of 0.5 bara to 5 bara.

[0050] Preferably, step (a) of bringing said mixture into contact with said membrane Ml is implemented at a temperature of 0°C to 150°C, advantageously from 0°C to 125°C, preferably from 5°C to 100°C, more preferably from 10 to 75°C, in particular from 10 to 50°C.

[0051] When implementing the method, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The differential pressure expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the differential pressure is from 1 to 3000 kPa, preferably from 50 to 2000 kPa, in particular from 100 to 1000 kPa, more particularly from 100 to 500 kPa.

[0052] Separation of Ll.L2.3.3-hexafluoropropane from nitrogen and / or oxygen

[0053] According to another aspect of the present invention, a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and at least one contaminant selected from the group consisting of nitrogen and oxygen or a mixture thereof is provided.

[0054] Preferably, said method comprises a step (a) of bringing said mixture into contact with a membrane Ml' to form a stream F1' comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2' comprising said at least one contaminant.

[0055] Generally, said membrane Ml' may be made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyaramide, polyamide, polysulfone, polyvinylidene fluoride, poly(methyl methacrylate), polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene tetrafluoroethylene or tetrafluoroethylene / perfluorovinylether copolymer optionally substituted by an SO3H group, a cellulose-based material and a material containing a siloxane functional group.

[0056] According to another particular embodiment, said at least one contaminant is nitrogen. In this case, said membrane Ml' is preferably made of a material selected from the group consisting of polyolefin and polyether. The terms polyolefin and polyether are as defined above. Preferably, said membrane Ml' is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] or poly(phenylene oxide). In particular, said membrane Ml' is made of a material selected from the group consisting of polypropylene or polymethylpentene. Said membrane Ml' preferably has a selectivity greater than 5; said selectivity being calculated by the ratio between the permeability of nitrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane Ml'.Advantageously, said membrane Ml' has a selectivity greater than 10, preferably greater than 20, more preferably greater than 50, in particular greater than 75; said se . lectivity being calculated by the ratio between the permeability of nitrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane Ml'.

[0057] According to another particular embodiment, said at least one contaminant is oxygen. In this case, said membrane Ml' preferably has a selectivity greater than 5; said selectivity being calculated by the ratio between the permeability of oxygen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane Ml'. Advantageously, said membrane Ml' has a selectivity greater than 10, preferably greater than 20, more preferably greater than 50, in particular greater than 75; said selectivity being calculated by the ratio between the permeability of oxygen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane Ml'. Preferably, said membrane Ml' is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyvinylidene fluoride, a cellulose-based material, polyalkylsiloxane and poly(methyl methacrylate).In particular, said membrane Ml' is made of a material selected from the group consisting of polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide).

[0058] Step (a) can be carried out over a wide range of temperature and pressure.

[0059] Preferably, step (a) of bringing said mixture into contact with said membrane Ml' is carried out at a pressure of 0.1 bara to 30 bara, advantageously of 0.2 bara to 25 bara, preferably of 0.3 bara to 20 bara, more preferably of 0.4 bara to 15 bara, in particular of 0.5 bara to 10 bara, more particularly of 0.5 bara to 5 bara.

[0060] Preferably, step (a) of bringing said mixture into contact with said membrane Ml' is carried out at a temperature of 0°C to 150°C, advantageously of 0°C to 125°C, preferably of 5°C to 100°C, more preferably of 10 to 75°C, in particular of 10 to 50°C.

[0061] When implementing the method, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The differential pressure expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the differential pressure is from 1 to 3000 kPa, preferably from 50 to 2000 kPa, in particular from 100 to 1000 kPa, more particularly from 100 to 500 kPa.

[0062] According to a preferred embodiment, in the present process, the mixture of step (a) is in anhydrous form. The term anhydrous refers to a mass content of water of less than 1000 ppm, advantageously 500 ppm, preferably less than 200 ppm, in particular less than 100 ppm based on the total weight of the mixture.

[0063] According to a preferred embodiment, said membrane Ml' is chosen from a film, a laminated structure, hollow fibers and coated fibers.

[0064] According to a particular embodiment, the mass content of said contaminant in said mixture subjected to step (a) is less than 15% based on the total weight of said mixture, advantageously less than 10%, preferably less than 5%, in particular less than 1% based on the total weight of said mixture. According to a particular embodiment, the mass content of 1,1,1,2,3,3-hexafluoropropane in said mixture subjected to step (a) is greater than 50% based on the total weight of said mixture, advantageously greater than 70%, preferably greater than 80%, in particular greater than 90% based on the total weight of said mixture. Preferably, said mixture is in gaseous form.

