Method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole type ionic liquid

Abstract

The application discloses a method for synthesizing hexafluoropropylene oxide dimer by catalysis of an imidazole type ionic liquid, and relates to the fine chemical technology field. The preparation method is as follows: S1. An imidazole type ionic liquid catalyst is added into a solvent, stirred uniformly, and subjected to activation treatment; S2. Hexafluoropropylene oxide is introduced into the activated mixture to perform reaction, and hexafluoropropylene oxide dimer crude products are obtained after the reaction is completed; S3. The crude products obtained in S2 are subjected to normal pressure rectification, and hexafluoropropylene oxide dimer pure products are obtained after the rectification; S4. The catalyst and the solvent are repeatedly used, and the steps of S2 and S3 are repeatedly performed for multiple times, and hexafluoropropylene oxide dimer is obtained; the imidazole type ionic liquid catalyst is metal functionalized methyl bisimidazole chloride M-(MimCleimCl-COO)2, wherein M is one of zinc, copper, cobalt and iron. The application adopts the imidazole type ionic liquid as the catalyst to prepare the hexafluoropropylene oxide dimer, the reaction has higher selectivity and yield, and the operation is convenient and the synthesis process is simple.

Description

Technical Field

[0001] This application relates to the field of fine chemical technology, and in particular to a method for the synthesis of hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids. Background Technology

[0002] Hexafluoropropylene oxide dimer is a perfluorinated reactive intermediate. Its terminal acyl fluoride group can react with various compounds to generate a series of fluorinated compounds, such as perfluoropropyl vinyl ether (PPVE), which is an important comonomer for the synthesis and modification of fluororesins. It can also introduce organofluorine functional groups through interaction with organic molecules, and has applications in the pharmaceutical and agricultural fields, thus having high application value.

[0003] In existing technologies, German patent DE2026669 discloses the use of silver nitrate as a catalyst, achieving a dimer yield of 86%. However, silver nitrate is photosensitive and produces nitrous acid gas, resulting in poor stability and operational safety. Japanese patent JP62195345 discloses the use of cesium fluoride as a catalyst, but the reaction temperature must be maintained at -20°C, and cesium fluoride is highly hygroscopic, causing some fluorinated fluoride to seep into the oligomers during the experiment, leading to operational difficulties, high cost, and overall high operating costs. German patent DE2924385 discloses a catalyst system composed of CuCl / CuCl2 / acrylonitrile, achieving a dimer yield of 84.6%, but it uses acrylonitrile, which is suspected of being carcinogenic. Chinese patent CN1026582C discloses a catalyst system composed of transition metal salts and tertiary diamines, generally including CuCl, CuCl2, CoCl2, ZnCl2, etc., resulting in relatively high dimer content and yield.

[0004] Current patents mostly utilize composite catalyst systems. Patent CN109485560B discloses a catalytic system using a mixture of phosphonamides and metal fluoride salts, yielding a dimer content exceeding 80%. Patent CN108264458B discloses a composite catalytic system composed of tertiary amines and tertiary diamines, with the addition of a fluorinated quaternary ammonium salt phase transfer agent, achieving a dimer yield of approximately 70%-80%. Patent CN109336758B discloses a catalytic system using a highly active emulsion layer containing tertiary diamine, triethylamine, and acyl fluoride, overcoming issues of moisture absorption, side reactions, and difficulty in recovery during preparation. However, this process generates hydrogen fluoride, and the dimer content is below 50%.

[0005] However, in existing catalyst systems, metal fluoride salts are solids, forming a heterogeneous phase in solvents. Furthermore, metal fluoride salts are highly hygroscopic, agglomerating, and deteriorating. Amine catalysts themselves exhibit high volatility and odor, requiring stringent operating conditions. These catalysts demand demanding reaction conditions, resulting in unstable reactions and difficulty in obtaining high-selectivity and high-yield hexafluoropropylene oxide dimers. Therefore, a new catalyst is urgently needed to effectively improve the selectivity and yield of hexafluoropropylene oxide dimers. Summary of the Invention

[0006] To improve the selectivity and yield of hexafluoropropylene oxide dimer, this application provides a method for synthesizing hexafluoropropylene oxide dimer using imidazole-type ionic liquid catalysis.

[0007] This application provides a method for synthesizing hexafluoropropylene oxide dimer using imidazole-type ionic liquid catalysis, which employs the following technical solution: A method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids includes the following steps: S1. Add the imidazole-type ionic liquid catalyst to the solvent, stir evenly, and perform activation treatment; S2. Hexafluoropropylene oxide is introduced into the activated mixture to carry out the reaction. After the reaction is completed, crude hexafluoropropylene oxide dimer product is obtained. S3. The crude product obtained in S2 is subjected to atmospheric distillation to obtain pure hexafluoropropylene oxide dimer. S4. The catalyst and solvent are reused, and steps S2 and S3 are repeated multiple times to obtain hexafluoropropylene oxide dimer.

