Method for producing trifluoroethylene

Abstract

The present invention relates to a method for producing trifluoroethylene in a reactor equipped with a fixed catalyst bed containing a catalyst, the method comprising the step of: a) reacting in the gas phase, in the presence of a catalyst, a composition A containing chlorotrifluoroethylene with hydrogen to produce a stream B containing trifluoroethylene, said composition A also containing at least one 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 present invention also relates to a method for producing a chlorotrifluoroethylene composition.

Description

[Technical field]

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

[0002] Fluoroolefins (eg, VF3) are known and used as monomers or comonomers to prepare fluorocarbon polymers that exhibit noteworthy properties, particularly excellent chemical resistance and good heat resistance.

[0003] Trifluoroethylene is a gas under standard conditions of pressure and temperature. The main risks associated with the use of this product relate to its flammability, tendency to self-polymerize if not stabilized, explosiveness due to chemical instability, and supposed sensitivity to peroxidation (similar to other halogenated olefins). Trifluoroethylene has the distinctive feature of being highly flammable, with a lower explosion limit (LEL) of approximately 10% and an upper explosion limit (UEL) of approximately 30%. The main danger, however, is related to the tendency 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] Considering the main risks mentioned above, the synthesis of VF3, but also its storage, poses particular problems and strict safety regulations are imposed throughout these processes. In the known route for the preparation of trifluoroethylene, chlorotrifluoroethylene (CTFE) and hydrogen are used as starting materials in the gas phase in the presence of a catalyst.

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

[0006] From EP 2 993 213, a process for producing trifluoroethylene is known. It is obtained by hydrogenolysis of chlorotrifluoroethylene or by pyrolysis of chlorodifluoromethane and chlorofluoromethane. The production process involves carrying out a distillation step at a pressure of 10 barg, with the trifluoroethylene being recovered by side draw. To carry out the high-pressure distillation, specific operating conditions must be established due to the explosive nature of trifluoroethylene above 3 bara.

[0007] Thus, there is a need to provide a simpler and safer process for producing trifluoroethylene while maintaining high yields and selectivity.

[0008] Summary of the Invention According to a first aspect, the invention provides a method for producing trifluoroethylene in a reactor comprising a fixed catalyst bed comprising a catalyst, the method comprising step a) reacting a composition A comprising chlorotrifluoroethylene with hydrogen in the presence of a catalyst in the gas phase to produce a stream B comprising trifluoroethylene, said composition A also comprising at least one 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.

[0009] Surprisingly, it has been observed that the productivity of trifluoroethylene increases in the presence of additional compounds C1. The presence of small amounts of these compounds in addition to chlorotrifluoroethylene allows for an improvement in the trifluoroethylene production process. The present invention demonstrates that chlorotrifluoroethylene does not need to be highly pure to achieve high productivity. This simplifies the production process and reduces its overall cost.

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

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

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

[0013] According to a preferred embodiment, the composition A also comprises at least one additional compound C2 selected from the group consisting of 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 is less than 5% based on the total weight of the composition A.

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

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

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

[0018] According to a preferred embodiment, during step i'), increasing the temperature of the catalyst bed from a temperature T1 to a temperature T2 higher than T1 with a temperature gradient of less than 0.5° C. / min; or The temperature of the catalyst bed is incrementally increased from a temperature T1 to a temperature T2 which is higher than T1.

[0019] According to a second embodiment, the present invention provides a composition comprising at least 80% by weight of 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, wherein the total weight content of the at least one additional compound is less than 15%, based on the total weight of the composition.

[0020] Detailed Description of the Invention The present invention relates to a method for producing trifluoroethylene, which comprises a step of hydrogenolysis of chlorotrifluoroethylene (CTFE) with hydrogen in a gas phase, preferably in the presence of a catalyst.

[0021] According to a preferred embodiment, the process according to the invention described herein is carried out continuously.

[0022] According to a preferred embodiment, in the process according to the invention described herein, the hydrogen is in anhydrous form.

[0023] According to a preferred embodiment, in the process according to the invention described herein, the chlorotrifluoroethylene is in anhydrous form.

