Hexafluoro-1,3-butadiene and its synthesis method and synthesis device

Abstract

The present application belongs to the technical field of organic fluorine chemical industry, and particularly relates to hexafluoro-1,3-butadiene and a synthesis method and a synthesis device thereof. The synthesis method of the hexafluoro-1,3-butadiene is synthesized according to the following synthesis process route: firstly, triphenylphosphine is reacted with difluorochloromethane raw material to obtain triphenyldifluoromethylphosphonium halide which is reacted with sodium hydride to prepare difluoromethyltriphenylphosphorane; then trifluoroethylene is reacted with carbonyl chloride fluoride to generate enoyl fluoride intermediate; finally, the enoyl fluoride intermediate is reacted with difluoromethyltriphenylphosphorane to generate hexafluoro-1,3-butadiene. The synthesis method of the hexafluoro-1,3-butadiene provided by the present application has mild conditions, is stable and has low risk; the hexafluoro-1,3-butadiene product synthesized by using the synthesis method of the present application has good selectivity, high purity and high yield; the synthesis device used in the synthesis method of the present application has low equipment cost and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of organofluorine chemical technology, specifically relating to hexafluoro-1,3-butadiene and its synthesis method and apparatus. Background Technology

[0002] Hexafluoro-1,3-butadiene (HFBD, CAS No. 685-63-2) is a perfluorinated conjugated diene with the structural formula CF2=CF-CF=CF2. Due to its unique physicochemical properties, such as high stability, low global warming potential (GWP), and excellent etch selectivity, this compound shows great application potential in the fine etching processes of semiconductor manufacturing. It is also a key intermediate for the synthesis of high-value-added fluorinated specialty chemicals. With the rapid development of the electronics and information industry, the demand for high-purity hexafluoro-1,3-butadiene is increasingly urgent, making the development of efficient, safe, and low-cost synthesis technologies of great significance.

[0003] Currently, there are some literature and patent reports on the synthesis technology of hexafluoro-1,3-butadiene, but its industrial application still faces many challenges. Existing synthetic routes are usually cumbersome, have harsh reaction conditions, and suffer from low selectivity.

[0004] For example, Chinese patent CN111675597A discloses a method for preparing hexafluoro-1,3-butadiene by reacting 1,2-dibromo-1-chloro-1,2,2-trifluoroethane with trifluoroethylene halothane and then dehalogenating with zinc powder. Although this process optimizes the reaction steps, the reaction still needs to be carried out at a temperature close to 100°C and under certain pressure. These harsh reaction conditions affect the selectivity and final yield of the target product.

[0005] Chinese patent CN112645794A discloses a route that uses R22 (difluoromethane chloride) as a raw material, which is cracked to produce tetrafluoroethylene (TFE), then reacts with bromine to generate dibromotetrafluoroethane, and finally couples with TFE in the presence of zinc powder and a specific solvent to generate the target product. This route has certain advantages in terms of raw material cost control, but the reaction temperature of its key steps is still above 100°C, and it requires the introduction of oxygen for oxidation. This not only places extremely high demands on the temperature and pressure resistance and operational safety of the production equipment, but also leads to high energy consumption in the production process.

[0006] Therefore, existing processes for synthesizing hexafluoro-1,3-butadiene generally suffer from the following common defects: harsh reaction conditions, mostly carried out under high temperature and high pressure, resulting in high production risk and strong dependence on the technical level of operators; high reaction temperature leads to high energy consumption and long reaction time, resulting in low overall reaction efficiency; complex reaction path, many side reactions, unsatisfactory selectivity of target product, and generation of complex by-product mixtures, making subsequent separation and purification processes difficult and costly. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for synthesizing hexafluoro-1,3-butadiene with mild and stable conditions and low risk. The hexafluoro-1,3-butadiene product synthesized by the method of the present invention has good selectivity, high purity and high yield. The synthesis apparatus used in the synthesis method of the present invention has low equipment cost and low energy consumption.

