Method for producing hexafluorobutadiene

Abstract

The present application provides a method for producing hexafluorobutadiene. The method includes the following steps: In step (1), a trifluorovinyl zinc bromide solution, a catalyst, and a first organic solvent are placed in a pressure-resistant reactor, and the reactor is purged with an inert gas. Then, bromotrifluoroethylene is added and reacted to obtain hexafluorobutadiene. Here, a polar aprotic organic solvent is used as the first organic solvent. In step (2), after the reaction is complete, the gaseous material is passed through a circulating shower system containing a second organic solvent to absorb excess bromotrifluoroethylene and fluorine-containing olefin impurities, and the unabsorbed hexafluorobutadiene crude product is purified by rectification. Here, the second organic solvent is selected from polar aprotic organic solvents and ionic liquids.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from a Chinese patent application bearing application number 202311639961.2, filed with the China Patent Office on December 1, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to fluorine-containing electronic gases, and in particular to a method for producing hexafluorobutadiene. [Background technology]

[0003] Hexafluorobutadiene (C4F6) is a colorless, liquefiable fluorine-containing gas with a boiling point of 5.5°C at atmospheric pressure and a liquid density of 1.44 g / mL at 15°C. Currently, hexafluorobutadiene is primarily used as a dry etching gas for precision etching of critical dimensions (up to 100 nm) in the production of Cu-containing low-K dielectric rectifier circuit boards. Its selectivity and depth-to-width ratio are superior to those of other etching gases. For example, compared with octafluorocyclobutane (c-C4F8), the width-to-depth ratio of C4F6 reaches 10, while that of c-C4F8 is only 3, making C4F6 suitable for ultra-narrow linewidth processes. C4F6 only etches silicon oxide films, leaving photoresist, silicon films, and nitride films unaffected, resulting in excellent etching selectivity. In addition, hexafluorobutadiene has good environmental properties, with ODP=0, GWP(100)=290, and a residence time in the atmosphere of only 1.9 days, making it a green and environmentally friendly etching gas with a very small greenhouse effect. Therefore, with the development of the integrated circuit industry and increasing attention to greenhouse gases, hexafluorobutadiene, which has the best etching effect and environmental friendliness, is sure to become a mainstream product and be widely used in the laser etching agent market.

[0004] The production and purification process of hexafluorobutadiene has been one of the hotspots of research in recent years. In the prior art, the reports on the production of hexafluorobutadiene mainly include the following:

[0005] WO2006 / 026400 describes a method for preparing bromotrifluoroethylene (CF2=CFBr) from chlorotrifluoroethylene (CF2=CFCl) as a raw material by hydrogenation, dechlorination, bromination, and removal of hydrogen bromide, followed by reaction with zinc powder to prepare trifluorovinyl zinc bromide (CF2=CFZnBr), and finally, by addition of Fe 3+ or Cu 2+ It has been disclosed that hexafluorobutadiene is obtained by homocoupling reaction in the presence of ions. Although this method uses inexpensive materials, it involves many dangerous production steps, and there is a risk of self-polymerization of the intermediate product trifluoroethylene, making it unsuitable for industrial mass production.

[0006] CN104829415 discloses a process route for producing hexafluorobutadiene using tetrafluoroethane (HFC-134a) as a raw material. First, tetrafluoroethane and bromine are reacted at high temperature to obtain 1,1-dibromotetrafluoroethane, which is then reacted with zinc powder in a polar aprotic solvent to prepare trifluorovinylzinc bromide. Finally, Fe 3+ The reaction involves homocoupling in the presence of an oxidizing agent to obtain hexafluorobutadiene, with a total reaction yield of 47%. This reaction uses the inexpensive refrigerant HFC-134a as raw material and has a relatively short process route, but due to the low activity of 1,1-dibromotetrafluoroethane and the low yield when preparing zinc powder and trifluorovinylzinc bromide, this process route results in a high actual unit consumption and generates a large amount of waste liquid, waste gas, and solid waste, making it unlikely to be put into practical industrial use.

