Method for industrially and continuously synthesizing octafluorocyclobutane

Abstract

The invention belongs to the technical field of chemical production, and particularly relates to a method for industrially and continuously synthesizing octafluorocyclobutane. The preparation method specifically comprises the following steps: S1, adding 1, 1, 2, 2, 3, 4-hexafluoro-3, 4-dichlorocyclobutane, alkali metal fluoride and an organic aprotic solvent into a reaction kettle, heating and stirring to carry out fluorine-chlorine exchange reaction to obtain a crude product octafluorocyclobutane; and S2, carrying out rectification and adsorption two-stage impurity removal on the crude octafluorocyclobutane, and finally collecting the refined octafluorocyclobutane. According to the method provided by the invention, the product yield can reach 70.8%, and the product content is gt; the water content is 1t; 0.1%, chloride ion detection result; and 0.1%. According to the octafluorocyclobutane preparation method, the production process is free of pollution, the prepared octafluorocyclobutane is high in selectivity, equipment is simple, continuity can be achieved, the yield is high, raw materials are cheap, the production cost is reduced, the product purity is high, and the octafluorocyclobutane preparation method is suitable for industrial production.

Description

Technical Field

[0001] This application belongs to the technical field of chemical production, and particularly relates to a method for industrially continuously synthesizing octafluorocyclobutane. Background Art

[0002] Octafluorocyclobutane (also known as perfluorocyclobutane) is a special fluorinated gas developed by DuPont in the United States in the 1950s. At room temperature, octafluorocyclobutane is a colorless, odorless, and non-flammable gas. Since octafluorocyclobutane is non-toxic and has an ODP (ozone depletion potential) value of zero, it is often used as a mixed refrigerant instead of chlorofluorocarbons (CFCs) to reduce the damage to the atmospheric ozone layer. The greenhouse effect index of octafluorocyclobutane is 1 / 3 of that of sulfur hexafluoride, and the insulation strength of octafluorocyclobutane gas under a uniform electric field is 1.11 - 1.80 times that of sulfur hexafluoride gas. Therefore, octafluorocyclobutane gas is also used as an insulating medium in high-voltage electrical equipment instead of sulfur hexafluoride. In recent years, it has been widely used as a refrigerant to replace the banned chlorofluorocarbon compounds. In addition, it is also commonly used in gas insulating media, solvents, sprays, foaming agents, large-scale circuit etchants, heat pump working fluids, and raw materials for producing C2F4 and C3F6 monomers, etc. High-purity octafluorocyclobutane is used in ultra-large-scale integrated circuit etchants and cleaning agents.

[0003] Regarding the preparation methods of octafluorocyclobutane, the currently known and publicly reported synthesis methods mainly include the following several:

[0004] (1) Tetrafluoroethylene dimerization method: This method uses tetrafluoroethylene as the raw material, adopts a tubular or autoclave reactor, and uses dimethyl sulfate, ethylene, ammonia water, or terpene as a polymerization inhibitor, and polymerizes at 400 - 750 °C and 0.005 - 0.1 MPa. The reaction equation is as follows:

[0005]

[0006] However, highly toxic perfluoroisobutene will be generated during the preparation of octafluorocyclobutane by the tetrafluoroethylene dimerization method. It is reported in patents and literature that the generation of perfluoroisobutene can be inhibited by reducing the contact time. However, trace amounts of perfluoroisobutene will also increase the difficulty of subsequent purification processes.

[0007] (2) Electrochemical fluorination method: The specific conditions are as follows: 285 mL of anhydrous hydrogen fluoride, 0.15 g of sodium fluoride, and 9.12 g of 1,1,2,2-tetrafluorocyclobutane are added to the electrochemical fluorination cell. The applied voltage is 4.8 V, the reference electrode is Cu / CuF2, the reaction temperature is about 18 °C, and the current efficiency is about 97%. Under these conditions, the selectivity of octafluorocyclobutane can reach up to 66%, and the yield is 62%. However, the content of perfluoroisobutene is relatively low during the preparation of octafluorocyclobutane by this method, which has a certain degree of safety. In addition, when using the electrochemical fluorination method, the electrolysis process is easy to control, and the reaction conditions are relatively mild. However, the electrolysis process will lead to an increase in the types of by-products, posing challenges to the subsequent purification process.

