Synthesis method of carbon dioxide-based cyclic carbonate

Abstract

The invention relates to the technical field of preparation of cyclic carbonate, and discloses a synthesis method of carbon dioxide-based cyclic carbonate. The method comprises the following steps: S1, adding cyclohexene oxide and a catalyst into a reaction kettle, replacing air in the reaction kettle with CO2, adjusting the pressure of the reaction kettle to 2-6 MPa and the temperature to 80-140 DEG C, and carrying out a reaction; the catalyst comprises Lewis acid and Lewis base, and the Lewis base is a quaternary phosphonium salt initiator; and S2, after the reaction is completed, cooling to room temperature, adding a quencher to terminate the reaction, and purifying and drying the product to obtain the cyclic carbonate. According to the invention, the product can be conveniently purified, and the reaction efficiency can be greatly improved.

Description

Technical Field

[0001] The present application relates to the technical field of cyclic carbonate preparation, and in particular to a method for synthesizing carbon dioxide-based cyclic carbonate. Background Art

[0002] CO2 is the main component of greenhouse gases, and it is also a safe, non-toxic, and abundant C1 resource. Converting CO2 into useful chemicals not only helps reduce CO2 emissions, but also partially replaces fossil resources, and is one of the important ways to achieve "carbon neutrality". At present, CO2 can be used to synthesize a variety of organic chemicals and intermediates. Among the many products converted from CO2, cyclic carbonates are important chemical products, which are widely used in battery electrolytes, cosmetics, coatings, etc. At the same time, as a building block for organic synthesis and material processing, cyclic carbonates have important applications in chemical transformations, such as decarboxylation, hydrogenation, and transesterification reactions. Although cyclic carbonates can be prepared by reacting epoxides, propargyl alcohol, and ethylene glycol with CO2, considering that the cyclic addition of CO2 and epoxides to cyclic carbonates has the advantages of 100% atom economy and non-toxicity, it is considered to be an economical CO2 resource utilization technology route.

[0003] Publication No. CN118344389A, CN118344388A and CN118852469A and other Chinese patent documents all disclose the synthesis method of carbon dioxide-based cyclic carbonate, mainly focusing on the construction and development of metal catalysts. The synthesis of carbon dioxide-based cyclic carbonate can be achieved in the relevant technical schemes, but the reaction is promoted by a metal catalyst, and there is a problem of difficulty in separating metal residues in subsequent product processing. Therefore, the synthesis of carbon dioxide-based cyclic carbonate still has a large room for improvement. Summary of the invention

[0004] The present invention synthesizes a quaternary phosphonium salt chain initiator and forms a new catalyst system with a Lewis acid, which is first applied to the synthesis of carbon dioxide-based cyclic carbonate, thereby increasing the reaction rate and shortening the reaction time, and has great application prospects. The synthesis method in the present application is simple, has mild reaction conditions, has low requirements on industrial equipment, is low in cost, and is suitable for industrial production.

[0005] This application adopts the following technical solutions: A method for synthesizing a carbon dioxide-based cyclic carbonate comprises the following steps: S1, adding cyclohexene oxide and a catalyst into a reactor, replacing the air in the reactor with CO2, adjusting the pressure of the reactor to 2-6 MPa and the temperature to 80-140°C, and reacting; the catalyst comprises a Lewis acid and a Lewis base, and the Lewis base is a quaternary phosphonium salt initiator; S2. After the reaction is completed, cool to room temperature, add a quencher to terminate the reaction, and purify and dry the product to obtain a cyclic carbonate.

[0006] By adopting the above technical scheme, the present invention synthesizes a quaternary phosphonium salt chain initiator through triphenylphosphine and bromoalkane, and combines it with a Lewis acid to form a catalyst system. The Lewis acid plays a role in the catalytic reaction mainly by forming a coordination bond with the Lewis base in the reactant. This coordination can activate the relevant functional groups in the reactant, thereby accelerating the reaction process; compared with traditional catalysts, the reaction efficiency is increased, the reaction time is shortened to 4-8h, and the production cost is reduced. The product obtained in the synthesis method of the present application can be dissolved, and then the rotary evaporation method, distillation method and other means can be used to obtain the final pure product, and the product is pure and the purification process is simple and convenient.

