Preparation method and production system for hexafluorobutadiene

Abstract

Disclosed in the present invention are a preparation method and a production system for hexafluorobutadiene. The preparation method comprises the following steps: step (1), respectively sequentially introducing an organic solution of bromotrifluoroethylene and zinc powder into a first reactor and a second reactor each filled with an initiator, zinc powder and an organic solvent for a reaction to obtain a trifluoroethylene zinc bromide solution, and then introducing the reaction solution to a sedimentation device to separate excessive zinc powder to obtain a zinc power-free trifluoroethylene zinc bromide solution, wherein the excessive zinc powder is filtered and then recycled; step (2), introducing the obtained trifluoroethylene zinc bromide solution and a pre-prepared composite catalyst solution into a third reactor for a coupling reaction to obtain a crude hexafluorobutadiene product; and step (3), purifying the obtained crude hexafluorobutadiene product to obtain a product having a purity more than or equal to 99.9%. The present invention has the advantages of a high bromotrifluoroethylene conversion rate, low coupling composite catalyst cost, mild reaction conditions, a high product purity, high safety, etc.

Description

A preparation method and production system of hexafluorobutadiene

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 12, 2023, with application number 202311705885.0. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the preparation of fluorine-containing electronic gas, and in particular to a preparation method and production system of hexafluorobutadiene. Technical Background

[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 100nm) for the production of rectifier circuit boards containing Cu and a low-K dielectric constant. It boasts better selectivity and aspect ratios than other etching gases. For example, compared to octafluorocyclobutane (c-C4F8), C4F6 has an etching aspect ratio of up to 10, while c-C4F8 has a ratio of only 3, making C4F6 suitable for extremely narrow linewidth processes. C4F6 only etches silicon oxide films, leaving photoresist, silicon films, and nitride films unaffected, resulting in excellent etching selectivity. Hexafluorobutadiene also has good environmental performance, with an ODP of 0, a GWP (100) of 290, and a lifetime in the atmosphere of only 1.9 days, making it a very low greenhouse effect, environmentally friendly etching gas. Therefore, with the development of the integrated circuit industry and the focus on greenhouse gases, hexafluorobutadiene, with its optimal etching performance and environmentally friendly properties, is bound to become a leading product and be widely used in the laser etching agent market.

[0004] The preparation process of hexafluorobutadiene has been one of the research hotspots in recent years, but few can actually achieve industrial production. The following reports on the preparation of hexafluorobutadiene are available in the prior art:

[0005] (1) Oxidative coupling process

[0006] The self-coupling route is based on the preparation of the key intermediate trifluorovinyl zinc halide (CF2=CFZnX), and then 3+ or Cu 2+ ions in the presence of self-coupling reaction to obtain hexafluorobutadiene. For example, WO 2006 / 026400 discloses using trifluorochloroethylene (CF2=CFCl) as raw material, through hydrodechlorination, bromination, dehydrobromination to prepare trifluoroethylene bromide (CF2=CFBr), then reacting with zinc powder to prepare trifluorovinyl zinc bromide (CF2=CFZnBr), and finally reacting with Fe 3+ or Cu 2+Hexafluorobutadiene is obtained through a self-coupling reaction in the presence of ions. Although this method uses relatively cheap materials, it involves multiple hazardous production processes, a long process, and the intermediate trifluoroethylene has the risk of self-polymerization, making it unsuitable for industrial scale-up production.

[0007] CN 104829415 discloses a process for preparing hexafluorobutadiene using tetrafluoroethane (HFC-134a) as a raw material. First, tetrafluoroethane reacts with bromine at high temperature to obtain 1,1-dibromotetrafluoroethane; then, it reacts with zinc powder in a polar aprotic solvent to prepare trifluorovinyl zinc bromide; and finally, the reaction is carried out in Fe 3+ Hexafluorobutadiene is obtained by self-coupling in the presence of an oxidizing agent, with an overall yield of 47%. This reaction uses the inexpensive refrigerant HFC-134a as a raw material, and the process route is relatively short. However, 1,1-dibromotetrafluoroethane has low reactivity, and the yield is low when reacted with zinc powder to prepare trifluorovinyl zinc bromide. This results in high unit costs, large amounts of three wastes, and low prospects for industrialization.

[0008] [Journal of Fluorine Chemistry 129(2008)443-446] reported the preparation of trifluorovinyl zinc chloride in a zinc chloride / tetrahydrofuran system using tetrafluoroethane (HFC-134a) as raw material and diisopropylamine (LDA) as hydrogen extraction reagent, and then 2+ or Fe 3+ Hexafluorobutadiene is obtained in a 69-70% yield. The raw material R134a is cheap and readily available, and the synthesis steps are simple, allowing for a one-pot synthesis. However, the first step requires the strong base lithium diisopropylamide (LDA), which is expensive and the production process is highly hazardous, making industrial feasibility difficult.

[0009] JP 2001114710 reports a process for synthesizing hexafluorobutadiene using tetrafluoroethylene as a raw material. First, tetrafluoroethylene is reacted with bromine to produce 1,2-dibromotetrafluoroethane. Second, 1,2-dibromotetrafluoroethane is rearranged under Lewis acid catalysis to produce 1,1-dibromotetrafluoroethane. Third, 1,1-dibromotetrafluoroethane is reacted with zinc powder to produce trifluoroethylene zinc bromide. Finally, trifluoroethylene zinc bromide is reacted with Cu 2CO 3 ions. 2+ or Fe 3+ The target product hexafluorobutadiene is obtained by self-coupling in the presence of a catalyst. The reaction conditions of this process are relatively mild and the raw material cost is relatively low, but the overall yield of this process is low (<50%), and tetrafluoroethylene is used as the raw material, which limits its industrialization.