[0007] US 304630 discloses a method for producing perfluorobutadiene using chlorotrifluoroethylene as a raw material, which involves first reacting chlorotrifluoroethylene with iodine chloride (ICl) in a closed system at 35-40°C to obtain 1,2-dichloro-1,2,2-trifluoroiodoethane, then coupling with an equivalent amount of mercury under UV light irradiation to obtain 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane, and finally dechlorinating 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane in an alcohol solvent under the action of zinc powder to obtain hexafluorobutadiene. This method requires the use of chemical equivalents of iodine chloride and mercury, and the resulting product, mercury iodide, is a highly toxic and expensive reagent.

[0008] US 2,894,043 discloses the dimerization of 1,2-dichlorodifluoroethylene (CFCl = CFCl) in the presence of fluorine gas to synthesize the intermediate product 1,2,3,4-tetrachlorohexafluorobutane, which is then dechlorinated with zinc powder to obtain the target product, perfluorobutadiene. This method requires low-temperature conditions (-70°C) during the fluorination dimerization step and also uses the highly hazardous gas F2. US 2,676,193 improves on this method, but the reaction still requires high-temperature (300°C) and high-pressure (12 MPa) conditions, and the reaction yield is somewhat low at 30-40%, with many by-products and difficulty in product separation.

[0009] WO2018235883 discloses using chlorotrifluoroethylene as a raw material to catalyze a homocoupling reaction in the presence of a palladium catalyst, a phosphorus ligand, and zinc powder to obtain hexafluorobutadiene, with a maximum yield of 86.1%. Patent CN116693365 discloses using chlorotrifluoroethylene and trifluoroethylene as raw materials to undergo a cross-coupling reaction in the presence of an activated palladium catalyst and a basic compound to obtain hexafluorobutadiene, with a maximum reaction yield of 83%. This method is simple, but uses expensive palladium as a catalyst, which is not advantageous in terms of raw material costs.

[0010] In the prior art, reports on the purification of hexafluorobutadiene mainly include the following:

[0011] US6544319 discloses a method for purifying hexafluorobutadiene using adsorption. This method is low-cost, operates under mild conditions, and can effectively adsorb azeotropic fluorine-containing olefin compounds and alcohol-based impurities. However, heat is generated when adsorbing alcohol-based impurities, and when hexafluorodiolefins are heated, rearrangement isomerization occurs, easily producing impurities such as hexafluoro-2-butyne that are difficult to remove.

[0012] CN111247120 discloses that crude hexafluorobutadiene, including octafluoro-1-butene, octafluoro-2-butene, heptafluoro-1-butene, and heptafluoro-2-butene, is subjected to extractive distillation using oxygenated hydrocarbons such as alcohols, ketones, and ethers, halogenated saturated hydrocarbons, and halogenated unsaturated hydrocarbons as extraction solvents, with a theoretical plate count of 14. The resulting hexafluorobutadiene product has a purity of 99.99%.

[0013] CN111138240 discloses a method for removing water from hexafluorobutadiene using dioctyl phthalate, ethylene glycol, N,N-dimethylformamide, and glycerin as extractants. The water content of the purified product is 10-12 ppm. However, the method only discloses that the water in the product is removed using an extractant and that the separated crude hexafluorobutadiene does not contain heptafluorobutene-based impurities, but does not disclose the purity of the hexafluorobutadiene product.

[0014] CN116903438 discloses the purification of hexafluorobutene using a technique that combines extractive rectification and adsorption. Furfural, methyl ethyl ketone, and cyclopentanone are used as extractants, and modified graphene oxide doped with organic bases and copper salts is used as the adsorbent. The maximum product purity reaches 5N or higher, but the purity of the raw materials is not specified.

[0015] In view of the shortcomings of the prior art, there is a need to provide a method for producing hexafluorobutadiene that is simple in process and low in cost. Summary of the Invention [Problem to be solved by the invention]

[0016] In order to alleviate the problems of related art such as high cost, many steps, low yield, and safety risks associated with the production of hexafluorobutadiene, the present application provides a method for producing hexafluorobutadiene, which overcomes the shortcomings of the conventional methods for producing hexafluorobutadiene. The technical route of the present invention is as follows:

[0017] [ka] [Means for solving the problem]

[0018] To achieve the object of the present invention, the present invention adopts the following technical solutions.