[0008] By adopting the above technical solution and using a metal-functionalized imidazole ionic liquid as a catalyst, which exists in the solvent in an ionic state, it can be fully dispersed in the bulk phase and exert its effect. It has multiple catalytic active sites for ionic ring-opening and oligomerization, making it a multifunctional catalyst with high catalytic activity. When used in the synthesis reaction of hexafluoropropylene oxide dimer, it can improve the selectivity of the hexafluoropropylene oxide dimer, effectively suppressing the formation of hexafluoropropylene oxide polymers and obtaining hexafluoropropylene oxide dimers with higher yields and purity. Simultaneously, the metal-functionalized imidazole ionic liquid can be stably stored in the system and reused repeatedly, making it convenient to use, simplifying the synthesis operation, and providing mild reaction conditions. This can reduce overall production costs from multiple aspects and facilitate industrial production.

[0009] Preferably, the imidazole-type ionic liquid catalyst is a metal-functionalized methylbisimidazole chloride M-(MimCleimCl-COO)2, with the following structural formula: In equation (Ⅰ), M is a transition metal.

[0010] Preferably, in the structural formula (1) of the imidazole-type ionic liquid catalyst, M is one of zinc, copper, cobalt, and iron.

[0011] By employing the above technical solution and using a metal-functionalized imidazole ionic liquid as a catalyst, the oligomerization of hexafluoropropylene oxide can be catalyzed to form hexafluoropropylene oxide dimers. This method achieves a higher yield of hexafluoropropylene oxide dimers with a smaller catalyst dosage, effectively improving the selectivity and yield of the hexafluoropropylene oxide dimers. Furthermore, the synthesis process is simple, requires less stringent reaction conditions, is stable in use, and reduces production costs. The synthetic route of the metal-functionalized methylbisimidazole chloride catalyst is as follows: Taking M as zinc, (1) Preparation of 1-bromoethyl-3-methylimidazolium bromide: 1. Preparation of cyanoethylimidazolium: 2. Preparation of carboxylic acid-functionalized methylbisimidazole chloride: 3. Preparation of metal-functionalized ionic liquids:

[0012] Preferably, the activation treatment temperature in S1 is 30-50℃, and the activation treatment time is 1-2h.

[0013] Preferably, the solvent in S1 is one of tetraethylene glycol dimethyl ether or diethylene glycol dimethyl ether.

[0014] Preferably, the reaction temperature in S2 is 10-60℃, and the reaction time is 0.5-2h.

[0015] Preferably, the reaction temperature in S2 is 30-40℃, and the reaction time is 0.5-1h.

[0016] Preferably, the molar ratio of hexafluoropropylene oxide to imidazole ionic liquid catalyst is 1:(0.005-0.05).

[0017] Preferably, the molar ratio of hexafluoropropylene oxide to imidazole ionic liquid catalyst is 1:(0.01-0.03).

[0018] Preferably, the mass ratio of hexafluoropropylene oxide to solvent is 1:(0.5-5).

[0019] In summary, this application includes at least one of the following beneficial technical effects: 1. By adopting the above technical solution, a metal-functionalized imidazole ionic liquid is used as a catalyst. Existing in an ionic state in the solvent, it can be fully dispersed in the bulk phase and exert its effect. It has multiple catalytically active sites for ionic ring-opening and oligomerization, making it a multifunctional catalyst with high catalytic activity. When used in the synthesis of hexafluoropropylene oxide dimers, it can enhance the selectivity of the hexafluoropropylene oxide dimers, effectively suppressing the formation of hexafluoropropylene oxide polymers and obtaining hexafluoropropylene oxide dimers with higher yields and purity. Simultaneously, the metal-functionalized imidazole ionic liquid can be stably stored in the system and reused repeatedly, making it convenient to use. The synthesis operation is simple, and the reaction conditions are mild, which can reduce the overall production cost from multiple aspects and facilitate industrial production. Detailed Implementation

[0020] The present application will be further described in detail below with reference to the embodiments. Example

