A process for the preparation of hexafluorobutadiene

Abstract

The application provides a preparation method of hexafluorobutadiene, 1) under normal temperature and pressure, chlorotrifluoroethylene and liquid bromine are subjected to an electrophilic addition reaction to generate 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane are mixed with an aprotic polar solvent to generate a zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride; 3) a catalyst is added, and the zinc reagent is subjected to a self-coupling reaction to generate an intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane; 4) the intermediate product is subjected to dehalogenation to generate hexafluorobutadiene; and the method has the effects of simple reaction process, low danger, relatively mild reaction conditions and high yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of hexafluorobutadiene, and particularly relates to a preparation method of hexafluorobutadiene. BACKGROUND

[0002] With the rapid development of domestic photoelectric industry, especially the development of semiconductor industry, the demand for dry etching gas is also growing. Hexafluorobutadiene (C4F6) is a perfluorinated compound, its boiling point is 6℃, density 1.4g·mL -1 , and its application potential in the chip industry is gradually developed. Studies show that compared with other commonly used etching gases, hexafluorobutadiene can perform dry etching on a width of less than 100nm, has higher selectivity and accuracy. Hexafluorobutadiene has high application value in the synthesis of fluorine-containing fine chemicals such as fluorine-containing pharmaceutical intermediates. In the synthesis of fluorine-containing polymers, hexafluorobutadiene can be used as a polymer monomer to prepare polyhexafluorobutadiene, and can also be synthesized with other monomers to prepare fluorine-containing rubber and resin with good electrical properties. Hexafluorobutadiene is a green and environmentally friendly high-efficiency dry etching gas with low greenhouse effect, and its atmospheric lifetime is less than 2d, and the greenhouse effect coefficient GWP 100 is less than 300.

[0003] At present, there are many routes for preparing hexafluorobutadiene, such as 1,2-dichlorodifluoroethylene route, tetrafluoroethylene route, 1,1,1,3-tetrafluoroethane route and chlorotrifluoroethylene route. Literature GB798407 reports a synthesis route using 1,2-dichlorodifluoroethylene as raw material, which needs to be carried out under the conditions of pressure 13.3MPa, temperature 275℃ and good stirring. Literature CA509738 reports a synthesis route using tetrafluoroethylene as raw material, which is flammable and explosive, and has a risk of carcinogenesis. The reaction needs to be carried out at-80℃ with butyllithium-containing hexane solution, which has high risk. Literature CN101432253A reports a synthesis route using 1,1,1,2-tetrafluoroethane as raw material, which needs to use liquid bromine in the reaction process, has high cost, certain risk and more reaction steps. Literature US3046304A reports a synthesis route using chlorotrifluoroethylene as raw material, which needs to use mercury or dioxane, and has certain risk. Literature US2668182A reports a synthesis route using chlorotrifluoroethylene as raw material, which needs high temperature for thermal catalytic coupling, and has more impurities in the product. The reaction needs to add chlorine and then separate, which has high cost and certain risk.

[0004] Therefore, it is necessary to develop a new preparation method of hexafluorobutadiene, which has simple reaction process, low risk, relatively mild reaction conditions and high yield. SUMMARY

[0005] The present application aims to provide a preparation method of hexafluorobutadiene, which can realize simple reaction process, low danger and preparation of hexafluorobutadiene with high yield under relatively mild conditions.

[0006] To solve the above technical problems, the technical scheme provided by the present application is:

[0007] A preparation method of hexafluorobutadiene, comprising the following steps in sequence:

[0008] 1) Under normal temperature and pressure, electrophilic addition reaction of trifluorochloroethylene and liquid bromine to generate 1,2-dibromo-1-chloro-1,2,2-trifluoroethane;

[0009] 2) The zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane are fully mixed with an aprotic polar solvent, and under the help of the aprotic polar solvent, the zinc powder attacks the carbon-halogen bond on 1,2-dibromo-1-chloro-1,2,2-trifluoroethane, and the reaction obtains a zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride;

[0010] 3) With iron salt or copper salt as catalyst, self-coupling reaction of the zinc reagent to generate an intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane;

[0011] 4) Dehalogenation of the intermediate product under the action of zinc powder to generate the target product hexafluorobutadiene.

