Preparation method and production system of hexafluorobutadiene

Abstract

The invention discloses a preparation method and a production system of hexafluorobutadiene, the preparation method comprises the following steps: (1) an organic solution of trifluorobromoethylene and zinc powder respectively enter a first reactor and a second reactor which are filled with an initiator, the zinc powder and an organic solvent in sequence, and a trifluorovinyl zinc bromide solution is obtained through reaction; then the reaction liquid enters a sedimentation device to separate excessive zinc powder, a trifluorovinyl zinc bromide solution without zinc powder is obtained, and the excessive zinc powder is filtered and then recycled. And (2) the obtained trifluorovinyl zinc bromide solution and a pre-prepared composite catalyst solution enter a third reactor for a coupling reaction, and a hexafluorobutadiene crude product is obtained. And (3) purifying the obtained hexafluorobutadiene crude product to obtain a product with the purity of more than or equal to 99.99%. The method has the advantages of high trifluorobromoethylene conversion rate, low cost of the coupling composite catalyst, mild reaction conditions, high product purity, high safety and the like.

Description

Technical Field

[0001] The present invention relates to the preparation of fluorine-containing electronic gases, and particularly to a preparation method and a production system for hexafluorobutadiene. Technical Background:

[0002] Hexafluorobutadiene (C 4 F 6 ) is a colorless liquefiable fluorine-containing gas with a boiling point of 5.5 °C under normal pressure and a liquid density of 1.44 g / mL at 15 °C. Currently, hexafluorobutadiene is mainly used as a dry etching gas for the precise etching of key dimensions (with an accuracy of up to 100 nm) in the production of rectifying circuit boards containing Cu and low-k dielectric constants, and has better selectivity and aspect ratio than other etching gases. For example, compared with octafluorocyclobutane (c-C 4 F 8 ), the etching aspect ratio of C 4 F 6 can reach 10, while that of c-C 4 F 8 is only 3. Therefore, C 4 F 6 is suitable for extremely narrow linewidth processes. C 4 F 6 only etches the silicon oxide film without affecting the photoresist, silicon film, and nitride film, and has excellent etching selectivity. In addition, hexafluorobutadiene also has good environmental performance, with an ODP = 0, GWP(100) = 290, and a residence time in the atmosphere of only 1.9 d, making it an etching gas with extremely low greenhouse effect and environmental friendliness. Therefore, with the development of the integrated circuit industry and the increasing attention to greenhouse gases, hexafluorobutadiene, which has the best etching effect and environmental friendly characteristics, is bound to become the leading product and be widely used in the laser etchant market.

[0003] The preparation process of hexafluorobutadiene has been one of the research hotspots in recent years, but there are not many that can truly achieve industrial production. The following are the main reports on the preparation of hexafluorobutadiene in the prior art:

[0004] (1) Oxidative coupling process

[0005] The self-coupling route takes the preparation of the key intermediate trifluorovinyl zinc halide (CF 2 =CFZnX) as the core, and then undergoes a self-coupling reaction in the presence of Fe 3+ or Cu 2+ ions to obtain hexafluorobutadiene. For example, WO 2006 / 026400 discloses using trichlorofluoroethylene (CF 2 =CFCl) as a raw material, through hydrodechlorination, bromination, and dehydrobromination to prepare trifluorobromoethylene (CF 2 =CFBr), and then reacting with zinc powder to prepare trifluorovinyl zinc bromide (CF2 = CFZnBr), and finally in the presence of Fe 3+ or Cu 2+ ion, the self-coupling reaction occurs to obtain hexafluorobutadiene. Although the materials used in this method are relatively inexpensive, it involves multiple dangerous production processes, has a long process, and the intermediate trifluoroethylene has a risk of self-polymerization, which is not suitable for industrial scale-up production.

[0006] CN 104829415 discloses a process route 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 zinc trifluorovinyl bromide, and finally, it undergoes self-coupling in the presence of an Fe3+ oxidant to obtain hexafluorobutadiene, with a total reaction 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 activity, and the yield is low when preparing zinc trifluorovinyl bromide with zinc powder, resulting in a relatively high actual unit consumption and a large amount of three wastes in this process route, and the actual industrialization prospect is low.

[0007] [Journal of Fluorine Chemistry 129(2008)443–446] reported that using tetrafluoroethane (HFC-134a) as a raw material, the lithium diisopropylamine mechanism (LDA) was used as a hydrogen abstraction reagent to prepare zinc trifluorovinyl chloride in a zinc chloride / tetrahydrofuran system, and then in the presence of Cu 2+ or Fe 3+ to obtain hexafluorobutadiene, with a reaction yield of 69–70%. The raw material R134a of this process is inexpensive and easily available, the synthesis steps are simple, and it can be synthesized in a "one-pot". However, the first step of the reaction uses the strong base lithium diisopropylamide (LDA), which is expensive and has high danger in the production process, and the industrial feasibility is low.

[0008] JP 2001114710 reported a process route for synthesizing hexafluorobutadiene using tetrafluoroethylene as a raw material. First, tetrafluoroethylene reacts with bromine to obtain 1,2-dibromotetrafluoroethane; secondly, 1,2-dibromotetrafluoroethane rearranges to obtain 1,1-dibromotetrafluoroethane under the catalysis of a Lewis acid; thirdly, 1,1-dibromotetrafluoroethane reacts with zinc powder to obtain zinc trifluorovinyl bromide reagent, and finally, the zinc trifluorovinyl bromide reagent undergoes self-coupling in the presence of Cu 2+ or Fe 3+ catalyst to obtain the target product hexafluorobutadiene., The reaction conditions of this process are relatively mild, and the raw material cost is relatively low. However, the total yield of this process is relatively low (<50%), and using tetrafluoroethylene as a raw material, the industrialization is limited.