[0010] (2) Dehalogenation process

[0011] The dehalogenation process involves obtaining an intermediate tetrahalohexafluorobutane (XCF2-CFX-CFX-CF2X) through telomerization or intermolecular dehalogenation, which is then reacted with zinc powder in an alcoholic solvent to produce hexafluorobutadiene. US Pat. No. 304,630 discloses a method for preparing perfluorobutadiene using chlorotrifluoroethylene as a raw material. The chlorotrifluoroethylene first reacts with iodine chloride (ICl) in a sealed system at 35-40°C to produce 1,2-dichloro-1,2,2-trifluoroiodoethane. This is then coupled with an equivalent amount of mercury under ultraviolet light to produce 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane. Finally, the 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane is dechlorinated in the presence of zinc powder in an alcoholic solvent to produce hexafluorobutadiene. This method requires chemically equivalent amounts of iodine chloride and mercury to react, resulting in mercuric iodide as one of the products, which is highly toxic and requires expensive reagents.

[0012] CN106336342 improves this process by using a zinc powder / acetic anhydride system for intermolecular coupling, avoiding the use of highly toxic mercury as a raw material. The process conditions are relatively mild, and the yield of the three-step reaction is high (90%). However, it still requires expensive iodine as a raw material, making it unsuitable for large-scale production.

[0013] US2894043 discloses the dimerization of 1,2-dichlorodifluoroethylene (CFCl=CFCl) in the presence of fluorine gas to produce 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 temperatures (-70°C) and the use of the highly hazardous gas F2 during the fluorination and dimerization stages. US2676193 improved this method, but the reaction still required high temperatures (300°C) and high pressures (12 MPa). The reaction yield was low, at only 30-40%, and numerous byproducts were produced, making product separation difficult.

[0014] RU0118462 reports a route for synthesizing hexafluorobutadiene using chlorotrifluoroethylene as a raw material, avoiding the use of highly toxic mercury and expensive iodine reagents. Chlorotrifluoroethylene is first dimerized at high temperature 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 directly dechlorinated with zinc powder to yield the target product, hexafluorobutadiene. This method has the advantage of requiring only two reaction steps to produce C4F6, a relatively short process. However, separation of the dimerization product requires a demanding fractional distillation process, which increases production costs. Furthermore, the yield of the target intermediate, even after the improvement, remains less than 30%.

[0015] (3) Catalytic coupling process

[0016] WO 2018235883 discloses a catalytic self-coupling reaction using trifluorochloroethylene as a raw material in the presence of a palladium catalyst, a phosphorus ligand, and zinc powder to obtain hexafluorobutadiene, with a maximum yield of 86.1%. CN 116693365 discloses a cross-coupling reaction using trifluorochloroethylene and trifluoroethylene as raw materials in the presence of an active palladium catalyst and a basic compound to obtain hexafluorobutadiene, with a maximum reaction yield of 83%. Although this method is simple, it uses expensive palladium as a catalyst, which does not offer advantages in terms of raw material costs.

[0017] (4) Fluorine gas process

[0018] WO2007125972 discloses a process for preparing hexafluorobutadiene using butadiene as a raw material. The main steps are: first, 1,3-butadiene reacts with chlorine to produce 1,2,3,4-tetrachlorobutane; second, in the absence of a catalyst, using an inert gas as a carrier gas, 1,2,3,4-tetrachlorobutane reacts with fluorine in the gas phase to produce 1,2,3,4-tetrachlorohexafluorobutane; finally, 1,2,3,4-tetrachlorohexafluorobutane reacts with zinc powder in a solvent to produce hexafluorobutadiene.

[0019] In view of the shortcomings of the existing technology, it is necessary to provide a method and a production system for preparing hexafluorobutadiene with low cost, high product purity, safety, continuous and stable production. Summary of the Invention

[0020] The object of the present invention is to provide a preparation method and production system of hexafluorobutadiene, so as to realize safe, stable and reliable production of hexafluorobutadiene.

[0021] The technical route of the present invention is as follows:

[0022] To achieve this object of the invention, according to a first aspect of the present invention, the present invention adopts the following technical solutions:

[0023] A method for preparing hexafluorobutadiene, comprising the following steps:

[0024] Step (1), introducing an organic solution of trifluoroethylene bromide and zinc powder into a first reactor containing an initiator, zinc powder and an organic solvent to react and obtain a trifluoroethylene zinc bromide solution; introducing the trifluoroethylene zinc bromide solution and zinc powder into a second reactor containing zinc powder, an initiator and a first organic solvent to completely convert unreacted trifluoroethylene bromide; the reaction solution enters a sedimentation device to separate excess zinc powder, thereby obtaining a trifluoroethylene zinc bromide solution from which the zinc powder has been removed; the first organic solvent is selected from a polar aprotic organic solvent;

[0025] Step (2), the trifluorovinyl zinc bromide solution from which the zinc powder has been removed obtained in step (1) and a pre-configured composite catalyst organic solution are introduced into a third reactor for a coupling reaction to obtain a synthetic solution including crude hexafluorobutadiene; the composite catalyst organic solution comprises an oxidant, a catalyst promoter, and a second organic solvent; the catalyst promoter is selected from a monovalent copper salt and a ferrous salt, and the second organic solvent is selected from a polar aprotic organic solvent;

[0026] Step (3) The synthetic liquid obtained in step (2) enters a purification system to obtain a purified hexafluorobutadiene product.

[0027] The preparation steps of the trifluoroethylene bromide solution are as follows:

[0028] A. Accurately add the same type of solvent as that in the first reactor into the bromotrifluoroethylene solution preparation kettle (water content ≤ 500ppm);

[0029] B. Then, a certain amount of trifluoroethylene bromide is introduced, and the temperature in the kettle is controlled between -10 and 10°C, and the mass concentration of the solution is between 5 and 30%. Preferably, the temperature in the kettle is controlled between 0 and 5°C, and the mass concentration of the solution is between 15 and 20%.