[0008] The method for synthesizing hexafluoro-1,3-butadiene according to the present invention is as follows: First, triphenylphosphine is reacted with difluorohalomethane as a raw material, and the resulting triphenyldifluoromethyl phosphorus halide is reacted with sodium hydride to prepare difluoromethyltriphenylphosphine; then, trifluoroethylene is reacted with carbonyl chloride fluoride to generate an acyl fluoride intermediate; finally, the acyl fluoride intermediate is reacted with difluoromethyltriphenylphosphine to generate hexafluoro-1,3-butadiene.

[0009] The molar ratio of triphenylphosphine, difluorohalomethane, and sodium hydride is 1:1.1~1.3:0.8~1.

[0010] The molar ratio of trifluoroethylene, carbonyl chloride fluoride, and sodium hydride is 1.2~1.5:1~1.2:1, and the molar ratio of acid-binding agent to sodium hydride is 1~1.1:1.

[0011] All reactions are carried out in an organic solvent, which is one of toluene, tetrahydrofuran, or propyl ether.

[0012] An acid-binding agent is added during the reaction of trifluoroethylene with carbonyl chloride fluoride. The acid-binding agent is triethylamine or N,N-dimethylbenzylamine.

[0013] The reaction temperature of the triphenylphosphine with the difluorohalomethane raw material is controlled at 35~50℃ and the pressure is controlled at 0.1MPa~0.3MPa; the reaction temperature of the triphenyldifluoromethyl phosphorus halide with sodium hydride is controlled at 30~45℃; the difluorohalomethane is difluorochloromethane or difluorobromomethane.

[0014] The reaction temperature of trifluoroethylene with carbonyl chloride fluoride is controlled at 0~5℃; the reaction temperature of enoyl fluoride intermediate with difluoromethyltriphenylphosphine is controlled at 10~15℃.

[0015] A hexafluoro-1,3-butadiene is obtained by the synthetic method of the aforementioned hexafluoro-1,3-butadiene.

[0016] The apparatus for synthesizing hexafluoro-1,3-butadiene includes reactor a, reactor b, and reactor c. Reactor a has a feed pipe connected to cryogenic reactor a and cryogenic reactor b. Reactor a's feed pipe is connected to reactor c, and reactor c is connected to reactor b. Reactor a's top is connected to a vertical condenser a and a packing section a. The connecting pipe between the vertical condenser a and the packing section a passes through a desalination tank and is then connected to the feed pipe of reactor a. Reactor c's top is connected to a vertical condenser b and a packing section b.

[0017] The feed pipe of reactor b is connected to the difluorohalomethane feed tank; packing section b is connected to the hydrogen treatment device and the target product collection tank; packing section a is connected to the tail gas treatment system; and the cryogenic reactor a is connected to the trifluoroethylene feed tank and the carbonyl chloride fluoride feed tank.

[0018] The synthetic route for hexafluoro-1,3-butadiene of the present invention is as follows: Figure 2 As shown.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) By designing a completely new synthesis route, this invention completely eliminates the dependence of existing technologies on high-temperature and high-pressure reactions above 100°C. This greatly reduces the risk factor of the production process and the stringent requirements for equipment pressure and temperature resistance, reduces energy consumption, makes operation safer and simpler, and significantly reduces equipment investment and operating costs.

[0021] (2) The route adopted in this invention has fewer side reactions and high selectivity for the target product hexafluoro-1,3-butadiene. At the same time, the by-products generated in the reaction (such as triphenylphosphine oxide) are easy to separate from the product, avoiding the separation and purification difficulties caused by the complexity of by-products in the prior art. This results in high purity and stable yield of the final product, and simplifies the subsequent purification process.

