Preparation method of fluoroethylene carbonate

Abstract

The invention provides a preparation method of fluoroethylene carbonate, which comprises the following steps: introducing anhydrous hydrogen fluoride into a mixed system of vinylene carbonate and a catalyst for reaction to obtain fluoroethylene carbonate, the catalyst is selected from hydrofluoride of organic alkali. According to the preparation method disclosed by the invention, vinylene carbonate and anhydrous hydrogen fluoride are taken as raw materials, a reaction solvent does not need to be additionally added, and fluoroethylene carbonate can be prepared at high yield under a mild condition under the catalytic action of hydrofluoride of a small amount of organic alkali.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for preparing fluoroethylene carbonate. Background Art

[0002] Fluorinated ethylene 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 two main methods for synthesizing fluoroethylene carbonate. One is the direct fluorination method, which uses fluorine gas to directly react with ethylene carbonate. However, fluorine gas is not only highly toxic, but also has high reactivity, the reaction process is difficult to control, there are many by-products, and the equipment requirements are high. The process conditions are harsh and the reaction yield is low; the other is the halogen exchange method, which uses a chlorination agent to react with ethylene carbonate to generate chloroethylene carbonate, and then, the chloroethylene carbonate is reacted with a fluorination agent to perform halogen exchange to synthesize fluoroethylene carbonate. This method requires strict control of the moisture content. In the absence of a catalyst, the reaction time is too long and the product is easy to decompose.

[0003] In summary, developing a method for preparing fluoroethylene carbonate under mild conditions and with high yield is a technical problem that needs to be solved urgently in the art. Summary of the invention

[0004] The invention provides a method for preparing fluoroethylene hydrochloride. The method uses vinylene carbonate and anhydrous hydrogen fluoride as raw materials, does not require the addition of an additional reaction solvent, and can prepare fluoroethylene carbonate with high yield under mild conditions under the catalytic action of a small amount of hydrofluoric acid salt of an organic base.

[0005] The present invention provides a method for preparing fluoroethylene carbonate, comprising the following steps:

[0006] Introducing anhydrous hydrogen fluoride into a mixed system of vinylene carbonate and a catalyst to react and obtain the fluoroethylene carbonate;

[0007] The catalyst is selected from hydrofluoric acid salts of organic bases.

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

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

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

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

[0012] In an optional embodiment, the reaction pressure is 0.3-3 MPa.

[0013] In an optional embodiment, the reaction temperature is 5-90°C.

[0014] In an optional embodiment, the reaction time is 1 to 20 hours.

[0015] In an optional embodiment, after the reaction is completed, the process further includes purifying the reaction solution;

[0016] The purification process comprises: performing negative pressure removal treatment on the reaction solution to remove residual hydrogen fluoride therein, and then obtaining the fluoroethylene carbonate by reduced pressure distillation.

[0017] In an optional embodiment, the negative pressure removal treatment has a pressure of 0.5 to 10 kPa, a temperature of 20 to 50° C., and a time of 10 to 60 min.

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

[0019] 1) The preparation method of the present invention uses the hydrofluoride of an organic base as a catalyst, which promotes the dissociation of hydrogen fluoride and enhances the electrophilic addition activity of hydrogen fluoride to vinylene carbonate, so that fluoroethylene carbonate is obtained by reaction with high yield and high activity.

[0020] 2) The preparation method of the present invention does not require the addition of an additional organic solvent. Hydrogen fluoride is used as a raw material and also serves as a solvent. It can be removed by simple negative pressure removal during the subsequent purification process, thereby reducing the cost of the reaction and the difficulty of purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The fluoroethylene carbonate prepared in Example 1 of the present invention 1 H NMR spectra;

[0022] Figure 2 This is the infrared spectrum of fluoroethylene carbonate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

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

[0025] Into a mixed system of vinylene carbonate and a catalyst, anhydrous hydrogen fluoride is introduced to react to obtain fluoroethylene carbonate;

[0026] Wherein, the catalyst is selected from hydrofluoric acid salts of organic bases.

[0027] The above reaction process can be expressed by the following reaction formula:

[0028]

[0029] Fluorine has a strong electronegativity, and the hydrogen-fluorine covalent bond in hydrogen fluoride is very stable and difficult to break, and it is not easy to undergo an electrophilic addition reaction with the double bond in vinylene carbonate. The present invention promotes the dissociation of hydrogen fluoride by adding a hydrofluoric acid salt of an organic base as a catalyst in the reaction system, thereby improving the electrophilic addition activity of hydrogen fluoride and vinylene carbonate, and further preparing fluoroethylene carbonate with a high yield.

