Process for the production and purification of trifluoroethylene and composition obtained from it

Abstract

The present invention relates to a process for producing trifluoroethylene in a reactor equipped with a fixed catalytic bed comprising a catalyst, said process comprising the steps of: a) reacting chlorotrifluoroethylene with hydrogen in the presence of the catalyst and in the gas phase to produce a product stream comprising trifluoroethylene; b) treating the product stream obtained in step a) to recover a stream A comprising trifluoroethylene (HFO-1123), chlorotrifluoroethylene (HCFO-1113) and at least one additional compound selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane; the total mass content of said at least one additional compound in said stream A being less than 0.5%;(c) Distillation of said stream A to recover a stream B comprising at least 99% by weight of trifluoroethylene and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane, based on the total weight of said stream B. The present invention also relates to a composition comprising at least 99% by weight of trifluoroethylene and 0.1 to 1000 ppm of ethane, and / or 0.1 to 1000 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a), based on the total weight of the composition.

Description

Title of the invention: Process for the production and purification of trifluoroethylene and composition obtained therefrom Technical field

[0001] The present invention relates to a process for producing hydrofluoroolefins. In particular, the present invention relates to a process for producing trifluoroethylene (HFO-1123 or VF3) by hydrogenolysis of chlorotrifluoroethylene. The present invention also relates to a composition comprising trifluoroethylene. Technological background of the invention

[0002] Fluorinated olefins, such as VF3, are known and are used as monomers or co-monomers for the manufacture of fluorocarbon polymers having remarkable characteristics, in particular excellent chemical resistance and good thermal resistance.

[0003] Trifluoroethylene is a gas under normal conditions of pressure and temperature. The main risks associated with the use of this product concern its flammability, its propensity for self-polymerization when not stabilized, its explosiveness due to its chemical instability and its supposed sensitivity to peroxidation, by analogy with other halogenated olefins. Trifluoroethylene has the particularity of being extremely flammable, with a lower explosive limit (LEL) of approximately 10% and an upper explosive limit (UEL) of approximately 30%. The major danger, however, is associated with the propensity of VF3 to decompose violently and explosively under certain pressure conditions in the presence of an energy source, even in the absence of oxygen.

[0004] Given the above main risks, the synthesis and storage of VF3 pose particular problems and impose strict safety rules throughout these processes. A known route for the preparation of trifluoroethylene uses chlorotrifluoroethylene (CTFE) and hydrogen as starting products in the presence of a catalyst and in the gas phase.

[0005] WO 2013 / 128102 discloses a process for producing trifluoroethylene by hydrogenolysis of CTFE in the gas phase and in the presence of a catalyst based on a group VIII metal at atmospheric pressure and at low temperatures.

[0006] EP 2 993 213 discloses a process for producing trifluoroethylene. This can be obtained by hydrogenolysis of chlorotrifluoroethylene or by thermal decomposition of chlorodifluoromethane and chlorofluoromethane. The production process involves the implementation of a distillation step at a pressure of 10 barg and from which the trifluoroethylene is recovered by side withdrawal. The implementation of high-pressure distillation requires the establishment of specific operating conditions given the explosive nature of trifluoroethylene above 3 bara.

[0007] There is therefore a need to provide a simpler and safer process for producing trifluoroethylene while maintaining high yields and selectivities. Summary of the invention

[0008] According to a first aspect, the present invention provides a process for producing trifluoroethylene in a reactor provided with a fixed catalytic bed comprising a catalyst, said process comprising the steps of: a. reacting chlorotrifluoroethylene with hydrogen in the presence of the catalyst and in the gas phase to produce a product stream comprising trifluoroethylene; b. treatment of the product stream obtained in step a) to recover a stream A comprising trifluoroethylene (HFO-1123), chlorotrifluoroethylene (HCFO-1113) and at least one additional compound selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) etethane; the total mass content of said at least one additional compound in said stream A being less than 0.5%; c. distilling said stream A to recover a stream B comprising at least 95% by weight of trifluoroethylene and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0009] The present invention makes it possible to implement a safe and efficient process for the production and purification of trifluoroethylene. The content of certain additional compounds is greatly limited while implementing a simplified process compared to the prior art. The present process also makes it possible to obtain a good yield of high-purity trifluoroethylene.

[0010] According to a preferred embodiment, step c) of distillation of said stream A is carried out at a pressure of less than 3 bara.