[0022] (3) The raw materials used in this invention (such as triphenylphosphine, difluorochloromethane, trifluoroethylene, etc.) are relatively easy to obtain or can be prepared efficiently. Furthermore, the synthesis device enables effective connection and material circulation between each step. The entire process is compact and highly continuous, reducing material transfer losses and improving production efficiency and overall atom economy. This lays a solid foundation for the large-scale, low-cost production of hexafluoro-1,3-butadiene. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the apparatus for synthesizing hexafluoro-1,3-butadiene according to the present invention.

[0024] Figure 2 This is a schematic diagram of the synthesis process route of hexafluoro-1,3-butadiene of the present invention.

[0025] In the diagram: 1. Trifluoroethylene feed tank; 2. Carbonyl chloride fluoride feed tank; 3. Cryogenic reactor a; 4. Cryogenic reactor b; 5. Reactor a; 6. Desalination tank; 7. Vertical condenser a; 8. Packing section a; 9. Tail gas treatment system; 10. Difluorohalomethane feed tank; 11. Reactor b; 12. Reactor c; 13. Vertical condenser b; 14. Packing section b; 15. Hydrogen treatment device; 16. Target product collection tank. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments.

[0027] The raw materials and additives used in the following examples and comparative examples are all commercially available products. The apparatus described are all standard experimental apparatus in the chemical industry; their functionality is sufficient for their use.

[0028] like Figure 1 As shown, the apparatus for synthesizing hexafluoro-1,3-butadiene includes reactor a5, reactor b11, and reactor c12. Low-temperature reactors a3 and b4 are installed on the feed pipe of reactor a5. The feed pipe of reactor a5 is connected to reactor c12, and reactor c12 is connected to reactor b11. A vertical condenser a7 and a packing section a8 are connected to the top of reactor a5. The connection between the vertical condenser a7 and the packing section a8 is via a desalination tank 6 and then connected to the feed pipe of reactor a5. A vertical condenser b13 and a packing section b14 are connected to the top of reactor c12.

[0029] The feed pipe of the reactor b11 is connected to the difluorohalomethane feed tank 10; the packing section b14 is connected to the hydrogen treatment device 15 and the target product collection tank 16; the packing section a8 is connected to the tail gas treatment system 9; and the cryogenic reactor a3 is connected to the trifluoroethylene feed tank 1 and the carbonyl chloride fluoride feed tank 2.

[0030] The packing material for packing section a8 is Pall rings made of PTFE.

[0031] The packing material for packing section B14 is Pall rings made of PTFE.

[0032] Specifically, the method for synthesizing hexafluoro-1,3-butadiene using the apparatus of the present invention includes the following steps:

[0033] Step 1: Solvent and triphenylphosphine are added to reactor b11. Difluorohalomethane from difluorohalomethane feedstock 10 is added to reactor b11 at a certain feeding rate. During the feeding process, the temperature of reactor b11 is controlled at 35~50℃ and the pressure is controlled at 0.1MPa~0.3MPa. After the feeding is completed, the reaction continues for 0.5~1.5 hours.

[0034] The second reaction step involves adding the solvent and sodium hydride to reactor C12. The temperatures of reactor C12 and vertical condenser B13 are set to 30-45°C and 5-10°C respectively, and connected to the hydrogen treatment device 15. The reaction solution in reactor B11 is pumped into reactor C12 at a certain rate. After the pumping is complete, the reaction is maintained at this temperature for 1-1.5 hours. The resulting reaction solution serves as the raw material for the fourth reaction step.

[0035] The third reaction step: The solvent and acid-binding agent are added to reactor a5. The temperatures of cryogenic reactor a3, cryogenic reactor b4, reactor a5, and vertical condenser a7 are set to -15~-10℃, -8~-2℃, 0℃~5℃, and -8~-2℃, respectively. The feed solutions from trifluoroethylene raw material tank 1 and carbonyl chloride fluoride raw material tank 2 are introduced. During the introduction process, organic hydrogen chloride salts are removed through desalting tank 6 and circulating pump group. The introduction process lasts for 3~5 hours. After the introduction is complete, the reaction is continued at the same temperature for 1~1.5 hours. The tail gas from the reaction process enters the tail gas treatment system 9. (Hydrogen chloride combines with the acid-binding agent to form salts, and the acid-binding agent is subsequently recovered through alkaline treatment).

