Method for producing trifluoroethylene

Abstract

The invention relates to a process for producing trifluoroethylene in a reactor equipped with a fixed catalytic bed comprising a catalyst, said process comprising the step a) of reacting a composition A comprising chlorotrifluoroethylene with hydrogen in the gas phase in the presence of a catalyst to produce a stream B comprising trifluoroethylene. The invention is characterised in that the composition A further comprises at least one of an additional compound C1 selected from the group consisting of 1, 1, 1-trifluoroethane, 1, 1, 1, 2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1, 1, 1-trifluoroethane and 1, 2-dichlorohexafluorocyclobutane. The invention also relates to a chlorotrifluoroethylene composition.

Description

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 VF 3 The present invention also relates to a composition comprising chlorotrifluoroethylene. Background Art

[0002] Fluoroolefins, such as VF 3 , are known and are used as monomers or comonomers for the manufacture of fluorocarbon polymers which exhibit noteworthy properties, in particular excellent chemical resistance and good thermal resistance.

[0003] Trifluoroethylene is a gas under standard conditions of pressure and temperature. Similar to other halogenated olefins, the main risks associated with the use of this product are related to its flammability, its tendency to self-polymerize when it is unstable, its explosiveness due to its chemical instability, and its expected sensitivity to peroxidation. Trifluoroethylene exhibits the remarkable characteristic of being extremely flammable, with a lower explosion limit (LEL) of about 10% and an upper explosion limit (UEL) of about 30%. However, the main danger is that VF 3 The tendency to decompose violently and explosively in the presence of an energy source, even in the absence of oxygen, and under certain pressure conditions.

[0004] In view of the above major risks, VF 3 The synthesis and storage of trifluoroethylene pose particular problems and strict safety regulations are imposed throughout these processes. A known route for preparing trifluoroethylene uses chlorotrifluoroethylene (CTFE) and hydrogen as starting materials in the presence of a catalyst and in the gas phase.

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

[0006] A process for producing trifluoroethylene is known from EP 2 993 213. This can be obtained by hydrogenolysis of chlorotrifluoroethylene or by thermal decomposition of chlorodifluoromethane and chlorofluoromethane. The production process involves a distillation step at a pressure of 10 barg, from which the trifluoroethylene is recovered by side stream extraction. The high-pressure distillation requires the installation of special operating conditions due to the explosive properties of trifluoroethylene above 3 bara.

[0007] It is therefore desirable to provide a simpler and safer process for producing trifluoroethylene while maintaining high yield and selectivity. Summary of the invention

[0008] According to a first aspect, the present invention provides a process for producing trifluoroethylene in a reactor equipped with a fixed catalytic bed comprising a catalyst, the process comprising step a): reacting a composition A comprising chlorotrifluoroethylene with hydrogen in the presence of a catalyst and in the gas phase to produce a stream B comprising trifluoroethylene, characterized in that the composition A also comprises at least one of the additional compounds C1 selected from 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1,1,1-trifluoroethane and 1,2-dichlorohexafluorocyclobutane.

[0009] Surprisingly, it was observed that in the presence of the additional compound C1, the trifluoroethylene productivity increased. The presence of these compounds in small amounts, in addition to chlorotrifluoroethylene, makes it possible to improve the process for producing trifluoroethylene. The present invention demonstrates that, in order to achieve high productivity, it is not necessary to have highly pure chlorotrifluoroethylene. This makes it possible to simplify the production process and limit its overall costs.

[0010] According to a preferred embodiment, the total weight content of the at least one additional compound C1 is less than 15%, based on the total weight of the composition A, preferably less than 10%, in particular less than 5%, based on the total weight of the composition A.

[0011] According to a preferred embodiment, the composition A comprises at least 80% by weight of chlorotrifluoroethylene, based on the total weight of the composition A, preferably at least 95% by weight of chlorotrifluoroethylene, based on the total weight of the composition A, in particular at least 90% by weight of chlorotrifluoroethylene, based on the total weight of the composition A.

[0012] According to a preferred embodiment, the composition A further comprises trifluoroethylene, preferably further comprises trifluoroethylene in a weight content of less than 5% based on the total weight of the composition A.

[0013] According to a preferred embodiment, the composition A further comprises at least one additional compound C2 selected from 1,1,2-trifluoroethane, 1-chloro-1,1,2-trifluoroethane, 1-chloro-2,2-difluoroethylene, E / Z-1-chloro-1,2-difluoroethylene and 1-chloro-1,2,2-trifluoroethane.

[0014] According to a preferred embodiment, the weight content of the at least one additional compound C2, based on the total weight of the composition A, is less than 5%.

[0015] In a preferred embodiment, the catalyst comprises palladium supported on alpha-alumina.

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

[0017] According to a preferred embodiment, the process comprises a step i') of activating the catalyst before step a) by contacting the catalyst with a gas stream comprising a reducing agent, an inert gas or a mixture thereof.