[0019] A method for producing hexafluorobutadiene, comprising the following steps (1) and (2): Step (1) is to place a trifluorovinyl zinc bromide solution, a catalyst, and a first organic solvent in a pressure-resistant reactor, and then purging the reactor with an inert gas. Then, bromotrifluoroethylene is added and reacted to obtain hexafluorobutadiene; the catalyst comprises a monovalent copper salt or a monovalent copper oxide and an organic phosphine ligand; Preferably, the monovalent copper salt is one or more selected from the group consisting of cuprous iodide, cuprous bromide, cuprous chloride, and cuprous acetate, and the monovalent copper oxide is cuprous oxide; the organic phosphine ligand is one or more selected from 1,10-phenanthroline, PPh3, PR1R2R3, PPhR1R2, PPh2R1, 1,2-bis(diphenylphosphino)ethane, and 2,2'-bis(diphenylphosphino)biphenyl, with the proviso that R1, R2, and R3 are each independently any one selected from an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group; preferably, the organic phosphine ligand is one selected from 1,10-phenanthroline, PPh3, 1,2-bis(diphenylphosphino)ethane, and 2,2'-bis(diphenylphosphino)biphenyl; The first organic solvent is a polar aprotic organic solvent, The first organic solvent is one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, sulfolane, and N-methylpyrrolidone, and the water content of the polar aprotic organic solvent used in the first organic solvent is ≦500 ppm.

[0020] Preferably, the organic solvent in step (1) is one selected from N,N-dimethylformamide and N,N-dimethylacetamide, and has a water content of ≦200 ppm.

[0021] In step (2), after the reaction is completed, the gaseous material is passed through a circulating shower system containing a second organic solvent to absorb excess bromotrifluoroethylene and fluorine-containing olefin impurities generated in the reaction, and the unabsorbed crude hexafluorobutadiene is purified by rectification.

[0022] The second organic solvent is selected from polar aprotic organic solvents or ionic liquids.

[0023] The polar aprotic organic solvent used as the second organic solvent is any one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, and sulfolane, and the ionic liquid is any one or more selected from 1-butyl-3-methylimidazole phosphate, 1-butyl-3-methylimidazole methanesulfonate, 1-butyl-3-methylimidazole acetate, 1-butyl-3-methylimidazole trifluoroacetate, 1-butyl-3-methylimidazole nitrate, 1-butyl-3-methylimidazole L-lactate, and 1-butyl-3-methylimidazole hexafluorophosphate.

[0024] Preferably, the second organic solvent is one selected from N,N-dimethylformamide, N,N-dimethylacetamide, 1-butyl-3-methylimidazole trifluoroacetate, 1-butyl-3-methylimidazole nitrate, and 1-butyl-3-methylimidazole hexafluorophosphate.

[0025] The molar ratio of trifluorovinyl zinc bromide to monovalent copper salt or monovalent copper oxide in the trifluorovinyl zinc bromide solution is 1:(0.01-0.3), and the molar ratio of monovalent copper salt or monovalent copper oxide to organic phosphine ligand is 1:(1.0-10).

[0026] Preferably, the molar ratio of trifluorovinyl zinc bromide to monovalent copper salt or monovalent copper oxide in the trifluorovinyl zinc bromide solution is 1:(0.01 to 0.20), and the molar ratio of monovalent copper salt or monovalent copper oxide to organic phosphine ligand is 1:(1.0 to 5.0).

[0027] More preferably, the molar ratio of trifluorovinyl zinc bromide to monovalent copper salt or monovalent copper oxide in the trifluorovinyl zinc bromide solution is 1:(0.05 to 0.10), and the molar ratio of monovalent copper salt or monovalent copper oxide to organic phosphine ligand is 1:(1.0 to 3.0).

