Method for purifying trifluoroethylene, composition comprising same, and use thereof

Abstract

The present invention relates to a method for purifying trifluoroethylene. The present invention also relates to a trifluoroethylene composition and to the use thereof as etching gas.

Description

[0001] Title: Sorting purification process

[0002]

[0003] this one and its use

[0004] Technical field of the invention

[0005] The present invention relates to a process for producing hydrofluoroolefins. In particular, the present invention relates to a process for producing trifluoroethylene (HFO-1123 or VF3) by hydrogenolysis of chlorotrifluoroethylene. The present invention also relates to a composition comprising trifluoroethylene.

[0006] Technological background of the invention

[0007] Fluorinated olefins, such as VF3, are well-known and used as monomers or comonomers in the manufacture of fluorocarbon polymers with remarkable characteristics, particularly excellent chemical stability and good thermal resistance. Trifluoroethylene is a gas under normal conditions of pressure and temperature. The main risks associated with the use of this product are its flammability, its propensity for self-polymerization when unstabilized, its explosiveness due to its chemical instability, and its presumed susceptibility to peroxidation, by analogy with other halogenated olefins. Trifluoroethylene is particularly flammable, with a lower explosive limit (LEL) of approximately 10% and an upper explosive limit (UEL) of approximately 30%.The major danger, however, is associated with the propensity of VF3 to decompose violently and explosively under certain pressure conditions in the presence of an energy source, even in the absence of oxygen.

[0008] Given the major risks mentioned above, the synthesis and storage of VF3 present particular challenges and require strict safety protocols throughout these processes. One known route for preparing trifluoroethylene uses chlorotrifluoroethylene (CTFE) and hydrogen as starting materials in the presence of a catalyst and in the gas phase.

[0009] A process for producing trifluoroethylene by hydrogenolysis of CTFE in the gas phase and in the presence of a catalyst based on a Group VIII metal at atmospheric pressure and low temperatures is known from WO 2013 / 128102. A process for producing trifluoroethylene is also known from EP 2993 213. This can be obtained by hydrogenolysis of chlorotrifluoroethylene or by thermal decomposition of chlorodifluoromethane and chlorofluoromethane.

[0010] There is therefore a need to provide a simpler and safer process for producing trifluoroethylene while maintaining high yields and selectivities.

[0011] Summary of the invention

[0012] According to a first aspect, the present invention relates to a method for purifying a gaseous mixture M comprising one or more fluorinated compounds A and one or more additional compounds B, said method comprising the following steps:

[0013] a) Supply of a gaseous mixture M comprising one or more fluorinated compounds A selected from the group consisting of trifluoroethylene and chlorotrifluoroethylene; and one or more additional compounds B selected from the group consisting of hydrogen, nitrogen, argon and helium;

[0014] b) Introduction into a column Cl of said gaseous mixture M in countercurrent to a solvent S to obtain on the one hand a liquid mixture Ml comprising said solvent S and said fluorinated compounds A and on the other hand a gaseous mixture M2 comprising said additional compounds B;

[0015] characterized in that the mass ratio between the introduction flow rate Ds of said solvent S into said column Cl and the introduction flow rate of said gas mixture M into said column Cl is between 0.1 and 100.

[0016] The present purification process improves the quality of the flow exiting the absorption column and enhances the removal of inert gases or hydrogen present in the mixture. Through the specific selection of the introduction flow rates of the various components, the solubilization of fluorinated compounds in the solvent is improved, maximizing their concentration while preventing solvent saturation. Saturating the solvent phase would promote excessive evaporation of the fluorinated compounds along with inert gases and hydrogen, resulting in a significant decrease in the overall process yield and thus a reduction in its overall efficiency. The present invention therefore enables a consistent product flow, thereby facilitating subsequent process steps.

[0017] According to a preferred embodiment, said column C1 comprises a theoretical number of plates between 1 and 20. This improves the efficiency in the absorption column and prevents excessive saturation of the solvent by the fluorinated compounds. According to a preferred embodiment, said process includes a desorption step c), carried out in a column C2, of said fluorinated compounds A from said liquid mixture M1 to form, on the one hand, a gas stream M1 comprising said fluorinated compounds A and, on the other hand, a liquid stream M1b comprising said solvent S; said step c) being carried out at a temperature, at the bottom of said column C2, lower than the boiling point of solvent S. By carrying out step c) at a temperature lower than the boiling point of solvent S, the overall efficiency of the process is improved by lower energy consumption.This implementation at a lower temperature is made possible by the improvement of the adsorption step resulting in an optimal concentration of the solvent S in fluorinated compounds A.

[0018] According to a preferred embodiment, said step c) is carried out at a temperature below 70°C at the bottom of said column C2.

[0019] According to a preferred embodiment, in column C2, the introduction flow rate Dml of the mixture Ml is between 0.9*Ds and 1.1*Ds; Ds being the introduction flow rate of solvent S into column C1. Implementing the process with similar flow rates Dml and Ds allows for the use of a closed loop between the two adsorption and desorption steps. The introduction flow rates mentioned here are mass flow rates.

