A process for the separation of hexafluoropropylene oxide and hexafluoropropylene

Abstract

The present application relates to fluorine chemical technology field, disclose a kind of hexafluoropropylene oxide and hexafluoropropylene separation process, with fluorine-containing solvent as extractant, using extraction rectification column and desorption rectification column simultaneous to the mixture containing hexafluoropropylene oxide and hexafluoropropylene is extracted rectification, realize the separation of hexafluoropropylene oxide and hexafluoropropylene.The present application uses fluorine-containing solvent as extractant, using extraction rectification technology will hexafluoropropylene oxide and hexafluoropropylene effectively separate, and then obtain high-purity hexafluoropropylene oxide product and hexafluoropropylene product.The fluorine-containing solvent used in the present application is not only environment-friendly, extraction effect is obvious, and high stability, even if hexafluoropropylene oxide product and hexafluoropropylene product entrain small amount of extractant, its subsequent application development influence is also smaller.

Description

Technical Field

[0001] This invention relates to the field of fluorochemical technology, and in particular to a separation process for hexafluoropropylene oxide and hexafluoropropylene. Background Technology

[0002] In the synthesis of hexafluoropropylene oxide (HFPO), hexafluoropropylene (HFP) cannot be completely converted, therefore, HFPO needs to be separated from HFP in subsequent separation processes. However, unreacted HFP has a boiling point of -29.4℃, while HFPO has a boiling point of -27.4℃; their boiling points are very close, meaning their relative volatility is low. Separating them using traditional distillation processes would require extremely tall distillation columns. However, extractive distillation technology, using a suitable extractant, reduces the volatility of HFP, thereby increasing the relative volatility of HFPO. This allows for a reduction in column height within a limited space, and also lowers the reflux ratio, achieving energy savings and reducing consumption while obtaining high-purity HFPO.

[0003] Currently, the research status of HFPO and HFP separation processes includes extractive distillation. For example, patent CN200810238474.4 relates to a method for preparing high-purity hexafluoropropylene oxide by extractive distillation. Epichlorohydrin is selected as the extractant, and the mass ratio of the extractant to the HFPO-HFP mixture is controlled at (1-200):1. The HFPO-HFP mixture is fed into an extractive distillation column, with epichlorohydrin sprayed from the top. HFPO separates from the top of the column, yielding HFPO with a purity of over 99%. HFP and epichlorohydrin are discharged from the bottom of the extractive distillation column and then pumped into a recovery column. HFP is separated from the top of the recovery column, and epichlorohydrin is discharged from the bottom of the recovery column and pumped back to the top spray port of the extractive distillation column for recycling. The method of this invention selects epichlorohydrin as the extractant, achieving a relative volatility of HFPO and HFP of 1.5-3.7, which allows for effective separation of the two. For example, Yang Bo of Zhejiang University conducted research on the separation of hexafluoropropylene and hexafluoropropylene oxide. He designed and manufactured an experimental device to measure the gas-liquid equilibrium data of the hexafluoropropylene and hexafluoropropylene oxide system, determining that dichloromethane was the optimal extractant. Subsequently, he measured the gas-liquid equilibrium data of the HFP and HFPO systems using dichloromethane as the extractant. Based on this, he used Aspenplus to simulate and optimize the separation of HFP and HFPO. By changing different conditions such as feed location, solvent ratio, and reflux ratio, he obtained the optimal process conditions for each. He then determined the optimal process flow and process parameters for the extractive distillation column.

[0004] US Patent 3326780 describes a process for refining HFPO, which uses extractive distillation to separate and purify HFPO. By using a solvent that affects relative volatility, the height of the equipment for separating HFPO and HFP can be reduced, thereby reducing equipment investment costs. It is believed that effective separation of the two can be achieved in the presence of extractants such as carbon tetrachloride or chloroform, mono-, di-, or tri-substituted benzenes (where the substituents are alkyl groups or alkoxy groups containing 1-4 carbon atoms), dialkyl ethers of vinyl ethylene glycol or divinyl ethylene glycol (where the hydrocarbon group of the ether has 1-2 carbon atoms), chlorinated hydrocarbons containing 2 or more carbon atoms, and dialkyl ethers with at least one hydrocarbon group having been dechained and having 3 or more carbon atoms. This method can obtain HFPO with a purity of 99.5%. However, its disadvantage is that the ethers undergo slow chemical changes under operating conditions, so the discharged reactants must be constantly replaced with fresh extractants.

