WO2024016438A1

WO2024016438A1 - Preparation method for hexafluorobutadiene

Info

Publication number: WO2024016438A1
Application number: PCT/CN2022/116782
Authority: WO
Inventors: 周文平; 张前臻; 傅晓腾; 张奎; 张鸿铨
Original assignee: 福建省杭氟电子材料有限公司
Priority date: 2022-07-19
Filing date: 2022-09-02
Publication date: 2024-01-25
Also published as: CN115259993B; CN115259993A

Abstract

The present invention relates to a preparation method for hexafluorobutadiene. The method comprises: 1) performing temperature raising and pressure increase reactions on chlorotrifluoroethylene, and then performing a thermal polymerization reaction on same to obtain a precursor; 2) performing fractional distillation on the precursor and obtaining a low-boiling-point intermediate, and recovering a residual solution; 3) adding the intermediate into ethanol, performing a reflux reaction under a zinc catalyst to collect a gas product, and then mixing the collected gas product with hydrogen iodide, performing high-temperature ring opening, and performing condensation recovery to obtain a condensate solution; and 4) mixing the condensate solution with the residual solution in step 2), reacting with chlorine water under photocatalysis, adding the mixture into diethylene glycol monobutyl ether, performing a heating reaction under a zinc catalyst, performing condensation reflux to remove impurities, and enabling the gas product to pass through a high-temperature porous solid catalyst to obtain hexafluorobutadiene. The preparation process can increase the yield of hexafluorobutadiene to at least 85%, and greatly improves the preparation effect.

Description

A kind of preparation method of hexafluorobutadiene

Technical field

The invention belongs to the field of new energy, and in particular relates to a preparation method of hexafluorobutadiene.

Background technique

Hexafluorobutadiene is an effective gas used in a new generation of dry etching. It can be effectively used to etch dielectric materials such as silicon dioxide and silicon nitride. As a special electron gas, it belongs to the electronic industry system. At present, the electronics industry has become the core industrial system that supports the sustainable development of the national economy and ensures national strategic security. Special electronic gas is one of the key raw materials at the core of the entire electronics industry system. It is widely used in national defense and military, aerospace, new solar cells, electronic products, etc.

However, most of the current preparation methods for hexafluorobutadiene have problems such as low productivity, low yield, and low conversion rate from raw materials to products during the actual production process. For example, the product yields of the new schemes disclosed by Miller and Haszeldine are only less than 30% and about 14% respectively, which restricts the capacity production of hexafluorobutadiene.

For this reason, developing a high-yield, high-yield hexafluorobutadiene preparation process is key to the development of hexafluorobutadiene and new energy technology.

technical problem

In order to solve the problems of the existing hexafluorobutadiene preparation process, such as low product yield, low product purity, and high purification difficulty, the present invention provides a preparation method of hexafluorobutadiene.

The purpose of the present invention is to significantly increase the product yield of hexafluorobutadiene to more than 85%, and to effectively ensure that the purity of the hexafluorobutadiene product can reach more than 99.99%.

Technical solutions

In order to achieve the above objects, the present invention adopts the following technical solutions.

A method for preparing hexafluorobutadiene, which method includes: 1) placing liquid chlorotrifluoroethylene raw material at the bottom of a reaction kettle, raising the temperature and pressure, then guiding it into the reaction vessel for thermal polymerization, condensing and recovering the thermal polymerization product, and Mix the thermal polymerization product into the raw material until the raw material and/or the thermal polymerization product no longer boil, then terminate the recovery to obtain the precursor; 2) High-pressure water bath fractionation of the precursor and obtain low-boiling point intermediates, and recover until the volume of the precursor no longer decreases. The remaining liquid is reserved; 3) Add the intermediate to ethanol and add elemental zinc as a catalyst. After the reflux reaction, collect the gas product and mix the gas product with hydrogen iodide gas for a high-temperature ring-opening reaction, then condense and recover the condensate; 4) Mix the condensate and the residual liquid described in step 2), react with chlorine water under photocatalysis, and then add it to butyl carbitol, and add elemental zinc as a catalyst. After heating the reaction and condensing and refluxing to remove impurities, the gas product passes through high temperature After adding the porous solid catalyst, hexafluorobutadiene is obtained.

