Process for 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

Technical Field

[0001] The present invention relates to a method for purifying hydrofluoroalkanes. Preferably, the present invention relates to a method for purifying hydrofluoroalkanes by membrane separation. Background Art

[0002] 1,1,1,2,3,3-Hexafluoropropane (HFC-236ea) is a hydrofluorocarbon and has been described as a starting material for the preparation of 1,1,1,2,3-pentafluoropropene or as an intermediate in the preparation of 1,1,1,2,3-pentafluoropropane and / or 2,3,3,3-tetrafluoropropene. Mention may in particular be made of documents US 5679875, US 539600, US 8359964 and US 8389779.

[0003] It can be prepared by high temperature pyrolysis of chlorodifluoromethane (CHClF2) in the presence of 1,1,1,2-tetrafluoroethane. Mention may be made, for example, of document WO 1996029296.

[0004] 1,1,1,2,3,3-Hexafluoropropane can also be prepared by a process during which at least one tetrafluorochloropropene is obtained by 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. The tetrafluorochloropropenes 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)) are then subsequently fluorinated in the presence of a catalyst to provide HFC-236ea. Mention may be made, for example, of document US 5532418.

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

[0006] In particular, 1,1,1,2,3,3-hexafluoropropane can be prepared by catalytic hydrogenation of hexafluoropropylene. The reaction is usually carried out with an excess of hydrogen. The hydrogen is usually removed by several distillation steps and a drying step before the distillation.

[0007] 1,1,1,2,3,3-Hexafluoropropane can be used as a cleaning agent in the semiconductor industry. In such applications, 1,1,1,2,3,3-Hexafluoropropane must be of high purity. Therefore, it is desirable to provide a method for purifying 1,1,1,2,3,3-Hexafluoropropane that can remove certain contaminants generated by its preparation process. Summary of the invention

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

[0009] According to a preferred embodiment, said membrane M1 is made of a material selected from polyolefins and polyethers.

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

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

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

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

[0014] According to a preferred embodiment, the mixture is obtained from the hydrogenation of hexafluoropropylene, which has optionally been purified beforehand, preferably by distillation.

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

[0016] A) gas-phase hydrogenation of hexafluoropropylene in the presence of hydrogen and a hydrogenation catalyst to form a stream A1 comprising 1,1,1,2,3,3-hexafluoropropane and unreacted hydrogen;

[0017] B) optionally purifying stream A1 to form purified stream A2;

[0018] C) Using the stream A1 or the stream A2 to carry out the purification process according to the invention.

[0019] According to another aspect, the present invention relates to a method 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 chosen from nitrogen and oxygen or mixtures thereof, said method comprising a step (a) of contacting said mixture with a membrane M1' so as to form a stream F1' comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2' comprising said at least one contaminant.

[0020] According to a preferred embodiment, the membrane M1' is made of a material chosen from polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, poly(methyl methacrylate), polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene or tetrafluoroethylene / perfluorovinyl ether copolymers, which are optionally substituted with SO3H groups, cellulose-based materials and materials containing siloxane functional groups.

[0021] According to a preferred embodiment, the pollutant is oxygen and the membrane M1 ′ is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyvinylidene fluoride, cellulose-based materials, polyalkylsiloxanes and poly(methyl methacrylate).

[0022] According to a preferred embodiment, the membrane M1 ′ is made of a material selected from polyethylene, polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], polyphenylene ether, cellulose acetate, polyimide and polydimethylsiloxane.

[0023] According to a preferred embodiment, the pollutant is nitrogen and the membrane M1' is made of a material selected from olefins and polyethers, preferably polyethylene, polypropylene, polymethylpentene, poly[[oxy(2,6-dimethyl-1,4-phenylene)] or polyphenylene ether, in particular polypropylene, polyphenylene ether or polymethylpentene.

[0024] According to a preferred embodiment, the mass content of the pollutant in the mixture is less than 5% based on the total weight of the mixture, preferably less than 1% based on the total weight of the mixture.