[0030] The preparation method of the invention uses vinylene carbonate and anhydrous hydrogen fluoride as raw materials, and prepares fluoroethylene carbonate with high yield under the catalysis of hydrofluoric acid salt of an organic base. The method does not need to add an additional organic solvent, and hydrogen fluoride can be used as a reaction solvent while participating in the reaction, thereby reducing the cost of the reaction and the difficulty of purification. Moreover, the hydrofluoric acid consumed in the catalyst can be continuously supplemented by the raw material hydrogen fluoride, thereby promoting the reaction.

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

[0032] The above compounds as catalysts can promote the reaction of vinylene carbonate and hydrogen fluoride to prepare fluoroethylene carbonate with high activity and high yield.

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

[0034] When the amount of the catalyst is less than 5% of the amount of vinylene carbonate, the reaction activity is limitedly improved, resulting in a lower yield of fluoroethylene carbonate; when the amount of the catalyst is greater than 50% of the amount of vinylene carbonate, the yield of the reaction will not increase further. Therefore, in order to balance the cost and yield of the reaction, it is preferred to control the molar ratio of vinylene carbonate to the catalyst within the above range.

[0035] In a preferred embodiment, the molar ratio of vinylene carbonate to anhydrous hydrogen fluoride is 1:(1-10). Exemplarily, 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 a range consisting of 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 small and insufficient to completely convert vinylene carbonate. Vinylene carbonate and fluoroethylene carbonate have similar structures and are difficult to separate during the purification process, 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] The boiling point of hydrogen fluoride is relatively low, only 19.5°C. Even if the reaction is carried out at a relatively low temperature under normal pressure, the slight heat release during the reaction will easily lead to the volatilization of hydrogen fluoride. In order to fully mix it with vinylene carbonate under liquid homogeneous conditions for reaction, the above reaction can be carried out under pressurized conditions.

[0038] In a preferred embodiment, the reaction pressure is 0.3-3 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 a range consisting of any two of the above values.

[0039] The inventors have found that the reaction can be carried out at a temperature of 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 a range consisting of any two of the above values.

[0040] However, a lower reaction temperature will result in a slower reaction rate, and a longer reaction time is required to complete the conversion of the raw materials. In order to take into account both a higher reaction rate and a higher reaction yield, the above reaction is preferably carried out at a temperature of 50°C to 80°C.

[0041] Further, within the above reaction temperature range, the reaction can be completed within 1 to 20 hours. The reaction time can be regulated according to factors such as the reaction temperature, the molar ratio of the raw materials, the amount of catalyst, the reaction pressure, etc. Exemplarily, 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 a range consisting of any two of the above values.

[0042] The progress of the reaction can be monitored by conventional detection means in the art, including but not limited to TLC, HPLC, NMR, etc. The reaction endpoint is usually when the starting material vinylene carbonate disappears or is no longer converted.

[0043] After the reaction is completed, the process also includes a purification process for the reaction liquid; wherein the purification process includes: performing negative pressure removal treatment on the reaction liquid to remove residual hydrogen fluoride therein, and then obtaining fluoroethylene carbonate by reduced pressure distillation.

[0044] After the reaction is completed, in addition to the product, there may be residual hydrogen fluoride in the reaction liquid. As mentioned above, the boiling point of hydrogen fluoride is very low, and it is easy to separate from the reaction system in the form of gas under negative pressure conditions. Then, the vinylene carbonate raw material or other liquid by-products that may remain in the reaction liquid are removed by reduced pressure distillation to purify and obtain fluoroethylene carbonate.

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

[0046] Under the above conditions, not only can the 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, with the characteristics of mildness and high efficiency.

[0047] Exemplarily, the pressure of the negative pressure removal treatment can be 0.5 kPa, 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa or a range consisting of any two of the above values;

[0048] The temperature of negative pressure removal can be 20℃, 30℃, 40℃, 50℃ or a range consisting of any two of the above values;

[0049] The time for negative pressure removal can be 10 min, 13 min, 15 min, 18 min, 20 min, 30 min, 40 min, 50 min, 60 min or a range consisting of 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 examples.

[0051] In the following examples, unless otherwise specified, all raw materials can be purchased from commercial sources or prepared by conventional methods in the art. Experimental methods without specific conditions are selected according to conventional methods and conditions in the art or according to 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, comprising the following steps:

[0055] 1) Add 430 g (5 mol, 1 equiv) of vinylene carbonate and 80.5 g (0.5 mol, 0.1 equiv) of triethylamine trihydrofluoride into a 1 L autoclave, start stirring, adjust the reaction temperature to 50° C., the reaction pressure to 0.8 MPa, introduce 300 g of anhydrous hydrogen fluoride (15 mol, 3 equiv), stir and react at the reaction temperature for 3 h, and the reaction is terminated when the vinylene carbonate raw material disappears by GC detection;

[0056] 2) Residual hydrogen fluoride in the reaction solution was removed under negative pressure at 2 kPa and 35° C. After 30 minutes, it was detected that the hydrogen fluoride was completely removed, and then fluoroethylene carbonate was obtained by reduced pressure distillation with a yield of 92.7% and a purity of 99.5%.