[0007] Optionally, the quaternary phosphonium salt initiator is prepared by the following steps: reacting triphenylphosphine, bromoalkane and solvent under an inert gas atmosphere at a reaction temperature of 60-100° C., removing excess components after the reaction is completed, and purifying and drying to obtain the quaternary phosphonium salt initiator.

[0008] By adopting the above technical scheme, the quaternary phosphonium salt initiator in the present application is prepared by reacting triphenylphosphine and bromoalkane. After the reaction is completed, it is purified and dried to finally obtain a pure quaternary phosphonium salt initiator. The reaction temperature is between 60-100°C, which is conducive to the forward reaction. The temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C.

[0009] Optionally, the brominated alkane is selected from one of benzyl bromide, p-methoxybenzyl bromide and p-trifluoromethylbenzyl bromide.

[0010] By adopting the above technical scheme, the quaternary phosphonium salt initiator is prepared by using the above components and triphenylphosphine. The prepared quaternary phosphonium salt initiator cooperates with Lewis acid to have the advantage of improving reaction efficiency.

[0011] Optionally, the Lewis acid is selected from one of triphenylboron, triethylboron, tributylboron or boron trichloride.

[0012] Optionally, the molar ratio of the Lewis acid to the Lewis base is 1:(1-4).

[0013] By adopting the above technical solution and controlling the molar ratio between the Lewis acid and the Lewis base, the synergistic effect between the two is better, thereby better promoting the reaction.

[0014] Optionally, the solvent is selected from one of acetonitrile, chloroform and dimethyl sulfoxide.

[0015] By adopting the above technical solution, solvents such as acetonitrile are inert solvents that can provide a good dissolving environment and stability for the reaction, thereby promoting the effective reaction of triphenylphosphine and bromohydrocarbon to generate corresponding products.

[0016] Optionally, the molar ratio of the cyclohexene oxide to the quaternary phosphonium salt initiator is (1500-4000):1.

[0017] Optionally, the quencher is selected from glacial acetic acid.

[0018] In summary, the present application includes at least one of the following beneficial effects: 1. The present invention synthesizes a quaternary phosphonium salt chain initiator through triphenylphosphine and bromoalkane, and combines it with Lewis acid to form a catalyst system. Compared with traditional catalysts, the reaction efficiency is increased, the reaction time is shortened to 4-8h, the production cost is reduced, and it is suitable for large-scale industrial production.

[0019] 2. The present invention uses a quaternary phosphonium salt initiator and a non-metallic organic boron compound to form a catalytic system for the synthesis of cyclic carbonates, thereby avoiding the difficulty in separating metal residues in subsequent product treatment caused by metal catalysts. The treatment method is simple, the reaction conditions are mild, and the requirements for industrial equipment are low. DETAILED DESCRIPTION

[0020] Preparation Example 1 Triphenylphosphine, benzyl bromide and acetonitrile were added into a reaction bottle under nitrogen atmosphere, wherein the molar ratio of triphenylphosphine, benzyl bromide and acetonitrile was 1:1.1:20, stirred and dissolved under heating conditions, and triphenylphosphine and benzyl bromide were chemically reacted at 70°C for 12 hours, then cooled to room temperature, acetonitrile and benzyl bromide were removed by vacuum distillation, the crude product was washed three times with ethyl acetate, then recrystallized in ether, and finally the product was placed in a vacuum drying oven at 40°C for 24 hours to obtain a solid powdery quaternary phosphonium salt initiator.