[0009] (2) Debromination process

[0010] The dehalogenation process involves obtaining the intermediate tetrachlorohexafluorobutane (XCF 2 -CFX-CFX-CF 2 X) through telomerization or intermolecular dehalogenation, and then reacting it with zinc powder in an alcohol solvent to prepare hexafluorobutadiene. US304630 discloses a method for preparing perfluorobutadiene using trichlorotrifluoroethylene as the raw material. Trichlorotrifluoroethylene first reacts with iodine chloride (ICl) in a sealed 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 ultraviolet light irradiation to obtain 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane. Finally, 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane undergoes dechlorination in an alcohol solvent under the action of zinc powder to obtain hexafluorobutadiene. This method requires the use of chemically equivalent iodine chloride and mercury to participate in the reaction, and one of the products is mercuric iodide, which is highly toxic and the reagents used are expensive.

[0011] CN106336342 improved this process by using a zinc powder / acetic anhydride system for intermolecular coupling, avoiding the use of highly toxic mercury as the raw material, and the process conditions are relatively mild, with high yields (90%) in all three reaction steps. However, it still requires expensive iodine as the raw material and is not suitable for large-scale production.

[0012] US2894043 discloses that 1,2-dichlorodifluoroethylene (CFCl=CFCl) dimerizes into the intermediate 1,2,3,4-tetrachlorohexafluorobutane in the presence of fluorine gas, and then zinc powder is used for dechlorination to obtain the target product perfluorobutadiene. This method requires low-temperature conditions (-70 °C) in the fluorination dimerization stage and requires the use of highly dangerous gas F 2 2. US2676193 improved this method, but the reaction still requires high-temperature (300 °C) and high-pressure (12 MPa) conditions, and the reaction yield is low, only 30 - 40%, and there are many by-products, making product separation difficult.

[0013] RU0118462 reported a route for synthesizing hexafluorobutadiene using trichlorotrifluoroethylene as the raw material. This patent avoids the use of highly toxic mercury and expensive iodine reagents. First, trichlorotrifluoroethylene dimerizes at high temperature to obtain 34% of 1,2-dichlorohexafluorocyclobutane and 27% of 3,4-dichlorohexafluoro-1-butene. Then these two products are separated by a high-efficiency rectification column. 3,4-dichlorohexafluoro-1-butene directly undergoes dechlorination with zinc powder to obtain the target product hexafluorobutadiene. The advantage of this method is that it only requires two reaction steps to obtain C 4 F 6 4, with a shorter process. However, the separation of the dimerization products requires the use of a fractionation process with high requirements, increasing the production cost to a certain extent, and the yield of the target intermediate after improvement is still less than 30%.

[0014] (3) Catalytic coupling process

[0015] WO 2018235883 discloses a catalytic self-coupling reaction with chlorotrifluoroethylene as the 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 with chlorotrifluoroethylene and trifluoroethylene as the 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 has a simple process, it uses expensive palladium as the catalyst and has no advantage in terms of raw material cost.

[0016] (4) Fluorine gas process

[0017] WO2007125972 discloses a process for preparing hexafluorobutadiene using butadiene as the raw material. The main steps are as follows: First, 1,3-butadiene reacts with chlorine gas to generate 1,2,3,4-tetrachlorobutane; Second, without a catalyst and using an inert gas as the carrier gas, 1,2,3,4-tetrachlorobutane reacts with fluorine gas in the gas phase to generate 1,2,3,4-tetrachlorohexafluorobutane; Finally, 1,2,3,4-tetrachlorohexafluorobutane reacts with zinc powder in a solvent to obtain hexafluorobutadiene.

[0018] In view of the deficiencies of the prior art, there is a need to provide a preparation method and a preparation production system for hexafluorobutadiene with low cost, high product purity, and capable of safe, continuous and stable production. Summary of the invention:

[0019] The purpose of the present invention is to provide a preparation method and a production system for hexafluorobutadiene to achieve safe, stable and reliable production of hexafluorobutadiene.

[0020] The technical route of the present invention is as follows:

[0021]

[0022] To achieve the purpose of this invention, according to the first aspect of the present invention, the following technical solutions are adopted:

[0023] A preparation method for hexafluorobutadiene, characterized in that the preparation method comprises the following steps:

[0024] (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 a reaction is carried out to obtain a solution of zinc trifluorovinyl bromide; this solution and zinc powder are introduced into a second reactor containing zinc powder, an initiator and an organic solvent to completely convert the unreacted bromotrifluoroethylene; the reaction solution enters a sedimentation device to separate the excess zinc powder, and a solution of zinc trifluorovinyl bromide with zinc powder removed is obtained; the organic solvent is selected from polar aprotic organic solvents;

[0025] (2) The zinc powder-removed vinyl bromide zinc trifluoride solution obtained in step (1) and the pre-prepared composite catalyst organic solution are fed into a third reactor for a coupling reaction to obtain a crude hexafluorobutadiene product; the composite catalyst organic solution is composed of an oxidant, a catalytic assistant, and an organic solvent; the catalytic assistant is selected from monovalent copper salts and ferrous salts, and the organic solvent is selected from polar aprotic organic solvents;

[0026] (3) The synthesis liquid obtained in step (2) is fed into a purification system to obtain a purified hexafluorobutadiene product.