[0012] Preferably, in step 1), the normal temperature is 15-30℃, and the normal pressure is 0.100-0.103 MPa.

[0013] Preferably, in step 2), the aprotic polar solvent is one or more combinations of tetrahydrofuran, N,N-dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N,N-diisopropylethylamine, benzene and toluene, and the water content is less than 100 ppm.

[0014] Preferably, in step 2), the molar ratio of the zinc powder to 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is 1:(0.8-1.2), and the temperature of the added zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is -10-20℃.

[0015] Preferably, in step 2), the temperature of the reaction for generating the zinc reagent is -20℃ to 30℃, and the reaction time is 2h to 4h.

[0016] Preferably, in step 3), the catalyst is one or more of ferric chloride, ferric bromide, cupric chloride, and cupric bromide, and the water content is less than 100ppm, the temperature of the zinc reagent when added is -10℃ to 10℃, and the molar ratio of the zinc reagent to the catalyst is 1:1.

[0017] Preferably, in step 3), the temperature of the coupling reaction after adding the ferric salt or the cupric salt is 40℃ to 80℃, and the coupling reaction time is 4h.

[0018] Preferably, in step 4), the molar ratio of the zinc powder to the intermediate product is (2-6):1, and the reaction temperature is 50℃ to 80℃.

[0019] The present application has the following beneficial technical effects:

[0020] (1). The reaction process of the present preparation method is simple, mainly reflected in three aspects: the raw materials are easier to obtain (no need for pretreatment), the reaction process is relatively simple, and the reaction equipment is simple. The main raw material of the present preparation method is trifluorochloroethylene, which is easy to obtain and does not need additional pretreatment for subsequent reactions. The reaction process of the present preparation method mainly includes four steps, each of which is carried out under relatively mild reaction conditions, without the need for pressure operation or high-temperature operation, and the operation is simple. The reaction equipment required by the present preparation method is simple. Since the reaction conditions are mild during the reaction process, no pressure or high-temperature operation is required, and a glass equipment with good airtightness can be used.

[0021] (2). The present preparation method has low risk, mainly reflected in four aspects: low toxicity of raw materials, mild reaction process, safe operation process, and stable process flow. The main raw material of the present preparation method is trifluorochloroethylene, which has low toxicity. The reaction process of the present preparation method is mild, with a total reaction temperature not exceeding 80℃, and the reaction process is not under pressure. The operation process of the present preparation method is safe. Since the reaction temperature does not need to exceed 80℃ and the reaction is not under pressure, the present preparation method mainly includes four steps, all of which do not require pressure and can be carried out under normal pressure. Step 1) trifluorochloroethylene bromination can be carried out at room temperature; step 2) zinc reagent preparation, the temperature of zinc powder addition and reaction process is -20~30℃; step 3) and step 4), the temperature of zinc reagent coupling reaction and dehalogenation reaction process does not need to exceed 80℃. There is no high-temperature operation and pressure operation. The process flow of the present preparation method is stable. The four steps of the present preparation method are stable, and no large amount of heat is released and the pressure does not rise sharply during the reaction process.

[0022] (3). The reaction conditions of the preparation method are relatively mild, mainly reflected in that the reaction conditions do not require high or low temperature, and do not require a pressurized reaction. The preparation method mainly comprises four steps. Step 1) The bromination of trifluorochloroethylene belongs to an electrophilic addition reaction, which can be carried out at normal temperature and pressure. Step 2) The preparation of zinc reagent, the temperature during the addition of zinc powder and the reaction process is-20℃ to 30℃, and there is no pressure requirement. This step is carried out at normal pressure. Steps 3) and 4), the coupling reaction of zinc reagent and the dehalogenation reaction are steps with higher temperature requirements in the preparation method, and the reaction process temperature still does not need to exceed 80℃, and there is no pressure requirement. These steps are carried out at normal pressure.