[0020] According to another aspect, the present invention relates to a process for producing trifluoroethylene in a reactor equipped with a fixed catalytic bed comprising a catalyst, said process comprising the steps of:

[0021] I) reaction of chlorotrifluoroethylene with hydrogen in the presence of the catalyst and in the gas phase to produce a product stream comprising trifluoroethylene and optionally chlorotrifluoroethylene;

[0022] II) treatment of the product stream obtained in step I) to recover a gas mixture M comprising one or more fluorinated compounds A selected from the group consisting of trifluoroethylene and optionally chlorotrifluoroethylene; and one or more additional compounds B selected from the group consisting of hydrogen, nitrogen, argon and helium; and implementation of the purification process according to the present invention from said gas mixture M.

[0023] According to another aspect, the present invention relates to a composition comprising at least 99.8% by weight of trifluoroethylene and

[0024] from 1 to 1000 ppm of vinylidene fluoride,

[0025] from 1 to 200 ppm of 1,1,1-trifluoroethane (HFC-143a); from 1 to 600 ppm of chlorotrifluoroethylene based on the total weight of the composition. In another aspect, the present invention relates to a composition comprising at least 99.8% by weight of trifluoroethylene and

[0026] from 1 to 500 ppm of vinylidene fluoride,

[0027] from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0028] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. The present invention makes it possible to obtain a high-purity trifluoroethylene composition by implementing the process according to the present invention. The trifluoroethylene thus obtained can be used in applications such as fetching.

[0029] According to a preferred embodiment, said composition also comprises from 1 to 100 ppm of ethane based on the total weight of the composition.

[0030] According to a preferred embodiment, said composition comprises at least 99.9% by weight of trifluoroethylene.

[0031] According to another aspect, the present invention relates to the use of the composition according to the present invention as a pickling or etching gas.

[0032] According to another aspect, the present invention relates to a pickling or etching gas comprising at least 99.8% by weight of trifluoroethylene and

[0033] 1 to 1000 ppm, preferably 1 to 500 ppm, of vinylidene fluoride, 1 to 200 ppm, preferably 1 to 50 ppm, of 1,1,1-trifluoroethane (HFC-143a), 1 to 600 ppm, preferably 1 to 100 ppm, of chlorotrifluoroethylene, and optionally 1 ppb to 100 ppm of at least one of the compounds selected from the group consisting of nitrogen (N2), argon and helium.

[0034] According to another aspect, the present invention relates to a pickling or etching gas comprising oxygen and the composition according to the present invention.

[0035] According to a preferred embodiment, the mass content of said composition according to the present invention is between 5 and 99% based on the total weight of said pickling or etching gas.

[0036] According to a preferred embodiment, the pickling or etching gas also includes NF3 or SFg or a mixture of both.

[0037] Detailed description of the invention

[0038] Purification Method. According to a first aspect of the present invention, a method for purifying a gaseous mixture M is provided. Said gaseous mixture M comprises one or more fluorinated compounds A and one or more additional compounds B. Said one or more fluorinated compounds A are selected from the group consisting of trifluoroethylene and chlorotrifluoroethylene. Said one or more additional compounds B are selected from the group consisting of hydrogen, nitrogen, argon, and helium.

[0039] The process according to the present invention comprises a step of introducing said gas mixture M into a column Cl. In said column Cl, a solvent S is introduced counter-currently to said gas mixture M. Thus, preferably, said solvent S is introduced at the top of said column Cl and the gas mixture is introduced at a lower height than the solvent, preferably at the bottom of said column Cl.

[0040] Preferably, the mass ratio between the introduction flow rate Ds of said solvent S into said column Cl and the introduction flow rate of said gas mixture M into said column Cl is between 10 and 60. Advantageously, the mass ratio between the introduction flow rate Ds of said solvent S into said column Cl and the introduction flow rate of said gas mixture M into said column Cl is between 1 and 75, preferably between 5 and 50 or between 5 and 60, more preferably between 10 and 60 or between 10 and 25 or between 10 and 50, in particular between 13 and 50 or between 13 and 30 or between 13 and 25 or between 13 and 20 or between 20 and 50 or between 20 and 60 or between 20 and 40 or between 20 and 30 or between 13 and 60. As mentioned above, the specific selection of the mass ratio mentioned here allows for improvement the operation of said column Cl and thus increase the overall yield of the process.Below this ratio, the solvent will be saturated with fluorinated compounds A and these will tend to move to the top of the Cl column with the additional compounds B. Above this ratio, the content of fluorinated compounds A in the solvent is insufficient to guarantee proper energy efficiency and implies excessive use of the solvent.

[0041] The said column Cl preferably comprises a number of theoretical plates between 1 and 20, preferably between 1 and 15.

[0042] Step b) of the present process solubilizes said fluorinated compounds A in solvent S and thus separates them from additional compounds B such as hydrogen or inert gases (e.g., nitrogen, argon, helium). Preferably, said fluorinated compounds A have a solubility in said solvent S greater than 1 × 10⁻³ 1 g / L, advantageously greater than 2.10 1 g / L, preferably greater than 3.10 1g / L, more preferably greater than 5.10 1 g / L, in particular greater than 1 g / L, and more particularly greater than 5 g / L. The solvent S may preferably be an alcohol, a ketone, or an ester. In particular, the solvent S is an alcohol having from 1 to 4 carbon atoms. For example, but not limited to, said solvent S may be ethanol, propylene glycol, 1,3-propanediol, or ethylene glycol.

