Preparation method of hexafluorobutadiene

Abstract

The invention is suitable for the technical field of halogenated hydrocarbon preparation, and provides a preparation method of hexafluorobutadiene, which comprises the following steps: (1) fully dissolving anhydrous zinc halide and trifluoroethylene in an aprotic polar solvent; (2) dropwise adding strong alkali into an aprotic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved to obtain a trifluoroethylene-based zinc reagent; and (3) carrying out a coupling reaction by taking ferric salt or copper salt as a catalyst and a trifluorovinyl zinc reagent to generate the target product hexafluorobutadiene. Therefore, the method provided by the invention has the advantages of simple reaction process and low risk, and can prepare high-yield hexafluorobutadiene under relatively mild conditions.

Description

Technical Field

[0001] The invention relates to the technical field of preparing halogenated hydrocarbons, and 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.

[0003] 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, it can perform dry etching on widths less than 100 nm with higher selectivity and precision. Hexafluorobutadiene has a high application value in the synthesis of fluorinated fine chemicals such as fluorinated pharmaceutical intermediates. In the synthesis of fluorinated polymers, hexafluorobutadiene can be used as a polymerization monomer to prepare polyhexafluorobutadiene, and can also be combined with other monomers to synthesize fluorinated rubber and resins with good electrical properties. Hexafluorobutadiene is a high-efficiency dry etching gas with low greenhouse effect and green environmental protection. The lifetime in the atmosphere is less than 2 days, and the greenhouse effect coefficient GWP 100 Less than 300.

[0004] Currently, there are many routes for preparing hexafluorobutadiene, such as the 1,2-dichlorodifluoroethylene route, the tetrafluoroethylene route, the 1,1,1,3-tetrafluoroethane route and the chlorotrifluoroethylene route.

[0005] GB798407 reports a synthesis route using 1,2-dichlorodifluoroethylene as raw material. This method needs to be carried out under a pressure of 13.3 MPa, a temperature of 275 °C and good stirring.

[0006] CA509738 reported a synthesis route using tetrafluoroethylene as raw material. The raw materials in this method are flammable and explosive and have a carcinogenic risk. The reaction needs to be carried out at -80°C with a hexane solution containing butyl lithium, which is highly dangerous.

[0007] CN101432253A reports a synthesis route using 1,1,1,2-tetrafluoroethane as a raw material. This method requires the use of liquid bromine during the reaction, which is expensive, has certain risks, and has many reaction steps.

[0008] US3046304A reports a synthesis route using chlorotrifluoroethylene as a raw material to prepare hexafluorobutadiene by synthesizing it with iodine chloride or iodine bromide. This method requires the use of mercury or dioxane, which is dangerous.

[0009] US2668182A reports a synthetic route using chlorotrifluoroethylene as a raw material to prepare hexafluorobutadiene by thermal catalytic coupling. However, this method requires high temperatures and contains many impurities in the product. Chlorine is added for reaction and then separated, which is expensive and dangerous.

[0010] Therefore, it is necessary to develop a method for preparing hexafluorobutadiene, which has a simple reaction process, low risk, relatively mild reaction conditions and high yield. In summary, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the invention

[0011] In view of the above-mentioned defects, 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 with a high yield under relatively mild conditions.

[0012] In order to achieve the above object, the present invention provides a method for preparing hexafluorobutadiene, comprising the following steps: Step 1: fully dissolving anhydrous zinc halide and trifluoroethylene in a non-protonic polar solvent to obtain a non-protonic polar solution of anhydrous zinc halide and trifluoroethylene; the non-protonic polar solvent has an excellent solvent effect, making it easier for the reactant molecules to be solvated; while not providing protons, it combines with the leaving group through van der Waals force or hydrogen bond to accelerate the leaving group, which is more conducive to the occurrence of nucleophilic reaction.

[0013] Step 2: slowly drop a strong base into a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are dissolved, and react at a certain temperature to obtain a trifluorovinyl zinc reagent. The strong base is dropped to remove hydrogen from trifluoroethylene and then react with anhydrous zinc halide to generate a trifluorovinyl zinc reagent.