[0018] According to a preferred embodiment, during said step i'):

[0019] - the temperature of the catalyst bed is increased from temperature T1 to temperature T2 which is higher than T1, wherein the temperature gradient is less than 0.5°C / min; or

[0020] - The temperature of the catalytic bed is increased incrementally from a temperature T1 to a temperature T2 which is higher than T1.

[0021] According to a second aspect, the present invention provides a composition comprising at least 80 weight percent of chlorotrifluoroethylene and at least one additional compound selected from 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1,1,1-trifluoroethane and 1,2-dichlorohexafluorocyclobutane; the total weight content of the at least one additional compound being less than 15% based on the total weight of the composition. DETAILED DESCRIPTION

[0022] The present invention relates to a process for producing trifluoroethylene, which comprises the step of subjecting chlorotrifluoroethylene (CTFE) to hydrogenolysis with hydrogen in the gas phase, preferably in the presence of a catalyst.

[0023] According to a preferred embodiment, the process according to the invention described in this patent application is performed continuously.

[0024] According to a preferred embodiment, in the process described in this patent application, the hydrogen is in anhydrous form.

[0025] According to a preferred embodiment, in the process described in this patent application, chlorotrifluoroethylene is in anhydrous form.

[0026] Carrying out the process according to the invention in the presence of anhydrous hydrogen and / or chlorotrifluoroethylene makes it possible to effectively increase the lifetime of the catalyst and thus the overall productivity of the process. The term anhydrous means a weight 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 compounds under consideration.

[0027] catalyst

[0028] Preferably, the catalyst is based on a metal from columns 8 to 10 of the Periodic Table of the Elements. In particular, the catalyst is based on a metal selected from Pd, Pt, Rh and Ru; preferably palladium.

[0029] Preferably, the catalyst is supported. The support is preferably selected from activated carbon, an aluminum-based (aluminum-based) support, calcium carbonate and graphite. Preferably, the support is based on aluminum. In particular, the support is aluminum oxide. The aluminum oxide may be alpha-aluminum oxide. Preferably, the aluminum oxide contains at least 90% alpha-aluminum oxide. It is observed that when the aluminum oxide is alpha-aluminum oxide, the conversion rate of the hydrogenolysis reaction is improved. Therefore, the catalyst is more particularly palladium supported on aluminum oxide, advantageously palladium supported on aluminum oxide containing at least 90% alpha-aluminum oxide, preferably palladium supported on alpha-aluminum oxide.

[0030] Preferably, palladium represents 0.01 to 5% by weight, based on the total weight of the catalyst, preferably 0.1 to 2% by weight, based on the total weight of the catalyst.

[0031] In particular, the catalyst comprises 0.01 to 5 wt% palladium supported on alumina; preferably, the alumina comprises at least 90% alpha-alumina; more preferably, the alumina is alpha-alumina.

[0032] Catalyst activation

[0033] The catalyst is preferably activated before its use in step a). Preferably, the activation of the catalyst is carried out at elevated temperature and in the presence of a reducing agent, an inert gas or a mixture thereof.

[0034] According to a particular embodiment, the reducing agent is selected from hydrogen, carbon monoxide, nitrogen monoxide, formaldehyde, C 1 -C 6 Alkanes and C 1 -C 10 Halogenated hydrocarbons, or mixtures thereof; preferably hydrogen or C 1 -C 10 Halogenated hydrocarbons, or mixtures thereof; in particular hydrogen, chlorotrifluoroethylene, trifluoroethylene, chlorotrifluoroethane, trifluoroethane or difluoroethane, or mixtures thereof.

[0035] The inert gas may be nitrogen or argon, preferably nitrogen.

[0036] Preferably, the activation of the catalyst is carried out at a temperature between 100° C. and 400° C., in particular between 150° C. and 350° C. In particular, the activation of the catalyst is carried out in the presence of hydrogen as a reducing agent at a temperature between 100° C. and 400° C., in particular between 150° C. and 350° C.

[0037] Preferably, during step i'), the temperature of the catalytic bed is increased from temperature T1 to temperature T2. In particular, during said step i'), the temperature of the catalytic bed is increased from temperature T1 to temperature T2 greater than T1, wherein the temperature gradient is less than 0.5°C / min. The applied temperature gradient makes it possible to prevent premature degradation of the catalyst and thereby enable a better yield or a better productivity of the hydrogenolysis reaction to be achieved. In particular, the temperature is increased with a temperature gradient of less than 0.45°C / min, or less than 0.40°C / min, or less than 0.35°C / min, or less than 0.30°C / min, or less than 0.25°C / min, or less than 0.20°C / min, or less than 0.15°C / min, or less than 0.10°C / min, or less than 0.05°C / min. Temperature T1 is the initial temperature of the activation step. This temperature T1 may be ambient temperature. Alternatively, the temperature T1 may be between 0°C and 150°C, advantageously between 0°C and 120°C, preferably between 0°C and 100°C, more preferably between 10°C and 100°C, in particular between 20°C and 100°C, more particularly between 20°C and 75°C, well between 20°C and 50°C. The temperature T2 represents the temperature to be reached during the activation phase. The temperature T2 is advantageously between 150°C and 400°C, preferably between 155°C and 375°C, more preferably between 160°C and 350°C, in particular between 165°C and 325°C, more particularly between 170°C and 320°C, well between 175°C and 310°C, and more well between 180°C and 300°C. According to a preferred embodiment, the temperature T2 is advantageously between 185°C and 290°C, preferably between 190°C and 280°C, more preferably between 195°C and 270°C, and in particular between 200°C and 260°C. The temperature T2 can be maintained for 5 min to 200 h, preferably 10 min to 100 h, in particular 15 min to 75 h, more particularly 30 min to 50 h, and well 1 h to 25 h. The temperature T2 can be maintained for 5 min to 24 h, preferably 10 min to 20 h, in particular 15 min to 15 h, more particularly 30 min to 10 h, and well 1 h to 10 h.

