Preparation method of perfluoro-2-alkoxy propionyl fluoride and perfluoroalkyl vinyl ether

Abstract

The invention belongs to the field of preparation of ether substances, and particularly relates to a preparation method of perfluoro-2-alkoxy propionyl fluoride and perfluoroalkyl vinyl ether. The preparation method of the perfluoro-2-alkoxy propionyl fluoride comprises the following steps: carrying out addition reaction on acyl fluoride and hexafluoropropylene oxide in a polar aprotic solvent in the presence of an organic base catalyst, a phase transfer catalyst and a phase transfer cosolvent to prepare the perfluoro-2-alkoxy propionyl fluoride, the phase transfer cosolvent is selected from a hexafluoropropylene dipolymer, a hexafluoropropylene tripolymer or 1, 3-bis (trifluoromethyl) benzene. The method provided by the invention can effectively reduce the generation of HFPO polymer by-products, thereby improving the yield of the target product.

Description

Technical Field

[0001] The invention belongs to the field of preparation of ether substances, and specifically relates to a preparation method of perfluoro-2-alkoxypropionyl fluoride and perfluoroalkyl vinyl ether. Background Art

[0002] Hexafluoropropylene oxide is an important fluorine-containing intermediate. Due to the ring bond in its structure and the strong electron-withdrawing property of fluorine, its epoxy bond is active and can undergo nucleophilic reactions with a variety of reagents. There are more than 40 important downstream products, which are extremely valuable and important in fluorine chemical industry. There are many methods for preparing hexafluoropropylene oxide by oxidation of hexafluoropropylene, but in industry, the valuable process method is the molecular oxygen liquid phase oxidation method. The oxidation of hexafluoropropylene to prepare hexafluoropropylene oxide is a complicated process, and its products include hexafluoropropylene oxide, perfluoroacetyl fluoride, carbonyl fluoride, carbon dioxide and carbon powder. Theoretically, 1 mole of hexafluoropropylene can produce 1 mole of hexafluoropropylene oxide, but in the actual production process, for every 1 mole of hexafluoropropylene oxide produced, about 1.3 to 1.6 moles of hexafluoropropylene are consumed. The oxidation process of hexafluoropropylene is accompanied by a large number of by-products such as carbonyl fluoride and perfluoropropionyl fluoride (accounting for about 15 to 30% of the product, of which carbonyl fluoride accounts for 10 to 25%). During the post-treatment process of water washing and alkali washing of by-products, a large amount of fluorine-containing wastewater that is difficult to treat and highly corrosive is generated.

[0003] In short, the preparation of hexafluoropropylene oxide by the liquid phase oxidation of hexafluoropropylene consumes a lot of raw materials and has high environmental post-processing costs, so the production cost of hexafluoropropylene oxide remains high.

[0004] Perfluoromethyl vinyl ether (CF3OCF=CF2, PMVE for short) is an important monomer for the synthesis of fluororubber and fluoroplastics. The introduction of a small amount of PMVE into PTFE can make PTFE have the advantages of being meltable, resistant to cold flow and folding, and having good gloss; PMVE can be copolymerized with tetrafluoroethylene and vinylidene fluoride to synthesize fluoroether rubber with excellent low temperature resistance. PMVE is a highly valuable modified monomer, but the preparation of its synthetic raw material carbonyl fluoride involves many flammable, explosive, and toxic (such as tetrafluoroethylene, carbonyl fluoride, etc.) hazardous chemicals, and the synthesis conditions are also harsh, making its synthesis difficult and costly.

[0005] The Chinese invention patent with the authorization announcement date of March 18, 2015 and the authorization announcement number of CN103724167B discloses a green synthesis method of perfluoromethyl vinyl ether with high yield, which uses alkali metal fluoride, ionic liquid and polar solvent to prepare catalyst solution to efficiently prepare perfluoromethyl vinyl ether. The alkali metal fluoride is potassium fluoride or cesium fluoride. The reaction principle is that the metal ion of the alkali metal fluoride becomes a strong nucleophile and a strong base after polarization in a polar aprotic solvent, which strongly attacks the second carbon atom of hexafluoropropylene oxide, and the attacked hexafluoropropylene oxide is converted into a nucleophilic anion with strong electronegativity, which combines with carbonyl fluoride to form an intermediate 2-methoxypropionyl fluoride. In the actual reaction, the above hexafluoropropylene oxide is converted into acyl fluoride, and the acyl fluoride combines with the fluoride salt catalyst to form a nucleophilic anion, which will continue to attack the hexafluoropropylene oxide molecules to form polymers. Therefore, the reaction is more inclined to produce hexafluoropropylene oxide polymers rather than a single adduct, which leads to the formation of more hexafluoropropylene oxide polymers (HFPO) in the reaction product, thereby reducing the preparation efficiency of the intermediate 2-methoxypropionyl fluoride, and further reducing the synthesis efficiency of perfluoromethyl vinyl ether.

