Preparation method for carbonate compound

Abstract

The present invention relates to the field of chemical engineering, and discloses a preparation method for a carbonate compound. Firstly, a cerium dioxide catalyst prepared in the present invention is of a uniformly distributed nanorod structure, and has a great number of surface oxygen vacancies and acid-base active sites; under mild conditions, the catalyst exhibits good catalytic performance in the reaction of the carbonate compound; moreover, the catalyst of the present invention has low raw material prices and stable properties, and can be reused many times. Secondly, a method for preparing dimethyl carbonate by means of a direct reaction of methanol with CO2 and a method for preparing ethylene carbonate by means of a direct reaction of ethylene glycol with CO2 are used in the present invention; and the methods have low raw material prices, a high atom utilization rate, environmental friendliness and economic efficiency, and are therefore suitable for industrial production.

Description

Preparation method of carbonate compound TECHNICAL FIELD

[0001] The present application relates to the chemical industry field, and particularly relates to a preparation method of a carbonate compound. BACKGROUND

[0002] Dimethyl carbonate (DMC) and ethylene carbonate (EC) are both important organic carbonate compounds. Among them, dimethyl carbonate has low vapor pressure, high oxygen content, high octane value, high dielectric constant, low toxicity, low viscosity, fast evaporation rate, rich functional groups, good reaction activity and other excellent performances, and can be applied to many fields such as medicine, pesticide, paint, polycarbonate and the like. At the same time, ethylene carbonate is also applied to many fields due to its excellent physical and chemical properties. For example, EC can be used as a decarbonizing agent in the fields of natural gas, synthetic gas and the like; as a good absorbent and solvent of organic matter; as a lithium ion battery electrolyte used in the battery industry field; and can also be used as a plasticizer, spinning solvent, oily solvent, olefin and aromatic hydrocarbon extraction agent and the like.

[0003] Traditional dimethyl carbonate synthesis methods mainly include: phosgene method, urea alcoholysis method, ester exchange method, methanol oxidative carbonylation method, but the above methods all have serious defects. The method of synthesizing DMC by directly reacting CO2 and methanol has low raw material price, high atom utilization rate, green environmental protection and strong economy. From the perspective of sustainable development and green chemistry, the one-step method of synthesizing DMC from CO2 and methanol is a very promising way. However, CO2 has stable chemical properties, is difficult to activate, and the Gibbs free energy of the reaction is positive, which is limited by the thermodynamic equilibrium.

[0004] Traditional synthesis methods of ethylene carbonate mainly include: phosgene synthesis method, ester exchange method, halogenated alcohol method, direct oxidation of ethylene and carbon dioxide, ring addition of oxirane and carbon dioxide, urea alcoholysis method, etc. For example, a patent with publication number CN113842858A discloses a reaction tower with a reaction shallow pool, which uses the urea alcoholysis method to prepare ethylene carbonate. The staged reaction greatly improves the yield of ethylene carbonate, which can be as high as more than 95%. However, this method has high cost, and the by-product ammonia gas leads to catalyst deactivation or dissolution, and the separation process is complex. A patent with publication number CN107915707A discloses a method for preparing ethylene carbonate by using a bimetallic catalyst M1O, M2O (wherein M1 is at least one selected from Ca, Mg, Sr or Ba; M2 is at least one selected from Zr or Ti), and adopting the ring addition of oxirane and carbon dioxide. The method improves the catalytic activity, and can achieve 96.8% conversion rate of oxirane and 98.7% selectivity of ethylene carbonate. However, this method has harsh production operating conditions, high risk coefficient of raw material oxirane, and many by-products. Other preparation methods also have their own serious shortcomings, for example, the phosgene method has high toxicity of raw materials, and the by-products have corrosion effect on equipment; the ester exchange method has expensive raw materials and large environmental pollution in production process; the halogenated alcohol method has harsh reaction conditions and many by-products; the direct oxidation of ethylene and carbon dioxide has complex production process and explosion risk.