[0021] Preparation Example 2 Triphenylphosphine, p-methoxybenzyl bromide and acetonitrile were added into a reaction bottle under nitrogen atmosphere, wherein the molar ratio of triphenylphosphine, p-methoxybenzyl bromide and acetonitrile was 1:1.1:20, and the mixture was stirred and dissolved under heating conditions, and triphenylphosphine and p-methoxybenzyl bromide were chemically reacted at 70°C for 12 hours, and then the mixture was cooled to room temperature, and acetonitrile and p-methoxybenzyl bromide were removed by vacuum distillation. The crude product was washed three times with ethyl acetate and then recrystallized in ether. Finally, the product was dried in a vacuum drying oven at 40°C for 24 hours to obtain a solid powdery quaternary phosphonium salt initiator.

[0022] Preparation Example 3 Triphenylphosphine, p-trifluoromethylbenzyl bromide and acetonitrile are added to a reaction bottle under a nitrogen atmosphere, wherein the molar ratio of triphenylphosphine, p-trifluoromethylbenzyl bromide and acetonitrile is 1:1.1:20, and the mixture is stirred and dissolved under heating conditions, and triphenylphosphine and p-trifluoromethylbenzyl bromide are chemically reacted at 70°C for 12 hours, and then the temperature is lowered to room temperature, and acetonitrile and p-methoxybenzyl bromide are removed by vacuum distillation. The crude product is washed three times with ethyl acetate and then recrystallized in ether. Finally, the product is placed in a vacuum drying oven and dried at 40°C for 24 hours to obtain a solid powdery quaternary phosphonium salt initiator.

[0023] Example 1 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron, and 0.2 mmol of the quaternary phosphonium salt initiator prepared in Preparation Example 1 were added to a 50 mL high-pressure reactor, 4.0 MPa of CO2 was introduced, and the reaction was heated in a heating mantle for reaction. The reaction temperature was set to 100°C and the reaction was continued for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the unreacted CO2 was slowly released. A few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0024] Example 2 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron, and 0.2 mmol of the quaternary phosphonium salt initiator prepared in Preparation Example 2 were added to a 50 mL high-pressure reactor, 4.0 MPa of CO2 was introduced, and the reaction was heated in a heating mantle for reaction. The reaction temperature was set to 100°C and the reaction was continued for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the unreacted CO2 was slowly released. A few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0025] Example 3 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron, and 0.2 mmol of the quaternary phosphonium salt initiator prepared in Preparation Example 3 were added to a 50 mL high-pressure reactor, 4.0 MPa of CO2 was introduced, and the reaction was heated in a heating mantle. The reaction temperature was set to 100°C and the reaction was continued for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the unreacted CO2 was slowly released. A few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0026] Example 4 Under anhydrous and oxygen-free conditions, 400 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron, and 0.1 mmol of the quaternary phosphonium salt initiator prepared in Preparation Example 1 were added to a 50 mL high-pressure reactor, 2.0 MPa of CO2 was introduced, and the reaction was heated in a heating mantle. The reaction temperature was set to 80°C and the reaction was continued for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the unreacted CO2 was slowly released. A few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0027] Example 5 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.05 mmol of triphenylboron, and 0.2 mmol of the quaternary phosphonium salt initiator prepared in Preparation Example 1 were added to a 50 mL high-pressure reactor, 6.0 MPa of CO2 was introduced, and the reaction was heated in a heating mantle. The reaction temperature was set to 140°C and the reaction was continued for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the unreacted CO2 was slowly released. A few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0028] Comparative Example 1 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron and 0.2 mmol of triethylamine were added to a 50 mL high-pressure reactor, 4.0 MPa of CO2 was introduced, and the reactor was placed in a heating mantle for heating and reaction. The reaction temperature was set at 100°C and the reaction was continued for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, unreacted CO2 was slowly released, and a few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0029] Comparative Example 2 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron and 0.2 mmol of n-butyltriphenylphosphonium bromide initiator were added into a 50 mL high-pressure reactor, 4.0 MPa of CO2 was introduced, and the reactor was placed in a heating mantle for heating and reaction. The reaction temperature was set at 100°C and the reaction was continued for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, unreacted CO2 was slowly released, and a few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0030] Comparative Example 3 Under anhydrous and oxygen-free conditions, 300 mmol of cyclohexene oxide, 0.1 mmol of triphenylboron and 0.2 mmol of tetra-n-butylphosphonium bromide initiator were added into a 50 mL high-pressure reactor, 4.0 MPa of CO2 was introduced, and the reactor was placed in a heating mantle for heating and reaction. The reaction temperature was set at 100°C and the reaction was continued for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, unreacted CO2 was slowly released, and a few drops of glacial acetic acid were added to quench the reaction to obtain a cyclic carbonate. The product was dissolved in dichloromethane, and then the product was placed in a vacuum oven at 40°C for 24 hours after rotary evaporation to obtain the final product, a cyclic carbonate.

