Preparation method of perfluoroalkyl vinyl ether

Abstract

The invention belongs to the technical field of organic fluorine chemical industry, and particularly relates to a preparation method of perfluoroalkyl vinyl ether. Adding the compound catalyst into a tubular reactor, introducing hexafluoropropylene and O2, raising the temperature, controlling the pressure, and carrying out a continuous reaction to obtain a mixed gas of hexafluoropropylene oxide, carbonyl fluoride and trifluoroacetyl fluoride; introducing the mixed gas into a tubular reactor containing a compound catalyst, and carrying out addition reaction to obtain an acyl fluoride intermediate; and adding solid alkali metal carbonate into the tubular reactor, heating, introducing the acyl fluoride intermediate, carrying out a decarboxylation reaction to obtain a crude perfluoroalkyl vinyl ether product, and carrying out rectification purification to obtain the perfluoroalkyl vinyl ether. The compound catalyst is a homogeneous mixture of a difluoro ion solvent, strong acid and alkali metal fluoride. The tubular reactor and the compound catalyst cooperate to realize continuous preparation of the perfluoroalkyl vinyl ether, the conversion rate and selectivity are remarkably improved, and the method is suitable for industrial amplification.

Description

Technical Field

[0001] This invention belongs to the field of organofluorine chemical technology, specifically relating to a method for preparing perfluoroalkyl vinyl ethers. Background Technology

[0002] Perfluoroalkyl vinyl ethers (PAVEs) are a class of fluorinated monomers that can copolymerize with fluorinated olefins to obtain organic polymers with special properties. Representative PAVE products include perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), and perfluoropropyl vinyl ether (PPVE). Due to their unique structures, they can participate in polymerization as modifying monomers and have wide applications in the research of fluorinated compounds.

[0003] Currently, the main methods for synthesizing perfluoroalkyl vinyl ethers include pyrolysis, reduction, and fluorinated building block methods. Among these, catalytic pyrolysis is widely used, primarily employing aprotic polar solvents as solvents and alkali metal fluorides as catalysts, with the reaction carried out in a batch-feed reactor. Patent CN101817728A provides a method for producing hexafluoropropylene oxide and co-producing perfluorovinyl ethers using a batch reactor, yielding products PMVE, PEVE, and PPVE, but the product yield is low, and the yield of each batch is unstable.

[0004] Patent CN106146294A provides a method for preparing perfluoromethyl vinyl ethers using a polar aprotic solvent in the presence of a main catalyst and a phase catalyst. However, this method suffers from poor catalyst solubility, difficulty in solvent recovery, and low yield. Patent CN103724167A selects the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) as a co-catalyst, increasing catalyst solubility and improving yield, but still suffers from poor product stability.

[0005] In summary, although existing technologies provide multiple pathways for the synthesis of perfluoroalkyl vinyl ethers, they generally suffer from industrialization bottlenecks such as unstable yields, low catalyst efficiency, and difficulties in product separation. There is an urgent need to develop a process to improve these problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing perfluoroalkyl vinyl ethers. By combining a compound catalyst with a tubular reactor, the method solves the problems of mass transfer and stability in continuous fluorination, simplifies the process, and improves production efficiency.

[0007] The method for preparing the perfluoroalkyl vinyl ether of the present invention comprises the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas The compound catalyst was added to a tubular reactor, and hexafluoropropylene and O2 were introduced. The temperature and pressure were raised to carry out a continuous reaction to obtain a mixed gas of hexafluoropropylene oxide (HFPO), carbonyl fluoride (COF2), and trifluoroacetyl fluoride (CF3COF). The mass ratio of the compound catalyst added to hexafluoropropylene in the tubular reactor was 0.2:(2~3). (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) is passed into a tubular reactor containing a compound catalyst to carry out an addition reaction to obtain acyl fluoride intermediates: perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride and perfluoro-2-propoxypropionyl fluoride; wherein the mass ratio of the amount of compound catalyst added to the amount of mixed gas input is 1: (8.5~10). (3) Decarboxylation of acyl fluoride intermediate Solid alkali metal carbonates are added to a tubular reactor, and after heating, an acyl fluoride intermediate is introduced to carry out a decarboxylation reaction to obtain crude perfluoroalkyl vinyl ethers: perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether) (PPVE). (4) Separation and purification of crude perfluoroalkyl vinyl ether The crude perfluoroalkyl vinyl ether obtained in step (3) is purified by distillation in a distillation column to obtain the product. The composite catalyst is a homogeneous mixture of difluorinated ionic solvent, strong acid, and alkali metal fluoride.

