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 the priority of Chinese Patent Application No. 202311639961.2, filed with the Chinese Patent Office on December 1, 2023, and incorporates the entire contents of the said application by reference into this application.

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

Background Art

[0003] Hexafluorobutadiene (C4F6) is a colorless and liquefiable fluorine-containing gas, with a boiling point of 5.5 °C under normal pressure and a liquid density of 1.44 g / mL at 15 °C. Currently, hexafluorobutadiene is mainly used as a dry etching gas for the precise etching of critical dimensions (the accuracy has reached 100 nm) in the production of low-k dielectric constant integrated circuit substrates containing Cu, and has better selectivity and depth-to-width ratio than other etching gases. For example, compared with octafluorocyclobutane (c-C4F8), the width-to-depth ratio of etching with C4F6 reaches 10, while that of c-C4F8 is only 3, so C4F6 is suitable for extremely narrow linewidth processes. C4F6 only etches silicon oxide films and does not affect photoresists, silicon films and nitride films, so it has excellent etching selectivity. In addition, hexafluorobutadiene has good environmental characteristics, with ODP = 0, GWP(100) = 290, and an atmospheric residence time of only 1.9 days, so it has an extremely small greenhouse effect and is a green and environmentally friendly etching gas. Therefore, as the development of the integrated circuit industry and the attention to greenhouse gases increase, hexafluorobutadiene with the best etching effect and environmental consideration will become the mainstream product and will surely be widely used in the laser etchant market.

[0004] The production and purification processes of hexafluorobutadiene have been a hot spot in research in recent years, but the reports on the production of hexafluorobutadiene using conventional technology mainly consist of the following:

[0005] WO2006 / 026400 describes preparing bromotrifluoroethylene (CF2=CFBr) using chlorotrifluoroethylene (CF2=CFCl) as a raw material by hydrogenation, dechlorination, bromination, and removal of hydrogen bromide. Next, it is reacted with zinc powder to prepare trifluorovinyl zinc bromide (CF2=CFZnBr), and finally, Fe 3+ or Cu 2+ It has been disclosed that hexafluorobutadiene can be obtained by homocoupling in the presence of ions. Although this method uses inexpensive materials, it involves many dangerous production processes, has many steps, and carries the risk of autopolymerization of the intermediate product trifluoroethylene, making it unsuitable for large-scale industrial 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, then zinc powder is reacted in a polar aprotic solvent to prepare trifluorovinyl zinc bromide, and finally Fe 3+ The reaction yields hexafluorobutadiene by homocoupling in the presence of an oxidizing agent, with a total yield of 47%. Although this reaction uses the inexpensive refrigerant HFC-134a as a raw material and has a relatively short process pathway, 1,1-dibromotetrafluoroethane has low reactivity, and the yield is low when preparing zinc powder and trifluorovinyl zinc bromide. Therefore, this process pathway has a high actual unit consumption and generates a large amount of waste liquid, waste gas, and solid waste, making its practical industrialization prospects slim.

[0007] US304630 discloses a method for producing perfluorobutadiene from chlorotrifluoroethylene as a raw material. First, chlorotrifluoroethylene is reacted with iodine chloride (ICl) in a closed system at 35-40°C to obtain 1,2-dichloro-1,2,2-trifluoroiodoethane. Next, under UV light irradiation, it is coupled with an equivalent amount of mercury to obtain 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane. Finally, under the action of zinc powder, 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane is dechlorinated in an alcohol solvent to obtain hexafluorobutadiene. This method requires the use of stoichiometric amounts of iodine chloride and mercury, and one of the products, mercury iodide, is highly toxic and uses expensive reagents.

[0008] US2894043 discloses a method in which 1,2-dichlorodifluoroethylene (CFCl=CFCl) dimerizes 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) for the fluorination dimerization step and also uses the very dangerous gas F2. US2676193 improves upon this method, but the reaction still requires high temperature (300°C) and high pressure (12 MPa), and the reaction yield is somewhat too low at 30-40%, with many by-products and difficulty in separating the product.

[0009] WO2018235883 discloses a method for obtaining hexafluorobutadiene by catalyzing a homocoupling reaction using chlorotrifluoroethylene as a starting material in the presence of a palladium catalyst, a phosphorus ligand, and zinc powder, with a maximum yield of 86.1%. Patent CN116693365 discloses a method for obtaining hexafluorobutadiene by cross-coupling reaction using chlorotrifluoroethylene and trifluoroethylene as starting materials in the presence of an activated palladium catalyst and a basic compound, with a maximum reaction yield of 83%. Although these methods are simple processes, they are not advantageous in terms of raw material costs because they use expensive palladium as a catalyst.