[0011] According to a preferred embodiment, step c) of distillation of said stream A is carried out in a distillation column comprising structured packing.

[0012] According to a preferred embodiment, said stream A comprises 1,1-difluoroethylene (HFO-1132a) and 1,1,1-trifluoroethane (HFC-143a), each in a mass content of less than 0.1% based on the total weight of said stream A.

[0013] According to a preferred embodiment, said stream A comprises 1,1,1,2-tetrafluoroethane (HFC-134a) in a mass content of less than 0.01% based on the total weight of said stream A.

[0014] According to a preferred embodiment, said stream A comprises ethane in a mass content of less than 0.05% based on the total weight of said stream A.

[0015] According to a preferred embodiment, said catalyst is a catalyst based on a metal from columns 8 to 10 of the periodic table of elements, preferably deposited on a support, in particular an aluminum-based support; more particularly the catalyst comprises palladium supported on alpha alumina.

[0016] According to a preferred embodiment, the chlorotrifluoroethylene and the hydrogen are in anhydrous form.

[0017] According to a second aspect, the present invention provides a composition comprising at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm of ethane, or - from 0.1 to 1000 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a); or - from 0.1 to 1000 ppm of ethane and from 0.1 to 1000 ppm of 1,1,1,2- tetrafluoroethane (HFC-134a) based on the total weight of the composition.

[0018] According to a preferred embodiment, the composition also comprises from 0.1 to 1000 ppm of 1,1,1-trifluoroethane (HFC-143a) based on the total weight of the composition.

[0019] According to a preferred embodiment, the composition also comprises from 0.1 to 2000 ppm of 1,1-difluoroethylene (HFO-1132a) based on the total weight of the composition.

[0020] The present invention provides a trifluoroethylene composition in which the content of additional compounds is limited. This provides numerous advantages in the fields of application of trifluoroethylene. Detailed description of the invention

[0021] The present invention relates to a process for producing trifluoroethylene comprising a step of hydrogenolysis reaction of chlorotrifluoroethylene (CTFE) with hydrogen in the gas phase and preferably in the presence of a catalyst.

[0022] According to a preferred embodiment, the method according to the invention described in the present application is implemented continuously.

[0023] According to a preferred embodiment, in the process described in the present application, the hydrogen is in anhydrous form.

[0024] According to a preferred embodiment, in the process described in the present application, the chlorotrifluoroethylene is in anhydrous form.

[0025] The implementation of the processes according to the invention in the presence of hydrogen and / or anhydrous chlorotrifluoroethylene makes it possible to effectively increase the lifetime of the catalyst and thus the overall productivity of the process. 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 compound considered. Catalyst

[0026] Preferably, the catalyst is based on a metal from columns 8 to 10 of the periodic table of elements. In particular, the catalyst is based on a metal selected from the group consisting of Pd, Pt, Rh, and Ru; preferably palladium.

[0027] Preferably, the catalyst is supported. The support is preferably selected from the group consisting of activated carbon, an aluminum-based support, calcium carbonate, and graphite. Preferably, the support is aluminum-based. In particular, the support is alumina. The alumina may be alpha alumina. Preferably, the alumina comprises at least 90% alpha alumina. It has been observed that the conversion of the hydrogenolysis reaction is improved when the alumina is an alpha alumina. Thus, the catalyst is more particularly palladium supported on alumina, advantageously palladium supported on an alumina comprising at least 90% alpha alumina, preferably palladium supported on an alpha alumina.

[0028] Preferably, the palladium represents from 0.01% to 5% by weight based on the total weight of the catalyst, preferably from 0.1% to 2% by weight based on the total weight of the catalyst.

[0029] In particular, said catalyst comprises from 0.01% to 5% by weight of palladium supported on alumina, preferably the alumina comprises at least 90% alpha alumina, more preferably the alumina is an alpha alumina. Catalyst activation

[0030] Said catalyst is preferably activated before its use in step a). Preferably, the activation of the catalyst is carried out at high temperature and in the presence of a reducing agent. According to a particular embodiment, the reducing agent is chosen from the group consisting of hydrogen, carbon monoxide, nitrogen monoxide, formaldehyde, C1-C6 alkanes and C1-C10 hydrohalocarbons, or a mixture thereof; preferably hydrogen or a C1-C10 hydrohalocarbon, or a mixture thereof; in particular hydrogen, chlorotrifluoroethylene, trifluoroethylene, chlorotrifluoroethane, trifluoroethane or difluoroethane or a mixture thereof. Preferably, the activation of the catalyst is carried out at a temperature between 100°C and 400°C, in particular at a temperature between 150°C and 350°C. In particular, the activation of the catalyst is carried out at a temperature between 100°C and 400°C, in particular at a temperature between 150°C and 350°C, in the presence of hydrogen as a reducing agent. Catalyst regeneration