[0006] The Chinese invention patent application with the application publication date of November 23, 2016 and the application publication number of CN106146294A discloses a method for preparing perfluoro-2-methoxypropionyl fluoride, wherein carbonyl fluoride and hexafluoropropylene oxide react under the action of a main catalyst alkali metal fluoride and a phase transfer catalyst to prepare perfluoro-2-methoxypropionyl fluoride. The alkali metal fluoride is cesium fluoride, silver fluoride, potassium fluoride, lithium fluoride, etc., and the phase transfer catalyst can be a cyclic crown ether such as 18-crown-6 and 15-crown-5. Although the phase transfer catalyst is used in the reaction, the reaction properties of the alkali metal fluoride are not changed, and more HFPO polymers will still be produced. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing perfluoro-2-alkoxypropionyl fluoride, so as to solve the problem that more HFPO polymers are generated in the existing method and the product yield needs to be improved.

[0008] The second object of the present invention is to provide a method for preparing perfluoroalkyl vinyl ether to solve the problems of many by-products and low product yield in the existing method.

[0009] In order to achieve the above first purpose, the technical solution adopted by the present invention is:

[0010] A method for preparing perfluoro-2-alkoxypropionyl fluoride comprises the following steps: acyl fluoride and hexafluoropropylene oxide are subjected to addition reaction in a polar aprotic solvent in the presence of an organic base catalyst, a phase transfer catalyst and a phase transfer cosolvent to obtain perfluoro-2-alkoxypropionyl fluoride; the phase transfer cosolvent is selected from hexafluoropropylene dimer, hexafluoropropylene trimer or 1,3-bistrifluoromethylbenzene; and the alkoxy group in the perfluoro-2-alkoxypropionyl fluoride is methoxy, ethoxy or propoxy.

[0011] The reasons why the present invention improves the yield of perfluoro-2-alkoxypropionyl fluoride are as follows: first, an organic base catalyst is selected, whose alkalinity and nucleophilic attack ability are weaker than those of alkali metal fluorides polarized in polar aprotic solvents. After hexafluoropropylene oxide is attacked by a nucleophilic agent, it becomes an anion core, and its ability to attack hexafluoropropylene oxide again is limited, thereby avoiding the generation of hexafluoropropylene oxide polymers and improving the conversion rate of the addition reaction; second, the use of a phase transfer cosolvent and a phase transfer catalyst promotes the addition reaction of carbonyl fluoride with anions activated by the catalyst, thereby avoiding the addition product from continuing to attack new hexafluoropropylene oxide and reducing the generation of hexafluoropropylene oxide polymers. Based on the above reasons, the method of the present invention can effectively reduce the generation of HFPO polymer by-products, thereby improving the yield of the target product.

[0012] Preferably, the mass ratio of the polar aprotic solvent to the phase transfer cosolvent is (2-3):1.

[0013] Preferably, the organic base catalyst is selected from triethylamine, tetramethylethylenediamine, trimethylamine, tributylamine, and N,N-diethylbenzylamine; the mass of the organic base catalyst is (0.04-0.07)% of the mass of the polar aprotic solvent.

[0014] Preferably, the phase transfer catalyst is selected from 18-crown-6, 15-crown-5, dibenzo-18-crown-6 or dicyclohexane-18-crown-6; the phase transfer catalyst is (0.02-0.05)% of the mass of the polar aprotic solvent.

[0015] Preferably, the polar aprotic solvent is selected from tetrahydrofuran, 1,3-dioxolane, tert-butyl methyl ether or acetone.

[0016] More preferably, the water content of the polar aprotic solvent is 600-1200 ppm. The presence of a small amount of water in the polar aprotic solvent can further reduce the excessive nucleophilic attack ability of the catalyst.

[0017] Preferably, the pressure of the addition reaction is 0.1-0.3 MPa; the temperature of the addition reaction is 15-25° C.; and the time of the addition reaction is 1.5-3 h.

