Preparation method of hexafluorobutadiene

Abstract

The invention provides a preparation method of hexafluorobutadiene, which comprises the following steps: 1) carrying out electrophilic addition reaction on chlorotrifluoroethylene and liquid bromine at normal temperature and normal pressure to generate 1, 2-dibromo-1-chloro-1, 2, 2-trifluoroethane; 2) mixing zinc powder, 1, 2-dibromo-1-chloro-1, 2, 2-trifluoroethane and an aprotic polar solvent, and carrying out a reaction so as to obtain a zinc reagent containing 1-chloro-2-bromo-1, 2, 2-trifluoroethyl zinc bromide and 1, 2-dibromo-1, 2, 2-trifluoroethyl zinc chloride; 3) adding a catalyst and a zinc reagent, and carrying out 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) dehalogenating the intermediate product to generate hexafluorobutadiene; the method has the effects of simple reaction process, relatively low risk, relatively mild reaction conditions and relatively high yield.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of hexafluorobutadiene, in particular to a method for preparing hexafluorobutadiene. Background Art

[0002] With the rapid development of the domestic optoelectronic industry, especially the semiconductor industry, the demand for dry etching gas is also increasing. Hexafluorobutadiene (C4F6) is a perfluorinated compound with a boiling point of 6°C and a density of 1.4 g·mL. -1 , its application potential in the chip industry is gradually being developed. Studies have shown that compared with other commonly used etching gases, hexafluorobutadiene can perform dry etching on widths less than 100nm with higher selectivity and precision. 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 polymerization monomer to prepare polyhexafluorobutadiene, and can also be combined with other monomers to synthesize fluorine-containing rubber and resins with good electrical properties. Hexafluorobutadiene is a low greenhouse effect, green and environmentally friendly high-efficiency dry etching gas with a lifetime in the atmosphere of less than 2d and a greenhouse effect coefficient GWP. 100 Less than 300.

[0003] Currently, there are numerous routes for preparing hexafluorobutadiene, including 1,2-dichlorodifluoroethylene, tetrafluoroethylene, 1,1,1,3-tetrafluoroethane, and chlorotrifluoroethylene. GB798407 reports a synthetic route using 1,2-dichlorodifluoroethylene as a raw material. This method requires a pressure of 13.3 MPa, a temperature of 275°C, and good stirring. CA509738 reports a synthetic route using tetrafluoroethylene as a raw material. However, this raw material is flammable and explosive, and poses a carcinogenic risk. The reaction requires a hexane solution containing butyl lithium at -80°C, which is highly hazardous. CN101432253A reports a synthetic route using 1,1,1,2-tetrafluoroethane as a raw material. This method requires the use of liquid bromine, which is costly, hazardous, and involves multiple reaction steps. US Pat. No. 3,046,304A reports a synthetic route using chlorotrifluoroethylene as a raw material to produce hexafluorobutadiene via reaction with iodine chloride or iodine bromide. This method requires the use of mercury or dioxane, which is hazardous. US Pat. No. 2,668,182A reports a synthetic route using chlorotrifluoroethylene as a raw material to produce hexafluorobutadiene via thermal catalytic coupling. This method requires high temperatures, produces a high concentration of impurities in the product, and requires the addition of chlorine for reaction and subsequent separation, which is both expensive and hazardous.

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

[0005] The object of the present invention is to provide a method for preparing hexafluorobutadiene, which can achieve a simple reaction process, low risk, and prepare hexafluorobutadiene in a high yield under relatively mild conditions.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is: A method for preparing hexafluorobutadiene comprises the following steps performed in sequence: 1) At room temperature and pressure, chlorotrifluoroethylene reacts with liquid bromine to form 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) thoroughly mixing zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane with an aprotic polar solvent, and allowing the zinc powder to attack the carbon-halogen bond on the 1,2-dibromo-1-chloro-1,2,2-trifluoroethane at a certain temperature with the aid of the aprotic solvent to react and obtain a zinc reagent comprising 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride; 3) Using an iron salt or a copper salt as a catalyst, the zinc reagent undergoes a self-coupling reaction to generate an intermediate product comprising 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 dehalogenated under the action of zinc powder to generate the target product hexafluorobutadiene.