[0043] Preferably, the purification process also includes a desorption step (c). This step separates the fluorinated compounds A from the solvent S. This step is carried out in a column C2 and allows the formation of, on the one hand, a gaseous stream Mla comprising the fluorinated compounds A and, on the other hand, a liquid stream Mlb comprising the solvent S.

[0044] Said step c) is preferably carried out at a temperature, at the bottom of said column C2, below the boiling point of solvent S. Preferably, said step c) is carried out at a temperature below 70°C at the bottom of said column C2, more preferably at a temperature below 65°C, in particular at a temperature below 60°C, more particularly at a temperature below 55°C at the bottom of said column C2.

[0045] According to a preferred embodiment, in column C2, the introduction flow rate Dml of mixture Ml is between 0.9*Ds and 1.1*Ds; Ds being the introduction flow rate of solvent S into column C1. As mentioned above, implementing the process with similar or even identical flow rates Dml and Ds allows for the use of a closed loop between the two adsorption and desorption steps. Thus, the introduction flow rate Dml of mixture Ml into column C2 is between 0.92*Ds and 1.08*Ds, advantageously between 0.94*Ds and 1.06*Ds, preferably between 0.96*Ds and 1.04*Ds, and in particular between 0.98*Ds and 1.02*Ds. Implementing the adsorption and desorption steps in a closed loop allows for maintaining a stable composition of mixture Ml1. This is particularly favourable when the Mla mixture is used, after distillation, as an etching gas.For this type of application, a stable composition in terms of the content of the various constituents is preferred. This implies that the presence of impurities must be minimized, but their content must not vary between different production batches. It is therefore important to maintain operating conditions that allow for this stability of the constituents.

[0046] Triflu production process

[0047]

[0048] The purification process as described above can be integrated into a trifluoroethylene production process. This trifluoroethylene production process is carried out in a reactor equipped with a fixed catalytic bed containing a catalyst. The process comprises a step (I) of reacting chlorotrifluoroethylene with hydrogen in the presence of the catalyst and in the gas phase to produce a product stream comprising trifluoroethylene and optionally chlorotrifluoroethylene.

[0049] According to a preferred embodiment, the process according to the invention described in this application is implemented continuously.

[0050] According to a preferred embodiment, in the process described in this application, hydrogen is in anhydrous form. According to another preferred embodiment, in the process described in this application, chlorotrifluoroethylene is in anhydrous form. Implementing the processes according to the invention in the presence of hydrogen and / or anhydrous chlorotrifluoroethylene effectively increases the catalyst lifetime and thus the overall productivity of the process. The term "anhydrous" refers to a water content of less than 1000 ppm by mass, advantageously 500 ppm, preferably less than 200 ppm, and in particular less than 100 ppm based on the total weight of the compound in question.

[0051] Catalyst

[0052] Preferably, the catalyst is based on a metal from columns 8 to 10 of the periodic table of elements. In particular, the catalyst is based on a metal selected from the group consisting of Pd, Pt, Rh, and Ru; preferably palladium.

[0053] Preferably, the catalyst is supported. The support is preferably selected from the group consisting of activated carbon, an aluminum-based support, calcium carbonate, and graphite. Preferably, the support is aluminum-based. In particular, the support is alumina. The alumina may be alpha alumina. Preferably, the alumina comprises at least 90% alpha alumina. It has been observed that the conversion of the hydrogenolysis reaction is improved when the alumina is alpha alumina. Thus, the catalyst is more particularly palladium supported on alumina, advantageously palladium supported on an alumina comprising at least 90% alpha alumina, preferably palladium supported on alpha alumina.

[0054] Preferably, palladium represents from 0.01% to 5% by weight based on the total weight of the catalyst, preferably from 0.1% to 2% by weight based on the total weight of the catalyst.

[0055] In particular, said catalyst comprises from 0.01% to 5% by weight of palladium supported on alumina, preferably the alumina comprises at least 90% alpha alumina, more preferably the alumina is alpha alumina. Activation of the catalyst

[0056] The catalyst is preferably activated before its use in step a). Preferably, the catalyst activation is carried out at a high temperature and in the presence of a reducing agent. In a particular embodiment, the reducing agent is selected from the group consisting of hydrogen, carbon monoxide, nitrogen monoxide, formaldehyde, Ci-C6 alkanes, and Ci-Cio hydrohalocarbons, or a mixture thereof; preferably hydrogen or a Ci-Cio hydrohalocarbon, or a mixture thereof; in particular, hydrogen, chlorotrifluoroethylene, trifluoroethylene, chlorotrifluoroethane, trifluoroethane, or difluoroethane, or a mixture thereof. Preferably, the catalyst activation is carried out at a temperature between 100°C and 400°C, in particular at a temperature between 150°C and 350°C.In particular, catalyst activation is carried out at a temperature between 100°C and 400°C, especially at a temperature between 150°C and 350°C, in the presence of hydrogen as a reducing agent.