[0038] The gas stream used during step i') preferably does not contain oxygen. Preferably, step i') can be carried out with an amount of reducing agent greater than 0.01 mol per gram of catalyst, preferably greater than 0.05 per gram of catalyst. In particular, step i') can be carried out with an amount of reducing agent between 0.01 and 10 mol per gram of catalyst, preferably between 0.05 and 5 mol per gram of catalyst.

[0039] According to another embodiment, during the step i'), the temperature of the catalytic bed is increased from temperature T1 to temperature T2 in increments. Activating the catalyst in increments can improve the performance of the catalyst. Implementing the increments makes it possible to prevent the degradation of the catalyst. It is also observed that if the temperature increase between the increments is gradual and relatively slow compared to the usual conditions for activating the catalyst, the properties of the catalyst are additionally further improved. Therefore, preferably, in step i'), between two increments, the temperature is increased with a temperature gradient of less than 0.5°C / min. The temperature gradient applied between the two increments makes it possible to prevent premature degradation of the catalyst, and thus enable a better yield or better productivity of the hydrogenolysis reaction to be achieved. In particular, the temperature is increased with a temperature gradient of less than 0.45°C / min, or less than 0.40°C / min, or less than 0.35°C / min, or less than 0.30°C / min, or less than 0.25°C / min, or less than 0.20°C / min, or less than 0.15°C / min, or less than 0.10°C / min, or less than 0.05°C / min. Temperature T1 is the initial temperature of the activation step. This temperature T1 may be ambient temperature. Alternatively, temperature T1 may be between 0°C and 150°C, advantageously between 0°C and 120°C, preferably between 0°C and 100°C, more preferably between 10°C and 100°C, particularly between 20°C and 100°C, more particularly between 20°C and 75°C, and well between 20°C and 50°C. Temperature T2 represents the temperature to be reached during the activation phase. Temperature T2 is advantageously between 150°C and 400°C, preferably between 155°C and 375°C, more preferably between 160°C and 350°C, particularly between 165°C and 325°C, more particularly between 170°C and 320°C, well between 175°C and 310°C, and more well between 180°C and 300°C. According to a preferred embodiment, the temperature T2 is advantageously between 185°C and 290°C, preferably between 190°C and 280°C, more preferably between 195°C and 270°C, in particular between 200°C and 260°C. The temperature T2 can be maintained for 5 min to 200 h, preferably 10 min to 100 h, in particular 15 min to 75 h, more particularly 30 min to 50 h, well 1 h to 25 h. The temperature T2 can be maintained for 5 min to 24 h, preferably 10 min to 20 h, in particular 15 min to 15 h, more particularly 30 min to 10 h, well 1 h to 10 h. The step i') of activating the catalyst contains at least one increment between the temperature T1 and the temperature T2. The step i') of activating the catalyst may comprise a plurality of increments between the temperature T1 and the temperature T2. Preferably, step i') comprises at least one increment at a temperature T1a between 90 and 120°C. The presence of an increment between 90°C and 120°C should be beneficial in increasing the life of the catalyst.Step i') may also include one or more increments between temperature T1 and T1a and / or between temperature T1a and T2. Preferably, each increment between temperature T1 and temperature T2 may last between 5 min and 200 h, preferably between 10 min and 100 h, in particular between 15 min and 75 h, more particularly between 30 min and 50 h. In particular, each increment between temperature T1 and temperature T2 may last between 5 min and 24 h, preferably between 10 min and 20 h, in particular between 15 min and 15 h, more particularly between 30 min and 10 h. In particular, the increment at temperature T1a may last between 5 min and 200 h, preferably between 10 min and 100 h, in particular between 15 min and 75 h, more particularly between 30 min and 50 h. Advantageously, the increase at temperature T1a may last between 5 min and 24 h, preferably between 10 min and 20 h, in particular between 15 min and 15 h, more particularly between 30 min and 10 h.