[0018] Preferably, the gas product obtained by liquid-phase oxidation of hexafluoropropylene is subjected to distillation to separate hexafluoropropylene oxide to obtain a distillation light component; the main components of the distillation light component are carbonyl fluoride, followed by trifluoroacetyl fluoride; the distillation light component is used as an acyl fluoride raw material to prepare perfluoro-2-alkoxypropionyl fluoride. In the process of preparing hexafluoropropylene oxide by liquid-phase oxidation of hexafluoropropylene, the traditional method is to treat the distillation light component as waste gas, which will produce fluorine-containing wastewater after treatment such as water washing and alkali washing, and the cost of environmental post-treatment is relatively high. The present invention utilizes the above-mentioned distillation light component as the reaction raw material of perfluoro-2-alkoxypropionyl fluoride, which not only realizes the rational utilization of elements, but also avoids environmental post-treatment.

[0019] Preferably, the mass proportion of carbonyl fluoride in the distillation light component is more than 80%, and the mass proportion of trifluoroacetyl fluoride is more than 10%; and perfluoro-2-methoxypropionyl fluoride is obtained by distillation after the addition reaction.

[0020] In order to achieve the above second purpose, the technical solution adopted by the present invention is:

[0021] A method for preparing perfluoroalkyl vinyl ether comprises the following steps: preparing perfluoro-2-alkoxypropionyl fluoride by the above method, and then performing decarboxylation and cracking to obtain perfluoroalkyl vinyl ether.

[0022] The preparation method of the perfluoroalkyl vinyl ether of the present invention has less by-products and high yield in preparing perfluoro-2-alkoxypropionyl fluoride, thereby effectively improving the reaction efficiency of the perfluoroalkyl vinyl ether and improving the product yield. DETAILED DESCRIPTION

[0023] The invention uses an acyl fluoride raw material and hexafluoropropylene oxide to carry out addition reaction in a polar aprotic solvent to prepare perfluoro-2-alkoxy propionyl fluoride, and the perfluoro-2-alkoxy propionyl fluoride is further decarboxylated and cracked to prepare perfluoroalkyl vinyl ether.

[0024] Taking carbonyl fluoride as an example, the reaction formula of the above addition reaction is:

[0025] COF2+CF3CFCF2O→CF3OCF(CF3)COF

[0026] The reaction equation for decarboxylation cleavage is:

[0027] CF3OCF(CF3)COF+Na2CO3→CF3OCF=CF2+2NaF+2CO2

[0028] The addition reaction uses an organic base catalyst, a phase transfer cosolvent and a phase transfer catalyst. The alkalinity and nucleophilic attack ability of the organic base catalyst are weaker than those of alkali metal fluorides such as potassium fluoride and cesium fluoride. After polarizing and attacking hexafluoropropylene oxide in a polar aprotic solvent, it forms an anionic core with weak nucleophilic attack ability. Combined with the use of a phase transfer cosolvent and a phase transfer catalyst, the occurrence of hexafluoropropylene oxide polymer side reactions is effectively avoided and the reaction yield is improved.

[0029] Here, the acyl fluoride raw materials such as carbonyl fluoride, trifluoroacetyl fluoride, pentafluoropropionyl fluoride, etc., respectively generate perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride, perfluoro-2-propoxypropionyl fluoride, and finally obtain perfluoromethyl vinyl ether PMVE, perfluoroethyl vinyl ether PEVE, perfluoropropyl vinyl ether PPVE and other perfluoroalkyl vinyl ether products. Based on the above reaction raw materials, it is not difficult to see that the acyl fluoride raw material can also be a mixed gas raw material containing carbonyl fluoride, trifluoroacetyl fluoride, pentafluoropropionyl fluoride, especially a mixed gas raw material with carbonyl fluoride, trifluoroacetyl fluoride, pentafluoropropionyl fluoride as the main components. This type of mixed gas raw material can appear in the form of industrial tail gas, and the above method of the present invention can be used to achieve high-value conversion of acyl fluoride.

[0030] The typical case of the above mixed gas raw material is the process of preparing hexafluoropropylene oxide by liquid phase oxidation of hexafluoropropylene, which is to react hexafluoropropylene with molecular oxygen (oxygen) in a solvent at a certain temperature and pressure to obtain a gas product containing hexafluoropropylene, hexafluoropropylene oxide, carbonyl fluoride and acetyl fluoride. In the above reaction process, the double bond of hexafluoropropylene is broken, and epoxidation and continuous oxidation cause most of the by-products in the product to be converted into carbonyl fluoride.