[0005] As mentioned above, most existing HFPO and HFP separation processes use chloroalkyl or traditional organic solvents. These extractants have limited extraction and distillation effects and can cause some environmental pollution. In addition, trace amounts of extractants may be carried in the separated HFP and HFPO products. Due to the poor stability of these extractants, the application of HFP and HFPO products may be affected. Summary of the Invention

[0006] In view of this, the present invention provides a separation process for hexafluoropropylene oxide and hexafluoropropylene to solve the problems of limited extractive distillation effect, environmental unfriendliness, and poor stability of the extractants used in existing separation processes, which restricts the application of HFP and HFPO products.

[0007] To solve the above problems, the present invention adopts the following technical solution: A separation process for hexafluoropropylene oxide and hexafluoropropylene is disclosed, which uses a fluorinated solvent as an extractant and employs a combination of an extractive distillation column and a desorption distillation column to extract and distill a mixture containing hexafluoropropylene oxide and hexafluoropropylene, thereby achieving the separation of hexafluoropropylene oxide and hexafluoropropylene.

[0008] Preferably, the extractant comprises one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ether, methyl nonafluorobutyl ether, and hexafluoropropylene trimer.

[0009] Preferably, the mixture contains 30-80% hexafluoropropylene oxide and 70-20% hexafluoropropylene by mass percentage.

[0010] Preferably, the specific steps for extractive distillation of the mixture containing hexafluoropropylene oxide and hexafluoropropylene using a combination of extractive distillation and desorption distillation columns are as follows: (1) The extractant is fed from the upper part of the extractive distillation column and simultaneously fed from the lower part of the desorption distillation column to establish a circulation system of the extractant between the extractive distillation column and the desorption distillation column; (2) The mixture is fed from the bottom of the extractive distillation column, and the mixture and extractant are contacted in opposite directions. After separation by extractive distillation, hexafluoropropylene oxide is obtained from the top of the column, and a mixture of hexafluoropropylene and extractant is obtained from the bottom of the column. (3) The mixture of hexafluoropropylene and extractant is fed from the bottom of the desorption distillation column. After desorption distillation separation, hexafluoropropylene product is obtained from the top of the column.

[0011] Preferably, the pressure of the extractive distillation column is 0.2-0.8 MPa, the reflux ratio is 5-20, the top temperature is 0-40℃, the bottom temperature is 50-150℃, and the extraction ratio is 2-20.

[0012] Preferably, the pressure of the desorption distillation column is 0.05-0.2 MPa, the reflux ratio is 5-20, the top temperature is -25 to 0℃, and the bottom temperature is 50-110℃.

[0013] Preferably, in step (3), the bottom of the desorption distillation column obtains a material containing the extractant, and the material containing the extractant is sent to the upper middle part of the extractive distillation column for circulation.

[0014] Preferably, the packing material of the extraction distillation column and the desorption distillation column is independently either wire mesh corrugated packing or perforated plate corrugated packing.

[0015] Preferably, the height of the packing is 3-10m.

[0016] This invention provides a separation process for hexafluoropropylene oxide and hexafluoropropylene, which has the following advantages compared with the prior art: This invention uses a fluorinated solvent as an extractant and employs extractive distillation technology to effectively separate hexafluoropropylene oxide and hexafluoropropylene, thereby obtaining high-purity hexafluoropropylene oxide and hexafluoropropylene products. The fluorinated solvent used in this invention is not only environmentally friendly and has a significant extraction effect, but also exhibits high stability. Even if the hexafluoropropylene oxide and hexafluoropropylene products contain a small amount of extractant, it has minimal impact on their subsequent application development. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0020] This invention provides a separation process for hexafluoropropylene oxide and hexafluoropropylene, using a fluorinated solvent as the extractant and employing a combination of an extractive distillation column and a desorption distillation column to extract and distill a mixture containing hexafluoropropylene oxide and hexafluoropropylene, thereby achieving the separation of hexafluoropropylene oxide and hexafluoropropylene.

