A process for the preparation of fluoroethylene carbonate

Abstract

The application provides a preparation method of fluoroethylene carbonate, comprising the following steps: introducing anhydrous hydrogen fluoride into a mixed system of vinylene carbonate and a catalyst to obtain fluoroethylene carbonate; and the catalyst is selected from hydrofluoric acid salts of organic bases. The preparation method of the application uses vinylene carbonate and anhydrous hydrogen fluoride as raw materials, does not need to add a reaction solvent, and can prepare fluoroethylene carbonate under mild conditions with high yield under the catalysis of a small amount of hydrofluoric acid salts of organic bases.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and relates to a preparation method of fluoroethylene carbonate. BACKGROUND

[0002] Fluoroethylene carbonate is an important electrolyte additive, which can promote the formation of SEI film on the negative electrode surface and effectively prevent the side reaction between the oxidizing substances in the electrolyte and the negative electrode. At present, there are mainly two methods for synthesizing fluoroethylene carbonate. One is direct fluorination method, which is to directly react fluorine gas with ethylene carbonate. However, fluorine gas is not only highly toxic, but also has high reactivity, and the reaction process is difficult to control, the by-products are more, the equipment requirement is high, the process condition is harsh, and the reaction yield is low. The other is halogen exchange method, which is to react chlorinating agent with ethylene carbonate to generate chloroethylene carbonate, and then to react chloroethylene carbonate with fluorinating agent to synthesize fluoroethylene carbonate. This method needs to strictly control the water content, and under the condition of no catalyst, the reaction time is too long, and the product is easy to decompose.

[0003] In summary, it is a technical problem to be solved in the field to develop a preparation method of fluoroethylene carbonate with mild conditions and high yield. SUMMARY

[0004] The application provides a preparation method of fluoroethylene carbonate, which uses vinylene carbonate and anhydrous hydrogen fluoride as raw materials, does not need to add additional reaction solvents, and can obtain fluoroethylene carbonate with high yield under the catalysis of a small amount of hydrogen fluoride salt of organic base and under mild conditions.

[0005] The application provides a preparation method of fluoroethylene carbonate, which comprises the following steps:

[0006] Anhydrous hydrogen fluoride is introduced into a mixed system of vinylene carbonate and a catalyst to obtain the fluoroethylene carbonate.

[0007] The catalyst is selected from hydrogen fluoride salts of organic bases.

[0008] In an alternative embodiment, the hydrogen fluoride salt of the organic base is selected from one or more of triethylamine trihydrofluoride, melamine hydrogen fluoride, pyridine hydrogen fluoride, N,N-diisopropylethylamine trihydrofluoride, and tetraethylammonium fluoride trihydrofluoride.

[0009] In an alternative embodiment, the molar ratio of the vinylene carbonate to the catalyst is 1:(0.05-0.5).

[0010] In an alternative embodiment, the molar ratio of the vinylene carbonate to the anhydrous hydrogen fluoride is 1:(1-10).

[0011] In an alternative embodiment, the molar ratio of the vinylene carbonate and the anhydrous hydrogen fluoride is 1:(3-7).

[0012] In an alternative embodiment, the pressure of the reaction is 0.3-3Mpa.

[0013] In an alternative embodiment, the temperature of the reaction is 5-90℃.

[0014] In an alternative embodiment, the time of the reaction is 1-20h.

[0015] In an alternative embodiment, after the reaction is completed, the process further comprises a purification treatment of the reaction solution.

[0016] The purification treatment comprises: a negative pressure removal treatment of the reaction solution to remove the residual hydrogen fluoride, and then obtaining the fluoroethylene carbonate through a reduced pressure distillation.

[0017] In an alternative embodiment, the pressure of the negative pressure removal treatment is 0.5-10kPa, the temperature is 20-50℃, and the time is 10-60min.

[0018] The implementation of the present application has at least the following advantages:

[0019] 1) The preparation method of the present application uses the hydrogen fluoride salt of an organic base as a catalyst to promote the dissociation of hydrogen fluoride and enhance the electrophilic addition activity of hydrogen fluoride to vinylene carbonate, so that the fluoroethylene carbonate is obtained with high yield and high activity.

[0020] 2) The preparation method of the present application does not need to add an organic solvent, uses hydrogen fluoride as a raw material, and has the function of a solvent at the same time. The hydrogen fluoride can be removed through a simple negative pressure removal in the subsequent purification process, which reduces the cost of the reaction and the difficulty of the purification. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The infrared spectrum of the fluoroethylene carbonate prepared in Example 1 of the present application is shown in FIG. 2. 1 H NMR chart.