[0023] (4). The preparation method mainly comprises four steps, and due to the high yield of each step, the final preparation method has a relatively high yield (55-70% yield) of the product hexafluorobutadiene. Step 1) The bromination of trifluorochloroethylene has high selectivity and conversion rate (the yield is in the range of 90-95%) for the intermediate product 1,2-dibromo-1-chloro-1,2,2-trifluoroethane. Steps 2) and 3) The preparation and coupling process of zinc reagent do not have the high conversion rate of step 1), but through the design of the reaction system (the selection of aprotic solvents and the control of reaction conditions) make the two steps have less side reactions, high selectivity, and therefore also have good yield (according to different reaction conditions, the yield varies greatly, and the optimal yield of step 2) is 87% and 88% respectively). Step 4) The dehalogenation process has a very high yield (the yield can be close to 99% at the highest). Combined with each step, reasonable process connection and complementary reaction characteristics form a set of efficient and stable synthesis path, so that the preparation method has a relatively high yield.

[0024] In the present application, trifluorochloroethylene with low price is used as the raw material, the material is easy to obtain, the reaction device is simple, the reaction process is simple, and the reaction conditions are relatively mild, without the need for very high reaction temperature. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The mass spectrum result statistical diagram of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane of Example 1;

[0026] Figure 2 The mass spectrum result statistical diagram of hexafluorobutadiene of Example 1. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Referring to reaction equations 1, 2, 3, and 4, this invention provides a method for preparing hexafluorobutadiene, comprising the following steps performed sequentially:

[0029] 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: Trifluorochloroethylene was slowly and uniformly introduced into liquid bromine at room temperature and pressure. Trifluorochloroethylene and liquid bromine underwent an electrophilic addition reaction. As trifluorochloroethylene was continuously introduced and the reaction proceeded, the initially dark reddish-brown liquid bromine gradually became lighter in color. The color change of the liquid bromine was continuously observed until the color of the liquid bromine completely disappeared. The reaction yielded a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane, and its composition was analyzed by gas chromatography.

[0030] 2) Preparation of a zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: At a certain temperature (-10℃ to 20℃ below), zinc powder and an aprotic polar solvent are first thoroughly mixed in a flask to form a suspension system. Then, the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) is added. After stirring to ensure thorough mixing of the three components, the zinc powder attacks the carbon-halogen bond with the help of the aprotic polar solvent. After reacting at a certain temperature for a period of time, a highly active zinc reagent is obtained. Its composition is analyzed by nuclear magnetic resonance fluorine spectroscopy.

[0031] The aprotic polar solvent is one or more combinations of tetrahydrofuran, N,N-dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, 1,3-dimethyl-2-imidazolinone, N-methylpyrrolidone, N,N-diisopropylethylamine, benzene, and toluene, with a water content of less than 100 ppm;

[0032] The molar ratio of zinc powder to 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is 1:(0.8~1.2), and the temperature at which the zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane are added is -10℃~20℃;

[0033] The reaction temperature for generating the zinc reagent is -20℃ to 30℃;

[0034] The reaction time for generating the zinc reagent is 2–4 hours;

[0035] The aprotic polar solvent has excellent solvent effect, which makes the reactant molecules more easily solvated; while not providing protons, it binds with the leaving group through van der Waals force or hydrogen bond to accelerate the leaving of the leaving group, which is more conducive to the occurrence of nucleophilic reaction;

[0036] The reaction temperature and time for preparing the appropriate zinc reagent can increase the conversion rate of the zinc reagent, and the time is too long or the temperature is too high, which is not conducive to the stability of the zinc reagent, so the zinc reagent has a higher conversion rate in this range;

[0037] 3) Zinc reagent coupling reaction for preparing intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane: After adjusting the temperature (the addition temperature is-10℃-10℃), the catalyst (iron salt or copper salt) is slowly added in the device in 2), so as to avoid the damage to the activity of the zinc reagent during the addition of the catalyst, and after sufficient mixing, the zinc reagent occurs self-coupling reaction under the action of the catalyst, and the intermediate product is obtained after reaction at a certain temperature, and its composition is analyzed by nuclear magnetic resonance fluorine spectrum;

[0038] The catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, copper chloride and copper bromide, the water content is less than 100ppm, the addition temperature is-10℃-10℃, and the molar ratio of the anhydrous zinc halide to the catalyst iron salt or copper salt is 1:1;

[0039] The coupling reaction temperature after adding the iron salt or copper salt is 40℃-80℃, and the coupling reaction time is 4h, which is conducive to the coupling reaction of the zinc reagent to generate the intermediate product in this reaction temperature range;

