A process for the preparation of a hydrofluoroether

Abstract

The present application provides a preparation method of hydrofluoroether, comprising the following steps: using amino alcohol and fluorine-containing olefin as raw materials, and performing addition reaction under the condition that neutral ionic liquid is used as catalyst and solvent; the neutral ionic liquid comprises at least one of fluorine-containing neutral ionic liquid. The inventor finds that using fluorine-containing neutral ionic liquid as catalyst can effectively improve the yield and purity of hydrofluoroether, and avoid the generation of unsaturated impurities under alkaline conditions. In addition, the fluorine-containing neutral ionic liquid used in the present application is easy to recover, can be recycled, and has the advantages of no corrosion of the reactor, no pollution to the environment, easy control of the reaction and no waste salt generation, etc., and is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and specifically relates to a method for preparing hydrofluoroethers. Background Technology

[0002] Hydrofluoroethers (HFEs) are a class of ether compounds containing fluorine, carbon, hydrogen, and oxygen. Belonging to partially fluorinated ethers, they are a new generation of alternatives to ozone-depleting substances (ODS). They have zero ODP, low GWP, and possess a series of excellent properties such as low viscosity, low freezing point, low surface tension, and good electrochemical stability. These solvents have been widely used as cleaning agents, coolants, foaming agents, and lubricants. Some HFEs with high fluorine-to-hydrogen ratios (F / H) can exhibit non-flammable properties and can be used as co-solvents in lithium-ion battery electrolytes, flame retardants, and as coolants in large-scale equipment applications.

[0003] There are several existing methods for preparing hydrofluoroethers, such as: (1) fluorination of ether compounds by fluorine gas or metal fluorides; (2) electrochemical fluorination of ether compounds; (3) reaction of fluorinated alcohols with haloalkanes in the presence of sodium or alkali metal hydroxides to obtain hydrofluoroethers; and (4) addition reaction of fluorinated alcohols with fluorinated alkenes. These methods all have certain shortcomings: method (1) generates HF during the production process, which is highly corrosive and requires stringent reaction equipment; method (2) has high energy consumption and low yield; method (3), although it can be used, most of them have long reaction times, high reaction temperatures, and low yields; in comparison, only the addition reaction of fluorinated alcohols with fluorinated alkenes in method (4) is relatively simple and yields a higher product, and is currently the main method for preparing fluorinated ethers.

[0004] Currently, the main method for synthesizing hydrofluoroethers (HFEs) is the addition reaction between fluorinated alcohols and fluorinated olefins. Under alkaline conditions, the reaction proceeds through nucleophilic addition of alcohols and perfluoroolefins to obtain the target product. Patent CN103739450A uses alkaline compounds such as NaOH, KOH, or alkali metal compounds like KF and CsF as catalysts to catalyze the reaction of fluorinated alkanols and fluorinated olefins to synthesize HFEs. This method is simple but generates a large amount of waste salt, especially during the removal of the solid alkaline catalyst, which requires a significant amount of water, resulting in substantial waste liquid and potential environmental problems. Patent CN104045524A uses fluorinated alcohols and fluorinated olefins as raw materials to prepare HFEs. While this avoids the solvent recovery step, the use of a solid catalyst, sodium fluoroalkoxide, still generates waste salt, increasing subsequent processing costs, and the product yield is relatively low, around 80%. Furthermore, these methods inevitably generate fluorinated olefin byproducts. The formation of these byproducts increases production costs and complicates the separation and purification of the final product.

