Method for recovering fluoroether from hexafluoropropylene rectification residual liquid

Abstract

The invention relates to the technical field of hexafluoropropylene rectification post-treatment, and discloses a method for recovering fluoroether from hexafluoropropylene rectification raffinate, and the method comprises the following steps: S1, mixing hexafluoropropylene rectification raffinate with alcohol, and carrying out reactive rectification to obtain a fluoroether-containing mixture and reactive rectification mixed gas; s2, carrying out first rectification on the fluorine-containing ether mixture to obtain a fluorine ether-alcohol azeotrope; and S3, extracting the fluoroether-alcohol azeotrope to obtain a fluoroether crude product, and carrying out second rectification on the fluoroether crude product. According to the present invention, the reaction rectification technology is adopted to reinforce the etherification reaction of the hexafluoropropylene rectification residual liquid and the alcohol, and the reaction product is timely separated during the chemical reaction, such that the reaction conversion rate is substantially improved, the reaction heat is efficiently utilized, and the conversion rate of the highly toxic octafluoroisobutene and the fluoroether yield are significantly increased. Reactive rectification, first rectification, extraction and second rectification are effectively integrated, and a fluoroether product with the purity being larger than 99% is obtained.

Description

Method for recovering fluoroethers from hexafluoropropylene distillation residue Technical Field

[0001] This invention relates to the field of hexafluoropropylene distillation post-treatment technology, specifically, to a method for recovering fluoroethers from hexafluoropropylene distillation residues. Background Technology

[0002] Hexafluoropropylene (HFP) is one of the important basic raw materials in the organofluorine industry. It is a comonomer of many fluorinated copolymers and an intermediate for various fluorinated compounds. The distillation residue of hexafluoropropylene is substantial, accounting for about 20% of the product. The residue mainly contains octafluorocyclobutane (C318), octafluoroisobutylene, and octafluoron-butene, among which octafluoroisobutylene is a highly toxic hazardous chemical.

[0003] Currently, the common treatment method used by production enterprises is to mix methanol and the residual liquid for reaction, partially eliminating toxicity, before sending it to an incinerator for combustion. Although the reaction time of mixing methanol and the residual liquid is very long, the residual liquid still contains unreacted octafluoroisobutylene. Due to the high toxicity of octafluoroisobutylene, production enterprises can only adopt incineration as a treatment measure. However, the residual liquid after the mixing reaction contains a large amount of useful components such as octafluorobutene and fluoroethers. Incinerating it entirely not only wastes resources and increases energy consumption, but also generates a large amount of waste gas, wastewater, and solid waste, increasing environmental pressure.

[0004] CN117756602A proposes a batch distillation method to recover useful components from the residue after methanol reaction sterilization. The residue is added in batches to a batch reactor and reacted with methanol. The resulting mixture is then distilled in a batch distillation column to recover octafluorocyclobutane, octafluoro-n-butene, methyl hexafluoroisobutyrate, and heptafluoroisobutylene methyl ether. However, the use of a batch reactor limits the reaction conversion rate, and the products contain a certain amount of highly toxic octafluoroisobutene. Furthermore, the batch distillation column at the end of the process yields different products at different times, requiring frequent switching operations. This not only increases the danger and complexity of the recovery operation but also results in low purity of the recovered products, including the presence of highly toxic octafluoroisobutene, limiting the product's applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of wasteful incineration, low purity of recovered products and presence of octafluoroisobutylene (highly toxic), low reaction conversion rate, and complex and dangerous intermittent separation operation in existing technologies. This invention provides a method for recovering fluoroethers from hexafluoropropylene distillation residues. This method has advantages such as continuous, efficient and safe production, energy saving and consumption reduction, high purity of recovered products and high yield, bringing significant economic and environmental benefits.

