Preparation method of ethylene carbonate
The catalysts of magnesium zinc bimetallic oxide and borax zinc were supported by mesoporous silica-carbon composite nano-supports, and the problems of low catalytic efficiency and poor stability in the preparation of vinyl carbonate were solved, and efficient and high-purity vinyl carbonate production was achieved.
Patent Information
- Application Number
- CN202510519198.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-29
AI Technical Summary
The existing vinyl carbonate preparation methods have problems with low product purity and yield, especially the catalyst catalytic efficiency and poor stability in the urea alcoholylation method, resulting in insufficient reaction.
The composite active components of the mesoporous silica-carbon composite nano-supported magnesium zinc bimetal oxide and borax zinc were prepared as catalysts, and the alcoholylation reaction of urea and ethylene glycol was carried out under specific conditions. Combined with ultrasonic assisted impregnation and secondary loading technology, the active site distribution and stability of the catalyst were adjusted.
It significantly improves the reaction rate and yield of vinyl carbonate, while ensuring high purity of the product, and improving the service life and stability of the catalyst.
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Figure BDA0005373422510000121 
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of organic synthesis, and specifically relates to a method for preparing ethylene carbonate. Background Art
[0002] Ethylene carbonate (EC), as an organic solvent and organic synthesis intermediate with excellent properties, has wide applications in the fields of lithium-ion battery electrolytes, pharmaceuticals, coatings, etc.
[0003] With the continuous increase of environmental pressure, the demand and development for environmental protection in all walks of life are also increasing, which has promoted the booming development of the new energy vehicle industry, and the market demand for lithium-ion batteries has surged. As a key component of the electrolyte, ethylene carbonate, its market scale has also been continuously expanding.
[0004] Currently, the methods for preparing ethylene carbonate in industry mainly include the phosgene method, the transesterification method, and the urea alcoholysis method, etc. However, these methods all have certain defects in practical applications, resulting in low product purity and yield.
[0005] The phosgene used in the phosgene method is highly toxic, which not only poses a great harm to the health of operators, but also makes it difficult to treat the chlorine-containing wastewater and waste gas generated during the production process, seriously polluting the environment; the transesterification method requires the use of a large amount of catalysts and organic solvents, and there are side reactions during the reaction process, resulting in great difficulties in product separation and purification and high costs; although the urea alcoholysis method is relatively environmentally friendly, due to the low catalytic efficiency and poor catalytic stability of the existing catalysts, the reaction between urea and ethylene glycol cannot proceed fully, resulting in a low yield of ethylene carbonate.
[0006] Therefore, developing an efficient and stable catalyst to improve the preparation efficiency and product quality of ethylene carbonate has become an urgent problem to be solved. Summary of the Invention
[0007] In view of the problems in the prior art, the present invention provides a method for preparing ethylene carbonate.
[0008] The technical solution adopted by the present invention to solve its technical problems is: a method for preparing ethylene carbonate, the method is to obtain ethylene carbonate through the alcoholysis reaction of urea and ethylene glycol under the action of a specific catalyst;
[0009] The catalyst adopts a mesoporous silica-carbon composite nanocarrier, the pore diameter of the carrier is 5 - 10 nm, the specific surface area ≥ 300 m 2 / g, and is loaded with a composite active component of magnesium-zinc double metal oxide and zinc borate, and the total loading amount of the active component is 30 - 40 wt%.
[0010] As a further technical solution, the mesoporous structure of the mesoporous silica-carbon composite nanocarrier enables high active sites exposure of the active components. Meanwhile, the carbon layer enhances the stability of the carrier and inhibits the sintering of the active components, thereby improving the service life and catalytic efficiency of the catalyst;
[0011] When synthesizing the carrier, methyltrimethoxysilane and sucrose are used as precursors, and mesoporous silica-carbon composite materials are prepared by the sol-gel method, and then the carrier is obtained by calcination.
[0012] As a further technical solution, cetyltrimethylammonium bromide is added as an additive during the sol-gel process of carrier synthesis to regulate the formation of the mesoporous structure, and mesoporous silica-carbon composite materials with a more uniform pore size distribution are prepared, and the carrier is obtained by calcination in a nitrogen atmosphere. This calcination atmosphere helps to improve the surface properties of the carrier.