[0021] Example 1 S1. The air in the 5L reactor equipped with a stirrer is purged and replaced several times with nitrogen. Then, under nitrogen protection, 2300g of solvent tetraethylene glycol dimethyl ether and 103.7g of imidazole ionic liquid catalyst (MimCleimCl-COO)2Zn are added. The reactor is stirred at 40℃ and atmospheric pressure for 1h for activation treatment. S2. Then the temperature was lowered to 30℃. After the temperature stabilized, 2400g of hexafluoropropylene oxide was introduced to carry out the reaction. The reaction temperature was controlled at 30℃. After the hexafluoropropylene oxide was introduced, the mixture was stirred until the pressure inside the reactor remained constant and maintained for 0.5h. The final reaction mixture was divided into two layers. The upper layer was a mixture of solvent and catalyst, and the lower layer was the product. After standing, the product was released from the valve at the bottom of the reactor to obtain the crude product of hexafluoropropylene oxide dimer. S3. The crude hexafluoropropylene oxide dimer obtained in S2 is subjected to atmospheric distillation to obtain the pure hexafluoropropylene oxide dimer. S4. Retain the solvent tetraethylene glycol dimethyl ether and imidazole ionic liquid catalyst in the reactor, and repeat steps S2 and S3 twice to obtain hexafluoropropylene oxide dimer.

[0022] Example 2 S1. Purge and replace the air in the 5L reactor equipped with a stirrer with nitrogen several times. Then, under nitrogen protection, add 2300g of solvent tetraethylene glycol dimethyl ether and 96g of imidazole ionic liquid catalyst (MimCleimCl-COO)2Cu. Stir at 40℃ and atmospheric pressure for 1h for activation treatment. S2. Then the temperature was lowered to 30℃. After the temperature stabilized, 2400g of hexafluoropropylene oxide was introduced to carry out the reaction. The reaction temperature was controlled at 30℃. After the hexafluoropropylene oxide was introduced, the mixture was stirred until the pressure inside the reactor remained constant and maintained for 0.5h. The final reaction mixture was divided into two layers. The upper layer was a mixture of solvent and catalyst, and the lower layer was the product. After standing, the product was released from the valve at the bottom of the reactor to obtain the crude product of hexafluoropropylene oxide dimer. S3. The crude hexafluoropropylene oxide dimer obtained in S2 is subjected to atmospheric distillation to obtain the pure hexafluoropropylene oxide dimer. S4. Retain the solvent tetraethylene glycol dimethyl ether and imidazole ionic liquid catalyst in the reactor, and repeat steps S2 and S3 twice to obtain hexafluoropropylene oxide dimer.

[0023] Example 3 S1. The air in the 5L reactor equipped with a stirrer is purged and replaced several times with nitrogen. Then, under nitrogen protection, 2300g of solvent tetraethylene glycol dimethyl ether and 113g of imidazole ionic liquid catalyst (MimCleimCl-COO)2Co are added. The reactor is stirred at 40℃ and atmospheric pressure for 1h for activation treatment. S2. 2400g of hexafluoropropylene oxide is introduced for reaction, and the reaction temperature is controlled at 40℃. After the hexafluoropropylene oxide is introduced, the mixture is stirred until the pressure inside the reactor remains constant and is maintained for 1 hour. The final reaction mixture is divided into two layers. The upper layer is a mixture of solvent and catalyst, and the lower layer is the product. After standing, the product is released from the valve at the bottom of the reactor to obtain the crude product of hexafluoropropylene oxide dimer. S3. The crude hexafluoropropylene oxide dimer obtained in S2 is subjected to atmospheric distillation to obtain the pure hexafluoropropylene oxide dimer. S4. Retain the solvent tetraethylene glycol dimethyl ether and imidazole ionic liquid catalyst in the reactor, and repeat steps S2 and S3 twice to obtain hexafluoropropylene oxide dimer.

[0024] Example 4 S1. The air in the 5L reactor equipped with a stirrer is purged and replaced several times with nitrogen. Then, under nitrogen protection, 2300g of solvent tetraethylene glycol dimethyl ether and 132g of imidazole ionic liquid catalyst (MimCleimCl-COO)2Fe are added. The reactor is stirred at 40℃ and atmospheric pressure for 1h for activation treatment. S2. 2400g of hexafluoropropylene oxide is introduced for reaction, and the reaction temperature is controlled at 40℃. After the hexafluoropropylene oxide is introduced, the mixture is stirred until the pressure inside the reactor remains constant and is maintained for 1 hour. The final reaction mixture is divided into two layers. The upper layer is a mixture of solvent and catalyst, and the lower layer is the product. After standing, the product is released from the valve at the bottom of the reactor to obtain the crude product of hexafluoropropylene oxide dimer. S3. The crude hexafluoropropylene oxide dimer obtained in S2 is subjected to atmospheric distillation to obtain the pure hexafluoropropylene oxide dimer. S4. Retain the solvent tetraethylene glycol dimethyl ether and imidazole ionic liquid catalyst in the reactor, and repeat steps S2 and S3 twice to obtain hexafluoropropylene oxide dimer.