[0040] The gas stream used during step i') may vary over time. For example, the gas stream may comprise an inert gas between two increments and, for example, a reducing agent between two other increments. In particular, when step i') is carried out between temperatures T1 and T1a, the gas stream comprises an inert gas and when step i') is carried out between temperatures T1a and T2, the gas stream comprises a reducing agent, preferably hydrogen or C as defined above. 1 -C 10 Thus, the gas stream used during step i') is changed during the increment carried out at temperature T1a. Alternatively, the gas stream may contain a reducing agent such as hydrogen or C as defined above during the entire step i'). 1 -C 10 It has been observed that during the temperature rise between the incremental temperature T1a and the temperature T2, the use of a reducing agent such as hydrogen or C as defined above 1 -C 10 Halogenated hydrocarbons, optionally mixed with an inert gas such as nitrogen, represent additional advantages in terms of productivity. As mentioned above, the temperature T2 is maintained for a certain period of time. During this increment at temperature T2, the gas stream can be changed. Thus, during the increment at temperature T2, the gas stream can contain hydrogen or C as defined above. 1 -C 10halogenated hydrocarbons; in particular, during the increment at temperature T2, the gas stream may contain hydrogen, chlorotrifluoroethylene, trifluoroethane, trifluoroethylene, chlorotrifluoroethane or difluoroethane. Preferably, step i') can be carried out in an amount of reducing agent greater than 0.01 per gram of catalyst, preferably greater than 0.05 per gram of catalyst. In particular, step i') can be carried out in an amount of reducing agent between 0.01 and 10 mol per gram of catalyst, preferably between 0.05 and 5 mol per gram of catalyst.

[0041] According to another embodiment, the step i') of activating the catalyst comprises contacting the catalyst with a gas stream comprising chlorotrifluoroethylene and optionally hydrogen. It has been observed that chlorotrifluoroethylene (CTFE) makes it possible to activate the catalyst, in particular when only hydrogen is present. This makes it possible to improve the process for producing trifluoroethylene. Activation in the presence of CTFE makes it possible to activate the catalyst at a lower temperature and thus provide a process with lower energy consumption. Since the reducing agent during activation is also one of the reactants for the subsequent reaction, the process is further simplified. Preferably, in this embodiment, step i') is carried out at a temperature T2' of less than 100°C. The temperature T2' can be reached from the temperature T1' using a low temperature gradient. Therefore, during the step i'), the temperature of the catalyst bed is increased from T1' to a temperature T2' greater than T1'; preferably, the temperature of the catalyst bed is increased from temperature T1' to a temperature T2' greater than T1', wherein the temperature gradient is less than 0.5°C / min. The applied temperature gradient makes it possible to prevent premature degradation of the catalyst and thus enable a better yield or a better productivity of the hydrogenolysis reaction. In particular, the temperature is increased with a temperature gradient of less than 0.45°C / min, or less than 0.40°C / min, or less than 0.35°C / min, or less than 0.30°C / min, or less than 0.25°C / min, or less than 0.20°C / min, or less than 0.15°C / min, or less than 0.10°C / min, or less than 0.05°C / min.

[0042] Preferably, the temperature of the catalytic bed is increased by increasing the contact time, calculated as the ratio of the volume of the catalyst in litres to the total flow rate of the gas stream in standard litres per second at the reactor inlet. The contact time 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. The temperature T1' may be between 0°C and 50°C, advantageously between 10°C and 50°C, preferably between 20°C and 50°C. Preferably, the temperature T2' is lower than the temperature T3 at which step a is carried out. The temperature T3 is preferably between 100°C and 180°C, more preferably between 100°C and 160°C, in particular between 120°C and 160°C.

[0043] Catalyst regeneration

[0044] The catalyst used in the present process can be regenerated. The regeneration step can be carried out in a temperature range of the catalyst bed between 90°C and 450°C. Preferably, the regeneration step is carried out in the presence of hydrogen. Carrying out the regeneration step makes it possible to increase the yield of the reaction compared to the initial yield before regeneration.

[0045] 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 at a temperature of the catalytic bed of 90° C. to 200° C., in particular at a temperature of the catalytic bed of 90° C. to 175° C., more particularly at a temperature of the catalytic bed of 90° C. to 150° C. In particular, the regeneration step is carried out at a low temperature, for example at a low temperature of 90° C. to 200° C. or 90° C. to 175° C. or 90° C. to 150° C., so that compounds harmful to the activity of the catalyst can be desorbed and / or so that phase transformations that change the structure of the catalyst can be limited.

[0046] 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 as a function of the conversion or productivity obtained in step a). The regeneration step can be advantageously carried out at a temperature of the catalytic bed 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, well between 225°C and 280°C, more preferably between 230°C and 280°C. Alternatively, the regeneration step can be carried out at a temperature between 300°C and 450°C, preferably between 300°C and 400°C. The regenerated catalyst can be reused in step a) of the present process.

[0047] Hydrogenolysis

[0048] As mentioned above, the present invention comprises a step of subjecting a composition A comprising chlorotrifluoroethylene to a hydrogenolysis reaction 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 preactivated catalyst and in the gas phase. The hydrogenolysis step consists in simultaneously introducing hydrogen, CTFE and an optional inert gas such as nitrogen in the gas phase and in the presence of the catalyst, the catalyst preferably being activated.