[0025] According to another aspect, the present invention relates to 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, the method comprising a step (a) of contacting the mixture with a membrane M2 to form a stream F3 comprising the 1,1,1,2,3,3-hexafluoropropane and a stream F4 comprising nitrogen, hydrogen and optionally oxygen, the 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 polyphenylene ether. DETAILED DESCRIPTION

[0026] Separation of 1,1,1,2,3,3-hexafluoropropane and hydrogen

[0027] According to a first aspect, the present invention relates to a method for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and hydrogen. The method comprises a step (a) of contacting the mixture with a membrane M1 to form a stream F1 comprising the 1,1,1,2,3,3-hexafluoropropane and a stream F2 comprising hydrogen.

[0028] Preferably, the mixture comprises less than 50%, preferably less than 25%, in particular less than 15% molar content of hydrogen, based on the total molar amount of the mixture. Preferably, the mixture comprises more than 0.5%, preferably more than 1% molar content of hydrogen, based on the total molar amount of the mixture.

[0029] Preferably, the mixture is in gaseous form.

[0030] The present process thus makes it possible to produce a stream F1 enriched in 1,1,1,2,3,3-hexafluoropropane relative to the initial mixture before contact with the membrane. Preferably, said stream F1 has a reduced molar content of hydrogen relative to said mixture.

[0031] According to a preferred embodiment, the 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 the stream F1.

[0032] Preferably, the stream F1 comprises less than 20% hydrogen, based on the total weight of the stream F1. Advantageously, the stream F1 comprises less than 15% by weight of hydrogen, preferably less than 10% by weight, in particular less than 5% by weight, more in particular less than 1% by weight of hydrogen, based on the total weight of the stream F1.

[0033] In the present process, stream F2 is enriched in 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, advantageously at least 95% by weight of hydrogen, based on the total weight of said stream F2.

[0034] In this patent application, the term membrane refers to a membrane that is selectively permeable to one or more compounds, making it possible for different compounds to migrate through the membrane at different flow rates. The membrane restricts the movement of molecules across it, causing some molecules to move more slowly than other molecules or to be completely excluded (that is, impermeable). For example, the membrane may be selectively permeable to hydrogen and impermeable (or weakly permeable) to 1,1,1,2,3,3-hexafluoropropane.

[0035] The permeability 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 within a wide range of solubility parameters and molecular sizes, from macromolecular materials to simple ionic or covalent compounds. The determining property of the performance quality of a membrane is primarily selectivity. The membrane separation process is characterized by the fact that the feed stream is divided into two streams: the retentate and the permeate. The retentate is the portion of the feed that does not pass through (or only slightly passes through) the membrane, while the permeate is the portion of the feed that passes through the membrane.

[0036] In this patent application, the retentate may be one of the streams described as a function of the membrane used and the compound considered.

[0037] Unlike distillation methods, membrane separation does not require phase separation, which generally enables significant energy savings compared to distillation methods. Since membrane separation methods generally have no moving parts, no complex control schemes, and few ancillary equipment items, capital costs can also be reduced compared to other separation methods known in the art.

[0038] Membranes can be produced with extremely high selectivity for the components to be separated. Typically, the values ​​of selectivity are much higher than the typical values ​​of relative volatility for distillation operations. Membrane separation methods are also able to recover small but valuable components from the mainstream without significant energy costs. Since membrane methods require the use of relatively simple and harmless materials, membrane separation methods may be better for the environment.

[0039] According to a preferred embodiment, the membrane M1 is made of a material selected from polyolefins, polyethers, polyimides, polyvinylidene fluoride, cellulose-based materials and poly(methyl methacrylate). Preferably, the membrane M1 is made of a material selected from polyolefins and polyethers. In particular, the membrane M1 is made of a material selected from polyethylene, polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)] and polyphenylene ether.

[0040] In the present patent application, the term polyether refers in particular to polyethers comprising the monomer units -[-O-Ar-]- or -[-Ar 1 -O-Ar 2 -]- polyarylether, wherein Ar, Ar 1 and Ar 2 Ar is independently an aromatic ring containing 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 polyphenylene ether.