[0008] The tubular reactor is equipped with a spiral static mixer.

[0009] The composite catalyst is a homogeneous mixture of a difluorinated ionic solvent, a strong acid, and an alkali metal fluoride in a molar ratio of 1:(0.1~0.5):(1~3).

[0010] The difluoroionic solvent is 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt: [CF3mim][(CF3SO2)2N], with the structural formula shown in Formula I below:

[0011] Formula I; The strong acid is sulfuric acid, and the alkali metal fluoride is potassium fluoride.

[0012] The preparation method of the 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt includes the following steps: a. Synthesis of 1-trifluoromethyl-3-methylimidazolium salt: First, toluene was added to a high-pressure reactor, followed by potassium carbonate and activated copper powder, and stirred for 2 hours. Then, N-methylimidazole was added. After the reaction was completed, excess trifluoromethyl iodine (CF3I) was bubbled through the reactor. The reaction was carried out under a nitrogen atmosphere at 80-100°C for 24 hours. After the reaction was completed, potassium carbonate and copper powder were removed by filtration, and toluene solvent was removed by rotary evaporation under reduced pressure to obtain a crude product. The crude product was dissolved in acetonitrile and recrystallized to obtain 1-trifluoromethyl-3-methylimidazole onium salt. b. Preparation of bis(trifluoromethanesulfonyl)imine salt: Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was dissolved in water to form an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide with a concentration of 1 mol / L; c. Synthesis of 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt: Dissolve 1-trifluoromethyl-3-methylimidazolium salt in a small amount of dichloromethane, and slowly add an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide under stirring. Stir the reaction for 4 hours, perform phase separation, and collect the organic phase. d. Drying and purification: The extracted organic phase ionic liquid was dried under high vacuum at 60°C to obtain 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt for later use.

[0013] The flow rate ratio of hexafluoropropylene and O2 in step (1) is (1~2):1.

[0014] The temperature and pressure control in step (1) is to raise the temperature to 150~180℃ and maintain the pressure at 0.3~0.5MPa. The residence time of the continuous reaction is 35~60min.

[0015] The reaction temperature of the addition reaction in step (2) is -10~10℃.

[0016] The mass ratio of the solid alkali metal carbonate and the acyl fluoride intermediate in step (3) is 1:(3.5~5).

[0017] The heating in step (3) is to raise the temperature to 180~210℃.

[0018] The distillation purification process in step (4) is as follows: pressure 0.2~0.35MPa, temperature 25~40℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a method for the continuous production of perfluoroalkyl vinyl ethers using a tubular reactor, which solves the problem of poor stability in traditional batch reactors. This invention improves the conversion rate of the product by optimizing the reaction temperature, pressure, and molar ratio of HFP and O2. The resulting mixture can be directly used as a raw material for the next reaction. Continuous feeding and discharging avoids material accumulation. Segmented temperature control increases product selectivity. Furthermore, the catalyst is less prone to agglomeration under continuous flow conditions. The tubular reactor operates in a closed manner, reducing the risk of HF volatilization. This method is suitable for industrial scale-up.

[0020] 2. The difluorinated ionic solvent [CF3mim][(CF3SO2)2N] used in the composite catalyst of the present invention has good fluorine compatibility, which dissolves KF to a greater extent and activates F⁻. Sulfuric acid enhances the electrophilicity of the substrate and weakens the binding between K⁺ and F⁻ through protonation. The three synergistically improve the reaction rate, increase the conversion rate of raw materials, and improve the product selectivity of perfluoroalkyl vinyl ethers.

[0021] 3. This invention solves the mass transfer and stability problems in continuous fluorination by combining a compound catalyst with a tubular reactor. The tubular reactor provides a stable and controllable ideal reaction environment for the efficient compound catalyst system, allowing its activity and selectivity to be maximized and maintained. Attached Figure Description

[0022] Figure 1 This is the NMR fluorine spectrum of the catalyst 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments.