[0031] Specifically, perfluorooctane or perfluorocyclic ether can be selected as the solvent, and the molar ratio of hexafluoropropylene to oxygen is controlled to be 1.5 to 2.3: 1. The mass ratio of hexafluoropropylene to solvent is 5 to 15: 1, the reaction temperature is 110 to 130° C., and the reaction pressure is 1.0 to 2.3 MPa.

[0032] In some reaction situations, among the above gas products, by mass percentage, hexafluoropropylene oxide accounts for 65-70%, hexafluoropropylene accounts for 5-10%, trifluoroacetyl fluoride accounts for 3-5%, and carbonyl fluoride accounts for 15-20%. After separating hexafluoropropylene oxide by distillation, a distillation light component can be obtained, the main component of which is carbonyl fluoride and the secondary component is trifluoroacetyl fluoride. For example, it is convenient to obtain a distillation light component in which the mass proportion of carbonyl fluoride is more than 80% and the mass proportion of trifluoroacetyl fluoride is more than 10%. In some typical cases, among the distillation light components, the mass proportions of trifluoroacetyl fluoride, carbonyl fluoride, hexafluoropropylene oxide, and hexafluoropropylene are 12-13%, 84-86%, 1-2%, and 0.9-1.1%, respectively.

[0033] After the addition reaction is completed, the gas is exhausted and the liquid is separated to obtain a crude product; the crude product is distilled to obtain perfluoro-2-methoxypropionyl fluoride. The distillation can be carried out by atmospheric pressure distillation, with a reflux ratio of 0.4 to 0.5 and a distillation temperature of 55 to 60°C.

[0034] The above decarboxylation cracking process belongs to the prior art, and similar reaction steps are recorded in the Chinese invention patent with the authorization announcement date of March 18, 2015 and the authorization announcement number of CN103724167B. The essence of the reaction is that perfluoro-2-methoxypropionyl fluoride undergoes a salt-forming decarboxylation reaction (i.e., a decarboxylation cracking reaction) in the presence of a carbonate filler to obtain a perfluoromethyl vinyl ether product. The carbonate filler can be composed of carbonate and alkali metal fluoride, wherein the amount of alkali metal fluoride added is very small, which can be controlled at about 2% (e.g., 1% to 3%). The temperature of the salt-forming decarboxylation reaction can be controlled to 210 to 230°C.

[0035] Specifically, perfluoro-2-methoxypropionyl fluoride can be introduced into a fixed bed reactor filled with the carbonate filler to carry out the decarboxylation cleavage reaction.

[0036] The implementation process of the present invention is described in detail below in conjunction with specific examples. In the following examples, if otherwise specified, the raw materials used are all commercially available conventional raw materials; "%" are all mass percentages. Among them, hexafluoropropylene dimer CAS: 13429-24-8, hexafluoropropylene trimer CAS: 6792-31-0.

[0037] 1. Specific embodiments of the preparation method of perfluoro-2-alkoxypropionyl fluoride and perfluoroalkyl vinyl ether of the present invention

[0038] Example 1

[0039] The preparation method of the perfluoroalkyl vinyl ether of the present embodiment is described by taking perfluoromethyl vinyl ether as an example, and comprises the following steps:

[0040] (1) Preparation of perfluoro-2-methoxypropionyl fluoride

[0041] The process gas from the liquid phase oxidation of hexafluoropropylene to prepare hexafluoropropylene oxide is subjected to a rectification operation in a rectification system to obtain a rectification light component. The composition thereof is as follows: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide and 1.1% of hexafluoropropylene, as tested by gas chromatography.

[0042] A 10-liter stainless steel reactor was used as a reaction vessel, and vacuum was first applied, followed by the addition of 4.7 kg 1,3-dioxolane (water content 790 ppm), 1.9 kg hexafluoropropylene trimer, 3.3 g tetramethylethylenediamine and 1.6 g 18-crown ether-6, and the system temperature was controlled to be 18-20°C, and the stirring speed was 200 rpm. Hexafluoropropylene oxide and the rectification light component were simultaneously introduced into the reactor containing a catalyst, a phase transfer solvent and a phase transfer catalyst, and stirred and mixed, the molar ratio of hexafluoropropylene oxide to the total acyl fluoride in the rectification light component was 1.07:1, and the mass of the rectification light component introduced was 653 g in total; the reaction pressure was 0.13 MPa, and the reaction time was 2 h.

[0043] After the reaction was completed, stirring was stopped, the gas was discharged, and the liquid was separated to obtain 1.74 kg of a crude product, the composition of which was: 92.2% perfluoro-2-methoxypropionyl fluoride, 5% perfluoro-2-ethoxypropionyl fluoride, 2% hexafluoropropylene oxide dimer, and 0.8% hexafluoropropylene oxide trimer.