[0036] Fourth step of the reaction: Reduce the temperature of reactor C12 to 10-15℃, set the temperature of vertical condenser B13, and close the connection valve of the hydrogen treatment device. Open the connection valve of the target product collection tank 16 for hexafluoro-1,3-butadiene. Add the reaction solution from reactor A5 to reactor C12. After the addition is complete, continue the reaction at this temperature for 0.5-1 hour. The resulting target product, hexafluoro-1,3-butadiene, enters the target product collection tank 16, ultimately yielding hexafluoro-1,3-butadiene.

[0037] The purity of the raw materials is as follows:

[0038] Triphenylphosphine: 99.5% purity; Trifluoroethylene raw material: 99.5% purity; Difluorochloromethane: 99% purity; Difluorobromomethane: 99% purity; Sodium hydride: 99% purity; Carbonyl chloride fluoride: 99.5% purity; Triethylamine: 99% purity; N,N-Dimethylbenzylamine: 99.2%.

[0039] The amount of material added and the subsequent yield are both calculated in moles.

[0040] Example 1

[0041] The method for synthesizing hexafluoro-1,3-butadiene using the apparatus of the present invention includes the following steps:

[0042] Step 1: 8.01 kg of toluene and 5.324 kg of triphenylphosphine were added to reactor b11. Difluorochloromethane from difluorohalomethane feedstock tank 10 was added to reactor b11 at a rate of 0.529 kg / h. During the addition process, the temperature of reactor b11 was controlled at 43℃ and the pressure at 0.1 MPa. A total of 2.117 kg was added, and the reaction continued for 1 hour after the addition was completed.

[0043] The second reaction step involves adding 8.03 kg of toluene and 0.44 kg of sodium hydride to reactor C12. The temperatures of reactor C12 and vertical condenser B13 are set to 38°C and 7°C respectively, and connected to hydrogen treatment device 15. The reaction solution in reactor B11 is pumped into reactor C12 at a rate of 3.815 kg / h. After the pumping is complete, the reaction is maintained at this temperature for 1.2 hours. The resulting reaction solution is used as the raw material for the fourth reaction step.

[0044] The third reaction step: 7.98 kg of toluene and 2.601 kg of N,N-dimethylbenzylamine were added to reactor a5. The temperatures of cryogenic reactors a3 and b4, reactor a5, and vertical condenser a7 were set to -12℃, -6℃, 3℃, and -6℃, respectively. The trifluoroethylene feed rate in trifluoroethylene feed tank 1 was 0.505 kg / h, and the carbonyl chloride fluoride feed rate in carbonyl chloride fluoride feed tank 2 was 0.414 kg / h. During the addition to reactor a5, the organic hydrogen chloride salt was removed through desalting tank 6 and circulating pump group. The addition lasted for 4 hours, with a total of 2.023 kg of trifluoroethylene and 1.657 kg of carbonyl chloride fluoride introduced. After the addition was completed, the reaction was maintained at the temperature for 1.3 hours. The tail gas from the reaction process entered the tail gas treatment system 9. (Hydrogen chloride combines with the acid-binding agent to form a salt, which is subsequently recovered by alkaline treatment.)

[0045] Step 4: The temperature of reactor C12 is lowered to 12℃, the temperature of vertical condenser B13 is set to 6℃, the connection valve of the hydrogen treatment device is closed, and the connection valve of the hexafluoro-1,3-butadiene target product collection tank 16 is opened. The reaction liquid in reactor A5 is added to reactor C12 at a flow rate of 3.545 kg / h, and the reaction is continued at the same temperature for 1 hour after the addition is complete. The target product hexafluoro-1,3-butadiene is collected in target product collection tank 16, and 2.951 kg of hexafluoro-1,3-butadiene is finally obtained. The purity of hexafluoro-1,3-butadiene is 97% according to gas phase analysis, and the yield is 96% (based on the molar amount of sodium hydride).

