Hexafluorobutadiene manufacturing method and production system

Abstract

The present invention discloses a method and system for producing hexafluorobutadiene, which includes the following steps: In step (1), an organic solution of bromotrifluoroethylene and zinc powder are respectively introduced into a first reactor containing an initiator, zinc powder, and an organic solvent, followed by a second reactor, and reacted to obtain a trifluorovinylzinc bromide solution. The reaction solution is then introduced into a precipitator to separate excess zinc powder, resulting in a zinc-free trifluorovinylzinc bromide solution. The excess zinc powder is then filtered and reused. In step (2), the trifluorovinylzinc bromide solution obtained above and a pre-prepared composite catalyst solution are introduced into a third reactor and subjected to a coupling reaction to obtain crude hexafluorobutadiene. In step (3), the crude hexafluorobutadiene obtained above is purified to obtain a product with a purity of ≥ 99.9%.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from a Chinese patent application with application number 202311705885.0, filed with the China Patent Office on December 12, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the production of fluorine-containing electronic gases, and in particular to a method and system for producing hexafluorobutadiene. [Background technology]

[0003] Hexafluorobutadiene (C4F6) is a colorless, liquefiable fluorine-containing gas with a boiling point of 5.5°C at atmospheric pressure and a liquid density of 1.44 g / mL at 15°C. Currently, hexafluorobutadiene is primarily used as a dry etching gas for precision etching of critical dimensions (up to 100 nm) in the production of Cu-containing low-K dielectric rectifier circuit boards. Its selectivity and depth-to-width ratio are superior to those of other etching gases. For example, compared with octafluorocyclobutane (c-C4F8), the width-to-depth ratio of C4F6 reaches 10, while that of c-C4F8 is only 3, making C4F6 suitable for ultra-narrow linewidth processes. C4F6 only etches silicon oxide films, leaving photoresist, silicon films, and nitride films unaffected, resulting in excellent etching selectivity. In addition, hexafluorobutadiene has good environmental properties, with ODP=0, GWP(100)=290, and a residence time in the atmosphere of only 1.9 days, making it a green and environmentally friendly etching gas with a very small greenhouse effect. Therefore, with the development of the integrated circuit industry and increasing attention to greenhouse gases, hexafluorobutadiene, which has the best etching effect and environmental friendliness, is sure to become a mainstream product and be widely used in the laser etching agent market.

[0004] The production process of hexafluorobutadiene has been one of the hotspots of research in recent years, but there are few that can be truly realized on an industrial scale. The main reports on the production of hexafluorobutadiene using conventional technology are as follows:

[0005] (1) Oxidative coupling process The homocoupling route centers on the preparation of the key intermediate trifluorovinylzinc halides (CF2 = CFZnX), which can then be further reacted with Fe 3+ or Cu 2+ For example, WO2006 / 026400 describes the preparation of bromotrifluoroethylene (CF2=CFBr) from chlorotrifluoroethylene (CF2=CFCl) by hydrogenation, dechlorination, bromination, and removal of hydrogen bromide, followed by the reaction with zinc powder to prepare trifluorovinylzinc bromide (CF2=CFZnBr), and finally the preparation of hexafluorobutadiene by the reaction with Fe 3+ or Cu 2+ It has been disclosed that hexafluorobutadiene is obtained by homocoupling reaction in the presence of ions. Although this method uses inexpensive materials, it involves many dangerous production steps, and there is a risk of self-polymerization of the intermediate product trifluoroethylene, making it unsuitable for industrial mass production.

[0006] CN104829415 discloses a process route for producing hexafluorobutadiene using tetrafluoroethane (HFC-134a) as a raw material. First, tetrafluoroethane and bromine are reacted at high temperature to obtain 1,1-dibromotetrafluoroethane, which is then reacted with zinc powder in a polar aprotic solvent to prepare trifluorovinylzinc bromide. Finally, Fe 3+The reaction is carried out by homocoupling in the presence of an oxidizing agent to obtain hexafluorobutadiene, with a total yield of 47%. This reaction uses the inexpensive refrigerant HFC-134a as raw material and has a relatively short process route, but due to the low activity of 1,1-dibromotetrafluoroethane and the low yield when preparing zinc powder and trifluorovinylzinc bromide, this process route results in a high actual unit consumption and generates a large amount of waste liquid, waste gas, and solid waste, making it unlikely to be put into practical industrial use.

[0007] The Journal of Fluorine Chemistry 129 (2008) 443-446 reports that trifluorovinylzinc chloride was prepared in a zinc chloride / tetrahydrofuran system using tetrafluoroethane (HFC-134a) as a raw material and lithium diisopropylamide (LDA) as a hydrogen abstracting agent. 2+ or Fe 3+ Hexafluorobutadiene is obtained under the action of R134a, with a reaction yield of 69-70%. This process is inexpensive and easily available, and the synthesis steps are simple, allowing for a "one-pot" synthesis. However, the strong base lithium diisopropylamide (LDA) used in the first reaction is expensive, and the production process is highly dangerous, making it unlikely to be industrially feasible.

[0008] JP2001114710 reports a process route for synthesizing hexafluorobutadiene using tetrafluoroethylene as a raw material. First, 1,2-dibromotetrafluoroethane is obtained by an addition reaction of tetrafluoroethylene with bromine, and then 1,2-dibromotetrafluoroethane is rearranged in the presence of a Lewis acid catalyst to obtain 1,1-dibromotetrafluoroethane. Further, 1,1-dibromotetrafluoroethane is reacted with zinc powder to obtain a trifluorovinylzinc bromide reagent. Finally, Cu 2+ or Fe 3+The target product, hexafluorobutadiene, is obtained by homo-coupling a trifluorovinyl zinc bromide reagent in the presence of a catalyst. This process has relatively mild reaction conditions and relatively low raw material costs, but the overall yield of this process is low (less than 50%) and it uses tetrafluoroethylene as a raw material, limiting its industrial application.

[0009] (2) Dehalogenation process The dehalogenation process involves telomerization or intermolecular dehalogenation to obtain an intermediate tetrahalohexafluorobutane (XCF2-CFX-CFX-CF2X), which is then reacted with zinc powder in an alcohol solvent to produce hexafluorobutadiene. US 304630 discloses a method for producing perfluorobutadiene using chlorotrifluoroethylene as a raw material, in which chlorotrifluoroethylene is first reacted with iodine chloride (ICl) in a closed system at 35-40°C to obtain 1,2-dichloro-1,2,2-trifluoroiodoethane, which is then coupled with an equivalent amount of mercury under UV light irradiation to obtain 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane, and finally, 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane is dechlorinated in an alcohol solvent under the action of zinc powder to obtain hexafluorobutadiene. This method requires the use of chemical equivalents of iodine chloride and mercury to participate in the reaction, and one of the products is mercury iodide, which is a highly toxic and expensive reagent.