[0022] Figure 2 The infrared spectrum of the fluoroethylene carbonate prepared in Example 1 of the present application is shown in FIG. 2. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] This invention provides a method for preparing fluoroethylene carbonate, comprising the following steps:

[0025] Anhydrous hydrogen fluoride is introduced into a mixture of vinylene carbonate and catalyst to react and yield fluoroethylene carbonate.

[0026] The catalyst is selected from the hydrofluoric acid salt of organic bases.

[0027] The above reaction process can be represented by the following reaction equation:

[0028]

[0029] Fluorine is highly electronegative, and the hydrofluoric covalent bonds in hydrogen fluoride are very stable and difficult to break, making it unsuitable for electrophilic addition reactions with the double bonds in vinylene carbonate. This invention utilizes the addition of an organic base hydrofluoric acid salt as a catalyst to the reaction system, promoting the dissociation of hydrogen fluoride and enhancing the electrophilic addition activity between hydrogen fluoride and vinylene carbonate, thereby achieving a high yield of fluoroethylene carbonate.

[0030] The preparation method of the present invention uses vinylene carbonate and anhydrous hydrogen fluoride as raw materials to prepare fluoroethylene carbonate in high yield under the catalysis of hydrofluoric acid salt of organic base. This method does not require the addition of an additional organic solvent. Hydrogen fluoride can also be used as a reaction solvent while participating in the reaction, which reduces the reaction cost and purification difficulty. Moreover, the hydrofluoric acid consumed in the catalyst can be continuously replenished by the raw material hydrogen fluoride, which promotes the reaction.

[0031] In a preferred embodiment, the hydrofluoric acid salt of the organic base is selected from one or more of triethylamine hydrofluoric acid salt, melamine hydrofluoric acid salt, pyridine hydrofluoric acid salt, N,N-diisopropylethylamine hydrofluoric acid salt, and tetraethylammonium fluoride hydrofluoric acid salt.

[0032] All of the above compounds can be used as catalysts to promote the preparation of fluoroethylene carbonate from vinylene carbonate and hydrogen fluoride with high activity and high yield.

[0033] In a preferred embodiment, the molar ratio of vinylene carbonate to catalyst is 1:(0.05 to 0.5). For example, the molar ratio of vinylene carbonate to catalyst can be 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, or any two of the above molar ratios.

[0034] When the amount of catalyst is less than 5% of the amount of vinylene carbonate, the improvement in reaction activity is limited, resulting in a low yield of fluorovinyl carbonate. When the amount of catalyst is greater than 50% of the amount of vinylene carbonate, the reaction yield will not increase further. Therefore, in order to balance the cost and yield of the reaction, it is preferable to control the molar ratio of vinylene carbonate and catalyst within the above range.

[0035] In a preferred embodiment, the molar ratio of vinylene carbonate to anhydrous hydrogen fluoride is 1:(1 to 10). For example, the molar ratio of vinylene carbonate to anhydrous hydrogen fluoride can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any two of the above molar ratios.

[0036] When the molar ratio of vinylene carbonate to anhydrous hydrogen fluoride is greater than 1:1, the amount of hydrogen fluoride used is too small to completely convert vinylene carbonate. Since vinylene carbonate and fluorovinyl carbonate have similar structures, they are difficult to separate during purification, which will increase the difficulty of purification. When the molar ratio of vinylene carbonate to anhydrous hydrogen fluoride is less than 1:10, the amount of hydrogen fluoride used is large, which will increase the reaction cost.

[0037] Hydrogen fluoride has a low boiling point of only 19.5°C. Even at low temperatures and under normal pressure, the slight exothermic reaction during the reaction can easily cause hydrogen fluoride to volatilize. To ensure that it can be fully mixed with vinylene carbonate under homogeneous liquid conditions, the above reaction can be carried out under pressure.

[0038] In a preferred embodiment, the reaction pressure is 0.3 to 3 MPa. For example, the reaction pressure can be 0.3 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, or any two of the above values.

[0039] The inventors have discovered that this reaction can be carried out at temperatures ranging from 5 to 90°C. For example, the reaction temperature can be 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or any two of the above values.

[0040] However, lower reaction temperatures result in slower reaction rates and require longer reaction times to complete the conversion of the raw materials. To balance higher reaction rates and yields, the above reactions are preferably carried out at temperatures between 50°C and 80°C.

[0041] Furthermore, within the aforementioned reaction temperature range, the reaction can be completed within 1 to 20 hours. Specifically, the reaction time can be controlled based on factors such as the reaction temperature, the molar ratio of the reactants, the amount of catalyst used, and the reaction pressure. For example, the reaction time can be 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours, 15 hours, 17 hours, 20 hours, or any combination of two of these values.