[0008] (3) Fluoride pyrolysis method: Octafluorocyclobutane is mainly prepared by pyrolyzing dichlorotetrafluoroethane. The reaction equation is shown in Equation (3). US Patent US1962183400 discloses a method for preparing octafluorocyclobutane by pyrolyzing dichlorotetrafluoroethane. 8.9 g of dichlorotetrafluoroethane is vaporized and passed through a pyrolysis tube equipped with a nickel wire mesh at a flow rate of 1.6 L / h, and pyrolysis is carried out at 590 °C, only producing 2.0 g of octafluorocyclobutane and 2.6 g of tetrafluoroethylene. Although the types of by-products generated by this method are few, the yield of octafluorocyclobutane is relatively low. Therefore, this method is not suitable for large-scale production.

[0009] In addition, Chinese Patent with Publication No. CN114956950B discloses a method for synthesizing octafluorocyclobutane by fluorine-chlorine exchange reaction. Hydrogen fluoride gas and 1,1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane gas are used to prepare octafluorocyclobutane in a self-made catalyst (activated carbon-supported Cr2O3-NiO catalyst). However, as the reaction time prolongs, the by-products of the reaction may adhere to the surface of the catalyst, affecting the catalytic effect, and the catalyst needs to be frequently replaced, which may increase the production cost in industrial continuous production.

[0010] In summary, there are many methods for preparing octafluorocyclobutane, but there are still some problems, such as the by-products being toxic and having many types, the product purity and yield being low, the cost being high, and it not being suitable for large-scale industrial production, etc. Therefore, there is an urgent need to propose a method for industrial continuous synthesis of octafluorocyclobutane to solve and alleviate the existing problems in the current production of octafluorocyclobutane. Summary of the Invention

[0011] Aiming at some problems existing in the existing technology for preparing octafluorocyclobutane, such as the by-products being toxic and having many types, the product purity and yield being low, the cost being high, and it not being suitable for large-scale industrial production, etc., the present application provides a method for octafluorocyclobutane with high reaction selectivity, high reaction efficiency and suitable for industrial continuous production.

[0012] The technical solution of the present application is as follows:

[0013] A method for industrially continuously synthesizing octafluorocyclobutane, comprising the following steps:

[0014] Step S1. Add 1,1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane, alkali metal fluoride and organic aprotic solvent into a reaction kettle, heat and stir to carry out a fluorine-chlorine exchange reaction to obtain crude octafluorocyclobutane;

[0015] Step S2. Purify the crude octafluorocyclobutane through two stages of rectification and adsorption, and finally collect the refined octafluorocyclobutane.

[0016] Preferably, the alkali metal fluoride is NaF or KF.

[0017] Preferably, the organic aprotic solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, sulfolane, and diethylene glycol dimethyl ether.

[0018] Preferably, the reaction temperature is 140 - 180 °C.

[0019] Preferably, the initial feeding molar ratio of 1,1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane, alkali metal fluoride and organic aprotic solvent is 1:(2 - 4):(7 - 10).

[0020] Preferably, the pressure of the rectification is 0.1 - 0.3 MPa, and the temperature is -5 °C - 20 °C.

[0021] Preferably, the adsorbent selected for adsorption purification is one or a mixture of adsorbents such as X-type molecular sieve, A-type molecular sieve, activated carbon or silica gel, the adsorption temperature is 10 - 40 °C, and the adsorption residence time is 40 - 80 s.

[0022] Preferably, the temperature for collecting the refined octafluorocyclobutane is -20 °C - -10 °C.

[0023] Preferably, the light components removed by the rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of the rectification is lower than 0.1 MPa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.15 - 0.2 Mpa.