[0021] In some embodiments of the present invention, the extractant comprises one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE-347), 1,1,2,2-tetrafluoroethyl ether (HFE-374), methyl nonafluorobutyl ether (HFE-7100), and hexafluoropropylene trimer. It should be noted that the extractant used in the present invention has low ozone depletion potential (ODP) and global warming potential (GWP), making it not only environmentally friendly but also exhibiting significant extraction efficiency and high stability. When the extractant is a mixture of two or more substances, the above-mentioned effects can be achieved by mixing the substances in any proportion, and no special limitations are imposed on this.

[0022] In some embodiments of the present invention, the content of hexafluoropropylene oxide in the mixture, by mass percentage, is 30-80%, specifically 30%, 40%, 50%, 60%, 70%, and 80%, etc.; the content of hexafluoropropylene in the mixture is 70-20%, specifically 70%, 60%, 50%, 40%, 30%, and 20%, etc. It should be noted that the main objective of the present invention is to effectively separate hexafluoropropylene oxide and hexafluoropropylene. Regardless of the distribution of hexafluoropropylene oxide and hexafluoropropylene content in the mixture, effective separation can be achieved through extractive distillation of the present invention. However, considering the purity of the separated hexafluoropropylene oxide and hexafluoropropylene, the content of hexafluoropropylene oxide and hexafluoropropylene in the mixture is limited.

[0023] In some embodiments of the present invention, the specific steps for extractive distillation of a mixture containing hexafluoropropylene oxide and hexafluoropropylene using a combination of an extractive distillation column and a desorption distillation column are as follows: (1) The extractant is fed from the upper part of the extractive distillation column and simultaneously fed from the lower part of the desorption distillation column to establish a circulation system of the extractant between the extractive distillation column and the desorption distillation column; (2) The mixture is fed from the bottom of the extractive distillation column, and the mixture and extractant are contacted in opposite directions. After separation by extractive distillation, hexafluoropropylene oxide is obtained from the top of the column, and a mixture of hexafluoropropylene and extractant is obtained from the bottom of the column. (3) The mixture of hexafluoropropylene and extractant is fed from the bottom of the desorption distillation column. After desorption distillation separation, hexafluoropropylene product is obtained from the top of the column.

[0024] It should be noted that feeding the extractant and the mixture from the upper middle and lower parts of the extractive distillation column, respectively, allows the mixture and the extractant to contact in opposite directions, improving extraction efficiency. In addition, feeding the extractant from the lower part of the desorption distillation column can reduce the entrainment of the extractant from the desorption distillation column, improving the distillation effect.

[0025] In some embodiments of the present invention, the pressure of the extractive distillation column is 0.2-0.8 MPa, specifically 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, and 0.8 MPa; the reflux ratio is 5-20, specifically 5, 10, 15, and 20; the column top temperature is 0-40°C, specifically 0°C, 10°C, 20°C, 30°C, and 40°C; the column bottom temperature is 50-150°C, specifically 50°C, 80°C, 100°C, 120°C, and 150°C; and the extraction ratio is 2-20, specifically 2, 10, 15, and 20.

[0026] In some embodiments of the present invention, the pressure of the desorption distillation column is 0.05-0.2 MPa, specifically 0.05 MPa, 0.1 MPa, 0.15 MPa, and 0.2 MPa, etc.; the reflux ratio is 5-20, specifically 5, 10, 15, and 20, etc.; the column top temperature is -25 to 0°C, specifically -25°C, -20°C, -15°C, -10°C, -5°C, and 0°C, etc.; and the column bottom temperature is 50-110°C, specifically 50°C, 70°C, 90°C, and 110°C, etc.