[0014]

[0015] Step 3: Using iron salt or copper salt as a catalyst, trifluorovinyl zinc reagent undergoes coupling reaction to generate the target product hexafluorobutadiene. Iron salt or copper salt is conducive to initiating the coupling reaction of zinc reagent to generate the target product hexafluorobutadiene; excessively high water content and temperature are not conducive to the stability of zinc reagent, thereby affecting the subsequent coupling reaction.

[0016]

[0017] According to a method for preparing hexafluorobutadiene of the present invention, in the step 1, the aprotic polar solvent is one or more combinations of tetrahydrofuran, N,N-dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidone, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N,N-diisopropylethylamine, benzene, toluene, 1-propanol, 2-propanol, n-butanol, and tri-n-butylamine, and the water content is less than 100 ppm.

[0018] According to a method for preparing hexafluorobutadiene of the present invention, in the step 1, the anhydrous zinc halide is zinc chloride, zinc bromide and zinc iodide, and preferably has a water content of less than 100 ppm.

[0019] According to a method for preparing hexafluorobutadiene of the present invention, in the step 1, the molar ratio of the anhydrous zinc halide to trifluoroethylene is 1:0.8 to 1:1.2, and the temperature for adding the anhydrous zinc halide and trifluoroethylene is -10°C to 20°C.

[0020] According to a method for preparing hexafluorobutadiene of the present invention, in step 2, the strong base is one or more combinations of n-butyl lithium, lithium diisopropylamide and potassium tert-butoxide.

[0021] According to a method for preparing hexafluorobutadiene of the present invention, in the step 2, the molar ratio of the strong base to trifluoroethylene is 1.0:1-1.5:1, and a slightly excessive amount of the strong base is conducive to the full progress of the reaction; the temperature of the aprotic polar solution in which the strong base is added to dissolve anhydrous zinc halide and trifluoroethylene is -20°C-30°C.

[0022] According to a method for preparing hexafluorobutadiene of the present invention, in the step 2, the strong base is added to the non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are dissolved, and the preparation temperature of the zinc reagent is -20°C to 30°C. Different strong bases have different reaction activities for the dehydrogenation of trifluoroethylene at different temperatures, and a suitable temperature needs to be selected according to the type of the strong base. The suitable temperature of the above strong bases is within this temperature range.

[0023] According to a method for preparing hexafluorobutadiene of the present invention, in the step 2, the strong base is added to the non-protonic polar solution for dissolving anhydrous zinc halide and trifluoroethylene, and the temperature time for preparing the zinc reagent is 2 to 4 hours. Prolonging the reaction time of the zinc reagent preparation appropriately can increase the conversion rate of the zinc reagent. Too long a time is not conducive to the stability of the zinc reagent, so the zinc reagent has a higher conversion rate within this range.

[0024] According to a method for preparing hexafluorobutadiene of the present invention, in the step 3, the catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, cupric chloride, and cupric bromide, the water content is less than 100 ppm, the addition temperature is -10°C to 10°C, and the molar ratio of anhydrous zinc halide to catalyst is 1:1.

[0025] According to a method for preparing hexafluorobutadiene of the present invention, in step 3, the coupling reaction temperature is 40° C. to 80° C. This reaction temperature range is conducive to the coupling reaction of the zinc reagent to generate the target product hexafluorobutadiene.

[0026] The object of the present invention is to provide a method for preparing hexafluorobutadiene, comprising the following steps: (1) fully dissolving anhydrous zinc halide and trifluoroethylene in a non-protonic polar solvent; (2) dropping a strong base into the non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved to obtain a trifluoroethylene zinc reagent; (3) using an iron salt or a copper salt as a catalyst, the trifluoroethylene zinc reagent undergoes a coupling reaction to generate the target product hexafluorobutadiene. In the present invention, trifluoroethylene, which is currently inexpensive, is used as a raw material, the material is easily available, the reaction process is simple, and the target product can be generated in one device. At the same time, the reaction conditions are relatively mild and do not require a very high reaction temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the reaction flow chart of step 2 of the present invention; Figure 2 It is the reaction flow chart of step three of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] See also Figure 1 and Figure 2 The present invention provides a method for preparing hexafluorobutadiene, comprising the following steps: Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc halide in a non-protonic polar solvent at a certain temperature and under anhydrous conditions, and then slowly introducing trifluoroethylene at the same temperature to obtain a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved; The aprotic polar solvent is one or more of tetrahydrofuran, N,N-dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidone, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N,N-diisopropylethylamine, benzene, toluene, 1-propanol, 2-propanol, n-butanol, and tri-n-butylamine, and preferably has a water content of less than 100 ppm. The aprotic polar solvent has an excellent solvent effect, making the reactant molecules more easily solvated; while not providing protons, it accelerates the leaving group by combining with the leaving group through van der Waals force or hydrogen bond, which is more conducive to the occurrence of nucleophilic reaction.