[0024] Advantages of this application:

[0025] (1) This application uses 1,1,2,2,3,4 - hexafluoro - 3,4 - dichlorocyclobutane, alkali metal fluoride, and organic aprotic solvent as raw materials. Due to the strong electrostatic interaction between fluoride ions in potassium fluoride (KF) and potassium ions (K+), fluoride ions are easily wrapped by solvent molecules through hydrogen bonds in protic solvents, resulting in a decrease in nucleophilicity. In aprotic solvents, the interaction between fluoride ions and cations weakens, forming a situation that can significantly improve the reactivity of fluoride ions (F-), and the nucleophilicity is greatly enhanced. Through a fluoro - chloro exchange reaction in sequence, crude octafluorocyclobutane is obtained. The obtained product is subjected to rectification to remove substances such as air, carbon monoxide, carbon dioxide, and light components with similar boiling points, and then moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. in octafluorocyclobutane are removed through an adsorbent to obtain octafluorocyclobutane with high yield and high content. The product yield can reach 70.8%, the product content > 99%, the water content < 0.1%, and the chloride ion detection < 0.1%.

[0026] (2) The production process of this application is pollution - free. The prepared octafluorocyclobutane has high selectivity, simple equipment, can achieve continuous production, high yield, and cheap raw materials, which is conducive to reducing production costs. The product has high purity, and it is a method for preparing octafluorocyclobutane suitable for industrial production. Detailed implementation mode

[0027] To further elaborate on the technical means and effects adopted by this application to achieve the predetermined invention purpose, the following combines preferred embodiments to detail the specific implementation mode, structure, characteristics, and their effects of this application as follows.

[0028] Example 1

[0029] This example provides a method for industrial continuous synthesis of octafluorocyclobutane, which is as follows:

[0030] Step S1. Fluoro - chloro exchange reaction

[0031] Mix NaF, dimethyl sulfoxide, and 1,2,2,3,4 - hexafluoro - 3,4 - dichlorocyclobutane with a purity of 95% in a molar ratio of 2:7:1, add them to a reaction kettle, heat up to 140 °C for reaction, continuously stir during the reaction for 5 hours to obtain crude octafluorocyclobutane.

[0032] Step S2. Two - stage rectification for impurity removal

[0033] Light - component removal in the rectification column: In the rectification process, liquid nitrogen is used as the cold source. The feed is about 2 / 3 of the tower kettle, maintaining the pressure at 0.1 - 0.2 MPa and the temperature at - 5 °C - 0 °C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide, and impurities with similar boiling points to octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reaches more than 99.95%, the gaseous octafluorocyclobutane enters the secondary adsorption;

[0034] Adsorption and impurity removal: The gas after rectification enters the adsorption equipment to adsorb moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. The octafluorocyclobutane after rectification is introduced into the adsorption tower filled with adsorbent. The X-type molecular sieve adsorbent is filled inside the adsorption tower. The adsorption temperature is 10-15°C, and the residence time is 60 s. The high-quality octafluorocyclobutane product with a purity of 99.99% is obtained by the method of purifying while reacting. Finally, it is received by a low-temperature cooling device, and the cooling temperature is -20 to -17°C.

[0035] Continuous reaction: The light components removed by rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification is lower than 0.1 Mpa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.15 Mpa.

[0036] Example 2

[0037] KF, dimethyl sulfoxide and 1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane with a purity of 95% are reacted at a molar ratio of 3:8:1 by heating to 140°C. The reaction process is continuously stirred for 5 hours to obtain the crude octafluorocyclobutane.

[0038] Step S2. Two-stage rectification for impurity removal

[0039] Light component removal in the rectification tower: Liquid nitrogen is used as the cold source in the rectification process. The feed is about 2 / 3 of the tower kettle, and the pressure is maintained at 0.1-0.2 MPa and the temperature is at -5°C to 0°C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide and impurities with boiling points close to that of octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reaches more than 99.95%, the gaseous octafluorocyclobutane enters the secondary adsorption.

