Method for producing carbon tetrafluoroethylene using fluoroform as a raw material

Abstract

This invention provides a method for producing carbon tetrafluoride using fluoroform as a raw material, and a pyrolysis and purification apparatus, which relate to the technical field of fluoroform resource utilization. Fluoroform is injected into a thermal plasma reactor and subjected to a pyrolysis reaction at 1500-5000 K to obtain carbon tetrafluoride. Compared to conventional tubular furnace pyrolysis or high-temperature muffle furnace pyrolysis, the thermal plasma reactor used in this invention relies on the synergistic effect of highly active electrons and heavy particles at high temperatures, resulting in significant electron excitation. This allows for efficient cleavage and directional reorganization of chemical bonds in fluoroform molecules without the use of catalysts or fluorine gas, resulting in high fluoroform conversion, high carbon tetrafluoride selectivity, and low energy consumption. Furthermore, the method provided by this invention has a short reaction time, large throughput, is safe and controllable, and the pyrolysis reaction products have a simple composition and are easy to separate and purify. It also consumes low cost and energy, making it suitable for industrial continuous scale-up production.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of fluoroform, and particularly to a method for producing carbon tetrafluoride using fluoroform as a raw material. law It relates to.

[0002] Cross-reference to related applications This application claims the priority of a Chinese patent application with the application number CN202310984672.X, filed with the China Patent Office on August 7, 2023, and the invention name "Method for Producing Carbon Tetrafluoride Using Fluoroform as a Raw Material", and all its contents are incorporated into this application by reference.

Background Art

[0003] Fluoroform (R23) is an inevitable by-product in the manufacturing processes such as when producing difluorochloromethane (HCFC-22) by reacting hydrogen fluoride and chloroform, or when producing tetrafluoroethylene by pyrolyzing HCFC-22. Its application fields are relatively narrow, and it is difficult to use as a chemical industrial raw material for manufacturing other products. It is only used for specific applications such as fire extinguishing agents and semiconductor etching agents. At the same time, although R23 itself does not destroy the ozone layer, it causes a serious greenhouse effect. Its global warming potential (GWP) is 14,800 times that of CO2, and it can exist stably in the atmosphere for 264 years. The concentration of R23 in the atmosphere has been steadily increasing at an annual rate of 5% over the past few decades, causing a serious ecological danger. Currently, the main treatment method for R23 is incineration treatment. By thoroughly incinerating R23 and thermally decomposing it into substances such as HF and CO2, the adverse effects on the environment are avoided. However, due to the very stability of R23 itself, thermal decomposition is difficult even under combustion conditions, and extremely harsh reaction conditions are often required for incineration treatment, which tends to increase the treatment cost and equipment investment, and valuable substances cannot be recovered. If the generated HF is not recovered, post-treatment of fluoride salts also needs to be considered, resulting in a low utilization value of the product. Therefore, it is urgent to develop a new method for resource treatment of R23 that can obtain clean, efficient, and high-value-added products.

[0004] Carbon tetrafluoride (R14) is the most widely used plasma etching gas in the microelectronics industry and has broad development potential. Currently, R14 is synthesized industrially mainly using hydrofluoromethane fluorination, chlorofluoromethane fluorination, and direct fluorination of carbon and fluorine gas. However, the phased banning of CFCs and HCFCs has limited the supply of raw materials for chlorofluoromethane fluorination, and both direct fluorination of carbon and fluorine gas and hydrofluoromethane fluorination have problems such as violent exothermic reactions, potential explosion hazards, high equipment requirements, and complex product compositions. Therefore, it is crucial to find a new method for efficiently preparing R14 that is safe, controllable, and suitable for industrial scale-up. [Overview of the project] [Problems that the invention aims to solve]

[0005] In view of this, the present invention relates to a method for producing carbon tetrafluoroethylene using fluoroform as a raw material. law The objective is to provide a method that offers a high conversion rate of fluoroform, high selectivity for carbon tetrafluoride, large processing capacity, is safe and controllable, and is suitable for continuous industrial scale-up production. [Means for solving the problem]

[0006] To achieve the above-mentioned objectives of the present invention, the present invention provides the following technical solutions. This invention provides a method for producing tetrafluorocarbon using fluoroform as a raw material. The process includes the step of injecting fluoroform into a thermal plasma reactor to carry out a thermal decomposition reaction to obtain carbon tetrafluoride, wherein the temperature of the thermal decomposition reaction is 1500 to 5000 K.