[0013] As a further technical solution, in the magnesium-zinc bimetallic oxide, Mg 2+ and Zn 2+ synergistically act to precisely regulate the distribution of acidic sites on the catalyst surface, effectively promote the pyrolysis of urea to generate the intermediate hydroxyethyl carbamate, and further provide favorable conditions for the subsequent generation of ethylene carbonate;
[0014] In the step of loading the active components, magnesium acetate and zinc acetate are dissolved in deionized water and added to the carrier for impregnation.
[0015] As a further technical solution, in the step of loading the active components, the carrier is impregnated by ultrasonic-assisted impregnation to make the active components more uniformly loaded on the carrier; borax is used to adjust the pH of the solution, and after stirring, subsequent drying and calcination steps are carried out to optimize the formation of zinc borate.
[0016] As a further technical solution, the preparation method of the catalyst includes the following steps:
[0017] Carrier synthesis: Using methyltrimethoxysilane and sucrose as precursors, a gel is prepared by the sol-gel method, and then the carrier is obtained by calcination at 610 - 630 °C for 2 - 3 h;
[0018] Specifically, methyltrimethoxysilane and sucrose are mixed in a molar ratio of 1:1, and a 50% ethanol solution with a mass 5 times that of sucrose is added as a solvent. At the same time, 1.2% hydrochloric acid based on the mass of the ethanol solution is added as a catalyst, and the mixture is stirred and reacted at 40 °C for 24 h to obtain a sol, and then the sol is dried at 60 °C for 48 h to form a gel;
[0019] Loading of active components:
[0020] Primary loading: Mix Mg(NO3)2·6H2O and Zn(NO3)2·6H2O in a molar ratio of 3:1 - 1.5 and dissolve them in deionized water that is 10 times the mass of the mixture. Then add the above carrier and impregnate it by ultrasonic wave for 12 h, where the mass ratio of the above carrier to deionized water is 1:4 - 5. After impregnation, dry it at 120 °C for 12 h, and then calcine it at 540 - 550 °C for 4.5 h;
[0021] The ultrasonic frequency for ultrasonic impregnation is 40 kHz;
[0022] Secondary loading: Mix Mg(NO3)2·6H2O and Zn(NO3)2·6H2O in a molar ratio of 3:1 - 1.5 and dissolve them in deionized water that is 10 times the mass of the mixture. Add borax to adjust the pH of the solution to 9 - 9.5, stir at 85 °C for 6.5 h, then dry at 120 °C for 12 h, and finally calcine at 552 - 560 °C for 4 h to obtain the catalyst loaded with active components.
[0023] As a further technical solution, cerium nitrate is added as an auxiliary during the secondary loading process, and the addition amount is 0.1 - 0.3 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
[0024] As a further technical solution, the conditions for the urea alcoholysis reaction are as follows:
[0025] The raw materials are proportioned according to a molar ratio of urea to ethylene glycol of 1 - 1.5:1.2 - 1.8;
[0026] Based on the mass of urea, the dosage of the catalyst is 1.5 - 2 wt%;
[0027] The reaction temperature is controlled at 130 - 140 °C;
[0028] The reaction time is 4 - 6 h;
[0029] The reaction is carried out under atmospheric pressure, and N2 is introduced to prevent the oxidation of reactants and products.
[0030] Advantages of the present invention:
[0031] The main core advantage of the method for preparing ethylene carbonate in the present invention lies in the catalyst used. The specially prepared catalyst in the present invention uses mesoporous silica-carbon composite nanomaterials as the carrier, which has unique structural characteristics, a pore diameter of 5 - 10 nm and a specific surface area of ≥300 m 2 / g, providing rich loading sites and a large reaction space for the active components, which is beneficial to the adsorption and diffusion of reactant molecules on the catalyst surface, thereby improving the reaction rate.
[0032] In terms of the loading of active components, a secondary loading method is adopted to make the magnesium-zinc bimetallic oxide and the zinc borate composite active components more evenly distributed on the surface of the carrier. The primary loading first preliminarily attaches the active components to the carrier, and the secondary loading further optimizes the loading form and distribution of the active components by adjusting conditions such as pH, enhances the interaction between the active components and the carrier, and improves the stability of the catalyst. At the same time, cerium nitrate is added as an auxiliary agent during the secondary loading process. Cerium nitrate can change the electronic structure and surface properties of the active components, promote the dispersion of the active components, reduce the agglomeration and sintering of the active components during the reaction process, and thus significantly improve the activity and stability of the catalyst.