[0040] The iron salt or copper salt is conducive to initiating the coupling reaction of the zinc reagent, so as to generate the intermediate product; and too high water content and temperature are not conducive to the stability of the zinc reagent, thereby affecting the subsequent coupling reaction;

[0041] 4) Preparation of target product hexafluorobutadiene by dehalogenation of the intermediate product: after the reaction system is stabilized after being reduced to normal temperature, zinc powder is added and continuously stirred, the zinc powder acts as a high-efficiency reducing agent, selectively attacks the carbon-halogen bond by virtue of its active metal characteristics, and promotes the dehalogenation reaction of the intermediate product. The target product hexafluorobutadiene is obtained by dehalogenation at a certain temperature, and its composition is analyzed by gas chromatography;

[0042] The molar ratio of the zinc powder to the intermediate product (1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane) is (2-6):1;

[0043] The dehalogenation reaction temperature is 50-80°C.

[0044] Reaction equation 1 of step 1):

[0045]

[0046] Reaction equation 2 of step 2):

[0047]

[0048] Reaction equation 3 of step 3):

[0049]

[0050] Reaction equation 4 of step 4):

[0051]

[0052] The methods and devices not described in detail in the present application are all prior art and will not be described again.

[0053] In order to further understand the present application, the following embodiments will be described in detail. The scope of the present application is not limited by the following embodiments. Example 1

[0054] A method for preparing hexafluorobutadiene, comprising the following steps in sequence:

[0055] 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: at room temperature and atmospheric pressure, trifluorochloroethylene is slowly and uniformly added to liquid bromine, and the color change of the liquid bromine is observed until the color of the liquid bromine completely fades, and a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is obtained by reaction;

[0056] 2) Preparation of zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: at -10°C, first mix zinc powder and N,N-dimethylformamide in a flask, then add the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) (the molar ratio of zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is 1), stir to fully mix the three, and then heat to 20°C for 2h to obtain the zinc reagent;

[0057] 3) Zinc reagent coupling reaction with iron or copper salt as catalyst to prepare intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane: the temperature is reduced to 0°C, the catalyst ferric chloride is slowly added in the device in 2), after fully mixing, the intermediate product is obtained after 4h reaction at 60°C;

[0058] 4) Dehalogenation of the intermediate product to prepare the target product hexafluorobutadiene: after reducing to normal temperature, 4 times equivalent of zinc powder is added, dehalogenation at 60°C to obtain the target product hexafluorobutadiene.

[0059] After detection and measurement, the yield of hexafluorobutadiene prepared in Example 1 is 64%, and other representative performance test data. The products in the above steps are analyzed by nuclear magnetic resonance fluorine spectrum and gas chromatography to obtain the following data (gas chromatography is used in steps 1) and 4); nuclear magnetic resonance fluorine spectrum is used in steps 2), 3). The yield of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in step 1) is 93%; the yield of zinc reagent in step 2) is 83%; the yield of the intermediate product prepared by coupling in step 3) is 87%; the yield of dehalogenation in step 4) is 95%; the overall yield of the prepared hexafluorobutadiene is 64%. Example 2

[0060] A method for preparing hexafluorobutadiene, comprising the following steps performed in sequence:

[0061] 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: at normal temperature and pressure, trifluorochloroethylene is slowly and uniformly added into liquid bromine, the color change of the liquid bromine is observed until the color of the liquid bromine completely fades, and a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is obtained by reaction;

[0062] 2) Preparation of zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: at 0°C, zinc powder and tetrahydrofuran are first fully mixed in a flask, then the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) is added (the molar ratio of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane to zinc powder is 0.8), the three are fully mixed by stirring, and the temperature is raised to 30°C for 2h to obtain the zinc reagent;

[0063] 3) Zinc reagent coupling reaction with iron or copper salt as catalyst to prepare intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane: the temperature is reduced to 0°C, the catalyst copper chloride is slowly added in the device in 2), after fully mixing, the intermediate product is obtained after 4h reaction at 40°C;

[0064] 4) Dehalogenation of the intermediate product to prepare the target product hexafluorobutadiene: after reducing to normal temperature, 6 times equivalent of zinc powder is added, dehalogenation is carried out at 70°C to obtain the target product hexafluorobutadiene.