[0031] Said catalyst used in the present process can be regenerated. This regeneration step can be carried out in a temperature range of the catalytic bed between 90°C and 450°C. Preferably, the regeneration step is carried out in the presence of hydrogen. The implementation of the regeneration step makes it possible to improve the yield of the reaction compared to the initial yield before regeneration.

[0032] According to a preferred embodiment, the regeneration step can be carried out at a temperature of the catalytic bed of 90°C to 300°C, preferably at a temperature of the catalytic bed of 90°C to 250°C, more preferably from 90°C to 200°C, in particular from 90°C to 175°C, more particularly at a temperature of the catalytic bed of 90°C to 150°C. In particular, the implementation of the regeneration step at a low temperature, for example from 90°C to 200°C or from 90°C to 175°C or from 90°C to 150°C allows the desorption of compounds harmful to the activity of the catalyst and / or to limit phase transitions modifying the structure of the catalyst.

[0033] According to another preferred embodiment, the regeneration step can be carried out at a temperature of the catalytic bed greater than 200°C, advantageously greater than 230°C, preferably greater than 250°C, in particular greater than 300°C. The regeneration step can be carried out periodically depending on the productivity or the conversion obtained in step a). The regeneration step may advantageously be carried out at a temperature of the catalytic bed of between 200°C and 300°C, preferably between 205°C and 295°C, more preferably between 210°C and 290°C, in particular between 215°C and 290°C, more particularly between 220°C and 285°C, preferably between 225°C and 280°C, more preferably between 230°C and 280°C. Alternatively, the regeneration step may be carried out at a temperature of between 300°C and 450°C, preferably between 300°C and 400°C.The regenerated catalyst can be reused in step a) of the present process. Hydrogenolysis reaction

[0034] The present invention comprises, as mentioned above, a step of hydrogenolysis reaction of chlorotrifluoroethylene (CTFE) with hydrogen to produce a stream comprising trifluoroethylene. The hydrogenolysis step is carried out in the presence of a catalyst and in the gas phase. Preferably, the hydrogenolysis step is carried out in the presence of a previously activated catalyst and in the gas phase. The hydrogenolysis step consists of simultaneously introducing hydrogen, CTFE and optionally an inert gas, such as nitrogen, into the gas phase and in the presence of said catalyst, preferably activated.

[0035] Preferably, said step a) is carried out at a fixed catalytic bed temperature of between 50°C and 250°C. Said step a) may be carried out at a fixed catalytic bed temperature of between 50°C and 240°C, advantageously between 50°C and 230°C, preferably between 50°C and 220°C, more preferably between 50°C and 210°C, in particular between 50°C and 200°C. Said step a) can also be carried out at a fixed catalytic bed temperature of between 60°C and 250°C, advantageously between 70°C and 250°C, preferably between 80°C and 250°C, more preferably between 90°C and 250°C, in particular between 100°C and 250°C, more particularly between 120°C and 250°C.Said step a) may also be carried out at a fixed catalytic bed temperature of between 60°C and 240°C, advantageously between 70°C and 230°C, preferably between 80°C and 220°C, more preferably between 90°C and 210°C, in particular between 100°C and 200°C, more particularly between 100°C and 180°C, preferably between 100°C and 160°C, particularly preferably between 120°C and 160°C.

[0036] The H2 / CTFE molar ratio is between 0.5 / 1 and 2 / 1 and preferably between 1 / 1 and 1.2 / 1. If an inert gas such as nitrogen is present in step a), the nitrogen / H2 molar ratio is between 0 / 1 and 2 / 1 and preferably between 0 / 1 and 1 / 1.

[0037] Step a) is preferably carried out at a pressure of 0.05 MPa to 1.1 MPa, more preferably of 0.05 MPa to 0.5 MPa, in particular at atmospheric pressure.

[0038] The contact time calculated as the ratio between the volume, in liters, of catalyst and the total flow rate of the gas mixture, in normal liters per second, at the inlet of the reactor, is between 1 and 60 seconds, preferably between 5 and 45 seconds, in particular between 10 and 30 seconds, more particularly between 15 and 25 seconds.