[0024] Carrying out the process according to the invention in the presence of anhydrous hydrogen and / or chlorotrifluoroethylene makes it possible to effectively extend the catalyst life and thus improve the overall productivity of the process.The term "anhydrous" refers to a weight content of water of less than 1000 ppm, advantageously less than 500 ppm, preferably less than 200 ppm, in particular less than 100 ppm, based on the total weight of the compounds considered.

[0025] catalyst The catalyst is preferably based on a metal from groups 8 to 10 of the periodic table of the elements. The catalyst is in particular based on a metal selected from the group consisting of Pd, Pt, Rh and Ru, preferably palladium.

[0026] The catalyst is preferably supported. The support is preferably selected from the group consisting of activated carbon, aluminum-based supports, calcium carbonate and graphite. The support is preferably aluminum-based. The support is in particular alumina. The alumina may be α-alumina. The alumina preferably comprises at least 90% α-alumina. It has been observed that when the alumina is α-alumina, the conversion of the hydrocracking reaction is improved. The catalyst is therefore more in particular palladium supported on alumina, advantageously palladium supported on alumina comprising at least 90% α-alumina, preferably palladium supported on α-alumina. 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.

[0027] The catalyst in particular comprises 0.01 to 5% by weight of palladium supported on alumina; preferably, the alumina comprises at least 90% α-alumina; more preferentially, the alumina is α-alumina.

[0028] Catalyst activation The catalyst is preferably activated before use in step a), preferably at elevated temperature in the presence of a reducing agent, an inert gas or a mixture thereof.

[0029] In certain embodiments, the reducing agent is selected from the group consisting of hydrogen, carbon monoxide, nitric oxide, formaldehyde, C1-C6 alkanes, and C1-C 10 or mixtures thereof; preferably hydrogen or C1-C 10 in particular, selected from the group consisting of hydrogen, chlorotrifluoroethylene, trifluoroethylene, chlorotrifluoroethane, trifluoroethane or difluoroethane, or mixtures thereof.

[0030] The inert gas may be nitrogen or argon, preferably nitrogen.

[0031] The activation of the catalyst is preferably carried out at a temperature of 100° C. to 400° C., in particular at a temperature of 150° C. to 350° C. The activation of the catalyst is especially carried out at a temperature of 100° C. to 400° C., in particular at a temperature of 150° C. to 350° C., in the presence of hydrogen as a reducing agent.

[0032] Preferably, during step i'), the temperature of the catalyst bed is increased from temperature T1 to temperature T2. In particular, during said step i'), the temperature of the catalyst bed is increased from temperature T1 to a temperature T2 higher than T1 with a temperature gradient of less than 0.5 ° C. / min. The applied temperature gradient makes it possible to prevent premature deterioration of the catalyst, which leads to a better yield or productivity of the hydrocracking reaction. The temperature is increased in particular 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 can be between 0°C and 150°C, advantageously between 0°C and 120°C, preferably between 0°C and 100°C, more preferentially between 10°C and 100°C, in particular between 20°C and 100°C, even more particularly between 20°C and 75°C, preferably 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 preferentially between 160°C and 350°C, in particular between 165°C and 325°C, in particular between 170°C and 320°C, preferably between 175°C and 310°C, more preferably 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 preferentially between 195° C. and 270° C., in particular between 200° C. and 260° C. The temperature T2 may be maintained for 5 minutes to 200 hours, preferably for 10 minutes to 100 hours, in particular for 15 minutes to 75 hours, more particularly for 30 minutes to 50 hours, and preferably for 1 hour to 25 hours. The temperature T2 may be maintained for 5 minutes to 24 hours, preferably for 10 minutes to 20 hours, in particular for 15 minutes to 15 hours, more particularly for 30 minutes to 10 hours, and preferably for 1 hour to 10 hours.

[0033] The gas stream used during step i') is preferably free of oxygen. Step i') may preferably be carried out with an amount of reducing agent greater than 0.01 moles per gram of catalyst, preferably greater than 0.05 moles per gram of catalyst. Step i') may in particular be carried out with an amount of reducing agent between 0.01 and 10 moles per gram of catalyst, preferably between 0.05 and 5 moles per gram of catalyst.