[0049] Preferably, step a) is carried out at a temperature of the fixed catalytic bed between 50° C. and 250° C. Step a) may be carried out at a temperature of the fixed catalytic bed 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. Step a) may also be carried out at a temperature of the fixed catalytic bed 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) can also be carried out at a temperature of the fixed catalytic bed 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, well between 100°C and 160°C, particularly preferably between 120°C and 160°C.

[0050] H 2 The molar ratio of H / CTFE 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 / H 2 The molar ratio is between 0 / 1 and 2 / 1, and preferably between 0 / 1 and 1 / 1.

[0051] Step a) is preferably carried out at a pressure of 0.05 MPa to 1.1 MPa, more preferably 0.05 MPa to 0.5 MPa, in particular at atmospheric pressure.

[0052] The contact time, calculated as the ratio of the volume of catalyst in litres to the total flow rate of the gas mixture in standard litres 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.

[0053] According to the present invention, the composition A further comprises at least one additional compound C1 selected from 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1,1,1-trifluoroethane and 1,2-dichlorohexafluorocyclobutane.

[0054] The composition A may comprise one or more of the additional compounds C1. The composition A may comprise one, two, three, four, five or all of the additional compounds C1.

[0055] Advantageously, the total weight content of the at least one additional compound C1 is less than 15%, based on the total weight of the composition A. Preferably, the total weight content of the at least one additional compound C1 is less than 10%, more preferably less than 5%, in particular less than 2%, more particularly less than 1%.

[0056] Advantageously, the total weight content of the at least one additional compound C1 is greater than 1 ppm, based on the total weight of the composition A. Preferably, the total weight content of the at least one additional compound C1 is greater than 5 ppm, more preferably greater than 10 ppm, in particular greater than 20 ppm, more particularly greater than 50 ppm, well greater than 100 ppm, based on the total weight of the composition A.

[0057] According to a preferred embodiment, composition A contains 1,1,1-trifluoroethane, and the total weight content of 1,1,1-trifluoroethane is less than 5000 ppm, advantageously less than 2500 ppm, preferably less than 1000 ppm, more preferably less than 750 ppm, based on the total weight of the composition A. When it is contained in the composition, the total weight content of 1,1,1-trifluoroethane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, more preferably greater than 20 ppm, particularly greater than 50 ppm, more particularly greater than 100 ppm, based on the total weight of the composition A.

[0058] According to a preferred embodiment, composition A contains 1,1,1,2-tetrafluoroethane, and the total weight content of 1,1,1,2-tetrafluoroethane is less than 1000 ppm, advantageously less than 750 ppm, preferably less than 500 ppm, more preferably less than 250 ppm, and in particular less than 100 ppm, based on the total weight of the composition A. When it is contained in the composition, the total weight content of 1,1,1,2-tetrafluoroethane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, and more preferably greater than 20 ppm, based on the total weight of the composition A.

[0059] According to a preferred embodiment, composition A contains hexafluorocyclobutene, and the total weight content of hexafluorocyclobutene is less than 1%, advantageously less than 7500 ppm, preferably less than 5000 ppm, more preferably less than 2500 ppm, and in particular less than 1000 ppm, based on the total weight of the composition A. When it is contained in the composition, the total weight content of hexafluorocyclobutene is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, more preferably greater than 20 ppm, in particular greater than 50 ppm, and more particularly greater than 100 ppm, based on the total weight of the composition A.

[0060] According to a preferred embodiment, composition A contains fluoroethane, and the total weight content of fluoroethane is less than 100 ppm, advantageously less than 75 ppm, preferably less than 50 ppm, more preferably less than 25 ppm, and in particular less than 10 ppm, based on the total weight of the composition A. When it is contained in the composition, the total weight content of fluoroethane is greater than 0.1 ppm, advantageously greater than 0.5 ppm, and preferably greater than 1 ppm, based on the total weight of the composition A.

[0061] According to a preferred embodiment, composition A contains 2-chloro-1,1,1-trifluoroethane, and the total weight content of 2-chloro-1,1,1-trifluoroethane is less than 1%, advantageously less than 7500 ppm, preferably less than 5000 ppm, more preferably less than 2500 ppm, and especially less than 1000 ppm, based on the total weight of the composition A. When it is contained in the composition, the total weight content of 2-chloro-1,1,1-trifluoroethane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, more preferably greater than 20 ppm, especially greater than 50 ppm, and more especially greater than 100 ppm, based on the total weight of the composition A.