[0030] The specific steps for preparing the trifluorovinyl zinc bromide solution are as follows:

[0031] A. First, add an organic solvent, an initiator, and zinc powder into the first reactor, and heat it to a certain temperature under stirring. At the same time, add a solvent, an initiator, and zinc powder into the second reactor, and heat it to a certain temperature under stirring. Open the overflow valve of the first reactor to allow the material in the first reactor to overflow into the second reactor;

[0032] B. Continuously add trifluoroethylene bromide organic solution and zinc powder into the first reactor, continuously add zinc powder into the second reactor, open the overflow valve of the second reactor, allow the material in the second reactor to overflow or be pumped to a settling device, and obtain a trifluoroethylene zinc bromide solution after removing the zinc powder. The settling device includes a multi-stage settling tank, preferably a two-stage settling tank, the trifluoroethylene zinc bromide solution prepared in step (1) enters the first settling tank by overflow or pumping, open the overflow valve or pump of the first settling tank, allow the material in the first settling tank to overflow or be pumped to the second settling tank, and obtain a trifluoroethylene zinc bromide solution without zinc powder residue. The settling tank can be a sedimentation filter press tank, and excess zinc powder is settled to the settling tank baffle to obtain a trifluoroethylene zinc bromide solution without zinc powder residue. The zinc powder in the settling tank can be directly used for the preparation reaction of the trifluoroethylene zinc bromide solution after filter pressing.

[0033] The initiator is selected from any one or more of methyl bromide, 1,2-dibromoethane, elemental iodine, trimethylsilyl chloride and trifluoroethylene zinc bromide solution, and the molar ratio of the feed rate (mol / h) of trifluoroethylene bromide to the amount (mol) of the primer initiator is 1: (1-100).

[0034] Preferably, the initiator is selected from one of 1,2-dibromoethane, elemental iodine, and trifluorovinyl zinc bromide reagent solution, and the molar ratio of trifluoroethylene bromide feed rate (mol / h) to the amount of primer initiator used (mol) is 1:(1-50). Further preferably, the initiator is trifluorovinyl zinc bromide reagent solution.

[0035] In the process of preparing the trifluoroethylene zinc bromide solution, the numerical ratio of the feeding rate of the trifluoroethylene bromohydrate organic solution in kg / h to the mass value of the first reactor primer in kg is 1:(10-100); and the numerical ratio of the feeding rate of the trifluoroethylene bromohydrate organic solution in kg / h to the mass value of the second reactor primer in kg is 1:(5-100).

[0036] Preferably, the numerical ratio of the feed rate value of trifluorobromoethylene organic solution in kg / h to the mass value of the first reactor primer in kg is 1:(10-50); the numerical ratio of the feed rate value of trifluorobromoethylene organic solution in kg / h to the mass value of the second reactor primer in kg is 1:(10-50).

[0037] In the process of preparing trifluoroethylene zinc bromide solution, the molar ratio of trifluoroethylene bromide to the zinc powder feeding rate in the first reactor is 1:(1.0-5.0), and the molar ratio of trifluoroethylene bromide to the zinc powder feeding rate in the second reactor is 1:(0.1-2.0).

[0038] Preferably, during the reaction, the molar ratio of bromotrifluoroethylene to the zinc powder feed rate in the first reactor is 1:(1.0-3.0), and the molar ratio of bromotrifluoroethylene to the zinc powder feed rate in the second reactor is 1:(0.1-1.0).

[0039] In the process of preparing trifluorovinyl zinc bromide solution in step (1), the mesh size of zinc powder is 100 to 500 mesh.

[0040] Preferably, the mesh size of the zinc powder is 200 to 400 meshes.

[0041] In the process of preparing the trifluorovinyl zinc bromide solution in step (1), the organic solvent is selected from a polar aprotic organic solvent; the polar aprotic organic solvent is selected from one or a combination of two or more of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide and N-methylpyrrolidone, and the water content of the polar aprotic organic solvent is ≤500ppm.

[0042] Preferably, the polar aprotic organic solvent in step (1) is selected from one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide, and the water content of the polar aprotic organic solvent is ≤200 ppm.

[0043] During the preparation of trifluorovinyl zinc bromide solution in step (1), the temperature range of the first reactor is 60-120°C, and the temperature range of the second reactor is 60-90°C.

[0044] Preferably, the temperature range of the first reactor is 60-90°C, and the temperature range of the second reactor is 60-70°C.

[0045] In the process of preparing hexafluorobutadiene in step (2), the oxidant is selected from any one or more of sodium peroxide, potassium peroxide, sodium perborate, sodium persulfate, potassium persulfate, ammonium persulfate and di-tert-butyl peroxide; the catalytic auxiliary is selected from any one or more of cuprous chloride, cuprous bromide, cuprous iodide, ferrous chloride and ferrous bromide; and the polar aprotic organic solvent is selected from any one or more of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide and N-methylpyrrolidone.

[0046] Preferably, in the process of preparing hexafluorobutadiene in step (2), the oxidant is selected from ammonium perborate, sodium persulfate, and potassium persulfate; the auxiliary agent is selected from any one or more of cuprous iodide and ferrous chloride; and the polar aprotic organic solvent is selected from any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0047] In the process of preparing hexafluorobutadiene in step (2), the molar ratio of trifluorovinyl zinc bromide to oxidant is 1:(1.0-3.0). The molar ratio of trifluorovinyl zinc bromide to catalyst promoter in the trifluorovinyl zinc bromide solution is 1:(0.01-0.2).

[0048] Preferably, the molar ratio of trifluorovinyl zinc bromide to the oxidant is 1:(1.0-1.5). The molar ratio of trifluorovinyl zinc bromide to the catalyst promoter in the trifluorovinyl zinc bromide solution is 1:(0.01-0.05).

[0049] In the process of preparing hexafluorobutadiene in step (2), the temperature of the coupling reaction 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 s.

[0050] Preferably, the coupling reaction temperature is 0-10° C., the reaction pressure is 0-0.2 MPa, and the residence time in the reactor is 50-300 s.

[0051] 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 enters the distillation apparatus, the product is quickly distilled out, and then subjected to rectification to obtain a high-purity hexafluorobutadiene product.

[0052] The content of the difficult-to-separate impurity trifluorobromoethylene in the crude hexafluorobutadiene obtained by distillation is ≤0.1%, and the content of heptafluorobutene is ≤0.01%. The purity of the product after distillation is ≥99.9%.