Preferably, the temperature and pressure increase control conditions in step 1) are: first control the pressure in the reactor to 0.6-0.8 MPa and then raise the temperature to 42-45°C.

Preferably, the reaction temperature of the thermal polymerization reaction in step 1) is 575-580°C, and the reaction time is 10-12 s.

Preferably, the high-pressure water bath fractionation in step 2) is specifically: placing the precursor in a boiling water bath across water, and controlling the pressure in the container where the precursor is located to be 0.5 to 0.7 MPa.

Preferably, the gas product described in step 3) is mixed with hydrogen iodide gas and then catalytically reacted at high temperature at 285-295°C for 22-26 hours.

Preferably, the illumination reaction in step 4) is carried out for ≥24 h; the illumination reaction is carried out under UV light irradiation.

Preferably, the heating reaction control temperature in step 4) is 145-150°C, and the reaction time is 6-8 h.

Preferably, the porous solid catalyst is composed of activated carbon, potassium fluoride and calcium fluoride; the molar ratio of the potassium fluoride and calcium fluoride is 1: (0.95~1.05), and the activated carbon accounts for 1% of the porous solid catalyst. 50~65 wt% of the total mass.

Preferably, activated carbon, potassium fluoride and calcium fluoride in the porous solid catalyst are mixed and filled in a tubular container, and the flow rate of the gas product is controlled so that the gas product passes through the tubular container within 12 to 14 seconds.

Preferably, the porous solid catalyst in step 4) is preheated to 665-670°C.

In the technical solution of the present invention, chlorotrifluoroethylene is used as raw material, and its boiling and/or volatilization is suppressed by high pressure, so that it can reach a higher temperature and then slowly boil or slowly volatilize and then be directed to a reaction vessel for high-temperature thermal polymerization. If the reaction is not directly heated under high-pressure conditions to cause it to boil or quickly evaporate and be directed to the reaction vessel for thermal polymerization, only about 22 to 24% of 3,4-dichloro-hexafluoro-1-butanol can be obtained. Alkene, and about 38 to 41% of 1,2-dichlorohexafluorocyclobutane is produced as an impurity product. The total yield of the two is not higher than 65%, which usually cannot be directly used effectively, while 3,4-dichlorohexafluorocyclobutane is produced as an impurity product. Chloro-hexafluoro-1-butene also needs to be processed through high-temperature reaction to obtain hexafluorobutadiene. In the technical solution of the present invention, through slow reaction and controlling the reaction process, selective conversion is achieved and the raw materials are more effectively utilized.

In the technical solution of the present invention, by controlling the reaction process and continuously carrying out repeated treatments and reactions, the yield of 3,4-dichloro-hexafluoro-1-butene can be increased to more than 47%, while the yield of 1,2-dichloro The hexafluorocyclobutane yield can reach more than 49%, which greatly improves the adequacy of the reaction, the total product yield is significantly improved, and the raw material utilization rate is also significantly improved.

In addition, the present invention achieves effective separation of two intermediate products through high-pressure water bath fractionation. The intermediate 1,2-dichlorohexafluorocyclobutane is separately obtained after zinc-catalyzed dechlorination and hydrogen iodide catalytic hydrogenation for ring-opening. Hexafluorobutane is obtained. Hexafluorobutane is condensed and recovered and mixed with the collected residual liquid 3,4-dichloro-hexafluoro-1-butene. It undergoes an addition reaction with chlorine water under photocatalysis to obtain important precursor. The product 1,2,3,4-tetrachlorohexafluorobutane (CF ₂ Cl-CFCl-CFCl-CF ₂ C), the resulting 1,2,3,4-tetrachlorohexafluorobutane is refluxed under zinc catalysis The reaction yields the target product hexafluorobutadiene.