[0027] The steps for preparing the vinyl bromide trifluoride solution are as follows:

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

[0029] B. Then introduce a certain amount of vinyl bromide trifluoride, control the temperature in the kettle 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 vinyl bromide zinc trifluoride solution are as follows:

[0031] A. First, add an organic solvent, an initiator, and zinc powder to the first reactor, heat up to a certain temperature under stirring conditions, and at the same time add a solvent, an initiator, and zinc powder to the second reactor, heat up to a certain temperature under stirring conditions, and open the overflow valve of the first reactor so that the materials in the first reactor can overflow into the second reactor;

[0032] B. Continuously add an organic solution of vinyl bromide trifluoride and zinc powder to the first reactor, continuously add zinc powder to the second reactor, open the overflow valve of the second reactor so that the materials in the second reactor can overflow or be pumped to a settling device to obtain a zinc powder-removed vinyl bromide zinc trifluoride solution. The settling device includes multiple settling tanks, preferably a two-stage settling tank. The vinyl bromide zinc trifluoride 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 so that the materials in the first settling tank can overflow or be pumped to the second settling tank to obtain a vinyl bromide zinc trifluoride solution without zinc powder residue. The settling tank can be a settling and pressure filtration tank, sediment the excess zinc powder to the baffle of the settling tank to obtain a vinyl bromide zinc trifluoride solution without zinc powder residue. After the zinc powder in the settling tank is pressure-filtered, it can be directly used in the reaction for preparing the vinyl bromide zinc trifluoride solution.

[0033] The initiator is selected from one of methyl bromide, 1,2-dibromoethane, iodine, trimethylchlorosilane and zinc trifluorovinyl bromide solution, and the molar ratio of the feeding rate (mol / h) of trifluorobromoethylene to the dosage (mol) of the initial initiator is 1:(1-100).

[0034] Preferably, the initiator is selected from one of 1,2-dibromoethane, iodine and zinc trifluorovinyl bromide solution, and the molar ratio of the feeding rate (mol / h) of trifluorobromoethylene to the dosage (mol) of the initial initiator is 1:(1-50). More preferably, the initiator is zinc trifluorovinyl bromide solution.

[0035] During the process of preparing zinc trifluorovinyl bromide solution, the numerical ratio of the feeding rate value of trifluorobromoethylene organic solution in kg / h to the mass value of the first reactor bottom charge in kg is 1:(10-100); the numerical ratio of the feeding rate value of trifluorobromoethylene organic solution in kg / h to the mass value of the second reactor bottom charge in kg is 1:(5-100).

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

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

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

[0039] During the process of preparing zinc trifluorovinyl bromide solution in step (1), the mesh number of zinc powder is 100-500 meshes.

[0040] Preferably, the mesh number of zinc powder is 200-400 meshes.

[0041] In the process of preparing the zinc trifluorovinyl bromide solution in step (1), the organic solvent is selected from polar aprotic organic solvents; the polar aprotic organic solvent is selected from one, two or more combinations 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 ≤500 ppm.

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

[0043] In the process of preparing the zinc trifluorovinyl 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 sodium peroxide, potassium peroxide, sodium perborate, sodium persulfate, potassium persulfate, ammonium persulfate, di-tert-butyl peroxide; the catalytic promoter is selected from cuprous chloride, cuprous bromide, cuprous iodide, ferrous chloride, ferrous bromide; the polar aprotic organic solvent is selected from 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, potassium persulfate; the promoter is selected from cuprous iodide and ferrous chloride. The polar aprotic organic solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

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

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

[0051] In step (3), the purification system is preferably a combination of a distillation device and a rectification device. After the reaction is completed, the reaction solution enters the distillation device, and the product is quickly distilled out and then rectified to obtain a high-purity hexafluorobutadiene product.

[0052] The content of the difficult-to-separate impurity bromotrifluoroethylene in the crude hexafluorobutadiene obtained by distillation is ≤0.1%, the content of heptafluorobutene is ≤0.01%, and the purity of the product after rectification is ≥99.99%.

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

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

[0055] The zinc trifluorovinyl bromide solution reaction unit includes a bromotrifluoroethylene organic solution feeding device, a zinc powder feeding device, a solvent and initiator feeding device, a first reactor and a second reactor; wherein, the bromotrifluoroethylene organic solution feeding device, the zinc powder feeding device, and the solvent and initiator feeding device are connected to the first reactor to feed it; the zinc powder feeding device, the solvent and initiator feeding device are connected to the second reactor to feed it; the first reactor and the second reactor are connected to output the zinc trifluorovinyl bromide solution obtained 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; the discharge of the second reactor is connected to a zinc powder sedimentation device;

[0056] The hexafluorobutadiene preparation unit includes a zinc trifluorovinyl bromide solution feeding device, a composite catalyst solution feeding device, and a third reactor. The zinc trifluorovinyl 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 collection device;

[0058] The rectification unit includes a crude hexafluorobutadiene feeding device, a rectification column, a pre-fraction storage tank, a product collection tank and a rectification residue storage tank.

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

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

[0061] Advantages of the present invention:

[0062] (1) In the preparation step of vinyl trifluoride zinc bromide, a two-stage series reactor is adopted, which not only realizes almost complete conversion of the raw material trifluorobromoethylene, improves the utilization rate of the raw material, but also reduces the pressure for subsequent rectification and purification of the product, which is beneficial to improving the purity of the product.

[0063] (2) In the preparation step of hexafluorobutadiene by oxidative coupling, a cheap peroxide is used as the oxidant, and a catalytic amount of copper salt or iron salt is used as the auxiliary agent. Compared with the traditional process using an equivalent amount of copper salt or iron salt, not only the raw material cost is greatly reduced, the discharge of heavy metal waste solids is reduced, and the environmental pressure is relieved. At the same time, using an inorganic peroxide as the oxidant can reduce the generation of difficult-to-separate impurity fluoroolefins compared with using a metal chloride as the oxidant, which is beneficial to improving the product purity. Description of the drawings

[0064] Figure 1 It is a schematic diagram of the vinyl trifluoride zinc bromide solution preparation unit and the zinc powder filtration unit in the embodiment of the present invention.