[0053] According to a second aspect of the present invention, the present invention adopts the following technical solutions:

[0054] A production system for hexafluorobutadiene, which is used in the above-mentioned production method, comprises a trifluorovinyl zinc bromide solution preparation unit, a hexafluorobutadiene preparation unit, a zinc powder filtration unit, a distillation unit, and a rectification unit;

[0055] The trifluoroethylene zinc bromide solution preparation unit comprises a trifluoroethylene bromide organic solution feeding device, a zinc powder feeding device, a solvent and initiator feeding device, a first reactor, and a second reactor; wherein the trifluoroethylene bromide organic solution feeding device, the zinc powder feeding device, and the solvent and initiator feeding device are connected to the first reactor to feed the solution therein; the zinc powder feeding device, the solvent and initiator feeding device are connected to the second reactor to feed the solution therein; the first reactor and the second reactor are connected to output the trifluoroethylene zinc bromide solution obtained by the reaction in the first reactor to the second reactor; the upper parts of the first reactor and the second reactor are respectively connected to a vacuum and high-purity nitrogen device through a condenser; and the discharge of the second reactor is connected to a zinc powder sedimentation device;

[0056] The hexafluorobutadiene preparation unit includes a trifluorovinyl zinc bromide solution feeding device, a composite catalyst solution feeding device, and a third reactor, wherein the trifluorovinyl zinc bromide solution feeding device and the composite catalyst solution feeding device are connected to the inlet end of the third reactor;

[0057] The distillation unit includes a hexafluorobutadiene synthesis liquid feeding device, a distillation device and a product collecting device;

[0058] The distillation unit comprises a hexafluorobutadiene crude product feeding device, a distillation tower, a front fraction storage tank, a product collecting tank and a distillation residue storage tank.

[0059] The material of each device in the trifluorovinyl zinc bromide solution preparation unit is selected from one of glass-lined, carbon steel, 316L, and fluororesin-lined carbon steel; the material of the equipment in the zinc powder filtration unit is selected from one of carbon steel, 304, and 316L; the material of the equipment in the distillation unit is selected from one of glass-lined, 304, and 316L.

[0060] Furthermore, the first reactor and the second reactor are equipped with a stirring device, and the type of the stirring paddle is selected from a propeller stirring paddle; the distillation device is equipped with a stirring device, and the type of the stirring paddle is selected from an anchor stirring paddle.

[0061] Beneficial effects of the present invention:

[0062] (1) In the preparation step of trifluoroethylene zinc bromide, a two-stage series reactor is used, which not only achieves almost complete conversion of the raw material trifluoroethylene bromide and improves the utilization rate of the raw material, but also reduces the pressure on the distillation and purification of the subsequent products, which is conducive to improving the purity of the product.

[0063] (2) In the oxidative coupling step for preparing hexafluorobutadiene, inexpensive peroxides are used as oxidants, and catalytic amounts of copper or iron salts are used as additives. Compared with the traditional process using equivalent amounts of copper or iron salts, this not only significantly reduces raw material costs, but also reduces the emission of heavy metal waste solids, alleviating environmental pressure. Furthermore, the use of inorganic peroxides as oxidants, compared with metal chlorides as oxidants, can reduce the production of difficult-to-separate impurities such as fluoroolefins, thereby improving product purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] FIG1 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.

[0065] FIG2 is a schematic diagram of a hexafluorobutadiene preparation unit and a distillation unit in an embodiment of the present invention.

[0066] FIG3 is a chromatographic analysis spectrum of the hexafluorobutadiene product prepared in Example 15 of the present invention.

[0067] The above drawings include the following reference numerals:

[0068] 1. Trifluoroethylene bromide solution storage tank; 2. Initiator or solvent storage tank; 3. First reactor; 4. Second reactor; 5. First zinc powder storage tank; 6. Second zinc powder storage tank; 7. First condenser; 8. Second condenser; 9. First sedimentation tank; 10. Second sedimentation tank; 11. First trifluoroethylene zinc bromide solution storage tank; 12. Second trifluoroethylene zinc bromide solution storage tank; 13. Composite catalyst solution storage tank; 14. Third reactor; 15. Hexafluorobutadiene synthesis 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. Fifth condenser; 23. Sixth condenser; 24. Second hexafluorobutadiene buffer tank; 25. Second hexafluorobutadiene crude product tank; 26. Residue storage tank. DETAILED DESCRIPTION

[0069] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0070] First, the production system for preparing hexafluorobutadiene according to the present invention will be described with reference to the accompanying drawings.

[0071] The hexafluorobutadiene production system comprises a trifluorovinyl zinc bromide solution preparation unit, a hexafluorobutadiene preparation unit, a zinc powder filtration unit, a distillation unit and a rectification unit;

[0072] The trifluoroethylene zinc bromide solution preparation unit includes a trifluoroethylene bromide organic solution feeding device, a zinc powder feeding device, a solvent and initiator feeding device, a first reactor 3, and a second reactor 4.

[0073] The trifluoroethylene bromide organic solution feeding device includes a trifluoroethylene bromide solution storage tank 1, and the solvent and initiator feeding device includes an initiator or solvent storage tank 2. These feed materials into the corresponding feed points above the first reactor 3 by pumping or gravity, respectively. The zinc powder feeding device includes a first zinc powder storage tank 5, which utilizes gravity feeding. The first reactor 3 is connected to a second reactor 4, which delivers the trifluoroethylene zinc bromide solution produced in the first reactor 3 to the second reactor 4. The second reactor 4 is also connected to the zinc powder feeding device, which can utilize a second zinc powder storage tank 6 and utilizes gravity feeding. 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 discharge port of the second reactor 4 is connected to the zinc powder filtration unit. The zinc powder filtration unit can utilize a two-stage sedimentation tank, namely a first sedimentation tank 9 and a second sedimentation tank 10. The discharge of the second sedimentation tank 10 is connected to the first trifluoroethylene zinc bromide solution storage tank 11, which can serve as a material buffer for production.

[0074] The hexafluorobutadiene production unit includes a trifluorovinyl zinc bromide solution feeding device, a composite catalyst solution feeding device, and a third reactor 14. The third reactor 14 is a tubular reactor. The trifluorovinyl zinc bromide solution feeding device and the composite catalyst solution feeding device are connected to the inlet end of the third reactor. The trifluorovinyl zinc bromide solution feeding device includes a second trifluorovinyl zinc bromide solution storage tank 12, which can be the same as the first trifluorovinyl zinc bromide solution storage tank 11. The fluorovinyl zinc bromide solution feeding device feeds the third reactor 14 by pumping. The composite catalyst solution feeding device includes a composite catalyst solution storage tank 13, which feeds the third reactor 14 by pumping.