[0065] After detection and measurement, the yield of hexafluorobutadiene prepared in Example 2 is 61%, and other representative performance test data. The products in the above steps are analyzed by nuclear magnetic resonance fluorine spectrum and gas chromatography to obtain the following data (gas chromatography is used in steps 1) and 4); nuclear magnetic resonance fluorine spectrum is used in steps 2), 3). The yield of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in step 1) is 93%; the yield of zinc reagent in step 2) is 87%; the yield of the intermediate product prepared by coupling in step 3) is 77%; the yield of dehalogenation in step 4) is 98%; the overall yield of the prepared hexafluorobutadiene is 61%. Example 3

[0066] A method for preparing hexafluorobutadiene, comprising the following steps performed in sequence:

[0067] 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: at normal temperature and pressure, trifluorochloroethylene is slowly and uniformly added into liquid bromine, the color change of the liquid bromine is observed until the color of the liquid bromine completely fades, and a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is obtained by reaction;

[0068] 2) Preparation of zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: at 10°C, zinc powder and 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone are fully mixed in a flask, and then the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) is added (the molar ratio of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane to zinc powder is 1.2), the three are fully mixed by stirring, and the zinc reagent is obtained after 4h reaction at 20°C;

[0069] 3) Zinc reagent coupling reaction with iron or copper salt as catalyst to prepare intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane: the temperature is reduced to 0°C, the catalyst ferric bromide is slowly added in the device in 2), after mixing well, the intermediate product is obtained after 4h reaction at 80°C;

[0070] 4) Dehalogenation of the intermediate product to prepare the target product hexafluorobutadiene: after reducing to normal temperature, 4 times equivalent of zinc powder is added, and the target product hexafluorobutadiene is obtained after dehalogenation at 80°C.

[0071] After detection and measurement, the yield of hexafluorobutadiene prepared in Example 3 is 64%, and other representative performance test data. The products in the above steps are analyzed by nuclear magnetic resonance fluorine spectrum and gas chromatography to obtain the following data (gas chromatography is used in steps 1) and 4); nuclear magnetic resonance fluorine spectrum is used in steps 2), 3). The yield of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in step 1) is 93%; the yield of zinc reagent in step 2) is 81%; the yield of the intermediate product prepared by coupling in step 3) is 87%; the yield of dehalogenation in step 4) is 97%; and the overall yield of the prepared hexafluorobutadiene is 64%.

[0072] The above examples are only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A process for the preparation of hexafluorobutadiene, characterized in that, The method comprises the following steps in sequence: 1) at normal temperature and pressure, the electrophilic addition reaction of chlorotrifluoroethylene and liquid bromine to generate 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) the zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane are mixed with an aprotic polar solvent, and under the help of the aprotic polar solvent, the zinc powder attacks the carbon-halogen bond on 1,2-dibromo-1-chloro-1,2,2-trifluoroethane to obtain a zinc reagent containing 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride; 3) the zinc reagent undergoes self-coupling reaction to generate an intermediate product containing 1,4-dibromo-2,3-dichloro-1,1,2,3,4,4-hexafluorobutane and 1,2,3,4-tetrabromo-1,1,2,3,4,4-hexafluorobutane, with an iron salt or a copper salt as a catalyst; 4) the intermediate product is dehalogenated under the action of zinc powder to generate the target product hexafluorobutadiene; In step 2), the molar ratio of the zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is 1:(0.8-1.2), and the temperature of the added zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is -10℃-20℃; In step 2), the reaction temperature for generating the zinc reagent is -20℃-30℃, and the reaction time is 2h-4h; In step 3), the catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, copper chloride and copper bromide, the water content is less than 100ppm, the temperature of the zinc reagent when added is -10℃-10℃, and the molar ratio of the zinc reagent and the catalyst is 1:1; In step 3), the coupling reaction temperature is 40℃-80℃ after the iron salt or copper salt is added, and the coupling reaction time is 4h.

2. The method for preparing hexafluorobutadiene according to claim 1, characterized in that, In step 2), the aprotic polar solvent is one or more of tetrahydrofuran, N,N-dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone and N,N-diisopropylethylamine, and the water content is less than 100ppm.

3. The method for preparing hexafluorobutadiene according to claim 1, characterized in that, In step 4), the molar ratio of the zinc powder and the intermediate product is (2-6):1, and the reaction temperature is 50℃-80℃.

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