[0030] The anhydrous zinc halide is zinc chloride, zinc bromide and zinc iodide, and preferably has a water content of less than 100 ppm; an increase in water content is not conducive to the formation and stability of the trifluorovinyl zinc reagent in step 2.

[0031] The molar ratio of the anhydrous zinc halide to trifluoroethylene is 1:0.8-1:1.2; when the anhydrous zinc halide and trifluoroethylene are within this ratio range, it is beneficial to the subsequent synthesis of trifluoroethylene zinc reagent.

[0032] The temperature for adding anhydrous zinc halide and trifluoroethylene is -10° C. to 20° C. Adding anhydrous zinc halide and trifluoroethylene within this temperature range is conducive to their full dissolution in the aprotic solvent.

[0033] Step 2, preparing trifluorovinyl zinc reagent: at a certain temperature, adding a strong base to a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved, so that trifluoroethylene removes hydrogen and reacts with anhydrous zinc halide to form trifluorovinyl zinc reagent. After the addition is completed, react at a certain temperature to prepare trifluorovinyl zinc reagent.

[0034] The strong base is one or more combinations of n-butyl lithium, lithium diisopropylamide and potassium tert-butoxide; The molar ratio of the added strong base to trifluoroethylene is 1.0:1-1.5:1; a slightly excess amount of the strong base is conducive to the full progress of the reaction.

[0035] The temperature for adding the strong base is -20°C to 30°C; different strong bases have different reaction activities for the dehydrogenation of trifluoroethylene at different temperatures, and it is necessary to select a suitable temperature according to the type of the strong base. The suitable temperature of the above strong bases is within this temperature range.

[0036] After the strong base is added, the preparation temperature of the zinc reagent is -20°C to 30°C.

[0037] The preparation time of the zinc reagent after the strong base is added is 2 to 4 hours. Prolonging the reaction time of the zinc reagent preparation appropriately can increase the conversion rate of the zinc reagent. Too long a time is not conducive to the stability of the zinc reagent. Therefore, the zinc reagent has a higher conversion rate within this range.

[0038] Step 3, preparing hexafluorobutadiene: under certain temperature conditions, slowly adding iron salt or copper salt, heating to a certain temperature and reacting for a period of time to couple the trifluorovinyl zinc reagent to prepare hexafluorobutadiene; The catalyst iron salt or copper salt is one or more of ferric chloride, ferric bromide, copper chloride, and copper bromide, preferably 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 of 1:1; the iron salt or copper salt is conducive to initiating a coupling reaction of the zinc reagent to generate the target product hexafluorobutadiene, and too high a water content and temperature are not conducive to the stability of the zinc reagent, thereby affecting the subsequent coupling reaction.

[0039] The temperature of the coupling reaction of adding the iron salt or copper salt is 40° C. to 80° C. In this reaction temperature range, it is favorable for the zinc reagent to undergo a coupling reaction to generate the target product hexafluorobutadiene. Example 1

[0040] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at -30°C under anhydrous conditions, and then slowly introducing trifluoroethylene at -10°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:0.8, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at -20°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, the molar ratio of the strong base added to trifluoroethylene being 1:1, after the dropwise addition is completed, react at -20°C to prepare trifluoroethylene zinc reagent, and the preparation time of the zinc reagent after the strong base is added is 2 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at -10°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 40°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 2

[0041] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at -5°C under anhydrous conditions, and then slowly introducing trifluoroethylene at -5°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at -10°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, the molar ratio of the strong base added to trifluoroethylene being 1.2:1, after the dropwise addition is completed, react at 10°C to prepare trifluoroethylene zinc reagent, and the preparation time of the zinc reagent after the strong base is added is 2h; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at -5°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 50°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 3