[0024] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0025] The activated copper powder was 97 wt.% industrial-grade light copper oxide, purchased from Yongsheng Chemical Co., Ltd.

[0026] The preparation of 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt ([CF3mim][(CF3SO2)2N) includes the following steps: a. Synthesis of 1-trifluoromethyl-3-methylimidazolium salt: First, 1.3 kg of toluene was added to a 5 L high-pressure reactor, along with 50 g of potassium carbonate and 20 g of activated copper powder. The mixture was stirred at 150 r / min for 2 h. Then, the stirring speed was adjusted to 100 r / min, and 680 g of N-methylimidazole was added. After the reaction was completed, 1600 g of trifluoromethyl iodine (CF3I) was bubbled through the reactor. The mixture was stirred and reacted at 80-100 °C for 24 h under a nitrogen atmosphere. After the reaction was completed, the potassium carbonate and copper powder were removed by filtration, and the toluene solvent was removed by rotary evaporation under reduced pressure to obtain the crude product. The crude product was dissolved in acetonitrile and recrystallized to obtain 2041.6 g of 1-trifluoromethyl-3-methylimidazole onium salt. b. Preparation of bis(trifluoromethanesulfonyl)imine salt: 2106.58g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was dissolved in water to form an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide with a concentration of 1mol / L; c. Synthesis of 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt: Dissolve 1-trifluoromethyl-3-methylimidazolium salt in a small amount of dichloromethane (until completely dissolved), stir to 150 r / min, and slowly add an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide at a rate of 60 g / min. Stir the reaction for 4 h, perform phase separation, and collect the organic phase. d. Drying and purification: The extracted organic phase ionic liquid was dried under high vacuum at 60°C to obtain 3162.36 g of 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, which was then stored for later use. The NMR fluorine spectrum is shown below. Figure 1 As shown, the fluorine NMR spectrum data are as follows: 19F NMR spectrum, δ, ppm: -59.18 (3F, s, NCF3); -78.70 (6F, s, 2SO2CF3).

[0027] Example 1 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas 280g of the compound catalyst was added to a tubular reactor equipped with a spiral static mixer. Hexafluoropropylene and O2 were introduced, with the flow rates of both hexafluoropropylene and oxygen controlled at 70g / min. The temperature was raised to 150℃, the pressure was maintained at 0.3MPa, and the residence time was 40min. Gas phase analysis revealed that the product contained 50.2% hexafluoropropylene oxide (HFPO), 22.6% carbonyl fluoride (COF2), 24.5% trifluoroacetyl fluoride (CF3COF), and 2.7% hexafluoropropylene. (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) was passed into a tubular reactor containing 200g of compound catalyst and carried out an addition reaction at -10℃. 1700g of mixed gas was passed in to obtain acyl fluoride intermediates. Sampling and testing showed that perfluoro-2-methoxypropionyl fluoride accounted for 35.6%, perfluoro-2-ethoxypropionyl fluoride accounted for 33.2%, and perfluoro-2-propoxypropionyl fluoride accounted for 28.5%. (3) Decarboxylation of acyl fluoride intermediate 400g of potassium carbonate was added to a tubular reactor, the temperature was raised to 180℃, and 1400g of acyl fluoride intermediate was introduced. Samples were taken for quantitative analysis of the product, yielding crude perfluoroalkyl vinyl ether: perfluoro(methyl vinyl ether) (PMVE) accounted for 33.7%, perfluoro(ethyl vinyl ether) (PEVE) accounted for 30.4%, and perfluoro(propyl vinyl ether) (PPVE) accounted for 29.6%. (4) Separation and purification of crude perfluoroalkyl vinyl ether The crude perfluoroalkyl vinyl ether obtained in step (3) was fed into a distillation column. The pressure in the bottom of the column was maintained at 0.2 MPa. The products PMVE, PEVE and PPVE were collected sequentially at the top temperatures of 25℃, 29℃ and 35℃, with purities of 99.917%, 99.943% and 99.303%, respectively.

