Method for producing carbon tetrafluoride 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 fluoroform resource utilization, and in particular to a method for producing carbon tetrafluoride using fluoroform as a raw material. law Regarding.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from a Chinese patent application bearing application number CN202310984672.X, filed with the China Patent Office on August 7, 2023, for the invention entitled "Method for producing carbon tetrafluoride using fluoroform as raw material," the entire contents of which are incorporated herein by reference. [Background technology]

[0003] Fluoroform (R23) is an unavoidable by-product in manufacturing processes such as the reaction of hydrogen fluoride and chloroform to produce difluorochloromethane (HCFC-22) and the thermal decomposition of HCFC-22 to produce tetrafluoroethylene. Its application is relatively narrow, making it difficult to use as a chemical industrial raw material for other products. It is used only for specific applications, such as fire extinguishing agents and semiconductor etching agents. While R23 itself does not deplete the ozone layer, it does cause severe greenhouse effects. Its global warming potential (GWP) is 14,800 times that of CO2 and can remain stable in the atmosphere for 264 years. Atmospheric R23 concentrations have been steadily increasing at a rate of 5% per year for the past several decades, posing serious ecological risks. Currently, the primary method for disposing of R23 is incineration, which involves thorough incineration and thermal decomposition of R23 into HF, CO2, and other substances, thereby avoiding adverse environmental impacts. However, because R23 itself is very stable, it is difficult to thermally decompose even under combustion conditions. Therefore, extremely harsh reaction conditions are often required for incineration, which tends to increase processing costs and capital investment, and makes it impossible to recover valuable materials. If the HF produced is not recovered, post-processing of the fluoride salts must also be considered, reducing the useful value of the product. Therefore, there is an urgent need to develop a new method for recycling R23 that is clean, efficient, and produces high-value-added products.

[0004] Carbon tetrafluoride (R14), the most widely used plasma etching gas in the microelectronics industry, has broad potential for development. Currently, R14 is primarily synthesized industrially using hydrofluoromethane fluorination, chlorofluoromethane fluorination, and direct fluorination of carbon and fluorine gas. However, the gradual ban on CFCs and HCFCs has limited raw material sources for the chlorofluoromethane fluorination method. Both the direct fluorination of carbon and fluorine gas and the hydrofluoromethane fluorination method suffer from issues 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 the efficient preparation of R14 that is safe, controllable, and suitable for industrial scale-up. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of this, the present invention provides a method for producing carbon tetrafluoride using fluoroform as a raw material. law The method provided by the present invention has a high conversion rate of fluoroform, a high selectivity for carbon tetrafluoride, a large throughput, is safe and controllable, and is suitable for continuous industrial scale-up production. [Means for solving the problem]

[0006] In order to achieve the above objectives of the present invention, the present invention provides the following technical solutions: The present invention provides a method for producing carbon tetrafluoride using fluoroform as a raw material, The method includes a step of injecting fluoroform into a thermal plasma reactor to carry out a pyrolysis reaction to obtain carbon tetrafluoride, and the temperature of the pyrolysis reaction is 1500 to 5000K.

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

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

[0009] Preferably, the pyrolysis reaction time is on the order of milliseconds.

[0010] Preferably, after the pyrolysis reaction, the pyrolysis gas obtained by the pyrolysis reaction is further purified, and the purification includes: a method for cooling the pyrolysis gas and then subjecting the gas to gas-solid separation to obtain a carbon black-removed pyrolysis gas, the cooling step including cooling the pyrolysis gas to 600 to 1000 K by a first partition wall type heat exchanger and then cooling the pyrolysis gas to 298 to 400 K by a second partition wall type heat exchanger, and the cooling medium used in the second partition wall type heat exchanger is fluoroform; washing the carbon black-removed pyrolysis gas with water and alkali to obtain a hydrogen fluoride-removed pyrolysis gas; The hydrogen fluoride-removed pyrolysis gas is dried and then rectified to obtain high-purity carbon tetrafluoride and a rectification residue, and the rectification residue is reused in the pyrolysis reaction.