[0025] Example 5 Example 5 was carried out using the same apparatus and method as Example 1, except that the activation treatment in S1 of Example 5 was carried out at a temperature of 30°C for a time of 2 hours.

[0026] Example 6 Example 6 was carried out using the same apparatus and method as Example 1, except that the activation treatment in S1 of Example 6 was carried out at a temperature of 50°C for a time of 1.5 hours.

[0027] Example 7 Example 7 was carried out using the same apparatus and method as Example 1, except that the solvent used in S1 of Example 7 was diethylene glycol dimethyl ether.

[0028] Example 8 Example 8 was carried out using the same apparatus and method as Example 1, except that the reaction temperature in S2 of Example 8 was 10°C and the reaction time was 2 hours.

[0029] Example 9 Example 9 was carried out using the same apparatus and method as Example 1, except that the reaction temperature in S2 of Example 9 was 40°C and the reaction time was 1 hour.

[0030] Example 10 Example 10 was carried out using the same apparatus and method as Example 1, except that the reaction temperature in S2 of Example 10 was 60°C and the reaction time was 0.5h.

[0031] Example 11 Example 11 was carried out using the same apparatus and method as Example 1, except that the reaction temperature in S2 of Example 11 was 70°C and the reaction time was 0.25h.

[0032] Example 12 Example 12 was carried out using the same apparatus and method as Example 1, except that the reaction temperature in S2 of Example 12 was 5°C and the reaction time was 3h.

[0033] Example 13 Example 13 was carried out in accordance with Example 1 using the same apparatus and method, except that the mass of the imidazole ionic liquid catalyst (MimCleimCl-COO)2Zn used in Example 13 was 51.85 g.

[0034] Example 14 Example 14 was carried out in accordance with Example 1 using the same apparatus and method, except that the mass of the imidazole ionic liquid catalyst (MimCleimCl-COO)2Zn used in Example 14 was 311.11 g.

[0035] Example 15 Example 15 was carried out in accordance with Example 1 using the same apparatus and method, except that the mass of the imidazole-type ionic liquid catalyst (MimCleimCl-COO)2Zn used in Example 15 was 518.5 g.

[0036] Example 16 Example 16 was carried out in accordance with Example 1 using the same apparatus and method, except that the mass of the imidazole ionic liquid catalyst (MimCleimCl-COO)2Zn used in Example 16 was 41.48 g.

[0037] Example 17 Example 17 was carried out in accordance with Example 1 using the same apparatus and method, except that the mass of the imidazole-type ionic liquid catalyst (MimCleimCl-COO)2Zn used in Example 17 was 622.2 g.

[0038] Example 18 Example 18 was carried out using the same apparatus and method as Example 1, except that the mass of the solvent tetraethylene glycol dimethyl ether used in Example 18 was 1200g.

[0039] Example 19 Example 19 was carried out using the same apparatus and method as Example 1, except that the mass of the solvent tetraethylene glycol dimethyl ether used in Example 19 was 12000g, and the volume of the reaction vessel used in this example was 20L.

[0040] Example 20 Example 20 was carried out using the same apparatus and method as Example 1, except that the mass of the solvent tetraethylene glycol dimethyl ether used in Example 20 was 600g.

[0041] Example 21 Example 21 was carried out in accordance with Example 1 using the same apparatus and method, except that the mass of the solvent tetraethylene glycol dimethyl ether used in Example 21 was 13000g, and the volume of the reaction vessel used in this example was 20L.

[0042] Performance testing 1. The products obtained in Examples 1-21 were analyzed by gas chromatography: the mass of the crude product was recorded and its selectivity was calculated; the test results of the purity of the product after distillation were recorded, and the results are shown in Table 1.

[0043] The specific test results are as follows: Table 1 Performance Test Results As can be seen from the test data in Table 1, the method for preparing hexafluoropropylene oxide dimer catalyzed by imidazole ionic liquid provided in this application has a large yield and high selectivity of crude product. This indicates that the imidazole ionic liquid catalyst provided in this application can effectively improve the yield and selectivity of the reaction in the synthesis of hexafluoropropylene oxide dimer. Furthermore, the purity of the product can reach over 99.5% after distillation.