[0062] According to a preferred embodiment, composition A comprises 1,2-dichlorohexafluorocyclobutane. 1,2-dichlorohexafluorocyclobutane can exist in the form of two diastereoisomers. The term "1,2-dichlorohexafluorocyclobutane" refers to two diastereoisomers. Preferably, the total weight content of 1,2-dichlorohexafluorocyclobutane is less than 15%, advantageously less than 10%, preferably less than 5%, and in particular less than 1%, based on the total weight of the composition A. According to an advantageous embodiment, the total weight content of 1,2-dichlorohexafluorocyclobutane is less than 5000ppm, advantageously less than 1000ppm, preferably less than 500ppm, more preferably less than 250ppm, and in particular less than 100ppm, based on the total weight of the composition A. When it is included in the composition, the total weight content of 1,2-dichlorohexafluorocyclobutane is greater than 1ppm, advantageously greater than 5ppm, preferably greater than 10ppm, and more preferably greater than 20ppm, based on the total weight of the composition A.

[0063] According to a preferred embodiment, the composition A comprises at least 80% by weight of chlorotrifluoroethylene, based on the total weight of the composition A, advantageously at least 82% by weight, preferably at least 84% by weight, more preferably at least 86% by weight, in particular at least 88% by weight, more particularly at least 90% by weight, preferably at least 92% by weight of chlorotrifluoroethylene, based on the total weight of the composition A.

[0064] The composition A may also contain trifluoroethylene, preferably in a weight content of less than 5%, preferably less than 4.5%, in particular less than 4%, based on the total weight of the composition A.

[0065] The composition A may optionally contain at least one of the additional compounds C2 selected from 1,1,2-trifluoroethane, 1-chloro-1,1,2-trifluoroethane, 1-chloro-2,2-difluoroethylene, E / Z-1-chloro-1,2-difluoroethylene and 1-chloro-1,2,2-trifluoroethane. The weight content of the at least one of the additional compounds C2 may be less than 5% based on the total weight of the composition A, advantageously less than 4%, preferably less than 3%, more preferably less than 2%, and in particular less than 1% based on the total weight of the composition A.

[0066] Processing of reactive streams

[0067] The stream B obtained from step a) can be treated to recover a purified trifluoroethylene (HFO-1123) stream. In addition to trifluoroethylene, the stream B may also contain HF, HCl, unreacted hydrogen, unreacted chlorotrifluoroethylene, and any one or more of additional compounds C1 or C2.

[0068] The logistics B can be processed according to the following steps:

[0069] i) removing HF and / or HCl from said product stream obtained in step a) to form a gas mixture;

[0070] ii) drying the gas mixture obtained in step i);

[0071] iii) treating the gas mixture dried in step ii) to remove hydrogen and optionally inert gases;

[0072] iv) distilling the mixture obtained from step iii).

[0073] The stream B obtained from step a) is collected in gaseous form at the reactor outlet. 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 scrubber and subsequently washed with a dilute alkali such as NaOH or KOH. 2The remainder of the gas mixture consisting of trifluoroethylene and CTFE), diluent nitrogen (if present), trifluoroethylene and the above-mentioned additional compounds is directed to a dryer to remove traces of washing water. Drying can be carried out using products such as calcium sulfate, sodium sulfate or magnesium sulfate, calcium chloride, potassium carbonate, silica gel or zeolite. In one embodiment, molecular sieves (zeolites) such as siliceous pores are used for drying. The gas mixture thus dried is subjected to the following steps: at a temperature below ambient temperature for absorption, preferably at a temperature below 10°C, and more preferably also at a temperature of -25°C and at atmospheric pressure, in the presence of an alcohol containing 1 to 4 carbon atoms and preferably ethanol, hydrogen and inert substances are separated from the remainder of other products present in the gas mixture by absorption / desorption. In one embodiment, the absorption of organic matter is carried out in a countercurrent tower, in which ethanol is cooled to -25°C. The ethanol flow rate is adjusted according to the flow rate of the organic matter to be absorbed. Hydrogen and inert gases that are insoluble in ethanol at this temperature are removed at the top of the absorption tower. The organic matter is subsequently recovered by heating the ethanol to its boiling point (desorption) for subsequent distillation. Alternatively, step iii) can be carried out by a membrane separation process.

[0074] According to step iv), the organic compounds thus obtained are distilled to form and recover a stream D1 comprising trifluoroethylene and a stream D2 comprising chlorotrifluoroethylene and optionally one or more of the additional compounds C1 or C2. Stream D2 can be recycled to step a).

[0075] According to a preferred embodiment, the distillation step iv) is carried out at a pressure of less than 3 bara, preferably at a pressure between 0.5 and 3 bara, in particular at a pressure between 0.9 and 2 bara. Carrying out the distillation at a pressure of less than 3 bara makes it possible to make the process safer due to the explosive properties of trifluoroethylene above 3 bara. Preferably, the distillation step iv) is carried out in a distillation tower comprising a structured filler. It has been observed that the structured filler makes it possible to obtain a more efficient distillation step. The structured filler can be made of a metallic material. The logistics D1 is preferably collected at the top of the distillation tower. Before collection, the logistics D1 can optionally be partially condensed at the top of the distillation tower. When partial condensation is carried out, the logistics D1 is brought to a temperature of -50°C to -70°C. The temperature is adjusted according to the applied pressure. Partial condensation makes it possible to improve the efficiency of the distillation by limiting the content of additional compounds in the logistics D1. Said stream D1 may comprise, based on the total weight of said stream B, at least 95% by weight, advantageously at least 96% by weight, preferably at least 97% by weight, in particular at least 98% by weight, more particularly at least 99% by weight, of trifluoroethylene.