[0028] The composite catalyst is a homogeneous mixture of [CF3mim][(CF3SO2)2N, sulfuric acid, and potassium fluoride in a molar ratio of 1:0.1:1.

[0029] Example 2 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas 420g of the compound catalyst was added to a tubular reactor equipped with a spiral static mixer. Hexafluoropropylene and O2 were introduced, with the flow rate of hexafluoropropylene controlled at 140g / min and the flow rate of oxygen at 70g / min. The temperature was raised to 180℃, the pressure was maintained at 0.5MPa, and the residence time was 36min. A sample was taken for gas chromatography analysis. The results showed that the mixture contained 32.6% hexafluoropropylene oxide (HFPO), 42.5% carbonyl fluoride (COF2), 23.4% trifluoroacetyl fluoride (CF3COF), and 1.5% hexafluoropropylene (HFP). (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) was passed into a tubular reactor containing 200g of compound catalyst and carried out an addition reaction at 10°C. 2000g of mixed gas was then passed in to obtain an acyl fluoride intermediate. Samples were taken and tested: perfluoro-2-methoxypropionyl fluoride accounted for 40.5%, perfluoro-2-ethoxypropionyl fluoride accounted for 31.2%, and perfluoro-2-propoxypropionyl fluoride accounted for 26.8%. (3) Decarboxylation of acyl fluoride intermediate 400g of potassium carbonate was added to a tubular reactor, the temperature was raised to 210℃, and 2000g of acyl fluoride intermediate was introduced. Samples were taken for quantitative analysis of the product, yielding crude perfluoroalkyl vinyl ethers: perfluoro(methyl vinyl ether) (PMVE) accounted for 38.5%, perfluoro(ethyl vinyl ether) (PEVE) accounted for 29.9%, and perfluoro(propyl vinyl ether) (PPVE) accounted for 25.7%. (4) Separation and purification of crude perfluoroalkyl vinyl ether The crude perfluoroalkyl vinyl ether obtained in step (3) was fed into a distillation column. The pressure in the bottom of the column was maintained at 0.35 MPa. The products PMVE, PEVE and PPVE were collected sequentially at the top temperatures of 33℃, 37℃ and 40℃, respectively. The purity of the products was 99.992%, 99.976% and 99.996%, respectively.

[0030] The composite catalyst is a homogeneous mixture of [CF3mim][(CF3SO2)2N, sulfuric acid, and potassium fluoride in a molar ratio of 1:0.5:3.

[0031] Example 3 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas 350g of the compound catalyst was added to a tubular reactor equipped with a spiral static mixer. Hexafluoropropylene and O2 were introduced, with the flow rate of hexafluoropropylene controlled at 105g / min and the flow rate of oxygen at 70g / min. The temperature was raised to 170℃, the pressure was maintained at 0.4MPa, and the residence time was 50min. A sample was taken for gas phase analysis, and a mixed gas was obtained with 40.5% hexafluoropropylene oxide (HFPO), 32.2% carbonyl fluoride (COF2), 25.6% trifluoroacetyl fluoride (CF3COF), and 1.7% hexafluoropropylene (HFP). (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) was introduced into a tubular reactor containing 200g of compound catalyst and carried out an addition reaction at 0°C. After introducing 1800g of mixed gas, an acyl fluoride intermediate was obtained. The gas phase detection results were: perfluoro-2-methoxypropionyl fluoride accounted for 28.4%, perfluoro-2-ethoxypropionyl fluoride accounted for 39.2%, and perfluoro-2-propoxypropionyl fluoride accounted for 30.7%. (3) Decarboxylation of acyl fluoride intermediate 400g of potassium carbonate was added to a tubular reactor, the temperature was raised to 190℃, and 1800g of acyl fluoride intermediate was introduced. Samples were taken for quantitative analysis of the product, yielding crude perfluoroalkyl vinyl ether: perfluoro(methyl vinyl ether) (PMVE) accounted for 36.5%, perfluoro(ethyl vinyl ether) (PEVE) accounted for 34.8%, and perfluoro(propyl vinyl ether) (PPVE) accounted for 26.5%. (4) Separation and purification of crude perfluoroalkyl vinyl ether The crude perfluoroalkyl vinyl ether obtained in step (3) was fed into a distillation column. The pressure in the bottom of the column was maintained at 0.3 MPa. The products PMVE, PEVE and PPVE were collected sequentially at the top temperatures of 30℃, 34℃ and 38.5℃, with purities of 99.971%, 99.992% and 99.985%, respectively.