[0006] To achieve the above objectives, the present invention provides a method for recovering fluoroethers from hexafluoropropylene distillation residue, the method comprising: S1, mixing hexafluoropropylene distillation residue with an alcohol and performing reactive distillation to obtain a fluoroether-containing mixture and a reactive distillation mixture gas; S2, performing a first distillation on the fluoroether-containing mixture to obtain a fluoroether-alcohol azeotrope; S3, extracting the fluoroether-alcohol azeotrope to obtain a crude fluoroether product, and then performing a second distillation on the crude fluoroether product.

[0007] Through the above technical solutions, the present invention can achieve at least the following beneficial effects: (1) In the process of treating the distillation residue of hexafluoropropylene, the present invention adopts reactive distillation, extraction, and first and second distillation, which greatly improves the purity of the recovered fluoroether and obtains a fluoroether product with a purity of >99%.

[0008] (2) The present invention uses reactive distillation technology to enhance the etherification reaction of octafluoroisobutylene and alcohol in the distillation residue of hexafluoropropylene. The reaction products are separated in time during the chemical reaction, which not only greatly improves the reaction conversion rate, but also makes efficient use of the reaction heat, significantly increases the conversion rate of highly toxic octafluoroisobutylene and the yield of fluoroether, and reduces energy consumption.

[0009] (3) The present invention adopts continuous, efficient and safe production of reactive distillation, first distillation, extraction and second distillation without switching operation, realizing full-process automation, which not only simplifies the recovery operation, but also ensures the safety of the staff. Attached Figure Description

[0010] Figure 1 is a simplified process flow diagram of the recovery of fluoroether from the distillation residue of hexafluoropropylene according to an embodiment of the present invention. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] This invention provides a method for recovering fluoroethers from hexafluoropropylene distillation residue, the method comprising: S1, mixing hexafluoropropylene distillation residue with an alcohol and performing reactive distillation to obtain a fluoroether-containing mixture and a reactive distillation mixture gas; S2, performing a first distillation on the fluoroether-containing mixture to obtain a fluoroether-alcohol azeotrope; S3, extracting the fluoroether-alcohol azeotrope to obtain a crude fluoroether product, and then performing a second distillation on the crude fluoroether product.

[0013] The inventors of this invention discovered during their research that by employing reactive distillation, extraction, and first and second distillations in the treatment of hexafluoropropylene distillation residues, the purity of recovered fluoroethers was significantly improved, yielding fluoroether products with a purity >99%. Furthermore, reactive distillation can enhance the etherification reaction between octafluoroisobutylene and alcohols in the hexafluoropropylene distillation residues, separating the reaction products simultaneously with the chemical reaction. This not only significantly improves the reaction conversion rate but also efficiently utilizes the heat of reaction, significantly increasing the conversion rate of highly toxic octafluoroisobutylene and the yield of fluoroethers, while reducing energy consumption. This invention effectively integrates reactive distillation, first distillation, extraction, and second distillation, achieving fully automated, continuous, and efficient recovery of fluoroethers while ensuring safe production. No switching operations are required, simplifying the recovery process and guaranteeing the safety of personnel.

[0014] In this invention, preferably, the hexafluoropropylene distillation residue contains at least one of octafluorocyclobutane, octafluoroisobutene, octafluoron-butene, and a polymerization inhibitor.

[0015] In this invention, preferably, based on the total weight of octafluorocyclobutane, octafluoroisobutene, octafluoron-butene, and the polymerization inhibitor, the content of octafluorocyclobutane can be 0.01-5 wt% (for example, it can be any two values ​​formed by 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or values ​​within that range), and the content of octafluoroisobutene can be 45-65 wt% (for example, it can be any two values ​​formed by 45 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, 62 wt%, 64 wt%, 65 wt%). The content of octafluorobutene can be 30-50 wt% (e.g., it can be any two values ​​formed by 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%) and the content of polymerization inhibitor can be 0.01-0.5 wt% (e.g., it can be any two values ​​formed by 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%) and the value within the range of 0.5 wt%.