[0041] In the present patent application, the term cellulose refers to a polymer consisting of a linear chain of D-glucose units, the hydroxyl functions of which are optionally partially or non-partially substituted. The hydrogen of one or more hydroxyl groups may be substituted by -C(O)-R or by a C1-C5 alkyl group optionally substituted by an OH, CO2H, CO2R group, wherein R=C1-C5 alkyl. Preferably, the cellulose is cellulose acetate.

[0042] In the present patent application, the term polyolefin refers in particular to polyethylene, polypropylene, polymethpropylene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene and polyethylbutene.

[0043] Generally, when the selectivity is greater than 2, it can be considered that there is a separation between hydrogen and 1,1,1,2,3,3-hexafluoropropane. The higher the selectivity, the more efficient the separation. When the selectivity is greater than or equal to 5, preferably greater than or equal to 10, especially greater than or equal to 20, the process is particularly efficient.

[0044] When the permeability of the membrane M1 for hydrogen is greater than the permeability of the membrane M1 for 1,1,1,2,3,3-hexafluoropropane, the selectivity is calculated by the ratio of the permeability of hydrogen through the membrane M1 to the permeability of the 1,1,1,2,3,3-hexafluoropropane under consideration through the membrane M1, i.e., selectivity = [permeability of hydrogen] / [permeability of 1,1,1,2,3,3-hexafluoropropane].

[0045] Preferably, the membrane M1 has a selectivity greater than 4, advantageously greater than 5, preferably greater than 6, more preferably greater than 7, particularly greater than 8, more particularly greater than 9, the selectivity being calculated as the ratio of the permeability of hydrogen through the membrane to the permeability of 1,1,1,2,3,3-hexafluoropropane through the membrane. In particular, preferably when the membrane is made of polyolefin or polyether, the selectivity of the membrane M1 can 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, and the selectivity is calculated by the ratio of the permeability of hydrogen through the membrane M1 to the permeability of the 1,1,1,2,3,3-hexafluoropropane through the membrane M1.

[0046] According to a specific embodiment, preferably when the membrane is made of polymethylpentene, poly[[oxy(2,6-dimethyl-1,4-phenylene)] and polyphenylene ether, the 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, the selectivity being calculated by the ratio of the permeability of hydrogen through the membrane M1 to the permeability of 1,1,1,2,3,3-hexafluoropropane through the membrane M1.

[0047] According to a preferred embodiment, in the present process, the mixture of step (a) has a mass content of water 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.

[0048] According to a preferred embodiment, the mixture of step a) is obtained by hydrogenation of hexafluoropropylene, which is optionally purified beforehand, preferably by distillation. This is described in particular detail below in the section on the production of 1,1,1,2,3,3-hexafluoropropane.

[0049] According to a preferred embodiment, the membrane M1 is selected from thin films, laminate structures, hollow fibers and coated fibers.

[0050] Step (a) can be carried out within a wide range of temperature and pressure.

[0051] Preferably, step (a) of contacting said mixture with said membrane M1 is carried out at a pressure ranging from 0.1 to 30 bara, advantageously from 0.2 to 25 bara, preferably from 0.3 to 20 bara, more preferably from 0.4 to 15 bara, in particular from 0.5 to 10 bara, more particularly from 0.5 to 5 bara.

[0052] Preferably, step (a) of contacting said mixture with said membrane M1 is carried out at a temperature ranging from 0 to 150°C, advantageously from 0 to 125°C, preferably from 5 to 100°C, more preferably from 10 to 75°C, in particular from 10 to 50°C.

[0053] During the implementation of 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 the membrane. Preferably, the differential pressure is 1 to 3000 kPa, preferably 50 to 2000 kPa, particularly 100 to 1000 kPa, more particularly 100 to 500 kPa.

[0054] Separation of 1,1,1,2,3,3-hexafluoropropane from nitrogen and / or oxygen

[0055] According to another aspect of the present invention, there is provided a method 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 nitrogen and oxygen or a mixture thereof.

[0056] Preferably, the method comprises a step (a) of contacting said mixture with a membrane M1 ' so as to form a stream F1 ' comprising said 1,1,1,2,3,3-hexafluoropropane and a stream F2' comprising at least one contaminant.

