Preparation method of methyl methoxytetrafluoropropionate

Abstract

The invention belongs to the technical field of preparation of fluorine-containing fine chemicals, and particularly relates to a preparation method of methyl methoxytetrafluoropropionate, which comprises the following steps: adding methanol, dimethyl carbonate and imidazolium salt basic ionic liquid into a reaction kettle, continuously introducing tetrafluoroethylene, keeping the system pressure stable, and carrying out addition reaction; and after the reaction is finished, cooling the reaction material, distilling and rectifying to obtain the product methyl methoxytetrafluoropropionate. According to the preparation method of the methyl methoxy tetrafluoropropionate, methanol, dimethyl carbonate and tetrafluoroethylene are taken as raw materials, addition reaction is carried out in the presence of the imidazolium salt basic ionic liquid catalyst, the method has the advantages of high selectivity, easy reaction control and catalyst recoverability, the purity of the prepared methyl methoxy tetrafluoropropionate is 99.0-99.7%, the yield is 90.0-98.0%, and the method is suitable for industrial production. The product purity and yield are obviously improved, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of fluorine-containing fine chemicals, and in particular relates to a method for preparing methyl methoxytetrafluoropropionate. Background Art

[0002] Methyl methoxytetrafluoropropionate (2,2,3,3-tetrafluoro-3-methoxypropionate, molecular formula C5H6F4O3, molecular weight 190.09) is an important fluorine chemical raw material. It is mainly used as a key intermediate for the synthesis of perfluorocarboxylic acid resins. It can be further used to synthesize perfluorocarboxylic acid monomers for perfluoro ion membranes. It is also an important raw material for the production of perfluoro or partially fluorinated vinyl ethers. It is also used in the production of adhesives, dyes, pharmaceutical intermediates, fluorinated polymers, etc. It is also used as a solvent and is a special fluorine-containing fine chemical. In 1961, Du Pont of the United States first synthesized methyl methoxytetrafluoropropionate. Due to its special structure, people attach great importance to its synthesis and application research. The preparation of functional perfluorocarboxylic acid monomers and perfluorocarboxylic acid resins using this substance as raw materials has laid a solid foundation for the preparation and application of perfluoro ion membranes for chlor-alkali.

[0003] U.S. Patent No. 2,988,537 discloses the use of fluorinated olefin compounds with CX2=CX2 to prepare carbonates, aldehydes, and ketone compounds containing fluorinated aliphatic ethers. This method uses fluorinated olefins with CX2=CX2 to obtain a series of alkoxy fluorinated carbonates, aldehydes, or ketone compounds. The reaction has many byproducts and the yield is not high. U.S. Patent No. 5,235,094 introduces a method for preparing fluorinated alkoxy carbonates (R1O-CX2CX2-COOR2). This method has a high selectivity, but the yield is unstable, between 39% and 93%, and it is not easy to produce continuously.

[0004] Chinese patent 201010011848.6 discloses a method for preparing β-methoxytetrafluoropropyl ester, wherein dimethyl carbonate is dissolved in a solvent, sodium methoxide is added, and the mixture is evacuated, and then tetrafluoroethylene monomer is continuously introduced for reaction. After the feeding is completed, concentrated sulfuric acid is added to the reaction system to continue the reaction, and finally β-methoxytetrafluoropropyl ester is obtained by suction filtration and rectification. In this synthetic route, the amount of sodium methoxide used is large and cannot be reused. After the reaction is completed, acid neutralization is required. Acid-base treatment will corrode the reactor and equipment pipelines, generate a large amount of waste salt and wastewater, and increase the separation step. In addition, the neutralization process is obviously exothermic, increases side reactions, affects the reaction purity, and is difficult to further purify to obtain a product with higher purity.

[0005] The above production methods are all very restrictive, and the reaction process of the synthetic route is easy to control, but the reaction is prone to produce more by-products, and the reaction requirements are relatively harsh. Therefore, it is necessary to develop a synthetic technology for methyl methoxytetrafluoropropionate with higher yield, more environmental protection and cost saving. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a method for preparing methyl methoxytetrafluoropropionate, which uses methanol, dimethyl carbonate and tetrafluoroethylene as raw materials, and uses imidazole ionic liquid as catalyst and solvent, so that the yield of methyl methoxytetrafluoropropionate is further improved, and the problems of low catalyst recovery rate and easy corrosion of equipment are avoided.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a method for preparing methyl methoxytetrafluoropropionate, comprising the following steps:

[0009] Methanol, dimethyl carbonate and imidazole salt alkaline ionic liquid are added into a reaction kettle, tetrafluoroethylene is continuously introduced, the system pressure is maintained stable, and an addition reaction is performed; after the reaction is completed, the reaction materials are cooled, and the product methoxytetrafluoropropionic acid methyl ester is obtained through distillation and rectification.