[0010] CN106336342 improves on this process by using zinc powder / acetic anhydride system for intermolecular coupling, avoiding the use of highly toxic mercury as a raw material. The process conditions are mild and the reaction yields for all three steps are high (90%). However, the process still requires expensive iodine as a raw material, making it unsuitable for mass production.

[0011] US 2,894,043 discloses the dimerization of 1,2-dichlorodifluoroethylene (CFCl = CFCl) in the presence of fluorine gas to synthesize the intermediate product 1,2,3,4-tetrachlorohexafluorobutane, which is then dechlorinated with zinc powder to obtain the target product, perfluorobutadiene. This method requires low-temperature conditions (-70°C) during the fluorination dimerization step and also uses the highly hazardous gas F2. US 2,676,193 improves on this method, but the reaction still requires high-temperature (300°C) and high-pressure (12 MPa) conditions, and the reaction yield is somewhat low at 30-40%, with many by-products and difficulty in product separation.

[0012] Patent document RU0118462 reports a route to synthesize hexafluorobutadiene using chlorotrifluoroethylene as a raw material. This patent avoids the use of highly toxic mercury and expensive iodine reagents. First, chlorotrifluoroethylene is dimerized at high temperatures to produce 34% 1,2-dichlorohexafluorocyclobutane and 27% 3,4-dichlorohexafluoro-1-butene. These two products are then separated using a high-efficiency distillation column. 3,4-dichlorohexafluoro-1-butene is then directly dechlorinated with zinc powder to obtain the desired product, hexafluorobutadiene. The advantage of this method is that it requires only two reaction steps to obtain CF6. However, the separation of the dimerization product requires a demanding fractional distillation process, which increases production costs somewhat. Although the yield of the desired intermediate is improved, it is still below 30%.

[0013] (3) Catalytic Coupling Process WO2018235883 discloses the use of chlorotrifluoroethylene as a raw material in the presence of a palladium catalyst, a phosphorus ligand, and zinc powder to catalyze a homocoupling reaction to obtain hexafluorobutadiene, with a maximum yield of 86.1%. CN116693365 discloses the use of chlorotrifluoroethylene and trifluoroethylene as raw materials in the presence of an activated palladium catalyst and a basic compound to obtain hexafluorobutadiene, with a maximum reaction yield of 83%. While this method is simple, it uses expensive palladium as a catalyst, which is not advantageous in terms of raw material costs.

[0014] (4) Fluorine gas process WO2007125972 discloses a process for producing hexafluorobutadiene using butadiene as a raw material, the main steps of which are as follows: first, 1,3-butadiene is reacted with chlorine gas to produce 1,2,3,4-tetrachlorobutane, then 1,2,3,4-tetrachlorobutane is reacted with fluorine gas in the gas phase in the absence of a catalyst and using an inert gas as a carrier gas to produce 1,2,3,4-tetrachlorohexafluorobutane, and finally, 1,2,3,4-tetrachlorohexafluorobutane is reacted with zinc powder in a solvent to obtain hexafluorobutadiene.

[0015] In view of the shortcomings of the prior art, it is necessary to provide a method and production system for producing hexafluorobutadiene that is low cost, has a high product purity, and allows safe, continuous, and stable production. Summary of the Invention [Problem to be solved by the invention]

[0016] An object of the present invention is to provide a method and system for producing hexafluorobutadiene, and to realize safe, stable, and reliable production of hexafluorobutadiene.

[0017] The technical route of the present invention is as follows:

[0018] [ka] [Means for solving the problem]

[0019] According to the first aspect of the present invention to achieve the object of the present invention, the present invention adopts the following technical solution:

[0020] A method for producing hexafluorobutadiene, the method comprising the steps of:

[0021] Step (1), an organic solution of bromotrifluoroethylene and zinc powder are introduced into a first reactor containing an initiator, zinc powder, and an organic solvent, and reacted to obtain a trifluorovinylzinc bromide solution; the trifluorovinylzinc bromide solution and zinc powder are introduced into a second reactor containing zinc powder, an initiator, and a first organic solvent, and unreacted bromotrifluoroethylene is completely converted; the reaction solution is introduced into a precipitator to separate excess zinc powder, and a trifluorovinylzinc bromide solution from which zinc powder has been removed is obtained; the first organic solvent is selected from polar aprotic organic solvents; Step (2), the zinc powder-removed trifluorovinylzinc bromide solution obtained in step (1) and the pre-prepared composite catalyst organic solution are introduced into a third reactor for coupling reaction to obtain a synthesis solution containing crude hexafluorobutadiene, the composite catalyst organic solution comprising an oxidant, a co-catalyst, and a second organic solvent, the co-catalyst being selected from monovalent copper salts and ferrous salts, and the second organic solvent being selected from polar aprotic organic solvents; Step (3) is to introduce the synthesis solution obtained in step (2) into a purification system to obtain a purified hexafluorobutadiene product.

[0022] The steps for preparing the bromotrifluoroethylene solution are as follows:

[0023] Step A: Add exactly the same kind of solvent (water content ≦500 ppm) as that in the first reactor to the bromotrifluoroethylene solution preparation vessel; In step B, a certain amount of bromotrifluoroethylene is then poured in, the temperature inside the vessel is limited to -10 to 10°C, and the mass concentration of the solution is 5 to 30%. Preferably, the temperature inside the vessel is limited to 0 to 5°C, and the mass concentration of the solution is 15 to 20%.

[0024] The specific steps for preparing the trifluorovinyl zinc bromide solution are as follows:

[0025] Step A: first, add an organic solvent, an initiator and zinc powder to a first reactor, and heat the mixture to a certain temperature while stirring; simultaneously add a solvent, an initiator and zinc powder to a second reactor, and heat the mixture to a certain temperature while stirring; open the overflow valve of the first reactor, so that the material in the first reactor can overflow into the second reactor; In step B, the organic solution of bromotrifluoroethylene and zinc powder are continuously added to the first reactor, zinc powder is continuously added to the second reactor, the overflow valve of the second reactor is opened, and the material in the second reactor can be overflowed or pumped into a precipitator to obtain a trifluorovinylzinc bromide solution free of zinc powder. The precipitator includes multiple settling tanks, preferably two-stage settling tanks, and the trifluorovinylzinc bromide solution prepared in step (1) is fed into the first settling tank by overflow or pumping, and the overflow valve or pump of the first settling tank is opened, and the material in the first settling tank can be overflowed or pumped into the second settling tank to obtain a trifluorovinylzinc bromide solution free of zinc powder. A pressure filtration tank may be used as the precipitation tank, and excess zinc powder may be precipitated on the baffle plate of the precipitation tank to obtain a trifluorovinyl zinc bromide solution free of residual zinc powder. The zinc powder in the precipitation tank may be subjected to pressure filtration and then directly used in the reaction for preparing the trifluorovinyl zinc bromide solution.