[0039] The hydrogenolysis step (step a)) of the present process results in the production of a product stream comprising trifluoroethylene. Said product stream may also comprise unreacted hydrogen and unreacted chlorotrifluoroethylene. Said product stream may also contain 1,1-difluoroethylene, 1,1,1,2-tetrafluoroethane, 1,1,1-trifluoroethane or ethane. Said product stream may also comprise HCl or HF or a mixture of both. Carrying out this step a) makes it possible to produce trifluoroethylene containing a reduced content of 1,1-difluoroethylene, 1,1,1,2-tetrafluoroethane, 1,1,1-trifluoroethane and / or ethane. This facilitates the reaction stream processing steps and results in better overall process efficiency. Reaction flow treatment

[0040] According to step b) of the present process, the product stream from step a) is treated to recover a stream A comprising trifluoroethylene (HFO-1123), chlorotrifluoroethylene (HCFO-1113) and at least one additional compound selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane. Said stream A may therefore comprise one, two, three or all four of the additional compounds mentioned above.

[0041] According to a preferred embodiment, the total mass content of said at least one additional compound in said stream A is less than 0.5%, advantageously less than 0.4%, preferably less than 0.3%, more preferably less than 0.2% based on the total weight of said stream A. Thus, all of the additional compounds present in said stream A represent a mass content of less than 0.5%, advantageously less than 0.4%, preferably less than 0.3%, more preferably less than 0.2% based on the total weight of said stream A.

[0042] According to a preferred embodiment, said stream A comprises 1,1,1,2-tetrafluoroethane (HFC-134a) in a mass content of less than 0.05%, advantageously less than 0.025%, preferably less than 0.01%, based on the total weight of said stream A.

[0043] According to a preferred embodiment, said stream A comprises ethane in a mass content of less than 0.1%, preferably less than 0.05%, in particular less than 0.025% based on the total weight of said stream A.

[0044] According to a preferred embodiment, said stream A comprises 1,1-difluoroethylene (HFO-1132a) in a mass content of less than 0.2%, advantageously less than 0.15%, preferably less than 0.1%, in particular less than 0.08%, more particularly less than 0.075% based on the total weight of said stream A.

[0045] According to a preferred embodiment, said stream A comprises 1,1,1-trifluoroethane in a mass content of less than 0.2%, advantageously less than 0.15%, preferably less than 0.1% based on the total weight of said stream A.

[0046] According to a preferred embodiment, said stream A comprises 1,1-difluoroethylene (HFO-1132a) and 1,1,1-trifluoroethane (HFC-143a), each in a mass content of less than 0.2%, preferably less than 0.1% based on the total weight of said stream A.

[0047] According to a preferred embodiment, said stream A comprises 1,1-difluoroethylene (HFO-1132a) and 1,1,1-trifluoroethane (HFC-143a), each in a mass content of less than 0.2%, preferably less than 0.1% based on the total weight of said stream A; and said stream A comprises ethane in a mass content of less than 0.1%, preferably less than 0.05% based on the total weight of said stream A.

[0048] According to a preferred embodiment, said stream A comprises 1,1-difluoroethylene (HFO-1132a) and 1,1,1-trifluoroethane (HFC-143a), each in a mass content of less than 0.2%, preferably less than 0.1% based on the total weight of said stream A; and said stream A comprises 1,1,1,2-tetrafluoroethane (HFC-134a) in a mass content of less than 0.05%, advantageously less than 0.025%, preferably less than 0.01%, based on the total weight of said stream A.

[0049] According to a preferred embodiment, said stream A comprises 1,1-difluoroethylene (HFO-1132a) and 1,1,1-trifluoroethane (HFC-143a), each in a mass content of less than 0.2%, preferably less than 0.1% based on the total weight of said stream A; and said stream A comprises 1,1,1,2-tetrafluoroethane (HFC-134a) in a mass content of less than 0.05%, advantageously less than 0.025%, preferably less than 0.01%, based on the total weight of said stream A; and said stream A comprises ethane in a mass content of less than 0.1%, preferably less than 0.05% based on the total weight of said stream A.

[0050] According to a preferred embodiment, in said stream A, the mass content of trifluoroethylene is greater than 10%, advantageously greater than 15%, preferably greater than 20%, in particular greater than 25%, more particularly greater than 30% based on the total weight of said stream A.