[0027] It should be noted that, in order to achieve better separation results, the pressure of the extractive distillation column and the temperature of the top and bottom of the desorption distillation column need to be limited within the above-mentioned ranges; otherwise, hexafluoropropylene oxide and hexafluoropropylene cannot be effectively separated. Furthermore, considering the liquid load and energy consumption of the bottom column, the extraction ratio and reflux ratio are limited within the above-mentioned ranges.

[0028] In some embodiments of the present invention, the bottom of the desorption distillation column in step (3) obtains a material containing extractant, and the material containing extractant is sent to the upper middle part of the extractive distillation column for circulation.

[0029] In some embodiments of the present invention, the packing of the extraction distillation column and the desorption distillation column are each independently wire mesh corrugated packing or perforated plate corrugated packing.

[0030] In some embodiments of the present invention, the height of the filler is 3-10m, specifically 3m, 5m, 8m and 10m, etc.

[0031] The technical solutions of this invention will be clearly and completely described below with reference to specific embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] The extraction distillation column and desorption distillation column of the separation process of this invention are both systems composed of only three components: HFP, HFPO and extractant, with no other impurities present. The content of each component is its purity in the system, and the sum of the contents of the three is 100%.

[0033] Example 1 This embodiment provides a separation process for hexafluoropropylene oxide and hexafluoropropylene, the specific steps of which are as follows: (1) Mix HFPO and HFP raw materials at a mass ratio of 6:4 and store them in a feed tank.

[0034] (2) The extractant HFE-347 is fed from the upper part of the extractive distillation column and simultaneously fed from the lower part of the desorption distillation column to establish a circulation system of the extractant between the extractive distillation column and the desorption distillation column.

[0035] (3) The mixture is fed from the bottom of the extractive distillation column. The mixture and the extractant are in countercurrent contact in the packed section. After extractive distillation separation, hexafluoropropylene oxide product is obtained from the top of the column, and a mixture of hexafluoropropylene and extractant is obtained from the bottom of the column. The pressure of the extractive distillation column is 0.6 MPa, the reflux ratio is 12, the top temperature is 28.5℃, the bottom temperature is 79.7℃, the extraction ratio is 17, the packing is wire mesh corrugated packing, and the packing height is 10m.

[0036] (4) The mixture of hexafluoropropylene and extractant is fed from the bottom of the desorption distillation column. After desorption distillation separation, hexafluoropropylene product is obtained from the top of the column, and material containing extractant is obtained from the bottom of the column. The material containing extractant is sent to the middle and upper part of the extraction distillation column for circulation. The pressure of the desorption distillation column is 0.18 MPa, the reflux ratio is 17, the top temperature is -2.8℃, the bottom temperature is 61.3℃, the packing is wire mesh corrugated packing, and the packing height is 10m.

[0037] In this embodiment, the HFPO content in the top product of the extractive distillation column is 97.31%, the HFP content is 2.02%, and the extractant content is 0.67%; the HFP content in the top product of the desorption distillation column is 99.29%, the HFPO content is 0.18%, and the extractant content is 0.53%.

[0038] Example 2 This embodiment is basically the same as Embodiment 1, except that the mixing ratio of HFPO and HFP, the type of extractant, and the parameters of the extractive distillation column and the desorption distillation column are different.

[0039] Specifically, HFPO and HFP feedstocks are mixed at a mass ratio of 8:2; the extractant is HFE-374; the pressure of the extractive distillation column is 0.45 MPa, the reflux ratio is 14, the top temperature is 20.5℃, the bottom temperature is 81.5℃, and the extraction ratio is 14; the pressure of the desorption distillation column is 0.09 MPa, the reflux ratio is 10, the top temperature is -13.9℃, and the bottom temperature is 64.4℃.

[0040] In this embodiment, the HFPO content in the top product of the extractive distillation column is 99.56%, the HFP content is 0.13%, and the extractant content is 0.31%; the HFP content in the top product of the desorption distillation column is 97.37%, the HFPO content is 0.19%, and the extractant content is 2.44%.