[0076] Composition

[0077] According to a second aspect, the present invention provides a composition comprising chlorotrifluoroethylene.

[0078] The composition comprises at least 80 weight percent of chlorotrifluoroethylene and at least one of additional compounds selected from 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1,1,1-trifluoroethane and 1,2-dichlorohexafluorocyclobutane; the total weight content of the at least one of the additional compounds is less than 15% based on the total weight of the composition.

[0079] According to a preferred embodiment, the composition comprises 1,1,1-trifluoroethane, and the total weight content of 1,1,1-trifluoroethane is less than 5000 ppm, advantageously less than 2500 ppm, preferably less than 1000 ppm, more preferably less than 750 ppm, based on the total weight of the composition. When it is contained in the composition, the total weight content of 1,1,1-trifluoroethane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, more preferably greater than 20 ppm, particularly greater than 50 ppm, more particularly greater than 100 ppm, based on the total weight of the composition.

[0080] According to a preferred embodiment, the composition comprises 1,1,1,2-tetrafluoroethane, and the total weight content of 1,1,1,2-tetrafluoroethane is less than 1000 ppm, advantageously less than 750 ppm, preferably less than 500 ppm, more preferably less than 250 ppm, and in particular less than 100 ppm, based on the total weight of the composition. When it is included in the composition, the total weight content of 1,1,1,2-tetrafluoroethane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, and more preferably greater than 20 ppm, based on the total weight of the composition.

[0081] According to a preferred embodiment, the composition comprises hexafluorocyclobutene, and the total weight content of hexafluorocyclobutene is less than 1%, advantageously less than 7500ppm, preferably less than 5000ppm, more preferably less than 2500ppm, and in particular less than 1000ppm, based on the total weight of the composition. When it is included in the composition, the total weight content of hexafluorocyclobutene is greater than 1ppm, advantageously greater than 5ppm, preferably greater than 10ppm, more preferably greater than 20pm, in particular greater than 50ppm, and more particularly greater than 100ppm, based on the total weight of the composition.

[0082] According to a preferred embodiment, the composition comprises fluoroethane, and the total weight content of fluoroethane is less than 100 ppm, advantageously less than 75 ppm, preferably less than 50 ppm, more preferably less than 25 ppm, in particular less than 10 ppm, based on the total weight of the composition. When it is included in the composition, the total weight content of fluoroethane is greater than 0.1 ppm, advantageously greater than 0.5 ppm, preferably greater than 1 ppm, based on the total weight of the composition.

[0083] According to a preferred embodiment, the composition contains 2-chloro-1,1,1-trifluoroethane, and the total weight content of 2-chloro-1,1,1-trifluoroethane is less than 1%, advantageously less than 7500 ppm, preferably less than 5000 ppm, more preferably less than 2500 ppm, and in particular less than 1000 ppm, based on the total weight of the composition. When it is contained in the composition, the total weight content of 2-chloro-1,1,1-trifluoroethane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, more preferably greater than 20 ppm, in particular greater than 50 ppm, and more particularly greater than 100 ppm, based on the total weight of the composition.

[0084] According to a preferred embodiment, the composition comprises 1,2-dichlorohexafluorocyclobutane, and the total weight content of 1,2-dichlorohexafluorocyclobutane is less than 15%, advantageously less than 10%, preferably less than 5%, and in particular less than 1%, based on the total weight of the composition. According to an advantageous embodiment, the total weight content of 1,2-dichlorohexafluorocyclobutane is less than 5000 ppm, advantageously less than 1000 ppm, preferably less than 500 ppm, more preferably less than 250 ppm, and in particular less than 100 ppm, based on the total weight of the composition. When it is included in the composition, the total weight content of 1,2-dichlorohexafluorocyclobutane is greater than 1 ppm, advantageously greater than 5 ppm, preferably greater than 10 ppm, and more preferably greater than 20 ppm, based on the total weight of the composition.

[0085] Example

[0086] 25cm 3The catalyst (0.2% of palladium supported on alpha-alumina) is introduced into a tubular reactor consisting of a stainless steel tube with a length of 1200 mm, a diameter of 25 mm and equipped with a jacket. The catalyst thus loaded is then activated in the following manner: the reaction tube is placed in a tubular furnace and fed with a stream of hydrogen (0.05 to 0.1 mol per gram of catalyst). The catalytic bed is heated to a temperature of 200° C. to 250° C. with a temperature gradient of 0.2° C. / min. After this activation phase, the tube is cooled to ambient temperature and then isolated for subsequent installation on a hydrogenolysis test bench.