[0032] The composite catalyst is a homogeneous mixture of [CF3mim][(CF3SO2)2N, sulfuric acid, and potassium fluoride in a molar ratio of 1:0.25:1.5.

[0033] Example 4 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas 280g of the compounded catalyst was added to a tubular reactor equipped with a spiral static mixer. Hexafluoropropylene and O2 were introduced, with the flow rates of hexafluoropropylene and oxygen controlled at 70g / min. The temperature was raised to 210℃, the pressure was maintained at 0.3MPa, and the residence time was 40min. Samples were taken for gas phase analysis, and the composition was found to be 13.7% hexafluoropropylene oxide (HFPO), 60.2% carbonyl fluoride (COF2), 23.5% trifluoroacetyl fluoride (CF3COF), 1.8% hexafluoropropylene (HFP), and 0.8% carbon dioxide (CO2). (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) was introduced into a tubular reactor containing 200g of compound catalyst, followed by 1700g of mixed gas. An addition reaction was carried out at -10℃ to obtain an acyl fluoride intermediate. The gas phase detection results were: perfluoro-2-methoxypropionyl fluoride accounted for 17.5%, perfluoro-2-ethoxypropionyl fluoride accounted for 14.2%, and perfluoro-2-propoxypropionyl fluoride accounted for 16.7%. (3) Decarboxylation of acyl fluoride intermediate 400g of potassium carbonate was added to a tubular reactor, the temperature was raised to 180℃, and 1400g of acyl fluoride intermediate was introduced. Samples were taken for quantitative analysis of the product, yielding crude perfluoroalkyl vinyl ethers: perfluoro(methyl vinyl ether) (PMVE) accounted for 17.2%, perfluoro(ethyl vinyl ether) (PEVE) accounted for 13.5%, and perfluoro(propyl vinyl ether) (PPVE) accounted for 12.7%. The composite catalyst is a homogeneous mixture of [CF3mim][(CF3SO2)2N, sulfuric acid, and potassium fluoride in a molar ratio of 1:0.1:1.

[0034] Compared with Example 1, this example increased the reaction temperature, which increased the selectivity of carbonyl fluoride in the product. However, it was accompanied by the generation of a large amount of carbon dioxide, which reduced the selectivity of the final perfluoroalkyl vinyl ether product. The results show that excessively high reaction temperature can cause the product to crack and generate CO2 byproduct, thus resulting in a lower selectivity of the final product.

[0035] Example 5 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas 280g of the compounded catalyst was added to a tubular reactor equipped with a spiral static mixer. Hexafluoropropylene and O2 were introduced, with the flow rates of hexafluoropropylene and oxygen controlled at 70g / min. The temperature was raised to 130℃, the pressure was maintained at 0.3MPa, and the residence time was 40min. Samples were taken for gas phase analysis, and the composition was found to be 60.7% hexafluoropropylene oxide (HFPO), 17.2% carbonyl fluoride (COF2), 10.2% trifluoroacetyl fluoride (CF3COF), and 11.9% hexafluoropropylene (HFP).

[0036] Compared with Example 1, this example reduced the reaction temperature, which relatively increased the selectivity of HFPO in the product and decreased the conversion rate of hexafluoropropylene. This result indicates that reducing the reaction temperature will lead to incomplete reaction, reduced product selectivity, and affect the selectivity of the final perfluoroalkyl vinyl ether.