[0028] In the step (1), the molar ratio of trifluorovinyl zinc bromide to bromotrifluoroethylene in the trifluorovinyl zinc bromide solution is 1:(1.0 to 10.0).

[0029] Preferably, in the step (1), the molar ratio of trifluorovinyl zinc bromide to bromotrifluoroethylene in the trifluorovinyl zinc bromide solution is 1:(1.0 to 5.0).

[0030] In the step (1), the reaction temperature is 60 to 140° C., the reaction pressure is 0.05 to 2.0 MPa, and the reaction time is 3 to 24 hours.

[0031] Preferably, in the step (1), the reaction temperature is 80 to 120° C., the reaction pressure is 0.3 to 1.0 MPa, and the reaction time is 6 to 12 hours.

[0032] In the step (2), the circulation shower system is a two-stage circulation shower system for absorption, and the temperature is -10 to 20°C and the pressure is 0 to 0.5 MPa.

[0033] Preferably, in the step (2), the circulation shower system is a two-stage circulation shower system for absorption, the temperature is −5 to 10° C., and the pressure is 0 to 0.2 MPa.

[0034] In the method for producing hexafluorobutadiene, in step (2), the organic solution after absorption in the circulation shower system is subjected to a distillation treatment, whereby bromotrifluoroethylene can be recovered and directly recycled for repeated use.

[0035] After treatment with the circulation shower system, the bromotrifluoroethylene content in the crude hexafluorobutadiene product is ≦0.3%, and the heptafluorobutene content is ≦0.02%, and after rectification, a hexafluorobutadiene product with a purity of ≧99.99% can be obtained. [Effects of the Invention]

[0036] The beneficial effects of the present invention are as follows:

[0037] (1) The present invention provides a method for producing hexafluorobutadiene by cross-coupling of bromotrifluoroethylene and trifluorovinylzinc bromide using inexpensive monovalent copper salts or oxides as a catalyst and organic phosphorus as a ligand. Compared with the oxidative homocoupling process, this method has the advantages of lower raw material costs and less discharge of waste liquids, waste gases, and solid waste.

[0038] (2) By passing the reaction product through a shower circulation absorption device containing a special solvent, excess bromotrifluoroethylene and heptafluorobutene, an impurity that is difficult to separate, can be dissolved in the solvent. The bromotrifluoroethylene content of the resulting crude hexafluorobutadiene is ≦0.3% and the heptafluorobutene content is ≦0.02%, which reduces the workload of subsequent product rectification and purification. Even with normal rectification, a product with a purity of ≧99.99% can be obtained.

[0039] (3) The present invention enables the repeated use of bromotrifluoroethylene through a simple distillation process, thereby improving the utilization rate of trifluoroethylene. [Brief explanation of the drawings]

[0040] [Figure 1] FIG. 1 shows an apparatus for producing hexafluorobutadiene in an embodiment of the present invention, which includes a continuous trifluorovinyl zinc bromide solution preparation apparatus for a continuous hexafluorobutadiene production method, comprising: 1, a bromotrifluoroethylene cylinder; 2, a trifluorovinyl zinc bromide solution cylinder; 3, a pressure-resistant reactor; 4, a condenser; 5, a buffer tank; 6, a first shower circulation absorption tower; 7, a second shower circulation absorption tower; and 8, a crude product tank. [Figure 2] FIG. 2 is a chromatogram of the product after rectification in Example 10. DETAILED DESCRIPTION OF THE INVENTION

[0041] First, the production system used in the present invention will be described with reference to Fig. 1. The system includes a pressure reactor 3, a condenser 4, a buffer tank 5, a first shower circulation absorber 6, a second shower circulation absorber 7, and a crude product tank 8.