[0065] Figure 2 It is a schematic diagram of the hexafluorobutadiene preparation unit and the distillation unit in the embodiment of the present invention.

[0066] Figure 3 It is a chromatogram analysis spectrum of the hexafluorobutadiene product prepared in Example 15 of the present invention. Detailed implementation manners

[0067] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific implementation manners. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions, and equivalent solutions that may be included within the scope of the claims.

[0068] First, the production system for preparing hexafluorobutadiene of the present invention will be described in conjunction with the drawings.

[0069] The preparation and production system of 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;

[0070] The trifluorovinyl zinc bromide solution reaction unit includes a trifluorobromoethylene organic solution feeding device, a zinc powder feeding device, a solvent and initiator feeding device, a first reactor 3, and a second reactor 4.

[0071] The trifluorobromoethylene organic solution feeding device includes a trifluorobromoethylene solution storage tank 1, and the solvent and initiator feeding device includes an initiator or solvent storage tank 2, which respectively feed to the corresponding feeding parts at the upper part of the first reactor 3 by pumping or gravity. The zinc powder feeding device includes a zinc powder storage tank 5, which feeds by gravity. The first reactor 3 and the second reactor 4 are connected and output the trifluorovinyl zinc bromide solution obtained by the reaction in the first reactor 3 to the second reactor 4. The second reactor 4 is also connected to the zinc powder feeding device, and this zinc powder feeding device can use a zinc powder storage tank 6, which feeds by gravity. The upper parts of the first reactor 3 and the second reactor 4 are respectively connected to a vacuum device through condensers 7 and 8; the discharge port of the second reactor 4 is connected to the zinc powder filtration unit; the zinc powder filtration unit can use two-stage sedimentation tanks, namely a first sedimentation tank 9 and a second sedimentation tank 10, and the discharge of the second sedimentation tank 10 is connected to a trifluorovinyl zinc bromide solution storage tank 11, and the trifluorovinyl zinc bromide solution storage tank 11 can be used as a material buffer link for production.

[0072] The hexafluorobutadiene preparation 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, and 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 trifluorovinyl zinc bromide solution storage tank 12, and this storage tank and the trifluorovinyl zinc bromide solution storage tank 11 can be the same one. The trifluorovinyl zinc bromide solution feeding device feeds to the third reactor 14 by pumping. The composite catalyst solution feeding device includes a composite catalyst solution storage tank 13, and feeds to the third reactor 14 by pumping.

[0073] The distillation unit includes a hexafluorobutadiene synthesis liquid feeding device, a distillation device and a product collection device. The outlet end of the third reactor 14 can be connected to a hexafluorobutadiene synthesis liquid buffer tank 15.

[0074] The distillation unit includes a hexafluorobutadiene synthesis liquid feeding device, a distillation device and a product collection device.

[0075] The hexafluorobutadiene synthesis liquid feeding device includes a hexafluorobutadiene synthesis liquid buffer tank 15, which feeds materials to two parallel purification systems respectively by pumping. The first purification system includes a first distillation device 16. The first distillation device 16 is connected to a hexafluorobutadiene buffer tank 20 through a condenser 18, and the hexafluorobutadiene buffer tank 20 is connected to a hexafluorobutadiene crude product tank 21 through a condenser 19. The second purification system includes a second distillation device 17. The second distillation device 17 is connected to a hexafluorobutadiene buffer tank 24 through a condenser 22, and the hexafluorobutadiene buffer tank 24 is connected to a hexafluorobutadiene crude product tank 25 through a condenser 23. The hexafluorobutadiene crude product tank 25 is then connected to a rectification device. The attached reference numeral 26 is a distillation residue storage tank.

[0076] The following examples utilize the above production system.

[0077] Example 1

[0078] (1) In a 500L first reactor made of 316L material, 300 kg of an N,N-dimethylformamide solution of zinc trifluorovinyl bromide with a mass fraction of 25% was put in, stirring was started, 65 kg of zinc powder was put in, and the reactor was heated to 80 °C.

[0079] (2) In a 500L second reactor made of 316L material, 300 kg of an N,N-dimethylformamide solution of zinc trifluorovinyl bromide with a mass fraction of 25% was put in, stirring was started, 32.5 kg of zinc powder was put in, and the reactor was heated to 60 °C.

[0080] (3) An N,N-dimethylformamide solution of trifluorobromoethylene (mass fraction 20%) was added to the first reactor, and the flow rate was controlled at (15 kg / h); at the same time, zinc powder (325 mesh, 1.3 kg / h) was added to the first reactor through a solid feeding device.

[0081] (4) The overflow port valve connecting the first reactor and the second reactor was opened. When the material level in the first reactor exceeded the height of the overflow port, it entered the second reactor; at the same time, zinc powder (325 mesh, 0.35 kg / h) was added to the second reactor through a solid feeding device.

[0082] (5) The overflow port valve connecting the second reactor and the first sedimentation tank was opened. When the material level in the second reactor exceeded the height of the overflow port, it entered the first sedimentation tank, and the excessive zinc powder in the reaction was sedimented to the baffle.

[0083] (6) The connection valve between the first sedimentation tank and the second sedimentation tank was opened. When the material level in the first sedimentation tank exceeded the height of the valve outlet, the material transfer pump was turned on to transfer the material to the second sedimentation tank, and the remaining zinc powder was sedimented to the baffle.