[0044] The yield is calculated based on the ratio of the actual mass of perfluoro-2-methoxypropionyl fluoride to the theoretical mass of perfluoro-2-methoxypropionyl fluoride. Considering that the raw materials and products will dissolve in the solvent and that vacuuming is required to exhaust the reaction gas, about 5% of the product will be lost. The actual calculated yield result is 1740*92.2% / (653*232 / 66)*84%*95%=87.6%.

[0045] The crude product was distilled to obtain perfluoro-2-methoxypropionyl fluoride with a purity of 99.0%. The distillation conditions were: atmospheric pressure distillation, reflux ratio of 0.5, and distillation temperature of 55°C.

[0046] (2) Preparation of perfluoromethyl vinyl ether

[0047] Perfluoro-2-methoxypropionyl fluoride is introduced into a fixed bed reactor filled with carbonate filler to perform salt-forming decarboxylation reaction at 230° C. to obtain crude perfluoromethyl vinyl ether. The carbonate filler is composed of sodium carbonate and sodium fluoride in a mass ratio of 98:2.

[0048] The crude perfluoromethyl vinyl ether is distilled to obtain a PMVE product with a purity of 99.9%. The distillation conditions are: low-temperature pressure distillation, pressure 0.2-0.3 MPa, reflux ratio 0.4-0.5, temperature -16--19°C.

[0049] On the basis of this embodiment, carbonyl fluoride, trifluoroacetyl fluoride or pentafluoropropionyl fluoride can be used as the acyl fluoride raw material, based on the same reaction principle, perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride, perfluoro-2-propoxypropionyl fluoride can be obtained accordingly, and then perfluoromethyl vinyl ether, perfluoroethyl vinyl ether and perfluoropropyl vinyl ether can be obtained through salt-forming decarboxylation reaction. The cost of the reaction raw materials is slightly higher, but it also has the characteristics of high reaction yield and less by-products.

[0050] Example 2

[0051] The preparation method of perfluoroalkyl vinyl ether in this embodiment refers to the reaction mode of Example 1, and the main process is as follows, and other matters not described are the same as those in Example 1.

[0052] (1) Preparation of perfluoro-2-methoxypropionyl fluoride

[0053] The composition of the distillation light component is: 12% of trifluoroacetyl fluoride, 86% of carbonyl fluoride, 1.1% of hexafluoropropylene oxide, and 0.9% of hexafluoropropylene.

[0054] A 10-liter stainless steel reactor was added with 5.6 kg 1,3-dioxolane (water content 1160 ppm), 2.7 kg 1,3-bistrifluoromethylbenzene, 3.8 g triethylamine, and 1.3 g 18-crown ether-6 as a solvent containing a catalyst, a phase transfer solvent, and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to the total acyl fluoride in the distillation light components was 1.07:1, and the mass of the distillation light components passed through was 685 g in total; the reaction pressure was 0.17 MPa, and the reaction time was 2 h.

[0055] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.87 kg of a crude product, which was composed of 90.2% perfluoro-2-methoxypropionyl fluoride, 6.1% perfluoro-2-ethoxypropionyl fluoride, 1.8% hexafluoropropylene oxide dimer, and 0.9% hexafluoropropylene oxide trimer. The yield was calculated based on the content of the crude product and perfluoro-2-methoxypropionyl fluoride, and the result was 85.7%.

[0056] The crude product was distilled under the distillation conditions of Example 1 to obtain perfluoro-2-methoxypropionyl fluoride with a purity of 99.0%.

[0057] (2) Preparation of perfluoromethyl vinyl ether

[0058] The salt-forming decarboxylation reaction was carried out in the manner of step (2) of Example 1 to obtain a crude product of perfluoromethyl vinyl ether, which was then distilled under the distillation conditions of Example 1 to obtain a PMVE product with a purity of 99.9%.

[0059] Example 3

[0060] The preparation method of perfluoroalkyl vinyl ether in this embodiment refers to the reaction mode of Example 1, and the main process is as follows, and other matters not described are the same as those in Example 1.

[0061] (1) Preparation of perfluoro-2-methoxypropionyl fluoride

[0062] The composition of the distillation light components is: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide, and 1.1% of hexafluoropropylene.