[0057] In general, the membrane M1' can be made of a material selected from polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, poly(methyl methacrylate), polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene or tetrafluoroethylene / perfluorovinyl ether copolymers, which are optionally substituted with SO3H groups, cellulose-based materials and materials containing siloxane functional groups.

[0058] According to another specific embodiment, the at least one pollutant is nitrogen. In this case, the membrane M1' is preferably made of a material selected from polyolefins and polyethers. The terms polyolefins and polyethers are as defined above. Preferably, the membrane M1' is made of a material selected from polyethylene, polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)] or polyphenylene ether. In particular, the membrane M1' is made of a material selected from polypropylene or polymethylpentene. The membrane M1' preferably has a selectivity greater than 5, the selectivity being calculated by the ratio of the permeability of nitrogen through the membrane M1' to the permeability of the 1,1,1,2,3,3-hexafluoropropane through the membrane M1'. Advantageously, the membrane M1' has a selectivity greater than 10, preferably greater than 20, more preferably greater than 50, and particularly greater than 75, the selectivity being calculated by the ratio of the permeability of nitrogen through the membrane M1' to the permeability of the 1,1,1,2,3,3-hexafluoropropane through the membrane M1'.

[0059] According to another specific embodiment, the at least one pollutant is oxygen. In this case, the membrane M1' preferably has a selectivity greater than 5, the selectivity being calculated by the ratio of the permeability of oxygen through the membrane M1' to the permeability of the 1,1,1,2,3,3-hexafluoropropane through the membrane M1'. Advantageously, the membrane M1' has a selectivity greater than 10, preferably greater than 20, more preferably greater than 50, and particularly greater than 75, the selectivity being calculated by the ratio of the permeability of oxygen through the membrane M1' to the permeability of the 1,1,1,2,3,3-hexafluoropropane through the membrane M1'. Preferably, the membrane M1' is made of a material selected from polyolefins, polyethers, polyimides, polyvinylidene fluoride, cellulose-based materials, polyalkylsiloxanes and poly(methyl methacrylate). In particular, the membrane M1' is made of a material selected from polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)] and polyphenylene ether.

[0060] Step (a) can be carried out within a wide range of temperature and pressure.

[0061] Preferably, step (a) of contacting said mixture with said membrane M1 'is carried out at a pressure of 0.1 to 30 bara, advantageously 0.2 to 25 bara, preferably 0.3 to 20 bara, more preferably 0.4 to 15 bara, in particular 0.5 to 10 bara, more particularly 0.5 to 5 bara.

[0062] Preferably, step (a) of contacting said mixture with said membrane M1 'is carried out at a temperature ranging from 0 to 150°C, advantageously from 0 to 125°C, preferably from 5 to 100°C, more preferably from 10 to 75°C, in particular from 10 to 50°C.

[0063] During the implementation of 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 the membrane. Preferably, the differential pressure is 1 to 3000 kPa, preferably 50 to 2000 kPa, particularly 100 to 1000 kPa, more particularly 100 to 500 kPa.

[0064] According to a preferred embodiment, in the present method, the mixture of step (a) is in anhydrous form. The term anhydrous means 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.

[0065] According to a preferred embodiment, the membrane M1 ′ is selected from thin films, laminate structures, hollow fibers and coated fibers.

[0066] According to a particular embodiment, the mass content of the pollutant in the mixture subjected to step (a) is less than 15% based on the total weight of the mixture, advantageously less than 10%, preferably less than 5%, in particular less than 1% based on the total weight of the mixture. According to a particular embodiment, the mass content of 1,1,1,2,3,3-hexafluoropropane in the mixture subjected to step (a) is greater than 50% based on the total weight of the mixture, advantageously greater than 70%, preferably greater than 80%, in particular greater than 90%. Preferably, the mixture is in gaseous form.