[0084] (7) Open the valve connecting the second sedimentation tank and the storage tank for zinc trifluorovinyl bromide solution. When the liquid level of the material in the second sedimentation tank exceeds the height of the valve outlet, turn on the material transfer pump and transfer the material to the storage tank. Operate for 72 h, take a sample from the storage tank for zinc trifluorovinyl bromide solution and analyze it. The results are as follows: the normalized content of bromotrifluoroethylene is 0.005%, the mass fraction of zinc trifluorovinyl bromide is 25.1% (by internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 96.5%.

[0085] Example 2

[0086] The operation of this example is the same as that of Example 1, except that: the N,N-dimethylformamide solution of bromotrifluoroethylene (mass fraction 20%) with a flow rate of (15 kg / h) is replaced by the N,N-dimethylformamide solution (mass fraction 20%) with a flow rate of (20 kg / h); adding zinc powder (325 mesh, 1.3 kg / h) to the first reactor is replaced by adding zinc powder (325 mesh, 1.8 kg / h) to the first reactor; adding zinc powder (325 mesh, 0.35 kg / h) to the second reactor is replaced by adding zinc powder (325 mesh, 0.48 kg / h) to the second reactor, and other conditions remain unchanged. Operate for 72 h, take a sample from the storage tank for zinc trifluorovinyl bromide solution and analyze it. The results are as follows: the normalized content of bromotrifluoroethylene is 0.008%, the mass fraction of zinc trifluorovinyl bromide is 24.4% (by internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 93.8%.

[0087] Example 3:

[0088] The operation of this example is the same as that of Example 1, except that: adding zinc powder (325 mesh, 0.35 kg / h) to the second reactor is replaced by adding zinc powder (325 mesh, 0.20 kg / h)

[0089] Other conditions remain unchanged. Operate for 72 h, take a sample from the storage tank for zinc trifluorovinyl bromide solution and analyze it. The results are as follows: the normalized content of bromotrifluoroethylene is 0.006%, the mass fraction of zinc trifluorovinyl bromide is 24.7% (by internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 95.0%.

[0090] Example 4

[0091] The operation of this example is the same as that of Example 1, except that: the mesh number of zinc powder is replaced from 325 mesh to 500 mesh, and other conditions remain unchanged. Operate for 72 h, take a sample from the storage tank for zinc trifluorovinyl bromide solution and analyze it. The results are as follows: the normalized content of bromotrifluoroethylene is 0.01%, the mass fraction of zinc trifluorovinyl bromide is 22.2% (by internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 85.3%.

[0092] Example 5

[0093] The operation of this example is the same as that of Example 1, except that: the temperature of the first reactor is replaced from 80 °C to 60 °C, and other conditions remain unchanged. After running for 72 h, a sample is taken from the zinc trifluorovinyl bromide solution storage tank for analysis. The results are as follows: the normalized content of bromotrifluoroethylene is 0.012%, the mass fraction of zinc trifluorovinyl bromide is 21.7% (internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 83.3%.

[0094] Example 6

[0095] The operation of this example is the same as that of Example 1, except that: the temperature of the second reactor is replaced from 60 °C to 70 °C, and other conditions remain unchanged. After running for 72 h, a sample is taken from the zinc trifluorovinyl bromide solution storage tank for analysis. The results are as follows: the normalized content of bromotrifluoroethylene is 0.005%, the mass fraction of zinc trifluorovinyl bromide is 24.9% (internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 95.8%.

[0096] Example 7

[0097] The operation of this example is the same as that of Example 1, except that: the N,N-dimethylformamide solution of 25% mass fraction of zinc trifluorovinyl bromide input into the first and second reactors is replaced by the N,N-dimethylacetamide solution of 25% mass fraction of zinc trifluorovinyl bromide input into the first and second reactors. The N,N-dimethylformamide solution (mass fraction of 20%) of bromotrifluoroethylene added to the first reactor is replaced by the N,N-dimethylacetamide solution (mass fraction of 20%) of bromotrifluoroethylene added to the first reactor. Other conditions remain unchanged. After running for 72 h, a sample is taken from the zinc trifluorovinyl bromide solution storage tank for analysis. The results are as follows: the normalized content of bromotrifluoroethylene is 0.007%, the mass fraction of zinc trifluorovinyl bromide is 23.9% (internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 91.9%.

[0098] Example 8

[0099] The operation of this example is the same as that of Example 1, except that: zinc powder is replaced by the zinc powder recovered from the first sedimentation tank. Other conditions remain unchanged. After running for 72 h, a sample is taken from the zinc trifluorovinyl bromide solution storage tank for analysis. The results are as follows: the normalized content of bromotrifluoroethylene is 0.006%, the mass fraction of zinc trifluorovinyl bromide is 24.3% (internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction is 26%, and the average yield is 93.5%.

[0100] Comparative Example 1

[0101] The reaction is carried out in a single reactor to prepare a zinc trifluorovinyl bromide solution. The operation steps are as follows:

[0102] (1) In a 500L first reactor made of 316L material, 300 kg of an N,N-dimethylformamide solution containing 25% by mass of zinc bromide trifluorovinyl was charged. Stirring was started, 65 kg of zinc powder was charged, and the reactor was heated to 80 °C.

[0103] (2) An N,N-dimethylformamide solution of bromotrifluoroethylene (mass fraction 20%) was added to the first reactor, and the flow rate was controlled at (15 kg / h); at the same time, zinc powder (325 mesh, 1.3 kg / h) was added to the first reactor through a solid feeding device.

[0104] (3) The valve between the first reactor and the overflow port of the first settling tank was opened. When the liquid level of the material in the second reactor exceeded the height of the overflow port, it entered the first settling tank, and the excessive zinc powder in the reaction was settled to the baffle.