[0051] According to a preferred embodiment, in said stream A, the mass content of chlorotrifluoroethylene is less than 70%, advantageously less than 65%, preferably less than 60%, in particular less than 55% based on the total weight of said stream A. Preferably, in said stream A, the mass content of chlorotrifluoroethylene is greater than 1%, preferably greater than 5% based on the total weight of said stream A.

[0052] Thus, said stream A may comprise trifluoroethylene (HFO-1123), chlorotrifluoroethylene (HCFO-1113), 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane in any of the mass contents expressed above.

[0053] Thus, according to a particular embodiment, said stream A comprises: - trifluoroethylene in a mass content greater than 10%, advantageously greater than 15%, preferably greater than 20%, in particular greater than 25%, more particularly greater than 30% based on the total weight of said stream A; - chlorotrifluoroethylene in a mass content of less than 70%, advantageously less than 65%, preferably less than 60%, in in particular less than 55% based on the total weight of said stream A, and optionally greater than 1%, preferably greater than 5% based on the total weight of said stream A; - 1,1,1,2-tetrafluoroethane (HFC-134a) in a mass content of less than 0.05%, advantageously less than 0.025%, preferably less than 0.01% based on the total weight of said stream A; - ethane in a mass content of less than 0.1%, preferably less than 0.05% based on the total weight of said stream A; - 1,1-difluoroethylene (HFO-1132a) in a mass content of less than 0.2%, advantageously less than 0.15%, preferably less than 0.1%, in particular less than 0.08% based on the total weight of said stream A; and - 1,1,1-trifluoroethane in a mass content of less than 0.2%, advantageously less than 0.15%, preferably less than 0.1% based on the total weight of said stream A;

[0054] and the total mass content of 1,1,1,2-tetrafluoroethane, ethane, 1,1-difluoroethylene and 1,1,1-trifluoroethane in said stream A is less than 0.5%, advantageously less than 0.4%, preferably less than 0.3%, more preferably less than 0.2% based on the total weight of said stream A.

[0055] When one of said additional compounds selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane is present in said stream A, it (or these) is (are) present in a mass content greater than 0.01 ppm, preferably greater than 0.1 ppm based on the total weight of said stream A.

[0056] According to a particular embodiment, the processing step b) of the present method may comprise the steps of: i. Removal of HF and / or HCl from said product stream obtained in step a) to form a gas mixture; ii. Drying of the gas mixture from step i); iii. Treatment of the dried gas mixture in step ii) to remove hydrogen and optionally inert gases and form said stream A.

[0057] Preferably, said stream A is gaseous.

[0058] The paragraph below details steps i) to iii).

[0059] The product stream from step a) is recovered at the reactor outlet in gaseous form. Preferably, at the outlet of the hydrogenolysis reactor, the product stream is first treated to remove HCl and HF. The product stream is passed through water in a washing column and then washed with a dilute base such as NaOH or KOH. The remainder of the gas mixture, consisting of the unconverted reactants (H2 and CTFE), dilution nitrogen (if present), trifluoroethylene and additional compounds mentioned above is directed to a dryer in order to remove traces of wash water. Drying can be carried out using products such as sodium or magnesium calcium sulfate, calcium chloride, potassium carbonate, silica gel (silica gel) or zeolites. In one embodiment, a molecular sieve (zeolite) such as siliporite is used for drying. The gas mixture thus dried is subjected to a step of separating the hydrogen and the inerts from the rest of the other products present in the gas mixture by absorption / desorption in the presence of an alcohol containing 1 to 4 carbon atoms and preferably ethanol, at atmospheric pressure and at a temperature below room temperature, preferably below 10°C and even more preferably at a temperature of -25°C, for absorption.In one embodiment, the absorption of the organics is carried out in a countercurrent column with ethanol cooled to -25°C. The ethanol flow rate is adjusted according to the flow rate of organics to be absorbed. Hydrogen and inert gases, insoluble in ethanol at this temperature, are eliminated at the top of the absorption column. The organics are then recovered in the form of said stream A, by heating the ethanol to its boiling point (desorption), to then be distilled.

[0060] Steps a) and b) of the present process thus make it possible to limit the content of the additional compound(s) in stream A, which facilitates the implementation of step c) described below (in particular by implementing this step at low pressure).