[0040] Adsorption and impurity removal: The gas after rectification enters the adsorption equipment to adsorb moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. The octafluorocyclobutane after rectification is introduced into the adsorption tower filled with adsorbent. The A-type molecular sieve is filled inside the adsorption tower as the adsorbent. The adsorption temperature is 10-15°C, and the residence time is 80 s. The high-quality octafluorocyclobutane product with a purity of 99.99% is obtained by the method of purifying while reacting. Finally, it is received by a low-temperature cooling device, and the cooling temperature is -20 to -17°C.

[0041] Continuous reaction: The light components removed by rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification is lower than 0.1 Mpa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.2 Mpa.

[0042] Example 3

[0043] NaF, N,N-dimethylformamide and 1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane with a purity of 95% are added to the reaction kettle in a molar ratio of 4:9:1, and the temperature is raised to 170 °C for reaction. During the reaction process, continuous stirring is carried out for 5 hours to obtain a crude product of octafluorocyclobutane.

[0044] Step S2. Two-stage rectification for impurity removal

[0045] Light component removal in the rectification column: In the rectification process, liquid nitrogen is used as the cold source. The feed is about 2 / 3 of the column kettle, and the pressure is maintained at 0.1 - 0.2 MPa and the temperature at 0 °C - 5 °C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide and impurities with boiling points close to that of octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reaches over 99.95%, the gaseous octafluorocyclobutane enters the secondary adsorption.

[0046] Adsorption for impurity removal: The gas after rectification enters the adsorption equipment to adsorb moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. The octafluorocyclobutane after rectification is passed into the adsorption tower filled with adsorbent. The inside of the adsorption tower is filled with activated carbon as the adsorbent. The adsorption temperature is 15 - 20 °C, and the residence time is 50 s. The high-purity octafluorocyclobutane product with a purity of 99.99% is obtained by the method of reacting and purifying simultaneously. Finally, it is received by a low-temperature cooling device, and the cooling temperature is -17 °C - -14 °C.

[0047] Continuous reaction: The light components removed by rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification is lower than 0.1 Mpa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.18 Mpa.

[0048] Example 4

[0049] KF, N,N-dimethylformamide and 1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane with a purity of 95% are added to the reaction kettle in a molar ratio of 3:10:1, and the temperature is raised to 170 °C for reaction. During the reaction process, continuous stirring is carried out for 5 hours to obtain a crude product of octafluorocyclobutane.

[0050] Step S2. Two-stage rectification for impurity removal

[0051] Light component removal in the rectification column: In the rectification process, liquid nitrogen is used as the cold source. The feed is about 2 / 3 of the column kettle, and the pressure is maintained at 0.2 - 0.3 MPa and the temperature at 5 °C - 10 °C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide and impurities with boiling points close to that of octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reaches over 99.95%, the gaseous octafluorocyclobutane enters the secondary adsorption.

[0052] Adsorption and impurity removal: The gas after rectification enters the adsorption equipment to adsorb moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. The octafluorocyclobutane after rectification is introduced into the adsorption tower filled with adsorbent. The inside of the adsorption tower is filled with silica gel as the adsorbent, the adsorption temperature is 15 - 20 °C, the residence time is 70 s, and the refined octafluorocyclobutane with a purity of 99.99% is obtained by the method of reacting and purifying simultaneously. Finally, it is received by a low-temperature cooling device, and the cooling temperature is -17 - -14 °C.

[0053] Continuous reaction: The light components removed by rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification is lower than 0.1 Mpa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.2 Mpa.

[0054] Example 5

[0055] NaF, sulfolane and 1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane with a purity of 95% are added to the reaction kettle in a molar ratio of 4:8:1, and the temperature is raised to 160 °C. During the reaction process, continuous stirring is carried out for 5 hours to obtain the crude octafluorocyclobutane.

[0056] Step S2. Two-stage rectification for impurity removal

[0057] Light component removal in the rectification tower: Liquid nitrogen is used as the cold source in the rectification process. The feed is about 2 / 3 of the tower kettle, the pressure is maintained at 0.2 - 0.3 MPa, and the temperature is at 10 °C - 15 °C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide and impurities with boiling points close to that of octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reaches over 99.95%, the gaseous octafluorocyclobutane enters the secondary adsorption.