[0065] The present method thus makes it possible to produce a stream F1' enriched in 1,1,1,2,3,3-hexafluoropropane relative to the initial mixture before contacting with the membrane M1'. Preferably, said stream F1' has a reduced molar content of said contaminant relative to said mixture. According to a preferred embodiment, said stream F1' comprises at least 60% by weight of 1,1,1,2,3,3-hexafluoropropane, advantageously at least 70% by weight of 1,1,1,2,3,3-hexafluoropropane, preferably at least 80% by weight of 1,1,1,2,3,3-hexafluoropropane, more preferably at least 90% by weight of 1,1,1,2,3,3-hexafluoropropane, in particular at least 95% by weight of 1,1,1,2,3,3-hexafluoropropane based on the total weight of said stream F1'. Preferably, said stream Fl' comprises less than 10% by weight of said contaminant based on the total weight of said stream Fl'.Advantageously, said stream F1' comprises less than 5% by weight of said contaminant, preferably less than 1% by weight, in particular less than 0.5% by weight, more particularly less than 0.1% by weight of said contaminant based on the total weight of said stream F1'. In the present method, stream F2' is enriched in said contaminant. According to a preferred embodiment, said stream F2' has an increased molar content of hydrogen relative to said mixture. Preferably, said stream F2' comprises at least 25% by weight of said contaminant, more preferably at least 50% by weight of said contaminant, in particular at least 75% by weight of said contaminant, more particularly at least 80% by weight of said contaminant, preferably at least 95% by weight of said contaminant based on the total weight of said stream F2'.

[0066] Separation of 1.1.1.2.3.3-hexafluoropropane from a mixture comprising nitrogen, hydrogen and optionally oxygen

[0067] According to another aspect, the present invention provides a process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane, nitrogen, hydrogen and optionally oxygen. Preferably, said process comprises a step (a) of contacting said mixture with a membrane M2 to form a stream F3 comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F4 comprising nitrogen, hydrogen and optionally oxygen. In particular, said membrane M2 is made of a material selected from the group consisting of polyolefin and polyether. According to a preferred embodiment, said membrane M2 is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

[0068] Step (a) can be carried out over a wide range of temperature and pressure.

[0069] Preferably, step (a) of bringing said mixture into contact with said membrane M 2 is carried out at a pressure of 0.1 bara to 30 bara, advantageously of 0.2 bara to 25 bara, preferably of 0.3 bara to 20 bara, more preferably of 0.4 bara to 15 bara, in particular of 0.5 bara to 10 bara, more particularly of 0.5 bara to 5 bara.

[0070] Preferably, step (a) of bringing said mixture into contact with said membrane M 2 is carried out at a temperature of 0°C to 150°C, advantageously of 0°C to 125°C, preferably of 5°C to 100°C, more preferably of 10 to 75°C, in particular of 10 to 50°C.

[0071] When implementing the method, a pressure difference is observed between the inlet of the membrane and the outlet of the membrane. The differential pressure expressed here corresponds to the pressure difference existing between the inlet and the outlet of said membrane. Preferably, the differential pressure is from 1 to 3000 kPa, preferably from 50 to 2000 kPa, in particular from 100 to 1000 kPa, more particularly from 100 to 500 kPa.

[0072] According to a preferred embodiment, in the present process, the mixture of step (a) is in anhydrous form. The term anhydrous refers to a water mass content of less than 1000 ppm, advantageously 500 ppm, preferably less than 200 ppm, in particular less than 100 ppm based on the total weight of the mixture.

[0073] According to a preferred embodiment, said membrane M2 is chosen from a film, a laminated structure, hollow fibers and coated fibers.

[0074] Said membrane M2 preferably has a selectivity greater than 5, advantageously greater than 10, preferably greater than 20, more preferably greater than 50, in particular greater than 75; said selectivity being calculated by the ratio between the permeability of nitrogen or hydrogen or oxygen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane M2; as demonstrated above.

[0075] Process for the production and purification of LL1.2.3.3-hexafluoropropane

[0076] According to another aspect, the present invention provides a process for producing 1,1,1,2,3,3-hexafluoropropane. Said process comprises the steps of:

[0077] A. Gas-phase hydrogenation of hexafluoropropene in the presence hydrogen and a hydrogenation catalyst to form an Al stream comprising 1,1,1,2,3,3-hexafluoropropane and unreacted hydrogen; B. Optionally purification of the Al stream to form a purified A2 stream; C. Implementation of the purification method according to the present invention from said stream Al or said stream A2.

