Catalyst for synthesizing trifluoroethyl carbonate and preparation method thereof

Abstract

The invention discloses a catalyst for synthesizing trifluoroethyl carbonate and a preparation method of the catalyst. The preparation method of the catalyst comprises the following steps: aminating chloromethylated polystyrene-based cross-linked microspheres to obtain a resin catalyst, and modifying the resin catalyst by using different anion functional groups to obtain the strong base type anion exchange resin catalyst. The prepared resin catalyst is suitable for catalyzing transesterification of trifluoroethanol and diphenyl carbonate to synthesize trifluoroethyl carbonate, the conversion per pass of the reaction is high, the yield is high, the process for preparing the catalyst is simple and environmentally friendly, and the catalyst can be recycled and is stable.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly relates to a catalyst for transesterification synthesis of trifluoroethyl carbonate and a preparation method thereof. Background Art

[0002] With the development of the times, environment-friendly energy technologies have increasingly attracted people's attention. Compared with traditional fossil fuels, lithium-ion batteries have become the preferred technology in the energy storage field due to their advantages such as high energy density, long cycle life, and environmental friendliness. The electrolyte is the core component of lithium-ion batteries, and its main component is carbonate-based electrolyte. However, research shows that traditional carbonate-based electrolytes are prone to solvent decomposition reactions under high-temperature or high-voltage conditions, which not only lead to insufficient thermal stability and rapid capacity decay of lithium-ion batteries, but also pose safety hazards such as thermal runaway.

[0003] Trifluoroethyl carbonate is a relatively new type of fluorinated carbonate. Compared with traditional carbonates, after fluorine atoms replace oxygen atoms on traditional organic solvents, the oxygen content of flammability will decrease, inhibiting the combustion possibility of the solvent. As an additive, it can improve the thermal stability and safety performance of the electrolyte. Due to the strong electron-withdrawing ability of fluorine element, trifluoroethyl carbonate can also increase the decomposition voltage of the electrolyte solvent, which is beneficial to form a stable and effective purification film on the surface of the negative carbon base, so as to improve the compatibility of other related materials with the electrolyte and then stabilize the electrochemical performance of the electrode.

[0004] Currently, the industrial preparation route of trifluoroethyl carbonate still uses the traditional phosgene method. This technical system has inherent defects such as difficult process control, prominent safety risks, and significant environmental burden due to its dependence on the highly toxic precursor triphosgene. Under the action of a basic catalyst, the transesterification reaction of trifluoroethanol and diphenyl carbonate can not only obtain trifluoroethyl carbonate products, but also by-products phenol. The transesterification method has the advantages of easy availability of raw materials and simple process, and is expected to become the mainstream route for trifluoroethyl carbonate.

[0005] Lu Gaoshan et al. used sodium hydride as the catalyst for the transesterification reaction of trifluoroethanol and diphenyl carbonate. After reacting at 120 °C for 8 h, the highest yield of trifluoroethyl carbonate was 51.1% (Synthesis of Trifluoroethyl Carbonate and Its Application in Lithium-Ion Batteries, Master's Thesis of Guangdong University of Technology, 2015). However, using sodium hydride as the catalyst has problems such as violent reaction and dangerous operation. In addition, as a homogeneous catalyst, the product yield is low, and the catalyst cannot be recycled, resulting in high production costs. Therefore, it is urgent to develop a heterogeneous catalyst suitable for the transesterification synthesis of trifluoroethyl carbonate from trifluoroethanol and diphenyl carbonate. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method of a heterogeneous catalyst aiming at the deficiencies of the existing catalysts for synthesizing trifluoroethyl carbonate by the transesterification of trifluoroethanol and diphenyl carbonate.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A catalyst for synthesizing trifluoroethyl carbonate and a preparation method thereof, specifically including the following steps: (1) Amination is carried out by adding an aminating agent to chloromethylated polystyrene-based crosslinked microspheres. After the reaction ends, type A resin catalyst is obtained by washing with deionized water. The mass ratio of chloromethylated polystyrene-based crosslinked microspheres to the aminating agent is 1:6; (2) A compound containing an anionic functional group is added to the type A resin catalyst obtained in step (1) and mixed. Then methanol is added and left to stand at room temperature for a certain time for exchange. After filtration, it is washed with deionized water and dried to obtain a strong-base anion exchange resin catalyst. The compound containing an anionic functional group is imidazole, hydroquinone, and 2-hydroxypyridine, and the corresponding anionic functional groups are imidazole anion, hydroquinone anion, and 2-hydroxypyridine anion.

[0008] Further, the crosslinking degree of the chloromethylated polystyrene-based crosslinked microspheres in step (1) is 7%.

[0009] Further, the aminating agent in step (1) is one or a mixture of triethylamine, trimethylamine, and ammonia water.

[0010] Further, the reaction temperature of the amination in step (1) is 30 - 60 °C.

[0011] Further, the pH value of the reaction system of the amination in step (1) is 7 - 11, and the pH is controlled by a 10% sodium hydroxide aqueous solution.