[0037] Comparative Example 1 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas 420g of the compound catalyst was added to a Hastelloy reactor. The flow rate of hexafluoropropylene was controlled at 140g / min, the flow rate of oxygen at 70g / min, the temperature was raised to 180℃, the pressure was maintained at 0.5MPa, and the residence time was 60min. A sample was taken for gas phase analysis, and the composition was found to be 22.7% hexafluoropropylene oxide (HFPO), 32.4% carbonyl fluoride (COF2), 22.5% trifluoroacetyl fluoride (CF3COF), and 22.4% hexafluoropropylene (HFP). (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) was introduced into a reactor containing 200g of compound catalyst, and 2000g of acyl fluoride mixed gas was introduced. An addition reaction was carried out at 10℃ to obtain an acyl fluoride intermediate. The gas phase detection results were: perfluoro-2-methoxypropionyl fluoride accounted for 16.3%, perfluoro-2-ethoxypropionyl fluoride accounted for 15.6%, and perfluoro-2-propoxypropionyl fluoride accounted for 17.7%. (3) Decarboxylation of acyl fluoride intermediate 400g of potassium carbonate was added to the decarboxylation reactor, the temperature was raised to 210℃, and 2000g of acyl fluoride intermediate was introduced. Samples were taken for quantitative analysis of the product, yielding crude perfluoroalkyl vinyl ether: perfluoro(methyl vinyl ether) (PMVE) accounted for 12.2%, perfluoro(ethyl vinyl ether) (PEVE) accounted for 13.1%, and perfluoro(propyl vinyl ether) (PPVE) accounted for 14.5%. The composite catalyst is a homogeneous mixture of [CF3mim][(CF3SO2)2N, sulfuric acid, and potassium fluoride in a molar ratio of 1:0.5:3.

[0038] Compared to Example 2, replacing the tubular reactors for the oxidation, addition, and decarboxylation reactions with batch reactors resulted in a decrease in the conversion rate of the product in the oxidation reaction and a decrease in the selectivity of the perfluoroalkyl vinyl ether product. The results show that the traditional batch reactor has a problem of uneven mass transfer, which leads to a decrease in the yield of the perfluoroalkyl vinyl ether product.

[0039] Comparative Example 2 The perfluoroalkyl vinyl ether is prepared by the following steps: (1) Oxidation of hexafluoropropylene (HFP) to prepare mixed gas A solution of 280 g potassium fluoride in tetraethylene glycol dimethyl ether (93.3 g / L) was added to a tubular reactor equipped with a spiral static mixer. Hexafluoropropylene and O2 were introduced, with the flow rates of both hexafluoropropylene and oxygen controlled at 70 g / min. The temperature was raised to 150 °C, the pressure maintained at 0.3 MPa, and the residence time was 40 min. Gas phase analysis revealed that the product contained 25.4% hexafluoropropylene oxide (HFPO), 14.7% carbonyl fluoride (COF2), 22.5% trifluoroacetyl fluoride (CF3COF), and 37.4% hexafluoropropylene. (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) was passed into a tubular reactor containing 200g of potassium fluoride in tetraethylene glycol dimethyl ether, and an addition reaction was carried out at -10℃. After 1700g of mixed gas was added, a sample was taken for testing, and the following intermediates of acyl fluoride were obtained: perfluoro-2-methoxypropionyl fluoride accounted for 15.2%, perfluoro-2-ethoxypropionyl fluoride accounted for 16.1%, and perfluoro-2-propoxypropionyl fluoride accounted for 17.4%; Compared with Example 1, replacing the compounded ionic liquid catalyst with a traditional polar protic solvent as the solvent and an alkali metal fluoride as the catalyst resulted in a decrease in the selectivity of each component of the mixed gas. This was because the traditional solvent catalyst system had insufficient solubility and activity, leading to a decrease in the selectivity of the final product.

[0040] Comparative Example 3 The perfluoroalkyl vinyl ether is prepared by the following steps: The [CF3mim][(CF3SO2)2N) in the composite catalyst was replaced with [BMIM]BF4, and the catalyst formulation was a homogeneous mixture of [BMIM]BF4, sulfuric acid, and potassium fluoride in a molar ratio of 1:0.1:1. The amount of composite catalyst was also replaced with 174g in an equimolar ratio. Preparation of mixed gas by oxidation of hexafluoropropylene (HFP) The experimental procedure was the same as step (1) in Example 1. The results of the mixed gas test were as follows: hexafluoropropylene oxide (HFPO) accounted for 14.2%, carbonyl fluoride (COF2) accounted for 17.8%, trifluoroacetyl fluoride (CF3COF) accounted for 14.3%, hexafluoropropylene accounted for 27.4%, and oxygen accounted for 26.3%.