[0063] A 10-liter stainless steel reactor was added with 4.7 kg 1,3-dioxolane (water content 790 ppm), 1.9 kg hexafluoropropylene trimer, 3.3 g tetramethylethylenediamine, and 1.5 g 15-crown ether-5 as a solvent containing a catalyst, a phase transfer solvent, and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to the total acyl fluoride in the distillation light component was 1.07:1, and the mass of the distillation light component passed through was 660 g in total; the reaction pressure was 0.16 MPa, and the reaction time was 2 h.

[0064] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.76 kg of a crude product, which was composed of 88.3% perfluoro-2-methoxypropionyl fluoride, 7.9% perfluoro-2-ethoxypropionyl fluoride, 2.9% hexafluoropropylene oxide dimer, and 0.9% hexafluoropropylene oxide trimer. The yield was calculated based on the content of the crude product and perfluoro-2-methoxypropionyl fluoride, and the result was 83.9%.

[0065] The crude product was distilled under the distillation conditions of Example 1 to obtain perfluoro-2-methoxypropionyl fluoride with a purity of 99.0%.

[0066] (2) Preparation of perfluoromethyl vinyl ether

[0067] The salt-forming decarboxylation reaction was carried out in the same manner as step (2) of Example 1 to obtain a crude product of perfluoromethyl vinyl ether, which was then distilled to obtain a PMVE product with a purity of 99.9%.

[0068] Example 4

[0069] The preparation method of perfluoroalkyl vinyl ether in this embodiment refers to the reaction mode of Example 1, and the main process is as follows, and other matters not described are the same as those in Example 1.

[0070] (1) Preparation of perfluoro-2-methoxypropionyl fluoride

[0071] The composition of the distillation light components is: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide, and 1.1% of hexafluoropropylene.

[0072] A 10-liter stainless steel reactor was added with 4.7 kg acetone (water content 670 ppm), 1.8 kg hexafluoropropylene dimer, 3.3 g tetramethylethylenediamine, and 1.5 g 15-crown ether-5 as a solvent containing a catalyst, a phase transfer solvent, and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to the total acyl fluoride in the distillation light component was 1.07:1, and the mass of the distillation light component was 635 g in total; the reaction pressure was 0.15 MPa, and the reaction time was 2.5 h.

[0073] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.69 kg of a crude product, which was composed of 87.4% perfluoro-2-methoxypropionyl fluoride, 9.3% perfluoro-2-ethoxypropionyl fluoride, 2.7% hexafluoropropylene oxide dimer, and 0.6% hexafluoropropylene oxide trimer. The yield was calculated based on the crude product and the content of perfluoro-2-methoxypropionyl fluoride, and the result was 83.0%.

[0074] The crude product was distilled under the distillation conditions of Example 1 to obtain perfluoro-2-methoxypropionyl fluoride with a purity of 99.0%.

[0075] (2) Preparation of perfluoromethyl vinyl ether

[0076] The salt-forming decarboxylation reaction was carried out in the same manner as step (2) of Example 1 to obtain a crude product of perfluoromethyl vinyl ether, which was then distilled to obtain a PMVE product with a purity of 99.9%.

[0077] Example 5

[0078] The preparation method of perfluoroalkyl vinyl ether in this embodiment refers to the reaction mode of Example 1, and the main process is as follows, and other matters not described are the same as those in Example 1.

[0079] (1) Preparation of perfluoro-2-methoxypropionyl fluoride

[0080] The composition of the distillation light component is: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide, and 1.1% of hexafluoropropylene.

[0081] A 10-liter stainless steel reactor was added with 4.7 kg 1,3-dioxolane (water content 790 ppm), 1.8 kg hexafluoropropylene dimer, 3.5 g N,N-diethylbenzylamine, and 1.6 g 18-crown ether-6 as a solvent containing a catalyst, a phase transfer solvent, and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to the total acyl fluoride in the distillation light components was 1.07:1, and the mass of the distillation light components passed through was 657 g in total; the reaction pressure was 0.16 MPa, and the reaction time was 3.0 h.

[0082] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.75 kg of a crude product, which was composed of 89.6% perfluoro-2-methoxypropionyl fluoride, 7.7% perfluoro-2-ethoxypropionyl fluoride, 1.7% hexafluoropropylene oxide dimer, and 1.0% hexafluoropropylene oxide trimer. The yield was calculated based on the content of the crude product and perfluoro-2-methoxypropionyl fluoride, and the result was 85.1%.

[0083] The crude product was distilled under the distillation conditions of Example 1 to obtain perfluoro-2-methoxypropionyl fluoride with a purity of 99.0%.