[0007] Preferably, in step 1), the normal temperature is 15° C. to 30° C., and the normal pressure is 0.100 MPa to 0.103 MPa.

[0008] 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.

[0009] 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°C to 20°C.

[0010] Preferably, in step 2), the reaction temperature for generating the zinc reagent is -20°C to 30°C, and the reaction time is 2h to 4h.

[0011] Preferably, in step 3), the catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, copper chloride, and copper bromide, and the water content is less than 100 ppm. The temperature of the zinc reagent during addition is -10°C to 10°C, and the molar ratio of the zinc reagent to the catalyst is 1:1.

[0012] Preferably, in step 3), the coupling reaction temperature after adding the iron salt or copper salt is 40° C. to 80° C., and the coupling reaction time is 4 hours.

[0013] 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°C to 80°C.

[0014] This application has achieved the following beneficial technical effects: (1). The simplicity of the reaction process of this preparation method is mainly reflected in the three aspects that the raw materials are easier to obtain (no pretreatment is required), the reaction process is relatively streamlined, and the reaction equipment is simpler. The main raw material of this preparation method is chlorotrifluoroethylene, which is easy to obtain and does not require additional pretreatment for subsequent reactions. The reaction process of this preparation method mainly includes four steps, each of which is carried out under relatively mild reaction conditions, does not require pressure operation or high temperature operation, and is simple to operate. The reaction equipment required for this preparation method is simple. Since the reaction conditions are mild during the reaction process, no pressure or high temperature operation is required, and glass equipment with good airtightness can be used.

[0015] (2) The risk of this preparation method is relatively low, which is mainly reflected in the following four aspects: low toxicity of raw materials, mild reaction process, safe operation process and stable process. The main raw material of this preparation method is trifluorochloroethylene, which has low toxicity. The reaction process of this preparation method is mild, the overall reaction temperature does not exceed 80℃, and there is no pressure during the reaction. The operation process of this preparation method is safe. Since the reaction temperature does not need to exceed 80℃ and the reaction is not under pressure, this preparation method mainly includes four steps, none of which have pressure requirements and can be carried out under normal pressure. Step 1) bromination of trifluorochloroethylene can be carried out at room temperature; Step 2) preparation of zinc reagent, adding zinc powder and the reaction process temperature is -20~30℃; Step 3) and Step 4), the temperature of the 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 of this preparation method is stable. The four steps of this preparation method have stable reaction processes. During the reaction process, a large amount of heat will not be released and the pressure will not rise sharply.

[0016] (3). The reaction conditions of this preparation method are relatively mild, mainly reflected in that the reaction conditions do not require high or low temperatures, and do not require pressure reactions. This preparation method mainly includes four steps. Step 1) The bromination of trifluorochloroethylene is an electrophilic addition reaction, which can be carried out at room temperature and pressure. Step 2) The preparation of the zinc reagent, the addition of zinc powder and the reaction process temperature are -20℃ to 30℃, there is no pressure requirement, and this step is carried out at normal pressure. Steps 3) and 4), the zinc reagent coupling reaction and the dehalogenation reaction are the steps in this preparation method that have higher temperature requirements. The reaction process temperature still does not need to exceed 80℃, there is no pressure requirement, and these steps are carried out at normal pressure.

[0017] (4) This preparation method mainly includes four steps. Thanks to the high yield of each step, the final preparation method has a high yield of the product hexafluorobutadiene (yield of 55~70%). Step 1) The bromination process of trifluorochloroethylene has high selectivity and conversion rate for the intermediate product 1,2-dibromo-1-chloro-1,2,2-trifluoroethane (yield is in the range of 90~95%). Steps 2) and 3) The preparation and coupling process of the zinc reagent do not have the high conversion rate of step 1, but through the design of the reaction system (selection of aprotic solvent and control of reaction conditions), these two steps have fewer side reactions and high selectivity, so they also have good yields (depending on different reaction conditions, the yield varies greatly, and the optimal yields of steps 2) and 3 can reach 87% and 88% respectively). Step 4) The dehalogenation process has an extremely high yield (the highest yield can be close to 99%). Combined with each step, the reasonable process connection and the complementary reaction characteristics form a set of efficient and stable synthetic pathways, which makes this preparation method have a high yield.