[0067] Thus, the present process makes it possible to produce a stream F1 'enriched in 1,1,1,2,3,3-hexafluoropropane relative to the initial mixture before contact 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 F1 ' comprises less than 10% by weight of said contaminant, based on the total weight of said stream F1 '. Advantageously, the stream F1 ' comprises less than 5% by weight of said pollutants, preferably less than 1% by weight, in particular less than 0.5% by weight, more particularly less than 0.1% by weight of said pollutants, based on the total weight of the stream F1 '. In the present method, the stream F2' is enriched with said pollutants. According to a preferred embodiment, the stream F2' has an increased molar content of hydrogen relative to the mixture. Preferably, the stream F2' comprises at least 25% by weight of said pollutants, more preferably at least 50% by weight of said pollutants, in particular at least 75% by weight of said pollutants, more particularly at least 80% by weight of said pollutants, advantageously at least 95% by weight of said pollutants, based on the total weight of the stream F2'.

[0068] Separation of 1,1,1,2,3,3-hexafluoropropane from a mixture comprising nitrogen, hydrogen and optionally oxygen

[0069] According to another aspect, the present invention provides 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. Preferably, the method comprises a step (a) of contacting the mixture with a membrane M2 to form a stream F3 comprising the 1,1,1,2,3,3-hexafluoropropane and a stream F4 comprising nitrogen, hydrogen and optionally oxygen. In particular, the membrane M2 is made of a material selected from polyolefins and polyethers. According to a preferred embodiment, the membrane M2 is made of a material selected from polyethylene, polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)] and polyphenylene ether.

[0070] Step (a) can be carried out within a wide range of temperature and pressure.

[0071] Preferably, step (a) of contacting said mixture with said membrane M2 is carried out at a pressure ranging from 0.1 to 30 bara, advantageously from 0.2 to 25 bara, preferably from 0.3 to 20 bara, more preferably from 0.4 to 15 bara, in particular from 0.5 to 10 bara, more particularly from 0.5 to 5 bara.

[0072] Preferably, step (a) of contacting said mixture with said membrane M2 is carried out at a temperature ranging from 0 to 150°C, advantageously from 0 to 125°C, preferably from 5 to 100°C, more preferably from 10 to 75°C, in particular from 10 to 50°C.

[0073] During the implementation of 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 the membrane. Preferably, the differential pressure is 1 to 3000 kPa, preferably 50 to 2000 kPa, particularly 100 to 1000 kPa, more particularly 100 to 500 kPa.

[0074] According to a preferred embodiment, in the present method, the mixture of step (a) is in anhydrous form. The term anhydrous means 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.

[0075] According to a preferred embodiment, the membrane M2 is selected from thin films, laminate structures, hollow fibers and coated fibers.

[0076] The 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, the selectivity being calculated by the ratio of the permeability of nitrogen or hydrogen or oxygen through the membrane M2 to the permeability of the 1,1,1,2,3,3-hexafluoropropane through the membrane M2, as indicated above.

[0077] Process for the production and purification of 1,1,1,2,3,3-hexafluoropropane

[0078] According to another aspect, the present invention provides a method for producing 1,1,1,2,3,3-hexafluoropropane. The method comprises the following steps:

[0079] A) gas-phase hydrogenation of hexafluoropropylene in the presence of hydrogen and a hydrogenation catalyst to form a stream A1 comprising 1,1,1,2,3,3-hexafluoropropane and unreacted hydrogen;

[0080] B) optionally purifying stream A1 to form purified stream A2;

[0081] C) Using the stream A1 or the stream A2 to carry out the purification process according to the invention.

[0082] Preferably, the hydrogenation step A) is carried out in the presence of a catalyst. As catalyst, mention may be made in particular of optionally supported metals such as Pd, Ru, Pt, Rh, Ir, Fe, Co, Ni, Cu, Ag, Re, Os, Au, Ge, Te. As supports, mention may be made in particular of carbon, alumina, fluorinated alumina, AlF3, oxides, oxyfluorides and fluorides of Cr, Ti, Zr, Mg and Zn, silicon dioxide and silicon carbide. When the catalyst is supported, the amount of metal present in the catalyst may be from 0.001% to 10% by weight, preferably from 0.001% to 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, which is supported on alumina, which is preferably in the alpha polymorphic form. In particular, the hydrogenation catalyst may comprise Pd supported on alumina in the alpha polymorphic form, with 0.001 to 1.0 wt %, preferably 0.01 to 0.2 wt %, based on the total weight of the catalyst. The hydrogenation step may be carried out in the liquid phase or in the gas phase. However, the gas phase is preferred.