[0007] Preferably, the fluoroform is 0.5 to 1000 Nm 3 It has a flow rate of / h.

[0008] Preferably, the thermal plasma reactor includes an RF thermal plasma reactor, a microwave thermal plasma reactor, or an arc thermal plasma reactor.

[0009] Preferably, the thermal decomposition reaction time is on the millisecond level.

[0010] Preferably, the process includes further purification of the pyrolysis gas obtained from the pyrolysis reaction, and the purification includes: The pyrolysis gas is cooled and then separated into gas and solid to obtain a carbon black-removed pyrolysis gas, and the cooling includes cooling to 600-1000K by a first partition-type heat exchanger, followed by cooling to 298-400K by a second partition-type heat exchanger, and the cooling medium for the cooling by the second partition-type heat exchanger is fluoroform. The carbon black removal pyrolysis gas is washed with water-alkaline to obtain a hydrogen fluoride removal pyrolysis gas, The process includes drying the hydrogen fluoride removal pyrolysis gas, then rectifying it to obtain high-purity carbon tetrafluoride and a rectification residue, and reusing the rectification residue in the pyrolysis reaction.

[0011] Preferably, the cooling medium for the cooling by the first partition-type heat exchange is water or a freezing liquid.

[0012] Preferably, the water-alkaline wash includes water wash and / or alkaline aqueous solution wash, wherein the mass concentration of alkali in the alkaline aqueous solution is 40% or less, and the alkali includes sodium hydroxide and / or potassium hydroxide.

[0013] Preferably, the gas-solid separation is carried out using a gas-solid separation apparatus, which includes a single-stage gas-solid separation apparatus or a multi-stage gas-solid separation apparatus.

[0014] Preferably, the gas-solid separation device includes a filter or a cyclone separator. [Effects of the Invention]

[0015] The present invention provides a method for producing tetrafluorocarbon using fluoroform as a raw material, comprising the step of injecting fluoroform into a thermal plasma reactor to carry out a thermal decomposition reaction to obtain tetrafluorocarbon, wherein the temperature of the thermal decomposition reaction is 1500 to 5000 K. Compared to conventional tubular furnace pyrolysis or muffle furnace high-temperature pyrolysis, the thermal plasma reactor used in the present invention can rely on the synergistic effect of highly active electrons and heavy particles at high temperatures, possessing a remarkable electron excitation effect. Without the use of catalysts or fluorine gas, it can achieve efficient cleavage of chemical bonds and directional rearrangement of fluoroform molecules, resulting in a high conversion rate of fluoroform, high selectivity for tetrafluorocarbon, short reaction time, large processing capacity, and a safe and controllable process. The products of the pyrolysis reaction have a simple composition, are easy to separate and purify, and are low-cost and energy-efficient, making them suitable for industrial continuous scale-up production. This enables the resource recovery and utilization of fluoroform at low cost and with low energy consumption. In particular, it is suitable for the resource recovery of fluoroform produced as a by-product in processes such as the production of difluorochloromethane or the pyrolysis of difluorochloromethane to produce tetrafluoroethylene. By avoiding the greenhouse effect from direct emissions of fluoroform and the waste of resources from incineration, and by producing high value-added tetrafluorocarbon products, it brings significant economic and social benefits. Furthermore, since the present invention does not use any catalyst, problems such as catalyst coking, deactivation, carbonization, and clogging of equipment under high-temperature conditions are avoided, further improving the yield of carbon tetrafluoride and the safety of the reaction.