[0078] Preferably, the hydrogenation step A) is carried out in the presence of a catalyst. As catalyst, mention may be made in particular of metals such as Pd, Ru, Pt, Rh, Ir, Fe, Co, Ni, Cu, Ag, Re, Os, Au, Ge, Te optionally supported. As support, mention may be made in particular of carbon, alumina, fluorinated alumina, A1F3, oxides, oxyfluorides and fluorides of Cr, Ti, Zr, Mg, Zn, silica and silicon carbide. The amount of metals present in the catalyst, when the latter is supported, may be between 0.001 and 10% by weight, preferably between 0.001 and 1.0% by weight, in particular from 0.01 to 0.2% by weight. The hydrogenation step is advantageously carried out in the presence of Pd supported on alumina, preferably in the alpha polymorphic form.In particular, said hydrogenation catalyst may comprise Pd supported on alumina in the alpha polymorphic form; palladium representing between 0.001 and 1.0% by weight, preferably from 0.01 to 0.2% based on the total weight of the catalyst. The hydrogenation step may be carried out both in the liquid phase and in the gas phase. The gas phase is however preferred.

[0079] The hydrogenation step A) is carried out in the presence of hydrogen, advantageously with a hydrogen / hexafluoropropene molar ratio of between 1 and 50, and particularly of between 2 and 15.

[0080] The hydrogenation step A) is preferably carried out at a temperature of between 50 and 200°C, preferably between 80 and 120°C. Preferably, the temperature at the inlet of the reactor of the hydrogenation step A) is between 30 and 100°C, advantageously between 40 and 80°C.

[0081] The contact time of the hydrogenation step A), defined as the ratio of the volume of the catalytic bed to the volume flow rate of the total flow under normal temperature and pressure conditions, is preferably between 0.1 s and 20 s and advantageously between 0.5 and 5 s.

[0082] The hydrogenation step A) is preferably carried out at an absolute pressure of between 0.5 and 20 bar and advantageously of between 1 and 5 bar.

[0083] Preferably, the hydrogenation step A) is carried out in the presence of a diluent which can be co-introduced with the reactants into the reaction medium. The diluent is an inert gas which does not react under the conditions of the hydrogenation step. As diluent, mention may be made of nitrogen, helium or argon. The molar ratio of diluent / reactants at the inlet of the reactor of the hydrogenation step A) may be between 100:1 and 1:1, preferably between 75:1 and 1:1, advantageously between 50:1 and 1:1.

[0084] In particular, during step A) according to the present invention, the diluent may be the hydrogenation product which is HFC-236ea. In this case, a portion of the gaseous effluent from the reactor comprising HFC-236ea, unreacted hydrogen and optionally unreacted hexafluoropropene is recycled and the other portion of the gaseous effluent from the reactor is subjected to a separation and / or purification step. The gaseous stream comprising the recycling loop and the reactants may be preheated before introduction into the reactor. The portion of the gaseous effluent recycled to the reactor preferably represents at least 90% by volume of the total effluent at the outlet of the reactor, advantageously at least 93% by volume. In a particularly preferred manner, the portion of the effluent recycled to the reactor represents between 94 and 98% by volume of the total effluent at the outlet of the reactor.

[0085] The stream Al may be purified before carrying out step C). The purification may be a drying step. The drying step may be carried out by contacting said stream with a solid absorbent agent. Said solid absorbent may comprise an agent absorbing acid molecules and / or a water absorbent agent. Said water absorbent agent may be an inorganic salt such as magnesium sulfate, calcium sulfate, calcium chloride or may be a molecular sieve of type 3A, 4A, 5A, AW500, XH-7, XH-9 or 13X, silica gel, activated carbon or a mixture thereof.Said acid molecule absorbing agent may be a metal oxide such as aluminum oxide, alkaline earth metal oxide, alkali metal oxide or metal hydroxide such as aluminum hydroxide, alkaline earth metal hydroxide, alkali metal hydroxide, aluminosilicates such as andalusite, kyanite, silimanite, calcium aluminosilicate, sodium aluminosilicate or silica or a mixture thereof. When the drying step is carried out in the presence of a water absorbing agent and an acid molecule absorbing agent, said stream is preferably brought into contact with the acid molecule absorbing agent and then with the water absorbing agent. The acid molecule absorbing agent preferably absorbs hydrofluoric acid.