[0057] Catalyst regeneration

[0058] The catalyst used in this process can be regenerated. This regeneration step can be carried out within a catalytic bed temperature range of 90°C to 450°C. Preferably, the regeneration step is carried out in the presence of hydrogen. Implementing the regeneration step improves the reaction yield compared to the initial yield before regeneration.

[0059] According to a preferred embodiment, the regeneration step can be carried out at a catalytic bed temperature of 90°C to 300°C, preferably at a catalytic bed temperature of 90°C to 250°C, more preferably at 90°C to 200°C, in particular at 90°C to 175°C, and more particularly at a catalytic bed temperature of 90°C to 150°C. In particular, carrying out the regeneration step at a low temperature, for example from 90°C to 200°C or from 90°C to 175°C or from 90°C to 150°C, allows the desorption of compounds detrimental to the activity of the catalyst and / or limits phase transitions that modify the structure of the catalyst.

[0060] According to another preferred embodiment, the regeneration step can be carried out at a catalytic bed temperature above 200°C, advantageously above 230°C, preferably above 250°C, and in particular above 300°C. The regeneration step can be carried out periodically depending on the productivity or conversion obtained in step I). The regeneration step can advantageously be carried out at a catalytic bed temperature between 200°C and 300°C, preferably between 205°C and 295°C, more preferably between 210°C and 290°C, in particular between 215°C and 290°C, more particularly between 220°C and 285°C, preferably between 225°C and 280°C, and more preferably between 230°C and 280°C. Alternatively, the regeneration step can be implemented at a temperature between 300°C and 450°C, preferably between 300°C and 400°C.The regenerated catalyst can be reused in step I) of this process.

[0061] Hydrogenolysis reaction

[0062] The present invention comprises, as mentioned above, a hydrogenolysis reaction step of chlorotrifluoroethylene (CTFE) with hydrogen to produce a stream comprising trifluoroethylene. The hydrogenolysis step is carried out in the presence of a catalyst and in the gas phase. Preferably, the hydrogenolysis step is carried out in the presence of a pre-activated catalyst and in the gas phase. The hydrogenolysis step consists of simultaneously introducing hydrogen, CTFE, and optionally an inert gas, such as nitrogen, in the gas phase and in the presence of said catalyst, preferably activated.

[0063] Preferably, said step I) is carried out at a fixed catalytic bed temperature between 50°C and 250°C. Said step a) can be carried out at a fixed catalytic bed temperature 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. The said step I) can also be implemented at a fixed catalytic bed temperature 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.The said step I) can also be implemented at a fixed catalytic bed temperature between 60°C and 240°C, advantageously between 70°C and 230°C, preferably between 80°C and 220°C, more preferably between 90°C and 210°C, in particular between 100°C and 200°C, more particularly between 100°C and 180°C, preferably between 100°C and 160°C, particularly preferably between 120°C and 160°C.

[0064] The H2 / CTFE molar ratio is between 0.5 / 1 and 2 / 1 and preferably between 1 / 1 and 1.2 / 1. If an inert gas such as nitrogen is present in step I), the nitrogen / H2 molar ratio is between 0 / 1 and 2 / 1 and preferably between 0 / 1 and 1 / 1. Step I) is preferably carried out at a pressure of 0.05 MPa to 1.1 MPa, more preferably from 0.05 MPa to 0.5 MPa, in particular at atmospheric pressure.

[0065] The contact time, calculated as the ratio between the volume, in liters, of catalyst and the total flow rate of the gas mixture, in normal liters per second, at the reactor inlet, 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.

[0066] The hydrogenolysis step (step I) of the present process results in the production of a product stream comprising trifluoroethylene. This product stream may also include unreacted hydrogen and unreacted chlorotrifluoroethylene. The product stream may also include HCl or HF, or a mixture of both.

[0067] Processing of the stream from step I)

[0068] The stream from step I) can be treated to recover a gas mixture M comprising one or more fluorinated compounds A selected from the group consisting of trifluoroethylene and optionally chlorotrifluoroethylene; and one or more additional compounds B selected from the group consisting of hydrogen, nitrogen, argon, and helium. The purification process according to the present invention can then be carried out using said gas mixture M.

[0069] Treatment step II) of this process may include the following steps:

[0070] i) Removal of HF and / or HCl from said product stream obtained in step I) to form a gaseous mixture;

[0071] ii) Drying of the gas mixture from step i) to form said gas mixture M.

[0072] The paragraph below details steps i) to ii).

[0073] The product stream from step I) is recovered from the reactor outlet in gaseous form. Preferably, at the outlet of the hydrogenolysis reactor, the product stream is first treated to remove HCl and HF. The product stream is passed through water in a scrubbing column and then through a wash with a dilute base such as NaOH or KOH. The remaining gaseous mixture, consisting of unconverted reactants (H2 and CTFE), dilution nitrogen (if present), trifluoroethylene, and the additional compounds mentioned above, is directed to a dryer to remove traces of wash water. Drying can be carried out using products such as sodium or magnesium calcium sulfate, calcium chloride, potassium carbonate, silica gel, or zeolites. In one embodiment, a molecular sieve (zeolite) such as siliporite is used for drying.The gas mixture thus dried corresponds to the gas mixture M and is subjected to the purification process according to the present invention to obtain a gas stream Mla comprising said fluorinated compounds A.