In the process of the above scheme, the most important thing is the temperature and pressure increase reaction in step 1), which is the key to achieving high product yield. Its participation in the thermal polymerization reaction after slow boiling and gasification at room temperature will lead to product recovery. The rate dropped significantly to a total yield of less than 60%, and the high-pressure water bath fractionation in step 2) is the key to improving product purity and ensuring product yield, and can very effectively separate two similar boiling point substances, namely 1,2-bis Chlorohexafluorocyclobutane and 3,4-dichloro-hexafluoro-1-butene to avoid side reactions that produce impurities or reduce target products. Step 3) is a conventional conversion reaction process, but in step 4), by jointly processing the two components in one step, the construction period can be greatly shortened, the production cost can be reduced, the production efficiency and production cost-effectiveness of the actual enterprise can be improved, and the invention has improved The industrial value and practical value of technical solutions. In addition, hexafluorocyclobutene produced and participated in the preparation process is the main impurity component produced in the production process of the present invention and the prior art. It usually needs to be removed through a complex separation process, but the present invention uses a porous solid catalyst to make it After the isomeric transformation occurs, it is converted into the target product hexafluorobutadiene of the present invention, which reduces the filtration and impurity removal steps and greatly improves the yield and purity of the product of the present invention, and the porous solid catalyst can remove water vapor and other impurities.

beneficial effects

The beneficial effects of the present invention are: 1) Through the preparation process of the present invention, the yield of hexafluorobutadiene in the existing industrial production and preparation process of chlorotrifluoroethylene as a low-cost raw material can be increased from about 40% to at least 85%. %, greatly improving the preparation effect of hexafluorobutadiene; 2) The purity of the obtained product is high, basically reaching more than 99.99%, meeting the existing industrial use requirements; 3) The scheme is suitable for industrial large-scale production and preparation.

Embodiments of the invention

The present invention will be further described in detail below in conjunction with specific embodiments. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention mentioned in the following description are generally only some embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of the present invention.

Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or those available to those skilled in the art. Unless otherwise specified, the methods used in the examples of the present invention are all methods mastered by those skilled in the art.

Unless otherwise specified, the reaction kettle used in the examples of the present invention is a high-pressure polymerization reaction kettle equipped with a condensation reflux device purchased from Weihai Automation.

Embodiment 1: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, first raising the pressure to 0.75 MPa, and then raising the temperature to 45°C. After the vinyl chloride is slowly vaporized, it is directed into a copper tube preheated to 575 ℃ for thermal polymerization reaction. During the diversion, the flow rate is controlled so that the gasified chlorotrifluoroethylene passes through the heat pipe within 12 s, and the temperature is cooled to ≤ 40 ℃ after the reaction. Condensate and recover the thermal polymerization product and mix the thermal polymerization product into the raw materials and place it at the bottom of the reactor. Stop the reaction when the material at the bottom of the reactor no longer boils. Release the pressure and maintain constant temperature for 10 minutes, then cool to room temperature and recover the precursor; 2) Place the precursor in a container to increase the pressure to 0.6 MPa, then place the container in a boiling water bath to obtain the low-boiling point intermediate produced by gasification of the precursor. When the volume of the precursor no longer decreases, the remaining liquid in the container is recovered for later use; 3) The intermediate is cooled to room temperature, added to 1.2 times the volume of ethanol, and 0.05 times the mass of elemental zinc is added as a catalyst. After the reflux reaction at 75°C, the gas product is collected and the gas product is mixed with hydrogen iodide gas at a volume ratio of 1: 1 and placed in a ring-opening reaction at 290°C for 24 hours, then condensed in an ice-water bath and recovered to obtain the condensate; 4) Mix the condensate and the remaining liquid in step 2) into a mixed liquid, add excess saturated chlorine water, and Carry out UV illumination for 24 hours under the catalysis of chlorine water to perform a chlorination addition reaction to obtain a pre-product solution. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the volume of elemental zinc as a catalyst, and heat to The reaction was carried out under reflux at 145°C for 8 hours, during which impurities were removed by condensation and reflux, and then the gas product was collected at a constant temperature of 65°C. The gas product passed through a copper tube filled with porous solid catalyst within 12 s. The porous solid catalyst in the copper tube was composed of activated carbon, Composed of potassium fluoride and calcium fluoride, the molar ratio of potassium fluoride and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 670°C , and then the target product hexafluorobutadiene is obtained.