[0046] Example 2

[0047] The method for synthesizing hexafluoro-1,3-butadiene using the apparatus of the present invention includes the following steps:

[0048] Step 1: 8.01 kg of toluene and 5.298 kg of triphenylphosphine were added to reactor b11. Difluorochloromethane from difluorohalomethane feedstock tank 10 was added to reactor b11 at a rate of 0.387 kg / h. During the addition process, the temperature of reactor b11 was controlled at 50℃ and the pressure at 0.15 MPa. A total of 1.939 kg was added, and the reaction continued for 1.5 hours after the addition was completed.

[0049] The second reaction step involves adding 8.03 kg of toluene and 0.392 kg of sodium hydride to reactor C12. The temperatures of reactor C12 and vertical condenser B13 are set to 45°C and 5°C respectively, and connected to hydrogen treatment device 15. The reaction solution in reactor B11 is pumped into reactor C12 at a rate of 3.026 kg / h. After the pumping is complete, the reaction is maintained at this temperature for 1.5 hours. The resulting reaction solution is used as the raw material for the fourth reaction step.

[0050] The third reaction step: 7.99 kg of toluene and 2.216 kg of N,N-dimethylbenzylamine were added to reactor a5. The temperatures of cryogenic reactors a3 and b4, reactor a5, and vertical condenser a7 were set to -10℃, -2℃, 5℃, and -8℃, respectively. The trifluoroethylene feed rate in trifluoroethylene feed tank 1 was 0.321 kg / h, and the carbonyl chloride fluoride feed rate in carbonyl chloride fluoride feed tank 2 was 0.269 kg / h. During the addition to reactor a5, the organic hydrogen chloride salt was removed through desalting tank 6 and circulating pump group. The addition lasted for 5 hours, with a total of 1.607 kg of trifluoroethylene and 1.347 kg of carbonyl chloride fluoride added. After the addition was complete, the reaction was continued at the same temperature for 1.5 hours. The tail gas from the reaction process entered the tail gas treatment system 9. (Hydrogen chloride combines with the acid-binding agent to form a salt, which is subsequently recovered by alkaline treatment).

[0051] Step 4: The temperature of reactor C12 is lowered to 15℃, the temperature of vertical condenser B13 is set to 6℃, the connection valve of the hydrogen treatment device is closed, and the connection valve of the hexafluoro-1,3-butadiene target product collection tank 16 is opened. The reaction liquid in reactor A5 is added to reactor C12 at a flow rate of 2.81 kg / h, and the reaction is continued at the same temperature for 1 hour after the addition is complete. The target product hexafluoro-1,3-butadiene is collected in target product collection tank 16, and 2.593 kg of hexafluoro-1,3-butadiene is finally obtained. The purity of hexafluoro-1,3-butadiene is 94% according to gas phase analysis, and the yield is 93% (based on the molar amount of sodium hydride).

[0052] Example 3

[0053] The method for synthesizing hexafluoro-1,3-butadiene using the apparatus of the present invention includes the following steps:

[0054] Step 1: 8.03 kg of toluene and 5.245 kg of triphenylphosphine were added to reactor b11. Difluorochloromethane from difluorohalomethane feedstock tank 10 was added to reactor b11 at a rate of 0.753 kg / h. During the addition process, the temperature of reactor b11 was controlled at 35℃ and the pressure at 0.3 MPa. A total of 2.259 kg was added, and the reaction continued for 0.5 h after the addition was completed.

[0055] The second reaction step: 8.01 kg of toluene and 0.482 kg of sodium hydride were added to reactor C12. The temperatures of reactor C12 and vertical condenser B13 were set to 30°C and 10°C respectively, and the hydrogen treatment device 15 was connected. The reaction solution in reactor B11 was pumped into reactor C12 at a rate of 5.073 kg / h. After the pumping was completed, the reaction was maintained at this temperature for 1 hour. The reaction solution after the reaction was completed was used as the raw material for the fourth reaction step.