[0005] To improve the selectivity of addition reactions, Yasuhisa et al. reported a method for preparing hydrofluoroethers by reacting alcohols with perfluoroolefins under neutral conditions using tetra(triphenylphosphine)palladium as a catalyst. This method effectively avoids the production of fluorinated olefin byproducts, thus simplifying the conditions for product separation and purification (Matsukawa, Yasuhisa et al., Angew. Chem., Int. Ed., 2005, 44(7), 1128-1130). However, because this method uses expensive palladium as a catalyst, and the catalyst cannot be recycled, it greatly increases the production cost of the product and is not suitable for large-scale industrial production. Patent CN114907192A describes the addition reaction of alcohols with perfluoroolefins in an aqueous system in the presence of potassium fluoride and additives to obtain the target product, hydrofluoroether. Although the formation of olefins is avoided, the yield of hydrofluoroether is too low. Patent CN114605233A describes a hydroalkoxylation reaction using fluorinated alcohols and fluorinated olefins as raw materials, with an ionic liquid as the main catalyst and an amine compound as the co-catalyst, to obtain hydrofluoroethers. Although it exhibits high selectivity for hydrofluoroethers, the amine compounds are basic substances with low boiling points, pungent odors, and can lead to the formation of unsaturated byproducts; furthermore, using two catalysts results in higher costs.

[0006] In summary, the method for preparing hydrofluoroethers using fluorinated alcohols and fluorinated olefins as raw materials is simple. However, the existing solid base as a catalyst will result in a large amount of solid and liquid waste. Although tetraphenylphosphine palladium has high efficiency, the catalyst is expensive and not suitable for industrial production. Furthermore, it is easy to generate olefin impurities under alkaline conditions in the reaction system.

[0007] Therefore, it is of great significance to further explore green catalytic pathways for the preparation of hydrofluoroethers. Summary of the Invention

[0008] Based on this, the purpose of this invention is to provide a method for preparing hydrofluoroethers, which effectively solves the problems of low yield and purity of hydrofluoroethers, easy generation of by-products, and difficulty in catalyst recovery in existing preparation methods.

[0009] To achieve the above objectives, the present invention adopts the following technical solution.

[0010] A method for preparing hydrofluoroether includes the following steps: using amino alcohols and fluorinated olefins as raw materials, carrying out an addition reaction under the condition of a neutral ionic liquid as a catalyst and solvent; wherein the neutral ionic liquid includes at least one of fluorinated neutral ionic liquids.

[0011] In some embodiments, the fluorinated neutral ionic liquid includes at least one of [EMIM][BF4], [BMIM][BF4], [MMIM][BF4], [HMIM][BF4], [HMIM][BF6], [EMIM][PF6], and [BMIM][PF6].

[0012] In some embodiments, the amino alcohol is selected from at least one of trans-p-aminocycloethanol, 2-amino-1-phenylethanol, 2-aminoethanol, and 1-amino-2-propanol.

[0013] In some embodiments, the fluorinated olefin is selected from at least one of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, and trifluorochloroethylene.

[0014] In some embodiments, the pressure of the addition reaction is 0.9 MPa to 1.0 MPa.

[0015] In some embodiments, the temperature of the addition reaction is 20°C to 90°C; preferably, the temperature of the addition reaction is 50°C to 85°C.

[0016] In some embodiments, the addition reaction takes 1 to 10 hours.

[0017] In some embodiments, the molar ratio of the amino alcohol to the fluorinated olefin is 2-5:1-3.

[0018] In some embodiments, the molar ratio of the neutral ionic liquid to the amino alcohol is 1:10 to 20.

[0019] In some embodiments, the oxygen content in the addition reaction system is less than 20 ppm.

[0020] In some embodiments, the method for preparing hydrofluoroether further includes the following steps: distilling the product of the addition reaction to obtain a crude product, and washing, distilling and drying the crude product to obtain the hydrofluoroether.

[0021] This invention provides a method for preparing hydrofluoroethers. The method uses a fluorinated neutral ionic liquid as a catalyst and solvent to catalyze the addition reaction of amino alcohols with fluorinated olefins, thereby obtaining hydrofluoroethers. The inventors have discovered that using the fluorinated neutral ionic liquid selected in this invention as a catalyst can effectively improve the yield and purity of hydrofluoroethers. This is because the fluorinated neutral ionic liquid promotes the addition reaction of amino alcohols with fluorinated olefins, avoiding the formation of unsaturated impurities during the reaction and effectively reducing the content of byproducts. Furthermore, the fluorinated neutral ionic liquid used in this invention is easy to recover and can be recycled. It also has advantages such as non-corrosion of the reactor, no environmental pollution, easy reaction control, and no waste salt generation, making it suitable for industrial production. Detailed Implementation

[0022] Unless otherwise specified, the experimental methods described in the following embodiments of the present invention are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.