[0075] The distillation unit includes a hexafluorobutadiene synthesis liquid feeding device, a distillation device and a product collecting device. The outlet end of the third reactor 14 can be connected to a hexafluorobutadiene synthesis liquid buffer tank 15.

[0076] The distillation unit comprises a hexafluorobutadiene synthesis liquid feeding device, a distillation device and a product collecting device.

[0077] The hexafluorobutadiene synthesis liquid feeding device includes a hexafluorobutadiene synthesis liquid buffer tank 15, which is pumped to two parallel purification systems. The first purification system includes a first distillation unit 16, which is connected to a first hexafluorobutadiene buffer tank 20 via a third condenser 18. 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 unit 17, which is connected to a second hexafluorobutadiene buffer tank 24 via a fifth condenser 22. 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 unit. Reference numeral 26 represents a distillation residue storage tank.

[0078] The following examples utilize the production system described above.

[0079] Example 1

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

[0081] (2) In a 500 L second reactor made of 316 L material, 300 kg of a 25% by mass solution of trifluorovinyl zinc bromide in N,N-dimethylformamide was added, stirring was started, 32.5 kg of zinc powder was added, and the reactor was heated to 60°C;

[0082] (3) Add trifluoroethylene bromide in N,N-dimethylformamide (mass fraction 20%) to the first reactor at a controlled flow rate of 15 kg / h; simultaneously, add zinc powder (325 mesh, 1.3 kg / h) to the first reactor through a solid feeding device;

[0083] (4) Open the overflow valve connecting the first reactor and the second reactor. When the liquid level in the first reactor exceeds the overflow height, the material enters the second reactor; at the same time, zinc powder (325 mesh, 0.35 kg / h) is added to the second reactor through the solid feeding equipment;

[0084] (5) Open the overflow valves of the second reactor and the first sedimentation tank. When the liquid level in the second reactor exceeds the overflow height, the material enters the first sedimentation tank and the excess zinc powder is settled to the baffle;

[0085] (6) Open the valve connecting the first sedimentation tank and the second sedimentation tank. When the material level in the first sedimentation tank exceeds the valve outlet height, turn on the material delivery pump to deliver the material to the second sedimentation tank and settle the residual zinc powder to the baffle;

[0086] (7) Open the valve connecting the second settling tank and the trifluoroethylene zinc bromide solution storage tank. When the material level in the second settling tank exceeds the valve outlet height, turn on the material delivery pump to deliver the material to the storage tank. After 72 hours of operation, the trifluoroethylene zinc bromide solution storage tank was sampled and analyzed. The results showed: the normalized content of trifluoroethylene bromide was 0.005%, the mass fraction of trifluoroethylene zinc bromide was 25.1% (NMR fluorine spectrum internal standard method), the theoretical mass fraction was 26%, and the average yield was 96.5%.

[0087] Example 2

[0088] The operation of this example is the same as that of Example 1, except that the flow rate of 15 kg / h of a 20% N,N-dimethylformamide solution of trifluoroethylene bromide was replaced by a 20% N,N-dimethylformamide solution 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 by the addition of zinc powder (325 mesh, 1.8 kg / h); the addition of zinc powder (325 mesh, 0.35 kg / h) to the second reactor was replaced by the addition of zinc powder (325 mesh, 0.48 kg / h) to the second reactor. Other conditions remained unchanged. After 72 hours of operation, the trifluoroethylene zinc bromide solution storage tank was sampled and analyzed. The results showed: the normalized content of trifluoroethylene bromide was 0.008%, the mass fraction of trifluoroethylene zinc bromide was 24.4% (NMR fluorine spectrum internal standard method), the theoretical mass fraction was 26%, and the average yield was 93.8%.

[0089] Example 3

[0090] The operation of this embodiment is the same as that of Example 1, except that the addition of zinc powder (325 mesh, 0.35 kg / h) into the second reactor is replaced by the addition of zinc powder (325 mesh, 0.20 kg / h) into the second reactor.

[0091] After 72 hours of operation, samples of the trifluoroethylene zinc bromide solution were taken from the storage tank for analysis. The results showed: a normalized trifluoroethylene bromide content of 0.006%, a mass fraction of trifluoroethylene zinc bromide of 24.7% (NMR fluorine spectrum internal standard method), a theoretical mass fraction of 26%, and an average yield of 95.0%.

[0092] Example 4

[0093] The operation of this example was the same as that of Example 1, except that the mesh size of the zinc powder was changed from 325 mesh to 500 mesh, while all other conditions remained unchanged. After 72 hours of operation, the trifluoroethylene zinc bromide solution was sampled and analyzed from the storage tank. The results showed that the normalized content of trifluoroethylene bromide was 0.01%, the mass fraction of trifluoroethylene zinc bromide was 22.2% (NMR fluorine spectrum internal standard method), the theoretical mass fraction was 26%, and the average yield was 85.3%.

[0094] Example 5

[0095] The operation of this embodiment is the same as that of Example 1, except that the temperature of the first reactor is replaced by 60° C. from 80° C., and other conditions remain unchanged. The reaction is carried out for 72 h, and sampling and analysis of the trifluoroethylene zinc bromide solution storage tank are performed. The results show that the normalized content of trifluoroethylene bromide is 0.012%, the mass fraction of trifluoroethylene zinc bromide is 21.7% (NMR fluorine spectrum internal standard method), the theoretical mass fraction is 26%, and the average yield is 83.3%.

[0096] Example 6

[0097] The operation of this example is the same as that of Example 1, except that the temperature of the second reactor is replaced by 70° C. from 60° C., and other conditions remain unchanged. The reaction is carried out for 72 h, and sampling and analysis of the trifluoroethylene zinc bromide solution storage tank are performed. The results show that the normalized content of trifluoroethylene bromide is 0.005%, the mass fraction of trifluoroethylene zinc bromide is 24.9% (NMR fluorine spectrum internal standard method), the theoretical mass fraction is 26%, and the average yield is 95.8%.