[0042] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 0°C and under anhydrous conditions, and then slowly introducing trifluoroethylene at 0°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1.2, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 0°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the added strong base to trifluoroethylene is 1.5:1. After the dropwise addition is completed, react at 0°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the addition of the strong base is 2 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 0°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 60°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 4

[0043] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 5°C under anhydrous conditions, and then slowly introducing trifluoroethylene at 5°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 10°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the added strong base to trifluoroethylene is 1.2:1. After the dropwise addition is completed, react at 10°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the addition of the strong base is 3 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 5°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 70°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 5

[0044] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 10° C. under anhydrous conditions, and then slowly introducing trifluoroethylene at 10° C., wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 20°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the strong base to trifluoroethylene is 1.2:1. After the dropwise addition is completed, react at 20°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the strong base is added is 4 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 10°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 80°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 6

[0045] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 15° C. under anhydrous conditions, and then slowly introducing trifluoroethylene at 15° C., wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 20°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the strong base to trifluoroethylene is 1.2:1. After the dropwise addition is completed, react at 20°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the strong base is added is 4 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 10°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 80°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 7

[0046] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 20° C. under anhydrous conditions, and then slowly introducing trifluoroethylene at 20° C., wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 20°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the strong base to trifluoroethylene is 1.2:1. After the dropwise addition is completed, react at 20°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the strong base is added is 4 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 10°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 80°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 8

[0047] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 0°C and under anhydrous conditions, and then slowly introducing trifluoroethylene at 0°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1.2, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 0°C, drop strong base n-butyl lithium into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the added strong base to trifluoroethylene is 1.5:1. After the dropwise addition is completed, react at 0°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the addition of the strong base is 4 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 0°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 60°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 9

[0048] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 0°C and under anhydrous conditions, and then slowly introducing trifluoroethylene at 0°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1.2, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 0°C, drop a strong base lithium diisopropylamide into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, and the molar ratio of the added strong base to trifluoroethylene is 1.5:1. After the dropwise addition is completed, react at 0°C to prepare trifluoroethylene zinc reagent. The preparation time of the zinc reagent after the addition of the strong base is 4 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 0°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 60°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene. Example 10

[0049] Step 1, preparing a non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are fully dissolved: dissolving anhydrous zinc chloride in tetrahydrofuran at 0°C and under anhydrous conditions, and then slowly introducing trifluoroethylene at 0°C, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene is 1:1.2, to obtain a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved; Step 2, preparing trifluoroethylene zinc reagent: at 0°C, drop strong base potassium tert-butoxide into a non-protonic polar solution in which anhydrous zinc chloride and trifluoroethylene are fully dissolved, the molar ratio of the strong base to trifluoroethylene being 1.5:1, after the dropwise addition is completed, react at 0°C to prepare trifluoroethylene zinc reagent, and the preparation time of the zinc reagent after the strong base is added is 4 hours; Step 3, preparation of hexafluorobutadiene: slowly add ferric chloride at 0°C, the molar ratio of anhydrous zinc chloride to ferric chloride is 1:1, and heat to 60°C to react so that the trifluoroethylene zinc reagent couples to prepare hexafluorobutadiene.

[0050] Comparative Example 1 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the reaction temperature in step 1 was changed to -20°C.

[0051] Comparative Example 2 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the reaction temperature in step 1 was changed to 30°C.

[0052] Comparative Example 3 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the molar ratio of anhydrous zinc chloride to trifluoroethylene in step 1 was changed to 1:1.2.

[0053] Comparative Example 4 The raw materials, additives and reaction conditions were the same as those in Example 2, wherein the molar ratio of anhydrous zinc chloride to trifluoroethylene in step 1 was changed to 1:1.5.

[0054] Comparative Example 5 The raw materials, additives and reaction conditions are the same as those in Example 2, wherein the molar ratio of the strong base added to trifluoroethylene in step 2 is changed to 2:1.

[0055] Comparative Example 6 The raw materials, additives and reaction conditions are the same as those in Example 2, wherein the molar ratio of the strong base added to trifluoroethylene in step 2 is changed to 1:2.