[0026] The initiator is one or more selected from bromomethane, 1,2-dibromoethane, iodine alone, chlorotrimethylsilane, and trifluorovinyl zinc bromide solution, and the molar ratio of the supply rate of bromotrifluoroethylene (mol / h) to the amount of base initiator used (mol) is 1:(1 to 100).

[0027] Preferably, the initiator is one selected from 1,2-dibromoethane, iodine alone, and a trifluorovinyl zinc bromide reagent solution, and the molar ratio of the supply rate (mol / h) of bromotrifluoroethylene to the amount (mol) of the base initiator used is 1:(1 to 50). More preferably, the initiator is a trifluorovinyl zinc bromide reagent solution.

[0028] In the process of preparing the trifluorovinyl zinc bromide solution, the ratio of the feed rate of the bromotrifluoroethylene organic solution in kg / h to the mass of the base material of the first reactor in kg is 1:(10-100), and the ratio of the feed rate of the bromotrifluoroethylene organic solution in kg / h to the mass of the base material of the second reactor in kg is 1:(5-100).

[0029] Preferably, the ratio of the feed rate of the bromotrifluoroethylene organic solution in kg / h to the mass of the base feedstock of the first reactor in kg is 1:(10-50), and the ratio of the feed rate of the bromotrifluoroethylene organic solution in kg / h to the mass of the base feedstock of the second reactor in kg is 1:(10-50).

[0030] In the process of preparing the trifluorovinyl zinc bromide solution, the molar ratio of bromotrifluoroethylene to the supply rate of zinc powder in the first reactor is 1: (1.0-5.0), and the molar ratio of bromotrifluoroethylene to the supply rate of zinc powder in the second reactor is 1: (0.1-2.0).

[0031] Preferably, during the reaction process, the molar ratio of the supply rate of bromotrifluoroethylene to the supply rate of zinc powder in the first reactor is 1:(1.0-3.0), and the molar ratio of the supply rate of bromotrifluoroethylene to the supply rate of zinc powder in the second reactor is 1:(0.1-1.0).

[0032] In the process of preparing the trifluorovinyl zinc bromide solution in step (1), the mesh size of the zinc powder is 100-500 mesh.

[0033] Preferably, the mesh size of the zinc powder is 200 to 400 mesh.

[0034] In the step (1) of preparing the trifluorovinyl zinc bromide solution, the organic solvent is selected from polar aprotic organic solvents, and the polar aprotic organic solvent is one, two or a combination of three or more selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide and N-methylpyrrolidone, and the water content of the polar aprotic organic solvent is ≦500 ppm.

[0035] Preferably, the polar aprotic organic solvent in step (1) is one, two or a combination of three or more selected from N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide, and the water content of the polar aprotic organic solvent is ≦200 ppm.

[0036] In the process of preparing the trifluorovinyl zinc bromide solution in step (1), the temperature range of the first reactor is 60 to 120°C, and the temperature range of the second reactor is 60 to 90°C.

[0037] Preferably, the first reactor temperature range is 60-90°C and the second reactor temperature range is 60-70°C.

[0038] In the process of preparing hexafluorobutadiene in step (2), the oxidizing agent is one or more selected from sodium peroxide, potassium peroxide, sodium perborate, sodium persulfate, potassium persulfate, ammonium persulfate, and di-tert-butyl peroxide; the co-catalyst is one or more selected from cuprous chloride, cuprous bromide, cuprous iodide, ferrous chloride, and ferrous bromide; and the polar aprotic organic solvent is one or more selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0039] Preferably, in the process of preparing hexafluorobutadiene in step (2), the oxidizing agent is selected from ammonium perborate, sodium persulfate, and potassium persulfate, the auxiliary is one or more selected from cuprous iodide and ferrous chloride, and the polar aprotic organic solvent is one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0040] In the process of preparing hexafluorobutadiene in step (2), the molar ratio of trifluorovinyl zinc bromide to oxidant is 1:(1.0~3.0). In the trifluorovinyl zinc bromide solution, the molar ratio of trifluorovinyl zinc bromide to cocatalyst is 1:(0.01~0.2).

[0041] Preferably, the molar ratio of trifluorovinyl zinc bromide to the oxidizing agent is 1: (1.0-1.5). In the trifluorovinyl zinc bromide solution, the molar ratio of trifluorovinyl zinc bromide to the co-catalyst is 1: (0.01-0.05).

[0042] In the process of preparing hexafluorobutadiene in step (2), the coupling reaction temperature is −10 to 50° C., the reaction pressure is 0 to 0.5 MPa, and the residence time in the reactor is 10 to 600 seconds.

[0043] Preferably, the temperature of the coupling reaction is 0 to 10° C., the reaction pressure is 0 to 0.2 MPa, and the residence time in the reactor is 50 to 300 seconds.

[0044] In step (3), the purification system is preferably a combination of a distillation apparatus and a rectification apparatus. After the reaction is completed, the reaction liquid is introduced into the distillation apparatus, and the product is immediately distilled and then rectified to obtain a high-purity hexafluorobutadiene product.

[0045] The content of bromotrifluoroethylene, which is a difficult-to-separate impurity, in the crude hexafluorobutadiene obtained by distillation is ≦0.1%, and the content of heptafluorobutene is ≦0.01%, and the purity of the product after rectification is ≧99.9%.