[0012] Further, the anionic functional groups in step (2) are imidazole anion, hydroquinone anion, and 2-hydroxypyridine anion.

[0013] Further, the mass ratio of the anionic functional group, methanol to the type A resin catalyst in step (2) is (2 - 5):(2 - 4):1.

[0014] Further, the room temperature standing exchange time in step (2) is 16 - 20 h.

[0015] Further, the drying temperature in step (2) is 45 - 65 °C, and the drying time is 20 - 24 h.

[0016] Compared with the prior art, the advantages of the present invention are: 1) The present invention uses a heterogeneous anion exchange resin catalytic system to replace the traditional homogeneous catalyst, effectively solving the problems of complex catalyst separation and recovery processes and poor reusability in the traditional process.

[0017] 2) By immobilizing the catalytic active sites, the alkaline resin avoids the emission of sodium salt-containing solid waste generated after the use of homogeneous catalysts, reducing the environmental pollution risk from the source.

[0018] 3) Since there is no need to introduce metal components such as sodium ions, the alkaline resin catalytic system eliminates the problem of metal impurity residues in the production process of the electrolyte, helping to improve the product purity.

[0019] 4) Through the functional modification of the resin surface, the alkaline resin has high catalytic activity (when the molar ratio of trifluoroethanol to diphenyl carbonate is 5:1, the reaction temperature is 80 °C, the single-pass conversion rate of diphenyl carbonate is higher than 90%, and the product yield is higher than 70%), and strong heat resistance (the catalyst can operate stably at 65 - 85 °C). Detailed implementation mode

[0020] In order to make the content of the present invention easier to understand, the following further describes the technical solution of the present invention in combination with specific implementation modes, but the present invention is not limited thereto.

[0021] Example 1 Weigh 5 g of chloromethylated polystyrene-based cross-linked microspheres with a cross-linking degree of 7%, add 30 g of trimethylamine solvent for amination, heat up to 50 °C by stirring, control the pH to 9 by adding 10% sodium hydroxide aqueous solution during the amination process, carry out the amination reaction for 10 h, and after the reaction, wash with deionized water until neutral and free of chloride ions to obtain the A-type resin catalyst. Add 3 times the mass of the A-type resin catalyst of hydroquinone for functional modification, then add 3 times the mass of the A-type resin catalyst of methanol, let it stand at room temperature for 16 h, carry out anion exchange with the A-type resin catalyst, and rinse with deionized water until the residual anions on the surface are completely removed. After placing the prepared anion exchange resin in a constant temperature drying oven at 50 °C, dry it for 24 h to obtain a strongly basic anion exchange resin-hydroquinone catalyst (A-2PhO).

[0022] Example 2 Weigh 5 g of chloromethylated polystyrene-based crosslinked microspheres with a crosslinking degree of 7%, add 30 g of trimethylamine for amination, heat up to 50 °C by stirring, control the pH to 9 by adding a 10% sodium hydroxide aqueous solution during the amination process, carry out the amination reaction for 10 h, and after the reaction is completed, wash with deionized water until neutral and free of chloride ions to obtain A-type resin catalyst. Add 2-hydroxypyridine with a mass three times that of the A-type resin catalyst for functional modification, then add methanol with a mass three times that of the A-type resin catalyst, let it stand at room temperature for 16 h, carry out anion exchange with the A-type resin catalyst, and rinse with deionized water until the residual anions on the surface are completely removed. Place the prepared anion exchange resin in a constant temperature drying oven at 50 °C and dry for 24 h to obtain a strongly basic anion exchange resin-2-hydroxypyridine catalyst (A-OP).

[0023] Example 3 Weigh 5 g of chloromethylated polystyrene-based crosslinked microspheres with a crosslinking degree of 7%, add 30 g of trimethylamine for amination, heat up to 50 °C by stirring, control the pH to 9 by adding a 10% sodium hydroxide aqueous solution during the amination process, carry out the amination reaction for 10 h, and after the reaction is completed, wash with deionized water until neutral and free of chloride ions to obtain A-type resin catalyst. Add imidazole with a mass three times that of the A-type resin catalyst for functional modification, then add methanol with a mass three times that of the A-type resin catalyst, let it stand at room temperature for 16 h, carry out anion exchange with the A-type resin catalyst, and rinse with deionized water until the residual anions on the surface are completely removed. Place the prepared anion exchange resin in a constant temperature drying oven at 50 °C and dry for 24 h to obtain a strongly basic anion exchange resin-imidazole catalyst (A-IM).

[0024] Comparative Example 1 Weigh 5 g of chloromethylated polystyrene-based crosslinked microspheres with a crosslinking degree of 7%, add 30 g of trimethylamine for amination, heat up to 50 °C by stirring, control the pH to 9 by adding a 10% sodium hydroxide aqueous solution during the amination process, carry out the amination reaction for 10 h, and after the reaction is completed, wash with deionized water until neutral and free of chloride ions to obtain A-type resin catalyst. Place the prepared resin material in a constant temperature drying oven at 50 °C and dry for 24 h to obtain a strongly basic anion exchange resin (A).