[0016] In this invention, preferably, in step S1, the alcohol can be selected from C1-C4 alcohols, more preferably at least one of methanol, ethanol and propanol.

[0017] In this invention, preferably, in step S1, the mass ratio of the alcohol to the hexafluoropropylene distillation residue can be 0.1-5:1 (for example, it can be any two ratios from 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any ratio within that range), more preferably it can be 1-3:1.

[0018] In this invention, preferably, the conditions for the reactive distillation include: a temperature of 0-90°C (for example, a range formed by any two values ​​from 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and values ​​within that range), and a pressure of 0-0.2 MPa (for example, a range formed by any two values ​​from 0 MPa, 0.01 MPa, 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, and values ​​within that range).

[0019] In this invention, preferably, relative to a reactive distillation apparatus with a processing capacity of 300 kg / h, the processing rate of the hexafluoropropylene distillation residue can be 100-500 kg / h (for example, it can be any two values ​​formed by 100 kg / h, 150 kg / h, 200 kg / h, 250 kg / h, 300 kg / h, 350 kg / h, 400 kg / h, 450 kg / h, 500 kg / h, and values ​​within that range).

[0020] In this invention, preferably, the conditions for the first distillation may include: a temperature of 10-90°C (for example, a range formed by any two values ​​from 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and values ​​within that range), and a pressure of 0-0.2 MPa (for example, a range formed by any two values ​​from 0 MPa, 0.01 MPa, 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, and values ​​within that range).

[0021] In this invention, preferably, relative to a distillation apparatus with a processing capacity of 400 kg / h, the processing rate of the fluorinated ether mixture in the first distillation can be 100-700 kg / h (for example, it can be a range formed by any two values ​​among 100 kg / h, 150 kg / h, 200 kg / h, 250 kg / h, 300 kg / h, 350 kg / h, 400 kg / h, 450 kg / h, 500 kg / h, 550 kg / h, 600 kg / h, 650 kg / h, and 700 kg / h, and values ​​within that range).

[0022] In this invention, preferably, the temperature of the reactive distillation can be 5-10°C lower than that of the first distillation (for example, it can be any two values ​​formed by 5°C, 6°C, 7°C, 8°C, 9°C, and 10°C, or values ​​within that range), more preferably it can be 5-8°C.

[0023] In this invention, preferably, the pressure of the reactive distillation can be 0.05-0.1 MPa higher than that of the first distillation (for example, it can be a range formed by any two values ​​among 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, and 0.1 MPa, and values ​​within that range).

[0024] In a preferred embodiment of the present invention, the reactive distillation apparatus can be any commonly used apparatus in the art, such as a reactive distillation column. The hexafluoropropylene distillation residue enters the lower part of the reactive distillation column, while the alcohol is added from the upper part. The gaseous substance (octafluoroisobutylene) in the hexafluoropropylene distillation residue undergoes a countercurrent contact with the alcohol in stages.

[0025] In a preferred embodiment of the present invention, the top temperature of the reactive distillation column can be 0-30°C, and the bottom temperature can be 60-90°C; the theoretical number of plates of the reactive distillation column can be 10-50, and the plate spacing can be 0.2-0.4m.

[0026] In this invention, preferably, the first distillation method may further include: recovering light components (e.g., alcohols in fluoroether-alcohol azeotropes) from the first distillation product and reusing them in the reactive distillation process of step (1).

[0027] In this invention, preferably, the extractant used for extraction can be selected from at least one of water, ketones, and hydrocarbons.

[0028] In this invention, preferably, the mass ratio of the extractant to the fluoroether-alcohol azeotrope feed can be 0.5-5:1 (for example, it can be any two ratios from 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any ratio within that range), more preferably, it can be 1-3:1.

[0029] In this invention, preferably, the extraction conditions may include: a temperature of 10-50°C (for example, a range formed by any two values ​​from 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C, and values ​​within that range), and a pressure of 0-0.1 MPa (for example, a range formed by any two values ​​from 0 MPa, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, and 0.1 MPa, and values ​​within that range).