Embodiment 2: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, first raising the pressure to 0.6 MPa, and then raising the temperature to 42°C. After the vinyl chloride is slowly vaporized, it is directed into a copper tube preheated to 580 ℃ for thermal polymerization reaction. The flow rate is controlled during the diversion so that the gasified chlorotrifluoroethylene passes through the heat pipe within 12 s. After the reaction, the temperature is cooled to ≤ 40 ℃. Condensate and recover the thermal polymerization product and mix the thermal polymerization product into the raw materials and place it at the bottom of the reactor. Stop the reaction when the material at the bottom of the reactor no longer boils. Release the pressure and maintain constant temperature for 10 minutes, then cool to room temperature and recover the precursor; 2) Place the precursor in a container to increase the pressure to 0.7 MPa, and then place the container in a boiling water bath to obtain the low-boiling point intermediate produced by gasification of the precursor. When the volume of the precursor no longer decreases, the remaining liquid in the container is recovered for later use; 3) The intermediate is cooled to room temperature, added to 1.2 times the volume of ethanol, and 0.05 times the mass of elemental zinc is added as a catalyst. After the reflux reaction at 75°C, the gas product is collected and the gas product is mixed with hydrogen iodide gas at a volume ratio of 1: 1 and placed in a ring-opening reaction at 295°C for 23 hours, then condensed in an ice-water bath and recovered to obtain the condensate; 4) Mix the condensate and the remaining liquid in step 2) into a mixed liquid, add excess saturated chlorine water, and Carry out UV illumination for 24 hours under the catalysis of chlorine water to perform a chlorination addition reaction to obtain a pre-product solution. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the volume of elemental zinc as a catalyst, and heat to The reaction was carried out under reflux at 150°C for 6 hours, during which the impurities were removed by condensation and reflux, and then the gas product was collected at a constant temperature of 65°C. The gas product passed through a copper tube filled with porous solid catalyst within 14 s. The porous solid catalyst in the copper tube was composed of activated carbon, Composed of potassium fluoride and calcium fluoride, the molar ratio of potassium fluoride and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 670°C , and then the target product hexafluorobutadiene is obtained.