[0046] According to the second aspect of the present invention, the present invention adopts the following technical solution:

[0047] A production system for producing hexafluorobutadiene, the production system being used in the above-mentioned production method, comprising: a trifluorovinyl zinc bromide solution preparation unit; a hexafluorobutadiene preparation unit; a zinc powder filtration unit; a distillation unit; and a rectification unit; The trifluorovinylzinc bromide solution preparation unit comprises a bromotrifluoroethylene organic solution supply device, a zinc powder supply device, a solvent and initiator supply device, a first reactor, and a second reactor, wherein the bromotrifluoroethylene organic solution supply device, the zinc powder supply device, and the solvent and initiator supply device are connected to and supplied to the first reactor, and the zinc powder supply device, the solvent and initiator supply device are connected to and supplied to the second reactor, the first reactor is connected to the second reactor, and is used to send the trifluorovinylzinc bromide solution obtained by the reaction in the first reactor to the second reactor, the tops of the first reactor and the second reactor are connected to a vacuum device and a high-purity nitrogen device, respectively, via a condenser, and the outlet of the second reactor is connected to a zinc powder precipitation device, The hexafluorobutadiene preparation unit includes a trifluorovinyl zinc bromide solution supply device, a composite catalyst solution supply device, and a third reactor, and the trifluorovinyl zinc bromide solution supply device and the composite catalyst solution supply device are connected to the inlet end of the third reactor; The distillation unit includes a hexafluorobutadiene synthesis liquid supply device, a distillation device, and a product collection device; The rectification unit includes a hexafluorobutadiene crude product supply device, a rectification column, a fore distillate storage tank, a product collection tank, and a rectification bottoms storage tank.

[0048] The material of each equipment in the trifluorovinyl zinc bromide solution preparation unit is one selected from enameled glass, carbon steel, 316L, and fluororesin-lined carbon steel; the material of the equipment in the zinc powder filtration unit is one selected from carbon steel, 304, and 316L; and the material of the equipment in the distillation unit is one selected from enameled glass, 304, and 316L.

[0049] Furthermore, the first reactor and the second reactor are equipped with a stirring device, and the type of the stirring blade is selected from a propeller-type stirring blade; and the distillation apparatus is equipped with a stirring device, and the type of the stirring blade is selected from an anchor-type stirring blade. [Effects of the Invention]

[0050] The beneficial effects of the present invention are as follows:

[0051] (1) In the preparation of trifluorovinyl zinc bromide, a two-stage series reactor is used, which not only achieves almost complete conversion of the raw material bromotrifluoroethylene, but also improves the utilization rate of the raw material, reduces the workload of subsequent product rectification and purification, and helps improve the purity of the product.

[0052] (2) In the step of preparing hexafluorobutadiene by oxidative coupling, inexpensive peroxide is used as the oxidizing agent and a catalytic amount of copper salt or iron salt is used as the auxiliary agent, which significantly reduces raw material costs and reduces the discharge of heavy metal solid waste, thereby mitigating the environmental burden compared to conventional processes that use equivalent amounts of copper salt or iron salt.In addition, the use of inorganic peroxide as the oxidizing agent can reduce the generation of fluorine-containing olefins, which are difficult to separate impurities, compared to metal chloride oxidizing agents, and helps improve the purity of the product. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 is a schematic diagram of a trifluorovinyl zinc bromide solution preparation unit and a zinc powder filtration unit in an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a hexafluorobutadiene preparation unit and a distillation unit in an embodiment of the present invention. [Figure 3] FIG. 3 is a chromatogram of the hexafluorobutadiene product produced in Example 15 of the present invention. [Explanation of symbols]

[0054] The above figures include the following reference numerals: 1. Bromotrifluoroethylene solution storage tank 2. Initiator or solvent storage tank 3. First reactor 4. Second reactor 5. No. 1 zinc powder storage tank 6. Second zinc powder storage tank 7. First condenser 8. Second condenser 9. First settling tank 10. Second settling tank 11. First trifluorovinyl zinc bromide solution storage tank 12. Second trifluorovinyl zinc bromide solution storage tank 13. Composite catalyst solution storage tank 14. Third reactor 15. Hexafluorobutadiene synthetic liquid buffer tank 16. First distillation apparatus 17. Second distillation apparatus 18. Third condenser 19. Fourth condenser 20. First hexafluorobutadiene buffer tank 21. First hexafluorobutadiene crude product tank 22. 5th condenser 23. 6th condenser 24. Second hexafluorobutadiene buffer tank 25. Second hexafluorobutadiene crude product tank 26. Distillation residual liquid storage tank DETAILED DESCRIPTION OF THE INVENTION

[0055] The present invention will be further described below in connection with specific examples, but the present invention is not limited to these specific embodiments. It should be understood by those skilled in the art that the present invention encompasses all possible forms, modifications, and equivalents that may fall within the scope of the claims.

[0056] First, a production system for realizing the production of hexafluorobutadiene according to the present invention will be described with reference to the drawings.

[0057] The production system for producing hexafluorobutadiene includes a trifluorovinyl zinc bromide solution preparation unit, a hexafluorobutadiene preparation unit, a zinc powder filtration unit, a distillation unit, and a rectification unit; The trifluorovinyl zinc bromide solution preparation unit includes a bromotrifluoroethylene organic solution supply device, a zinc powder input device, a solvent and initiator input device, a first reactor 3, and a second reactor 4.

[0058] The bromotrifluoroethylene organic solution supply device includes a bromotrifluoroethylene solution storage tank 1, and the solvent and initiator supply device includes an initiator or solvent storage tank 2, each of which supplies materials to a corresponding supply site in the upper part of the first reactor 3 by pumping or gravity. The zinc powder supply device includes a first zinc powder storage tank 5 that supplies materials by gravity. The first reactor 3 is connected to the second reactor 4, and delivers the trifluorovinyl zinc bromide solution obtained by the reaction in the first reactor 3 to the second reactor 4. The second reactor 4 is further connected to a zinc powder supply device, which may be a second zinc powder storage tank 6 that supplies materials by gravity. The upper portions of the first reactor 3 and the second reactor 4 are connected to a vacuum device via a first condenser 7 and a second condenser 8, respectively. The outlet of the second reactor 4 is connected to the zinc powder filtration unit, which may adopt two-stage precipitation tanks, namely a first precipitation tank 9 and a second precipitation tank 10, respectively. The outlet of the second precipitation tank 10 is connected to a first trifluorovinyl zinc bromide solution storage tank 11, which may serve as a material buffer for production.

[0059] The hexafluorobutadiene preparation unit includes a trifluorovinyl zinc bromide solution supply device, a composite catalyst solution supply device, and a third reactor 14. The third reactor 14 is a tubular reactor, and the trifluorovinyl zinc bromide solution supply device and the composite catalyst solution supply device are connected to the inlet end of the third reactor. The trifluorovinyl zinc bromide solution supply device includes a second trifluorovinyl zinc bromide solution reservoir 12, and the second trifluorovinyl zinc bromide solution reservoir 12 and the first trifluorovinyl zinc bromide solution reservoir 11 can be the same. The trifluorovinyl zinc bromide solution supply device pumps materials to the third reactor 14. The composite catalyst solution supply device includes a composite catalyst solution reservoir 13 and pumps materials to the third reactor 14.