[0042] Bromotrifluoroethylene cylinder 1 and trifluorovinylzinc bromide solution cylinder 2 are connected to the supply inlet of pressure-resistant reactor 3, the outlet at the top of pressure-resistant reactor 3 is connected to the supply inlet of condenser 4, the outlet of condenser 4 is connected to the supply inlet of buffer tank 5, the outlet of buffer tank 5 is connected to the supply inlet of first shower circulation absorption tower 6, the outlet of first shower circulation absorption tower 6 is connected to the supply inlet of second shower circulation absorption tower 7, the outlet of second shower circulation absorption tower 7 is connected to the supply inlet of crude product tank 8, and the outlet of crude product tank 8 is connected to a rectification system.

[0043] Below, a practical test will be carried out using the above system.

[0044] Example 1 (1) A 5 L pressure-resistant reactor equipped with a condensation reflux device and made of 316 L material was charged with 1810 g of an N,N-dimethylacetamide solution of trifluorovinylzinc bromide (mass fraction 25%, 2.0 mol), 1000 g of N,N-dimethylacetamide (water content 150 ppm), 38.2 g (0.2 mol) of cuprous iodide, and 72.2 g (0.4 mol) of 1,10-phenanthroline. The reactor was purged with high-purity nitrogen gas and evacuated until a vacuum of ≥ 0.1 MPa was reached. 644 g (4.0 mol) of bromotrifluoroethylene was added to the autoclave, stirring was started, the internal temperature of the reaction vessel was raised to 100°C, the refrigerant temperature of the condenser jacket was 20°C, and the pressure of the reaction vessel was 0.8 MPa. After reacting for 6 hours, a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene), and it was found that trifluorovinyl zinc bromide had been completely converted.

[0045] (2) 1 L of 1-butyl-3-methylimidazole hexafluorophosphate was added to a two-stage circulation shower system, each with a capacity of 1 L. The internal temperature was controlled at 4-6°C, the internal circulation pump was opened, and the flow rate was 100 mL / min. The control valve at the gas phase outlet of the pressure-resistant reactor was opened, and the reactor was heated to 130°C. The gas phase product was introduced into the two-stage circulation shower system, and the unabsorbed tail gas was collected in a cold trap absorption system using liquid nitrogen as a coolant. The results were as follows: 244.8 g of crude hexafluorobutadiene was collected in cold trap 1, with a purity of 97.82%. Converted to a weight percentage, this was 239.4 g. The theoretical yield was 324.0 g, and the yield was 73.9%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0046] (3) The 1-butyl-3-methylimidazole hexafluorophosphate solution in the two-stage circulation shower apparatus was added to a pressure vessel and distilled, and the temperature was raised to 120°C to distill off the dissolved fluorine-containing olefin, which was collected in a cold trap absorption apparatus using liquid nitrogen as a coolant, with the following results: A total of 341.9 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 89.50%, the chromatographic content of hexafluorobutadiene was 9.75%, and the contents of the other components were as shown in Table 2.

[0047] Example 2 The procedure of this example was the same as that of Example 1, with the only difference being that 19.1 g (0.1 mol) of cuprous iodide was added to a 5 L pressure-resistant reactor made of 316 L material, instead of 38.2 g (0.2 mol) of cuprous iodide, while other conditions were unchanged. The results were as follows:

[0048] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinylzinc bromide was found to be 94.5%.

[0049] In step (2), 234.2 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 96.60%, which was 226.2 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 69.8%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0050] In step (3), a total of 358.7 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 90.80%, the chromatographic content of hexafluorobutadiene was 8.55%, and the contents of other components were as shown in Table 2.

[0051] Example 3 The procedure of this example was the same as that of Example 1, with the only difference being that 38.2 g (0.2 mol) of cuprous iodide was replaced with 19.8 g (0.2 mol) of cuprous chloride in a 5 L pressure-resistant reactor made of 316 L material, with the other conditions remaining unchanged. The results were as follows:

[0052] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene), which showed that trifluorovinylzinc bromide was completely converted.

[0053] In step (2), 244.0 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 96.32%, which was 235 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 72.5%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0054] In step (3), a total of 339.3 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 89.25%, the chromatographic content of hexafluorobutadiene was 10.10%, and the contents of other components were as shown in Table 2.