[0041] Compared to Example 1, replacing the difluorinated ion catalyst with a conventional fluorinated ion catalyst significantly reduced the conversion rate and selectivity of the mixed gas.

Claims

1. A method for preparing a perfluoroalkyl vinyl ether, characterized in that, It is prepared by the following steps: (1) Oxidation of hexafluoropropylene to prepare mixed gas The compound catalyst was added to a tubular reactor, and hexafluoropropylene and O2 were introduced. The temperature and pressure were increased to carry out a continuous reaction to obtain a mixture of hexafluoropropylene oxide, carbonyl fluoride and trifluoroacetyl fluoride. (2) Preparation of acyl fluoride intermediates by addition of mixed gas The mixed gas obtained in step (1) is passed into a tubular reactor containing a composite catalyst to carry out an addition reaction to obtain acyl fluoride intermediates: perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride and perfluoro-2-propoxypropionyl fluoride. (3) Decarboxylation of acyl fluoride intermediate Solid alkali metal carbonates are added to a tubular reactor, and after heating, acyl fluoride intermediates are introduced to carry out a decarboxylation reaction to obtain crude perfluoroalkyl vinyl ethers: perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether). (4) Separation and purification of crude perfluoroalkyl vinyl ether The crude perfluoroalkyl vinyl ether obtained in step (3) is purified by distillation in a distillation column to obtain the product. The composite catalyst is a homogeneous mixture of difluorinated ionic solvent, strong acid, and alkali metal fluoride.

2. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The composite catalyst is a homogeneous mixture of a difluorinated ionic solvent, a strong acid, and an alkali metal fluoride in a molar ratio of 1:(0.1~0.5):(1~3).

3. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The difluoroionic solvent is 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt: [CF3mim][(CF3SO2)2N], with the structural formula shown in Formula I below: Formula I; The strong acid is sulfuric acid, and the alkali metal fluoride is potassium fluoride.

4. The method for preparing perfluoroalkyl vinyl ethers according to claim 3, characterized in that, The preparation method of the 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt includes the following steps: a. Synthesis of 1-trifluoromethyl-3-methylimidazolium salt: First, toluene was added to a high-pressure reactor, followed by potassium carbonate and activated copper powder, and then N-methylimidazole was added. After the reaction was completed, excess trifluoromethyl iodine was bubbled through the reactor. The reactor was heated and stirred under a nitrogen atmosphere. After the reaction was completed, the potassium carbonate and copper powder were removed by filtration, and the toluene solvent was removed by rotary evaporation under reduced pressure to obtain the crude product. The crude product was dissolved in acetonitrile and recrystallized to obtain 1-trifluoromethyl-3-methylimidazole onium salt. b. Preparation of bis(trifluoromethanesulfonyl)imine salt: Lithium bis(trifluoromethanesulfonyl)imide is dissolved in water to form an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide. c. Synthesis of 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt: 1-Trifluoromethyl-3-methylimidazolium salt was dissolved in dichloromethane, and an aqueous solution of lithium bis(trifluoromethanesulfonylimide) was added under stirring. The reaction was stirred, and phase separation was carried out to collect the organic phase. d. Drying and purification: The extracted organic phase ionic liquid was vacuum dried to obtain 1-trifluoromethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt for later use.

5. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The flow rate ratio of hexafluoropropylene and O2 in step (1) is (1~2):1, and the mass ratio of the amount of the compound catalyst added in step (1) to the mass of hexafluoropropylene is 0.2:(2~3).

6. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The temperature and pressure control in step (1) is to raise the temperature to 150~180℃ and maintain the pressure at 0.3~0.5MPa. The residence time of the continuous reaction is 35~60min.

7. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The reaction temperature of the addition reaction in step (2) is -10~10℃.

8. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The mass ratio of the solid alkali metal carbonate and the acyl fluoride intermediate in step (3) is 1:(3.5~5).

9. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The heating in step (3) is to raise the temperature to 180~210℃.

10. The method for preparing perfluoroalkyl vinyl ethers according to claim 1, characterized in that, The distillation purification process described in step (4) is as follows: pressure 0.2~0.35MPa, top temperature 25~40℃.

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