[0060] The distillation unit includes a hexafluorobutadiene synthesis liquid supply device, a distillation device, and a product collection device. A hexafluorobutadiene synthesis liquid buffer tank 15 may be connected to the outlet end of the third reactor 14.

[0061] The distillation unit includes a hexafluorobutadiene synthesis liquid supply device, a distillation device, and a product collection device.

[0062] The hexafluorobutadiene synthesis liquid supply system includes a hexafluorobutadiene synthesis liquid buffer tank 15, which pumps the material to supply two parallel purification systems. The first purification system includes a first distillation apparatus 16, which is connected to a first hexafluorobutadiene buffer tank 20 via a third condenser 18, and the first hexafluorobutadiene buffer tank 20 is connected to a first hexafluorobutadiene crude product tank 21 via a fourth condenser 19. The second purification system includes a second distillation apparatus 17, which is connected to a second hexafluorobutadiene buffer tank 24 via a fifth condenser 22, and the second hexafluorobutadiene buffer tank 24 is connected to a second hexafluorobutadiene crude product tank 25 via a sixth condenser 23. The second hexafluorobutadiene crude product tank 25 is further connected to a rectification system. In the figure, reference numeral 26 denotes a distillation residue storage tank.

[0063] In the following examples, the above production system is used.

[0064] Example 1 (1) 300 kg of an N,N-dimethylformamide solution of trifluorovinyl zinc bromide with a mass fraction of 25% was added to a 500 L first reactor made of 316 L material, stirring was started, 65 kg of zinc powder was added, and the reactor was heated to 80°C.

[0065] (2) 300 kg of an N,N-dimethylformamide solution of trifluorovinyl zinc bromide with a mass fraction of 25% was added to a 500 L second reactor made of 316 L material, stirring was started, 32.5 kg of zinc powder was added, and the reactor was heated to 60°C.

[0066] (3) A solution of bromotrifluoroethylene in N,N-dimethylformamide (mass fraction 20%) was added to the first reactor, and the flow rate was limited to 15 kg / h. At the same time, zinc powder (325 mesh, 1.3 kg / h) was added to the first reactor using a solid feed facility.

[0067] (4) The overflow valve connected to the second reactor of the first reactor was opened, and the material in the first reactor entered the second reactor when the liquid level exceeded the height of the overflow valve. At the same time, zinc powder (325 mesh, 0.35 kg / h) was added to the second reactor using the solid supply equipment.

[0068] (5) The overflow valve to the first settling tank of the second reactor was opened, and when the liquid level in the second reactor exceeded the height of the overflow valve, the material entered the first settling tank, and the excess zinc powder was precipitated on the baffle plate during the reaction.

[0069] (6) The connecting valve of the first settling tank to the second settling tank was opened, and when the liquid level of the material in the first settling tank exceeded the height of the valve outlet, the material transport pump was opened to transport the material to the second settling tank, and the remaining zinc powder was allowed to settle on the baffle plate.

[0070] (7) The connection valve between the second settling tank and the trifluorovinyl zinc bromide solution storage tank was opened, and when the liquid level in the second settling tank exceeded the height of the valve outlet, the material transport pump was opened to transport the material to the storage tank. After 72 hours of operation, sampling and analysis of the trifluorovinyl zinc bromide solution storage tank yielded the following results: the normalized content of bromotrifluoroethylene was 0.005% by area percentage, the mass fraction of trifluorovinyl zinc bromide was 25.1% (using the fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 96.5%.

[0071] Example 2 The operation of this example was the same as in Example 1, with the following differences: the bromotrifluoroethylene N,N-dimethylformamide solution (20% by mass) at a flow rate of 15 kg / h was replaced with an N,N-dimethylformamide solution (20% by mass) at a flow rate of 20 kg / h; the addition of zinc powder (325 mesh, 1.3 kg / h) to the first reactor was replaced with zinc powder (325 mesh, 1.8 kg / h) to the first reactor; and the addition of zinc powder (325 mesh, 0.35 kg / h) to the second reactor was replaced with zinc powder (325 mesh, 0.48 kg / h) to the second reactor, with the other conditions remaining unchanged. After 72 hours of operation, a sample was taken from the trifluorovinyl zinc bromide solution storage tank and analyzed, with the following results: The area percentage content of bromotrifluoroethylene was 0.008%, the mass fraction of trifluorovinylzinc bromide was 24.4% (fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 93.8%.

[0072] Example 3 The procedure of this example was the same as in Example 1, with the only difference being that adding zinc powder (325 mesh, 0.35 kg / h) to the second reactor was replaced by adding zinc powder (325 mesh, 0.20 kg / h) to the second reactor.

[0073] Other conditions were not changed. After 72 hours of operation, a sample was taken from the trifluorovinyl zinc bromide solution storage tank and analyzed, yielding the following results: the bromotrifluoroethylene content by area percentage method was 0.006%, the mass fraction of trifluorovinyl zinc bromide was 24.7% (fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 95.0%.

[0074] Example 4 The procedure of this example was the same as that of Example 1, with the only difference being that the mesh size of the zinc powder was changed from 325 mesh to 500 mesh, with other conditions remaining unchanged. After 72 hours of operation, a sample was taken from the trifluorovinylzinc bromide solution storage tank and analyzed, with the following results: the bromotrifluoroethylene content by area percentage method was 0.01%, the mass fraction of trifluorovinylzinc bromide was 22.2% (using the fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 85.3%.

[0075] Example 5 The procedure of this example was the same as that of Example 1, with the only difference being that the temperature of the first reactor was changed from 80°C to 60°C, with other conditions remaining unchanged. After 72 hours of operation, a sample was taken from the trifluorovinyl zinc bromide solution storage tank and analyzed, with the following results: the bromotrifluoroethylene content by area percentage method was 0.012%, the mass fraction of trifluorovinyl zinc bromide was 21.7% (fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 83.3%.

[0076] Example 6 The procedure of this example was the same as that of Example 1, with the only difference being that the temperature of the second reactor was changed from 60°C to 70°C, with other conditions remaining unchanged. After 72 hours of operation, a sample was taken from the trifluorovinyl zinc bromide solution storage tank and analyzed, with the following results: the bromotrifluoroethylene content by area percentage method was 0.005%, the mass fraction of trifluorovinyl zinc bromide was 24.9% (fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 95.8%.