[0034] According to another embodiment, during said step i'), the temperature of the catalyst bed is increased incrementally from temperature T1 to temperature T2. By incrementally activating the catalyst, the performance of the catalyst can be improved. By doing it incrementally, it is possible to prevent catalyst degradation. It has also been observed that if the temperature increase between the increments is gentle and relatively slow compared to the usual catalyst activation conditions, the properties of the catalyst are additionally further improved. Thus, 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 two increments makes it possible to prevent premature catalyst degradation, which leads to a better yield or productivity of the hydrocracking reaction. The temperature is increased in particular 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. Temperature T1 can be the ambient temperature. Alternatively, temperature T1 can be between 0° C. and 150° C., advantageously between 0° C. and 120° C., preferably between 0° C. and 100° C., more preferentially between 10° C. and 100° C., in particular between 20° C. and 100° C., even more particularly between 20° C. and 75° C., suitably between 20° C. and 50° C. 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 preferentially between 160° C. and 350° C., in particular between 165° C. and 325° C., in particular between 170° C. and 320° C., preferably between 175° C. and 310° C., more preferably 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 preferentially between 195° C. and 270° C., in particular between 200° C. and 260° C. The temperature T2 can be maintained for 5 minutes to 200 hours, preferably for 10 minutes to 100 hours, in particular for 15 minutes to 75 hours, more particularly for 30 minutes to 50 hours, preferably for 1 hour to 25 hours. The temperature T2 may be maintained for 5 minutes to 24 hours, preferably 10 minutes to 20 hours, in particular 15 minutes to 15 hours, more in particular 30 minutes to 10 hours, preferably 1 hour to 10 hours.Step i') of activating the catalyst comprises at least one increment between temperatures T1 and T2. Step i') of activating the catalyst may comprise several increments between temperatures T1 and T2. Step i') preferably comprises at least one increment at a temperature T1a between 90 and 120°C. The presence of increments between 90°C and 120°C should be favorable to extend the life of the catalyst. Step i') may also comprise one or more increments between temperatures T1 and T1a and / or between temperatures T1a and T2. Each increment between temperatures T1 and T2 may preferably last for between 5 minutes and 200 hours, preferably between 10 minutes and 100 hours, in particular between 15 minutes and 75 hours, and more in particular between 30 minutes and 50 hours. In particular, each increment between temperatures T1 and T2 may be maintained for 5 minutes to 24 hours, preferably for 10 minutes to 20 hours, in particular for 15 minutes to 15 hours, more in particular for 30 minutes to 10 hours. In particular, the increment at temperature T1a may be maintained for 5 minutes to 200 hours, preferably for 10 minutes to 100 hours, in particular for 15 minutes to 75 hours, more in particular for 30 minutes to 50 hours. The increment at temperature T1a may suitably be maintained for 5 minutes to 24 hours, preferably for 10 minutes to 20 hours, in particular for 15 minutes to 15 hours, more in particular for 30 minutes to 10 hours.

[0035] The gas flow used during step i′) may vary over time. For example, the gas flow may contain an inert gas between two increments and, for example, a reducing agent between the other two increments. In particular, the gas flow contains an inert gas when step i′) is performed between temperatures T1 and T1a, and a reducing agent (preferably hydrogen or a C1-C2 as defined above) when step i′) is performed between temperatures T1a and T2. 10 Thus, the gas flow used in step i′) is changed during the increments made at temperature T1a. Alternatively, the gas flow may be changed throughout step i′) to include a reducing agent, such as hydrogen or a C1-C alkane as defined above. 10 The reducing agent may include a halohydrocarbon, optionally mixed with an inert gas, such as nitrogen. The reducing agent may include a reducing agent such as hydrogen or any of the C1-C 10It has been observed that the use of halohydrocarbons (optionally mixed with an inert gas, for example nitrogen) shows an additional advantage in terms of productivity during the temperature increase between the increment temperatures T1a and T2. As mentioned above, the temperature T2 is maintained for a certain time. During this increment at temperature T2, the gas flow can be changed. Thus, the gas flow can be hydrogen or the C1-C 2 -C 1 - ... 10 It may contain halohydrocarbons. In particular, the gas stream may contain hydrogen, chlorotrifluoroethylene, trifluoroethane, trifluoroethylene, chlorotrifluoroethane, or difluoroethane during the increment at temperature T2. Preferably, step i') may be carried out with 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') may be carried out with an amount of reducing agent between 0.01 and 10 moles per gram of catalyst, preferably between 0.05 and 5 moles per gram of catalyst.