[0010] The following are some of the reports on the purification of hexafluorobutadiene using conventional technology.

[0011] US6544319 discloses a method for purifying hexafluorobutadiene using adsorption. This method is low-cost, requires mild conditions, and can effectively adsorb azeotropic fluorine-containing olefin compounds and alcoholic impurities. However, it generates heat when adsorbing alcoholic impurities, and when heated, hexafluorodiolefin undergoes rearrangement isomerization, easily generating impurities such as hexafluoro-2-butyne, which are difficult to remove.

[0012] CN111247120 discloses an extraction distillation method for crude hexafluorobutadiene containing octafluoro-1-butene, octafluoro-2-butene, heptafluoro-1-butene, and heptafluoro-2-butene, using oxygen-containing hydrocarbons such as alcohols, ketones, and ethers, halogenated saturated hydrocarbons, and halogenated unsaturated hydrocarbons as extraction solvents, with a theoretical plate count of 14. A hexafluorobutadiene product with a purity of 99.99% is obtained.

[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, while it discloses that water is removed from the product using extractants and that the separated crude hexafluorobutadiene does not contain heptafluorobutene impurities, it does not disclose the purity of the hexafluorobutadiene product.

[0014] CN116903438 discloses a method for purifying hexafluorobutene using a combined extraction and adsorption technique. Using furfural, methyl ethyl ketone, and cyclopentanone as extractants, and modified graphene oxide doped with organic bases and copper salts as the adsorbent, the maximum product purity reaches 5N or higher, but the purity of the raw materials is not specified.

[0015] In contrast to the shortcomings of conventional technologies, there is a need to provide a method for producing hexafluorobutadiene that is simple in process and low in cost. [Overview of the project] [Problems that the invention aims to solve]

[0016] This application provides a method for producing hexafluorobutadiene to mitigate the problems of related technologies, such as high cost, numerous steps, low yield, and safety risks, thereby compensating for the shortcomings of conventional methods for producing hexafluorobutadiene. The technical pathway of this invention is as follows.

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

[0018] To achieve the objective of this invention, the present invention employs the following technical solution.

[0019] A method for producing hexafluorobutadiene comprising the following steps (1) and (2), Step (1) involves placing a trifluorovinyl zinc bromide solution, a catalyst, and a first organic solvent into a pressure reactor, purging it with an inert gas, and then adding bromotrifluoroethylene and reacting it to obtain hexafluorobutadiene. The catalyst comprises a monovalent copper salt or monovalent copper oxide and an organophosphine ligand. Preferably, the monovalent copper salt is one or more selected from cuprous iodide, cuprous bromide, cuprous chloride, and cuprous acetate, and the monovalent copper oxide is cuprous oxide. The organophosphine 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, wherein R1, R2, and R3 are each independently selected from n-propyl group, isopropyl group, n-butyl group, isobutyl group, and tert-butyl group, and preferably the organophosphine ligand is one selected from 1,10-phenanthroline, PPh3, 1,2-bis(diphenylphosphino)ethane, and 2,2'-bis(diphenylphosphino)biphenyl. As the first organic solvent, a polar aprotic organic solvent is used. The first organic solvent is one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphate 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 the water content is ≤200 ppm.

[0021] Step (2), after the reaction is completed, the gas-phase material is passed through a circulating shower system containing a second organic solvent to absorb excess bromotrifluoroethylene and fluorinated olefin impurities generated in the reaction, and the unabsorbed crude hexafluorobutadiene is rectified and purified.

[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-methylimidazolium phosphate, 1-butyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium L-lactate, and 1-butyl-3-methylimidazolium hexafluorophosphate.

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

[0025] The molar ratio of trifluorovinylzinc bromide to monovalent copper salt or monovalent copper oxide in the trifluorovinylzinc 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:(0.01~0.20), and the molar ratio of monovalent copper salt or monovalent copper oxide to organophosphine ligand is 1:(1.0~5.0).

[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:(0.05~0.10), and the molar ratio of monovalent copper salt or monovalent copper oxide to organophosphine ligand is 1:(1.0~3.0).

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

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

[0030] In step (1) above, 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 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 step (2) above, the circulating shower system absorbs water using a two-stage circulating shower, with a temperature of -10 to 20°C and a pressure of 0 to 0.5 MPa.

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

[0034] In the method for producing hexafluorobutadiene described above, if the organic solution absorbed by the circulating shower system is subjected to distillation in step (2), bromotrifluoroethylene can be recovered and reused by directly circulating it.