[0016] Furthermore, the present invention utilizes a method of cooling to 600-1000K by a first partition-type heat exchanger and then cooling to 298-400K by a second partition-type heat exchanger to preheat fluoroform using the waste heat cooled by the second partition-type heat exchanger. This avoids the reaction of fluoroform with the high-temperature waste heat cooled by the first partition-type heat exchanger to produce byproducts, while also making full use of the waste heat cooled by the second partition-type heat exchanger, thereby significantly reducing energy consumption and production costs. [Brief explanation of the drawing]

[0017] [Figure 1] It is a diagram of a pyrolysis purification apparatus used when producing carbon tetrafluoride using fluoroform as a raw material.

Embodiments for Carrying Out the Invention

[0018] The present invention provides a method for producing carbon tetrafluoride using fluoroform as a raw material, including the step of injecting fluoroform into a thermal plasma reactor to carry out a pyrolysis reaction to obtain carbon tetrafluoride, wherein the temperature of the pyrolysis reaction is 1500 - 5000K.

[0019] In the present invention, the flow rate of the fluoroform is preferably 0.5 - 1000 Nm 3 / h, more preferably 1 - 800 Nm 3 / h, and even more preferably 3 - 600 Nm 3 / h. The present invention has no particular limitation on the source of the fluoroform. The fluoroform may be fluoroform generated in the manufacturing process of difluorochloromethane well-known to those skilled in the art, fluoroform generated in the manufacturing process of tetrafluoroethylene by pyrolysis of difluorochloromethane, a low-temperature refrigerant mainly composed of fluoroform recovered from a factory, or fluoroform recovered from other process routes. The purity of the fluoroform is preferably 90% or more. The manufacturing method provided by the present invention can realize the resource utilization of by-produced fluoroform in the manufacturing process of difluorochloromethane or in the process of producing tetrafluoroethylene by pyrolyzing difluorochloromethane and fluoroform from other sources.

[0020] In the present invention, the thermal plasma reactor preferably includes an RF thermal plasma reactor, a microwave thermal plasma reactor, or an arc thermal plasma reactor. The arc thermal plasma reactor is preferably a DC arc plasma reactor, and more preferably a magnetically rotated arc thermal plasma reactor. The DC arc plasma reactor used in the present invention has high mass transfer efficiency and heat transfer efficiency, uniform residence time, and is easy to control. The present invention uses a thermal plasma reactor to thermally decompose chloroform and does not require a carrier gas for dilution or auxiliary thermal decomposition. Therefore, the thermally decomposed gas obtained by the thermal decomposition reaction has a simple composition, and the subsequent purification process is further simplified.

[0021] In the present invention, the temperature of the thermal decomposition reaction is preferably 2000 - 4500 K, more preferably 2500 - 4000 K, and even more preferably 3000 - 3500 K. In the present invention, in the thermal decomposition reaction process, chloroform is thermally decomposed in the presence of thermal plasma to produce carbon tetrafluoride, a small amount of carbon black, and hydrogen fluoride. Also, a small amount of chloroform did not undergo a thermal decomposition reaction.

[0022] After the thermal decomposition reaction, the present invention preferably further includes purifying the thermally decomposed gas obtained by the thermal decomposition reaction. The purification includes After cooling the thermally decomposed gas, performing gas-solid separation to obtain a carbon black-removed thermally decomposed gas. The cooling includes cooling to 600 - 1000 K by a first partition type heat exchange and then cooling to 298 - 400 K by a second partition type heat exchange. The cooling medium for the cooling by the second partition type heat exchange is chloroform, and washing the carbon black-removed thermally decomposed gas with water-alkali to obtain a hydrogen fluoride-removed thermally decomposed gas, and after drying the hydrogen fluoride-removed thermally decomposed gas, performing rectification to obtain high purity carbon tetrafluoride and rectification residues respectively, and recycling the rectification residues to the thermal decomposition reaction.