[0055] Example 4 The procedure of this example was the same as that of Example 1, with the only difference being that 72.2 g (0.4 mol) of 1,10-phenanthroline was replaced with 104.9 g (0.4 mol) of triphenylphosphine in a 5 L pressure-resistant reactor made of 316 L material, while the other conditions were unchanged. The results were as follows:

[0056] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinylzinc bromide was found to be 97.9%.

[0057] In step (2), 254.0 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 95.83%, which was 243.4 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 75.1%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0058] In step (3), a total of 340.6 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 91.40%, the chromatographic content of hexafluorobutadiene was 8.29%, and the contents of other components were as shown in Table 2.

[0059] Example 5 The procedure of this example was the same as that of Example 1, with the only difference being the following: 1810 g of a solution of trifluorovinyl zinc bromide in N,N-dimethylacetamide (25% mass fraction, 2.0 mol) was replaced with 1810 g of a solution of trifluorovinyl zinc bromide in N,N-dimethylformamide (25% mass fraction, 2.0 mol) in a 5 L pressure-resistant reactor made of 316 L material, and 1000 g of N,N-dimethylacetamide (150 ppm water content) was replaced with 1000 g of N,N-dimethylformamide (150 ppm water content), with the other conditions remaining unchanged. The results were as follows:

[0060] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene), which showed that trifluorovinylzinc bromide was completely converted.

[0061] In step (2), 251.0 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 96.59%, which was 242.4 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 74.8%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0062] In step (3), a total of 338.7 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 89.85%, the chromatographic content of hexafluorobutadiene was 9.31%, and the contents of other components were as shown in Table 2.

[0063] Example 6 The procedure of this example was the same as that of Example 1, with the only difference being that the internal temperature of the reactor was increased to 80°C instead of 100°C, and the other conditions were the same. The results were as follows:

[0064] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinylzinc bromide was found to be 80.5%.

[0065] In step (2), 205.6 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 95.50%, which was 196.4 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 60.6%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0066] In step (3), a total of 391.28 g was collected in cold trap 2, with a chromatographic content of bromotrifluoroethylene of 93.31%, a chromatographic content of hexafluorobutadiene of 5.75%, and the contents of the other components as shown in Table 2.

[0067] Example 7 The procedure of this example was the same as that of Example 1, with the only difference being that in step (2), the second organic solvent, 1-butyl-3-methylimidazole hexafluorophosphate, was replaced with 1-butyl-3-methylimidazole trifluoroacetate, and the other conditions were unchanged. The results were as follows:

[0068] In step (2), 253.0 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 96.20%, which was 247.2 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 76.3%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0069] In step (3), a total of 337.85 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 89.61%, the chromatographic content of hexafluorobutadiene was 9.20%, and the contents of other components were as shown in Table 2.

[0070] Example 8 The procedure of this example was the same as that of Example 1, with the only difference being that in step (2), the internal temperature of the two-stage circulation shower device was controlled to 4-6°C, but the internal temperature was set to 2-4°C, with the other conditions remaining unchanged. The results were as follows:

[0071] In step (2), 233.8 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 97.85%, which was 228.8 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 70.6%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0072] In step (3), a total of 356.4 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 88.02%, the chromatographic content of hexafluorobutadiene was 11.46%, and the contents of other components were as shown in Table 2.

[0073] Example 9 The operation of this example was the same as that of Example 1, with the only difference being that in step (1), recovered bromotrifluoroethylene was used as the raw material, with the proviso that the purity of bromotrifluoroethylene in the recovered bromotrifluoroethylene was 93.20% and the purity of hexafluorobutadiene was 6.25%.

[0074] The amount of the feed was 691 g (when converted to weight percentage, the mass of bromotrifluoroethylene was 644 g). Other conditions were unchanged. The results were as follows:

[0075] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene), which showed that trifluorovinylzinc bromide was completely converted.

[0076] In step (2), 330.6 g of crude hexafluorobutadiene was collected in the cooling trap 1. The purity was 96.33%, which was 318.4 g when converted to weight percentage. The theoretical yield was 324.0 g, and the yield was 98.30%. The contents of each impurity in the crude hexafluorobutadiene were as shown in Table 1.