[0086] According to another embodiment, the purification comprises a step of condensation of the Al stream. The Al stream at the end of the hydrogenation step A) can be subjected to a condensation step under conditions such that the unreacted hydrogen is not condensed and that a portion of HFC-236ea formed in step A) is condensed. Preferably, the condensation step is carried out at a temperature of between 0 and 50°C and at a pressure of between 0.5 and 20 bar absolute, advantageously between 1 and 5 bar absolute. Preferably, the condensation step is carried out under conditions such that between 1 and 30% of HFC-236ea at the outlet of the reactor is condensed and advantageously between 2 and 10% is condensed. The non-condensed fraction can then be recycled to the hydrogenation step A) after possible heating. The non-condensed fraction can be subjected to step C) of the present process. The non-condensed fraction comprises 1,1,1,2,3,3-hexafluoropropane and hydrogen.

[0087] The condensed fraction, thus recovered and purified, can then be evaporated before being sent to step C). The condensed fraction can be said purified stream A2. Before carrying out step C), the condensed fraction can be purified and / or dried. The condensed fraction comprises 1,1,1,2,3,3-hexafluoropropane and hydrogen. However, the hydrogen is preferably present in small proportions.

[0088] According to another embodiment, step B) may be a distillation step for recovering a stream A2 comprising 1,1,1,2,3,3-hexafluoropropane and hydrogen, said stream A2 being enriched in 1,1,1,2,3,3-hexafluoropropane relative to stream A1.

[0089] Alternatively, a distillation step may be implemented after step C). In this case, the stream F1 as defined in the present application may be distilled. Examples

[0090] The permeability of a gaseous compound through a polymer is measured using an Evonik MET Crossflow Filtration Cell (with an inner diameter of 52 mm and an active surface area of 14 cm2) for polymers in film form or a commercial module for polymers in fiber form. The polyimide film is a Dupont Kapton HN film, the polymethylpentene film has the reference MX004, the silicone has the reference USP class VI. The films are supplied by Goodfellow.

[0091] In the examples below, the membranes tested are in the form of a film with an active surface area of 14 cm2 and whose thickness is shown in Table 1 below.

[0092] [Tables 1] Material Thickness Polyimide 25 pm Cellulose acetate 35 pm PMP 50 pm Polypropylene 25 pm PPO 50 pm

[0093] PMP = polymethylpentene; PMMA: polymethyl methacrylate; PPO = poly(phenylene oxide)

[0094] The permeability is calculated according to the following formula: P = Q xex S1 x AP4

[0095] With P: Permeability in cmAs hPa1

[0096] Q: permeate flow rate in cm3 / s

[0097] e: thickness of the membrane in cm

[0098] S: membrane surface in cm2

[0099] AP: Pressure difference across the membrane at P a (i.e. differential pressure mentioned in the present application)

[0100] The permeability is usually expressed in Barrer (10 lo.cm3(STP).cm.cm2.s '.cm Hg ') according to the conversion: PBarrer = P x 1010 / (7.500615 x 10-4)

[0101] Thus, it is possible to calculate the permeability of a compound through a material from the material data (surface area, thickness), the pressure difference across the membrane and the measurement of the permeate flow rate through the membrane. The permeability is thus measured by maintaining a compound under pressure upstream of the membrane in the absence of an outlet on the retentate side, and to measure the flow rate of this same compound at atmospheric pressure on the permeate side. The tests are carried out at a temperature of 25°C except for silicone, the tests of which were carried out at 35°C. The tests are repeated several times, possibly at different pressures, to obtain a more precise permeability value. Unless otherwise stated, the permeability remains constant regardless of the DeltaP (i.e. the pressure difference across the membrane).

[0102] Example 1: Hydrogen / 1,1,1,2,3,3-hexafluoropropane separation

[0103] The experimental protocol detailed above was implemented independently for each compound of the mixture considered: hydrogen (H2) and 1,1,1,2,3,3-hexafluoropropane (HFC-236ea). The membrane used is made of polypropylene, polymethylpentene, poly(phenylene oxide), polyimide. The results are shown in Table 2 below. The permeability value is expressed in Barrer. The selectivity mentioned in the table corresponds to the ratio between the permeability measured for the two species considered.

[0104] [Tables2] Permeability (Barrer) Selectivity H2 HFC-236ea H2 / HFC-236ea PP 5.7 0.1 57 PMP 130 0.1 1300 Polyimide 2.8 0.5 5.6 PPO 118833 136 874

[0105] PP = polypropylene; PMP = polymethylpentene; PPO = poly(phenylene oxide)

[0106] As shown in the above data, polyolefin or polyether membranes are more permeable to hydrogen than to 1,1,1,2,3,3-hexafluoropropane. Polyolefin (polypropylene, polyethylene or polymethylpentene) or polyether membranes therefore allow efficient separation of hydrogen from HFC-236ea.