[0061] According to step c), said stream A thus obtained is distilled to form and recover a stream B comprising trifluoroethylene and one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane. Said stream B may comprise one, two, three or all four of the additional compounds mentioned above.

[0062] According to a preferred embodiment, step c) of distillation of said stream A is carried out at a pressure of less than 3 bara, preferably at a pressure of between 0.5 and 3 bara, in particular at a pressure of between 0.9 and 2 bara. Carrying out distillation at a pressure of less than 3 bara makes it possible to make the process safe given the explosive nature of trifluoroethylene above 3 bara.

[0063] Preferably, step c) of distillation of said stream A is carried out in a distillation column comprising a structured packing. It has been observed that a structured packing makes it possible to obtain a more efficient distillation step c). Said structured packing may be made of a metallic material.

[0064] Said stream B is preferably recovered at the top of the distillation column. Before being recovered, stream B may optionally be partially condensed at the top of the distillation column. When partial condensation is carried out, stream B is brought to a temperature of -50°C to -70°C. The temperature is adjusted according to the pressure applied in step c). Partial condensation makes it possible to improve the efficiency of the distillation by limiting the content of additional compounds in stream B.

[0065] The distillation of said stream A also results in the formation of a stream C comprising chlorotrifluoroethylene, preferably recovered at the bottom of the distillation column. Said stream C can be recycled to step a) after a possible purification treatment.

[0066] Said stream B may comprise at least 95% of trifluoroethylene, advantageously at least 96%, preferably at least 97%, in particular at least 98%, more particularly at least 99% by weight based on the total weight of said stream B.

[0067] Preferably, said stream B also comprises less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0068] Thus, said stream B may comprise at least 95% by weight of trifluoroethylene; and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0069] Advantageously, said stream B may comprise at least 96% by weight of trifluoroethylene; and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0070] Preferably, said stream B may comprise at least 97% by weight of trifluoroethylene; and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0071] More preferably, said stream B may comprise at least 98% by weight of trifluoroethylene; and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO- 1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0072] In particular, said stream B may comprise at least 99% by weight of trifluoroethylene; and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B.

[0073] Preferably, said stream B comprises ethane in a mass content of less than 500 ppm, more preferably less than 200 ppm, in particular less than 100 ppm, more particularly less than 50 ppm, preferably less than 10 ppm based on the total weight of said stream B.

[0074] Preferably, said stream B comprises 1,1,1,2-tetrafluoroethane in a mass content of less than 500 ppm, more preferably less than 200 ppm, in particular less than 100 ppm, more particularly less than 50 ppm, preferably less than 10 ppm based on the total weight of said stream B. Said stream B may also be free of 1,1,1,2-tetrafluoroethane.

[0075] Preferably, said stream B comprises 1,1,1-trifluoroethane in a mass content of less than 1000 ppm, more preferably less than 750 ppm, in particular less than 500 ppm, more particularly less than 250 ppm based on the total weight of said stream B.

[0076] Preferably, said stream B comprises 1,1-difluoroethylene in a mass content of less than 2000 ppm, more preferably less than 1500 ppm, in particular less than 1000 ppm based on the total weight of said stream B.

[0077] When one of said additional compounds selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane is present in said stream B, it (or these) is (are) present in a mass content greater than 0.01 ppm, preferably greater than 0.1 ppm based on the total weight of said stream B. Composition

[0078] According to a second aspect, the present invention provides high purity trifluoroethylene compositions.

[0079] Said composition comprises at least 99% by weight of trifluoroethylene and from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane based on the total weight of the composition.

[0080] Said composition may also comprise at least 99% by weight of trifluoroethylene and from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a) based on the total weight of the composition.

[0081] Said composition may also comprise at least 99% by weight of trifluoroethylene and: - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane; and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a) based on the total weight of the composition.

[0082] According to a preferred embodiment, any of the above compositions also comprises from 0.1 to 1000 ppm, preferably from 0.1 to 750 ppm, in particular from 0.1 to 500 ppm, more preferably from 0.1 to 250 ppm of 1,1,1-trifluoroethane (HFC-143a) based on the total weight of the composition.

[0083] According to a preferred embodiment, any of the above compositions also comprises from 0.1 to 2000 ppm, preferably from 0.1 to 1500 ppm, in particular from 0.1 to 1000 ppm of 1,1-difluoroethylene (HFO-1132a) based on the total weight of the composition.