[0023] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0024] The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or device that includes a series of steps is not limited to the steps or modules listed, but may optionally include steps not listed, or may optionally include other steps inherent to such process, method, product, or device.

[0025] In this invention, "at least one" refers to one or more.

[0026] The following description is based on specific embodiments.

[0027] Example 1

[0028] In a 5-liter high-pressure reactor equipped with a stirrer, cooling coil, and temperature and pressure display instruments, 200g of [EMIM][BF4] and 641g (10.5mol) of 2-aminoethanol were added. The mixture was purged three times with high-purity nitrogen to reduce the oxygen content in the reaction system to below 20ppm. The system was then evacuated to -0.06MPa, and tetrafluoroethylene was added to 0MPa. The material in the reactor was heated to 70°C, and tetrafluoroethylene was added to the reactor to 1.0MPa. When the pressure dropped to 0.9MPa, tetrafluoropropylene was added to maintain the pressure, keeping the reaction pressure between 0.9 and 1.0MPa and the reaction temperature between 68°C. After 2 hours of reaction, a total of 2150g (21.5mol) of tetrafluoroethylene was consumed. The reaction mixture was then cooled. After distillation, washing with water, rectification, and drying, 2510 g (9.61 mol) of hydrofluoroether (CF2HCF2NHCH2CH2OCF2CF2H) was obtained. GC-MS analysis showed a yield of 97.1%, a purity of 99.7%, and an unsaturated compound content of 0.03%. The distillate was washed and dried under vacuum at 70 °C for 12 h, recovering 169.37 g of [EMIM][BF4], with a recovery rate of 84.68%.

[0029] Example 2

[0030] In a 5-liter high-pressure reactor equipped with a stirrer, cooling coil, and temperature and pressure display instruments, 256 g of [EMIM][PF6] and 1152 g (10 mol) of trans-p-aminocyclohexanol were added. The mixture was purged three times with high-purity nitrogen to reduce the oxygen content in the reaction system to below 20 ppm. The system was then evacuated to -0.06 MPa, and tetrafluoroethylene was added to 0 MPa. The material in the reactor was heated to 80°C, and tetrafluoroethylene was added to the reactor to 1.0 MPa. When the pressure dropped to 0.9 MPa, tetrafluoroethylene was added to maintain the pressure, keeping the reaction pressure between 0.9 and 1.0 MPa and the reaction temperature between 76°C. After 3 hours of reaction, a total of 2030 g (20.3 mol) of tetrafluoroethylene was consumed. The reaction mixture was then cooled. Hydrofluoroether (HF) was obtained after distillation, washing with water, rectification, and drying. 3010g (9.55mol) of [EMIM][PF6] was analyzed by GC-MS, with a yield of 96.5%, purity of 99.8%, and unsaturated compound content of 0.02%. The distillate was washed and vacuum dried at 70℃ for 12h, and 211.94g of [EMIM][PF6] was recovered, with a recovery rate of 82.79%.

[0031] Example 3

[0032] In an 8-liter high-pressure reactor equipped with a stirrer, cooling coil, and temperature and pressure display instruments, 226 g of [BMIM][BF4] and 1372 g (10 mol) of 2-amino-1-phenylethanol were added. The mixture was purged three times with high-purity nitrogen to reduce the oxygen content in the reaction system to below 20 ppm. The system was then evacuated to -0.06 MPa, and hexafluoropropylene was added to 0 MPa. The material in the reactor was heated to 60°C, and hexafluoropropylene was added to the reactor to 1.0 MPa. When the pressure dropped to 0.9 MPa, hexafluoropropylene was added to maintain the pressure, keeping the reaction pressure between 0.9 and 1.0 MPa and the reaction temperature between 66°C. After 1 hour of reaction, a total of 3105 g (20.7 mol) of hexafluoropropylene was consumed. The reactants were then cooled. Hydrofluoroether was obtained after distillation, washing with water, rectification, and drying. 3230 g (9.58 mol) was analyzed by GC-MS, with a yield of 96.8%, purity of 99.5%, and unsaturated compound content of 0.03%. The distillate was washed and vacuum dried at 70 °C for 12 h, recovering 188.19 g of [BMIM][BF4], with a recovery rate of 83.27%.