[0033] During the catalytic reaction process, the catalyst prepared by the present invention can effectively reduce the activation energy of the urea alcoholysis reaction, enabling the reaction to proceed efficiently under relatively mild conditions. Compared with traditional catalysts, the catalyst of the present invention can significantly increase the reaction rate and conversion rate of urea and ethylene glycol, and while ensuring the product purity, greatly improve the yield of ethylene carbonate. Specific embodiments
[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.
[0035] The method for preparing ethylene carbonate of the present invention prepares ethylene carbonate by the alcoholysis reaction of urea and ethylene glycol under the action of a specific catalyst. This specific catalyst uses a mesoporous silica-carbon composite nanocarrier loaded with a composite active component of magnesium-zinc bimetallic oxide and zinc borate, which can significantly improve the catalytic efficiency of the reaction and the selectivity of the product, thereby preparing ethylene carbonate efficiently and with high purity.
[0036] Raw material preparation
[0037] The raw materials used in this method, such as urea, ethylene glycol, methyltrimethoxysilane, sucrose, cetyltrimethylammonium bromide, magnesium acetate, zinc acetate, Mg(NO2)2·6H2O, Zn(NO3)2·6H2O, borax, cerium nitrate, deionized water, ethanol solution with a mass fraction of 50%, hydrochloric acid, etc., are all commercially available chemically pure or analytically pure reagents.
[0038] Catalyst preparation
[0039] Synthesis of the carrier: Using methyltrimethoxysilane and sucrose as precursors, a gel is prepared by the sol-gel method, and then calcined at 610 - 630 °C for 2 - 3 h to obtain the carrier;
[0040] Specifically, methyltrimethoxysilane and sucrose are mixed in a molar ratio of 1:1, and an ethanol solution with a mass fraction of 50% five times the mass of sucrose is added as a solvent. At the same time, 1.2% of hydrochloric acid based on the mass of the ethanol solution is added as a catalyst. The mixture is stirred and reacted at 40 °C for 24 h to obtain a sol, and then the sol is dried at 60 °C for 48 h to form a gel.
[0041] Loading of active components:
[0042] First loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O are mixed and dissolved in deionized water ten times the mass of the mixture in a molar ratio of 3:1 - 1.5. Then the above carrier is added and ultrasonically impregnated for 12 h, where the mass ratio of the above carrier to deionized water is 1:4 - 5. After impregnation, it is dried at 120 °C for 12 h, and then calcined at 540 - 550 °C for 4.5 h.
[0043] The ultrasonic frequency of ultrasonic impregnation is 40 kHz.
[0044] Second loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O are mixed and dissolved in deionized water ten times the mass of the mixture in a molar ratio of 3:1 - 1.5. Borax is added to adjust the pH of the solution to 9 - 9.5, and it is stirred at 85 °C for 6.5 h. Subsequently, it is dried at 120 °C for 12 h, and finally calcined at 552 - 560 °C for 4 h to obtain a catalyst loaded with active components.
[0045] Cerium nitrate is added as an additive during the second loading process, and the addition amount is 0.1 - 0.3 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
[0046] Preparation steps of ethylene carbonate
[0047] In a reaction kettle equipped with a stirring device, a thermometer and a gas inlet device, these two raw materials are added in a molar ratio of urea to ethylene glycol of 1.2:1.5.
[0048] Based on the mass of urea, 1.8 wt% of the above-prepared catalyst is added.
[0049] The reaction kettle is sealed, and N2 is introduced to prevent the oxidation of reactants and products. The reaction temperature is controlled at 135 °C, the reaction time is 5 h, and the reaction is carried out at atmospheric pressure.
[0050] After the reaction is completed, the reaction solution is cooled to room temperature, and the ethylene carbonate product is separated by methods such as filtration and distillation. Specific examples
[0052] Example 1
[0053] Catalyst preparation:
[0054] Support synthesis: Using methyltrimethoxysilane and sucrose as precursors, a gel was prepared by the sol-gel method and then calcined at 610 °C for 2 h to obtain the support;
[0055] Specifically, methyltrimethoxysilane and sucrose were mixed in a molar ratio of 1:1, and a 50% ethanol solution 5 times the mass of sucrose was added as a solvent. At the same time, 1.2% hydrochloric acid based on the mass of the ethanol solution was added as a catalyst, and the mixture was stirred and reacted at 40 °C for 24 h to obtain a sol. Then the sol was dried at 60 °C for 48 h to form a gel;
[0056] Loading of active components:
[0057] First loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O were mixed and dissolved in deionized water 10 times the mass of the mixture at a molar ratio of 3:1, and then the above support was added and ultrasonically impregnated for 12 h. The mass ratio of the above support to deionized water was 1:4. After impregnation, it was dried at 120 °C for 12 h and then calcined at 540 °C for 4.5 h;
[0058] The ultrasonic frequency of ultrasonic impregnation was 40 kHz;
[0059] Second loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O were mixed and dissolved in deionized water 10 times the mass of the mixture at a molar ratio of 3:1, borax was added to adjust the pH of the solution to 9, and it was stirred at 85 °C for 6.5 h. Subsequently, it was dried at 120 °C for 12 h and finally calcined at 552 °C for 4 h to obtain a catalyst loaded with active components.