[0098] Example 7

[0099] The operation of this example was the same as that of Example 1, except that the N,N-dimethylformamide solution of 25% by mass of trifluorovinylzinc bromide added to the first and second reactors was replaced by a N,N-dimethylacetamide solution of 25% by mass of trifluorovinylzinc bromide added to the first and second reactors. The N,N-dimethylformamide solution (mass fraction) of trifluoroethylene bromide added to the first reactor was replaced by a N,N-dimethylacetamide solution (mass fraction) of trifluoroethylene bromide added to the first reactor. Other conditions remained unchanged. The reaction was run for 72 hours, and the trifluorovinylzinc bromide solution storage tank was sampled and analyzed. The results showed: the normalized content of trifluoroethylene bromide was 0.007%, the mass fraction of trifluorovinylzinc bromide was 23.9% (NMR fluorine spectrum internal standard method), the theoretical mass fraction was 26%, and the average yield was 91.9%.

[0100] Example 8

[0101] The operation of this embodiment is the same as that of Example 1, except that the zinc powder is replaced by the zinc powder recovered from the first settling tank. Other conditions remain unchanged. The reaction is carried out for 72 hours, and the trifluoroethylene zinc bromide solution storage tank is sampled and analyzed. The results show that the normalized content of trifluoroethylene bromide is 0.006%, the mass fraction of trifluoroethylene zinc bromide is 24.3% (NMR fluorine spectrum internal standard method), the theoretical mass fraction is 26%, and the average yield is 93.5%.

[0102] Comparative Example 1

[0103] The trifluorovinyl zinc bromide solution is prepared by a single reactor reaction, and the operation steps are as follows:

[0104] (1) In a 500 L first reactor made of 316 L material, 300 kg of a 25% by mass solution of trifluorovinyl zinc bromide in N,N-dimethylformamide was added, stirring was started, 65 kg of zinc powder was added, and the reactor was heated to 80°C;

[0105] (2) Add trifluoroethylene bromide in N,N-dimethylformamide (mass fraction 20%) to the first reactor at a controlled flow rate of 15 kg / h; simultaneously, add zinc powder (325 mesh, 1.3 kg / h) to the first reactor through a solid feeding device;

[0106] (3) Open the overflow valves of the first reactor and the first sedimentation tank. When the liquid level in the second reactor exceeds the overflow height, the material enters the first sedimentation tank and the excess zinc powder is settled to the baffle;

[0107] (4) Open the valve connecting the first sedimentation tank and the second sedimentation tank. When the material level in the first sedimentation tank exceeds the valve outlet height, turn on the material delivery pump to deliver the material to the second sedimentation tank and settle the residual zinc powder to the baffle.

[0108] (5) Open the valve connecting the second settling tank to the trifluoroethylene zinc bromide solution storage tank. When the material level in the second settling tank exceeds the valve outlet height, turn on the material delivery pump to deliver the material to the storage tank. After 72 hours of operation, samples were taken from the trifluoroethylene zinc bromide solution storage tank for analysis. The results showed: the normalized content of trifluoroethylene bromide was 1.56%, the mass fraction of trifluoroethylene zinc bromide was 20.2% (NMR fluorine spectrum internal standard method), the theoretical mass fraction was 26%, and the average yield was 77.8%.

[0109] Example 9

[0110] (1) Add 300 kg of N,N-dimethylformamide to a 500 L glass-lined reactor, add ammonium persulfate (40 kg, 175 mol) and cuprous iodide (0.67 kg, 3.5 mol) under stirring, maintain the internal temperature at 0-5°C, and complete the preparation of the oxidant solution. The oxidant concentration is 0.51 mol / kg and the auxiliary agent concentration is 0.01 mol / kg.

[0111] (2) To a 316L spiral reaction tube (total length 10 meters, tube inner diameter 8 mm), the above-described oxidant solution (flow rate 40 kg / h, equivalent to an ammonium persulfate flow rate of 20.4 mol / h, and a cuprous iodide flow rate of 0.4 mol / h) and trifluorovinyl zinc bromide solution (mass fraction 25%, flow rate 16.8 kg / h, equivalent to trifluorovinyl zinc bromide 18.6 mol / h) were added. The internal temperature was controlled at 0-5°C, and the pressure in the reaction tube was controlled at 0.05 MPa.

[0112] (3) The synthetic liquid was introduced into distillation apparatus A or B from the outlet of the reaction tube. The temperature in the reactor was 60°C and the vacuum degree in the reactor was 0.1 MPa. The crude hexafluorobutadiene product was collected by condensation from the vacuum pump. The condenser temperature was -15°C. After 72 hours of operation, the results were: 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 are shown in Table 1 below). The total yield was 102.6 kg, the theoretical yield was 108.5 kg, and the average yield was 94.6%.

[0113] Example 10

[0114] The operation of this example was the same as that of Example 9, except that the above-described oxidant solution (flow rate of 60 kg / h, equivalent to 30.6 mol / h of ammonium persulfate and 0.6 mol / h of cuprous iodide) and trifluorovinyl zinc bromide solution (mass fraction 25%, flow rate of 25.2 kg / h, equivalent to 27.9 mol / h of trifluorovinyl zinc bromide) were added. Other conditions remained unchanged and the reaction was run for 72 hours. The results were as follows: 156.1 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main impurity content of 95.81% (the contents of other impurities are shown in Table 1 below). The total yield was 149.5 kg, the theoretical yield was 162.8 kg, and the average yield was 91.8%.

[0115] Example 11

[0116] The operation of this embodiment is the same as that of Example 9, except that in step (1), ammonium persulfate (40 kg, 0.175 kmol) is replaced by potassium persulfate (40 kg, 0.148 kmol), the oxidant concentration is 0.43 mol / kg, and the auxiliary agent concentration is 0.01 mol / kg.