[0084] Said composition may comprise at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane, - from 0.1 to 1000 ppm, preferably from 0.1 to 750 ppm, in particular from 0.1 to 500 ppm, more preferably from 0.1 to 250 ppm of 1,1,1-trifluoroethane (HFC-143a); based on the total weight of the composition.

[0085] Said composition may comprise at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a), - from 0.1 to 1000 ppm, preferably from 0.1 to 750 ppm, in particular from 0.1 to 500 ppm, more preferably from 0.1 to 250 ppm of 1,1,1-trifluoroethane (HFC-143a); based on the total weight of the composition.

[0086] Said composition may comprise at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane, - from 0.1 to 2000 ppm, preferably from 0.1 to 1500 ppm, in particular from 0.1 to 1000 ppm of 1,1-difluoroethylene (HFO-1132a); based on the total weight of the composition.

[0087] Said composition may comprise at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a), - from 0.1 to 2000 ppm, preferably from 0.1 to 1500 ppm, in particular from 0.1 to 1000 ppm of 1,1-difluoroethylene (HFO-1132a); based on the total weight of the composition.

[0088] Thus, according to a preferred embodiment, said composition comprises at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane, - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a), - from 0.1 to 1000 ppm, preferably from 0.1 to 750 ppm, in particular from 0.1 to 500 ppm, more preferably from 0.1 to 250 ppm of 1,1,1-trifluoroethane (HFC-143a); based on the total weight of the composition.

[0089] Thus, according to another preferred embodiment, said composition comprises at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane, - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a), - from 0.1 to 2000 ppm, preferably from 0.1 to 1500 ppm, in particular from 0.1 to 1000 ppm of 1,1-difluoroethylene (HFO-1132a); based on the total weight of the composition.

[0090] According to another particular embodiment, said composition comprises at least 99% by weight of trifluoroethylene and - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of ethane, - from 0.1 to 1000 ppm, advantageously from 0.1 to 500 ppm, preferably from 0.1 to 200 ppm, more preferably from 0.1 to 100 ppm, in particular from 0.1 to 50 ppm, more particularly from 0.1 to 10 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a), - from 0.1 to 1000 ppm, preferably from 0.1 to 750 ppm, in particular from 0.1 to 500 ppm, more preferably from 0.1 to 250 ppm of 1,1,1-trifluoroethane (HFC-143a); - from 0.1 to 2000 ppm, preferably from 0.1 to 1500 ppm, in particular from 0.1 to 1000 ppm of 1,1-difluoroethylene (HFO-1132a); based on the total weight of the composition.

[0091] The above-mentioned compositions can be obtained by the process according to the present invention. Examples

[0092] In a tubular reactor consisting of a stainless steel tube with a length of 1200 mm and a diameter of 25 mm, and equipped with a double jacket, 25 cm3 of catalyst (0.2% palladium supported on alpha alumina) were introduced. The catalyst thus loaded was then activated in the following manner: the reaction tube was placed in a tubular furnace and was supplied with a flow of hydrogen (from 0.05 to 0.1 moles per gram of catalyst). The catalytic bed was then heated to a temperature of 200°C to 250°C with a temperature gradient of 0.2°C / min. After this activation period, the tube was cooled to room temperature and then isolated for installation on a hydrogenolysis test bench. The reactor was supplied with 1 mol / h of CTFE and 1 mol / h of hydrogen in anhydrous form. It is also possible to feed the reactors with an inert gas (here nitrogen). The temperature of the catalytic bed was between 100°C and 130°C.The contact time, calculated as the ratio of the volume in liters of catalyst to the sum of the flow rates of the reactants in normal liters per second, was of the order of 22 seconds.

[0093] The gases resulting from the reaction are introduced into a hydroacid removal column consisting of a fluoropolymer tube 355 mm long and 40 mm in diameter and lined with fluoropolymer rings 4 mm in diameter and 5 mm long. The removal column is continuously supplied with water at a flow rate of 101 / h. The water loaded with hydroacid is continuously removed from the bottom of the removal column. The reaction products thus freed from hydroacids are then directed to a drying section consisting of two stainless steel metal tubes with a 800 mm long and 50 mm in diameter, mounted in series, and filled with molecular sieve of the siliporite 3A type. The gases thus dried are then directed towards an absorption column consisting of a stainless steel metal tube 700 mm long and 40 mm in diameter, equipped with a double jacket and packed with glass rings 4.3 mm in diameter and 4.5 mm long. The absorption column is fed at the top with ethanol via a pump with a flow rate of 8 liters / hour. The double jacket of the absorption column is fed with a heat transfer fluid at -25°C.Hydrogen and inerts exit at the top of the absorption column while the reaction products, dissolved in ethanol, exit at the bottom of the column and are directed towards a desorption section consisting of a glass column 250 mm long and 18 mm in diameter, packed with glass rings 4.3 mm in diameter and 4.5 mm long and a 1 liter glass flask where the ethanol is brought to the boil using a heating mantle. The organic products from the reaction are evaporated and leave the desorption section through the column head while the ethanol freed from organics is taken up by the pump to be fed to the top of the absorption column.