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

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

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

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

[0015] The present invention provides a method for producing carbon tetrafluoride using fluoroform as a raw material, which includes a 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 to 5000K. Compared with conventional tubular furnace pyrolysis or muffle furnace high-temperature pyrolysis, the thermal plasma reactor used in the present invention relies on the synergistic effect of highly active electrons and heavy particles at high temperatures, resulting in significant electron excitation. This effectively breaks the chemical bonds of fluoroform molecules and reorganizes their directionality without the need for a catalyst or fluorine gas. This results in a high fluoroform conversion rate, high selectivity for carbon tetrafluoride, a short reaction time, a large throughput, and a safe and controllable process. The pyrolysis reaction products have a simple composition and are easy to separate and purify, resulting in low-cost, low-energy consumption. This makes the process suitable for continuous, scaled-up industrial production. This enables the low-cost, low-energy recovery and utilization of fluoroform as a resource. This is particularly suitable for the conversion of fluoroform, a by-product of processes such as the production of difluorochloromethane or the thermal decomposition of difluorochloromethane to produce tetrafluoroethylene, into a resource. This avoids the greenhouse effect caused by direct fluoroform emissions and the waste of resources caused by incineration, and produces high-value-added carbon tetrafluoride products, thereby bringing significant economic and social benefits. Furthermore, since the present invention does not use any catalyst, problems such as catalyst coking and deactivation, susceptibility to 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 uses a first partition wall-type heat exchanger to cool the fluoroform to 600 to 1000 K, and then a second partition wall-type heat exchanger to cool it to 298 to 400 K, and uses the waste heat from the second partition wall-type heat exchanger to preheat the fluoroform. This avoids the high-temperature waste heat from the first partition wall-type heat exchanger from causing the fluoroform to react and produce by-products, and also makes full use of the waste heat from the second partition wall-type heat exchanger, thereby significantly reducing energy consumption and production costs. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram of a pyrolysis purification apparatus used in producing carbon tetrafluoride using fluoroform as a raw material. DETAILED DESCRIPTION OF THE INVENTION

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

[0019] In the present invention, the flow rate of the fluoroform is preferably 0.5 to 1000 Nm 3 / h, more preferably 1 to 800 Nm 3 / h, and more preferably 3 to 600 Nm 3 / h. The present invention is not particularly limited by the source of the fluoroform, and fluoroform may be fluoroform produced in the difluorochloromethane production process known to those skilled in the art, fluoroform generated in the tetrafluoroethylene production process by thermal decomposition of difluorochloromethane, or fluoroform recovered from a factory or other process route, with the purity of the fluoroform preferably being 90% or higher. The production method provided by the present invention can realize the recycling of fluoroform by-produced in the difluorochloromethane production process or the process of producing tetrafluoroethylene by thermal decomposition of difluorochloromethane, as well as 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, and the arc thermal plasma reactor is preferably a direct current arc plasma reactor, more preferably a magnetic rotating arc thermal plasma reactor. The direct current arc plasma reactor used in the present invention has high mass transfer efficiency and heat transfer efficiency, uniform residence time, and easy control. Since the present invention uses a thermal plasma reactor to pyrolyze fluoroform and does not require a carrier gas for dilution or auxiliary pyrolysis, the pyrolysis gas obtained by the pyrolysis reaction has a simple composition, which further simplifies the subsequent purification process.

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

[0022] After the pyrolysis reaction, the present invention preferably further includes purifying the pyrolysis gas obtained by the pyrolysis reaction, and the purification includes: a method for cooling the pyrolysis gas and then subjecting the gas to gas-solid separation to obtain a carbon black-removed pyrolysis gas, the cooling step including cooling the pyrolysis gas to 600 to 1000 K by a first partition wall type heat exchanger and then cooling the pyrolysis gas to 298 to 400 K by a second partition wall type heat exchanger, the cooling medium used in the second partition wall type heat exchanger being fluoroform; washing the carbon black-removed pyrolysis gas with water and alkali to obtain a hydrogen fluoride-removed pyrolysis gas; The hydrogen fluoride-removed pyrolysis gas is dried and then rectified to obtain high-purity carbon tetrafluoride and a rectification residue, and the rectification residue is reused in the pyrolysis reaction.