[0010] In some embodiments, the molar ratio of methanol to tetrafluoroethylene is (1-3): (2-5), and the molar ratio of dimethyl carbonate to tetrafluoroethylene is (2-5): (1-3). In some preferred embodiments, the molar ratio of methanol to tetrafluoroethylene is (0.9-1): 1, and the molar ratio of dimethyl carbonate to tetrafluoroethylene is (1-1.2): 1.

[0011] In some embodiments, the molar ratio of tetrafluoroethylene to imidazolium salt alkaline ionic liquid is (3-8): (2-5). In some preferred embodiments, the molar ratio of tetrafluoroethylene to imidazolium salt alkaline ionic liquid is 1: (0.3-0.8).

[0012] In some embodiments, the imidazolium salt alkaline ionic liquid includes one or more of [BMIM][OH], [BMIM][NTf2], [EMIM][IM], [EMIM][PF6], and [BTMG][OH].

[0013] In some of the embodiments, the imidazolium salt alkaline ionic liquid includes a newly prepared imidazolium salt alkaline ionic liquid and a recycled and reused imidazolium salt alkaline ionic liquid.

[0014] In some embodiments, the operation of recovering the imidazole salt alkaline ionic liquid is: washing the distillation residue after distillation and vacuum drying. Specifically, the vacuum drying temperature is 60-80° C. and the time is 8-15 hours.

[0015] In some embodiments, the temperature of the addition reaction is -20 to 60°C, the time is 1 to 10 hours, and the pressure is -0.098 to 0.05 MPa. In some preferred embodiments, the temperature of the addition reaction is 10 to 20°C, the time is 2 to 5 hours, and the pressure is 0.01 to 0.05 MPa.

[0016] In some embodiments, the oxygen content in the system is less than 20 ppm.

[0017] In some of the embodiments, before tetrafluoroethylene is introduced, high-purity nitrogen is used for replacement three times to make the oxygen content in the system lower than 20 ppm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The method for preparing methyl methoxytetrafluoropropionate of the present invention uses methanol, dimethyl carbonate and tetrafluoroethylene as raw materials, and performs addition reaction in the presence of an imidazole salt alkaline ionic liquid catalyst. The method has the advantages of high selectivity, easy reaction control and recoverable catalyst. The purity of the prepared methyl methoxytetrafluoropropionate is 99.0-99.7%, and the yield is 90.0-98.0%. The purity and yield of the product are significantly improved, and the method is suitable for industrial production.

[0020] (2) The present invention uses imidazolium salt alkaline ionic liquid as a catalyst, which has functional groups and thus has excellent catalytic activity, selectivity and stability, which is beneficial to the formation of the target product methyl methoxytetrafluoropropionate, thereby improving the reaction yield; in addition, the imidazolium salt alkaline ionic liquid also acts as a solvent, which can dissolve polar and non-polar compounds, and can increase the solubility of reactants and intermediates, thereby increasing the reaction rate and selectivity; at the same time, the imidazolium salt alkaline ionic liquid is also non-volatile, which can prevent the release of harmful vapors, making the reaction safer and more environmentally friendly.

[0021] (3) The preparation method of methyl methoxytetrafluoropropionate of the present invention uses imidazole salt alkaline ionic liquid as a catalyst. Compared with the conventional preparation process using sodium methoxide as a catalyst for addition reaction during the preparation process, it avoids the problems of low catalyst recovery rate and easy corrosion of equipment; at the same time, the reaction process does not generate a large amount of waste salt and waste liquid, and the treatment is simple and environmentally friendly; the imidazole salt alkaline ionic liquid catalyst of the present invention can be reused many times, the catalyst utilization rate is high, and the production cost is greatly reduced. DETAILED DESCRIPTION

[0022] The experimental methods in the following examples of the present invention, where no specific conditions are specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0023] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0026] Example 1