[0084] (2) Preparation of perfluoromethyl vinyl ether

[0085] The salt-forming decarboxylation reaction was carried out in the same manner as step (2) of Example 1 to obtain a crude product of perfluoromethyl vinyl ether, which was then distilled to obtain a PMVE product with a purity of 99.9%.

[0086] Example 6

[0087] The preparation method of perfluoroalkyl vinyl ether in this embodiment refers to the reaction mode of Example 1, and the main process is as follows, and other matters not described are the same as those in Example 1.

[0088] The composition of the distillation light components is: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide, and 1.1% of hexafluoropropylene.

[0089] A 10-liter stainless steel reactor was added with 4.8 kg 1,3-dioxolane solvent (water content 230 ppm), 1.9 kg hexafluoropropylene trimer, 3.3 g tetramethylethylenediamine, and 1.6 g 18-crown ether-6 as a solvent containing a catalyst, a phase transfer solvent, and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to the total acyl fluoride in the distillation light component was 1.07:1, and the mass of the distillation light component passed through was 570 g in total; the reaction pressure was 0.19 MPa, and the reaction time was 2.5 h.

[0090] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.52 kg of a crude product, which was composed of 77.5% perfluoro-2-methoxypropionyl fluoride, 11.7% perfluoro-2-ethoxypropionyl fluoride, 9.8% hexafluoropropylene oxide dimer, and 1.0% hexafluoropropylene oxide trimer. The yield was calculated based on the content of the crude product and perfluoro-2-methoxypropionyl fluoride, and the result was 73.6%.

[0091] 2. Comparison

[0092] Comparative Example 1

[0093] The preparation method of perfluoroalkyl vinyl ether in this comparative example refers to the reaction mode of Example 1, without using a phase transfer catalyst and a phase transfer cosolvent. The main process is as follows, and other matters not described are the same as those in Example 1.

[0094] The composition of the distillation light component is the same as that of Example 2, specifically: 12% of trifluoroacetyl fluoride, 86% of carbonyl fluoride, 1.1% of hexafluoropropylene oxide, and 0.9% of hexafluoropropylene.

[0095] A 10-liter stainless steel reactor was added with 7.8 kg 1,3-dioxolane (water content 1160 ppm) and 3.3 g tetramethylethylenediamine as a solvent containing a catalyst; the molar ratio of hexafluoropropylene oxide to total acyl fluoride in the distillation light components was 1.07:1, and the mass of the distillation light components passed through was 553 g in total; the reaction pressure was 0.21 MPa, and the reaction time was 2 h.

[0096] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.51 kg of a crude product, which was composed of 78.2% perfluoro-2-methoxypropionyl fluoride, 17.1% perfluoro-2-ethoxypropionyl fluoride, 3.7% hexafluoropropylene oxide dimer, and 1.0% hexafluoropropylene oxide trimer. The yield was calculated based on the crude product and the content of perfluoro-2-methoxypropionyl fluoride, and the result was 74.3%.

[0097] Comparative Example 2

[0098] The preparation method of perfluoroalkyl vinyl ether in this comparative example refers to the reaction mode of Example 1, and no phase transfer cosolvent is used. The main process is as follows, and other matters not described are the same as those in Example 1.

[0099] The composition of the distillation light component is the same as that in Example 1, specifically: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide, and 1.1% of hexafluoropropylene.

[0100] A 10-liter stainless steel reactor was added with 7.8 kg 1,3-dioxolane (water content 1160 ppm), 3.3 g tetramethylethylenediamine, and 1.6 g 18-crown ether-6 as a solvent containing a catalyst and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to total acyl fluoride in the distillation light components was 1.07:1, and the mass of the distillation light components passed through was 532 g in total; the reaction pressure was 0.23 MPa, and the reaction time was 2.5 h.

[0101] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.42 kg of a crude product, which was composed of 74.8% perfluoro-2-methoxypropionyl fluoride, 18.7% perfluoro-2-ethoxypropionyl fluoride, 5.8% hexafluoropropylene oxide dimer, and 0.7% hexafluoropropylene oxide trimer. The yield was calculated based on the content of the crude product and perfluoro-2-methoxypropionyl fluoride, and the result was 71.1%.

[0102] Comparative Example 3

[0103] The preparation method of perfluoroalkyl vinyl ether in this comparative example refers to the reaction mode of Example 1, uses potassium fluoride as a catalyst and does not use a phase transfer cosolvent. The main process is as follows, and other matters not described are the same as those in Example 1.