[0023] In the present invention, the pyrolysis gas is cooled and then subjected to gas-solid separation to obtain a carbon black-removed pyrolysis gas. The cooling includes cooling to 600 to 1000 K using a first partition wall-type heat exchanger and then cooling to 298 to 400 K using a second partition wall-type heat exchanger. In the present invention, the cooling medium used in the first partition wall-type heat exchanger is preferably water or a frozen liquid. In the present invention, there are no particular requirements for the specific type of frozen liquid; any frozen liquid having a cooling function known to those skilled in the art may be used, specifically, ethylene glycol, for example. In the present invention, the temperature after cooling is preferably 298 K, 350 K, or 400 K. In the present invention, the cooling medium used in the second partition wall heat exchanger is fluoroform. That is, the waste heat from the second partition wall heat exchanger is used to preheat and cool fluoroform, and the preheated fluoroform is then injected into a thermal plasma reactor for pyrolysis. This makes it possible to fully utilize the heat of the pyrolysis gas, assuming that fluoroform undergoes no side reactions, and further reduces energy consumption and production costs.

[0024] In the present invention, the gas-solid separation is preferably carried out using a gas-solid separator, which preferably includes a single-stage gas-solid separator or a multi-stage gas-solid separator, 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 separator is preferably a two-stage gas-solid separator, and the first-stage solid-solid separator in the two-stage gas-solid separator is preferably a cyclone separator and is used to capture carbon black particles with a particle size of 5 μm or more (larger carbon black particles or agglomerates of small carbon black particles), and the second-stage gas-solid separator in the two-stage gas-solid separator is preferably a filter and 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 the carbon black-removed pyrolysis gas, the present invention provides a hydrogen fluoride-removed pyrolysis gas by subjecting the carbon black-removed pyrolysis gas to water-alkali washing. In the present invention, the water-alkali washing preferably includes water washing and / or washing with an aqueous alkaline solution, the mass concentration of the alkali in the aqueous alkaline solution is preferably 40% or less, more preferably 15 to 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 the hydrogen fluoride-removed pyrolysis gas, the present invention dries the hydrogen fluoride-removed pyrolysis gas and then rectifies it to obtain high-purity carbon tetrafluoride and a rectification residue, which is then reused in the pyrolysis reaction. The present invention does not particularly limit the drying method, as long as it can remove moisture. The present invention also does not particularly limit the rectification conditions, and rectification conditions well known to those skilled in the art can be used. In the present invention, the rectification residue contains unreacted fluoroform and other by-products (including octafluoroisobutylene). In the present invention, the rectification residue is further pyrolyzed, thereby improving the utilization rate of fluoroform and the yield of carbon tetrafluoride. While existing purification methods require the removal and recycling of octafluoroisobutene, the purification method used in the present invention does not require the separate removal of octafluoroisobutene, and octafluoroisobutene undergoes a pyrolysis reaction to produce carbon tetrafluoride without accumulating, thereby improving the yield of carbon tetrafluoride.

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

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

[0030] In the present 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 and input power of the thermal plasma reactor 1 are consistent with those of the pyrolysis reaction step, and therefore will not be described again here.

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

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

[0033] In the present invention, the water-alkali scrubbing device 4 contains water or an alkaline aqueous solution, and is preferably further equipped with a jacket, with circulating water preferably installed inside the jacket. The water-alkali scrubbing device 4 is preferably a multi-stage water-alkali scrubbing device, which is preferably configured by connecting multiple absorption scrubbing devices in series, with each absorption scrubbing device preferably equipped with a jacket outside, and with circulating water preferably installed inside the jacket. The carbon black removal pyrolysis gas enters the first absorption scrubbing device, is scrubbed, and then enters the next absorption scrubbing device to continue removing hydrofluoric acid. The water-alkali scrubbing device used in the present invention not only achieves the purpose of acid removal, but also cools the material to prevent secondary reactions from occurring.

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

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

[0036] In the present invention, the pipe connecting the drying device 5 and the rectification device 6 is preferably provided with a sampling port.

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

[0038] In the present invention, the materials of the respective communicating pipes used in the cooling device 2, the gas-solid separation device 3, the water-alkali washing device 4, and the pyrolysis purification device preferably independently include silicon carbide, Hastelloy C alloy, Monel alloy, or stainless steel lined with polytetrafluoroethylene.

[0039] The technical solutions of the present invention are clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall 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 / h) into a thermal plasma reactor, and after arc initiation (input power: 15 kW), a rotating arc plasma is formed, and a thermal decomposition reaction occurs at 3500 K on the order of milliseconds, producing a pyrolysis gas. The pyrolysis gas is then sequentially cooled by a partition wall heat exchanger (cooling media: water and fluoroform) to 350 K, gas-solid separation, washed with an alkaline aqueous solution, and dried to obtain a hydrogen fluoride-removed pyrolysis gas. This gas is sampled, analyzed by gas chromatography, and then rectified to obtain high-purity carbon tetrafluoride and a rectification residue. The rectification residue (unreacted fluoroform and other by-products) is returned to the thermal plasma reactor for a thermal decomposition reaction to produce carbon tetrafluoride. The cooled waste heat is used to preheat the fluoroform.