[0025] Comparative Example 2 Weigh 5 g of chloromethylated polystyrene-based crosslinked microspheres with a crosslinking degree of 7%, add 30 g of trimethylamine for amination, heat to 50 °C by stirring, control the pH to 9 by adding a 10% sodium hydroxide aqueous solution during the amination process, carry out the amination reaction for 10 h, and after the reaction is completed, wash with deionized water until neutral and free of chloride ions to obtain the A-type resin catalyst. Add phenol with a mass three times that of the A-type resin catalyst for functional modification, then add methanol with a mass three times that of the A-type resin catalyst, let it stand at room temperature for 16 h, carry out anion exchange with the A-type resin catalyst, and rinse with deionized water until the residual anions on the surface are completely removed. Place the prepared anion exchange resin in a constant temperature drying oven at 50 °C and dry for 24 h to obtain a strongly basic anion exchange resin-phenol catalyst (A-PhO).

[0026] Catalyst performance evaluation: Weigh 0.5 mol of trifluoroethanol and 0.1 mol of diphenyl carbonate, stir well and heat to 50 °C, and add 2.14 g of the catalysts prepared in the above examples and comparative examples respectively, and carry out the transesterification reaction at a reaction temperature of 80 °C for 8 h. After the reaction is completed, quantitative analysis is carried out by gas chromatography. The obtained results are shown in Table 1.

[0027] Table 1 Catalytic effects of different catalysts From the performance evaluation of different catalysts in the examples and comparative examples, it can be seen that the A-OP type catalyst prepared by 2-hydroxypyridine anion functional modification in Example 2 has the best catalytic performance. Under the preparation conditions of this catalyst, the conversion rate of diphenyl carbonate is 96.15%, and the yield of trifluoroethyl carbonate is 78.39%.

[0028] Therefore, the A-OP type catalyst is recycled. The specific steps are as follows: Filter the reaction solution to obtain the resin catalyst, soak it with methanol and rinse it at least three times, dry it in a vacuum drying oven at 50 °C for 24 h, and use the dried A-OP type resin for repeated experiments to test the stability of the catalyst.

[0029] Catalyst stability evaluation: Weigh 0.5 mol of trifluoroethanol and 0.1 mol of diphenyl carbonate, stir well and heat to 50 °C, add 2.14 g of the recycled catalyst, and carry out the transesterification reaction at a reaction temperature of 80 °C for 8 h. After the reaction is completed, quantitative analysis is carried out by gas chromatography. This operation is repeated five times, and the experimental results are shown in Table 2.

[0030] Table 2 Comparison of catalytic performance when the catalyst is reused From the results of the recycling experiment in Table 2, it can be seen that the A-OP type catalyst functionalized with 2-hydroxypyridine anion is easy to separate and recycle. The catalyst still has good catalytic performance after being reused 5 times. The conversion rate of diphenyl carbonate remains above 95%, and the yield of trifluoroethyl carbonate remains above 74%. Therefore, the A-OP type catalyst prepared by the present invention has good recyclability and cycle stability.

[0031] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a catalyst for synthesizing trifluoroethyl carbonate, characterized in that: It includes the following steps: (1) Add an aminating agent to chloromethylated polystyrene cross-linked microspheres for amination. After the reaction is completed, wash with deionized water to obtain a Type A resin catalyst. The mass ratio of chloromethylated polystyrene cross-linked microspheres to the aminating agent is 1:6; (2) Add a compound containing an anionic functional group to the Type A resin catalyst obtained in step (1), then add methanol and allow to stand at room temperature for a certain time for exchange. After filtration, wash with deionized water and dry to obtain a strong-base anion exchange resin catalyst; the compound containing an anionic functional group is imidazole, hydroquinone, and 2-hydroxypyridine, and the corresponding anionic functional groups are imidazole anion, hydroquinone anion, and 2-hydroxypyridine anion.

2. The preparation method according to claim 1, characterized in that: In step (1), the cross-linking degree of the chloromethylated polystyrene cross-linked microspheres is 7%.

3. The preparation method according to claim 1, characterized in that: In step (1), the aminating agent is one or a mixture of triethylamine, trimethylamine, and ammonia water.

4. The preparation method according to claim 1, wherein: In step (1), the reaction temperature for amination is 30-60°C.

5. The preparation method according to claim 1, characterized in that: In step (1), the pH value of the amination reaction system is 7-11, and the pH is controlled by a 10% sodium hydroxide aqueous solution.

6. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the anionic functional group, methanol to the Type A resin catalyst is (2-5):(2-4):

1.

7. The preparation method according to claim 1, characterized in that: In step (2), the time for standing at room temperature for exchange is 16-20 h.

8. The method according to claim 1, characterized in that: In step (2), the drying temperature is 45-65°C, and the drying time is 20-24 h.

9. A catalyst for synthesizing trifluoroethyl carbonate obtained by the preparation method according to any one of claims 1-8.

10. Use of the catalyst according to claim 9 in the synthesis of trifluoroethyl carbonate, characterized in that: The temperature of the synthesis reaction is 65-85°C.

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