[0023] In this invention, a pyrolysis gas is cooled and then separated into gas and solid to obtain a carbon black-removed pyrolysis gas. The cooling includes cooling to 600-1000K by a first partition-type heat exchanger, followed by cooling to 298-400K by a second partition-type heat exchanger. In this invention, the cooling medium for cooling by the first partition-type heat exchanger is preferably water or a freezing liquid. In this invention, there is no particular requirement for the specific type of freezing liquid, and any freezing liquid with a cooling function known to those skilled in the art may be used, specifically, for example, ethylene glycol. In this invention, the temperature after cooling is preferably 298K, 350K, or 400K. In this invention, the cooling medium for cooling by the second partition-type heat exchange is fluoroform. That is, the waste heat cooled by the second partition-type heat exchange is used for preheating and cooling the fluoroform, and the resulting preheated fluoroform is injected into a thermal plasma reactor to cause a thermal decomposition reaction. Assuming that fluoroform does not cause side reactions, the heat of the thermal decomposition gas can be fully utilized, further reducing energy consumption and manufacturing costs.

[0024] In the present invention, the gas-solid separation is preferably carried out using a gas-solid separation apparatus, which preferably includes a single-stage gas-solid separation apparatus or a multi-stage gas-solid separation apparatus, which preferably includes a filter or a cyclone separator, and the purpose of the gas-solid separation is to remove carbon black. In the present invention, the multi-stage gas-solid separation apparatus is preferably a two-stage gas-solid separation apparatus, the first-stage gas-solid separation apparatus in the two-stage gas-solid separation apparatus is preferably a cyclone separator, which is used to capture carbon black particles with a particle size of 5 μm or more (larger carbon black particles or aggregates of small carbon black particles), and the second-stage gas-solid separation apparatus in the two-stage gas-solid separation apparatus is preferably a filter, which is used to capture carbon black with a particle size of less than 5 μm.

[0025] The gas-solid separation device preferably includes a filter or a cyclone separator, and the purpose of the gas-solid separation is to remove carbon black.

[0026] After obtaining a carbon black removal pyrolysis gas, the present invention washes the carbon black removal pyrolysis gas with water and alkali to obtain a hydrogen fluoride removal pyrolysis gas. In the present invention, the water-alkaline washing preferably includes washing with water and / or washing with an alkaline aqueous solution, the mass concentration of alkali in the alkaline aqueous solution is preferably 40% or less, more preferably 15-40%, the alkali preferably includes sodium hydroxide and / or potassium hydroxide, more preferably potassium hydroxide, and the purpose of the washing is to remove hydrogen fluoride.

[0027] After obtaining a hydrogen fluoride removal pyrolysis gas, the present invention dries the hydrogen fluoride removal pyrolysis gas, then rectifies it to obtain high-purity carbon tetrafluoride and a rectification residue, and reuses the rectification residue in the pyrolysis reaction. In the present invention, there are no particular restrictions on the drying; it is sufficient that moisture is removed. In the present invention, there are no particular restrictions on the rectification conditions; rectification conditions well known to those skilled in the art may be used. In the present invention, the rectification residue contains unreacted fluoroform and other by-products (including octafluoroisobutylene), but in the present invention, the utilization rate of fluoroform and the yield of carbon tetrafluoride can be improved by pyrolyzing the rectification residue again. In existing purification methods, it is necessary to remove octafluoroisobutene and then recycle it, but in the purification method used in the present invention, it is not necessary to remove octafluoroisobutene separately, and octafluoroisobutene undergoes a pyrolysis reaction to produce carbon tetrafluoride without accumulation, thus improving the yield of carbon tetrafluoride.

[0028] After drying, the present invention preferably includes sampling and detecting the obtained dried hydrogen fluoride-removed pyrolysis gas, the detection of which is preferably gas chromatography analysis and is used to confirm the composition of the pyrolysis gas (i.e., dried hydrogen fluoride-removed pyrolysis gas) from which carbon black, HF and water have been removed.

[0029] In the present invention, the production of carbon tetrafluoride using fluoroform as a raw material (thermal decomposition reaction and purification) is preferably carried out in a thermal decomposition and purification apparatus, and according to the direction of material flow, the thermal decomposition and purification apparatus preferably includes a thermal plasma reactor 1, a cooling device 2, a gas-solid separation device 3, a water-alkaline washing device 4, a drying device 5, and a rectification device 6, which are preferably connected sequentially via piping.