[0077] Example 7 The operation of this example was the same as in Example 1, with the only difference being the following: instead of feeding a 25% mass fraction N,N-dimethylformamide solution of trifluorovinylzinc bromide into the first and second reactors, a 25% mass fraction N,N-dimethylacetamide solution of trifluorovinylzinc bromide was fed into the first and second reactors; instead of feeding a 20% mass fraction N,N-dimethylformamide solution of bromotrifluoroethylene into the first reactor, a 20% mass fraction N,N-dimethylacetamide solution of bromotrifluoroethylene was fed into the first reactor, with the other conditions remaining unchanged. After 72 hours of operation, a sample was taken from the trifluorovinylzinc bromide solution storage tank and analyzed, yielding the following results: The area percentage content of bromotrifluoroethylene was 0.007%, the mass fraction of trifluorovinylzinc bromide was 23.9% (fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 91.9%.

[0078] Example 8 The operation of this example was the same as that of Example 1, with the only difference being that the zinc powder was replaced with zinc powder recovered from the first settling tank, with other conditions remaining unchanged. After 72 hours of operation, a sample was taken from the trifluorovinylzinc bromide solution storage tank and analyzed, yielding the following results: the bromotrifluoroethylene content by area percentage was 0.006%, the mass fraction of trifluorovinylzinc bromide was 24.3% (using the fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 93.5%.

[0079] (Comparative Example 1) The trifluorovinyl zinc bromide solution was prepared by reaction in a single reactor, and the operating steps were as follows:

[0080] (1) 300 kg of an N,N-dimethylformamide solution of trifluorovinyl zinc bromide with a mass fraction of 25% was added to a 500 L first reactor made of 316 L material, stirring was started, 65 kg of zinc powder was added, and the reactor was heated to 80°C.

[0081] (2) A solution of bromotrifluoroethylene in N,N-dimethylformamide (mass fraction 20%) was added to the first reactor, and the flow rate was limited to 15 kg / h. At the same time, zinc powder (325 mesh, 1.3 kg / h) was added to the first reactor using a solid feed facility.

[0082] (3) The overflow valve to the first settling tank of the first reactor was opened, and when the liquid level in the second reactor exceeded the height of the overflow port, the material entered the first settling tank, and the excess zinc powder from the reaction was precipitated on the baffle plate.

[0083] (4) The connecting valve of the first settling tank to the second settling tank was opened, and when the liquid level of the material in the first settling tank exceeded the height of the valve outlet, the material transport pump was opened to transport the material to the second settling tank, and the remaining zinc powder was allowed to settle on the baffle plate.

[0084] (5) The connection valve between the second settling tank and the trifluorovinyl zinc bromide solution storage tank was opened, and when the liquid level in the second settling tank exceeded the height of the valve outlet, the material transport pump was opened and the material was transported to the storage tank. After 72 hours of operation, sampling and analysis of the trifluorovinyl zinc bromide solution storage tank yielded the following results: the bromotrifluoroethylene content by area percentage was 1.56%, the trifluorovinyl zinc bromide mass fraction was 20.2% (using the fluorine nuclear magnetic resonance internal standard method), the theoretical mass fraction was 26%, and the average yield was 77.8%.

[0085] Example 9 (1) 300 kg of N,N-dimethylformamide was added to a 500 L enamel glass reaction vessel, and ammonium persulfate (40 kg, 175 mol) and cuprous iodide (0.67 kg, 3.5 mol) were added while stirring. The internal temperature was maintained at 0-5°C, and the preparation of the oxidant solution was completed. The oxidant concentration was 0.51 mol / kg, and the auxiliary concentration was 0.01 mol / kg.

[0086] (2) The oxidant solution prepared above (flow rate: 40 kg / h, corresponding to a flow rate of ammonium persulfate of 20.4 mol / h and a flow rate of cuprous iodide of 0.4 mol / h) and a trifluorovinyl zinc bromide solution (mass fraction: 25%, flow rate: 16.8 kg / h, corresponding to a flow rate of trifluorovinyl zinc bromide of 18.6 mol / h) were added to a 316 L spiral tube reactor (total length: 10 m, tube inner diameter: 8 mm), the internal temperature was limited to 0 to 5°C, and the pressure inside the reaction tube was 0.05 MPa.

[0087] (3) The synthesis liquid was fed from the outlet of the reaction tube into distillation apparatus A or B. The temperature inside the vessel was 60°C, the degree of vacuum inside the vessel was 0.1 MPa, and the crude hexafluorobutadiene was collected by condensation after the vacuum pump, with the condenser temperature being -15°C. After 72 hours of operation, the results were as follows: 107.6 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main component content of 95.33% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 102.6 kg, with a theoretical yield of 108.5 kg and an average yield of 94.6%.

[0088] Example 10 The procedure of this example was the same as in Example 9, with the only difference being the following: the oxidant solution prepared above (flow rate: 60 kg / h, corresponding to a flow rate of 30.6 mol / h of ammonium persulfate and a flow rate of 0.6 mol / h of cuprous iodide) and the trifluorovinyl zinc bromide solution (mass fraction: 25%, flow rate: 25.2 kg / h, corresponding to a flow rate of 27.9 mol / h of trifluorovinyl zinc bromide) were added, and other conditions were unchanged. After 72 hours of operation, the results were as follows: 156.1 kg of hexafluorobutadiene crude product was collected from the crude product tank after pumping, with a major component content of 95.81% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 149.5 kg, with a theoretical yield of 162.8 kg and an average yield of 91.8%.

[0089] Example 11 The procedure of this example was the same as that of Example 9, with the only difference being that in step (1), ammonium persulfate (40 kg, 0.175 kmol) was replaced with potassium persulfate (40 kg, 0.148 kmol), the oxidant concentration was 0.43 mol / kg, and the co-reagent concentration was 0.01 mol / kg.

[0090] In step (2), the oxidant solution (flow rate: 40 kg / h, corresponding to a flow rate of 20.4 mol / h of ammonium persulfate and a flow rate of 0.4 mol / h of cuprous iodide) was replaced with an oxidant solution (flow rate: 47.4 kg / h, corresponding to a flow rate of 20.4 mol / h of potassium persulfate and a flow rate of 0.4 mol / h of cuprous iodide), while other conditions remained unchanged. After 72 hours of operation, the results were as follows: 104.3 kg of hexafluorobutadiene crude product was collected from the crude product tank after pumping, with a major component content of 93.80% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 97.8 kg, a theoretical yield of 108.5 kg, and an average yield of 90.1%.

[0091] Example 12 The procedure of this example was the same as that of Example 9, with the only difference being that in step (1), cuprous iodide (0.67 kg, 3.5 mol) was replaced with ferrous chloride (0.70 kg, 3.5 mol). Other conditions were unchanged. After 72 hours of operation, the results were as follows: 109.4 kg of hexafluorobutadiene crude product was collected from the crude product tank after pumping, with a major component content of 94.68% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 103.6 kg, with a theoretical yield of 108.5 kg and an average yield of 95.5%.