[0018] In the present invention, chlorotrifluoroethylene, which is currently inexpensive, is used as a raw material, the material is easily available, the reaction device is simple, the reaction process is simple, and at the same time, the reaction conditions are relatively mild and do not require a very high reaction temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a statistical graph of the mass spectrometry results of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in Example 1; Figure 2 This is a statistical chart of the mass spectrometry results of hexafluorobutadiene in Example 1. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0021] Referring to reaction equations 1, 2, 3, and 4, the present invention provides a method for preparing hexafluorobutadiene, comprising the following steps performed in sequence: 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: At room temperature and pressure, chlorotrifluoroethylene was slowly and uniformly introduced into liquid bromine. The chlorotrifluoroethylene and the liquid bromine underwent an electrophilic addition reaction. As the chlorotrifluoroethylene was continuously introduced and the reaction proceeded, the initially dark reddish-brown liquid bromine gradually became lighter. The color of the liquid bromine was continuously observed until the color of the liquid bromine completely faded. The reaction yielded a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane, the composition of which was analyzed by gas chromatography. 2) preparing a zinc reagent comprising 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: at a certain temperature (hereinafter referred to as -10°C to 20°C), first thoroughly mixing zinc powder and an aprotic polar solvent in a flask to form a suspension system, then adding the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1), stirring to thoroughly mix the three, and then the zinc powder attacks the carbon-halogen bond with the help of the aprotic polar solvent. The reaction is carried out at a certain temperature for a period of time to obtain a highly active zinc reagent, and its composition is analyzed by nuclear magnetic resonance fluorine spectroscopy; 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; 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°C to 20°C; The reaction temperature for generating the zinc reagent is -20°C to 30°C; The reaction time for generating the zinc reagent is 2 to 4 hours; Aprotic polar solvents have excellent solvent effects, making reactant molecules more easily solvated. While not providing protons, they accelerate the departure of leaving groups through van der Waals forces or hydrogen bonds, making them more conducive to nucleophilic reactions. Appropriate reaction temperature and time for the preparation of zinc reagent can increase the conversion rate of zinc reagent. Too long time or too high temperature is not conducive to the stability of zinc reagent. Therefore, within this range, zinc reagent has a higher conversion rate. 3) Using an iron salt or a copper salt as a catalyst, a zinc reagent coupling reaction is performed to prepare an intermediate product comprising 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 to a certain temperature (the addition temperature described below is -10°C to 10°C), the catalyst (iron salt or copper salt) is slowly added to the apparatus in 2) to avoid damage to the activity of the zinc reagent during the catalyst addition process. After thorough mixing, the zinc reagent undergoes a self-coupling reaction under the action of the catalyst. After reacting at a certain temperature, an intermediate product is obtained, and its composition is analyzed by nuclear magnetic resonance fluorine spectroscopy; The catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, copper chloride, and copper bromide, with a water content of less than 100 ppm, an addition temperature of -10°C to 10°C, and a molar ratio of anhydrous zinc halide to the catalyst iron salt or copper salt of 1:1; The coupling reaction temperature after adding the iron salt or copper salt is 40°C to 80°C, and the coupling reaction time is 4 hours. This reaction temperature range is conducive to the coupling reaction of the zinc reagent to generate an intermediate product; Iron or copper salts are beneficial for initiating the coupling reaction of the zinc reagent, thereby generating an intermediate product; excessively high water content and temperature are not conducive to the stability of the zinc reagent, thereby affecting the subsequent coupling reaction; 4) Dehalogenation of the intermediate product to produce the target product, hexafluorobutadiene: After the reaction system is cooled to room temperature and stabilized, zinc powder is added with continuous stirring. Zinc powder, a highly efficient reducing agent, selectively attacks the carbon-halogen bond due to its active metallic properties, promoting dehalogenation of the intermediate product. The target product, hexafluorobutadiene, is obtained by dehalogenation at a specific temperature, and its composition is analyzed by gas chromatography. 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; The dehalogenation reaction temperature is 50°C to 80°C.

[0022] Reaction equation 1 of step 1):

[0023] Reaction equation 2 of step 2):

[0024] Reaction equation 3 of step 3):

[0025] Reaction equation 4 of step 4):

[0026] The methods and devices not fully described in the present invention are all prior art and will not be described in detail.