[0005] In summary, it is of great significance to develop high-efficiency catalysts for carbonate compounds. At present, various catalysts can be used for the synthesis of carbonate compounds, such as metal organic framework materials, supported catalysts, and metal oxides. CeO2-based catalysts are considered to be suitable for this reaction because they have abundant surface acid-base sites and surface oxygen vacancies, and have become a research hotspot. However, the catalytic performance of existing CeO2-based catalysts needs to be further improved, and the reaction conditions are still harsh, which cannot be applied to industrial production. Therefore, it is extremely important to prepare catalysts that can obtain higher yield of carbonate compounds under milder reaction conditions by changing the preparation method of the catalysts.

[0006] SUMMARY

[0007] To solve the above technical problems, the present application provides a preparation method of carbonate compounds. First, the cerium dioxide catalyst prepared by the present application has a uniform distribution of nanorod structure, has numerous surface oxygen vacancies and acid-base active sites, and exhibits good catalytic performance in the reaction of carbonate compounds under mild conditions. In addition, the catalyst prepared by the present application has low raw material price and stable properties, and can be repeatedly used. Second, the present application adopts the method of directly reacting methanol and CO2 to prepare dimethyl carbonate and the method of directly reacting ethylene glycol and CO2 to prepare ethylene carbonate. The above methods have low raw material price, high atomic utilization rate, green environmental protection, and strong economic efficiency, and are suitable for industrial production.

[0008] The specific technical scheme of the present application is:

[0009] In a first aspect, the present application provides a preparation method of carbonate compounds, using a cobalt-doped nanorod ceria catalyst, the preparation method of the catalyst comprising the following steps: dissolving a trivalent cerium salt and / or its hydrate and a divalent cobalt salt and / or its hydrate in water to obtain a cobalt-cerium mixed solution; under stirring conditions, adding the cerium-cobalt mixed solution dropwise into a NaOH solution, then stirring the obtained mixed solution under sealing; then hydrothermally aging the obtained mixture, centrifugally separating, filtering to collect the solid product, and washing, drying and calcining to obtain the cobalt-doped nanorod ceria catalyst.

[0010] The ceria catalyst prepared by the present application has a uniform nanorod structure, has numerous surface oxygen vacancies and acid-base active sites, and exhibits good catalytic performance in the reaction of carbonate compounds under mild conditions. Meanwhile, the catalyst raw material is low in price and stable in properties, and can be repeatedly used for multiple times.

[0011] Preferably, the molar ratio of the trivalent cerium salt and / or its hydrate to the divalent cobalt salt and / or its hydrate is 0.03-0.1:1, calculated based on the molar amount of cobalt atoms and cerium atoms.

[0012] Preferably, the trivalent cerium salt and / or its hydrate is cerium nitrate hexahydrate, and the divalent cobalt salt and / or its hydrate is cobalt nitrate hexahydrate.

[0013] Preferably, the molar ratio of the trivalent cerium salt and / or its hydrate to the divalent cobalt salt and / or its hydrate is 0.03-0.1:1, calculated based on the molar amount of cobalt atoms and cerium atoms.

[0014] Preferably, the use amount ratio of the cerium nitrate hexahydrate to water is 3-5 g:20-40 mL.

[0015] Preferably, the ratio of NaOH to water in the NaOH solution is 45-55 g:150-250 mL.

[0016] Preferably, the stirring time of the mixed solution is 20-40 min, and the stirring temperature is 20-40℃.

[0017] Preferably, the hydrothermal aging time is 8-15 h.

[0018] Preferably, the centrifugal separation speed is 8000-10000 rpm.

[0019] Preferably, the drying is freeze-drying, and the time is 20-25 h.

[0020] As preferred, the temperature of the calcination is 500-700℃, and the time is 3-10h; the calcination atmosphere is air, hydrogen, or nitrogen. Preferably, the atmosphere is air.

[0021] In a second aspect, the present application provides a method for preparing dimethyl carbonate, comprising the following steps: taking CO2 and methanol as raw materials, taking the cobalt-doped nanorod-like ceria catalyst prepared by the method of any one of claims 1-4 as a catalyst, taking 2-cyanopyridine (2-CP) as a dehydrating agent, and obtaining dimethyl carbonate after the reaction.