[0092] Example 13 The procedure of this example was the same as that of Example 9, with the only difference being the following: In step (1), cuprous iodide (0.67 kg, 3.5 mol) was replaced with cuprous iodide (1.33 kg, 7.0 mol), completing the preparation of the oxidant solution. The auxiliary agent concentration was changed from 0.01 mol / kg to 0.02 mol / kg. In step (2), the flow rate of cuprous iodide was changed from 0.4 mol / h to 0.8 mol / h. Other conditions were unchanged. After 72 hours of operation, the results were as follows: 107.4 kg of hexafluorobutadiene crude product was collected from the crude product tank after pumping, with a major component content of 95.02% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 102.0 kg, with a theoretical yield of 108.5 kg and an average yield of 94.0%.

[0093] Example 14 The procedure of this example was the same as that of Example 9, with the only difference being that the internal temperature was maintained at 5 to 10°C instead of 0 to 5°C, and the internal temperature in step (2) was limited to 5 to 10°C instead of 0 to 5°C, but the other conditions were unchanged. After 72 hours of operation, the results were as follows: 107.1 kg of hexafluorobutadiene crude product was collected from the crude product tank after the pump, and the content of the main component was 94.25% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 100.9 kg, the theoretical yield was 108.5 kg, and the average yield was 93.0%.

[0094] (Comparative Example 2) The procedure of this example was the same as that of Example 9, with the only difference being that the auxiliary agent, cuprous iodide, was not added during the preparation of the oxidant solution in step (1), and other conditions were unchanged. After 72 hours of operation, the results were as follows: 10.7 kg of hexafluorobutadiene crude product was collected from the crude product tank after pumping, with a major component content of 66.51% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 7.1 kg, with a theoretical yield of 108.5 kg and an average yield of 6.5%.

[0095] (Comparative Example 3) The procedure of this example was the same as that of Example 9, with the only difference being the following: In step (3), the hexafluorobutadiene synthesis liquid was distilled in an intermittent still, and the synthesis liquid after 72 hours of operation was charged into the distillation apparatus only once, with other conditions remaining unchanged. The results were as follows: 98.3 kg of hexafluorobutadiene crude product was collected from the crude product tank after the pump, with a main component content of 93.85% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 92.3 kg, with a theoretical yield of 108.5 kg and an average yield of 85.1%.

[0096] Comparative Example 4 The procedure of this example was the same as that of Example 9, with the only difference being that in the process of preparing the oxidant solution in step (1), the persulfate oxidant was replaced with an equimolar amount of iron salt oxidant, specifically as follows:

[0097] (1) 300 kg of N,N-dimethylformamide was added to a 500 L enamel glass reaction vessel, and ferric chloride (28.4 kg, 0.175 kmol) was added while stirring. The internal temperature was maintained at 0-5°C, and the preparation of the oxidant solution was completed. The oxidant concentration was 0.53 mol / kg.

[0098] (2) The oxidant solution prepared above (flow rate: 38.5 kg / h, corresponding to a ferric chloride flow rate of 20.4 mol / h) and the trifluorovinyl zinc bromide solution (mass fraction: 25%, flow rate: 16.8 kg / h, corresponding to a trifluorovinyl zinc bromide flow rate of 18.6 mol / h) were added to a 316 L spiral tube reactor (total length: 10 m, tube inner diameter: 8 mm), the internal temperature was limited to 0 to 5°C, and the pressure inside the reaction tube was 0.05 MPa.

[0099] Step (3) was the same as in Example 9, and the operation was carried out for 72 hours, with the following results: 102.7 kg of hexafluorobutadiene crude product was collected from the crude product tank after the pump, with a main component content of 88.52% (the contents of other impurities were as shown in Table 1 below). Converted to weight percentage, this was 90.9 kg, with a theoretical yield of 108.5 kg and an average yield of 83.8%.

[0100] [Table 1]

[0101] Example 15 A rectification experiment was carried out using the crude hexafluorobutadiene prepared in Example 9 as a raw material, and the rectification column parameters and rectification parameters were as shown in Tables 2 and 3 below.

[0102] [Table 2]

[0103] [Table 3] In the rectification, 100 kg was fed, and 22.6 kg of fore distillate was obtained, with 65.7 kg of product and 10.5 kg of bottoms. The product purity was 99.9908%, the rectification yield per batch was 65.7%, and the material balance rate was 98.8%. The chromatogram of the product after rectification is shown in Figure 3. The results are as follows:

[0104] Table 4

Claims

1. (1) a step of reacting an organic solution of bromotrifluoroethylene and zinc powder in a first reactor containing an initiator, zinc powder, and an organic solvent to obtain a trifluorovinyl zinc bromide solution, and then transferring the trifluorovinyl zinc bromide solution and zinc powder to a second reactor containing zinc powder, an initiator, and a first organic solvent to completely convert unreacted bromotrifluoroethylene, and then transferring the reaction solution to a precipitator to separate excess zinc powder to obtain a trifluorovinyl zinc bromide solution free of zinc powder, wherein the first organic solvent is selected from polar aprotic organic solvents; Step (2) of introducing the zinc powder-removed trifluorovinylzinc bromide solution obtained in step (1) and the pre-prepared composite catalyst organic solution into a third reactor for coupling reaction to obtain a synthesis solution containing crude hexafluorobutadiene, wherein the composite catalyst organic solution comprises an oxidant, a co-catalyst, and a second organic solvent, the co-catalyst being selected from monovalent copper salts and ferrous salts, and the second organic solvent being selected from polar aprotic organic solvents; and step (3) of introducing the synthesis liquid obtained in step (2) into a purification system to obtain purified hexafluorobutadiene.

2. The method for producing hexafluorobutadiene according to claim 1, wherein the initiator is one or more selected from the group consisting of bromomethane, 1,2-dibromoethane, iodine alone, chlorotrimethylsilane, and a trifluorovinyl zinc bromide reagent solution, preferably the initiator is one selected from the group consisting of 1,2-dibromoethane, iodine alone, and a trifluorovinyl zinc bromide reagent solution, and the molar ratio of the supply rate (mol / h) of the bromotrifluoroethylene to the amount (mol) of the base initiator used is 1:(1 to 50).

3. 3. The method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that the initiator is one or more selected from the group consisting of 1,2-dibromoethane, chlorotrimethylsilane, and the trifluorovinyl zinc bromide reagent solution, and the ratio of the supply rate of the bromotrifluoroethylene in mol / h to the molar amount of the base initiator used is 1:(1 to 100).