[0074] The said Mla stream thus obtained can be distilled to form and recover an M2a stream comprising trifluoroethylene and one or more additional compound(s) selected from the group consisting of 1,1-difluoroethylene (HFO-1132a), 1,1,1-trifluoroethane (HFC-143a), chlorotrifluoroethylene and possibly ethane.

[0075] According to a preferred embodiment, the distillation step of said Mla stream is carried out at a pressure below 3 bara, preferably at a pressure between 0.5 and 3 bara, and in particular at a pressure between 0.9 and 2 bara. Performing distillation at a pressure below 3 bara makes the process safer, given the explosive nature of trifluoroethylene above 3 bara.

[0076] Preferably, the distillation step of said stream Mla is carried out in a distillation column comprising a structured packing. It has been observed that a structured packing allows for a more efficient distillation step. Said structured packing may be made of a metallic material.

[0077] The M2a stream is preferably collected at the top of the distillation column. Before collection, the M2a stream may optionally be partially condensed at the top of the distillation column. When partial condensation is implemented, the M2a stream is heated to a temperature of -50°C to -70°C. The temperature is adjusted according to the pressure applied in step c). Partial condensation improves distillation efficiency by limiting the content of additional compounds in the M2a stream.

[0078] Distillation of the M1 stream also results in the formation of an M2b stream comprising chlorotrifluoroethylene, preferably recovered from the bottom of the distillation column. This M2b stream can be recycled in step a) after optional purification treatment.

[0079] Composition and use

[0080] The present invention enables the preparation of a high-purity trifluoroethylene composition. Thus, the present invention provides a composition comprising at least 99.8% by weight of trifluoroethylene.

[0081] More specifically, said composition comprises at least 99.8% by weight of trifluoroethylene and 1 to 1000 ppm of vinylidene fluoride,

[0082] from 1 to 200 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0083] from 1 to 600 ppm of chlorotrifluoroethylene based on the total weight of the composition. More specifically, said composition comprises at least 99.8% by weight of trifluoroethylene and

[0084] from 1 to 750 ppm of vinylidene fluoride,

[0085] from 1 to 100 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0086] from 1 to 250 ppm of chlorotrifluoroethylene based on the total weight of the composition. More specifically, said composition comprises at least 99.8% by weight of trifluoroethylene and

[0087] from 1 to 500 ppm of vinylidene fluoride,

[0088] from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0089] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. Preferably, said composition comprises at least 99.8% by weight of trifluoroethylene and from 1 to 400 ppm of vinylidene fluoride,

[0090] from 1 to 40 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0091] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. In particular, said composition comprises at least 99.8% by weight of trifluoroethylene and from 1 to 400 ppm of vinylidene fluoride,

[0092] from 1 to 30 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0093] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. Said composition may also include from 1 to 100 ppm of ethane based on the total weight of the composition.

[0094] According to a preferred embodiment, said composition comprises at least 99.9% by weight of trifluoroethylene. Thus, said composition comprises at least 99.9% by weight of trifluoroethylene and

[0095] from 1 to 500 ppm of vinylidene fluoride,

[0096] from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0097] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. Preferably, said composition comprises at least 99.9% by weight of trifluoroethylene and from 1 to 400 ppm of vinylidene fluoride,

[0098] from 1 to 40 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0099] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. In particular, said composition comprises at least 99.9% by weight of trifluoroethylene and from 1 to 400 ppm of vinylidene fluoride,

[0100] from 1 to 30 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0101] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. As mentioned above, the present invention also relates to the use of the composition according to the present invention as a stripping or etching gas. The present invention relates to trifluoroethylene compositions useful for removing surface deposits in CVD chambers, and to methods for removing surface deposits from the inside of a chemical vapor deposition chamber using an activated gas mixture created by activating a gas mixture in the chamber or in a remote chamber, wherein the gas mixture comprises a trifluoroethylene composition according to the present invention.

[0102] Surface deposits removed with the composition according to the present invention include materials commonly deposited by chemical vapor deposition (CVD) or plasma-enhanced chemical vapor deposition (PECVD) or similar processes. Such materials include nitrogen-containing deposits such as, without limitation, silicon nitride, silicon oxynitride, silicon carbonitride (SiCN), silicon boronitride (SiBN), and metal nitrides, such as tungsten nitride, titanium nitride, or tantalum nitride. In one embodiment of the invention, a preferred surface deposit is silicon nitride. The surface deposits are removed from inside a processing chamber used in the manufacture of electronic devices. Such a processing chamber could be a CVD chamber or a PECVD chamber.Other embodiments of the invention include, but are not limited to, the removal of metal surface deposits, the cleaning of plasma etching chambers, and the removal of nitrogen-containing thin films from a disc (i.e., wafer). In one embodiment, the gas is used in an etching application.