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

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

[0037] (1) The present invention provides a method for producing hexafluorobutadiene by cross-coupling of bromotrifluoroethylene and trifluorovinyl zinc bromide using an inexpensive monovalent copper salt or oxide as a catalyst and an organophosphorus as a ligand. Compared to oxidative homocoupling processes, this method has advantages such as lower raw material costs and lower emissions of waste liquid, waste gas, 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 resulting crude hexafluorobutadiene has a bromotrifluoroethylene content of ≤0.3% and a heptafluorobutene content of ≤0.02%, reducing the workload for subsequent rectification and purification of the product. 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 by a simple distillation process, thereby improving the utilization rate of trifluoroethylene. [Brief explanation of the drawing]

[0040] [Figure 1] Figure 1 shows a hexafluorobutadiene production apparatus in an embodiment of the present invention, which includes a continuous preparation apparatus for trifluorovinyl zinc bromide solution in 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] Figure 2 shows the chromatogram of the product after rectification in Example 10. [Modes for carrying out the invention]

[0041] Referring to Figure 1, the manufacturing system used in the present invention will first be described. The system includes a pressure-resistant reactor 3, a condenser 4, a buffer tank 5, a first shower circulation absorption tower 6, a second shower circulation absorption tower 7, and a crude product tank 8.

[0042] Bromotrifluoroethylene cylinder 1 and trifluorovinyl zinc bromide solution cylinder 2 are connected to the supply port of the pressure reactor 3, the outlet at the top of the pressure reactor 3 is connected to the supply port of the condenser 4, the outlet of the condenser 4 is connected to the supply port of the buffer tank 5, the outlet of the buffer tank 5 is connected to the supply port of the first shower circulation absorption tower 6, the outlet of the first shower circulation absorption tower 6 is connected to the supply port of the second shower circulation absorption tower 7, the outlet of the second shower circulation absorption tower 7 is connected to the supply port of the crude material tank 8, and the outlet of the crude material tank 8 is connected to the rectification equipment.

[0043] In the following, we will conduct practical tests using the system described above.

[0044] (Example 1) (1) In a 5L pressure-resistant reaction vessel made of 316L material, equipped with a condensation reflux apparatus, 1810g (25% mass fraction, 2.0 mol) of N,N-dimethylacetamide solution of trifluorovinyl zinc bromide, 1000g (150 ppm moisture), 38.2g (0.2 mol) of cuprous iodide, and 72.2g (0.4 mol) of 1,10-phenanthroline were added. The reaction vessel was replaced with high-purity nitrogen gas and the system was evacuated until the vacuum level reached ≥0.1 MPa. 644 g (4.0 mol) of bromotrifluoroethylene was added to a pressure vessel, 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The trifluorovinyl zinc bromide was found to have been completely converted.

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

[0046] (3) The 1-butyl-3-methylimidazole hexafluorophosphate solution in the two-stage circulating shower system 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 cooling trap absorption device using liquid nitrogen as the coolant. The results were as follows: A total of 341.9 g was collected in cooling trap 2, with a chromatographic content of bromotrifluoroethylene of 89.50% and a chromatographic content of hexafluorobutadiene of 9.75%. The content of each other component is shown in Table 2.

[0047] (Example 2) The procedure in this embodiment was the same as in Embodiment 1, with the only difference being the addition of 19.1 g (0.1 mol) of cuprous iodide instead of 38.2 g (0.2 mol) to a 5 L pressure-resistant reaction vessel made of 316 L material, while keeping all other conditions 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinyl zinc bromide was 94.5%.

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

[0050] In step (3), a total of 358.7 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 90.80%, the chromatographic content of hexafluorobutadiene was 8.55%, and the content of each other component is shown in Table 2.

[0051] (Example 3) The procedure in this embodiment was the same as in Embodiment 1, with the only difference being the addition of 19.8 g (0.2 mol) of cuprous iodide to a 5 L pressure-resistant reaction vessel made of 316 L material, while keeping all other conditions 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance being trifluoromethylbenzene). The trifluorovinyl zinc bromide was found to have been completely converted.

[0053] In step (2), 244.0 g of crude hexafluorobutadiene was collected in cooling trap 1, with a purity of 96.32%. Converted to a weight percentage, this was 235 g, the theoretical yield was 324.0 g, and the yield was 72.5%. The content of each impurity in the crude hexafluorobutadiene is shown in Table 1.

[0054] In step (3), a total of 339.3 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 89.25%, the chromatographic content of hexafluorobutadiene was 10.10%, and the content of each other component is shown in Table 2.

[0055] (Example 4) The procedure in this example was the same as in Example 1, with the only difference being the addition of 104.9 g (0.4 mol) of triphenylphosphine to a 5 L pressure-resistant reaction vessel made of 316 L material, while keeping all other conditions 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinyl zinc bromide was 97.9%.