[0060] Cerium nitrate was added as an auxiliary during the second loading process, and the addition amount was 0.1 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
[0061] Preparation of ethylene carbonate: 1 mol of urea and 1.25 mol of ethylene glycol were added to the reaction kettle, and a catalyst based on 1.5 wt% of the mass of urea was added. The reaction was carried out at 130 °C and atmospheric pressure for 4 h under N2 protection. After the reaction, the ethylene carbonate product was obtained by separation. The detected yield was 85% and the purity was 98%.
[0062] Example 2
[0063] Catalyst preparation:
[0064] Support synthesis: Using methyltrimethoxysilane and sucrose as precursors, a gel was prepared by the sol-gel method and then calcined at 620 °C for 2.5 h to obtain the support;
[0065] Specifically, methyltrimethoxysilane and sucrose were mixed in a molar ratio of 1:1, and an ethanol solution with a mass fraction of 50% five times the mass of sucrose was added as a solvent. Meanwhile, hydrochloric acid with a mass of 1.2% of the ethanol solution was added as a catalyst, and the mixture was stirred at 40 °C for 24 h to obtain a sol. Then, the sol was dried at 60 °C for 48 h to form a gel;
[0066] Loading of active components:
[0067] First loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O were mixed and dissolved in deionized water ten times the mass of the mixture according to a molar ratio of 3:1.2. Then, the above-mentioned carrier was added and ultrasonically impregnated for 12 h, where the mass ratio of the above-mentioned carrier to deionized water was 1:4.5. After impregnation, it was dried at 120 °C for 12 h, and then calcined at 546 °C for 4.5 h;
[0068] The ultrasonic frequency of ultrasonic impregnation was 40 kHz;
[0069] Second loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O were mixed and dissolved in deionized water ten times the mass of the mixture according to a molar ratio of 3:1.2. Borax was added to adjust the pH of the solution to 9.2, and it was stirred at 85 °C for 6.5 h. Subsequently, it was dried at 120 °C for 12 h, and finally calcined at 555 °C for 4 h to obtain the catalyst loaded with active components.
[0070] During the second loading process, cerium nitrate was added as an auxiliary agent, and the addition amount was 0.2 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
[0071] Preparation of ethylene carbonate: 1 mol of urea and 1.5 mol of ethylene glycol were added to the reaction kettle, and a catalyst based on 1.8 wt% of the mass of urea was added. The reaction was carried out at 135 °C and atmospheric pressure for 5 h under N2 protection. After the reaction, the ethylene carbonate product was obtained through separation. After detection, the yield was 90% and the purity was 99%.
[0072] Example 3
[0073] Catalyst preparation:
[0074] Synthesis of carrier: Using methyltrimethoxysilane and sucrose as precursors, a gel was prepared by the sol-gel method, and then the carrier was obtained by calcining at 630 °C for 3 h;
[0075] Specifically, methyltrimethoxysilane and sucrose were mixed in a molar ratio of 1:1, and an ethanol solution with a mass fraction of 50% five times the mass of sucrose was added as a solvent. At the same time, 1.2% of the mass of the ethanol solution of hydrochloric acid was added as a catalyst, and the mixture was stirred and reacted at 40 °C for 24 h to obtain a sol. Then, the sol was dried at 60 °C for 48 h to form a gel;
[0076] Loading of active components:
[0077] First loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O were mixed and dissolved in deionized water ten times the mass of the mixture according to a molar ratio of 3:1.5, and then the above-mentioned carrier was added and ultrasonically impregnated for 12 h. The mass ratio of the above-mentioned carrier to deionized water was 1:5. After impregnation, it was dried at 120 °C for 12 h, and then calcined at 550 °C for 4.5 h;
[0078] The ultrasonic frequency of ultrasonic impregnation was 40 kHz;
[0079] Second loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O were mixed and dissolved in deionized water ten times the mass of the mixture according to a molar ratio of 3:1.5, borax was added to adjust the pH of the solution to 9.5, and it was stirred at 85 °C for 6.5 h. Subsequently, it was dried at 120 °C for 12 h, and finally calcined at 560 °C for 4 h to obtain a catalyst loaded with active components.