[0103] The process of the present invention involves an activation step in which a cleaning gas mixture is activated in a remote chamber. Activation can be achieved by any means that dissociates a significant fraction of the feed gas, such as radio frequency (RF) energy, direct current (DC) energy, laser illumination, and microwave energy. One embodiment of the present invention is the use of transformer-coupled, induction-coupled, lower-frequency RF power sources in which the plasma has a toroidal configuration and acts as the transformer secondary.The use of low-frequency RF power enables the use of magnetic cores that improve inductive coupling compared to capacitive coupling; this allows for more efficient energy transfer to the plasma without excessive ion bombardment, which limits the lifetime of the internal components of the remote plasma source chamber. The typical RF power used in the present invention has a frequency below 1000 kHz. In another embodiment of the present invention, the power source is a microwave plasma source, either inductively or capacitively coupled. In yet another embodiment of the invention, the gas is activated using a glow discharge. The activation of the gas mixture uses sufficient power for a sufficient duration to form an activated gas mixture. In one embodiment of the invention, the activated gas mixture has a neutral temperature of at least approximately 1000–3000 K.The neutral temperature of the resulting plasma depends on the power and residence time of the gas mixture in the remote chamber. Under certain conditions and power input settings, the neutral temperature will be higher with longer residence times. In one embodiment of the invention, a preferred neutral temperature of the activated gas mixture is greater than approximately 3000 K.

[0104] Thus, the present invention provides a stripping or etching gas comprising at least 99.8% by weight of trifluoroethylene and

[0105] from 1 to 1000 ppm of vinylidene fluoride,

[0106] from 1 to 200 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0107] from 1 to 600 ppm of chlorotrifluoroethylene based on the total weight of the composition. Thus, the present invention provides a etching gas comprising at least 99.8% by weight of trifluoroethylene and

[0108] from 1 to 750 ppm of vinylidene fluoride,

[0109] from 1 to 100 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0110] from 1 to 250 ppm of chlorotrifluoroethylene based on the total weight of the composition. Thus, the present invention provides a etching gas comprising at least 99.8% by weight of trifluoroethylene and

[0111] from 1 to 500 ppm of vinylidene fluoride,

[0112] from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0113] from 1 to 100 ppm of chlorotrifluoroethylene.

[0114] Preferably, said pickling or etching gas comprises at least 99.8% by weight of trifluoroethylene and 1 to 400 ppm of vinylidene fluoride,

[0115] from 1 to 40 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0116] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. In particular, said pickling or etching gas comprises at least 99.8% by weight of trifluoroethylene and

[0117] from 1 to 400 ppm of vinylidene fluoride,

[0118] from 1 to 30 ppm of 1,1,1-trifluoroethane (HFC-143a);

[0119] from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition. The etching or cleaning gas may optionally include traces of inert gases. The etching gas may comprise at least 99.8% by weight of trifluoroethylene and

[0120] from 1 to 500 ppm of vinylidene fluoride,

[0121] from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0122] from 1 to 100 ppm of chlorotrifluoroethylene, and

[0123] optionally from 1 ppb to 100 ppm of at least one of the selected compounds from the group consisting of nitrogen (N2), argon and helium.

[0124] Advantageously, the pickling or etching gas may comprise at least 99.8% by weight of trifluoroethylene and

[0125] from 1 to 400 ppm of vinylidene fluoride,

[0126] from 1 to 40 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0127] from 1 to 100 ppm of chlorotrifluoroethylene, and

[0128] optionally from 1 ppb to 100 ppm of at least one of the selected compounds from the group consisting of nitrogen (N2), argon and helium.

[0129] Preferably, the pickling or etching gas may comprise at least 99.8% by weight of trifluoroethylene and

[0130] from 1 to 400 ppm of vinylidene fluoride,

[0131] from 1 to 30 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0132] from 1 to 100 ppm of chlorotrifluoroethylene, and

[0133] optionally from 1 ppb to 100 ppm of at least one of the selected compounds from the group consisting of nitrogen (N2), argon and helium.

[0134] According to a preferred embodiment, said etching gas may comprise at least 99.9% trifluoroethylene. Thus, the etching or etching gas may comprise at least 99.9% by weight trifluoroethylene and

[0135] from 1 to 500 ppm of vinylidene fluoride, from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0136] from 1 to 100 ppm of chlorotrifluoroethylene, and

[0137] optionally from 1 ppb to 100 ppm of at least one of the selected compounds from the group consisting of nitrogen (N2), argon and helium.

[0138] Advantageously, the pickling or etching gas may comprise at least 99.9% by weight of trifluoroethylene and

[0139] from 1 to 400 ppm of vinylidene fluoride,

[0140] from 1 to 40 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0141] from 1 to 100 ppm of chlorotrifluoroethylene, and

[0142] optionally from 1 ppb to 100 ppm of at least one of the selected compounds from the group consisting of nitrogen (N2), argon and helium.