[0033] Example 4

[0034] The ionic liquid recovered after one use was reused, otherwise the same as in Example 1. Hydrofluoroether (CF2HCF2NHCH2CH2OCF2CF2H) was obtained. GC-MS analysis showed a yield of 96.7%, a purity of 99.7%, and an unsaturated compound content of 0.03%. The recovery rate of the ionic liquid was 84.97%.

[0035] Example 5

[0036] The ionic liquid recovered after three cycles was reused, with other procedures the same as in Example 1. Hydrofluoroether (CF2HCF2NHCH2CH2OCF2CF2H) was obtained. GC-MS analysis showed a yield of 96.5%, purity of 99.4%, and unsaturated compound content of 0.03%. The recovery rate of the ionic liquid was 83.66%.

[0037] Example 6

[0038] The ionic liquid recovered after 10 cycles was reused, with other procedures the same as in Example 1. Hydrofluoroether (CF2HCF2NHCH2CH2OCF2CF2H) was obtained. GC-MS analysis showed a yield of 95.3%, purity of 99.5%, and unsaturated compound content of 0.04%. The recovery rate of the ionic liquid was 79.15%.

[0039] Comparative Example 1

[0040] Except for replacing the neutral ionic liquid with 29.5 g of 85 wt% potassium hydroxide solution (catalyst) and 641 g of DMF (solvent), everything else was the same as in Example 1. GC-MS analysis revealed a hydrofluoroether (CF2HCF2NHCH2CH2OCF2CF2H) with a yield of 91.4%, a purity of 91.2%, and an unsaturated compound content of 8.6%.

[0041] Comparative Example 2

[0042] The neutral ionic liquid was replaced with 28 g of 85 wt% potassium hydroxide solution (catalyst) and 1152 g of DMF (solvent), otherwise the same as in Example 2. GC-MS analysis revealed a hydrofluoroether with a yield of 90.8%, purity of 90.1%, and unsaturated compound content of 9.7%.

[0043] Comparative Example 3

[0044] The neutral ionic liquid was replaced with 28 g of 85 wt% potassium hydroxide solution (catalyst) and 1372 g of DMF (solvent), otherwise the same as in Example 3. GC-MS analysis revealed a hydrofluoroether with a yield of 90.2%, purity of 90.4%, and unsaturated compound content of 9.3%.

[0045] Comparative Example 4

[0046] The neutral ionic liquid was replaced with 156 g of basic ionic liquid ([BMIM]OH), otherwise the same as in Example 1. GC-MS analysis revealed a hydrofluoroether (CF₂HCF₂NHCH₂CH₂OCF₂CF₂H) with a yield of 95.4%, purity of 94.3%, and unsaturated compound content of 3.6%, with an ionic liquid recovery rate of 81.7%.

[0047] Comparative Example 5

[0048] The neutral ionic liquid was replaced with 280g of neutral ionic liquid [EMIM][AlCl4], otherwise the same as in Example 1. GC-MS analysis revealed a hydrofluoroether (CF2HCF2NHCH2CH2OCF2CF2H) with a yield of 95.7%, purity of 98.2%, unsaturated compound content of 1.63%, and ionic liquid recovery of 83.79%.

[0049] Comparative Example 6

[0050] The neutral ionic liquid was replaced with 260 g of 1-octyl-3-methylimidazolium acetate, otherwise the same as in Example 1. GC-MS analysis revealed a hydrofluoroether (CF₂HCF₂NHCH₂CH₂OCF₂CF₂H) with a yield of 96.1%, purity of 98.5%, unsaturated compound content of 1.47%, and a recovery rate of 84.43% for the ionic liquid.