Embodiment 3: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, first raising the pressure to 0.75 MPa, and then raising the temperature to 42°C. After the vinyl chloride is slowly vaporized, it is directed into a copper tube preheated to 580 ℃ for thermal polymerization reaction. During the diversion, the flow rate is controlled so that the gasified chlorotrifluoroethylene passes through the heat pipe within 10 s. After the reaction, the temperature is cooled to ≤ 40 ℃. Condensate and recover the thermal polymerization product and mix the thermal polymerization product into the raw materials and place it at the bottom of the reactor. Stop the reaction when the material at the bottom of the reactor no longer boils. Release the pressure and maintain constant temperature for 10 minutes, then cool to room temperature and recover the precursor; 2) Place the precursor in a container to increase the pressure to 0.6 MPa, then place the container in a boiling water bath to obtain the low-boiling point intermediate produced by gasification of the precursor. When the volume of the precursor no longer decreases, the remaining liquid in the container is recovered for later use; 3) The intermediate is cooled to room temperature, added to 1.2 times the volume of ethanol, and 0.05 times the mass of elemental zinc is added as a catalyst. After the reflux reaction at 75°C, the gas product is collected and the gas product is mixed with hydrogen iodide gas at a volume ratio of 1: 1 and placed in a ring-opening reaction at 290°C for 24 hours, then condensed in an ice-water bath and recovered to obtain the condensate; 4) Mix the condensate and the remaining liquid in step 2) into a mixed liquid, add excess saturated chlorine water, and Carry out UV illumination for 24 hours under the catalysis of chlorine water to perform a chlorination addition reaction to obtain a pre-product solution. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the volume of elemental zinc as a catalyst, and heat to The reaction was carried out under reflux at 145°C for 8 hours, during which impurities were removed by condensation and reflux, and then the gas product was collected at a constant temperature of 65°C. The gas product passed through a copper tube filled with porous solid catalyst within 12 s. The porous solid catalyst in the copper tube was composed of activated carbon, Composed of potassium fluoride and calcium fluoride, the molar ratio of potassium fluoride and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 670°C , and then the target product hexafluorobutadiene was obtained.

Embodiment 4: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, first raising the pressure to 0.6 MPa, and then raising the temperature to 42°C. After the vinyl chloride is slowly vaporized, it is directed into a copper tube preheated to 580 ℃ for thermal polymerization reaction. The flow rate is controlled during the diversion so that the gasified chlorotrifluoroethylene passes through the heat pipe within 12 s. After the reaction, the temperature is cooled to ≤ 40 ℃. Condensate and recover the thermal polymerization product and mix the thermal polymerization product into the raw materials and place it at the bottom of the reactor. Stop the reaction when the material at the bottom of the reactor no longer boils. Release the pressure and maintain constant temperature for 10 minutes, then cool to room temperature and recover the precursor; 2) Place the precursor in a container to increase the pressure to 0.7 MPa, and then place the container in a boiling water bath to obtain the low-boiling point intermediate produced by gasification of the precursor. When the volume of the precursor no longer decreases, the remaining liquid in the container is recovered for later use; 3) The intermediate is cooled to room temperature, added to 1.2 times the volume of ethanol, and 0.05 times the mass of elemental zinc is added as a catalyst. After the reflux reaction at 75°C, the gas product is collected and the gas product is mixed with hydrogen iodide gas at a volume ratio of 1: 1 and placed in a ring-opening reaction at 285°C for 25 hours, then condensed in an ice-water bath and recovered to obtain the condensate; 4) Mix the condensate and the residual liquid described in step 2) into a mixed liquid, add excess saturated chlorine water, and Carry out UV illumination for 24 hours under the catalysis of chlorine water to perform a chlorination addition reaction to obtain a pre-product solution. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the volume of elemental zinc as a catalyst, and heat to The reaction was carried out under reflux at 145°C for 8 hours and impurities were removed by condensation and reflux during this process. The gas product was then collected at a constant temperature of 65°C. The gas product passed through a copper tube filled with porous solid catalyst within 14 s. The porous solid catalyst in the copper tube was composed of activated carbon, Composed of potassium fluoride and calcium fluoride, the molar ratio of potassium fluoride and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 665°C , and then the target product hexafluorobutadiene is obtained.