[0143] Preferably, the pickling or etching gas may comprise at least 99.9% by weight of trifluoroethylene and

[0144] from 1 to 400 ppm of vinylidene fluoride,

[0145] from 1 to 30 ppm of 1,1,1-trifluoroethane (HFC-143a),

[0146] from 1 to 100 ppm of chlorotrifluoroethylene, and

[0147] optionally from 1 ppb to 100 ppm of at least one of the selected compounds from the group consisting of nitrogen (N2), argon and helium.

[0148] The etching or stripping gas may, in addition to the trifluoroethylene composition according to the present invention, comprise an oxygen source, a nitrogen source, or an inorganic fluorine source, including NF3 and SFg. The gas mixture that is activated to form the activated gas mixture of the invention may further comprise a carrier gas. Examples of suitable carrier gases include noble gases such as argon and helium. The temperature in the treatment chamber during the removal of surface deposits may be from approximately 50°C to approximately 150°C. The total pressure during the activation step may be between approximately 0.5 torr (0.667 x 10⁻³) and 0.667 x 10⁻³. -3 bar) and approximately 20 torr (0.02667 bar). The total pressure in the treatment chamber can be between approximately 0.5 torr (0.667 x 10 -3 bar) and approximately 15 torr (0.01999 bar).

[0149] Thus, according to another preferred embodiment, the etching or cleaning gas may also comprise oxygen, trifluoroethylene, vinylidene fluoride, 1,1,1-trifluoroethane, and chlorotrifluoroethylene. In this embodiment, the etching or cleaning gas may comprise a carrier gas such as helium, argon, or nitrogen. The etching or cleaning gas may also comprise NF3 or SFg, or a mixture of both. In this embodiment, the total mass content of the following compounds—trifluoroethylene, vinylidene fluoride, 1,1,1-trifluoroethane, and chlorotrifluoroethylene, and optionally ethane—is between 5% and 99% based on the total weight of said etching or cleaning gas.

[0150] Example 1 (invention)

[0151] In a tubular reactor consisting of a stainless steel tube 1200 mm long and 25 mm in diameter, and equipped with a double jacket, 25 cm³ was introduced 3of catalyst (0.2% palladium supported on alpha alumina). The charged catalyst was then activated as follows: the reaction tube was placed in a tubular furnace and fed with a hydrogen flow (0.05 to 0.1 moles per gram of catalyst). The catalytic bed was then heated to a temperature of 200°C to 250°C with a temperature gradient of 0.2°C / min. After this activation period, the tube was cooled to room temperature and then insulated for installation on a hydrogenolysis test bench. The reactor was fed with 1 mol / h of CTFE and 1 mol / h of anhydrous hydrogen. It is also possible to feed the reactors with an inert gas (here, nitrogen). The temperature of the catalytic bed was maintained between 100°C and 130°C. The contact time, calculated as the ratio between the volume in liters of catalyst and the sum of the flow rates of the reactants in normal liters per second, was on the order of 22 seconds.

[0152] The gases produced by the reaction are introduced into a hydrochloric acid removal column consisting of a 355 mm long, 40 mm diameter fluoropolymer tube fitted with 4 mm diameter, 5 mm long fluoropolymer rings. The removal column is continuously fed with water at a flow rate of 10 L / h. The hydrochloric acid-laden water is continuously removed at the bottom of the column. The reaction products, thus freed of hydrochloric acids, are then directed to a drying section consisting of two 800 mm long, 50 mm diameter stainless steel tubes connected in series and filled with Siliporite 3A molecular sieve.

[0153] The dried gases are then directed to an absorption column containing a structured packing equivalent to 10 theoretical plates. The absorption column is fed at the top with ethanol. The mass ratio between the ethanol feed rate and the dried gas feed rate is 14.3. The double jacket of the absorption column is cooled by a heat transfer fluid at -25°C. Hydrogen and inert gases exit at the top of the absorption column, while the reaction products, dissolved in ethanol, exit at the bottom and are directed to a desorption section consisting of a column with a structured packing. The temperature at the bottom of the desorption column is 50°C.The organic products from the reaction are evaporated and leave the desorption section through the column head, while the ethanol, now free of organics, is pumped to the absorption column head. The mixture of organic products from the desorption section is then directed to a distillation column containing either Sulzer EX or Sulzer DX structured packing. The rectification section is equivalent to 12 to 13 theoretical stages, and the exhaustion section is equivalent to one theoretical stage. The resulting composition comprises 99.90% trifluoroethylene (TrFE), 306 ppm of 1,1-difluoroethylene, 10 ppm of 1,1,1-trifluoroethane, and 42 ppm of chlorotrifluoroethylene.

[0154] Example 2 (comparative)

[0155] Example 1 is reproduced except that the treatment of the dried gases is carried out at a ratio between the ethanol introduction flow rate and the dried gas introduction flow rate of 0.

[0156] Example 3 (invention)

[0157] Example 1 is reproduced except that the treatment of the dried gases is carried out at a ratio of ethanol introduction flow rate to dried gas introduction flow rate of 25. The resulting composition comprises 99.8% trifluoroethylene (TrFE), 664 ppm of 1,1-difluoroethylene, 6 ppm of 1,1,1-trifluoroethane, and 276 ppm of chlorotrifluoroethylene.