[0022] The reaction equation of the above process is as follows:

[0023] Compared with the existing catalysts, the catalyst used in the above preparation method of the present application has a uniform nanorod-like structure, a large number of surface oxygen vacancies, and acid-base active sites, and can exhibit good catalytic performance in the esterification reaction of methanol and CO2 under mild conditions. Coupling with the dehydration reaction can greatly improve the product yield. At the same time, the catalyst of the present application has low raw material price and stable properties, and can be repeatedly used. Compared with the traditional method, the method for preparing dimethyl carbonate by directly reacting methanol and CO2 in the present application has low raw material price, high atom utilization rate, green environmental protection, and strong economic efficiency, and is suitable for industrial production.

[0024] As preferred, the mass ratio of the methanol, 2-cyanopyridine, and cobalt-doped nanorod-like ceria catalyst is 8-20:8-20:0.1-0.5; further preferably, 8-16:8-16:0.1-0.3.

[0025] As preferred, the reaction pressure is 1-4MPa, the reaction temperature is 100-160℃, and the reaction time is 1-8h; further preferably, the reaction pressure is 2-3MPa, the reaction temperature is 120-140℃, and the reaction time is 4-6h.

[0026] In a third aspect, the present application provides a method for preparing ethylene carbonate, comprising the following steps:

[0027] 1) taking CO2 and ethylene glycol (EG) as raw materials, taking the cobalt-doped nanorod-like ceria catalyst prepared by the method of any one of claims 1-4 as a catalyst, taking 2-cyanopyridine (2-CP) as a dehydrating agent, and performing a cyclization dehydration reaction in a solvent to prepare ethylene carbonate.

[0028] 2) simultaneously coupling the hydration reaction of the dehydrating agent 2-cyanopyridine, and the 2-cyanopyridine is hydrated to generate 2-pyridinecarboxamide (2-PA).

[0029] The reaction equation of the above process is as follows:

[0030] The catalyst prepared by the present application has a small size, a uniform nanorod structure, and a large number of surface oxygen vacancies and acid-base sites, can effectively adsorb and activate ethylene glycol and CO2, can effectively catalyze the reaction of ethylene glycol and CO2, and can obtain ethylene carbonate with high yield and selectivity by cooperating with a dehydrating agent. The method for preparing ethylene carbonate by directly reacting ethylene glycol and CO2 in the present application overcomes the shortcomings of traditional methods, such as expensive raw materials, harsh reaction conditions, difficult product separation, environmental pollution, etc., and is suitable for industrial production.

[0031] Preferably, the molar ratio of the ethylene glycol to the 2-cyanopyridine is 1:1.5-3.

[0032] Preferably, the ratio of the amount of the ethylene glycol to the solvent is 1-3 mmol: 1-4 mL.

[0033] Preferably, the ratio of the amount of the catalyst to the ethylene glycol is 1-3 g: 50-150 mmol.

[0034] Preferably, the solvent is one of tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0035] Preferably, the reaction pressure of the cyclization dehydration reaction is 1-4 MPa, the reaction temperature is 100-160℃, the reaction time is 0.5-5 h, and the reaction is carried out at a stirring speed of 400-800 rpm. Further preferably, the reaction pressure of the cyclization dehydration reaction is 3-4 MPa, the reaction temperature is 120-140℃, and the reaction time is 1-2 h.

[0036] Preferably, the method for preparing ethylene carbonate further comprises the following steps: separating 2-pyridine carboxamide from the product, and further recycling 2-cyanopyridine by a dehydration reaction.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] (1) Compared with the existing catalyst, the catalyst prepared by the present application has a uniform nanorod structure, a large number of surface oxygen vacancies and acid-base active sites, and good catalytic performance in carbonate compound reactions under mild conditions. In addition, the catalyst has low raw material price and stable properties, and can be repeatedly used.

[0039] (2) Compared with the traditional method, the present application adopts a method for preparing dimethyl carbonate by directly reacting methanol and CO2 and a method for preparing ethylene carbonate by directly reacting ethylene glycol and CO2. The above-mentioned methods have low raw material price, high atomic utilization rate, environmental protection, and strong economic efficiency, and are suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a SEM image of CeO2 and 5% Co-CeO2 catalyst prepared in Example 3 of the present application.