[0036] According to another embodiment, step i') of activating the catalyst comprises contacting the catalyst with a gas stream containing chlorotrifluoroethylene and optionally hydrogen. It has been observed that chlorotrifluoroethylene (CTFE) makes it possible to activate the catalyst, especially when only hydrogen is also present. This allows the trifluoroethylene production process to be improved. Activation in the presence of CTFE allows the catalyst to be activated at low temperatures, which results in a less energy-intensive process. This process is further simplified, since the reducing agent during activation is also one of the reactants for the subsequent reaction. Preferably, in this embodiment, step i') is carried out at a temperature T2' below 100°C. This temperature T2' can be reached from temperature T1' using a low temperature gradient. Thus, during this step i'), the temperature of the catalyst bed is increased from temperature T1' to a temperature T2' higher than T1'; the temperature of the catalyst bed is preferably increased from temperature T1' to a temperature T2' higher than T1' with a temperature gradient of less than 0.5°C / min. The applied temperature gradient can prevent premature catalyst degradation, thereby resulting in better yield or productivity of the hydrocracking reaction. The temperature is particularly 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.

[0037] Preferably, the temperature of the catalyst bed is increased by increasing the contact time, calculated as the ratio of the volume of catalyst (liters) to the total flow rate of the gas streams at the inlet of the reactor (standard liters / second). The contact time is between 1 and 60 seconds, preferably between 5 and 45 seconds, in particular between 10 and 30 seconds, in particular between 15 and 25 seconds. The temperature T1' can 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 preferentially between 100°C and 160°C, in particular between 120°C and 160°C.

[0038] Catalyst regeneration The catalyst used in the present process may be regenerated. This regeneration step may be carried out at a catalyst bed temperature range between 90°C and 450°C. Preferably, the regeneration step is carried out in the presence of hydrogen. By carrying out the regeneration step, the yield of the reaction can be improved compared to the initial yield before regeneration.

[0039] According to a preferred embodiment, the regeneration step can be carried out at a catalyst bed temperature of 90° C. to 300° C., preferably at a catalyst bed temperature of 90° C. to 250° C., more preferentially at a catalyst bed temperature of 90° C. to 200° C., in particular at 90° C. to 175° C., and even more particularly at 90° C. to 150° C. In particular, carrying out the regeneration step at low temperatures, for example at 90° C. to 200° C., or 90° C. to 175° C., or 90° C. to 150° C., allows desorption of compounds harmful to the activity of the catalyst and / or limiting phase transformations that modify the structure of the catalyst.

[0040] According to another preferred embodiment, the regeneration step can be carried out at a catalyst bed temperature of more than 200°C, advantageously more than 230°C, preferably more than 250°C, in particular more than 300°C. The regeneration step can be carried out periodically as a function of the productivity or as a function of the conversion obtained in step a). The regeneration step can be advantageously carried out at a catalyst bed temperature between 200°C and 300°C, preferably between 205°C and 295°C, more preferentially between 210°C and 290°C, in particular between 215°C and 290°C, even 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 can be carried out at a temperature between 300°C and 450°C, preferably between 300°C and 400°C. The regenerated catalyst can be reused in step a) of the process.

[0041] Hydrogenolysis Reaction As mentioned above, the present invention comprises a step of hydrocracking a composition A containing chlorotrifluoroethylene with hydrogen to produce a stream containing trifluoroethylene. The hydrocracking step is carried out in the gas phase in the presence of a catalyst. Preferably, the hydrocracking step is carried out in the gas phase in the presence of a pre-activated catalyst. The hydrocracking step consists of simultaneously introducing hydrogen, CTFE, and optionally an inert gas (e.g., nitrogen) in the gas phase in the presence of the catalyst (preferably activated).