[0158] [Table 1]

[0159]

[0160] * 1,1-Difluoroethylene, chlorotrifluoroethylene, and 1,1,1-trifluoroethane. The present invention demonstrates that the specific mass ratio between the ethanol introduction flow rate and the gas introduction flow rate allows for improved productivity and a lower content of secondary compounds in the trifluoroethylene. Implementing a process with too low a ratio will result in an excessive amount of inert gas and secondary compounds in the distillation column, preventing efficient purification of the trifluoroethylene. Implementing a process with too high a ratio requires the use of large quantities of solvent, thus impacting the overall process cost. The composition according to the invention is particularly suitable for use as a pickling or etching gas.

Claims

Demands 1. A process for purifying a gaseous mixture M comprising one or more fluorinated compounds A and one or more additional compounds B, said process comprising the following steps: a) Supply of a gaseous mixture M comprising one or more fluorinated compounds A selected from the group consisting of trifluoroethylene and chlorotrifluoroethylene; and one or more additional compounds B selected from the group consisting of hydrogen, nitrogen, argon and helium; b) Introduction into a column Cl of said gaseous mixture M in countercurrent to a solvent S to obtain on the one hand a liquid mixture Ml comprising said solvent S and said fluorinated compounds A and on the other hand a gaseous mixture M2 comprising said additional compounds B; characterized in that the mass ratio between the introduction flow rate Ds of said solvent S into said column Cl and the introduction flow rate of said gas mixture M into said column Cl is between 0.1 and 100.

2. Purification process according to the preceding claim characterized in that said column Cl comprises a number of theoretical plates between 1 and 10.

3. A purification process according to any one of the preceding claims characterized in that said process comprises a step c) of desorption, carried out in a column C2, of said fluorinated compounds A of said liquid mixture Ml to form on the one hand a gaseous stream Mla comprising said fluorinated compounds A and on the other hand a liquid stream Mlb comprising said solvent S; said step c) being carried out at a temperature, at the bottom of said column C2, lower than the boiling point of solvent S.

4. Purification process according to the preceding claim characterized in that said step c) is carried out at a temperature below 70°C at the bottom of said column C2.

5. Purification process according to any one of the preceding claims 3 or 4 characterized in that, in said column C2, the introduction flow rate Dml of the mixtureMl is between 0.9*Ds and l.l*Ds; Ds being the introduction flow rate of said solvent S into said column Cl.

6. A process for producing trifluoroethylene in a reactor equipped with a fixed catalytic bed comprising a catalyst, said process comprising the steps of: I) reaction of chlorotrifluoroethylene with hydrogen in the presence of the catalyst and in the gas phase to produce a product stream comprising trifluoroethylene and optionally chlorotrifluoroethylene; II) treatment of the product stream obtained in step I) to recover a gas mixture M comprising one or more fluorinated compounds A selected from the group consisting of trifluoroethylene and optionally chlorotrifluoroethylene; and one or more additional compounds B selected from the group consisting of hydrogen, nitrogen, argon and helium; and implementation of the purification process according to any one of the preceding claims from said gas mixture M.

7. Composition comprising at least 99.8% by weight of trifluoroethylene and from 1 to 1000 ppm of vinylidene fluoride, from 1 to 200 ppm of 1,1,1-trifluoroethane (HFC-143a); from 1 to 600 ppm of chlorotrifluoroethylene based on the total weight of the composition.

8. Composition according to the preceding claim comprising at least 99.8% by weight of trifluoroethylene and from 1 to 500 ppm of vinylidene fluoride, from 1 to 50 ppm of 1,1,1-trifluoroethane (HFC-143a); from 1 to 100 ppm of chlorotrifluoroethylene based on the total weight of the composition.

9. Composition according to any one of the preceding claims 7 or 8 characterized in that it also comprises from 1 to 100 ppm of ethane on a weight-for-weight basis of the total composition.

10. Composition according to any one of the preceding claims 8 or 9 characterized in that it comprises at least 99.9% by weight of trifluoroethylene.

11. Use of the composition according to any one of claims 7 to 10 as a pickling or etching gas.

12. Pickling or etching gas comprising at least 99.8% by weight of trifluoroethylene and 1 to 1000 ppm, preferably 1 to 500 ppm, of vinylidene fluoride, 1 to 200 ppm, preferably 1 to 50 ppm, of 1,1,1-trifluoroethane (HFC-143a), 1 to 600 ppm, preferably 1 to 100 ppm, of chlorotrifluoroethylene, and optionally 1 ppb to 100 ppm of at least one of the compounds selected from the group consisting of nitrogen (N2), argon and helium.

13. Pickling or etching gas comprising oxygen and the composition according to any one of the preceding claims 7 to 10.

14. Pickling or etching gas according to claim 12 or 13 characterized in that the mass content of said composition according to any one of the preceding claims 7 to 10 is between 5 and 99% on the basis of the total weight of said pickling or etching gas.

15. Pickling or etching gas according to any one of the preceding claims 12 to 14 characterized in that it also comprises NF3 or SFg or a mixture of both.