[0030] In this invention, the thermal plasma reactor 1 is connected to a fluoroform supply pipe, and the thermal plasma reactor 1 is further equipped with a pyrolysis gas outlet and a rectification residue inlet. The type of thermal plasma reactor 1 and the input power are the same as those for the pyrolysis reaction step, so they will not be explained again here.

[0031] In the present invention, the cooling method used by the cooling device is a partition-type heat exchange cooling device, the partition-type heat exchange cooling device includes a first partition-type heat exchange cooling device and a second partition-type heat exchange cooling device, the cooling medium of the first partition-type heat exchange cooling device is preferably water or a freezing liquid, and the cooling medium of the second partition-type heat exchange cooling device is preferably fluoroform.

[0032] In the present invention, the gas-solid separation apparatus 3 is located in the purification section described above and will not be explained again here, but the gas-solid separation apparatus 3 is provided with a carbon black outlet.

[0033] In the present invention, the water-alkaline cleaning device 4 contains water or an alkaline aqueous solution, the water-alkaline cleaning device 4 is preferably further equipped with a jacket, and circulating water is preferably provided inside the jacket, the water-alkaline cleaning device 4 is preferably a multi-stage water-alkaline cleaning device, the multi-stage water-alkaline cleaning device is preferably configured by connecting a plurality of absorption cleaning devices in series, jackets are preferably provided outside each absorption cleaning device, and circulating water is preferably provided inside the jacket, the carbon black removal pyrolysis gas enters the first absorption cleaning device, is cleaned, and then enters the next absorption cleaning device to continue the removal of hydrofluoric acid. The water-alkaline cleaning device used in the present invention not only achieves the purpose of removing acid, but can also further cool the material to prevent the occurrence of secondary reactions.

[0034] In the present invention, there are no particular limitations on the drying apparatus 5, and any drying apparatus commonly used in the chemical industry and well known to those skilled in the art may be used.

[0035] In the present invention, the rectification apparatus 6 is further equipped with a rectification residue outlet and a carbon tetrafluoride outlet, and the rectification residue outlet is connected via piping to the rectification residue inlet of the thermal plasma reactor 1.

[0036] In the present invention, a sampling port is preferably provided in the piping that connects the drying apparatus 5 and the rectification apparatus 6.

[0037] In the present invention, the pyrolysis purification apparatus is preferably further equipped with a carbon tetrafluoride finished product storage device 7 whose inlet is connected by piping to the carbon tetrafluoride outlet of the rectification apparatus 6.

[0038] In the present invention, the material of each connecting pipe used in the cooling device 2, the gas-solid separation device 3, the water-alkaline washing device 4, and the pyrolysis purification device is preferably, independently, silicon carbide, Hastelloy C alloy, Monel alloy, or stainless steel lined with polytetrafluoroethylene.

[0039] The technical solutions of the present invention are described below clearly and completely with reference to embodiments of the present invention. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all embodiments. All other embodiments that can be obtained by those skilled in the art without creative effort based on embodiments of the present invention are included within the scope of protection of the present invention.

[0040] Example 1 Carbon tetrafluoride was produced using the pyrolysis purification apparatus shown in Figure 1.

[0041] Fluoroform (flow rate: 3Nm 3 A fluoride-free pyrolysis gas is passed through a thermal plasma reactor and an arc is started (input power: 15kW). A rotating arc plasma is formed, and a pyrolysis reaction occurs at millisecond levels under conditions of 3500K to obtain pyrolysis gas. The pyrolysis gas is then sequentially cooled by partition heat exchange (cooling medium: water and fluoroform) to 350K, followed by gas-solid separation, washing with an alkaline aqueous solution, and drying to obtain a pyrolysis gas with hydrogen fluoride removed. After sampling and gas chromatography analysis, it is rectified to obtain high-purity carbon tetrafluoride and rectification residue. The rectification residue (unreacted fluoroform and other by-products) is sent back to the thermal plasma reactor for further pyrolysis to produce carbon tetrafluoride. Here, the cooled waste heat is used to preheat the fluoroform.