[0083] The hydrogenation step A) is carried out in the presence of hydrogen, advantageously in a hydrogen / hexafluoropropylene molar ratio ranging from 1 to 50, most particularly from 2 to 15.

[0084] The hydrogenation step A) is preferably carried out at a temperature ranging from 50 to 200° C., preferably from 80 to 120° C. Preferably, the temperature at the inlet of the reactor for the hydrogenation step A) is from 30 to 100° C., advantageously from 40 to 80° C.

[0085] The contact time of the hydrogenation step A) (defined as the ratio of the volume of the catalyst bed to the volume flow rate of the total flow at standard temperature and pressure conditions) is preferably between 0.1 and 20 seconds and advantageously between 0.5 and 5 seconds.

[0086] The hydrogenation step A) is preferably carried out at a pressure of from 0.5 to 20 bar absolute and advantageously at a pressure of from 1 to 5 bar absolute.

[0087] Preferably, the hydrogenation step A) is carried out in the presence of a diluent, which can be introduced into the reaction medium together with the reactants. The diluent is an inert gas which is unreactive under the conditions of the hydrogenation step. As diluents, nitrogen, helium or argon may be mentioned. The molar ratio of diluent / reactants at the reactor inlet for 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.

[0088] In particular, during step A) according to the present invention, the diluent may be a hydrogenation product, which is HFC-236ea. In this case, a portion of the gaseous effluent obtained from the reactor comprising HFC-236ea, unreacted hydrogen and possibly unreacted hexafluoropropylene is recycled, and the other portions of the gaseous effluent obtained from the reactor are subjected to separation and / or purification steps. The gas stream comprising a recycle loop and reactants may be preheated before being introduced into the reactor. The portion of the gaseous effluent recycled into the reactor preferably accounts for at least 90 volume %, advantageously at least 93 volume % of the total effluent at the reactor outlet. Particularly preferably, the portion of the effluent recycled into the reactor accounts for 94 volume % to 98 volume % of the total effluent at the reactor outlet.

[0089] The material stream A1 can be purified before step C). The purification can be a drying step. The drying step can be carried out by contacting the material stream with a solid absorbent. The solid absorbent may contain a reagent and / or a water absorbent that absorbs acidic molecules. The water absorbent may be an inorganic salt, such as magnesium sulfate, calcium sulfate, calcium chloride, or may be a 3A, 4A, 5A, AW500, XH-7, XH-9 or 13X molecular sieve, silica gel, activated carbon or a mixture thereof. The reagent that absorbs acidic molecules may be a metal oxide (such as aluminum oxide), an alkaline earth metal oxide, an alkali metal oxide or a metal hydroxide (such as aluminum hydroxide), an alkaline earth metal hydroxide, an alkali metal hydroxide, an aluminosilicate (such as andalusite, kyanite, sillimanite, calcium aluminosilicate, sodium aluminosilicate), or silicon dioxide or a mixture thereof. When the drying step is carried out in the presence of a water absorbent and a reagent that absorbs acidic molecules, the material stream is preferably contacted with a reagent that absorbs acidic molecules and then contacted with a water absorbent. The reagent that absorbs acidic molecules preferably absorbs hydrofluoric acid.

[0090] According to another embodiment, the purification comprises a step of condensing the stream A1. At the end of the hydrogenation step A), the stream A1 can be subjected to a condensation step under conditions such that the unreacted hydrogen is not condensed and a portion of the HFC-236a formed in step A) is condensed. Preferably, the condensation step is carried out at a temperature of 0 to 50° C. and a pressure of 0.5 to 20 bar absolute, advantageously 1 to 5 bar absolute. Preferably, the condensation step is carried out under conditions such that 1% to 30% of the HFC-236ea leaving the reactor is condensed, advantageously 2% to 10%. The uncondensed fraction can then be recycled to the hydrogenation step A) after optional heating. The uncondensed fraction can be subjected to step C) of the present method. The uncondensed fraction contains 1,1,1,2,3,3-hexafluoropropane and hydrogen.