[0027] In order to further understand the present invention, the preparation method of hexafluorobutadiene provided by the present invention is described in detail below with reference to examples. The protection scope of the present invention is not limited by the following examples. Example 1

[0028] A method for preparing hexafluorobutadiene comprises the following steps performed in sequence: 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: At room temperature and pressure, chlorotrifluoroethylene is slowly added to liquid bromine at a uniform rate, and the color change of the liquid bromine is observed until the color of the liquid bromine completely fades, thereby obtaining a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) preparing a zinc reagent comprising 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: first, thoroughly mixing zinc powder and N,N-dimethylformamide in a flask at -10°C, then adding the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) (wherein the molar ratio of zinc powder to 1,2-dibromo-1-chloro-1,2,2-trifluoroethane is 1), stirring to thoroughly mix the three, and heating to 20°C to react for 2 hours to obtain the zinc reagent; 3) Using an iron salt or a copper salt as a catalyst, a zinc reagent coupling reaction is performed to prepare an intermediate product comprising 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 lowered to 0°C, and in the apparatus in 2), the catalyst ferric chloride is slowly added, the mixture is thoroughly mixed, and the reaction is carried out at 60°C for 4 hours to obtain the intermediate product; 4) Dehalogenation of the intermediate product to prepare the target product hexafluorobutadiene: After cooling to room temperature, 4 equivalents of zinc powder were added and dehalogenation reaction was carried out at 60°C to obtain the target product hexafluorobutadiene.

[0029] Testing and measurement revealed a 64% yield of hexafluorobutadiene produced in Example 1, along with other representative performance test data. The products from the above steps were analyzed by nuclear magnetic resonance fluorine spectroscopy and gas chromatography, yielding the following data (gas chromatography for steps 1) and 4); nuclear magnetic resonance fluorine spectroscopy for steps 2) and 3). The yield of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in step 1) was 93%; the yield of the zinc reagent in step 2) was 83%; the yield of the intermediate product prepared by coupling in step 3) was 87%; and the yield of the dehalogenation in step 4) was 95%. The overall yield of hexafluorobutadiene produced was 64%. Example 2

[0030] A method for preparing hexafluorobutadiene comprises the following steps performed in sequence: 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: At room temperature and pressure, chlorotrifluoroethylene is slowly added to liquid bromine at a uniform rate, and the color change of the liquid bromine is observed until the color of the liquid bromine completely fades, thereby obtaining a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) preparing a zinc reagent comprising 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: at 0° C., thoroughly mixing zinc powder and tetrahydrofuran in a flask, then adding the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) (wherein the molar ratio of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane to zinc powder is 0.8), stirring to thoroughly mix the three, and heating to 30° C. for reaction for 2 h to obtain the zinc reagent; 3) Using an iron salt or a copper salt as a catalyst, a zinc reagent coupling reaction is performed to prepare an intermediate product comprising 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 lowered to 0°C, and in the apparatus in 2), a catalyst, copper chloride, is slowly added, the mixture is thoroughly mixed, and the reaction is carried out at 40°C for 4 hours to obtain the intermediate product; 4) Dehalogenation of the intermediate product to prepare the target product hexafluorobutadiene: After cooling to room temperature, 6 equivalents of zinc powder were added and dehalogenation reaction was carried out at 70°C to obtain the target product hexafluorobutadiene.

[0031] Testing and measurement revealed a 61% yield of hexafluorobutadiene produced in Example 2, along with other representative performance test data. The products from the above steps were analyzed by nuclear magnetic resonance fluorine spectroscopy and gas chromatography, yielding the following data (gas chromatography for steps 1) and 4); nuclear magnetic resonance fluorine spectroscopy for steps 2 and 3). The yield of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in step 1 was 93%; the yield of the zinc reagent in step 2 was 87%; the yield of the intermediate product prepared by coupling in step 3 was 77%; and the yield of dehalogenation in step 4 was 98%. The overall yield of hexafluorobutadiene produced was 61%. Example 3