[0105] (4) The valve connecting the first settling tank and the second settling tank was opened. When the liquid level of the material in the first settling tank exceeded the height of the valve outlet, the material transfer pump was turned on, and the material was transported to the second settling tank, and the residual zinc powder was settled to the baffle.

[0106] (5) The valve connecting the second settling tank and the zinc bromide trifluorovinyl solution storage tank was opened. When the liquid level of the material in the second settling tank exceeded the height of the valve outlet, the material transfer pump was turned on, and the material was transported to the storage tank. After operating for 72 h, a sample was taken from the zinc bromide trifluorovinyl solution storage tank for analysis. The results were as follows: the normalized content of bromotrifluoroethylene was 1.56%, the mass fraction of zinc bromide trifluorovinyl was 20.2% (internal standard method of nuclear magnetic resonance fluorine spectrum), the theoretical mass fraction was 26%, and the average yield was 77.8%.

[0107] Example 9

[0108] (1) 300 kg of N,N-dimethylformamide was added to a 500L glass-lined reactor. Under stirring conditions, ammonium persulfate (40 kg, 175 mol) and cuprous iodide (0.67 kg, 3.5 mol) were added, and the internal temperature was maintained at 0 - 5 °C to complete the preparation of the oxidant solution. The concentration of the oxidant was 0.51 mol / kg, and the concentration of the auxiliary agent was 0.01 mol / kg.

[0109] (2) The above-prepared oxidant solution (flow rate 40 kg / h, corresponding to an ammonium persulfate flow rate of 20.4 mol / h and a cuprous iodide flow rate of 0.4 mol / h) and a zinc bromide trifluorovinyl solution (mass fraction 25%, flow rate 16.8 kg / h, corresponding to 18.6 mol / h of zinc bromide trifluorovinyl) were added to a 316L spiral reaction tube (total length 10 m, inner tube diameter 8 mm). The internal temperature was controlled at 0 - 5 °C, and the pressure in the reaction tube was 0.05 MPa.

[0110] (3) The synthesized liquid enters distillation device A or B from the outlet of the reaction tube. The temperature in the kettle is 60 °C, and the vacuum degree in the kettle is 0.1 MPa. The crude hexafluorobutadiene is collected by condensation after the vacuum pump, and the temperature of the condenser is -15 °C. After running for 72 h, the results are as follows: 107.6 kg of crude hexafluorobutadiene is collected from the crude product tank behind the pump, with the main content being 95.33% (the contents of other impurities are shown in Table 1 below). The yield in terms of 100% purity is 102.6 kg, the theoretical output is 108.5 kg, and the average yield is 94.6%.

[0111] Example 10

[0112] The operation of this example is the same as that of Example 9, except that: the oxidant solution configured above (flow rate: 60 kg / h, equivalent to ammonium persulfate flow rate: 30.6 mol / h, copper(I) iodide flow rate: 0.6 mol / h) and the zinc trifluorovinyl bromide solution (mass fraction: 25%, flow rate: 25.2 kg / h, equivalent to zinc trifluorovinyl bromide: 27.9 mol / h) are added, and other conditions remain unchanged. After running for 72 h, the results are as follows: 156.1 kg of crude hexafluorobutadiene is collected from the crude product tank behind the pump, with the main content being 95.81% (the contents of other impurities are shown in Table 1 below). The yield in terms of 100% purity is 149.5 kg, the theoretical output is 162.8 kg, and the average yield is 91.8%.

[0113] Example 11

[0114] The operation of this example 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 assistant concentration is 0.01 mol / kg.

[0115] In step (2), the oxidant solution (flow rate: 40 kg / h, equivalent to ammonium persulfate flow rate: 20.4 mol / h, copper(I) iodide flow rate: 0.4 mol / h) is replaced by the oxidant solution (flow rate: 47.4 kg / h, equivalent to potassium persulfate flow rate: 20.4 mol / h, copper(I) iodide flow rate: 0.4 mol / h), and other conditions remain unchanged. After running for 72 h, the results are as follows: 104.3 kg of crude hexafluorobutadiene is collected from the crude product tank behind the pump, with the main content being 93.80% (the contents of other impurities are shown in Table 1 below). The yield in terms of 100% purity is 97.8 kg, the theoretical output is 108.5 kg, and the average yield is 90.1%.

[0116] Example 12

[0117] The operation of this example is the same as that of Example 9, except that: in step (1), cuprous iodide (0.67 kg, 3.5 mol) is replaced by ferrous chloride (0.70 kg, 3.5 mol). Other conditions remain unchanged. After running for 72 h, the results are as follows: 109.4 kg of hexafluorobutadiene crude product is collected from the crude product tank behind the pump, with the main content being 94.68% (the contents of other impurities are shown in Table 1 below). The yield after conversion to 100% purity is 103.6 kg, the theoretical yield is 108.5 kg, and the average yield is 95.5%.

[0118] Example 13

[0119] The operation of this example is the same as that of Example 9, except that: in step (1), cuprous iodide (0.67 kg, 3.5 mol) is replaced by cuprous iodide (1.33 kg, 7.0 mol), and after completing the preparation of the oxidant solution, the concentration of the auxiliary agent is changed from 0.01 mol / kg to 0.02 mol / kg. In step (2), the flow rate of cuprous iodide is changed from 0.4 mol / h to 0.8 mol / h. Other conditions remain unchanged. After running for 72 h, the results are as follows: 107.4 kg of hexafluorobutadiene crude product is collected from the crude product tank behind the pump, with the main content being 95.02% (the contents of other impurities are shown in Table 1 below). The yield after conversion to 100% purity is 102.0 kg, the theoretical yield is 108.5 kg, and the average yield is 94.0%.