[0041] Figure 2 is an XRD image of Co-CeO2 catalyst prepared in Examples 1-5 of the present application.

[0042] Figure 3 is a recycling use of 5% Co-CeO2 catalyst prepared in Example 3 of the present application during the reaction process.

[0043] Figure 4 is a process flow diagram for preparing ethylene carbonate according to the present application.

[0044] Figure 5 is a TEM image and particle size distribution of 5% Co-CeO2 catalyst prepared in Example 16 of the present application.

[0045] Figure 6 is a HAADF image of 5% Co-CeO2 catalyst prepared in Example 16 of the present application.

[0046] Figure 7 is a mechanism diagram of the reaction of CO2 and ethylene glycol catalyzed by 5% Co-CeO2 catalyst of the present application to prepare ethylene carbonate. DETAILED DESCRIPTION

[0047] The present application will be further described below with reference to examples.

[0048] (I) Preparation of dimethyl carbonate

[0049] Example 1

[0050] Cerium nitrate (III) hexahydrate with an atomic molar ratio of cobalt to cerium of 0.01:1 (wherein the mass of cerium nitrate (III) hexahydrate is 4.3 g) was dissolved in 25 mL of deionized water together with cobalt nitrate (II) hexahydrate, and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the cerium nitrate and cobalt nitrate mixed solution was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. Then the mixture was transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with anhydrous ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600°C for 5 hours. After calcination, the target 1% Co-CeO2 catalyst was obtained, and the XRD image of the product is shown in Figure 2.

[0051] Dimethyl carbonate was prepared in a 50 mL stirred tank reactor using 1% Co-CeO2catalyst for the reaction of CO2and methanol. The amount of methanol was 12 g, the amount of 2-cyanopyridine (2-CP) was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The results of the reaction are shown in Table 1.

[0052] Example 2

[0053] Cerium nitrate (III) hexahydrate with an atomic molar ratio of cobalt to cerium of 0.03:1 (wherein the mass of cerium nitrate (III) hexahydrate was 4.3 g) was dissolved in 25 mL of deionized water along with cobalt (II) nitrate hexahydrate, and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the cerium nitrate and cobalt nitrate mixed solution was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 hours. The target 3% Co-CeO2catalyst was obtained after calcination, and the product XRD pattern is shown in Figure 2.

[0054] Dimethyl carbonate was prepared in a 50 mL stirred tank reactor using 3% Co-CeO2catalyst for the reaction of CO2and methanol. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The results of the reaction are shown in Table 1.

[0055] Example 3

[0056] Cerium nitrate (III) hexahydrate (4.3 g) with cobalt atomic molar ratio of 0.05:1 was dissolved in 25 mL of deionized water along with cobalt nitrate (II) hexahydrate and 48 g of NaOH was dissolved in 175 mL of deionized water. The mixed solution of cerium nitrate and cobalt nitrate was added dropwise to the NaOH solution under stirring condition and then the mixed solution was sealed and stirred for 30 min at room temperature. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral, respectively. After pre-freezing, the product was dried by a freeze-dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 h. The target 5% Co-CeO2catalyst was obtained after calcination, and the SEM image of the 5% Co-CeO2catalyst (right) in Example 1 is shown in Figure 1, and the product XRD pattern is shown in Figure 2.

[0057] Dimethyl carbonate was prepared by catalyzing CO2and methanol with 5% Co-CeO2in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0058] Example 4

[0059] Cerium nitrate (III) hexahydrate (4.3 g) with cobalt atomic molar ratio of 0.05:1 was dissolved in 25 mL of deionized water along with cobalt nitrate (II) hexahydrate and 48 g of NaOH was dissolved in 175 mL of deionized water. The mixed solution of cerium nitrate and cobalt nitrate was added dropwise to the NaOH solution under stirring condition and then the mixed solution was sealed and stirred for 30 min at room temperature. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral, respectively. After pre-freezing, the product was dried by a freeze-dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 h. The target 5% Co-CeO2catalyst was obtained after calcination, and the SEM image of the 5% Co-CeO2catalyst (right) in Example 1 is shown in Figure 1, and the product XRD pattern is shown in Figure 2.