[0042] The step a) is preferably carried out at a fixed catalyst bed temperature between 50° C. and 250° C. The step a) can be carried out at a fixed catalyst bed temperature between 50° C. and 240° C., advantageously between 50° C. and 230° C., preferably between 50° C. and 220° C., more preferentially between 50° C. and 210° C., in particular between 50° C. and 200° C. The step a) can also be carried out at a fixed catalyst bed temperature between 60° C. and 250° C., advantageously between 70° C. and 250° C., preferably between 80° C. and 250° C., more preferentially between 90° C. and 250° C., in particular between 100° C. and 250° C., more particularly between 120° C. and 250° C. Said step a) may also be carried out at a fixed catalyst bed temperature between 60°C and 240°C, advantageously between 70°C and 230°C, preferably between 80°C and 220°C, more preferentially between 90°C and 210°C, in particular between 100°C and 200°C, more particularly between 100°C and 180°C, suitably between 100°C and 160°C and particularly preferably between 120°C and 160°C.

[0043] The molar ratio of H2 / CTFE is between 0.5 / 1 and 2 / 1, preferably between 1 / 1 and 1.2 / 1. If an inert gas (e.g. nitrogen) is present in step a), the molar ratio of nitrogen / H2 is between 0 / 1 and 2 / 1, preferably between 0 / 1 and 1 / 1.

[0044] Step a) is preferably carried out at a pressure between 0.05 MPa and 1.1 MPa, more preferentially at a pressure between 0.05 MPa and 0.5 MPa, in particular at atmospheric pressure.

[0045] The contact time (calculated as the ratio of catalyst volume (liters) to the total flow rate of the gas mixture (standard liters / second)) at the reactor inlet is between 1 and 60 seconds, preferably between 5 and 45 seconds, in particular between 10 and 30 seconds, and more particularly between 15 and 25 seconds.

[0046] According to the invention, composition A also comprises at least one 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.

[0047] The composition A may comprise one or more additional compounds C1. The composition A may comprise one, two, three, four, five or all of the additional compounds C1.

[0048] 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 preferentially less than 5%, in particular less than 2% and even more particularly less than 1%.

[0049] Advantageously, the total weight content of the at least one additional compound C1 is greater than 1 ppm, based on the total weight of composition A. Preferably, the total weight content of the at least one additional compound C1 is greater than 5 ppm, more preferentially greater than 10 ppm, in particular greater than 20 ppm, more particularly greater than 50 ppm and preferably greater than 100 ppm, based on the total weight of composition A.

[0050] According to a preferred embodiment, composition A comprises 1,1,1-trifluoroethane, the total weight content of 1,1,1-trifluoroethane being less than 5000 ppm, advantageously less than 2500 ppm, preferably less than 1000 ppm and more preferentially less than 750 ppm, based on the total weight of composition A. When 1,1,1-trifluoroethane 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 preferentially greater than 20 ppm, in particular greater than 50 ppm and more particularly greater than 100 ppm, based on the total weight of composition A.

[0051] According to a preferred embodiment, composition A comprises 1,1,1,2-tetrafluoroethane, the total weight content of 1,1,1,2-tetrafluoroethane being less than 1000 ppm, advantageously less than 750 ppm, preferably less than 500 ppm, more preferentially less than 250 ppm and in particular less than 100 ppm, based on the total weight of composition A. When 1,1,1,2-tetrafluoroethane 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 preferentially greater than 20 ppm, based on the total weight of composition A.

[0052] According to a preferred embodiment, composition A comprises hexafluorocyclobutene, the total weight content of hexafluorocyclobutene being less than 1%, advantageously less than 7500 ppm, preferably less than 5000 ppm, more preferentially less than 2500 ppm, in particular less than 1000 ppm, based on the total weight of composition A. When hexafluorocyclobutene 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 preferentially greater than 20 ppm, in particular greater than 50 ppm, in particular greater than 100 ppm, based on the total weight of composition A.