[0030] In this invention, preferably, relative to an extraction device with a processing capacity of 200 kg / h, the extraction rate of the fluoroether-alcohol azeotrope can be 50-300 kg / h (for example, it can be a range formed by any two of the following values: 50 kg / h, 100 kg / h, 150 kg / h, 200 kg / h, 250 kg / h, 300 kg / h, and values ​​within that range).

[0031] In this invention, preferably, the conditions for the second distillation may include: a temperature of 30-90°C (for example, a range formed by any two values ​​from 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, and values ​​within that range), and a pressure of 0-0.1 MPa (for example, a range formed by any two values ​​from 0 MPa, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, and 0.1 MPa, and values ​​within that range).

[0032] In this invention, preferably, relative to a distillation apparatus with a processing capacity of 200 kg / h, the processing rate of the crude fluoroether in the second distillation can be 50-400 kg / h (for example, it can be any two values ​​formed by 50 kg / h, 100 kg / h, 150 kg / h, 200 kg / h, 250 kg / h, 300 kg / h, 350 kg / h, 400 kg / h, or any value within that range).

[0033] In this invention, preferably, the extraction temperature can be 5-15°C lower than the second distillation temperature (for example, it can be any two values ​​formed by 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, or a value within that range), more preferably it can be 6-10°C.

[0034] The present invention will be described in detail below through examples, but the present invention is not limited to the examples involved. In the following examples, parameters such as temperature, pressure, and flow rate are measured by detection instruments in the recovery device; the purity of the fluoroether is measured by a chromatograph using a GC-17A manufactured by SHIMADZU, with a DB624 column (Length 60, ID 0.32, Film 1.8μm).

[0035] Example 1 This example illustrates the continuous and efficient recovery of fluoroether products from the hexafluoropropylene distillation residue-alcohol reaction mixture.

[0036] (1) The hexafluoropropylene distillation residue first enters the lower part of a reactive distillation column (the temperature of the reactive distillation column is 30℃, the pressure is 0.1MPa, the temperature at the top of the column is 30℃, the temperature at the bottom of the column is 90℃, the theoretical number of plates is 20, and the plate spacing is 0.4m) at a feed rate of 300 kg / h. Methanol (fresh alcohol) is added from the top of the reactive distillation column. Octafluoroisobutylene in the residue reacts with methanol in a stepwise countercurrent contact reaction to generate octafluoroisobutyl methyl ether. Through simultaneous reaction and distillation, a mixture containing octafluoroisobutyl methyl ether (i.e., a fluorinated ether mixture) is obtained at the bottom of the reactive distillation column, and a mixed gas containing octafluorocyclobutane and octafluoron-butene is obtained at the top of the column.

[0037] (2) The fluorinated ether mixture collected from the bottom of the reactive distillation column is continuously fed to the middle of the first distillation column (the temperature of the first distillation column is 38℃ and the pressure is 0.05MPa) at a rate of 400kg / h. Through efficient distillation, excess unreacted methanol is recovered from the top of the column and returned to the front reactive distillation column to continue the reaction. Fluorinated ether-methanol azeotrope is obtained from the bottom of the column.

[0038] (3) The fluoroether-methanol azeotrope collected from the bottom of the first distillation column is continuously fed to the top of the extraction column (the temperature of the extraction column is 40℃ and the pressure is 0.01MPa) at a rate of 200kg / h. The extractant (water) is added from the bottom of the extraction column. Through countercurrent contact, the extractant extracts and separates the methanol in the fluoroether-methanol azeotrope. The crude fluoroether is collected from the bottom of the column, and the mixture of extractant (water) and methanol is collected from the top of the column.

[0039] (4) The crude fluoroether product collected from the bottom of the extraction tower is continuously fed to the middle of the second distillation tower (the temperature of the second distillation tower is 50℃ and the pressure is 0.01MPa) at a rate of 200kg / h. Through efficient distillation, octafluoroisobutyl methyl ether is obtained at the top of the tower and can be sold as a product. A small amount of a mixture of extractant (water), residual fluoroether and polymerization inhibitor is collected from the bottom of the tower. Since the amount is small, it can be treated as waste liquid.