[0031] Comparative Example 4 The difference between this comparative example and Example 1 is that the amount used in the components is 0.1 mmol of triphenylborane and 0.8 mmol of the quaternary phosphonium salt initiator prepared in Preparation Example 1, and the other steps and amounts remain unchanged.

[0032] Conversion rate testing After a certain reaction time, samples are taken midway and the conversion rate is calculated through nuclear magnetic resonance testing. The higher the conversion rate, the higher the efficiency of the reaction.

[0033] Table 1 Conversion rate values ​​of Examples 1-5 and Comparative Examples 1-3 after 6 hours of reaction Conversion rate / % Example 1 86％ Example 2 93％ Example 3 89％ Example 4 85％ Example 5 84％ Comparative Example 1 61％ Comparative Example 2 66％ Comparative Example 3 55％ Comparative Example 4 53％ By comparing Examples 1-3 with Comparative Example 1, it can be seen that, under the condition that other reaction conditions remain unchanged, compared with the traditional organic amine initiator, the conversion rate of the target product cyclic carbonate ester prepared by the quaternary ammonium salt initiator of the present invention is greatly improved in the same time. This shows that the present invention can obtain cyclic carbonate esters in a shorter time by using quaternary phosphonium salt initiators and organic boron catalysts, thereby improving the reaction efficiency.

[0034] By comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that, when other reaction conditions remain unchanged, compared with commercial quaternary ammonium salts, the conversion rate of the target product cyclic carbonate ester prepared by the quaternary ammonium salt initiator of the present invention is greatly improved in the same time. This shows that the present invention can obtain cyclic carbonate esters in a shorter time by using quaternary phosphonium salt initiators and organoboron catalysts, thereby improving reaction efficiency.

[0035] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for synthesizing a carbon dioxide-based cyclic carbonate, characterized in that: The steps include: S1, adding cyclohexene oxide and a catalyst into a reactor, replacing the air in the reactor with CO2, adjusting the pressure of the reactor to 2-6 MPa and the temperature to 80-140°C, and reacting; the catalyst comprises a Lewis acid and a Lewis base, and the Lewis base is a quaternary phosphonium salt initiator; S2. After the reaction is completed, cool to room temperature, add a quencher to terminate the reaction, and purify and dry the product to obtain a cyclic carbonate.

2. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 1, characterized in that: The quaternary phosphonium salt initiator is prepared by the following steps: triphenylphosphine, bromoalkane and solvent are reacted in an inert gas atmosphere at a reaction temperature of 60-100° C. After the reaction is completed, excess components are removed, and the mixture is purified and dried to obtain the quaternary phosphonium salt initiator.

3. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 2, characterized in that: The brominated alkane is selected from one of benzyl bromide, p-methoxybenzyl bromide and p-trifluoromethylbenzyl bromide.

4. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 2, characterized in that: The Lewis acid is selected from one of triphenylboron, triethylboron, tributylboron or boron trichloride.

5. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 1, characterized in that: The molar ratio of the Lewis acid to the Lewis base is 1:(1-4).

6. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 2, characterized in that: The solvent is selected from one of acetonitrile, chloroform and dimethyl sulfoxide.

7. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 1, characterized in that: The molar ratio of the cyclohexene oxide to the quaternary phosphonium salt initiator is (1500-4000):

1.

8. The method for synthesizing a carbon dioxide-based cyclic carbonate according to claim 1, characterized in that: The quencher is selected from glacial acetic acid.