[0042] The reaction process can be monitored using conventional detection methods in the field, including but not limited to TLC, HPLC, NMR, etc., and is usually considered to be the endpoint when the starting material vinylene carbonate disappears or stops converting to the reaction.

[0043] After the reaction is completed, the process also includes purifying the reaction solution; the purification process includes: removing residual hydrogen fluoride from the reaction solution under negative pressure, and then obtaining fluoroethylene carbonate by vacuum distillation.

[0044] After the reaction is complete, in addition to the product, there may be residual hydrogen fluoride in the reaction solution. As mentioned earlier, hydrogen fluoride has a very low boiling point and can be easily separated from the reaction system in gaseous form under negative pressure. Then, the possible residual vinylene carbonate raw material or other liquid byproducts in the reaction solution can be removed by vacuum distillation to purify and obtain fluoroethylene carbonate.

[0045] In a preferred embodiment, the negative pressure removal process is performed at a pressure of 0.5–10 kPa, a temperature of 20–50 °C, and a time of 10–60 min.

[0046] Under the above conditions, not only can residual hydrogen fluoride in the reaction be completely removed, but the pressure and temperature are also relatively mild, and the removal time is also short, exhibiting the characteristics of being mild and efficient.

[0047] For example, the pressure for negative pressure removal treatment can be any two values ​​of 0.5 kPa, 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa or above.

[0048] The temperature for negative pressure removal can be 20℃, 30℃, 40℃, 50℃, or any two of the above values.

[0049] The negative pressure removal time can be 10 min, 13 min, 15 min, 18 min, 20 min, 30 min, 40 min, 50 min, 60 min, or any two of the above values.

[0050] The preparation method of fluoroethylene carbonate provided by the present invention will be described in detail below with reference to specific embodiments.

[0051] In the following embodiments, unless otherwise specified, all raw materials can be prepared by commercial purchase or conventional methods in the art. Experimental methods without specific conditions shall be performed in accordance with conventional methods and conditions in the art, or by following the product instructions.

[0052] It should be noted that the purity of the products in the following examples was determined by GC (Gas Chromatography).

[0053] Example 1

[0054] This embodiment provides a method for preparing fluoroethylene carbonate, including the following steps:

[0055] 1) Add 430g (5mol, 1equiv) of vinylene carbonate and 80.5g (0.5mol, 0.1equiv) of triethylamine trihydrofluoride to a 1L high-pressure reactor, start stirring, adjust the reaction temperature to 50℃, the reaction pressure to 0.8MPa, and introduce 300g of anhydrous hydrogen fluoride (15mol, 3equiv). Stir the reaction at this temperature for 3h. The reaction ends when GC detection shows that the vinylene carbonate raw material has disappeared.

[0056] 2) The residual hydrogen fluoride in the reaction solution was removed under negative pressure at 2 kPa and 35 °C. After 30 min, the removal of hydrogen fluoride was detected to be complete. Fluoroethylene carbonate was then obtained by vacuum distillation with a yield of 92.7% and a purity of 99.5%.

[0057] The fluoroethylene carbonate prepared in Example 1 was subjected to 1H NMR and IR spectra.

[0058] Figure 1 The fluoroethylene carbonate prepared in Example 1 of this invention 1 H NMR spectrum, from Figure 1 It can be analyzed that, 1 ¹H NMR (400 MHz, CDCl₃) δ (ppm): 6.225–6.398 (ddd, 1H), 4.539–4.672 (q, 2H), where the two hydrogens at 4.539–4.672 are the two hydrogens attached to the carbon at position A, and the hydrogen at 6.225–6.398 is the one hydrogen attached to the carbon at position B.

[0059] Figure 2 The infrared spectrum of the fluoroethylene carbonate prepared in Example 1 of this invention is shown below, where 1824 cm⁻¹ is the maximum infrared spectrum. -1 It is the characteristic absorption peak of the stretching vibration of the carbonyl group, at 1465 cm⁻¹. -1 It is the absorption peak of the methylene-CH2- in-plane rocking, 1152 cm⁻¹. -1 and 1077cm -1 It is the absorption peak of the symmetric and asymmetric stretching vibrations of COC, at 992 cm⁻¹. -1 The absorption peak is the CF stretching vibration, which indicates that the product contains carbonyl, carbonate, and CF bonds, consistent with the structure of FEC.