[0053] According to a preferred embodiment, composition A comprises fluoroethane, the total weight content of fluoroethane being less than 100 ppm, advantageously less than 75 ppm, preferably less than 50 ppm, more preferentially less than 25 ppm and in particular less than 10 ppm, based on the total weight of composition A. When fluoroethane 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 composition A.

[0054] According to a preferred embodiment, composition A comprises 2-chloro-1,1,1-trifluoroethane, the total weight content of 2-chloro-1,1,1-trifluoroethane being less than 1%, advantageously less than 7500 ppm, preferably less than 5000 ppm, more preferentially less than 2500 ppm, in particular less than 1000 ppm, based on the total weight of composition A. When 2-chloro-1,1,1-trifluoroethane 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 preferentially greater than 20 ppm, in particular greater than 50 ppm, and more particularly greater than 100 ppm, based on the total weight of composition A.

[0055] 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 the two diastereoisomers. Preferably, the total weight content of 1,2-dichlorohexafluorocyclobutane is less than 15%, advantageously less than 10%, preferably less than 5%, in particular less than 1%, based on the total weight of composition A. According to a preferred 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 preferentially less than 250 ppm, in particular less than 100 ppm, based on the total weight of composition A. When 1,2-dichlorohexafluorocyclobutane is present 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 preferentially greater than 20 ppm, based on the total weight of composition A.

[0056] According to a preferred embodiment, composition A comprises at least 80% by weight of chlorotrifluoroethylene, based on the total weight of composition A, advantageously at least 82% by weight, preferably at least 84% by weight, more preferentially at least 86% by weight, in particular at least 88% by weight, further in particular at least 90% by weight, preferably at least 92% by weight, based on the total weight of composition A.

[0057] Composition A also comprises 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 composition A.

[0058] The composition A may optionally comprise at least one additional compound C2 selected from the group consisting of 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 additional compound C2 may be less than 5%, based on the total weight of the composition A, advantageously less than 4%, preferably less than 3%, more preferentially less than 2% and in particular less than 1%, based on the total weight of the composition A.

[0059] Reacting Flow Treatment Stream B resulting from step a) can be treated to recover a purified trifluoroethylene (HFO-1123) stream, which in addition to trifluoroethylene can contain HF, HCl, unreacted hydrogen, unreacted chlorotrifluoroethylene, and optionally one or more additional compounds C1 or C2.

[0060] The stream B may be treated by the following steps: i) removing HF and / or HCl from the product stream obtained from step a) to form a gas mixture; ii) drying the gas mixture resulting from step i), iii) treating the gas mixture dried in step ii) to remove hydrogen and, optionally, inert gases; iv) distilling the mixture resulting from step iii).

[0061] Stream B resulting from step a) is withdrawn in gaseous form at the reactor outlet. Preferably, at the outlet of the hydrocracking reactor, the product stream is first treated to remove HCl and HF. The product stream passes through water in a washing column and is subsequently washed with a dilute base (for example NaOH or KOH). The remainder of the gas mixture consisting of unconverted reactants (H2 and CTFE), dilute nitrogen (if present), trifluoroethylene and the abovementioned additional compounds is led 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 zeolites. In one embodiment, molecular sieves (zeolites), for example silipolite, are used for drying. The gas mixture thus dried is subjected to a step of separating hydrogen and inert substances from the residues of other products present in the gas mixture by absorption / desorption (for absorption at temperatures below ambient, preferably below 10° C., more preferably at −25° C.) in the presence of an alcohol having 1 to 4 carbon atoms, preferably ethanol, at atmospheric pressure. In one embodiment, the absorption of the organic substances is carried out in a countercurrent column in which the ethanol is cooled to −25° C. The flow rate of the ethanol is adjusted according to the flow rate of the organic substances to be absorbed. Hydrogen and inert gases (which are insoluble in ethanol at this temperature) are removed at the top of the absorption column. The organic substances are then recovered by heating the ethanol to its boiling point (desorption) followed by distillation. Alternatively, step iii) can be carried out by a membrane separation process.

[0062] 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 additional compounds C1 and C2. Stream D2 can be recycled to step a).