[0077] In step (3), a total of 341.9 g was collected in cold trap 2, and the chromatographic content of bromotrifluoroethylene was 88.90%, the chromatographic content of hexafluorobutadiene was 10.52%, and the contents of other components were as shown in Table 2.

[0078] [Table 1]

[0079] [Table 2]

[0080] Example 10 Rectification experiments were carried out using the crude hexafluorobutadiene products prepared in Examples 1 to 7 as raw materials, and the rectification column parameters and rectification parameters were as shown in Tables 3 and 4 below.

[0081] [Table 3]

[0082] [Table 4] In the rectification, 800 g was fed, and 57.5 g of pre-distillate was obtained, 608 g of product, and 118.5 g of bottoms. The product purity was 99.990%, the rectification yield per batch was 76.0%, and the material balance rate was 98.0%. See Figure 2 for the chromatogram of the product after rectification, and the results were as follows:

[0083] [Table 5]

[0084] (Comparative Example 1) The procedure of this example was the same as that of Example 1, with the only difference being that no monovalent copper salt catalyst was added in step (1), and other conditions were unchanged. The results were as follows:

[0085] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinylzinc bromide was found to be 0.5%.

[0086] No hexafluorobutadiene product is collected in cold trap 1 in step (2).

[0087] (Comparative Example 2) The procedure of this example was the same as that of Example 1, with the only difference being that no organic phosphine ligand was added in step (1), and other conditions were kept unchanged. The results were as follows:

[0088] After reacting for 6 hours in step (1), a sample was taken from the liquid phase tube of the autoclave and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinylzinc bromide was found to be 62.2%.

[0089] In step (2), 65.3 g of crude hexafluorobutadiene was collected in the cooling trap 1, and the purity was 95.47%, which was 62.3 g when converted to weight percentage. The theoretical yield was 162.0 g, and the yield was 38.5%.

[0090] A total of 444.4 g was collected in cold trap 2 in step (3), with a chromatographic content of bromotrifluoroethylene of 92.81% and a chromatographic content of hexafluorobutadiene of 6.55%.

[0091] (Comparative Example 3) The procedure of this example was the same as that of Example 1, with the only difference being that the product prepared in step (1) was not subjected to the treatment of step (2) but was directly collected in a cold trap absorption device using liquid nitrogen as a coolant. The results were as follows: 607.3 g of crude hexafluorobutadiene was collected in cold trap 1, with a purity of 41.7%, equivalent to 253.4 g by weight percentage, and the theoretical yield was 324.0 g, for a yield of 78.2%.

Claims

1. The method includes steps (1) and (2), In step (1), a trifluorovinyl zinc bromide solution, a catalyst, and a first organic solvent are placed in a pressure-resistant reactor, and the reactor is purged with an inert gas. Then, bromotrifluoroethylene is added and reacted to obtain hexafluorobutadiene; the catalyst comprises a monovalent copper salt or a monovalent copper oxide and an organic phosphine ligand; The organic phosphine ligand is 1,10-phenanthroline, PPh ３ , P.R. １ R ２ R ３ , PPhR １ R ２ , PPh ２ R １ , 1,2-bis(diphenylphosphino)ethane, and 2,2′-bis(diphenylphosphino)biphenyl, provided that R １ , R ２ , R ３ are each independently any one selected from an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group, The first organic solvent is a polar aprotic organic solvent, In step (2), after the reaction is completed, the gaseous material is passed through a circulating shower system containing a second organic solvent to absorb excess bromotrifluoroethylene and fluorine-containing olefin impurities generated in the reaction, and the unabsorbed hexafluorobutadiene crude product is purified by rectification; The method for producing hexafluorobutadiene, wherein the second organic solvent is selected from a polar aprotic organic solvent or an ionic liquid.

2. 2. The method for producing hexafluorobutadiene according to claim 1, wherein the monovalent copper salt is one or more selected from the group consisting of cuprous iodide, cuprous bromide, cuprous chloride, and cuprous acetate, and / or the monovalent copper oxide is cuprous oxide.