[0042] After gas chromatography detection and analytical calculation, the one-pass conversion rate of fluoroform was 99.2%, the purity of carbon tetrafluoride in the hydrogen fluoride-removed pyrolysis gas was 92.3%, the selectivity of carbon tetrafluoride was 94.2%, and the purity of high-purity carbon tetrafluoride reached electronic level.

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

[0044] After heat exchange with the pyrolysis gas, fluoroform (flow rate: 3 Nm 3 / h) into a thermal plasma reactor, and after arc initiation (input power: 11 kW), a rotating arc plasma was formed, and a thermal decomposition reaction took place at 3300 K on the order of milliseconds, yielding a pyrolysis gas. The pyrolysis gas was then sequentially cooled to 400 K by a partition wall heat exchanger (cooling media: water and fluoroform), gas-solid separation, washed with an alkaline aqueous solution, and dried to obtain a hydrogen fluoride-removed pyrolysis gas. This gas was sampled and analyzed by gas chromatography, and then rectified to obtain high-purity carbon tetrafluoride and a rectification residue. The rectification residue (unreacted fluoroform and other by-products) was returned to the thermal plasma reactor for a thermal decomposition reaction to produce carbon tetrafluoride. The cooled waste heat was used to preheat the fluoroform.

[0045] After gas chromatography detection and analytical calculation, the one-pass conversion rate of fluoroform was 99.0%, the purity of carbon tetrafluoride in the hydrogen fluoride-removed 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 the pyrolysis gas, fluoroform (flow rate: 12 Nm 3 / h) into a thermal plasma reactor, and after arc initiation (input power: 20 kW), a rotating arc plasma is formed, and a thermal decomposition reaction occurs at 3800 K on the order of milliseconds, producing a pyrolysis gas. The pyrolysis gas is then sequentially cooled to 298 K by a partition wall heat exchanger (cooling media: ethylene glycol and fluoroform), gas-solid separation, washed with an alkaline aqueous solution, and dried to obtain a hydrogen fluoride-removed pyrolysis gas. This gas is sampled, analyzed by gas chromatography, and then rectified to obtain high-purity carbon tetrafluoride and a rectification residue. The rectification residue (unreacted fluoroform and other by-products) is returned to the thermal plasma reactor for a thermal decomposition reaction to produce carbon tetrafluoride. The cooled waste heat is used to preheat the fluoroform.

[0048] After gas chromatography detection and analytical calculation, the one-pass conversion rate of fluoroform was 99.3%, the purity of carbon tetrafluoride in the hydrogen fluoride-removed pyrolysis gas was 93.4%, the selectivity of carbon tetrafluoride was 94.3%, and the purity of high-purity carbon tetrafluoride reached electronic level.

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

[0050] After heat exchange with the pyrolysis gas, fluoroform (flow rate: 600 Nm 3 / h) into a thermal plasma reactor, and after arc initiation (input power: 1 MW), a rotating arc plasma is formed, and a thermal decomposition reaction occurs at 4000 K on the order of milliseconds, producing a pyrolysis gas. The pyrolysis gas is then sequentially cooled to 298 K by a partition wall heat exchanger (cooling media: ethylene glycol and fluoroform), gas-solid separation, washed with an alkaline aqueous solution, and dried to obtain a hydrogen fluoride-removed pyrolysis gas. This gas is sampled, analyzed by gas chromatography, and then rectified to obtain high-purity carbon tetrafluoride and a rectification residue. The rectification residue (unreacted fluoroform and other by-products) is returned to the thermal plasma reactor for a thermal decomposition reaction to produce carbon tetrafluoride. The cooled waste heat is used to preheat the fluoroform.

[0051] After gas chromatography detection and analytical calculation, the one-pass conversion rate of fluoroform was 99.1%, the purity of carbon tetrafluoride in the hydrogen fluoride-removed pyrolysis gas was 94.8%, the selectivity of carbon tetrafluoride was 95.2%, and the purity of high-purity carbon tetrafluoride reached electronic 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 middle 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 with an aqueous alkali solution and dried, and the resulting acid-removed pyrolysis gas was sampled and analyzed by gas chromatography. 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 no carbon tetrafluoride was detected.