[0091] The condensed fraction thus collected and purified can then be evaporated before being sent to step C). The condensed fraction can be the purified stream A2. Before carrying out step C), the condensed fraction can be purified and / or dried. The condensed fraction contains 1,1,1,2,3,3-hexafluoropropane and hydrogen. However, hydrogen is preferably present in a small proportion.

[0092] According to another embodiment, step B) can 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.

[0093] Alternatively, a distillation step may be carried out after step C). In this case, stream F1 as defined in the present application may be distilled.

[0094] Example

[0095] For polymers in film form, an Evonik MET Crossflow Filtration Cell (52 mm inner diameter, 14 cm active surface area) was used. 2 ) or for polymers in fiber form, the permeability of gaseous compounds through the polymers was measured using commercial modules. The polyimide membrane was Dupont Kapton HN film, the polymethylpentene film had the reference number MX004, and the silicone had the reference number USP Class VI. The membranes were supplied by Goodfellow.

[0096] In the following examples, the membrane tested was an active surface area of ​​14 cm 2 The film forms and thicknesses thereof are shown in Table 1 below.

[0097] [Table 1]

[0098] Material thickness Polyimide 25μm Cellulose acetate 35μm PMP 50μm Polypropylene 25μm PPO 50μm

[0099] PMP = polymethylpentene; PMMA: polymethyl methacrylate; PPO = polyphenylene oxide

[0100] The permeability is calculated according to the following formula: P = Q xex S -1 xΔP -1

[0101] Where P: permeability, in cm 2 .s -1 .Pa -1 count

[0102] Q: Permeate flow rate, in cm 3 / s meter

[0103] e: film thickness, in cm

[0104] S: Surface area of ​​the membrane, in cm 2 count

[0105] ΔP: Transmembrane pressure difference, in Pa (i.e., differential pressure referred to in this patent application)

[0106] Permeability is usually calculated in barrer (10 -10 .cm 3 (STP).cm.cm 2 .s -1 .cmHg -1 )express:

[0107] P barrer =P x 10 10 / (7.500615x 10 -4 )

[0108] Therefore, the permeability of a compound through a material can be calculated from the data of the material (surface area, thickness), the transmembrane pressure difference and the measurement of the permeate flow rate through the membrane. Therefore, the permeability is measured by keeping the compound upstream of the membrane under pressure without an outlet on the retentate side and measuring the flow rate of the same compound at atmospheric pressure on the permeate side. The pressure difference corresponds to the difference between the pressure upstream of the membrane and the pressure downstream of the membrane (in this case, atmospheric pressure). The test is carried out at a temperature of 25°C, except for silicone, which is tested at 35°C. The test is optionally repeated several times at different pressures to obtain a more accurate permeability value. Unless otherwise stated, the permeability remains constant regardless of ΔP (i.e., transmembrane pressure difference).

[0109] Example 1: Hydrogen / 1,1,1,2,3,3-hexafluoropropane separation

[0110] The experimental protocol detailed above was used independently for each compound of the mixture under consideration: hydrogen (H2) and 1,1,1,2,3,3-hexafluoropropane (HFC-236ea). The membranes used were made of polypropylene, polymethylpentene, polyphenylene oxide, polyimide. The results are shown in Table 2 below. The permeability values ​​are expressed in barrers. The selectivity mentioned in the table corresponds to the ratio of the permeabilities measured for the two substances under consideration.

[0111] [Table 2]

[0112]

[0113] PP = polypropylene; PMP = polymethylpentene; PPO = polyphenylene oxide

[0114] As shown in the above data, the membrane made of polyolefin or polyether has a higher permeability to hydrogen than to 1,1,1,2,3,3-hexafluoropropane. Therefore, polyolefin (polypropylene, polyethylene or polymethylpentene) type or polyether type membrane can effectively separate hydrogen from HFC-236ea.