3. the first organic solvent is one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, sulfolane, and N-methylpyrrolidone, and the water content of the polar aprotic organic solvent used in the first organic solvent is ≦500 ppm; The method for producing hexafluorobutadiene according to claim 1 or 2, wherein the polar aprotic organic solvent used as the second organic solvent is any one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphoric triamide, dimethyl sulfoxide, and sulfolane, and the ionic liquid is any one or more selected from 1-butyl-3-methylimidazole phosphate, 1-butyl-3-methylimidazole methanesulfonate, 1-butyl-3-methylimidazole acetate, 1-butyl-3-methylimidazole trifluoroacetate, 1-butyl-3-methylimidazole nitrate, 1-butyl-3-methylimidazole L-lactate, and 1-butyl-3-methylimidazole hexafluorophosphate.

4. The method for producing hexafluorobutadiene according to any one of claims 1 to 3, wherein the first organic solvent described in the step (1) is one selected from N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane.

5. The method for producing hexafluorobutadiene according to any one of claims 1 to 4, characterized in that the molar ratio of trifluorovinyl zinc bromide to the monovalent copper salt or monovalent copper oxide in the trifluorovinyl zinc bromide solution is 1: (0.01 to 0.3), and the molar ratio of the monovalent copper salt or monovalent copper oxide to the organic phosphine ligand is 1: (1.0 to 10).

6. The method for producing hexafluorobutadiene according to claim 5, wherein the molar ratio of trifluorovinyl zinc bromide to the monovalent copper salt or monovalent copper oxide in the trifluorovinyl zinc bromide solution is 1:(0.01 to 0.20), preferably 1:(0.05 to 0.10), and the molar ratio of the monovalent copper salt or monovalent copper oxide to the organic phosphine ligand is 1:(1.0 to 5.0), preferably 1:(1.0 to 3.0).

7. The method for producing hexafluorobutadiene according to any one of claims 1 to 6, characterized in that the molar ratio of trifluorovinyl zinc bromide to bromotrifluoroethylene in the trifluorovinyl zinc bromide solution is 1:(1 to 10), preferably 1:(1.0 to 5.0).

8. The method for producing hexafluorobutadiene according to any one of claims 1 to 7, wherein in step (1), the reaction temperature is 60°C to 140°C, the reaction pressure is 0.05 MPa to 2.0 MPa, and the reaction time is 3 hours to 24 hours, and preferably, in step (1), the reaction temperature is 80°C to 120°C, the reaction pressure is 0.3 MPa to 1.0 MPa, and the reaction time is 6 hours to 12 hours.

9. The method for producing hexafluorobutadiene according to any one of claims 1 to 8, wherein the second organic solvent described in step (2) is one or more selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, 1-butyl-3-methylimidazole phosphate, 1-butyl-3-methylimidazole acetate, 1-butyl-3-methylimidazole trifluoroacetate, and 1-butyl-3-methylimidazole hexafluorophosphate.

10. The method for producing hexafluorobutadiene according to any one of claims 1 to 9, wherein the circulation shower system described in step (2) is a two-stage circulation shower system for absorption, and the temperature in the circulation shower system is -10°C to 20°C and the pressure is 0 MPa to 0.5 MPa, preferably the temperature in the circulation shower system is -5°C to 10°C and the pressure is 0 MPa to 0.2 MPa.

11. The method for producing hexafluorobutadiene according to any one of claims 1 to 10, characterized in that when the organic solution after absorption in the circulation shower system described in step (2) is subjected to a distillation treatment, bromotrifluoroethylene can be recovered and directly circulated for repeated use.

12. The method for producing hexafluorobutadiene according to any one of claims 1 to 11, characterized in that the hexafluorobutadiene crude product treated in the circulation shower system has a bromotrifluoroethylene content of ≦0.3% and a heptafluorobutene content of ≦0.02%, and after rectification, a hexafluorobutadiene product with a purity of ≧99.99% can be obtained.

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