[0044] As can be seen from the test results of Examples 1-4, the imidazole-type ionic liquid catalyst provided in this application is beneficial to the selectivity and yield of hexafluoropropylene oxide dimer when the metal-functionalized methylbisimidazole chloride M-(MimCleimCl-COO)2 is any one of zinc, copper, cobalt, or iron, and the results of these catalysts participating in the reaction are not significantly different.

[0045] The test results of Examples 1, 5, and 6 show that the activation temperature and time provided in this application are beneficial to improving the selectivity and yield of the synthesis of hexafluoropropylene oxide dimer catalyzed by imidazole ionic liquid.

[0046] As can be seen from the detection results of Examples 1 and 7, the method for preparing hexafluoropropylene oxide dimer by catalysis of imidazole ionic liquid provided in this application is beneficial to the selectivity and yield of hexafluoropropylene oxide dimer when the solvent is selected as either tetraethylene glycol dimethyl ether or diethylene glycol dimethyl ether, and the results of the two reactions are not significantly different.

[0047] The test results of Examples 1, 8, 9, 10, 11, and 12 show that the method for preparing hexafluoropropylene oxide dimer by catalytic synthesis of imidazole-type ionic liquid provided in this application has high yield and selectivity when the reaction temperature and reaction time are 10-60℃ and 0.5-2h, respectively. The preferred reaction temperature and reaction time are 30-40℃ and 0.5-1h. When the temperature and time of the reactants are lower than 10-60℃ and 0.5-2h, it can be seen that the reaction yield and selectivity decrease significantly, and the purity of the product after distillation also decreases significantly.

[0048] The test results of Examples 1, 13, 14, 15, 16, and 17 show that the method for preparing hexafluoropropylene oxide dimers by catalysis of imidazole-type ionic liquids provided in this application exhibits high yield and selectivity when the molar ratio of hexafluoropropylene oxide to imidazole-type ionic liquid catalyst is in the range of 1:(0.005-0.05). Preferably, the molar ratio of hexafluoropropylene oxide to imidazole-type ionic liquid catalyst is 1:(0.01-0.03). When the molar ratio of hexafluoropropylene oxide to imidazole-type ionic liquid catalyst is lower than or higher than the value of 1:(0.005-0.05), it can be seen that the yield and selectivity of the reaction decrease significantly, and the purity of the product after distillation also decreases significantly.

[0049] As can be seen from the test results of Examples 1, 18, 19, 20, and 21, the method for preparing hexafluoropropylene oxide dimers by catalysis of imidazole-type ionic liquids provided in this application has high reaction yield and selectivity when the mass ratio of hexafluoropropylene oxide to solvent is in the range of 1:(0.5-5). However, when the mass ratio of hexafluoropropylene oxide to solvent is lower or higher than this ratio, the reaction yield and selectivity decrease significantly.

[0050] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids, characterized in that: Includes the following steps: S1. Add the imidazole-type ionic liquid catalyst to the solvent, stir evenly, and perform activation treatment; the activation treatment temperature is 30-50℃, and the activation treatment time is 1-2h; S2. Hexafluoropropylene oxide is introduced into the activated mixture to carry out the reaction. After the reaction is completed, crude hexafluoropropylene oxide dimer product is obtained. S3. The crude product obtained in S2 is subjected to atmospheric distillation to obtain pure hexafluoropropylene oxide dimer. S4. The catalyst and solvent are reused, and steps S2 and S3 are repeated multiple times to obtain hexafluoropropylene oxide dimer; The imidazole-type ionic liquid catalyst is a metal-functionalized methylbisimidazolium chloride M-(MimCleimCl-COO)2, with the following structural formula: (Formula I); In formula (Ⅰ), M is one of the transition metals zinc, copper, cobalt, and iron.

2. The method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids according to claim 1, characterized in that: The solvent mentioned in S1 is one of tetraethylene glycol dimethyl ether or diethylene glycol dimethyl ether.

3. The method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids according to claim 1, characterized in that: The reaction temperature in S2 is 10-60℃, and the reaction time is 0.5-2h.

4. The method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids according to claim 3, characterized in that: The reaction temperature in S2 is 30-40℃, and the reaction time is 0.5-1h.

5. The method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquids according to claim 1, characterized in that: The molar ratio of hexafluoropropylene oxide to imidazole ionic liquid catalyst is 1:(0.005-0.05).

6. The method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquid according to claim 5, characterized in that: The molar ratio of hexafluoropropylene oxide to imidazole ionic liquid catalyst is 1:(0.01-0.03).

7. The method for synthesizing hexafluoropropylene oxide dimer catalyzed by imidazole-type ionic liquid according to claim 1, characterized in that: The mass ratio of hexafluoropropylene oxide to solvent is 1:(0.5-5).

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