[0115] Example 2: Nitrogen or oxygen / HFC-236ea separation

[0116] The experimental protocol detailed above was used independently for each compound of the mixture considered: nitrogen (N2), oxygen (O2), 1,1,1,2,3,3-hexafluoropropane (HFC-236ea). The membranes used were made of polymethylpentene or polypropylene. The results are shown in Table 3 below. The permeability values ​​are expressed in barrers. The selectivity mentioned in the table corresponds to the ratio of the permeabilities measured for the two substances considered.

[0117] [Table 3]

[0118]

[0119] The above results show that the membrane made of polyolefin is permeable to nitrogen and oxygen, but not to 1,1,1,2,3,3-hexafluoropropane. Similar results were obtained with the membrane made of PPO. Therefore, the membrane made of polyolefin and polyether makes it possible to separate nitrogen and oxygen from 1,1,1,2,3,3-hexafluoropropane.

Claims

1. A method for purifying 1,1,1,2,3,3-hexafluoropropane from a mixture comprising 1,1,1,2,3,3-hexafluoropropane and hydrogen, said method 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 The membrane M1 is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyvinylidene fluoride, cellulose-based materials, and poly(methyl methacrylate).

2. The method according to the preceding claim, characterized in that The membrane M1 is made of a material selected from polyolefins and polyethers.

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

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

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

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

7. The method according to any one of the preceding claims, characterized in that The mixture is obtained from the hydrogenation of hexafluoropropylene which has optionally been purified beforehand, preferably by distillation.

8. A method for producing 1,1,1,2,3,3-hexafluoropropane, comprising the following steps: A) gas-phase hydrogenation of hexafluoropropylene in the presence of hydrogen and a hydrogenation catalyst to form a stream A1 comprising 1,1,1,2,3,3-hexafluoropropane and unreacted hydrogen; B) optionally purifying stream A1 to form purified stream A2; C) using the material stream A1 or the material stream A2 to carry out the purification process according to any one of claims 1 to 7.

9. A method 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 chosen from nitrogen and oxygen or mixtures thereof, the method comprising a step (a) of contacting the mixture with a membrane M1' to form a stream F1' comprising the 1,1,1,2,3,3-hexafluoropropane and a stream F2' comprising the at least one contaminant.

10. The method according to the preceding claim, characterized in that The membrane M1' is made of a material selected from polyolefins, polyethers, polyimides, polyaramids, polyamides, polysulfones, polyvinylidene fluoride, poly(methyl methacrylate), polytetrafluoroethylene, polyvinyl fluoride, polychlorotrifluoroethylene, polyethylene-tetrafluoroethylene or tetrafluoroethylene / perfluorovinyl ether copolymers, which are optionally substituted with SO3H groups, cellulose-based materials and materials containing siloxane functional groups.

11. The method according to the preceding claim, characterized in that The contaminant is oxygen, and the membrane M1' is made of a material selected from the group consisting of polyolefins, polyethers, polyimides, polyvinylidene fluoride, cellulose-based materials, polyalkylsiloxanes, and poly(methyl methacrylate).

12. The method according to the preceding claim, characterized in that The film M1 ′ is made of a material selected from the group consisting of polyethylene, polypropylene, polymethylpentene, poly[oxy(2,6-dimethyl-1,4-phenylene)], polyphenylene ether, cellulose acetate, polyimide and polydimethylsiloxane.

13. The method according to any one of claims 11 and 12, characterized in that The pollutant is nitrogen and the membrane M1' is made of a material selected from polyolefins and polyethers, preferably polyethylene, polypropylene, polymethylpentene, poly[[oxy(2,6-dimethyl-1,4-phenylene)] or polyphenylene ether, in particular polypropylene, polyphenylene ether or polymethylpentene.

14. The method according to any one of the preceding claims 11 to 15, characterized in that The mass content of the pollutant in the mixture is less than 5% based on the total weight of the mixture, preferably less than 1% based on the total weight of the 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, the method comprising step (a) of contacting the mixture with a membrane M2 to form a stream F3 comprising the 1,1,1,2,3,3-hexafluoropropane and a stream F4 comprising nitrogen, hydrogen and optionally oxygen, the 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 polyphenylene ether.

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