[0060] Dimethyl carbonate was prepared by catalyzing CO2and methanol with 5% Co-CeO2in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0061] Example 5

[0062] Cerium nitrate (III) hexahydrate (4.3 g) with cobalt nitrate (II) hexahydrate in the atomic molar ratio of 0.15:1 was dissolved in 25 mL of deionized water, and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the mixed solution of cerium nitrate and cobalt nitrate was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with anhydrous ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 hours. The target 15% Co-CeO2catalyst was obtained after calcination, and the product XRD pattern is shown in Figure 2.

[0063] In a 50 mL stirred tank, dimethyl carbonate was prepared by catalyzing the reaction of CO2and methanol with 15% Co-CeO2. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0064] Example 6

[0065] Cerium nitrate (III) hexahydrate (4.3 g) with cobalt nitrate (II) hexahydrate in the atomic molar ratio of 0.15:1 was dissolved in 25 mL of deionized water, and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the mixed solution of cerium nitrate and cobalt nitrate was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with anhydrous ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 hours. The target 15% Co-CeO2catalyst was obtained after calcination, and the product XRD pattern is shown in Figure 2.

[0066] In a 50 mL stirred tank, dimethyl carbonate was prepared by catalyzing the reaction of CO2and methanol with 15% Co-CeO2. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0067] Example 7

[0068] Example 5

[0069] Example 6

[0070] Example 7

[0071] Example 8

[0072] Example 9

[0073] Example 10

[0074] Example 11

[0075] Example 12

[0076] Example 13

[0077] Cerium nitrate (III) hexahydrate (4.3 g) with cobalt (II) nitrate hexahydrate in a molar ratio of 0.05:1 was dissolved in 25 mL of deionized water, and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the cerium nitrate and cobalt nitrate mixed solution was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. Then the mixture was transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with anhydrous ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in nitrogen at 600 °C for 5 h. The target 5% Co-CeO2-N catalyst was obtained after calcination.

[0078] Dimethyl carbonate was prepared by catalyzing CO2 and methanol with 5% Co-CeO2-N in a 50 mL stirred tank. The amount of methanol was 12 g, the amount of 2-CP was 15 g, the amount of catalyst was 0.2 g, the reaction pressure was 2 MPa, the reaction temperature was 130 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0079] Example 11

[0080] The preparation method of the 5% Co-CeO2catalyst was the same as that of Example 3.

[0081] Dimethyl carbonate was prepared by catalyzing CO2 and methanol with 5% Co-CeO2-N in a 50 mL stirred tank. The amount of methanol was 12 g, the amount of 2-CP was 9 g, the amount of catalyst was 0.2 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0082] Example 12

[0083] The preparation method of the 5% Co-CeO2catalyst was the same as that of Example 3.

[0084] Dimethyl carbonate was prepared by catalyzing CO2 and methanol with 5% Co-CeO2-N in a 50 mL stirred tank. The amount of methanol was 12 g, the amount of 2-CP was 15 g, the amount of catalyst was 0.2 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0085] Example 13

[0086] The preparation method of the 5% Co-CeO2catalyst was the same as that of Example 3.

[0087] Dimethyl carbonate was prepared by reacting CO2 and methanol with 5% Co-CeO2 catalyst in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 15 g, the amount of catalyst was 0.2 g, the reaction pressure was 2 MPa, the reaction temperature was 110 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0088] Example 14

[0089] The 5% Co-CeO2 catalyst was prepared according to the method of Example 3.

[0090] Dimethyl carbonate was prepared by reacting CO2 and methanol with 5% Co-CeO2 catalyst in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 15 g, the amount of catalyst was 0.2 g, the reaction pressure was 3 MPa, the reaction temperature was 130 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0091] Example 15

[0092] The 5% Co-CeO2 catalyst was prepared according to the method of Example 3.