[0056] The third reaction step: 8.01 kg of toluene and 2.983 kg of N,N-dimethylbenzylamine were added to reactor a5. The temperatures of cryogenic reactors a3 and b4, reactor a5, and vertical condenser a7 were set to -15℃, -8℃, 0℃, and -2℃, respectively. The trifluoroethylene feed rate in trifluoroethylene feed tank 1 was 0.82 kg / h, and the carbonyl chloride fluoride feed rate in carbonyl chloride fluoride feed tank 2 was 0.659 kg / h. During the addition to reactor a5, the organic hydrogen chloride salt was removed through desalting tank 6 and circulating pump group. The addition lasted for 3 hours, with a total of 2.46 kg of trifluoroethylene and 1.979 kg of carbonyl chloride fluoride introduced. After the addition was completed, the reaction was continued at the temperature for 1 hour. The tail gas from the reaction process entered the tail gas treatment system 9. (Hydrogen chloride combines with the acid-binding agent to form a salt, which is subsequently recovered by alkaline treatment).

[0057] Step 4: The temperature of reactor C12 is lowered to 10℃, the temperature of vertical condenser B13 is set to 6℃, the connection valve of the hydrogen treatment device is closed, and the connection valve of the hexafluoro-1,3-butadiene target product collection tank 16 is opened. The reaction liquid in reactor A5 is added to reactor C12 at a flow rate of 4.8 kg / h, and the reaction is continued at the same temperature for 0.5 h after the addition is complete. The target product hexafluoro-1,3-butadiene is collected in target product collection tank 16, and 3.197 kg of hexafluoro-1,3-butadiene is finally obtained. The purity of hexafluoro-1,3-butadiene is 94.3% according to gas phase analysis, and the yield is 93.5% (based on the molar amount of sodium hydride).

[0058] Example 4

[0059] The method for synthesizing hexafluoro-1,3-butadiene using the apparatus of the present invention includes the following steps:

[0060] Step 1: 8.01 kg of tetrahydrofuran and 5.14 kg of triphenylphosphine were added to reactor b11. Difluorochloromethane from difluorohalomethane feedstock tank 10 was added to reactor b11 at a rate of 0.51 kg / h. During the addition process, the temperature of reactor b11 was controlled at 40℃ and the pressure at 0.3 MPa. A total of 2.043 kg was added, and the reaction continued for 1 hour after the addition was completed.

[0061] The second reaction step involves adding 8.1 kg of tetrahydrofuran and 0.449 kg of sodium hydride to reactor C12. The temperatures of reactor C12 and vertical condenser B13 are set to 40°C and 8°C respectively, and connected to hydrogen treatment device 15. The reaction solution in reactor B11 is pumped into reactor C12 at a rate of 3.752 kg / h. After the pumping is complete, the reaction is maintained at this temperature for 1.5 hours. The resulting reaction solution serves as the raw material for the fourth reaction step.

[0062] The third reaction step: 8.03 kg of tetrahydrofuran and 2.044 kg of triethylamine were added to reactor a5. The temperatures of cryogenic reactors a3 and b4, reactor a5, and vertical condenser a7 were set to -12℃, -5℃, 3℃, and -6℃, respectively. The trifluoroethylene feed rate in trifluoroethylene feed tank 1 was 0.534 kg / h, and the carbonyl chloride fluoride feed rate in carbonyl chloride fluoride feed tank 2 was 0.429 kg / h. During the addition to reactor a5, the organic hydrogen chloride salt was removed through desalting tank 6 and circulating pump group. The addition lasted for 4 hours, with a total of 2.137 kg of trifluoroethylene and 1.719 kg of carbonyl chloride fluoride introduced. After the addition was completed, the reaction was maintained at the temperature for 1.5 hours. The tail gas from the reaction process entered the tail gas treatment system 9. (Hydrogen chloride combines with the acid-binding agent to form a salt, which is subsequently recovered by alkaline treatment.)