[0094] The mixture of organic products from the desorption section is then directed to a distillation column comprising a Sulzer EX or Sulzer DX structured packing. The rectification section is equivalent to 12 to 13 theoretical stages and the stripping section is equivalent to 1 theoretical stage. Stream A entering the distillation column comprises between 35 and 40% trifluoroethylene, 45% to 55% chlorotrifluoroethylene, 0.01 to 0.02% ethane, 0.05 to 0.1% 1,1-difluoroethylene, 0.05 to 0.1% 1,1,1-trifluoroethane and 0.005 to 0.01% 1,1,1,2-tetrafluoroethane. This distillation step is carried out at a pressure of between 0.8 and 1.2 bara. Stream B is recovered at the top of the distillation column. Stream B consists of 99.5% trifluoroethylene, 0.1% 1,1-difluoroethylene (HFO-1132a), 0.02% 1,1,1-trifluoroethane (HFC-143a) and 0.0002% ethane and less than 1 ppm 1,1,1,2-tetrafluoroethane (HFC-134a).

Claims

Claims

1. A process for producing trifluoroethylene in a reactor provided with a fixed catalytic bed comprising a catalyst, said process comprising the steps of: a. reacting chlorotrifluoroethylene with hydrogen in the presence of the catalyst and in the gas phase to produce a product stream comprising trifluoroethylene; b. treating the product stream obtained in step a) to recover a stream A comprising trifluoroethylene (HFO-1123), chlorotrifluoroethylene (HCFO-1113) and at least one additional compound selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane; the total mass content of said at least one additional compound in said stream A being less than 0.5%; c.distillation of said stream A to recover a stream B comprising at least 95% by weight of trifluoroethylene and less than 0.2% by weight of one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a) and ethane based on the total weight of said stream B; characterized in that the chlorotrifluoroethylene and the hydrogen are in anhydrous form; and in that step c) of distillation of said stream A is carried out in a distillation column comprising structured packing.

2. Process according to claim 1 characterized in that step c) of distillation of said stream A is carried out at a pressure of less than 3 bara.

3. Method according to any one of the preceding claims, characterized in that step c) of distillation of said stream A is carried out in a distillation column comprising a structured packing made of a metallic material.

4. Method according to any one of the preceding claims characterized in that said stream A comprises 1,1- difluoroethylene (HFO-1132a) and 1,1,1-trifluoroethane (HFC-143a), each in a mass content of less than 0.1% based on the total weight of said stream A.

5. Process according to any one of the preceding claims, characterized in that said stream A comprises 1,1,1,2-tetrafluoroethane (HFC-134a) in a mass content of less than 0.01% based on the total weight of said stream A.

6. Process according to any one of the preceding claims, characterized in that said stream A comprises ethane in a mass content of less than 0.05% based on the total weight of said stream A.

7. Method according to any one of the preceding claims, characterized in that said catalyst is a catalyst based on a metal from columns 8 to 10 of the periodic table of elements, preferably deposited on a support, in particular an aluminum-based support; more particularly the catalyst comprises palladium supported on alpha alumina.

8. A composition comprising at least 99% by weight of trifluoroethylene, from 0.1 to 2000 ppm of 1,1-difluoroethylene (HFO-1132a) and - from 0.1 to 1000 ppm of ethane, or - from 0.1 to 1000 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a); or - from 0.1 to 1000 ppm of ethane and from 0.1 to 1000 ppm of 1,1,1,2-tetrafluoroethane (HFC-134a) based on the total weight of the composition.

9. Composition according to the preceding claim, characterized in that it also comprises from 0.1 to 1000 ppm of 1,1,1-trifluoroethane (HFC-143a) based on the total weight of the composition.