[0056] Comparative Example 7 The raw materials, additives and reaction conditions are the same as those in Example 2, wherein the preparation temperature of the zinc reagent is changed to -30°C after the strong base is added in step 2.

[0057] Comparative Example 8 The raw materials, additives and reaction conditions are the same as those in Example 2, wherein the preparation temperature of the zinc reagent is changed to 50° C. after the strong base is added in step 2.

[0058] Comparative Example 9 The raw materials, additives and reaction conditions are the same as those in Example 2, wherein the preparation time of the zinc reagent after the addition of the strong base in step 2 is 1 hour.

[0059] Comparative Example 10 The raw materials, additives and reaction conditions are the same as those in Example 2, wherein the preparation time of the zinc reagent after the addition of the strong base in step 2 is 5 hours.

[0060] Comparative Example 11 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the temperature for adding ferric chloride in step 3 was changed to -20°C.

[0061] Comparative Example 12 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the temperature for adding ferric chloride in step 3 was changed to 20°C.

[0062] Comparative Example 13 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the coupling reaction temperature in step 3 was changed to 10°C.

[0063] Comparative Example 14 The raw materials, additives and reaction conditions were the same as those in Example 2, except that the coupling reaction temperature in step 3 was changed to 120°C.

[0064] The products in the above examples and comparative examples were analyzed by nuclear magnetic resonance fluorine spectrum analysis and gas chromatography to obtain the following data.

[0065] Table 1: Comparison of test data of examples and comparative examples

[0066] In summary, the present invention uses the combined action of an aprotic solvent and a strong base to prepare the intermediate product trifluoroethylene zinc reagent from the raw material trifluoroethylene, and then uses a catalyst to efficiently prepare the target product hexafluorobutadiene. The beneficial effects of the present invention are: the material is easy to obtain, the reaction process is simple, the target product can be generated by reaction in one device, and at the same time, the reaction conditions are relatively mild and do not require a very high reaction temperature.

[0067] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing hexafluorobutadiene, characterized in that: The following steps are involved: Step 1, fully dissolving anhydrous zinc halide and trifluoroethylene in a non-protonic polar solvent to obtain a non-protonic polar solution of anhydrous zinc halide and trifluoroethylene; Step 2: slowly drop a strong base into a non-protonic polar solution containing anhydrous zinc halide and trifluoroethylene, and react at a certain temperature to obtain a trifluoroethylene zinc reagent; Step 3: Using iron salt or copper salt as catalyst, trifluoroethylene zinc reagent undergoes coupling reaction to generate target product hexafluorobutadiene.

2. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 1, the aprotic polar solvent is one or more combinations of tetrahydrofuran, N,N-dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidone, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N,N-diisopropylethylamine, benzene, toluene, 1-propanol, 2-propanol, n-butanol, and tri-n-butylamine, and the water content is less than 100 ppm.

3. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 1, the anhydrous zinc halide is zinc chloride, zinc bromide and zinc iodide, and the water content is less than 100 ppm.

4. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 1, the molar ratio of the anhydrous zinc halide to trifluoroethylene is 1:0.8 to 1:1.2, and the temperature for adding the anhydrous zinc halide and trifluoroethylene is -10°C to 20°C.

5. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 2, the strong base is one or more combinations of n-butyl lithium, lithium diisopropylamide and potassium tert-butoxide.

6. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 2, the molar ratio of the strong base to trifluoroethylene is 1:1 to 1.5:1, and the temperature of the aprotic polar solution in which the strong base is added to dissolve anhydrous zinc halide and trifluoroethylene is -20°C to 30°C.

7. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 2, the temperature for preparing the zinc reagent is -20°C to 30°C after the strong base is added into the non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are dissolved.

8. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 2, the strong base is added to the non-protonic polar solution in which anhydrous zinc halide and trifluoroethylene are dissolved, and the temperature and time for preparing the zinc reagent are 2 to 4 hours.

9. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step 3, the catalyst is one or more of ferric chloride, ferric bromide, cupric chloride, and cupric bromide, the water content is less than 100 ppm, the addition temperature is -10°C to 10°C, and the molar ratio of anhydrous zinc halide to the catalyst is 1:

1.

10. The method for preparing hexafluorobutadiene according to claim 1, characterized in that: In the step three, the coupling reaction temperature is between 40°C and 80°C.

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