[0040] The simplified process flow diagram for recovering fluoroethers from the distillation residue of hexafluoropropylene in Example 1 is shown in Figure 1. Table 1 shows the content of each component in the hexafluoropropylene distillation residue based on the total weight of octafluorocyclobutane, octafluoroisobutylene, octafluoron-butene, and polymerization inhibitor; the feed mass ratio of the reactive distillation column residue to methanol; and the feed mass ratio of the fluoroether-methanol azeotrope to the extractant (water) in the extraction column. Table 2 shows the purity and yield of the octafluoroisobutyl methyl ether product collected from the top of the second distillation column and the conversion rate of octafluoroisobutylene.

[0041] Example 2 recovers fluoroether according to the method of Example 1, except that the mass ratio of methanol to residual liquid in the reactive distillation column is 0.2:1.

[0042] Example 3 recovers fluoroethers according to the method of Example 1, except that the mass ratio of the extractant to the fluoroether-alcohol azeotrope in the extraction tower is 0.5:1.

[0043] Example 4 recovers fluoroether according to the method of Example 1, except that the temperature of the reactive distillation column is 50°C and the pressure is 0.2 MPa.

[0044] Table 1

[0045] Comparative Example 1 was recovered according to the method of Example 1, except that the extraction and second distillation operations in steps (3) and (4) were not performed. That is, the hexafluoropropylene distillation residue was reacted with methanol and subjected to first distillation to obtain a fluoroether-methanol azeotrope.

[0046] Comparative Example 2 was recovered according to the method of Example 1, except that the first distillation operation in step (2) was not performed, that is, the hexafluoropropylene distillation residue was reacted with methanol for distillation, extraction and second distillation to obtain the fluoroether product.

[0047] Comparative Example 3 was recovered according to the method of Example 1, except that the reactive distillation operation in step (1) was replaced by a batch mixing reaction, that is, the hexafluoropropylene distillation residue was subjected to a low-temperature batch mixing reaction, a first distillation, an extraction, and a second distillation to obtain the fluoroether product. Specifically: (1) The hexafluoropropylene distillation residue was added to the reactor in batches at a feed rate of 1500 kg / h (the temperature of the reactor was 0°C and the pressure was 0.3 MPa), and methanol was added to the reactor for a batch mixing reaction. The feed mass ratio of methanol to hexafluoropropylene distillation residue was 1:1.

[0048] (2) The fluorinated ether mixture in the reactor is sent to the middle of the first distillation column (the temperature of the first distillation column is 38℃ and the pressure is 0.05MPa) at a rate of 400kg / h. Through efficient distillation, excess unreacted methanol is recovered at the top of the column and returned to the front-end reaction distillation column to continue the reaction. Fluorinated ether-methanol azeotrope is obtained at the bottom of the column.

[0049] (3) The fluoroether-methanol azeotrope collected from the bottom of the first distillation column is fed to the upper part of the extraction column (the temperature of the extraction column is 40℃ and the pressure is 0.01MPa) at a rate of 200kg / h. The extractant (water) is added from the bottom of the extraction column (the mass ratio of the extractant to the fluoroether-methanol azeotrope is 1:1). Through countercurrent contact, the extractant extracts and separates the methanol in the fluoroether-methanol azeotrope. The crude fluoroether is collected from the bottom of the column, and the mixture of extractant (water) and methanol is collected from the top of the column.

[0050] (4) The crude fluoroether product collected from the bottom of the extraction tower is sent to the middle of the second distillation tower (the temperature of the second distillation tower is 50℃ and the pressure is 0.01MPa) at a rate of 200kg / h. Through efficient distillation, octafluoroisobutyl methyl ether is obtained at the top of the tower and can be sold as a product. A small amount of extractant (water), residual fluoroether and polymerization inhibitor mixture is collected from the bottom of the tower. Since the amount is small, it can be treated as waste liquid.