[0087] Four test beds, each comprising a reactor prepared as described above, were used in parallel. The four beds were fed with 1 mol / h of the starting composition and 1 mol / h of hydrogen in anhydrous form. The temperature of the reactor jacket was 25°C. The contact time was about 22 seconds, calculated as the ratio of the volume of the catalyst in liters to the sum of the flow rates of the reactants in standard liters / second. Various starting compositions were used for testing. Comparative Example 1 was carried out starting with chlorotrifluoroethylene. Example 2 according to the invention was carried out starting with the chlorotrifluoroethylene used in the comparative example, to which the following compounds were added to obtain a composition A having the ratios mentioned for each component: 1,1,1-trifluoroethane (519 ppm), 1,1,1,2-tetrafluoroethane (39 ppm), hexafluorocyclobutene (880 ppm), fluoroethane (5 ppm), 2-chloro-1,1,1-trifluoroethane (600 ppm), 1,2-dichlorohexafluorocyclobutane (68 ppm) and trifluoroethylene (2.9%), the remainder of which was chlorotrifluoroethylene.

[0088] Example 3 according to the invention was carried out starting from the chlorotrifluoroethylene used in the comparative example, to which the following compounds were added to obtain composition A having the proportions mentioned for each component: 1,1,1-trifluoroethane (453 ppm), 1,1,1,2-tetrafluoroethane (56 ppm), hexafluorocyclobutene (754 ppm), 2-chloro-1,1,1-trifluoroethane (455 ppm), and 1,2-dichlorohexafluorocyclobutane (54 ppm), with the remainder being chlorotrifluoroethylene.

[0089] Example 4 according to the invention was carried out starting from the chlorotrifluoroethylene used in the comparative example, to which the following compounds were added to obtain a composition A having the proportions mentioned for each component: 1,1,1-trifluoroethane (450 ppm), 1,1,1,2-tetrafluoroethane (52 ppm), and 2-chloro-1,1,1-trifluoroethane (467 ppm), with the remainder being chlorotrifluoroethylene.

[0090] The results are shown in Table 1 below:

[0091] [Table 1]

[0092]

[0093] The productivity mentioned corresponds to the sum of the productivity obtained for all four hydrogenolysis beds.As can be seen, starting from the composition according to the invention, the trifluoroethylene productivity is significantly improved compared to the chlorotrifluoroethylene composition containing no additional compound.

Claims

1. A process for producing trifluoroethylene in a reactor equipped with a fixed catalytic bed comprising a catalyst, said process comprising the steps a) of reacting a composition A comprising chlorotrifluoroethylene with hydrogen in the presence of a catalyst and in the gas phase to produce a stream B comprising trifluoroethylene, Features The composition A further comprises at least one of additional compounds C1 selected from 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1,1,1-trifluoroethane and 1,2-dichlorohexafluorocyclobutane.

2. A process as claimed in the preceding claims, characterised in that The total weight content of the at least one additional compound C1 is less than 15%, based on the total weight of the composition A, preferably less than 10%, in particular less than 5%, based on the total weight of the composition A.

3. The process as claimed in one of the preceding claims, characterized in that The composition A comprises at least 80% by weight of chlorotrifluoroethylene, based on the total weight of the composition A, preferably at least 85% by weight of chlorotrifluoroethylene, based on the total weight of the composition A, in particular at least 90% by weight of chlorotrifluoroethylene, based on the total weight of the composition A.

4. A process as claimed in any one of the preceding claims, characterised in that The composition A further comprises trifluoroethylene, preferably also in a weight content of less than 5%, based on the total weight of the composition A.

5. A process as claimed in any one of the preceding claims, characterised in that The composition A further comprises at least one additional compound C2 selected from 1,1,2-trifluoroethane, 1-chloro-1,1,2-trifluoroethane, 1-chloro-2,2-difluoroethylene, E / Z-1-chloro-1,2-difluoroethylene and 1-chloro-1,2,2-trifluoroethane.

6. A process as claimed in the preceding claims, characterised in that The weight content of the at least one additional compound C2, based on the total weight of the composition A, is less than 5%.

7. A process as claimed in any one of the preceding claims, characterised in that The catalyst comprises palladium supported on alpha-alumina.

8. A process as claimed in any one of the preceding claims, characterised in that Chlorotrifluoroethylene and hydrogen are in anhydrous form.

9. A process as claimed in any one of the preceding claims, characterised in that The process comprises a step i') of activating the catalyst prior to step a) by contacting the catalyst with a gas stream comprising a reducing agent, an inert gas or a mixture thereof.

10. A process as claimed in the preceding claims, characterised in that During said step i'): - the temperature of the catalyst bed is increased from temperature T1 to temperature T2 which is higher than T1, wherein the temperature gradient is less than 0.5°C / min; or - The temperature of the catalytic bed is increased incrementally from a temperature T1 to a temperature T2 which is higher than T1.

11. A composition comprising at least 80 weight percent chlorotrifluoroethylene and at least one additional compound selected from the group consisting of 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, hexafluorocyclobutene, fluoroethane, 2-chloro-1,1,1-trifluoroethane, and 1,2-dichlorohexafluorocyclobutane; the total weight content of the at least one additional compound being less than 15%, based on the total weight of the composition.

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