[0058] Adsorption and impurity removal: The gas after rectification enters the adsorption equipment to adsorb moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. The octafluorocyclobutane after rectification is introduced into the adsorption tower filled with adsorbent. The inside of the adsorption tower is filled with a mixed adsorbent of X-type molecular sieve and silica gel, the adsorption temperature is 20 - 25 °C, the residence time is 60 s, and the refined octafluorocyclobutane with a purity of 99.99% is obtained by the method of reacting and purifying simultaneously. Finally, it is received by a low-temperature cooling device, and the cooling temperature is -17 - -14 °C.

[0059] Continuous reaction: The light components removed by rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification is lower than 0.1 Mpa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.15 Mpa.

[0060] Example 6

[0061] KF, sulfolane, and 1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane with a purity of 95% were added to the reaction kettle at a molar ratio of 2.5:8.5:1, and the temperature was raised to 160 °C for reaction. During the reaction process, continuous stirring was carried out for 5 hours to obtain a crude product of octafluorocyclobutane.

[0062] Step S2. Two-stage rectification for impurity removal

[0063] Light component removal in the rectification column: In the rectification process, liquid nitrogen was used as the cold source. The feed was about 2 / 3 of the column bottom, and the pressure was maintained at 0.2 - 0.3 MPa, and the temperature was at 15 °C - 20 °C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide, and impurities with boiling points close to that of octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reached over 99.95%, the gaseous octafluorocyclobutane entered the secondary adsorption.

[0064] Adsorption for impurity removal: The gas after rectification entered the adsorption equipment to adsorb water, carbon dioxide, halogenated hydrocarbon compounds, etc. The rectified octafluorocyclobutane was passed into the adsorption tower filled with adsorbents. The internal filling of the adsorption tower was a mixed adsorbent of type A molecular sieve and activated carbon. The adsorption temperature was 25 - 30 °C, and the residence time was 50 s. The refined product of octafluorocyclobutane with a purity of 99.99% was obtained by the method of reacting and purifying simultaneously. Finally, it was received by a low-temperature cooling device, and the cooling temperature was -14 °C - -10 °C.

[0065] Continuous reaction: The light components removed by rectification were recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification was lower than 0.1 Mpa, alkali metal fluoride was added to the reaction kettle until the rectification pressure reached 0.19 Mpa.

[0066] Example 7

[0067] NaF, diethylene glycol dimethyl ether, and 1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane with a purity of 95% were added to the reaction kettle at a molar ratio of 3:7:1, and the temperature was raised to 180 °C. During the reaction process, continuous stirring was carried out for 5 hours to obtain a crude product of octafluorocyclobutane.

[0068] Step S2. Two-stage rectification for impurity removal

[0069] Light component removal in the rectification column: In the rectification process, liquid nitrogen was used as the cold source. The feed was about 2 / 3 of the column bottom, and the pressure was maintained at 0.2 - 0.3 MPa, and the temperature was at 15 °C - 20 °C to remove light components, including reaction materials, air, carbon monoxide, carbon dioxide, and impurities with boiling points close to that of octafluorocyclobutane. When the purity of the sampled octafluorocyclobutane reached over 99.95%, the gaseous octafluorocyclobutane entered the secondary adsorption.

[0070] Adsorption and impurity removal: The gas after rectification enters the adsorption equipment to adsorb moisture, carbon dioxide, halogenated hydrocarbon compounds, etc. The perfluorocyclobutane after rectification is introduced into the adsorption tower filled with adsorbent. The inside of the adsorption tower is filled with a mixed adsorbent of X-type molecular sieve and silica gel. The adsorption temperature is 35 - 40°C, the residence time is 40 s, and the high-quality perfluorocyclobutane product with a purity of 99.99% is obtained by the method of reacting and purifying simultaneously. Finally, it is received by a low-temperature cooling device, and the cooling temperature is -14 - -10°C.

[0071] Continuous reaction: The light components removed by rectification are recycled to the reaction kettle to continue participating in the fluorine-chlorine exchange reaction. When the pressure of rectification is lower than 0.1 Mpa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.17 Mpa.