[0080] Cerium nitrate was added as an auxiliary agent during the second loading process, and the addition amount was 0.3 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
[0081] Preparation of ethylene carbonate: 1 mol of urea and 1.75 mol of ethylene glycol were added to the reaction kettle, and a catalyst based on 2 wt% of the mass of urea was added. The reaction was carried out at 140 °C and atmospheric pressure for 6 h under N2 protection. After the reaction, the ethylene carbonate product was obtained by separation. After detection, the yield was 92% and the purity was 99.2%.
[0082] The following are comparative examples:
[0083] Comparative example 1
[0084] The difference from Example 2 was that a common commercial catalyst (zinc oxide) was used, and the rest of the operations were the same. The yield of the finally obtained ethylene carbonate product was 70%, and the purity was 95.1%, indicating that the catalyst prepared by the present invention had better catalytic performance.
[0085] Comparative example 2
[0086] The difference from Example 2 is that cerium nitrate promoter is not added during the catalyst preparation process, and the rest of the operations are the same. The yield of the ethylene carbonate product obtained from the reaction is 80%, and the purity is 97.4%, indicating that the cerium nitrate promoter helps to improve the activity and stability of the catalyst.
[0087] Comparative Example 3
[0088] Catalyst preparation:
[0089] Support synthesis: Using methyltrimethoxysilane and sucrose as precursors, a gel is prepared by the sol-gel method, and then calcined at 610 °C for 2 h to obtain the support;
[0090] Specifically, methyltrimethoxysilane and sucrose are mixed in a molar ratio of 1:1, and a 50% ethanol solution with a mass 5 times that of sucrose is added as a solvent. At the same time, 1.2% hydrochloric acid based on the mass of the ethanol solution is added as a catalyst, and the mixture is stirred and reacted at 40 °C for 24 h to obtain a sol. Then the sol is dried at 60 °C for 48 h to form a gel;
[0091] Active component loading:
[0092] First loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O are mixed and dissolved in deionized water with a mass 10 times that of the mixture in a molar ratio of 3:1, and then the above support is added and ultrasonically impregnated for 12 h. The mass ratio of the above support to deionized water is 1:4. After impregnation, it is dried at 120 °C for 12 h, and then calcined at 540 °C for 4.5 h to obtain a catalyst loaded with active components; the ultrasonic frequency of ultrasonic impregnation is 40 kHz.
[0093] During the second loading process, cerium nitrate is added as a promoter, and the addition amount is 0.1 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
[0094] Ethylene carbonate preparation: 1 mol of urea and 1.25 mol of ethylene glycol are added to the reaction kettle, and a catalyst based on 1.5 wt% of the mass of urea is added. The reaction is carried out at 130 °C and atmospheric pressure for 4 h under N2 protection. After the reaction, the ethylene carbonate product is obtained through separation. The yield of the ethylene carbonate product obtained from the reaction is 71%, and the purity is 90.6%, indicating that the second loading helps to improve the activity of the catalyst.
[0095] Experiment
[0096] Purity detection experiment
[0097] Test method: Referring to the detection principle of high performance liquid chromatography (HPLC) in "GB / T 22388-2008 Detection Methods for Melamine in Raw Milk and Dairy Products", and combining with the instrument operation specifications of "GB / T 37109-2018 General Rules for Chemical Reagents - High Performance Liquid Chromatographic Analysis", the purity of the products in Examples 1-3 and Comparative Examples 1-2 was detected. An octadecylsilane chemically bonded silica gel column (4.6×250 mm, 5 μm) was used, the mobile phase was acetonitrile-water (volume ratio 15:85), the flow rate was 1.0 mL / min, the column temperature was 30 °C, the detection wavelength was 243 nm, and the injection volume was 10 μL. A standard curve was plotted with ethylene carbonate standard, and the sample purity was calculated by the external standard method of peak area:
[0098] Table 1
[0099] Purity % Example 1 98.0 Example 2 99.0 Example 3 99.2 Comparative Example 1 95.1 Comparative Example 2 97.4 Comparative Example 3 90.6
[0100] As can be seen from the data in the table, the products obtained by the present invention have high purity.