[0051] The hydrofluoroether yield, hydrofluoroether purity, unsaturated compound impurity content, and ionic liquid recovery rate of the above examples and comparative examples are shown in Table 1:

[0052] Table 1

[0053] Yield / % purity / % Unsaturated compound content / % Ionic liquid recovery rate / % Example 1 97.1 99.7 0.03 84.68 Example 2 96.5 99.8 0.02 82.79 Example 3 96.8 99.5 0.03 83.27 Example 4 96.7 99.7 0.03 84.97 Example 5 96.5 99.4 0.03 83.66 Example 6 95.3 99.5 0.04 79.15 Comparative Example 1 91.4 91.2 8.6 - Comparative Example 2 90.8 90.1 9.7 - Comparative Example 3 90.2 90.4 9.3 - Comparative Example 4 95.4 94.3 3.6 81.7 Comparative Example 5 95.7 98.2 1.63 83.79 Comparative Example 6 96.1 98.5 1.47 84.43

[0054] The above results (Examples 1-6) demonstrate that the preparation method of the present invention can effectively improve the yield and purity of hydrofluoroethers and reduce the content of unsaturated compound impurities. Furthermore, the method for recovering the fluorine-containing neutral ionic liquid catalyst of the present invention is simple and has a high recovery rate. After being recycled once, three times, and ten times, the yield of the target product and the content of unsaturated compounds obtained by reusing the fluorine-containing neutral ionic liquid showed no significant change compared to the first use.

[0055] A comparison of the data from Examples 1-3 and Comparative Examples 1-3 shows that the present invention uses a fluorine-containing neutral ionic liquid as a catalyst and solvent, and the yield of the product obtained is higher than that of the target product obtained using potassium hydroxide solution, and the content of unsaturated compounds in the product is also lower.

[0056] A comparison of Example 1 and Comparative Example 4 shows that when an alkaline ionic liquid catalyst is used, the product contains more unsaturated compounds, and the purity and yield are also lower.

[0057] A comparison of Example 1 with Comparative Examples 5 and 6 shows that when a non-fluorine-containing neutral ionic liquid catalyst is used, the content of unsaturated compounds in the product increases and the purity decreases.

[0058] In summary, the preparation method of the present invention uses a suitable neutral ionic liquid as a catalyst and solvent to prepare hydrofluoroether, which can effectively improve the yield and purity of hydrofluoroether, reduce the content of unsaturated impurities, and the catalyst is easy to recycle.

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A process for the preparation of a hydrofluoroether, characterized in that, The method includes the following steps: using amino alcohols and fluorinated olefins as raw materials, an addition reaction is carried out under conditions where a neutral ionic liquid is used as a catalyst and solvent; the oxygen content in the addition reaction system is less than 20 ppm; the pressure of the addition reaction is 0.9 MPa to 1.0 MPa; the amino alcohol is selected from at least one of trans-p-aminocycloethanol, 2-amino-1-phenylethanol, 2-aminoethanol, and 1-amino-2-propanol; The neutral ionic liquid is selected from at least one of [EMIM][BF4], [BMIM][BF4], [MMIM][BF4], [HMIM][BF4], [HMIM][BF6], [EMIM][PF6], and [BMIM][PF6]. The fluorinated olefin is selected from at least one of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, and trifluorochloroethylene.

2. The method for preparing hydrofluoroether according to claim 1, characterized in that, The addition reaction is carried out at a temperature of 20°C to 90°C.

3. The method for preparing hydrofluoroether according to claim 1, characterized in that, The addition reaction takes 1 to 10 hours.

4. The method for preparing hydrofluoroether according to claim 1, characterized in that, The molar ratio of the amino alcohol to the fluorinated olefin is 2~5:1~3.

5. The method for preparing hydrofluoroether according to claim 1, characterized in that, The molar ratio of the neutral ionic liquid to the amino alcohol is 1:10~20.

6. The method for preparing hydrofluoroether according to any one of claims 1 to 5, characterized in that, It also includes the following steps: The product of the addition reaction is distilled to obtain a crude product, which is then washed with water, distilled, and dried to obtain the hydrofluoroether.