[0063] Step 4: The temperature of reactor C12 is lowered to 12℃, the temperature of vertical condenser B13 is set to 6℃, the connection valve of the hydrogen treatment device is closed, and the connection valve of the hexafluoro-1,3-butadiene target product collection tank 16 is opened. The reaction liquid in reactor A5 is added to reactor C12 at a flow rate of 3.356 kg / h, and the reaction is continued at the same temperature for 1 hour after the addition is complete. The target product hexafluoro-1,3-butadiene is collected in target product collection tank 16, and 3.004 kg of hexafluoro-1,3-butadiene is finally obtained. The purity of hexafluoro-1,3-butadiene is 95.2% according to gas phase analysis, and the yield is 95.3% (based on the molar amount of sodium hydride).

[0064] Example 5

[0065] The method for synthesizing hexafluoro-1,3-butadiene using the apparatus of the present invention includes the following steps:

[0066] Step 1: 7.97 kg of solvent propyl ether and 5.43 kg of triphenylphosphine were added to reactor b11. Difluorobromomethane from difluorohalomethane feedstock tank 10 was added to reactor b11 at a rate of 0.837 kg / h. During the addition process, the temperature of reactor b11 was controlled at 40℃ and the pressure at 0.15 MPa. A total of 3.335 kg was added, and the reaction continued for 1 hour after the addition was completed.

[0067] The second reaction step involves adding 8.1 kg of propyl ether and 0.474 kg of sodium hydride to reactor C12. The temperatures of reactor C12 and vertical condenser B13 are set to 40°C and 8°C respectively, and connected to hydrogen treatment device 15. The reaction solution in reactor B11 is pumped into reactor C12 at a rate of 4.106 kg / h. After the pumping is complete, the reaction is maintained at this temperature for 1.5 hours. The resulting reaction solution is used as the raw material for the fourth reaction step.

[0068] The third reaction step: 8.03 kg of propyl ether and 2.14 kg of triethylamine were added to reactor a5. The temperatures of cryogenic reactors a3 and b4, reactor a5, and vertical condenser a7 were set to -12℃, -5℃, 3℃, and -6℃, respectively. The trifluoroethylene feed rate in trifluoroethylene feed tank 1 was 0.552 kg / h, and the carbonyl chloride fluoride feed rate in carbonyl chloride fluoride feed tank 2 was 0.454 kg / h. During the addition to reactor a5, the organic hydrogen chloride salt was removed through desalting tank 6 and circulating pump group. The addition lasted for 4 hours, with a total of 2.21 kg of trifluoroethylene and 1.816 kg of carbonyl chloride fluoride introduced. After the addition was completed, the reaction was continued at the temperature for 1.5 hours. The tail gas from the reaction process entered the tail gas treatment system 9. (Hydrogen chloride combines with the acid-binding agent to form a salt, which is subsequently recovered by alkaline treatment.)

[0069] Step 4: The temperature of reactor C12 is lowered to 12℃, the temperature of vertical condenser B13 is set to 6℃, the connection valve of the hydrogen treatment device is closed, and the connection valve of the hexafluoro-1,3-butadiene target product collection tank 16 is opened. The reaction liquid in reactor A5 is added to reactor C12 at a flow rate of 3.425 kg / h, and the reaction is continued at the same temperature for 1 hour after the addition is complete. The target product hexafluoro-1,3-butadiene is collected in target product collection tank 16, and 3.154 kg of hexafluoro-1,3-butadiene is finally obtained. The purity of hexafluoro-1,3-butadiene is 96% according to gas phase analysis, and the yield is 95.5% (based on the molar amount of sodium hydride).

[0070] Comparative Example 1

[0071] This comparative example is the same as Example 1, except that the cryogenic reactors a3 and b4 for the third step reaction were not used, and other preparation conditions were the same. A total of 4.018 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 35% and a yield of 45% (based on the molar amount of sodium hydride).