[0107] Example 2: Nitrogen or oxygen separation / HFC-236ea

[0108] The experimental protocol detailed above was implemented independently for each compound of the mixture considered: nitrogen (N2), oxygen (02), 1,1,1,2,3,3-hexafluoropropane (HFC-236ea). The membrane used is made of polymethylpentene or polypropylene. The results are shown in Table 3 below. The permeability value is expressed in Barrer. The selectivity mentioned in the table corresponds to the ratio between the permeability measured for the two species considered.

[0109] [Tables3] Permeability (Barrer) Selectivity N2 02 HFC-236ea N2 / HFC-236ea O2 / HFC-236ea PP 3 13 0.1 30 130 PMP 9 32 0.1 90 320

[0110] The above results show that polyolefin membranes are permeable to nitrogen or oxygen rather than to 1,1,1,2,3,3-hexafluoropropane. Similar results were obtained with a PPO membrane. Thus, polyolefin and polyether membranes can separate nitrogen and oxygen from 1,1,1,2,3,3-hexafluoropropane.

Claims

Claims

1. A process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and hydrogen; said process comprising a step (a) of contacting said mixture with a membrane M1 to form a stream F1 comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2 comprising hydrogen, characterized in that said membrane M1 is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyvinylidene fluoride, a cellulose-based material and poly(methyl methacrylate).

2. Method according to the preceding claim, characterized in that said membrane M1 is made of a material selected from the group consisting of polyolefin and polyether.

3. Method according to the preceding claim characterized in that said membrane M1 is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).

4. Method according to the preceding claim characterized in that said membrane M1 has a selectivity greater than 100; said selectivity being calculated by the ratio between the permeability of hydrogen and the permeability of said 1,1,1,2,3,3-hexafluoropropane through said membrane M1; preferably the selectivity is greater than 250, in particular greater than 500.

5. A method according to any one of the preceding claims characterized in that said mixture contains less than 100 ppm of water based on the total weight of said mixture.

6. A method according to any one of the preceding claims, characterized in that the mass content of hydrogen in said mixture is less than 25% by weight based on the total weight of said mixture.

7. Process according to any one of the preceding claims, characterized in that said mixture is obtained from a hydrogenation reaction of hexafluoropropene, optionally previously purified, preferably by distillation.

8. A process for producing 1,1,1,2,3,3-hexafluoropropane comprising the steps of: A. Gas-phase hydrogenation of hexafluoropropene in the presence of hydrogen and a hydrogenation catalyst for forming a stream Al comprising 1,1,1,2,3,3-hexafluoropropane and unreacted hydrogen; B. Optionally purifying the stream Al to form a purified stream A2 C. Implementing the purification method according to any one of claims 1 to 7 from said stream Al or said stream A2.

9. A process for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and at least one contaminant selected from the group consisting of nitrogen and oxygen or a mixture thereof; said process comprising a step (a) of contacting said mixture with a membrane Ml' to form a stream Fl' comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2' comprising said at least one contaminant.

10. Method according to the preceding claim, characterized in that said membrane Ml' is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyaramide, polyamide, polysulfone, polyvinylidene fluoride, poly(methyl methacrylate), polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylenetetrafluoroethylene or tetrafluoroethylene / perfluorovinylether copolymer optionally substituted by an SO3H group, a cellulose-based material and a material containing a siloxane functional group.

11. Method according to the preceding claim characterized in that said contaminant is oxygen and said membrane Ml' is made of a material selected from the group consisting of polyolefin, polyether, polyimide, polyvinylidene fluoride, a cellulose-based material, polyalkylsiloxane and poly(methyl methacrylate).

12. Method according to the preceding claim characterized in that said membrane Ml' is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)], poly(phenylene oxide), cellulose acetate, polyimide and polydimethylsiloxane.

13. Method according to any one of claims 11 or 12 characterized in that said contaminant is nitrogen and said membrane Ml' is in a material selected from the group consisting of polyolefin and polyether, preferably polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] or poly(phenylene oxide); in particular polypropylene, poly(phenylene oxide) or polymethylpentene.

14. Method according to any one of the preceding claims 11 to 15 characterized in that the mass content of said contaminant in said mixture is less than 5% based on the total weight of said mixture, preferably less than 1% based on the total weight of said mixture.

15. A method for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane, nitrogen, hydrogen and optionally oxygen; said method comprising a step (a) of contacting said mixture with a membrane M2 to form a stream F3 comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F4 comprising nitrogen, hydrogen and optionally oxygen; said membrane M2 being made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy-(2,6-dimethyl-1,4-phenylene)] and poly(phenylene oxide).