[0120] Example 14

[0121] The operation of this example is the same as that of Example 9, except that: maintaining the internal temperature at 0 - 5°C is replaced by maintaining the internal temperature at 5 - 10°C, and in step (2), controlling the internal temperature at 0 - 5°C is replaced by 5 - 10°C. Other conditions remain unchanged. After running for 72 h, the results are as follows: 107.1 kg of hexafluorobutadiene crude product is collected from the crude product tank behind the pump, with the main content being 94.25% (the contents of other impurities are shown in Table 1 below). The yield after conversion to 100% purity is 100.9 kg, the theoretical yield is 108.5 kg, and the average yield is 93.0%.

[0122] Comparative Example 3

[0123] The operation of this example is the same as that of Example 9, except that: in step (1), the auxiliary agent cuprous iodide is not added during the preparation of the oxidant solution. Other conditions remain unchanged. After running for 72 h, the results are as follows: 10.7 kg of hexafluorobutadiene crude product is collected from the crude product tank behind the pump, with the main content being 66.51% (the contents of other impurities are shown in Table 1 below). The yield after conversion to 100% purity is 7.1 kg, the theoretical yield is 108.5 kg, and the average yield is 6.5%.

[0124] Comparative Example 4

[0125] The operation of this example is the same as that of Example 9, with the only difference being that: in step (3), the hexafluorobutadiene synthesis liquid is subjected to batch distillation in a kettle. The synthesis liquid that has been running for 72 hours is fed into the distillation device all at once, and other conditions remain unchanged. The results are as follows: 98.3 kg of hexafluorobutadiene crude product is 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 yield after conversion to 100% is 92.3 kg, the theoretical yield is 108.5 kg, and the average yield is 85.1%.

[0126] Comparative Example 5

[0127] The operation of this example is the same as that of Example 9, with the only difference being that: in step (1), an equimolar amount of iron salt oxidant is used to replace the persulfate oxidant during the preparation of the oxidant solution, specifically as follows:

[0128] (1) Add 300 kg of N,N-dimethylformamide to a 500 L glass-lined reactor, and add ferric chloride (28.4 kg, 0.175 kmol) under stirring conditions. Maintain the internal temperature at 0 - 5 °C to complete the preparation of the oxidant solution, and the concentration of the oxidant is 0.53 mol / kg.

[0129] (2) Add the above-prepared oxidant solution (flow rate: 38.5 kg / h, equivalent to a ferric chloride flow rate of 20.4 mol / h) and zinc trifluorovinyl bromide solution (mass fraction 25%, flow rate: 16.8 kg / h, equivalent to 18.6 mol / h of zinc trifluorovinyl bromide) to a 316 L spiral reaction tube (total length 10 m, inner tube diameter 8 mm). Control the internal temperature at 0 - 5 °C, and the pressure inside the reaction tube is 0.05 MPa.

[0130] Step (3) is the same as that of Example 9 and runs for 72 hours. The results are as follows: 102.7 kg of hexafluorobutadiene crude product is 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 yield after conversion to 100% is 90.9 kg, the theoretical yield is 108.5 kg, and the average yield is 83.8%.

[0131] Table 1 Composition table of hexafluorobutadiene crude products prepared in Examples 9 - 14 and Comparative Examples 3 - 5

[0132]

[0133] Example 15

[0134] Using the hexafluorobutadiene crude product prepared in Example 9 as the raw material, a rectification experiment is carried out. The rectification tower parameters and rectification parameters are shown in Tables 2 and 3 below:

[0135] Table 2 Rectification tower parameters

[0136] Reboiler volume Column inner diameter Column height Packing Number of theoretical plates 100L 80mm 8m CY700 30

[0137] Table 3 Distillation Process Parameters

[0138] External temperature of reboiler Reboiler pressure Condenser medium temperature Reflux ratio 60℃ 0.1 - 0.3MPa 0～5℃ 5:1～10:1

[0139] For the distillation feed of 100 kg, 22.6 kg of the fore-fraction, 65.7 kg of the product, and 10.5 kg of the residue are obtained. The purity of the product is 99.9908%, the single-batch distillation yield is 65.7%, and the material balance rate is 98.8%.

[0140]

Claims

1. A preparation method of hexafluorobutadiene, characterized in that the preparation method comprises the following steps: (1) An organic solution of trifluorobromoethylene and zinc powder are introduced into a first reactor containing an initiator, zinc powder and an organic solvent, and a solution of zinc trifluorovinyl bromide is obtained through reaction; this solution and zinc powder are introduced into a second reactor containing zinc powder, an initiator and an organic solvent to completely convert the unreacted trifluorobromoethylene; the reaction solution is introduced into a sedimentation device to separate the excess zinc powder, and a zinc powder-removed solution of zinc trifluorovinyl bromide is obtained; the organic solvent is selected from polar aprotic organic solvents; (2) The zinc powder-removed solution of zinc trifluorovinyl bromide obtained in step (1) and a pre-prepared organic solution of a composite catalyst are introduced into a third reactor for a coupling reaction to obtain a crude product of hexafluorobutadiene; the organic solution of the composite catalyst is composed of an oxidant, a catalytic assistant and an organic solvent; the catalytic assistant is selected from monovalent copper salts and ferrous salts, and the organic solvent is selected from polar aprotic organic solvents; (3) The synthetic solution obtained in step (2) is introduced into a purification system to obtain purified hexafluorobutadiene.

2. The preparation method of hexafluorobutadiene according to claim 1, characterized in that the initiator is selected from methyl bromide, 1,2-dibromoethane, iodine, trimethylchlorosilane and a reagent solution of zinc trifluorovinyl bromide.