[0027] In a 10-liter autoclave equipped with a stirrer, cooling coil, temperature and pressure display instrument, 640 g (20 mol) of methanol, 2000 g (22.2 mol) of dimethyl carbonate and 2083 g of [BMIM][OH] were added, and the reaction system was replaced with high-purity nitrogen three times to make the oxygen content in the reaction system lower than 20 ppm. The temperature of the autoclave was controlled to 10° C., tetrafluoroethylene was added to the autoclave to 0.05 MPa, and when the pressure dropped to 0.01 MPa, tetrafluoroethylene was added to maintain the pressure, and the reaction pressure was kept at 0.04-0.05 MPa, and the reaction temperature was kept between 10 and 20° C. After the reaction for 4 hours, 2000 g (20 mol) of tetrafluoroethylene was consumed cumulatively, and the reaction material was cooled, and 3700 g (19.47 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester was obtained after distillation and rectification, with a yield of 97.4% and a purity of 99.5%. The residual liquid after distillation was washed and vacuum dried, and the imidazole salt alkaline ionic liquid was recovered for recycling. A total of 1697 g of [BMIM][OH] was recovered, with a recovery rate of 81.5%.

[0028] Example 2

[0029] In a 10-liter autoclave with stirring, cooling coils, temperature and pressure display instruments, 640 g (20 mol) of methanol, 2000 g (22.2 mol) of dimethyl carbonate and 4100 g of [BMIM][NTf2] were added, and the oxygen content in the reaction system was lower than 20 ppm after replacement with high-purity nitrogen three times. The temperature of the autoclave was controlled to 10° C., tetrafluoroethylene was added to the autoclave to 0.05 MPa, and when the pressure dropped to 0.01 MPa, tetrafluoroethylene was added to maintain the pressure, and the reaction pressure was kept at 0.04-0.05 MPa, and the reaction temperature was kept between 10 and 20° C. After reacting for 5 hours, 2050 g (20.5 mol) of tetrafluoroethylene was consumed cumulatively, and the reaction materials were cooled, and 3768 g (19.83 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester was obtained after distillation and rectification, with a yield of 96.7% and a purity of 99.3%. The residual liquid after distillation was washed and vacuum dried, and the imidazole salt alkaline ionic liquid was recovered for recycling. A total of 3376 g of [BMIM][NTf2] was recovered, with a recovery rate of 82.3%.

[0030] Example 3

[0031] In a 10-liter high-pressure reactor equipped with a stirrer, cooling coil, temperature and pressure display instrument, 640 g (20 mol) of methanol, 2000 g (22.2 mol) of dimethyl carbonate and 2617 g of [EMIM][IM] were added, and the reaction system was replaced with high-purity nitrogen three times to make the oxygen content in the reaction system lower than 20 ppm. The temperature of the reactor was controlled to 10° C., tetrafluoroethylene was added to the reactor to 0.05 MPa, and when the pressure dropped to 0.01 MPa, tetrafluoroethylene was added to maintain the pressure, and the reaction pressure was kept at 0.04-0.05 MPa, and the reaction temperature was kept between 10 and 20° C. After the reaction for 4 hours, 2070 g (20.7 mol) of tetrafluoroethylene was consumed cumulatively, and the reaction material was cooled, and 3844 g (20.23 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester was obtained after distillation and rectification, with a yield of 97.7% and a purity of 99.6%. The residual liquid after distillation was washed and vacuum dried, and the imidazole salt alkaline ionic liquid was recovered for recycling. A total of 2157 g of [BTMG][OH] was recovered, with a recovery rate of 82.4%.

[0032] Example 4

[0033] The difference between this embodiment and embodiment 1 is that the imidazolium salt alkaline ionic liquid is [BMIM][OH] which is recycled after being used once and is reused, and the rest is the same as embodiment 1. Methyl methoxytetrafluoropropionate with a yield of 97.2% and a purity of 99.7% is obtained, and the recovery rate of the imidazolium salt alkaline ionic liquid is 84.0%.

[0034] Example 5

[0035] The difference between this embodiment and embodiment 1 is that the imidazolium salt alkaline ionic liquid is [BMIM][OH] recycled after three times, and the rest is the same as embodiment 1. Methyl methoxytetrafluoropropionate with a yield of 96.9% and a purity of 99.4% is obtained, and the recovery rate of the imidazolium salt alkaline ionic liquid is 84.3%.