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

[0058] In step (3), a total of 340.6 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 91.40%, the chromatographic content of hexafluorobutadiene was 8.29%, and the content of each other component is shown in Table 2.

[0059] (Example 5) The procedure in this example was the same as in Example 1, with the only difference being the addition of 1810 g (25% mass fraction, 2.0 mol) of N,N-dimethylacetamide solution of trifluorovinyl zinc bromide to a 5 L pressure-resistant reaction vessel made of 316 L material, which was replaced with the addition of 1810 g (25% mass fraction, 2.0 mol) of N,N-dimethylformamide solution of trifluorovinyl zinc bromide, and 1000 g (150 ppm moisture) of N,N-dimethylacetamide was replaced with 1000 g (150 ppm moisture), while all other conditions remained 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance being trifluoromethylbenzene). The trifluorovinyl zinc bromide was found to have been completely converted.

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

[0062] In step (3), a total of 338.7 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 89.85%, the chromatographic content of hexafluorobutadiene was 9.31%, and the content of each other component is shown in Table 2.

[0063] (Example 6) The procedure in this embodiment was the same as in Embodiment 1, with the only difference being that raising the internal temperature of the reaction vessel to 100°C was replaced with raising the internal temperature to 80°C, while other conditions remained unchanged. 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinyl zinc bromide was 80.5%.

[0065] In step (2), 205.6 g of crude hexafluorobutadiene was collected in cooling trap 1 with a purity of 95.50%, which corresponds to 196.4 g by weight. The theoretical yield was 324.0 g, and the yield was 60.6%. The content of each impurity in the crude hexafluorobutadiene is shown in Table 1.

[0066] In step (3), a total of 391.28 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 93.31%, the chromatographic content of hexafluorobutadiene was 5.75%, and the content of each other component is shown in Table 2.

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

[0068] In step (2), 253.0 g of crude hexafluorobutadiene was collected in cooling trap 1 with a purity of 96.20%, which corresponds to 247.2 g when converted to a fraction by weight. The theoretical yield was 324.0 g, and the yield was 76.3%. The content of each impurity in the crude hexafluorobutadiene is shown in Table 1.

[0069] In step (3), a total of 337.85 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 89.61%, the chromatographic content of hexafluorobutadiene was 9.20%, and the content of each other component is shown in Table 2.

[0070] (Example 8) The operation in this embodiment was the same as in Embodiment 1, with the only difference being that in step (2), the internal temperature of the two-stage circulating shower device was controlled to be 4-6°C, while other conditions remained unchanged. The results were as follows.

[0071] In step (2), 233.8 g of crude hexafluorobutadiene was collected in cooling trap 1 with a purity of 97.85%, which corresponds to 228.8 g when converted to a fraction by weight. The theoretical yield was 324.0 g, and the yield was 70.6%. The content of each impurity in the crude hexafluorobutadiene is shown in Table 1.

[0072] In step (3), a total of 356.4 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 88.02%, the chromatographic content of hexafluorobutadiene was 11.46%, and the content of each other component is shown in Table 2.

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

[0074] The input amount was 691g (converted to a percentage by weight, the mass of bromotrifluoroethylene was 644g). Other conditions remained 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance being trifluoromethylbenzene). The trifluorovinyl zinc bromide was found to have been completely converted.

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

[0077] In step (3), a total of 341.9 g was collected in cooling trap 2. The chromatographic content of bromotrifluoroethylene was 88.90%, the chromatographic content of hexafluorobutadiene was 10.52%, and the content of each other component is shown in Table 2.

[0078] [Table 1]

[0079] [Table 2]

[0080] (Example 10) Using the crude hexafluorobutadiene prepared in Examples 1-7 as raw materials, rectification experiments were conducted, and the rectification column parameters and rectification parameters are shown in Tables 3 and 4 below.

[0081] [Table 3]

[0082] [Table 4] In the rectification process, 800g was supplied, yielding 57.5g of pre-distillate, resulting in 608g of product and 118.5g of residue. The product purity was 99.990%, the rectification yield per batch was 76.0%, and the material balance ratio was 98.0%. Refer to Figure 2 for the chromatogram of the product after rectification, and the results are as follows.

[0083] [Table 5]

[0084] (Comparative Example 1) The procedure in this example was the same as in Example 1, with the only difference being that no monovalent copper salt catalyst was added in step (1), and all other conditions remained 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinyl zinc bromide was 0.5%.

[0086] In step (2), no hexafluorobutadiene product was collected in cooling trap 1.