[0042] Following detection and analytical calculations using gas chromatography, the one-pass conversion rate of fluoroform was 99.2%, the purity of carbon tetrafluoride in the hydrogen fluoride removal pyrolysis gas was 92.3%, the selectivity of carbon tetrafluoride was 94.2%, and the purity of high-purity carbon tetrafluoride reached the electron level.

[0043] Example 2 Carbon tetrafluoride was produced using the pyrolysis purification apparatus shown in Figure 1.

[0044] After heat exchange with pyrolysis gas, fluoroform (flow rate: 3 Nm³) 3A fluoride-free pyrolysis gas is passed through a thermal plasma reactor and an arc is started (input power: 11kW). A rotating arc plasma is formed, and a pyrolysis reaction occurs at millisecond levels under conditions of 3300K to obtain pyrolysis gas. The pyrolysis gas is then sequentially cooled by partition heat exchange (cooling medium: water and fluoroform) to 400K, followed by gas-solid separation, washing with an alkaline aqueous solution, and drying to obtain a hydrogen fluoride-free pyrolysis gas. After sampling and gas chromatography analysis, it is rectified to obtain high-purity carbon tetrafluoride and rectification residue. The rectification residue (unreacted fluoroform and other by-products) is sent back to the thermal plasma reactor for further pyrolysis to produce carbon tetrafluoride. Here, the cooled waste heat is used to preheat the fluoroform.

[0045] Following detection and analytical calculations using gas chromatography, the one-pass conversion rate of fluoroform was 99.0%, the purity of carbon tetrafluoride in the hydrogen fluoride removal pyrolysis gas was 91.2%, the selectivity of carbon tetrafluoride was 93.7%, and the purity of high-purity carbon tetrafluoride reached the electron level.

[0046] Example 3 Carbon tetrafluoride was produced using the pyrolysis purification apparatus shown in Figure 1.

[0047] After heat exchange with pyrolysis gas, fluoroform (flow rate: 12 Nm³) 3 A 20kW (input power) is introduced into a thermal plasma reactor, and an arc is started. A rotating arc plasma is formed, and a pyrolysis reaction occurs at millisecond levels under conditions of 3800K to obtain pyrolysis gas. The pyrolysis gas is then sequentially cooled by partition heat exchange (cooling medium: ethylene glycol and fluoroform) to 298K, followed by gas-solid separation, washing with an alkaline aqueous solution, and drying to obtain a pyrolysis gas with hydrogen fluoride removed. This gas is sampled and analyzed by gas chromatography, then rectified to obtain high-purity carbon tetrafluoride and rectification residue. The rectification residue (unreacted fluoroform and other by-products) is sent back to the thermal plasma reactor for further pyrolysis to produce carbon tetrafluoride. Here, the cooled waste heat is used to preheat the fluoroform.

[0048] Following detection and analytical calculations using gas chromatography, the one-pass conversion rate of fluoroform was 99.3%, the purity of carbon tetrafluoride in the hydrogen fluoride removal pyrolysis gas was 93.4%, the selectivity of carbon tetrafluoride was 94.3%, and the purity of high-purity carbon tetrafluoride reached the electron level.

[0049] Example 4 Carbon tetrafluoride was produced using the pyrolysis purification apparatus shown in Figure 1.

[0050] After heat exchange with pyrolysis gas, fluoroform (flow rate: 600 Nm³) 3 A 1MW (1 / h) is flowed into a thermal plasma reactor to initiate an arc, forming a rotating arc plasma. Under conditions of 4000K, a pyrolysis reaction occurs at the millisecond level to obtain pyrolysis gas. The pyrolysis gas is then sequentially cooled by partition heat exchange (using ethylene glycol and fluoroform as cooling media) to 298K, followed by gas-solid separation, washing with an alkaline aqueous solution, and drying to obtain a pyrolysis gas with hydrogen fluoride removed. This gas is sampled, analyzed by gas chromatography, and then rectified to obtain high-purity carbon tetrafluoride and rectification residue. The rectification residue (unreacted fluoroform and other by-products) is sent back to the thermal plasma reactor for further pyrolysis to produce carbon tetrafluoride. The cooled waste heat is used to preheat the fluoroform.