[0072] Comparative Example 1

[0073] The difference in technical features between this comparative example and Example 1 is that the reaction temperature is 80°C.

[0074] Comparative Example 2

[0075] The difference in technical features between this comparative example and Example 1 is that the reaction temperature is 260°C.

[0076] Comparative Example 3

[0077] The difference in technical features between this comparative example and Example 1 is that the solvent is absolute ethanol.

[0078] Product detection

[0079] The yields, purities, moisture contents, and chloride ion contents of the products in Examples 1 - 7 and Comparative Examples 1 - 3 were detected, and the results are shown in Table 1.

[0080] Table 1

[0081] Sample Product purity (%) Water content (%) Chloride ion (%) Example 1 92.5 <0.1 <0.1 Example 2 98.7 <0.1 <0.1 Example 3 93.1 <0.1 <0.1 Example 4 92.2 <0.1 <0.1 Example 5 94.6 <0.1 <0.1 Example 6 96.0 <0.1 <0.1 Example 7 95.4 <0.1 <0.1 Comparative Example 1 85.3 <0.1 1.1 Comparative Example 2 80.6 <0.1 2.0 Comparative Example 3 81.2 <0.1 1.3

[0082] By comparing the test results of the above Examples 1 - 7 and Comparative Examples 1 - 4, it can be found that by using the method of the present application,

[0083] Perfluorocyclobutane with high yield and high content can be obtained. The product yield can reach 70.8%, the product purity > 99%, the water content < 0.1%, and the chloride ion detection < 0.1%. Moreover, the production process of the present application is pollution-free, the prepared perfluorocyclobutane has high selectivity, the equipment is simple and continuous production can be realized, the yield is high, the raw materials are cheap, which is beneficial to reducing production costs, and the product purity is high. It is a method for preparing perfluorocyclobutane suitable for industrial production. In the comparative examples, due to inappropriate reaction temperature or solvent selectivity, the product yield is low, the purity is not high, and the impurity content is high.

[0084] The above are only the preferred embodiments of the present application and do not impose any formal restrictions on the present application. Although the present application has been disclosed above with the preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to equivalent embodiments with equivalent changes within the scope of the technical solution of the present application. However, as long as it does not depart from the content of the technical solution of the present application, any modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application still fall within the scope of the technical solution of the present application.

Claims

1. A method for continuously synthesizing octafluorocyclobutane industrially, characterized in that, It includes the following steps: Step S1. Add 1,1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane, alkali metal fluoride and organic aprotic solvent into a reaction kettle, heat and stir to carry out a fluorochloride exchange reaction to obtain crude octafluorocyclobutane; Step S2. Purify the crude octafluorocyclobutane through two stages of rectification and adsorption, and finally collect the refined octafluorocyclobutane.

2. The method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, wherein The alkali metal fluoride is NaF or KF.

3. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The organic aprotic solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, sulfolane, and diethylene glycol dimethyl ether.

4. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The reaction temperature is 140-180 °C.

5. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The initial feeding molar ratio of 1,1,2,2,3,4-hexafluoro-3,4-dichlorocyclobutane, alkali metal fluoride and organic aprotic solvent is 1:(2-4):(7-10).

6. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The pressure of the rectification is 0.1-0.3 MPa, and the temperature is -5 °C to 20 °C.

7. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The adsorbent selected for adsorption purification is one or a mixture of adsorbents such as X-type molecular sieve, A-type molecular sieve, activated carbon or silica gel. The adsorption temperature is 10-40 °C, and the adsorption residence time is 40-80 s.

8. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The temperature for collecting the refined octafluorocyclobutane is -20 °C to -10 °C.

9. A method for industrially continuously synthesizing octafluorocyclobutane according to claim 1, characterized in that, The light components removed by the rectification are recycled to the reaction kettle to continue participating in the fluorochloride exchange reaction. When the pressure of the rectification is lower than 0.1 MPa, alkali metal fluoride is added to the reaction kettle until the rectification pressure reaches 0.15-0.2 Mpa.

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