3. The preparation method of hexafluorobutadiene according to claim 1, characterized in that the initiator is selected from 1,2-dibromoethane, trimethylchlorosilane and zinc trifluorovinyl bromide reagent, and the numerical ratio of the feed rate value of trifluorobromoethylene in mol / h to the molar value of the amount of the initial initiator used is 1:(1 - 100).

4. The preparation method of hexafluorobutadiene according to claim 1, characterized in that the mass concentration of the trifluorobromoethylene organic solution is 5 - 30%; during the reaction process, the numerical ratio of the feed rate value of the trifluorobromoethylene organic solution in kg / h to the mass value of the first reactor bottom charge in kg is 1:(10 - 100); the numerical ratio of the feed rate value of the trifluorobromoethylene organic solution in kg / h to the mass value of the second reactor bottom charge in kg is 1:(5 - 100); the molar ratio of trifluorobromoethylene to the feed rate of zinc powder in the first reactor is 1:(1.0 - 5.0), and the molar ratio of trifluorobromoethylene to the feed rate of zinc powder in the second reactor is 1:(0.1 - 2.0).

5. The preparation method of hexafluorobutadiene according to claim 1, characterized in that the mesh number of the zinc powder is 100 - 500 mesh; the polar aprotic organic solvent in step (1) is selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide and N-methylpyrrolidone, and the water content of the polar aprotic organic solvent is ≤500 ppm.

6. The method for preparing hexafluorobutadiene according to claim 1, characterized in that the temperature range of the first reactor is 60 - 120 °C, and the temperature range of the second reactor is 60 - 90 °C.

7. The preparation method of hexafluorobutadiene according to claim 1, It is characterized in that the sedimentation device includes multiple sedimentation tanks.

8. The preparation method of hexafluorobutadiene according to claim 1, It is characterized in that the sedimentation device includes two stages, namely a first sedimentation tank and a second sedimentation tank. The zinc trifluorovinyl bromide solution prepared in step (1) enters the first sedimentation tank and the second sedimentation tank in sequence through an overflow or pump transportation method, and the excessive zinc powder is sedimented to obtain a zinc trifluorovinyl bromide solution without zinc powder residue.

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

10. The preparation method of hexafluorobutadiene according to claim 1, It is characterized in that the oxidant in the composite catalyst organic solution in step (2) is selected from sodium peroxide, potassium peroxide, sodium perborate, sodium persulfate, potassium persulfate, ammonium persulfate, di-tert-butyl peroxide; the catalytic assistant is selected from cuprous chloride, cuprous bromide, cuprous iodide, ferrous chloride, ferrous bromide; the polar aprotic organic solvent in step (2) is selected from one of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide and N-methylpyrrolidone.

11. The preparation method of hexafluorobutadiene according to claim 1, It is characterized in that in step (2), the molar ratio of zinc trifluorovinyl bromide to the oxidant is 1:(1.0 - 3.0); the molar ratio of zinc trifluorovinyl bromide to the catalytic assistant in the zinc trifluorovinyl bromide solution is 1:(0.01 - 0.2).

12. The preparation method of hexafluorobutadiene according to claim 1, It is 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.

13. The preparation method of hexafluorobutadiene according to claim 1, It is characterized in that in step (3), the synthesis liquid obtained in step (2) is distilled to obtain a crude hexafluorobutadiene product, and then through rectification, a pure hexafluorobutadiene product is obtained.

14. The preparation method of hexafluorobutadiene according to claim 13, It is characterized in that the content of trifluorobromoethylene in the crude hexafluorobutadiene product obtained by distillation is ≤0.1%, the content of heptafluorobutene is ≤0.01%, and the product purity after rectification is ≥99.99%.

15. A preparation production system for hexafluorobutadiene, It is characterized in that the preparation production system is used for the preparation method described in any one of claims 1 - 14, and includes a zinc trifluorovinyl bromide solution preparation unit, a hexafluorobutadiene preparation unit, a zinc powder filtration unit, a distillation unit and a rectification unit; The zinc trifluorovinyl bromide solution reaction unit includes a trifluorobromoethylene organic solution feeding device, a zinc powder feeding device, a solvent and initiator feeding device, a first reactor, and a second reactor; wherein, the trifluorobromoethylene organic solution feeding device, the zinc powder feeding device, and the solvent and initiator feeding device are connected to the first reactor to feed materials thereto; the zinc powder feeding device, the solvent and initiator feeding device are connected to the second reactor to feed materials thereto; the first reactor and the second reactor are connected to output the zinc trifluorovinyl 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 condensers; the discharge of the second reactor is connected to a zinc powder sedimentation device; The hexafluorobutadiene preparation unit includes a zinc trifluorovinyl bromide solution feeding device, a composite catalyst solution feeding device, and a third reactor, and the zinc trifluorovinyl bromide solution feeding device and the composite catalyst solution feeding device are connected to the inlet end of the third reactor; The distillation unit includes a hexafluorobutadiene synthesis liquid feeding device, a distillation device, and a product collection device; The rectification unit includes a hexafluorobutadiene crude product feeding device, a rectification column, a pre-fraction storage tank, a product collection tank, and a rectification residue storage tank.

16. A production system for preparing hexafluorobutadiene according to claim 14, characterized in that The materials of each device in the zinc trifluorovinyl bromide solution reaction unit and the hexafluorobutadiene preparation unit are selected from one of glass-lined, carbon steel, 316L, and fluorine-lined resin carbon steel; the material of the zinc powder filtration unit device is selected from one of carbon steel, 304, and 316L; the material of the distillation unit device is selected from one of glass-lined, 304, and 316L.

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