[0041] Example 3 This embodiment is basically the same as Embodiment 1, except that the mixing ratio of HFPO and HFP, the type of extractant, and the parameters of the extractive distillation column and the desorption distillation column are different.

[0042] Specifically, HFPO and HFP feedstocks are mixed at a mass ratio of 6:4; the extractant is HFE-7100; the pressure of the extractive distillation column is 0.5 MPa, the reflux ratio is 11, the top temperature is 22.6℃, the bottom temperature is 59.8℃, and the extraction ratio is 12; the pressure of the desorption distillation column is 0.1 MPa, the reflux ratio is 19, the top temperature is -11.8℃, and the bottom temperature is 61.8℃.

[0043] In this embodiment, the HFPO content in the top product of the extractive distillation column is 96.77%, the HFP content is 2.28%, and the extractant content is 0.95%; the HFP content in the top product of the desorption distillation column is 99.37%, the HFPO content is 0.11%, and the extractant content is 0.52%.

[0044] Example 4 This embodiment is basically the same as Embodiment 1, except that the mixing ratio of HFPO and HFP, the type of extractant, and the parameters of the extractive distillation column and the desorption distillation column are different.

[0045] Specifically, the feedstocks HFPO and HFP are mixed at a mass ratio of 6:4; the extractants are HFE-374 and HFE-7100 at a volume ratio of 1:1; the pressure of the extractive distillation column is 0.35 MPa, the reflux ratio is 18, the top temperature is 12.3℃, the bottom temperature is 70.8℃, and the extraction ratio is 8; the pressure of the desorption distillation column is 0.1 MPa, the reflux ratio is 17, the top temperature is -12.3℃, and the bottom temperature is 63.0℃.

[0046] In this embodiment, the HFPO content in the top product of the extractive distillation column is 99.14%, the HFP content is 0.72%, and the extractant content is 0.14%; the HFP content in the top product of the desorption distillation column is 98.96%, the HFPO content is 0.91%, and the extractant content is 0.13%.

[0047] Example 5 This embodiment is basically the same as Embodiment 1, except that the mixing ratio of HFPO and HFP, the type of extractant, and the parameters of the extractive distillation column and the desorption distillation column are different.

[0048] Specifically, HFPO and HFP feedstocks are mixed at a mass ratio of 3:7; the extractant is hexafluoropropylene trimer; the extractive distillation column has a pressure of 0.25 MPa, a reflux ratio of 6, a top temperature of 4.1℃, a bottom temperature of 88.6℃, an extraction ratio of 5, and is packed with perforated corrugated packing with a packing height of 10m; the desorption distillation column has a pressure of 0.05 MPa, a reflux ratio of 5, a top temperature of -19.8℃, a bottom temperature of 103℃, and is packed with perforated corrugated packing with a packing height of 10m.

[0049] In this embodiment, the HFPO content in the top product of the extractive distillation column is 96.06%, the HFP content is 3.90%, and the extractant content is 0.04%; the HFP content in the top product of the desorption distillation column is 99.81%, the HFPO content is 0.11%, and the extractant content is 0.08%.

[0050] Example 6 This embodiment is basically the same as Embodiment 2, except that the mixing ratio of HFPO and HFP is different. Specifically, the raw materials HFPO and HFP are mixed in a mass ratio of 5:5.

[0051] In this embodiment, the HFPO content in the top product of the extractive distillation column is 98.92%, the HFP content is 0.84%, and the extractant content is 0.24%; the HFP content in the top product of the desorption distillation column is 96.66%, the HFPO content is 0.27%, and the extractant content is 3.07%.

[0052] Example 7 This embodiment is basically the same as Embodiment 1, except that the extraction ratio set in the extractive distillation column is different. Specifically, the extraction ratio is 4.

[0053] In this embodiment, the HFPO content in the top product of the extractive distillation column is 85.32%, the HFP content is 14.26%, and the extractant content is 0.42%; the HFP content in the top product of the desorption distillation column is 80.17%, the HFPO content is 19.75%, and the extractant content is 0.08%.