[0036] Example 6

[0037] The difference between this embodiment and embodiment 1 is that the imidazolium salt alkaline ionic liquid is [BMIM][OH] recycled after 10 cycles, and the rest is the same as embodiment 1. Methyl methoxytetrafluoropropionate with a yield of 96.5% and a purity of 99.5% is obtained, and the recovery rate of the imidazolium salt alkaline ionic liquid is 79.9%.

[0038] Example 7

[0039] The difference between this embodiment and embodiment 1 is that the temperature of the reactor is controlled to 25°C, the reaction temperature is between 25 and 30°C, and the rest is the same as embodiment 1. Methyl methoxytetrafluoropropionate with a yield of 96.8% and a purity of 99.6% is obtained, and the recovery rate of the imidazole salt alkaline ionic liquid is 84.5%.

[0040] Example 8

[0041] The difference between this embodiment and embodiment 1 is that the temperature of the reactor is controlled to 50°C, the reaction temperature is between 50 and 60°C, and the rest is the same as embodiment 1. Methyl methoxytetrafluoropropionate with a yield of 93.1% and a purity of 99.3% is obtained, and the recovery rate of the imidazole salt alkaline ionic liquid is 81.6%.

[0042] Example 9

[0043] The difference between this embodiment and embodiment 1 is that the reaction kettle is temperature controlled to -20°C, the reaction temperature is between -20 and 0°C, and the rest is the same as embodiment 1. Methyl methoxytetrafluoropropionate with a yield of 92.9% and a purity of 99.1% is obtained, and the recovery rate of the imidazole salt alkaline ionic liquid is 86.9%.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that 2083g [BMIM][OH] is replaced with 1079g sodium methoxide and 1440g solvent tetrahydrofuran, and no methanol is added, and 979g concentrated sulfuric acid is added after the reaction kettle synthesis step is completed for acid neutralization. The specific steps are as follows:

[0046] In a 10-liter high-pressure reactor equipped with stirring, cooling coils, temperature and pressure display instruments, 2000 g of dimethyl carbonate and 1440 g of tetrahydrofuran were added, and then 1079 g of sodium methoxide was added thereto. The gas was replaced three times with high-purity nitrogen to make the oxygen content in the reaction system lower than 20 ppm. The temperature of the reactor was controlled to 10°C, and tetrafluoroethylene was filled into the reactor to 0.05 MPa. When the pressure dropped to 0.01 MPa, tetrafluoroethylene was added to maintain the pressure, and the reaction pressure was kept at 0.04-0.05 MPa and the reaction temperature was kept between 10 and 20°C. After 4 hours of reaction, a total of 1980 g (19.8 mol) of tetrafluoroethylene was consumed. 979 g of 98% concentrated sulfuric acid was added to the reactor for acid neutralization. The neutralized reaction mass was cooled and 3296 g (17.35 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester was obtained after distillation and rectification. The yield was 87.6% and the purity was 98.7%.

[0047] Comparative Example 2

[0048] The difference between this comparative example and comparative example 1 is that the temperature of the reactor is controlled to 25°C, the reaction temperature is between 25 and 30°C, and the other conditions are the same as comparative example 1. Methyl methoxytetrafluoropropionate is obtained with a yield of 81.1% and a purity of 98.3%.

[0049] Comparative Example 3

[0050] The difference between this comparative example and Example 1 is that the imidazolium salt alkaline ionic liquid [BMIM][OH] is replaced by a quaternary ammonium salt alkaline ionic liquid [N2,2,2,2][OH] (tetraethylammonium hydroxide), and the specific steps are as follows:

[0051] In a 10-liter autoclave equipped with a stirrer, cooling coil, temperature and pressure display instrument, add 640 g (20 mol) of methanol, 2000 g (22.2 mol) of dimethyl carbonate and 2061 g of [N2,2,2,2][OH], replace with high-purity nitrogen three times to make the oxygen content in the reaction system lower than 20 ppm, control the temperature of the autoclave to 10°C, fill the autoclave with tetrafluoroethylene to 0.05 MPa, and when the pressure drops to 0.01 MPa, add tetrafluoroethylene to maintain the pressure, keep the reaction pressure at 0.04-0.05 MPa, and the reaction temperature at 10-20°C. After 4 hours of reaction, the cumulative consumption of tetrafluoroethylene is 2100 g (21 mol), the reaction material is cooled, and after distillation and rectification, 3579 (18.84 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester is obtained, with a yield of 89.7% and a purity of 99.2%. The distillate after distillation was washed and vacuum dried to recover the quaternary ammonium salt ionic liquid. A total of 1791 g of [N2,2,2,2][OH] was recovered, with a recovery rate of 86.9%.