[0104] The composition of the distillation light component is the same as that in Example 1, specifically: 13% of trifluoroacetyl fluoride, 84% of carbonyl fluoride, 1.9% of hexafluoropropylene oxide, and 1.1% of hexafluoropropylene.

[0105] A 10-liter stainless steel reactor was added with 7.8 kg 1,3-dioxolane solvent (water content 1160 ppm), 3.3 g potassium fluoride, and 1.6 g 18-crown ether-6 as a solvent containing a catalyst and a phase transfer catalyst; the molar ratio of hexafluoropropylene oxide to total acyl fluoride in the distillation light component was 1.07:1, and the mass of the distillation light component passed through was 499 g in total; the reaction pressure was 0.29 MPa, and the reaction time was 3 h.

[0106] After the reaction was completed, stirring was stopped, gas was discharged, and liquid was separated to obtain 1.33 kg of a crude product, which was composed of 69.4% perfluoro-2-methoxypropionyl fluoride, 17.1% perfluoro-2-ethoxypropionyl fluoride, 10.3% hexafluoropropylene oxide dimer, and 3.2% hexafluoropropylene oxide trimer. The yield was calculated based on the crude product and the content of perfluoro-2-methoxypropionyl fluoride, and the result was 65.9%.

[0107] The above experiments show that the present invention uses a new catalytic system, a phase transfer catalyst and a phase transfer cosolvent, reduces the formation of hexafluoropropylene oxide polymers, improves the product yield, and can effectively promote the economy and environmental protection of the industrial production of perfluoro-2-alkoxypropionyl fluoride and perfluoroalkyl vinyl ether, and has good economic and social benefits.

Claims

1. A method for preparing perfluoro-2-alkoxypropionyl fluoride, characterized in that: The following steps are involved: Acyl fluoride and hexafluoropropylene oxide are subjected to addition reaction in a polar aprotic solvent in the presence of an organic base catalyst, a phase transfer catalyst and a phase transfer cosolvent to prepare perfluoro-2-alkoxypropionyl fluoride; the phase transfer cosolvent is selected from hexafluoropropylene dimer, hexafluoropropylene trimer or 1,3-bistrifluoromethylbenzene; the alkoxy group in the perfluoro-2-alkoxypropionyl fluoride is methoxy, ethoxy or propoxy.

2. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to claim 1, characterized in that: The mass ratio of the polar aprotic solvent to the phase transfer cosolvent is (2-3):

1.

3. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to claim 1, characterized in that: The organic base catalyst is selected from triethylamine, tetramethylethylenediamine, trimethylamine, tributylamine, and N,N-diethylbenzylamine; the mass of the organic base catalyst is (0.04-0.07)% of the mass of the polar aprotic solvent.

4. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to claim 1, characterized in that: The phase transfer catalyst is selected from 18-crown-6, 15-crown-5, dibenzo-18-crown-6 or dicyclohexane-18-crown-6; the mass of the polar aprotic solvent of the phase transfer catalyst is (0.02-0.05)%.

5. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to any one of claims 1 to 4, characterized in that: The polar aprotic solvent is selected from tetrahydrofuran, 1,3-dioxolane, tert-butyl methyl ether or acetone.

6. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to claim 5, characterized in that: The water content of the polar aprotic solvent is 600-1200 ppm.

7. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to any one of claims 1 to 4, characterized in that: The pressure of the addition reaction is 0.1-0.3 MPa; the temperature of the addition reaction is 15-25° C.; and the time of the addition reaction is 1.5-3 h.

8. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to any one of claims 1 to 4, characterized in that: The gas product obtained by liquid phase oxidation of hexafluoropropylene is subjected to distillation to separate hexafluoropropylene oxide to obtain a distillation light component; the main component of the distillation light component is carbonyl fluoride, followed by trifluoroacetyl fluoride; the distillation light component is used as an acyl fluoride raw material to prepare perfluoro-2-alkoxypropionyl fluoride.

9. The method for preparing perfluoro-2-alkoxypropionyl fluoride according to claim 8, characterized in that: The mass proportion of carbonyl fluoride in the distillation light component is more than 80%, and the mass proportion of trifluoroacetyl fluoride is more than 10%; after the addition reaction, perfluoro-2-methoxypropionyl fluoride is obtained by distillation.

10. A method for preparing perfluoroalkyl vinyl ether, characterized in that: The method comprises the following steps: preparing perfluoro-2-alkoxypropionyl fluoride by the method described in any one of claims 1 to 9, and then performing decarboxylation and cleavage to obtain perfluoroalkyl vinyl ether.