[0117] In step (2), the oxidant solution (flow rate of 40 kg / h, equivalent to 20.4 mol / h of ammonium persulfate and 0.4 mol / h of cuprous iodide) was replaced with an oxidant solution (flow rate of 47.4 kg / h, equivalent to 20.4 mol / h of potassium persulfate and 0.4 mol / h of cuprous iodide), with other conditions remaining unchanged. After 72 h of operation, the result was: 104.3 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main content of 93.80% (the contents of other impurities are shown in Table 1 below). The total weight was 97.8 kg, the theoretical yield was 108.5 kg, and the average yield was 90.1%.

[0118] Example 12

[0119] The operation of this embodiment is the same as that of Example 9, except that cuprous iodide (0.67 kg, 3.5 mol) is replaced with ferrous chloride (0.70 kg, 3.5 mol) in step (1). Other conditions remain unchanged. After 72 hours of operation, the result is: 109.4 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main content of 94.68% (the contents of other impurities are shown in Table 1 below). The total weight was 103.6 kg, the theoretical yield was 108.5 kg, and the average yield was 95.5%.

[0120] Example 13

[0121] The operation of this embodiment is the same as that of Example 9, except that: in step (1), cuprous iodide (0.67kg, 3.5mol) is replaced by cuprous iodide (1.33kg, 7.0mol), the oxidant solution configuration is completed, and the auxiliary agent concentration is replaced by 0.02mol / kg by 0.01mol / kg. The flow rate of cuprous iodide in step (2) is replaced by 0.8mol / h by 0.4mol / h. Other conditions remain unchanged. After running for 72h, the result is: 107.4kg of hexafluorobutadiene crude product is collected from the crude product tank after the pump, with a main content of 95.02% (the contents of other impurities are shown in Table 1 below). The total weight is 102.0kg, the theoretical output is 108.5kg, and the average yield is 94.0%.

[0122] Example 14

[0123] The operation of this example is the same as that of Example 9, except that the internal temperature is maintained at 5-10°C instead of 0-5°C, and the internal temperature in step (2) is controlled at 5-10°C instead of 0-5°C. Other conditions remain unchanged. After 72 hours of operation, the results are as follows: 107.1 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main content of 94.25% (the contents of other impurities are shown in Table 1 below). The total weight was 100.9 kg, the theoretical yield was 108.5 kg, and the average yield was 93.0%.

[0124] Comparative Example 2

[0125] The operation of this example was the same as that of Example 9, except that the auxiliary agent, cuprous iodide, was not added during the preparation of the oxidant solution in step (1). All other conditions remained unchanged. The operation was continued for 72 hours, and the results were as follows: 10.7 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main component content of 66.51% (the contents of other impurities are shown in Table 1 below). The total weight was 7.1 kg, with a theoretical yield of 108.5 kg and an average yield of 6.5%.

[0126] Comparative Example 3

[0127] The operation of this example was the same as that of Example 9, except that in step (3), the hexafluorobutadiene synthesis liquid was subjected to batch distillation in a kettle, and the synthesis liquid after 72 hours of operation was fed into the distillation apparatus at once. All other conditions remained unchanged. The results were: 98.3 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main content of 93.85% (the contents of other impurities are shown in Table 1 below). The total weight was 92.3 kg, the theoretical yield was 108.5 kg, and the average yield was 85.1%.

[0128] Comparative Example 4

[0129] The operation of this embodiment is the same as that of embodiment 9, except that in step (1), an equimolar amount of an iron salt oxidant is used instead of a persulfate oxidant during the preparation of the oxidant solution, as follows:

[0130] (1) Add 300 kg of N,N-dimethylformamide to a 500 L glass-lined reactor, add ferric chloride (28.4 kg, 0.175 kmol) under stirring, maintain the internal temperature at 0-5 °C, and complete the preparation of the oxidant solution. The oxidant concentration is 0.53 mol / kg.

[0131] (2) To a 316L spiral reaction tube (total length 10 meters, tube inner diameter 8 mm), the above-described oxidant solution (flow rate of 38.5 kg / h, equivalent to a flow rate of 20.4 mol / h of ferric chloride) and trifluorovinyl zinc bromide solution (mass fraction 25%, flow rate of 16.8 kg / h, equivalent to 18.6 mol / h of trifluorovinyl zinc bromide) were added. The internal temperature was controlled at 0-5°C and the pressure in the reaction tube was controlled at 0.05 MPa.

[0132] Step (3) was the same as in Example 9 and was run for 72 hours. The results were as follows: 102.7 kg of crude hexafluorobutadiene was collected from the crude product tank after the pump, with a main content of 88.52% (the contents of other impurities are shown in Table 1 below). The total weight was 90.9 kg, with a theoretical yield of 108.5 kg and an average yield of 83.8%.

[0133] Table 1 Composition of crude hexafluorobutadiene prepared in Examples 9 to 14 and Comparative Examples 2 to 4

[0134] Example 15

[0135] The crude hexafluorobutadiene prepared in Example 9 was used as a raw material to conduct a distillation experiment. The distillation column parameters and distillation parameters are shown in Tables 2 and 3 below:

[0136] Table 2 Distillation column parameters

[0137] Table 3 Distillation process parameters

[0138] The distillation feed was 100 kg, yielding 22.6 kg of fore-fraction, 65.7 kg of product, and 10.5 kg of still residue. The product purity was 99.9908%, the single-batch distillation yield was 65.7%, and the material balance was 98.8%. The chromatogram of the product after distillation is shown in Figure 3, and the results are as follows:

Claims

1. A method for preparing hexafluorobutadiene, characterized in that: The preparation method comprises the following steps: Step (1), introducing an organic solution of trifluoroethylene bromide and zinc powder into a first reactor containing an initiator, zinc powder and an organic solvent to react and obtain a trifluoroethylene zinc bromide solution; the trifluoroethylene zinc bromide solution and zinc powder are introduced into a second reactor containing zinc powder, an initiator and a first organic solvent to completely convert unreacted trifluoroethylene bromide; the reaction solution enters a sedimentation device to separate excess zinc powder, thereby obtaining a trifluoroethylene zinc bromide solution from which zinc powder has been removed; the first organic solvent is selected from a polar aprotic organic solvent; Step (2), the trifluorovinyl zinc bromide solution from which the zinc powder has been removed obtained in step (1) and a pre-configured composite catalyst organic solution are introduced into a third reactor for coupling reaction to obtain a synthetic liquid including a crude hexafluorobutadiene product; the composite catalyst organic solution comprises an oxidant, a catalyst promoter and a second organic solvent; the catalyst promoter is selected from a monovalent copper salt and a ferrous salt, and the second organic solvent is selected from a polar aprotic organic solvent; Step (3) The synthetic liquid obtained in step (2) enters a purification system to obtain purified hexafluorobutadiene.

2. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: The initiator is selected from any one or more of methyl bromide, 1,2-dibromoethane, iodine, trimethylsilyl chloride and trifluorovinyl zinc bromide reagent solution; preferably, the initiator is selected from one of the 1,2-dibromoethane, iodine and trifluorovinyl zinc bromide reagent solution, and the molar ratio of the feed rate (mol / h) of trifluoroethylene bromide to the amount of the primer initiator (mol) is 1: (1 to 50).

3. The method for preparing hexafluorobutadiene according to claim 1 or 2, characterized in that: The initiator is selected from any one or more of the 1,2-dibromoethane, trimethylsilyl chloride and the trifluoroethylene zinc bromide reagent solution, and the numerical ratio of the feed rate value of the trifluoroethylene bromide in mol / h to the molar value of the bottoming initiator amount is 1:(1-100).

4. The method for preparing hexafluorobutadiene according to any one of claims 1 to 3, characterized in that: The mass concentration of the trifluoroethylene bromide organic solution is 5-30%; during the reaction, the numerical ratio of the feed rate of the trifluoroethylene bromide organic solution in kg / h to the mass value of the first reactor primer in kg is 1:(10-100), preferably 1:(10-50); the numerical ratio of the feed rate of the trifluoroethylene bromide organic solution in kg / h to the mass value of the second reactor primer in kg is 1:(5-100), preferably 1:(10-50); the molar ratio of the trifluoroethylene bromide to the zinc powder feed rate in the first reactor is 1:(1.0-5.0), preferably 1:(1.0-3.0), and the molar ratio of the trifluoroethylene bromide to the zinc powder feed rate in the second reactor is 1:(0.1-2.0), preferably 1:(0.1-1.0).

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

6. The method for preparing hexafluorobutadiene according to any one of claims 1 to 5, characterized in that: The temperature range of the first reactor is 60-120°C, preferably 60-90°C; the temperature range of the second reactor is 60-90°C, preferably 60-70°C.

7. The method for preparing hexafluorobutadiene according to any one of claims 1 to 6, characterized in that: The sedimentation device comprises a multi-stage sedimentation tank.

8. The method for preparing hexafluorobutadiene according to any one of claims 1 to 7, characterized in that: The sedimentation device comprises two stages, namely a first sedimentation tank and a second sedimentation tank. The trifluorovinyl zinc bromide solution prepared in the step (1) enters the first sedimentation tank and the second sedimentation tank in sequence by overflow or pumping, and the excess zinc powder is precipitated to obtain a trifluorovinyl zinc bromide solution without residual zinc powder.

9. The method for preparing hexafluorobutadiene according to claim 7 or 8, characterized in that: The zinc powder in the sedimentation tank in the step (1) can be directly used for the preparation reaction of trifluorovinyl zinc bromide solution after filter pressing.

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

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

12. The method for preparing hexafluorobutadiene according to any one of claims 1 to 11, characterized in that: The temperature of the coupling reaction in step (2) 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 s; preferably, the temperature of the coupling reaction in step (2) 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 s.

13. The method for preparing hexafluorobutadiene according to any one of claims 1 to 12, characterized in that: In the step (3), the synthetic liquid obtained in the step (2) is distilled to obtain crude hexafluorobutadiene, which is then rectified to obtain pure hexafluorobutadiene.

14. The method for preparing hexafluorobutadiene according to claim 13, characterized in that: The content of trifluoroethylene bromide in the crude hexafluorobutadiene obtained by distillation is ≤0.1%, the content of heptafluorobutene is ≤0.01%, and the purity of the product after distillation is ≥99.9%.

15. A system for preparing and producing hexafluorobutadiene, characterized in that: The preparation production system is used for the preparation method described in any one of claims 1 to 14, 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 trifluoroethylene zinc bromide solution preparation unit comprises a trifluoroethylene bromide organic solution feeding device, a zinc powder feeding device, a solvent and initiator feeding device, a first reactor, and a second reactor; wherein the trifluoroethylene bromide organic solution feeding device, the zinc powder feeding device, and the solvent and initiator feeding device are connected to the first reactor to feed thereto; the zinc powder feeding device and the solvent and initiator feeding device are connected to the second reactor to feed thereto; the first reactor and the second reactor are connected to output the trifluoroethylene zinc bromide solution obtained by the reaction in the first reactor to the second reactor; the upper parts of the first reactor and the second reactor are respectively connected to a vacuum and high-purity nitrogen device through a condenser; and the discharge of the second reactor is connected to a zinc powder sedimentation device; The hexafluorobutadiene preparation unit comprises a trifluorovinyl zinc bromide solution feeding device, a composite catalyst solution feeding device, and a third reactor, wherein the trifluorovinyl zinc bromide solution feeding device and the composite catalyst solution feeding device are connected to the inlet end of the third reactor; The distillation unit comprises a hexafluorobutadiene synthesis liquid feeding device, a distillation device and a product collecting device; The distillation unit comprises a hexafluorobutadiene crude product feeding device, a distillation tower, a fore fraction storage tank, a product collecting tank and a distillation residual liquid storage tank.

16. The system for preparing hexafluorobutadiene according to claim 15, characterized in that: The equipment materials in the trifluorovinyl zinc bromide solution preparation unit and the hexafluorobutadiene preparation unit are selected from one of glass-lined, carbon steel, 316L, and fluororesin-lined carbon steel; the equipment material of the zinc powder filtration unit is selected from one of carbon steel, 304, and 316L; the equipment material of the distillation unit is selected from one of glass-lined, 304, and 316L.

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