[0052] Comparative Example 4

[0053] The difference between this comparative example and Example 1 is that the imidazolium salt alkaline ionic liquid [BMIM][OH] is replaced with a quaternary phosphonium salt alkaline ionic liquid (tetrabutylphosphine tetrafluoroborate), and the specific steps are as follows:

[0054] In a 10-liter high-pressure reactor equipped with stirring, cooling coils, temperature and pressure display instruments, 640 g (20 mol) of methanol, 2000 g (22.2 mol) of dimethyl carbonate and 2389 g of tetrabutylphosphine tetrafluoroborate were added, and the reaction system was replaced with high-purity nitrogen three times to make the oxygen content in the reaction system lower than 20 ppm. The reactor was temperature-controlled to 10° C., tetrafluoroethylene was added to the reactor to 0.05 MPa, and when the pressure dropped to 0.01 MPa, tetrafluoroethylene was added to maintain the pressure, and the reaction pressure was kept at 0.04-0.05 MPa, and the reaction temperature was kept between 10 and 20° C. After the reaction for 4 hours, 2070 g (20.7 mol) of tetrafluoroethylene was consumed cumulatively, and the reaction mass was cooled, and 3276 g (17.24 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester was obtained after distillation and rectification, with a yield of 83.3% and a purity of 97.8%. The distillate residue after distillation was washed and vacuum dried to recover the quaternary phosphonium salt alkaline ionic liquid, and a total of 2013 g was recovered with a recovery rate of 84.3%.

[0055] Comparative Example 5

[0056] The difference between this comparative example and Example 1 is that the imidazolium salt alkaline ionic liquid [BMIM][OH] is replaced by a pyridinium salt alkaline ionic liquid (N-butylpyridinium tetrafluoroborate), and the specific steps are as follows:

[0057] In a 10-liter high-pressure reactor equipped with stirring, cooling coils, temperature and pressure display instruments, 640 g (20 mol) of methanol, 2000 g (22.2 mol) of dimethyl carbonate and 2973 g of N-butylpyridinium tetrafluoroborate were added, and the reaction system was replaced with high-purity nitrogen three times to make the oxygen content in the reaction system lower than 20 ppm. The temperature of the reactor was controlled to 10° C., tetrafluoroethylene was added to the reactor to 0.05 MPa, and when the pressure dropped to 0.01 MPa, tetrafluoroethylene was added to maintain the pressure, and the reaction pressure was kept at 0.04-0.05 MPa, and the reaction temperature was kept between 10 and 20° C. After the reaction for 4 hours, 2000 g (20 mol) of tetrafluoroethylene was consumed cumulatively, and the reaction materials were cooled, and 3239 (17.05 mol) of colorless transparent liquid methoxytetrafluoropropionic acid methyl ester was obtained after distillation and rectification, with a yield of 85.2% and a purity of 97.3%. The residual liquid after distillation was washed and vacuum dried to recover the pyridinium salt alkaline ionic liquid, and a total of 2425 g was recovered, with a recovery rate of 81.6%.

[0058] Comparative Example 6

[0059] The difference between this comparative example and Example 1 is that the imidazolium salt alkaline ionic liquid is [BMIM][OH] recycled after 20 cycles, and the rest is the same as Example 1. Methyl methoxytetrafluoropropionate with a yield of 90.5% and a purity of 99.2% is obtained, and the recovery rate of the ionic liquid is 79.8%.

[0060] As can be seen from Examples 1-9, the present invention uses methanol, dimethyl carbonate and tetrafluoroethylene as raw materials, uses imidazole salt alkaline ionic liquid as a catalyst and solvent, performs addition reaction to prepare methyl methoxytetrafluoropropionate, the reaction temperature is wide and easy to control, the selectivity is good, the product yield is further improved, the purity of the prepared methyl methoxytetrafluoropropionate reaches 99.0-99.7%, and the yield reaches 90.0-98.0%; and, when methyl methoxytetrafluoropropionate is prepared by the method of the present invention, the imidazole salt alkaline ionic liquid used as a catalyst and solvent can be recycled, the recovery rate is above 80%, the recycled imidazole salt alkaline ionic liquid can be reused 1-20 times, and the reactor will not be corroded, which is more green and environmentally friendly.