[0051] Following detection and analytical calculations using gas chromatography, the one-pass conversion rate of fluoroform was 99.1%, the purity of carbon tetrafluoride in the hydrogen fluoride removal pyrolysis gas was 94.8%, the selectivity of carbon tetrafluoride was 95.2%, and the purity of high-purity carbon tetrafluoride reached the electron level.

[0052] Comparative Example 1 Fluoroform (flow rate: 100 mL / min) was flowed into a tubular furnace. The preheating outlet temperature was 895°C, the reaction intermediate temperature was 910°C, and the reaction residence time was 2 s. The pyrolysis gas at the outlet of the tubular furnace was sequentially washed and dried with an alkaline aqueous solution. The resulting acid-removed pyrolysis gas was sampled and subjected to gas chromatography analysis. Analysis and calculations revealed that the one-pass conversion rate of fluoroform was 61.6%, the tetrafluoroethylene concentration in the acid-removed pyrolysis gas was 5.1 wt%, the hexafluoropropylene concentration was 46.8 wt%, and carbon tetrafluoride was not detected.

[0053] It should be noted that the above are merely preferred embodiments of the present invention, and those skilled in the art can make many improvements and embellishments without departing from the principles of the present invention, and these improvements and embellishments should also be considered within the scope of protection of the present invention. [Explanation of symbols]

[0054] 1. Thermal plasma reactor 2 cooling device 3 Gas-solid separator 4. Water-Alkaline Cleaning System 5 drying equipment 6. Rectification apparatus 7. Storage device for finished tetrafluorocarbon products

Claims

1. The process includes the step of injecting fluoroform into a thermal plasma reactor to carry out a thermal decomposition reaction to obtain carbon tetrafluoride, wherein the temperature of the thermal decomposition reaction is 3000 to 4500 K. The aforementioned thermal decomposition reaction can be carried out without the use of carrier gases for dilution or auxiliary thermal decomposition. The thermal plasma reactor is an arc thermal plasma reactor. A method for producing tetrafluorocarbon using fluoroform as a raw material, characterized by the above.

2. The fluoroform has a flow rate of 0.5 to 1000 Nm³ / h. The method according to claim 1.

3. The process includes further purifying the pyrolysis gas obtained from the pyrolysis reaction, and the purification process includes: The pyrolysis gas is cooled and then separated into gas and solid to obtain a carbon black-removed pyrolysis gas, and the cooling includes cooling to 600-1000K by a first partition-type heat exchanger, followed by cooling to 298-400K by a second partition-type heat exchanger, wherein the cooling medium for the cooling by the second partition-type heat exchanger is fluoroform. The carbon black removal pyrolysis gas is washed with water-alkaline to obtain a hydrogen fluoride removal pyrolysis gas, The process includes drying the hydrogen fluoride removal pyrolysis gas, then rectifying it to obtain carbon tetrafluoride and a rectification residue, and reusing the rectification residue in the pyrolysis reaction. The method according to claim 1.

4. The cooling medium for the first partition-type heat exchange is water. The method according to claim 3.

5. The water-alkaline wash includes water washing and / or alkaline aqueous solution washing, wherein the mass concentration of alkali in the alkaline aqueous solution is 40% or less, and the alkali includes sodium hydroxide and / or potassium hydroxide. The method according to claim 3.

6. The gas-solid separation is carried out using a gas-solid separation apparatus, which includes a single-stage gas-solid separation apparatus or a multi-stage gas-solid separation apparatus. The method according to claim 3.

7. The gas-solid separation apparatus includes a filter or a cyclone separator. The method according to claim 6.

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