[0101] Catalytic efficiency test experiment
[0102] Test method: The initial reaction rates of the catalysts in Examples 1-3 and Comparative Examples 1-2 during the reaction were measured respectively. Under the same reaction conditions (molar ratio of urea to ethylene glycol 1.2:1.5, temperature 135 °C, normal pressure, introducing N2), by monitoring the change of the reactant concentration in the reaction system with time, the initial reaction rate was calculated:
[0103] Table 2
[0104]
[0105]
[0106] As can be seen from Table 2, the catalyst used in the method of the present invention has high catalytic efficiency.
[0107] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing ethylene carbonate, characterized in that, The method prepares ethylene carbonate through the alcoholysis reaction of urea and ethylene glycol under the action of a specific catalyst; The catalyst uses a mesoporous silica-carbon composite nanocarrier, the pore diameter of the carrier is 5-10 nm, the specific surface area is ≥ 300 m 2 / g, and is loaded with a composite active component of magnesium-zinc bimetallic oxide and zinc borate, and the total loading amount of the active component is 30-40 wt%.
2. The preparation method of ethylene carbonate according to claim 1, characterized in that, When synthesizing the carrier, the precursors are methyltrimethoxysilane and sucrose, and a mesoporous silica-carbon composite material is prepared by the sol-gel method, and then the carrier is obtained by calcination.
3. The preparation method of ethylene carbonate according to claim 2, characterized in that, During the sol-gel process of synthesizing the carrier, cetyltrimethylammonium bromide is added as an additive to regulate the formation of the mesoporous structure, prepare a mesoporous silica-carbon composite material with a more uniform pore size distribution, and obtain the carrier by calcination under a nitrogen atmosphere.
4. The preparation method of ethylene carbonate according to claim 1, characterized in that In the step of loading the active component, magnesium acetate and zinc acetate are dissolved in deionized water and added to the carrier for impregnation.
5. The preparation method of ethylene carbonate according to claim 4, wherein, In the step of loading the active component, the carrier is impregnated by ultrasonic-assisted impregnation to make the active component more evenly loaded on the carrier; Borax is used to adjust the pH of the solution, and after stirring, subsequent drying and calcination steps are carried out.
6. The preparation method of ethylene carbonate according to claim 1, characterized in that, The preparation method of the catalyst includes the following steps: Carrier synthesis: Using methyltrimethoxysilane and sucrose as precursors, a gel is prepared by the sol-gel method, and then the carrier is obtained by calcining at 610-630 °C for 2-3 h; Specifically, methyltrimethoxysilane and sucrose are mixed in a molar ratio of 1:1, and a 50% ethanol solution with a mass 5 times that of sucrose is added as a solvent. At the same time, 1.2% hydrochloric acid based on the mass of the ethanol solution is added as a catalyst, and the reaction is stirred at 40 °C for 24 h to obtain a sol, and then the sol is dried at 60 °C for 48 h to form a gel; Active component loading: First loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O are mixed and dissolved in deionized water with a mass 10 times that of the mixture according to a molar ratio of 3:1-1.5, and then the above carrier is ultrasonically impregnated for 12 h, where the mass ratio of the above carrier to deionized water is 1:4-5. After impregnation, it is dried at 120 °C for 12 h, and then calcined at 540-550 °C for 4.5 h; The ultrasonic frequency of ultrasonic impregnation is 40 kHz; Second loading: Mg(NO3)2·6H2O and Zn(NO3)2·6H2O are mixed and dissolved in deionized water with a mass 10 times that of the mixture according to a molar ratio of 3:1-1.5, borax is added to adjust the pH of the solution to 9-9.5, stirred at 85 °C for 6.5 h, then dried at 120 °C for 12 h, and finally calcined at 552-560 °C for 4 h to obtain a catalyst loaded with active components.
7. The preparation method of ethylene carbonate according to claim 6, wherein, Cerium nitrate is added as an auxiliary agent during the second loading process, and the addition amount is 0.1-0.3 wt% of the total mass of the active components to improve the activity and stability of the catalyst.
8. A method for preparing ethylene carbonate according to claim 1, characterized in that, The conditions for the urea alcoholysis reaction are as follows: The raw materials are proportioned according to a molar ratio of urea to ethylene glycol of 1-1.5:1.2-1.8; Based on the mass of urea, the dosage of the catalyst is 1.5-2 wt%; The reaction temperature is controlled at 130-140 °C; The reaction time is 4-6 h; The reaction is carried out under normal pressure, and N2 is introduced to prevent the oxidation of reactants and products.