[0087] (Comparative Example 2) The procedure in this example was the same as in Example 1, with the only difference being that no organic phosphine ligand was added in step (1), and all other conditions remained 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 pressure vessel and analyzed by the internal standard method using fluorine nuclear magnetic resonance (the internal standard substance was trifluoromethylbenzene). The conversion rate of trifluorovinyl zinc bromide was 62.2%.

[0089] In step (2), 65.3 g of crude hexafluorobutadiene was collected in cooling trap 1, with a purity of 95.47%. Converted to a fraction by weight, this was 62.3 g, the theoretical yield was 162.0 g, and the yield was 38.5%.

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

[0091] (Comparative Example 3) The procedure in this example was the same as in Example 1, with the only difference being the following: The product prepared in step (1) was collected directly into a cooling trap absorption apparatus using liquid nitrogen as the coolant, without undergoing the treatment in step (2). The results were as follows: 607.3 g of crude hexafluorobutadiene was collected in cooling trap 1, with a purity of 41.7%, which corresponds to 253.4 g when converted to a fraction by weight, with a theoretical yield of 324.0 g and a yield of 78.2%.

Claims

1. Including step (1) and step (2), In step (1), the trifluorovinyl zinc bromide solution, catalyst, and first organic solvent are placed in a pressure reactor, purged with an inert gas, and then bromotrifluoroethylene is added and reacted to obtain hexafluorobutadiene. The catalyst comprises a monovalent copper salt or monovalent copper oxide and an organophosphine ligand. Alternatively, the catalyst comprises a monovalent copper salt or monovalent copper oxide and 1,10-phenanthroline. The organic phosphine ligand is PPh ３ , PR １ R ２ R ３ , PPhR １ R ２ , PPh ２ R １ , 1,2-bis(diphenylphosphino)ethane, and 2,2'-bis(diphenylphosphino)biphenyl, and is any one or more selected therefrom, provided that R １ , R ２ , R ３ is 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, As the first organic solvent, a polar aprotic organic solvent is used. In step (2), after the reaction is complete, the gas phase material obtained in step (1) 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. A method for producing hexafluorobutadiene, characterized in that the second organic solvent is selected from polar aprotic organic solvents or ionic liquids.

2. The method for producing hexafluorobutadiene according to claim 1, characterized in that the monovalent copper salt is one or more selected from 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, hexamethylphosphate 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. A method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that the polar aprotic organic solvent used as the second organic solvent is one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, hexamethylphosphate triamide, dimethyl sulfoxide, and sulfolane, and the ionic liquid is 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 claim 1 or 2, characterized in that the first organic solvent described in step (1) is selected from N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane.

5. The method for producing hexafluorobutadiene according to claim 1 or 2, 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. 1) 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), 2) The molar ratio of trifluorovinyl zinc bromide to the monovalent copper salt or monovalent copper oxide in the trifluorovinyl zinc bromide solution is 1:(0.05 to 0.10), 3) The molar ratio of the monovalent copper salt or monovalent copper oxide to the organophosphine ligand is 1:(1.0 to 5.0), 4) The method for producing hexafluorobutadiene according to claim 5, characterized in that at least one of the following conditions is met: the molar ratio of the monovalent copper salt or monovalent copper oxide to the organophosphine ligand is 1:(1.0 to 3.0).

7. 1) The molar ratio of trifluorovinyl zinc bromide to bromotrifluoroethylene in the trifluorovinyl zinc bromide solution is 1:(1 to 10), 2) The method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that at least one of the following conditions is met: the molar ratio of trifluorovinyl zinc bromide to bromotrifluoroethylene in the trifluorovinyl zinc bromide solution is 1:(1.0 to 5.0).

8. 1) 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, 2) A method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that at least one of the following conditions is met 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. A method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that the second organic solvent described in step (2) is one or more selected from 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. 1) The circulating shower system described in step (2) is absorbed by a two-stage circulating shower, the temperature inside the circulating shower system is -10°C to 20°C, and the pressure is 0 MPa to 0.5 MPa, 2) A method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that at least one of the following conditions is met: the temperature in the circulating 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 claim 1 or 2, characterized in that by performing a distillation treatment on the organic solution absorbed by the circulating shower system described in step (2) above, bromotrifluoroethylene can be recovered and reused by directly circulating it.

12. The method for producing hexafluorobutadiene according to claim 1 or 2, characterized in that the bromotrifluoroethylene content in the crude hexafluorobutadiene treated with a circulating shower system is ≤0.3%, the heptafluorobutene content is ≤0.02%, and after rectification, a hexafluorobutadiene product with a purity of ≥99.99% can be obtained.

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