[0093] Dimethyl carbonate was prepared by reacting CO2 and methanol with 5% Co-CeO2 catalyst in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 15 g, the amount of catalyst was 0.2 g, the reaction pressure was 2 MPa, the reaction temperature was 130 °C, the reaction time was 3 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0094] Comparative Example 1

[0095] Ce(NO3)3.6H2O 4.3 g was dissolved in 25 mL of deionized water, and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the cerium nitrate solution was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with anhydrous ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 hours. The target CeO2 catalyst was obtained after calcination, and the SEM image of CeO2 is shown on the left side of Figure 1.

[0096] Dimethyl carbonate was prepared by reacting CO2 and methanol with CeO2 catalyst in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0097] Comparative Example 2

[0098] Cerium nitrate (III) hexahydrate (4.3 g) with an atomic molar ratio of iron to cerium of 0.05:1 was dissolved in 25 mL of deionized water along with iron nitrate (III) nonahydrate (0.5 g), and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the mixed solution of cerium nitrate and iron nitrate was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 h. The target 5% Fe-CeO2catalyst was obtained after calcination.

[0099] Dimethyl carbonate was prepared by catalyzing the reaction of CO2 and methanol with 5% Fe-CeO2. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0100] Comparative Example 3

[0101] Cerium nitrate (III) hexahydrate (4.3 g) with an atomic molar ratio of iron to cerium of 0.05:1 was dissolved in 25 mL of deionized water along with iron nitrate (III) nonahydrate (0.5 g), and 48 g of NaOH was dissolved in 175 mL of deionized water. Under stirring conditions, the mixed solution of cerium nitrate and iron nitrate was added dropwise to the NaOH solution, and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral. After pre-freezing, it was dried by a freeze dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 h. The target 5% Fe-CeO2catalyst was obtained after calcination.

[0102] Dimethyl carbonate was prepared by catalyzing the reaction of CO2 and methanol with 5% Fe-CeO2. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0103] Comparative Example 4

[0104] Cerium nitrate (III) hexahydrate (4.3 g) with atomic molar ratio of lanthanum to cerium of 0.05:1 was dissolved in 25 mL of deionized water along with lanthanum nitrate (III) hexahydrate and 48 g of NaOH was dissolved in 175 mL of deionized water. The mixed solution of cerium nitrate and lanthanum nitrate was added dropwise to the NaOH solution under stirring condition and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral, respectively. After pre-freezing, it was dried by a freeze-dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 hours. The target 5% La-CeO2catalyst was obtained after calcination.

[0105] Dimethyl carbonate was prepared by catalyzing CO2and methanol with 5% La-CeO2in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0106] Comparative Example 5

[0107] Cerium nitrate (III) hexahydrate (4.3 g) with atomic molar ratio of lanthanum to cerium of 0.05:1 was dissolved in 25 mL of deionized water along with lanthanum nitrate (III) hexahydrate and 48 g of NaOH was dissolved in 175 mL of deionized water. The mixed solution of cerium nitrate and lanthanum nitrate was added dropwise to the NaOH solution under stirring condition and then the mixed solution was sealed and stirred at room temperature for 30 min. The mixture was then transferred to an autoclave for aging for 12 h. The turbid liquid was separated using a centrifuge. The product was collected by filtration and washed with absolute ethanol and deionized water until neutral, respectively. After pre-freezing, it was dried by a freeze-dryer for 24 h. Finally, the obtained nanoparticles were calcined in air at 600 °C for 5 hours. The target 5% La-CeO2catalyst was obtained after calcination.

[0108] Dimethyl carbonate was prepared by catalyzing CO2and methanol with 5% La-CeO2in a 50 mL stirred tank reactor. The amount of methanol was 12 g, the amount of 2-CP was 12.5 g, the amount of catalyst was 0.1 g, the reaction pressure was 3.5 MPa, the reaction temperature was 140 °C, the reaction time was 4 h, and the stirring speed was 500 rpm. The reaction results are shown in Table 1.