Comparative Example 1: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, first raising the pressure to 0.75 MPa, and then raising the temperature to 45°C. After the vinyl chloride is slowly vaporized, it is directed into a copper tube preheated to 575 ℃ for thermal polymerization reaction. During the diversion, the flow rate is controlled so that the gasified chlorotrifluoroethylene passes through the heat pipe within 12 s, and the temperature is cooled to ≤ 40 ℃ after the reaction. Condensate and recover the thermal polymerization product and mix the thermal polymerization product into the raw materials and place it at the bottom of the reactor. Stop the reaction when the material at the bottom of the reactor no longer boils. Release the pressure and cool to room temperature to recover the precursor; 2) Place the precursor at the bottom of the reactor. The pressure in the container is increased to 0.6 MPa, and then the container is placed in a boiling water bath to obtain the low-boiling point intermediate produced by the gasification of the precursor. When the volume of the precursor no longer decreases, the remaining liquid in the container is recovered for later use; 3) Cool the intermediate to room temperature. , add it to 1.2 times the volume of ethanol, and add 0.05 times the mass of elemental zinc as a catalyst. After the reflux reaction at 75°C, collect the gas products and mix the gas products with hydrogen iodide gas in a volume ratio of 1:1. After ring-opening reaction at 290°C for 24 hours, the condensate was recovered by condensation in an ice-water bath; 4) Mix the condensate and the residual liquid described in step 2) into a mixed liquid, add excess saturated chlorine water, and proceed under the catalysis of chlorine water Perform chlorination addition reaction under UV illumination for 24 hours to obtain a pre-product solution. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the elemental zinc as a catalyst, and heat to 145°C for reflux reaction 8 h and condensed and refluxed to remove impurities during this process, and then the gas products were collected at a constant temperature of 65°C. The gas products passed through a copper tube filled with porous solid catalyst within 12 s. The porous solid catalyst in the copper tube was composed of activated carbon, potassium fluoride and fluorine. Composed of calcium fluoride, the molar ratio of potassium fluoride and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 670°C, and then the target product is obtained Hexafluorobutadiene.

Comparative Example 2: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, raising the temperature to 45°C, slowly vaporizing the chlorotrifluoroethylene and then guiding it into The thermal polymerization reaction is carried out in a copper tube preheated to 575°C. The flow rate is controlled during diversion so that the gasified chlorotrifluoroethylene passes through the heat pipe within 12 s. After the reaction, the temperature is cooled to ≤40°C, the thermal polymerization product is condensed, recovered and the heat The polymer product is mixed into the raw materials and placed at the bottom of the reaction kettle. The reaction is terminated when the material at the bottom of the reaction kettle no longer boils. Release the pressure and maintain a constant temperature for 10 minutes, then cool to room temperature and recover the precursor; 2) Place the precursor in a container and raise it. Pressure to 0.6 MPa, and then place the container in a boiling water bath to obtain the low-boiling point intermediate produced by gasification of the precursor. When the volume of the precursor no longer decreases, recover the remaining liquid in the container for later use; 3) Cool the intermediate to room temperature, add to into 1.2 times the volume of ethanol, and add 0.05 times the mass of elemental zinc as a catalyst. After the reflux reaction at 75°C, collect the gas products and mix the gas products with hydrogen iodide gas in a volume ratio of 1:1 and place at 290°C. After the ring-opening reaction under the conditions for 24 hours, the condensate is recovered by condensation in an ice-water bath; 4) Mix the condensate and the residual liquid described in step 2) into a mixed liquid, add excess saturated chlorine water, and perform UV illumination under the catalysis of chlorine water for 24 h to perform a chlorination addition reaction to obtain a pre-product solution. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the volume of elemental zinc as a catalyst. Heat to 145°C and reflux for 8 hours. During this process, impurities are removed by condensation and reflux, and then the gas products are collected at a constant temperature of 65°C. The gas products pass through a copper tube filled with porous solid catalyst within 12 seconds. The porous solid catalyst in the copper tube is composed of activated carbon, potassium fluoride and calcium fluoride. , the molar ratio of potassium fluoride and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 670°C, and then the target product hexafluorobutane is obtained Diene.