[0053] It should be noted that the above is only a preferred embodiment of the present invention, and those skilled in the art can make many improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered as part of the protection scope of the present invention. [Explanation of symbols]

[0054] 1. Thermal plasma reactor 2 cooling device 3 Gas-solid separator 4. Water-alkali cleaning equipment 5 drying equipment 6. Rectification unit 7. Carbon tetrafluoride finished product storage device

Claims

1. The method includes the step of injecting fluoroform into a thermal plasma reactor to carry out a pyrolysis reaction to obtain carbon tetrafluoride, and the temperature of the pyrolysis reaction is 1500 to 5000 K. A method for producing carbon tetrafluoride using fluoroform as a raw material, comprising:

2. The fluoroform has a viscosity of 0.5 to 1000 Nm ３ / h flow rate The method of claim 1.

3. The thermal plasma reactor includes an RF thermal plasma reactor, a microwave thermal plasma reactor, or an arc thermal plasma reactor. The method of claim 1.

4. The thermal decomposition reaction time is in the millisecond range.

4. The method according to claim 1.

5. After the pyrolysis reaction, the pyrolysis gas obtained by the pyrolysis reaction is further purified, and the purification includes: a method for cooling the pyrolysis gas and then subjecting the gas to gas-solid separation to obtain a carbon black-removed pyrolysis gas, the cooling step including cooling the gas to 600 to 1000 K by a first partition wall type heat exchanger and then cooling the gas to 298 to 400 K by a second partition wall type heat exchanger, the cooling medium used in the second partition wall type heat exchanger being fluoroform; washing the carbon black-removed pyrolysis gas with water and / or an alkaline aqueous solution to obtain a hydrogen fluoride-removed pyrolysis gas; drying the hydrogen fluoride-removed pyrolysis gas, and then rectifying the gas to obtain high-purity carbon tetrafluoride and a rectification residue, and reusing the rectification residue in the pyrolysis reaction. The method of claim 1.

6. The cooling medium for the first partition-type heat exchanger is water or a frozen liquid. The method of claim 5.

7. The alkali concentration in the alkaline aqueous solution is 40% or less, and the alkali includes sodium hydroxide and / or potassium hydroxide. The method of claim 5.

8. The gas-solid separation is carried out using a gas-solid separator, which may be a single-stage gas-solid separator or a multi-stage gas-solid separator. The method of claim 5.

9. The gas-solid separation device includes a filter or a cyclone separator. The method of claim 8.

10. The system comprises a thermal plasma reactor (1), a cooling device (2), a gas-solid separator (3), a water-alkali washing device (4), a drying device (5), and a rectification device (6), which are connected in sequence via piping in accordance with the direction of material flow; A fluoroform supply pipe is connected to the thermal plasma reactor (1), and a pyrolysis gas outlet is installed in the thermal plasma reactor (1); The rectification device (6) is provided with a carbon tetrafluoride outlet. A pyrolysis purification apparatus for producing carbon tetrafluoride from fluoroform, characterized by:

11. The cooling device (2) is a partition-type heat exchange cooling device. The pyrolysis purification apparatus according to claim 10.

12. The partition wall type heat exchange cooling device includes a first partition wall type heat exchange cooling device and a second partition wall type heat exchange cooling device, the cooling medium of the first partition wall type heat exchange cooling device is water or a frozen liquid, and the cooling medium of the second partition wall type heat exchange cooling device is fluoroform. The pyrolysis purification apparatus according to claim 11.

13. The thermal plasma reactor (1) is further provided with a rectification residue inlet; The rectification device (6) is further provided with a rectification residue outlet, and the rectification residue outlet and the rectification residue inlet of the thermal plasma reactor (1) are connected by piping. The pyrolysis purification apparatus according to claim 11.

14. The thermal decomposition purification apparatus further includes a carbon tetrafluoride finished product storage device (7) whose inlet is connected to the carbon tetrafluoride outlet of the rectification device (6) by piping. The pyrolysis purification apparatus according to any one of claims 10 to 13.

15. The materials of the cooling device (2), the gas-solid separation device (3), the water-alkali washing device (4) and the piping independently include silicon carbide, Hastelloy C alloy, Monel alloy, or stainless steel lined with polytetrafluoroethylene. The pyrolysis purification apparatus according to claim 14.

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