[0063] According to a preferred embodiment, the distillation step iv) is carried out at a pressure below 3 bara, preferably between 0.5 and 3 bara, in particular between 0.9 and 2 bara. Carrying out the distillation at a pressure below 3 bara makes it possible to make the process safer (due to the explosive nature of trifluoroethylene above 3 bara). Preferably, the distillation step iv) is carried out in a distillation column comprising a structured packing. It has been observed that the structured packing makes it possible to obtain a more efficient distillation process. The structured packing may be made of a metallic material. Said stream D1 is preferably withdrawn at the top of the distillation column. Before withdrawal, stream D1 can optionally be partially condensed at the top of the distillation column. When partial condensation is carried out, stream D1 has a temperature of -50°C to -70°C. This temperature is adjusted depending on the applied pressure. The partial condensation makes it possible to improve the efficiency of the distillation by limiting the content of additional compounds in stream D1. The stream D1 may comprise at least 95% by weight, advantageously at least 96%, preferably at least 97%, in particular at least 98%, and more in particular at least 99% by weight, based on the total weight of the stream B, of trifluoroethylene.

[0064] composition According to a second aspect, the present invention provides a composition comprising chlorotrifluoroethylene.

[0065] The composition comprises at least 80% by weight of 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, wherein the total weight content of the at least one additional compound is less than 15%, based on the total weight of the composition.

[0066] According to a preferred embodiment, the composition comprises 1,1,1-trifluoroethane, the total weight content of 1,1,1-trifluoroethane being less than 5000 ppm, advantageously less than 2500 ppm, preferably less than 1000 ppm, more preferentially less than 750 ppm, based on the total weight of the composition.When 1,1,1-trifluoroethane 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 preferentially greater than 20 ppm, in particular greater than 50 ppm, more particularly greater than 100 ppm, based on the total weight of the composition.

[0067] According to a preferred embodiment, the composition comprises 1,1,1,2-tetrafluoroethane, the total weight content of 1,1,1,2-tetrafluoroethane being less than 1000 ppm, advantageously less than 750 ppm, preferably less than 500 ppm, more preferably less than 250 ppm, in particular less than 100 ppm, based on the total weight of the composition. When 1,1,1,2-tetrafluoroethane 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, more preferentially greater than 20 ppm, based on the total weight of the composition.

[0068] According to a preferred embodiment, the composition comprises hexafluorocyclobutene, the total weight content of hexafluorocyclobutene being less than 1%, advantageously less than 7500 ppm, preferably less than 5000 ppm, more preferentially less than 2500 ppm, in particular less than 1000 ppm, based on the total weight of the composition. When hexafluorocyclobutene 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 preferentially 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.

[0069] According to a preferred embodiment, the composition comprises fluoroethane, the total weight content of fluoroethane being less than 100 ppm, advantageously less than 75 ppm, preferably less than 50 ppm, more preferentially less than 25 ppm and in particular less than 10 ppm, based on the total weight of the composition. When fluoroethane is present 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.

[0070] According to a preferred embodiment, the composition comprises 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 preferentially less than 2500 ppm, in particular less than 1000 ppm, based on the total weight of the composition.When 2-chloro-1,1,1-trifluoroethane is contained in the composition, the total weight content of 2-chloro-1,1,1-trifluoroethane is more than 1 ppm, advantageously more than 5 ppm, preferably more than 10 ppm, more preferentially more than 20 ppm, in particular more than 50 ppm, and more particularly more than 100 ppm, based on the total weight of the composition.

[0071] 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%, in particular less than 1%, based on the total weight of the composition. According to a preferred 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 preferentially less than 250 ppm, in particular less than 100 ppm, based on the total weight of the composition. When 1,2-dichlorohexafluorocyclobutane is contained in the composition, the total weight content of 1,2-dichlorohexafluorocyclobutane is more than 1 ppm, advantageously more than 5 ppm, preferably more than 10 ppm, more preferentially more than 20 ppm, based on the total weight of the composition.