[0032] A method for preparing hexafluorobutadiene comprises the following steps performed in sequence: 1) Preparation of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane: At room temperature and pressure, chlorotrifluoroethylene is slowly added to liquid bromine at a uniform rate, and the color change of the liquid bromine is observed until the color of the liquid bromine completely fades, thereby obtaining a solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) preparing a zinc reagent comprising 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride: first, at 10° C., thoroughly mixing zinc powder and 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone in a flask, then adding the solution containing 1,2-dibromo-1-chloro-1,2,2-trifluoroethane prepared in 1) (wherein the molar ratio of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane to zinc powder is 1.2), stirring to thoroughly mix the three, and heating to 20° C. to react for 4 hours to obtain the zinc reagent; 3) Using an iron salt or a copper salt as a catalyst, a zinc reagent coupling reaction is performed to prepare an intermediate product comprising 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 lowered to 0°C, and the catalyst ferric bromide is slowly added to the apparatus in 2), and after thorough mixing, the reaction is carried out at 80°C for 4 hours to obtain the intermediate product; 4) Dehalogenation of the intermediate product to prepare the target product hexafluorobutadiene: After cooling to room temperature, 4 equivalents of zinc powder were added and dehalogenation reaction was carried out at 80°C to obtain the target product hexafluorobutadiene.

[0033] Testing and measurement revealed a 64% yield of hexafluorobutadiene produced in Example 3, along with other representative performance test data. The products from the above steps were analyzed by nuclear magnetic resonance fluorine spectroscopy and gas chromatography, yielding the following data (gas chromatography for steps 1) and 4); nuclear magnetic resonance fluorine spectroscopy for steps 2) and 3). The yield of 1,2-dibromo-1-chloro-1,2,2-trifluoroethane in step 1) was 93%; the yield of the zinc reagent in step 2) was 81%; the yield of the intermediate product prepared by coupling in step 3) was 87%; and the yield of the dehalogenation in step 4) was 97%. The overall yield of hexafluorobutadiene produced was 64%.

[0034] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing hexafluorobutadiene, characterized in that: The method includes the following steps: 1) At room temperature and pressure, chlorotrifluoroethylene reacts with liquid bromine to form 1,2-dibromo-1-chloro-1,2,2-trifluoroethane; 2) thoroughly mixing zinc powder and 1,2-dibromo-1-chloro-1,2,2-trifluoroethane with an aprotic polar solvent, and allowing the zinc powder to attack the carbon-halogen bond on the 1,2-dibromo-1-chloro-1,2,2-trifluoroethane at a certain temperature with the aid of the aprotic solvent to react and obtain a zinc reagent comprising 1-chloro-2-bromo-1,2,2-trifluoroethane zinc bromide and 1,2-dibromo-1,2,2-trifluoroethane zinc chloride; 3) Using an iron salt or a copper salt as a catalyst, the zinc reagent undergoes a self-coupling reaction to generate an intermediate product comprising 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 dehalogenated under the action of zinc powder to generate the target product hexafluorobutadiene.

2. The method for preparing hexafluorobutadiene according to claim 1, wherein: In step 1), the normal temperature is 15° C. to 30° C., and the normal pressure is 0.100 MPa to 0.103 MPa.

3. The method for preparing hexafluorobutadiene according to claim 1, wherein: 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.

4. The method for preparing hexafluorobutadiene according to claim 1, wherein: 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°C to 20°C.

5. The method for preparing hexafluorobutadiene according to claim 1, wherein: In step 2), the reaction temperature for generating the zinc reagent is -20°C to 30°C, and the reaction time is 2h to 4h.

6. The method for preparing hexafluorobutadiene according to claim 1, wherein: In step 3), the catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, copper chloride, and copper bromide, and the water content is less than 100 ppm. The temperature of the zinc reagent when added is -10°C to 10°C, and the molar ratio of the zinc reagent to the catalyst is 1:

1.

7. The method for preparing hexafluorobutadiene according to claim 1, wherein: In step 3), after adding the iron salt or copper salt, the coupling reaction temperature is 40° C. to 80° C., and the coupling reaction time is 4 hours.

8. The method for preparing hexafluorobutadiene according to claim 1, wherein: In step 4), the molar ratio of the zinc powder to the intermediate product is (2-6):1, and the reaction temperature is 50°C to 80°C.

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