[0060] Examples 2-29

[0061] Examples 2 to 29 provide a method for preparing fluoroethylene carbonate, the steps of which are basically the same as those in Example 1. The differences are: the type of catalyst, the molar ratio of fluoroethylene carbonate (VC) to catalyst and hydrogen fluoride (HF), the reaction temperature, the reaction time, and the reaction pressure in step 1), and the temperature, time, and pressure of negative pressure removal in step 2) are different from those in Example 1. The specific differences are listed in Table 1.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing fluoroethylene carbonate, with reaction conditions basically the same as in Example 1. The difference is that the catalyst triethylamine trihydrofluoride was not added. After 3 hours of reaction, GC detection showed that the raw material vinylene carbonate had not been converted and no FEC was detected. After 3 more days of reaction, GC detection still showed no FEC formation.

[0064] The FEC preparation yields and product purities of Examples 1–29 are also listed in Table 1.

[0065] Table 1

[0066]

[0067]

[0068]

[0069] The following conclusions can be drawn from Table 1:

[0070] 1) As can be seen from the comparison between Examples 1-29 and Comparative Example 1, when no catalyst is added, vinylene carbonate and anhydrous hydrogen fluoride do not react, and no FEC is generated. However, the present invention uses hydrofluoric acid salts of organic bases as catalysts, which can catalyze the highly selective reaction of VC and HF to generate FEC.

[0071] 2) As can be seen from the data of Examples 1, 7, 9 and 10, triethylamine trihydrofluoride, melamine hydrofluoride, pyridine hydrofluoride, N,N-diisopropylethylamine trihydrofluoride and tetraethylammonium fluoride trihydrofluoride all exhibit excellent catalytic activity as catalysts, and can complete the reaction efficiently within 5 hours, with the FEC yield all above 90%.

[0072] 3) As can be seen from the comparison of Examples 1 and 11-15, when the molar ratio of catalyst to VC is in the range of (0.05-0.5):1, the yield of FEC can reach more than 90%, and the more catalyst is used, the more efficient the reaction and the shorter the reaction time. When the molar ratio of catalyst to VC is 0.025:1, the reaction rate decreases significantly, and it takes 25 hours for the raw materials to be completely converted. When the molar ratio of catalyst to VC is 0.8:1, although the reaction can be completed in 0.5 hours, the yield of FEC decreases.

[0073] 4) As can be seen from the comparison of Examples 1, 16-20, the greater the amount of HF used, the higher the required reaction pressure. The amount of HF, equal to or slightly excess of VC, can result in a high yield of the reaction. When the amount of HF is less than one equivalent of VC, the yield of FEC drops significantly to only 78.6%.

[0074] 5) As can be seen from the comparison of Examples 1 and 21-25, the reaction temperature affects both the yield and the reaction time of FEC. The reaction can achieve a high yield in the temperature range of 5-90°C. When the reaction temperature is higher than 50°C, the reaction time no longer decreases with the increase of temperature. Furthermore, higher temperatures require higher pressure to be applied to the system to avoid the volatilization of HF. The yield of FEC will also decrease significantly when the temperature is too high (100°C) or too low (0°C).

[0075] 6) As can be seen from the comparison of Examples 1, 26 to 29, the change in reaction pressure has no significant effect on the reaction time and the yield of FEC, as long as a certain pressure can be provided to the reaction system to prevent the volatilization of HF.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing fluoroethylene carbonate, characterized in that, Includes the following steps: Anhydrous hydrogen fluoride is introduced into a mixture of vinylene carbonate and a catalyst to react and obtain the fluoroethylene carbonate; the reaction pressure is 0.3~3 MPa. The catalyst is triethylamine trihydrofluoride; The molar ratio of the vinylene carbonate to the catalyst is 1:(0.05~0.5). The reaction temperature is 25~90℃.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the vinylene carbonate to the anhydrous hydrogen fluoride is 1:(1~10).

3. The preparation method according to claim 2, characterized in that, The molar ratio of the vinylene carbonate to the anhydrous hydrogen fluoride is 1:(3~7).

4. The preparation method according to claim 1, characterized in that, The reaction time is 1 to 20 hours.

5. The preparation method according to any one of claims 1-4, characterized in that, After the reaction is completed, the process also includes purifying the reaction solution; The purification process includes: subjecting the reaction solution to negative pressure defluorination to remove residual hydrogen fluoride, and then obtaining the fluoroethylene carbonate by vacuum distillation.

6. The preparation method according to claim 5, characterized in that, The negative pressure removal process is performed at a pressure of 0.5~10 kPa, a temperature of 20~50℃, and a time of 10~60 min.

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