[0072] Working Example 25cm 3 of catalyst (0.2% palladium supported on α-alumina) was introduced into a tubular reactor (jacketed) consisting of a stainless steel tube (length 1200 mm, diameter 25 mm). The catalyst thus loaded was subsequently activated as follows: the reaction tube was placed in a tubular furnace and fed with a flow of hydrogen (0.05-0.1 mol per gram of catalyst). The catalyst bed was heated to a temperature of 200 ° C-250 ° C with a temperature gradient of 0.2 ° C / min. After this activation period, the tube was cooled to ambient temperature and then separated and subsequently installed in a hydrocracking test bench.

[0073] Four test beds, each containing a reactor prepared as described above, are used in parallel. The four beds are fed with 1 mol / h of the starting composition and 1 mol / h of hydrogen in anhydrous form. The temperature of the reactor jacket is 25° C. The contact time (calculated as the ratio of the volume of catalyst in liters: the total flow rate of reactants in standard liters / s) is approximately 22 seconds. Tests are carried out with different starting compositions. Comparative Example 1 is carried out starting from chlorotrifluoroethylene. Example 2 according to the invention is carried out starting from the chlorotrifluoroethylene used in the comparative example, to which the following compounds are added, to obtain a composition A with the proportions mentioned for each constituent: The components were 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 balance being chlorotrifluoroethylene.

[0074] Example 3 according to the invention started from the chlorotrifluoroethylene used in the comparative example, to which the following compounds were added to obtain a composition A having the stated proportions of 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.

[0075] Example 4 according to the invention started from the chlorotrifluoroethylene used in the comparative example, to which the following compounds were added to obtain a composition A having the stated proportions of 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.

[0076] The results are shown in Table 1 below: TIFF2025515083000001.tif40170

[0077] The stated productivities correspond to the sum of the productivities obtained for all four hydrocracking beds. As can be seen, starting from the composition according to the invention, the trifluoroethylene productivity is significantly improved compared to the chlorotrifluoroethylene composition without additional compounds.

Claims

1. A process for producing trifluoroethylene in a reactor containing a fixed catalyst bed comprising a catalyst, the process comprising step a) reacting a composition A comprising chlorotrifluoroethylene with hydrogen in the gas phase in the presence of the catalyst to produce a stream B comprising trifluoroethylene, wherein composition A also comprises at least one 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.

2. 2. The method according to claim 1, characterized in that the total content of the at least one additional compound C1 is less than 15% based on the total weight of composition A, preferably less than 10% based on the total weight of composition A, in particular less than 5% based on the total weight of composition A.

3. 2. The method according to claim 1, characterized in that composition A contains at least 80% by weight of chlorotrifluoroethylene, based on the total weight of composition A, preferably at least 85% by weight of chlorotrifluoroethylene, based on the total weight of composition A, in particular at least 90% by weight of chlorotrifluoroethylene, based on the total weight of composition A.

4. 2. The method according to claim 1, characterized in that said composition A also contains trifluoroethylene, preferably in a content of less than 5% by weight, based on the total weight of said composition A.

5. 2. The method of claim 1, wherein composition A also comprises at least one additional compound C2 selected from the group consisting of 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. 6. The method according to claim 5, characterized in that the weight content of said at least one additional compound C2 is less than 5%, based on the total weight of said composition A.

7. 10. The process of claim 1, wherein the catalyst comprises palladium supported on alpha-alumina.

8. 2. The process of claim 1, wherein the chlorotrifluoroethylene and hydrogen are in anhydrous form.

9. 2. The method of claim 1, further comprising a step i') of activating the catalyst by contacting the catalyst with a gas stream comprising a reducing agent, an inert gas, or a mixture thereof, wherein step i') is carried out before step a).

10. During said step i'), increasing the temperature of the catalyst bed from a temperature T1 to a temperature T2 higher than T1 with a temperature gradient of less than 0.5°C / min, or Incrementally increasing the temperature of the catalyst bed from temperature T1 to a temperature T2 that is higher than T1 10. The method according to claim 9.

11. 1. A composition comprising at least 80% by weight of 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, wherein the total weight content of the at least one additional compound is less than 15%, based on the total weight of the composition.