[0054] Example 8 This embodiment is basically the same as Embodiment 4, except that the reflux ratios set for the extractive distillation column and the desorption distillation column are different. Specifically, the reflux ratio for the extractive distillation column is 6, and the reflux ratio for the desorption distillation column is 5.

[0055] In this embodiment, the HFPO content in the top product of the extractive distillation column is 96.01%, the HFP content is 0.74%, and the extractant content is 3.25%; the HFP content in the top product of the desorption distillation column is 95.10%, the HFPO content is 1.25%, and the extractant content is 3.65%.

[0056] Example 9 This embodiment is basically the same as Embodiment 2, the only difference being the type of packing material used in the extractive distillation column and the desorption distillation column. Specifically, the packing material is perforated corrugated packing.

[0057] In this embodiment, the HFPO content in the top product of the extractive distillation column is 98.24%, the HFP content is 1.18%, and the extractant content is 0.58%; the HFP content in the top product of the desorption distillation column is 96.89%, the HFPO content is 0.21%, and the extractant content is 2.90%.

[0058] Example 10 This embodiment is basically the same as Embodiment 5, except that the packing height of the extractive distillation column and the desorption distillation column are different. Specifically, the packing height is 3m.

[0059] In this embodiment, the HFPO content in the top product of the extractive distillation column is 78.33%, the HFP content is 20.18%, and the extractant content is 1.49%; the HFP content in the top product of the desorption distillation column is 90.08%, the HFPO content is 7.59%, and the extractant content is 2.33%.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A process for separating hexafluoropropylene oxide and hexafluoropropylene, characterized in that, Using a fluorinated solvent as the extractant, an extractive distillation column and a desorption distillation column are used in combination to extract and distill a mixture containing hexafluoropropylene oxide and hexafluoropropylene, thereby achieving the separation of hexafluoropropylene oxide and hexafluoropropylene.

2. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 1, characterized in that, The extractant includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ether, methyl nonafluorobutyl ether, and hexafluoropropylene trimer.

3. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 1, characterized in that, The mixture contains 30-80% hexafluoropropylene oxide and 70-20% hexafluoropropylene by mass percentage.

4. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 1, characterized in that, The specific steps for extractive distillation of a mixture containing hexafluoropropylene oxide and hexafluoropropylene using a combination of extractive distillation and desorption distillation columns are as follows: (1) The extractant is fed from the upper part of the extractive distillation column and simultaneously fed from the lower part of the desorption distillation column to establish a circulation system of the extractant between the extractive distillation column and the desorption distillation column; (2) The mixture is fed from the bottom of the extractive distillation column, and the mixture and extractant are contacted in opposite directions. After separation by extractive distillation, hexafluoropropylene oxide is obtained from the top of the column, and a mixture of hexafluoropropylene and extractant is obtained from the bottom of the column. (3) The mixture of hexafluoropropylene and extractant is fed from the bottom of the desorption distillation column. After desorption distillation separation, hexafluoropropylene product is obtained from the top of the column.

5. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 1 or 4, characterized in that, The pressure of the extractive distillation column is 0.2-0.8 MPa, the reflux ratio is 5-20, the top temperature is 0-40℃, the bottom temperature is 50-150℃, and the extraction ratio is 2-20.

6. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 1 or 4, characterized in that, The desorption distillation column has a pressure of 0.05-0.2 MPa, a reflux ratio of 5-20, a top temperature of -25 to 0℃, and a bottom temperature of 50-110℃.

7. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 4, characterized in that, In step (3), the bottom of the desorption distillation column obtains a material containing the extractant, and the material containing the extractant is sent to the upper middle part of the extractive distillation column for circulation.

8. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 1 or 4, characterized in that, The packing materials for the extraction distillation column and the desorption distillation column are each independently either wire mesh corrugated packing or perforated plate corrugated packing.

9. The separation process for hexafluoropropylene oxide and hexafluoropropylene according to claim 8, characterized in that, The height of the packing material is 3-10m.

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