[0072] Comparative Example 2

[0073] This comparative example is the same as Example 1, except that the reaction temperature and pressure in the first step were changed to 65°C and 0.8 MPa, while other preparation conditions remained the same. A final yield of 2.668 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 41% and a yield of 35% (based on the molar amount of sodium hydride).

[0074] Comparative Example 3

[0075] This comparative example is the same as Example 1, except that the reaction temperature and pressure in the first step were changed to 15°C and 0.8 MPa, while other preparation conditions remained the same. A final yield of 3.978 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 33% and a yield of 42% (based on the molar amount of sodium hydride).

[0076] Comparative Example 4

[0077] This comparative example is the same as Example 1, except that the reaction temperature in the second step was changed to 18°C, while other preparation conditions remained the same. A total of 3.003 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 51% and a yield of 49% (based on the molar amount of sodium hydride).

[0078] Comparative Example 5

[0079] This comparative example is the same as Example 1, except that no acid-binding agent is added in the third step of the reaction, and other preparation conditions are the same. Finally, 3.632 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 37% and a yield of 43% (based on the molar amount of sodium hydride).

[0080] Comparative Example 6

[0081] This comparative example is the same as Example 1, except that the reaction temperature in reactor a5 in the third step is controlled at 20°C, and other preparation conditions are the same. Finally, 3.46 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 56% and a yield of 62% (based on the molar amount of sodium hydride).

[0082] Comparative Example 7

[0083] This comparative example is the same as Example 1, except that the amount of carbonyl chloride fluoride added in the third step of the reaction is doubled, and other preparation conditions are the same. Finally, 2.411 kg of hexafluoro-1,3-butadiene was obtained, with a gas phase analysis purity of 35% and a yield of 27% (based on the molar amount of sodium hydride).

Claims

1. A method for the synthesis of hexafluoro-1,3-butadiene, characterized in that, The hexafluoro-1,3-butadiene is synthesized according to the following synthetic process route: first, triphenylphosphine is reacted with difluoro halomethane raw material to obtain triphenyl difluoromethyl halogenated phosphorus which is reacted with sodium hydride to prepare difluoromethyltriphenyl phosphine; then trifluoroethylene is reacted with carbonyl chloride fluoride to generate enoyl fluoride intermediate; finally, the enoyl fluoride intermediate is reacted with difluoromethyltriphenyl phosphine to generate hexafluoro-1,3-butadiene; The acid binding agent is triethylamine or N,N-dimethyl benzylamine; The molar ratio of the triphenylphosphine, difluoro halomethane and sodium hydride is 1:1.1-1.3:0.8-1; The molar ratio of the trifluoroethylene, carbonyl chloride fluoride and sodium hydride is 1.2-1.5:1-1.2:1, and the molar ratio of the acid binding agent and sodium hydride is 1-1.1:1; The temperature of the reaction of the triphenylphosphine and difluoro halomethane raw material is controlled at 35-50 DEG C, and the pressure is controlled at 0.1-0.3 MPa; the temperature of the reaction of the triphenyl difluoromethyl halogenated phosphorus and sodium hydride is controlled at 30-45 DEG C; The temperature of the reaction of the trifluoroethylene and carbonyl chloride fluoride is controlled at 0-5 DEG C.

2. The method of synthesizing hexafluoro-1,3-butadiene according to claim 1, characterized in that: Each reaction is carried out in an organic solvent, and the solvent is one of toluene, tetrahydrofuran and diethyl ether.

3. The method for synthesizing hexafluoro-1,3-butadiene according to claim 1, characterized in that: The difluoro halomethane is difluoro chloromethane or difluoro bromomethane.

4. The method for synthesizing hexafluoro-1,3-butadiene according to claim 1, characterized in that: The temperature of the reaction of the enoyl fluoride intermediate and difluoromethyltriphenyl phosphine is controlled at 10-15 DEG C.

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