4. The mass concentration of the organic solution of bromotrifluoroethylene is 5%-30%, and during the reaction, the ratio of the feed rate of the bromotrifluoroethylene organic solution in kg / h to the mass of the base material of the first reactor in kg is 1:(10-100), preferably 1:(10-50), and the ratio of the feed rate of the bromotrifluoroethylene organic solution in kg / h to the mass of the base material of the second reactor in kg is 1:(5-100), preferably 1:(5-100). The method for producing hexafluorobutadiene according to any one of claims 1 to 3, wherein the molar ratio of the supply rate of the bromotrifluoroethylene to the supply rate of zinc powder in the first reactor is 1:(1.0-5.0), preferably 1:(1.0-3.0), and the molar ratio of the supply rate of the bromotrifluoroethylene to the supply rate of zinc powder in the second reactor is 1:(0.1-2.0), preferably 1:(0.1-1.0).

5. The method for producing hexafluorobutadiene according to any one of claims 1 to 4, characterized in that the mesh size of the zinc powder is 100 mesh to 500 mesh, preferably 200 mesh to 400 mesh, the polar aprotic organic solvent in step (1) is any one or more selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, and N-methylpyrrolidone, and the water content of the polar aprotic organic solvent is ≦500 ppm, preferably ≦200 ppm.

6. The method for producing hexafluorobutadiene according to any one of claims 1 to 5, wherein the temperature range of the first reactor is 60°C to 120°C, preferably 60°C to 90°C, and the temperature range of the second reactor is 60°C to 90°C, preferably 60°C to 70°C.

7. 7. The method for producing hexafluorobutadiene according to claim 1, wherein the precipitation device comprises a plurality of precipitation tanks.

8. The method for producing hexafluorobutadiene according to any one of claims 1 to 7, characterized in that the precipitation apparatus comprises two stages, which are a first precipitation tank and a second precipitation tank, respectively, and the trifluorovinyl zinc bromide solution prepared in step (1) is fed into the first precipitation tank and the second precipitation tank, in this order, by overflow or pumping, to precipitate excess zinc powder, thereby obtaining a trifluorovinyl zinc bromide solution free of residual zinc powder.

9. 9. The method for producing hexafluorobutadiene according to claim 7 or 8, wherein the zinc powder in the precipitation tank in step (1) can be directly used in the reaction for preparing trifluorovinyl zinc bromide solution after pressure filtration.

10. The method for producing hexafluorobutadiene according to any one of claims 1 to 9, wherein the oxidizing agent in the composite catalyst organic solution in step (2) is one or more selected from sodium peroxide, potassium peroxide, sodium perborate, sodium persulfate, potassium persulfate, ammonium persulfate, and di-tert-butyl peroxide; the co-catalyst is one or more selected from cuprous chloride, cuprous bromide, cuprous iodide, ferrous chloride, and ferrous bromide; and the polar aprotic organic solvent in step (2) is one or more selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, and N-methylpyrrolidone.

11. The method for producing hexafluorobutadiene according to any one of claims 1 to 10, characterized in that in step (2), the molar ratio of trifluorovinyl zinc bromide to oxidant is 1:(1.0 to 3.0), preferably 1:(1.0 to 1.5), and in the trifluorovinyl zinc bromide solution, the molar ratio of trifluorovinyl zinc bromide to co-catalyst is 1:(0.01 to 0.2), preferably 1:(0.01 to 0.05).

12. The method for producing hexafluorobutadiene according to any one of claims 1 to 11, wherein in step (2), the coupling reaction temperature is -10°C to 50°C, the reaction pressure is 0 MPa to 0.5 MPa, and the residence time in the reactor is 10 seconds to 600 seconds, and preferably, in step (2), the coupling reaction temperature is 0°C to 10°C, the reaction pressure is 0 MPa to 0.2 MPa, and the residence time in the reactor is 50 seconds to 300 seconds.

13. The method for producing hexafluorobutadiene according to any one of claims 1 to 12, characterized in that in the step (3), the synthesis liquid obtained in the step (2) is distilled to obtain crude hexafluorobutadiene, and the crude hexafluorobutadiene is further rectified to obtain pure hexafluorobutadiene.

14. 14. The method for producing hexafluorobutadiene according to claim 13, wherein the bromotrifluoroethylene content in the crude hexafluorobutadiene obtained by distillation is ≦0.1% and the heptafluorobutene content is ≦0.01%, and the purity of the product after rectification is ≧99.9%.

15. A production system for producing hexafluorobutadiene, which is used in the production method according to any one of claims 1 to 14, and which comprises a trifluorovinyl zinc bromide solution preparation unit, a hexafluorobutadiene preparation unit, a zinc powder filtration unit, a distillation unit, and a rectification unit; the trifluorovinyl zinc bromide solution preparation unit comprises a bromotrifluoroethylene organic solution supply device, a zinc powder input device, a solvent and initiator input device, a first reactor, and a second reactor, wherein the bromotrifluoroethylene organic solution supply device, the zinc powder input device, and the solvent and initiator input device are connected to the first reactor to supply materials thereto, the zinc powder input device, and the solvent and initiator input device are connected to the second reactor to supply materials thereto, the first reactor is connected to the second reactor, and is used to deliver the trifluorovinyl zinc bromide solution obtained by the reaction in the first reactor to the second reactor, the tops of the first reactor and the second reactor are connected to vacuum and high-purity nitrogen devices, respectively, via condensers, and the outlet of the second reactor is connected to a zinc powder precipitation device; The hexafluorobutadiene preparation unit includes a trifluorovinyl zinc bromide solution supply device, a composite catalyst solution supply device, and a third reactor, and the trifluorovinyl zinc bromide solution supply device and the composite catalyst solution supply device are connected to the inlet end of the third reactor; The distillation unit includes a hexafluorobutadiene synthesis liquid supply device, a distillation device, and a product collection device; The rectification unit comprises a hexafluorobutadiene crude product supply device, a rectification column, a preliminary fraction storage tank, a product collection tank, and a rectification residue storage tank.

16. 16. The production system for producing hexafluorobutadiene according to claim 15, wherein the material of each piece of equipment in the trifluorovinyl zinc bromide solution preparation unit and the hexafluorobutadiene preparation unit is one selected from enameled glass, carbon steel, 316L, and fluororesin-lined carbon steel; the material of the equipment in the zinc powder filtration unit is one selected from carbon steel, 304, and 316L; and the material of the equipment in the distillation unit is one selected from enameled glass, 304, and 316L.

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