[0057] The fluoroethylene carbonate prepared in Example 1 was tested by hydrogen nuclear magnetic resonance spectrum and infrared spectrum:

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

[0059] Figure 2 This is the infrared spectrum of fluoroethylene carbonate prepared in Example 1 of the present invention, wherein 1824 cm -1 It is the characteristic absorption peak of carbonyl stretching vibration, 1465cm -1 It is the absorption peak of the in-plane swing of methylene -CH2-, 1152cm -1 and 1077cm -1 It is the absorption peak of COC symmetric and asymmetric stretching vibration, 992cm -1 It is the absorption peak of CF stretching vibration, from which it can be judged that the product contains carbonyl group, carbonate group and CF bond, which is consistent with the structure of FEC.

[0060] Embodiments 2 to 29

[0061] Examples 2 to 29 respectively provide a method for preparing fluoroethylene carbonate, wherein the steps are substantially the same as those of Example 1, except that: the type of catalyst in step 1), the molar ratio of fluoroethylene carbonate (VC) to the catalyst and hydrogen fluoride (HF), the reaction temperature, the reaction time, the reaction pressure, and the temperature, time, and pressure of the negative pressure removal in step 2) are different from those of 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, which is basically the same as the reaction conditions in Example 1, except that the catalyst triethylamine trihydrofluoride is not added, and GC is used to detect after 3 hours of reaction, and the raw material vinylene carbonate is not converted and FEC is not detected. After continuing the reaction for 3 days, GC is used to detect, and the generation of FEC is still not detected.

[0064] The FEC preparation yields and product purities of Examples 1 to 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) From the comparison between Examples 1-29 and Comparative Example 1, it can be seen that when no catalyst is added, vinylene carbonate and anhydrous hydrogen fluoride do not react, and no FEC is generated. However, the present invention uses a hydrofluoric acid salt of an organic base as a catalyst to catalyze the reaction of VC and HF to generate FEC with high selectivity.

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

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

[0073] 4) From the comparison of Examples 1, 16 to 20, it can be seen that the greater the amount of HF used, the higher the required reaction pressure. The amount of HF used in an equivalent amount to VC or in an appropriate excess can give the reaction a higher yield. When the amount of HF used is less than one equivalent of VC, the yield of FEC decreases significantly to only 78.6%.

[0074] 5) From the comparison of Examples 1 and 21 to 25, it can be seen that the reaction temperature has an effect on the yield and reaction time of FEC. A higher yield can be obtained in the temperature range of 5 to 90°C. When the reaction temperature is higher than 50°C, the reaction time no longer shortens with increasing temperature, and a higher temperature requires a higher pressure to be applied to the system to avoid the volatilization of HF. When the temperature is too high (100°C) or too low (0°C), the yield of FEC will also decrease significantly.

[0075] 6) From the comparison of Examples 1 and 26 to 29, it can be seen that 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 avoid 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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: The following steps are involved: Introducing anhydrous hydrogen fluoride into a mixed system of vinylene carbonate and a catalyst to react and obtain the fluoroethylene carbonate; The catalyst is selected from hydrofluoric acid salts of organic bases.

2. The preparation method according to claim 1, characterized in that: The hydrofluoride of the organic base is selected from one or more of triethylamine trihydrofluoride, melamine hydrofluoride, pyridine hydrofluoride, N,N-diisopropylethylamine trihydrofluoride, and tetraethylammonium fluoride trihydrofluoride.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the vinylene carbonate to the catalyst is 1:(0.05-0.5).

4. 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).

5. The preparation method according to claim 4, characterized in that: The molar ratio of the vinylene carbonate to the anhydrous hydrogen fluoride is 1:(3-7).

6. The preparation method according to any one of claims 1 to 5, characterized in that: The reaction pressure is 0.3-3 MPa.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The reaction temperature is 5-90°C.

8. The preparation method according to claim 7, characterized in that: The reaction time is 1 to 20 hours.

9. The preparation method according to any one of claims 1 to 8, characterized in that: After the reaction is completed, the process of purifying the reaction solution is also included; The purification process comprises: performing negative pressure removal treatment on the reaction solution to remove residual hydrogen fluoride therein, and then obtaining the fluoroethylene carbonate by reduced pressure distillation.

10. The preparation method according to claim 9, characterized in that: The negative pressure removal treatment is performed at a pressure of 0.5 to 10 kPa, a temperature of 20 to 50° C., and a time of 10 to 60 minutes.

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