Comparative Example 3: A method for preparing hexafluorobutadiene. The method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reaction kettle, first raising the pressure to 0.75 MPa, and then raising the temperature to 45°C. After the vinyl chloride is slowly vaporized, it is directed into a copper tube preheated to 575 ℃ for thermal polymerization reaction. During the diversion, the flow rate is controlled so that the gasified chlorotrifluoroethylene passes through the heat pipe within 12 s, and the temperature is cooled to ≤ 40 ℃ after the reaction. Condensate and recover the thermal polymerization product and mix the thermal polymerization product into the raw materials and place it at the bottom of the reactor. Stop the reaction when the material at the bottom of the reactor no longer boils. Release the pressure and maintain constant temperature for 10 minutes, then cool to room temperature and recover the precursor; 2) Under normal pressure conditions, the low-boiling point intermediate produced by gasification of the precursor is obtained by splitting at a constant temperature of 60°C. When the volume of the precursor is no longer reduced, the remaining liquid is recovered in the container for later use; 3) Cool the intermediate to room temperature and add 1.2 times the volume of the intermediate. In ethanol, add 0.05 times the mass of elemental zinc as a catalyst, collect the gas product after the reflux reaction at 75°C, and mix the gas product and hydrogen iodide gas in a volume ratio of 1:1 and place it at 290°C for ring-opening reaction. After 24 hours, the condensate is recovered by condensation in an ice-water bath; 4) Mix the condensate and the residual liquid described in step 2) into a mixed liquid, add excess saturated chlorine water, and perform UV illumination under the catalysis of chlorine water for 24 hours to perform chlorination addition. The pre-product solution was obtained from the complete reaction. Add the pre-product solution to 1.2 times the volume of butyl carbitol, and add 0.05 times the volume of elemental zinc as a catalyst. Heat to 145°C for reflux reaction for 8 hours and condense to reflux during the process. Impurities are removed, and then the gas product is collected at a constant temperature of 65°C. The gas product passes through a copper tube filled with a porous solid catalyst within 12 seconds. The porous solid catalyst in the copper tube is composed of activated carbon, potassium fluoride and calcium fluoride. The fluoride The molar ratio of potassium and calcium fluoride is 1:1, the activated carbon accounts for 65 wt% of the total mass of the porous solid catalyst, and the porous solid catalyst is preheated to 670°C, and then the target product hexafluorobutadiene is obtained.

The purity and product yield of the hexafluorobutadiene products prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were detected and characterized. The calculated yield of the product of Example 1 is 91.2%, and the product purity is more than 99.99% VOL after gas chromatography characterization. The calculated yield of the product of Example 2 is 88.7%, and the product purity is more than 99.99% VOL after gas chromatography characterization. Implementation The calculated yield of the product in Example 3 is 90.2%, and the product purity is more than 99.99% VOL after gas chromatography characterization. The calculated yield of the product in Example 4 is 89.6%, and the product purity is more than 99.99% VOL after gas chromatography characterization. It can be seen that the product yields obtained by the embodiments of the present invention can reach more than 88%, and after the factory's half-month trial production (2022/5/1 ~ 2022/5/15), the industrial production yield will decrease slightly. , but can still be maintained above 85%, and the product purity can be maintained above 99.99%VOL. In Comparative Example 1, the calculated product yield can still remain high, reaching about 88.9% VOL, but the purity drops to about 98.91% VOL. This is mainly because during the constant temperature process after the reaction in step 1), the product can be volatilized and removed Some impurities are difficult to remove in subsequent processes. However, after omitting the constant temperature step in Comparative Example 1, the solution quickly cooled down and these impurities were retained. And during factory trial production (2022/4/28 ~ 2022/4/30), the product purity dropped to approximately 96.13% VOL, which resulted in a very significant decrease and was not conducive to industrial mass production. In Comparative Example 2, the rapid thermal polymerization reaction was directly carried out under non-high pressure conditions, which produced a large amount of impurities, and the reaction adequacy and selectivity were significantly reduced. The calculated yield of the final product was only about 69.4%, and the product purity remained relatively low. High, can reach above 99%VOL. However, the product yield has dropped significantly, and the costs and benefits of batch and large-scale production in factories have dropped significantly. In Comparative Example 3, atmospheric pressure fractionation is used, and the normal pressure boiling points of the two components are about 59 ℃ and 63.5 ℃ respectively. The fractionation effect of controlling 60 ℃ under normal pressure is not good, so the actual product yield drops to about 81.4% VOL, and the purity dropped to about 98.69%. Moreover, during the trial production process (2022/4/25 ~ 2022/4/26), the product yield was only about 72.9%VOL, a huge drop.