[0051] Table 2

[0052] The purity of fluoroether products in the table refers to the content of fluoroether in the fluoroether product stream; the yield of fluoroether products = the mass of fluoroether in the fluoroether product stream / the mass of fluoroether produced in the reaction; the conversion rate of octafluoroisobutylene = the mass of octafluoroisobutylene reacting with methanol / the mass of octafluoroisobutylene in the residual feed.

[0053] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering fluoroethers from hexafluoropropylene distillation residue, characterized in that, The method includes: S1, mixing hexafluoropropylene distillation residue with alcohol for reactive distillation to obtain a fluorinated ether mixture and a reactive distillation mixture gas; S2, subjecting the fluorinated ether mixture to a first distillation to obtain a fluorinated ether-alcohol azeotrope; S3, extracting the fluorinated ether-alcohol azeotrope to obtain a crude fluorinated ether product, and then subjecting the crude fluorinated ether product to a second distillation.

2. The method according to claim 1, wherein, The hexafluoropropylene distillation residue contains at least one of octafluorocyclobutane, octafluoroisobutene, octafluoron-butene, and a polymerization inhibitor; preferably, based on the total weight of octafluorocyclobutane, octafluoroisobutene, octafluoron-butene, and the polymerization inhibitor, the content of octafluorocyclobutane is 0.01-5 wt%, the content of octafluoroisobutene is 45-65 wt%, the content of octafluoron-butene is 30-50 wt%, and the content of the polymerization inhibitor is 0.01-0.5 wt%.

3. The method according to claim 1 or 2, wherein, In step S1, the alcohol is selected from C1-C4 alcohols, preferably at least one of methanol, ethanol and propanol; and / or, in step S1, the mass ratio of the alcohol to the hexafluoropropylene distillation residue is 0.1-5:1, preferably 1-3:

1.

4. The method according to claim 1 or 2, wherein, The conditions for the reactive distillation include: a temperature of 0-90°C and a pressure of 0-0.2 MPa; and / or, relative to a reactive distillation apparatus with a capacity of 300 kg / h, the processing rate of the hexafluoropropylene distillation residue is 100-500 kg / h.

5. The method according to claim 1, wherein, The conditions for the first distillation include: a temperature of 10-90℃ and a pressure of 0-0.2MPa; and / or, relative to a distillation apparatus with a throughput of 400kg / h, the processing rate of the fluorinated ether mixture in the first distillation is 100-700kg / h.

6. The method according to claim 1 or 5, wherein, The temperature of the reactive distillation is 5-10°C lower than that of the first distillation, preferably 5-8°C; and / or the pressure of the reactive distillation is 0.05-0.1 MPa higher than that of the first distillation.

7. The method according to claim 1 or 5, wherein, The method further includes: recovering the light components from the first distillation product and reusing them in the reactive distillation process of step (1).

8. The method according to claim 1, wherein, The extractant is selected from at least one of water, ketones and hydrocarbons; preferably, the mass ratio of the extractant to the fluoroether-alcohol azeotrope feed is 0.5-5:1, more preferably 1-3:

1.

9. The method according to claim 1 or 8, wherein, The extraction conditions include: a temperature of 10-50℃ and a pressure of 0-0.1MPa; and / or, relative to an extraction device with a throughput of 200kg / h, the extraction rate of the fluoroether-alcohol azeotrope is 50-300kg / h.

10. The method according to claim 1, wherein, The conditions for the second distillation include: a temperature of 30-90°C and a pressure of 0-0.1 MPa; and / or, relative to a distillation apparatus with a throughput of 200 kg / h, the crude fluoroether product processing rate of the second distillation is 50-400 kg / h; preferably, the extraction temperature is 5-15°C lower than that of the second distillation, more preferably 6-10°C.

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