[0061] By comparing Example 1 and Comparative Example 1, and Example 7 and Comparative Example 2, it can be seen that the present invention uses imidazole salt alkaline ionic liquid as a catalyst, and the yield of methoxytetrafluoropropionic acid methyl ester obtained is higher than that using sodium methoxide as a catalyst, and the purity of the obtained product is also higher.

[0062] Comparative Example 1 and Comparative Examples 3-5 show that not all alkaline ionic liquids can achieve the effect of the present invention. In the present invention, imidazole salt alkaline ionic liquids are used as catalysts, and compared with other catalyst systems, they are applied to methoxytetrafluoropropionate, and the yield is significantly improved, up to 97%. This is because the imidazole salt alkaline ionic liquids in the present invention are imidazole salt ionic liquids with functional groups, and thus have excellent catalytic activity, selectivity and stability, which are beneficial to the generation of the target product methoxytetrafluoropropionate, thereby improving the reaction yield; and, imidazole salt alkaline ionic liquids also act as solvents, which can dissolve polar and non-polar compounds, can improve the solubility of reactants and intermediates, thereby increasing the reaction speed and selectivity; at the same time, imidazole salt alkaline ionic liquids are also non-volatile, which can prevent the release of harmful vapors, making the reaction safer and more environmentally friendly.

[0063] In summary, the present invention uses imidazole salt alkaline ionic liquid as a catalyst and solvent to synthesize methyl methoxytetrafluoropropionate, the product yield and purity are significantly improved, and the catalyst can be recycled and reused multiple times, the catalyst recycling is simple and the utilization rate is high, and it is suitable for industrial production.

[0064] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for preparing methyl methoxytetrafluoropropionate, characterized in that: The following steps are involved: Methanol, dimethyl carbonate and imidazole salt alkaline ionic liquid are added into a reaction kettle, tetrafluoroethylene is continuously introduced, the system pressure is maintained stable, and an addition reaction is performed; after the reaction is completed, the reaction materials are cooled, and the product methoxytetrafluoropropionic acid methyl ester is obtained through distillation and rectification.

2. The method for preparing methyl methoxytetrafluoropropionate according to claim 1, characterized in that The molar ratio of the methanol to tetrafluoroethylene is (1-3):(2-5), and the molar ratio of the dimethyl carbonate to tetrafluoroethylene is (2-5):(1-3).

3. The preparation method of methoxytetrafluoropropionate according to claim 1, characterized in that The molar ratio of tetrafluoroethylene to imidazole salt alkaline ionic liquid is (3-8): (2-5).

4. The method for preparing methyl methoxytetrafluoropropionate according to claim 1, characterized in that The imidazolium salt alkaline ionic liquid includes one or more of [BTMG][OH], [BMIM][OH], [NBMD][OH], [BMIM][NTf2], and [EMIM][IM].

5. The method for preparing methyl methoxytetrafluoropropionate according to claim 1, characterized in that The imidazolium salt alkaline ionic liquid includes a newly prepared imidazolium salt alkaline ionic liquid and a recycled and reused imidazolium salt alkaline ionic liquid.

6. The method for preparing methyl methoxytetrafluoropropionate according to claim 5, characterized in that: The operation of recovering the imidazole salt alkaline ionic liquid is as follows: washing the distillation residue after distillation and vacuum drying the residue.

7. The method for preparing methyl methoxytetrafluoropropionate according to claim 1, characterized in that: The temperature of the addition reaction is -20 to 60° C., the time is 1 to 10 hours, and the pressure is -0.098 to 0.05 MPa.

8. The method for preparing methyl methoxytetrafluoropropionate according to claim 1, characterized in that The oxygen content in the system is less than 20 ppm.

9. The method for preparing methyl methoxytetrafluoropropionate according to claim 8, characterized in that Before introducing tetrafluoroethylene, high-purity nitrogen was used for replacement three times to reduce the oxygen content in the system to less than 20 ppm.