Therefore, it can also be seen from the above comparative experiments that for the technical solution of the present invention, fine adjustments of various parameters and processes will have a huge impact on the yield and purity of the product. Therefore, strictly controlling the preparation process parameters is the key to achieving the technical effects of the present invention.

Claims

A method for preparing hexafluorobutadiene, which is characterized in that the method includes: 1) placing the liquid chlorotrifluoroethylene raw material at the bottom of the reactor, raising the temperature and pressure, and then flowing it into the reaction vessel for thermal polymerization reaction and then condensation recovery The thermal polymerization product is mixed into the raw material until the raw material and/or the thermal polymerization product no longer boils, then the recovery is terminated to obtain the precursor; 2) High-pressure water bath fractionation of the precursor and obtains a low boiling point intermediate, to the volume of the precursor Do not recover the remaining liquid after reduction for later use; 3) Add the intermediate to ethanol, and add elemental zinc as a catalyst, collect the gas product after the reflux reaction, mix the gas product with hydrogen iodide gas, perform a high-temperature ring-opening reaction, and then condense and recover to obtain the condensation liquid; 4) Mix the condensate with the residual liquid described in step 2), react with chlorine water under photocatalysis, and then add it to butyl carbitol, and add elemental zinc as a catalyst, heat the reaction and condense and reflux to remove impurities, After the gas product passes through a high-temperature porous solid catalyst, hexafluorobutadiene is obtained.
A method for preparing hexafluorobutadiene according to claim 1, characterized in that the temperature and pressure increase control conditions in step 1) are: first control the pressure in the reaction kettle to 0.6~0.8 MPa and then raise the temperature to 42~0.8 MPa. 45℃.
The method for preparing hexafluorobutadiene according to claim 1 or 2, characterized in that the reaction temperature of the thermal polymerization reaction in step 1) is 575-580°C, and the reaction time is 10-12 s.
A method for preparing hexafluorobutadiene according to claim 1, characterized in that the high-pressure water bath fractionation in step 2) specifically includes: placing the precursor in a boiling water bath across water, and controlling the container in which the precursor is located. The pressure is 0.5~0.7 MPa.
A method for preparing hexafluorobutadiene according to claim 1, characterized in that, in step 3), the gas product is mixed with hydrogen iodide gas and subjected to a high-temperature catalytic reaction at 285 to 295°C for 22 to 26 hours. .
The preparation method of hexafluorobutadiene according to claim 1, characterized in that the illumination reaction in step 4) is carried out for ≥24 h; the illumination reaction is carried out under UV light irradiation.
A method for preparing hexafluorobutadiene according to claim 1, characterized in that the heating reaction control temperature in step 4) is 145-150°C, and the reaction time is 6-8 h.
A method for preparing hexafluorobutadiene according to claim 1, characterized in that the porous solid catalyst is composed of activated carbon, potassium fluoride and calcium fluoride; the potassium fluoride and calcium fluoride are The molar ratio is 1: (0.95-1.05), and the activated carbon accounts for 50-65 wt% of the total mass of the porous solid catalyst.
A method for preparing hexafluorobutadiene according to claim 8, characterized in that activated carbon, potassium fluoride and calcium fluoride in the porous solid catalyst are mixed and then filled in a tubular container to control gas products The flow rate allows the gas product to pass through the tubular container within 12 to 14 seconds.
The method for preparing hexafluorobutadiene according to claim 1, 8 or 9, characterized in that the porous solid catalyst in step 4) is preheated to 665-670°C.