[0109] Performance Comparison

[0110] Table 1

[0111] As shown in Table 1, compared with Comparative Examples 1-5 using different catalysts, each of the examples uses cobalt-doped nanorod ceria as a catalyst, 2-CP as a dehydrating agent, and catalyzes the direct synthesis of DMC from methanol and carbon dioxide, and the yield of DMC can reach 61.9% (Example 8), which is far superior to the previously reported results, and the reaction conditions are more mild. It is shown that the catalyst is a highly efficient DMC synthesis catalyst, and is expected to become an ideal material for the resource utilization of CO2.

[0112] The 5% Co-CeO2 prepared in Example 3 was further subjected to recyclability study, and the results are shown in Figure 3. As shown in the figure, after 5 cycles, the yield and selectivity of the catalytic system remained at a high level, and there was basically no difference compared with the fresh catalyst. It is shown that the 5% Co-CeO2 catalyst has good stability for the reaction system of DMC directly generated from CO2 and methanol.

[0113] (ii) Preparation of ethylene carbonate

[0114] Figure 4 is a process flow diagram for preparing ethylene carbonate according to the present application. The process is as follows: CO2, EG, catalyst, dehydrating agent and solvent are mixed, and CO2 and ethylene glycol undergo cyclization and dehydration reaction under the action of the catalyst. After the reaction is completed, gas-liquid separation is performed, and the obtained carbon dioxide is returned to the cyclization and dehydration reaction for continuous use. The obtained liquid material is further separated in a separation unit to obtain a solution of 2-PA and a crude product of ethylene carbonate (EC). The crude product of ethylene carbonate (EC) is refined to obtain an EC product, and the solution of 2-PA obtained in the separation unit is subjected to solvent recovery, and the obtained solvent is returned to the cyclization and dehydration reaction for continuous use. At the same time, the 2-PA after solvent recovery is subjected to dehydrating agent regeneration, and the obtained dehydrating agent is used in the cyclization and dehydration reaction. The whole process realizes the use of dehydrating agent and solvent.

[0115] Example 16

[0116] Cobalt(II) nitrate hexahydrate and cerium(III) nitrate hexahydrate with an atomic molar ratio of cobalt to cerium of 0.05:1 (wherein the mass of cerium(III) nitrate hexahydrate is 4.3 g) were dissolved in 25 ml of deionized water, and 48 g of NaOH was dissolved in 175 ml of deionized water. The mixed solution of cerium nitrate and cobalt nitrate was added dropwise to the NaOH solution, and after stirring at room temperature for 30 min, it was transferred to an autoclave for aging for 12 h. The turbid liquid was centrifuged, and the product was washed with anhydrous ethanol and deionized water until neutral, and then freeze-dried for 24 h. Finally, the target 5% Co-CeO2 catalyst was obtained by calcining at 600℃ in air for 5 hours. The TEM image and particle size distribution of the catalyst are shown in Figure 5, and the HAADF image is shown in Figure 6. As shown in Figures 5 and 6, the obtained Co-CeO2 catalyst has a small size and a uniform nanorod structure.

[0117] Ethylene carbonate was prepared by 5% Co-CeO2catalyzed reaction of CO2and ethylene glycol in a 50ml stirred tank reactor with Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMSO was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 1.

[0118] Example 17

[0119] The preparation method of 5% Co-CeO2catalyst was the same as that in Example 16.

[0120] Ethylene carbonate was prepared by 5% Co-CeO2catalyzed reaction of CO2and ethylene glycol in a 50ml stirred tank reactor with Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMSO was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 1.

[0121] Example 18

[0122] The preparation method of 5% Co-CeO2catalyst was the same as that in Example 16.

[0123] Ethylene carbonate was prepared by 5% Co-CeO2catalyzed reaction of CO2and ethylene glycol in a 50ml stirred tank reactor with Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMSO was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 1.

[0124] Example 19

[0125] The preparation method of 5% Co-CeO2catalyst was the same as that in Example 16.

[0126] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent NMP was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0127] Example 20

[0128] The preparation method of the 5% Co-CeO2catalyst was the same as that in Example 16.

[0129] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0130] Example 21

[0131] The preparation method of the 5% Co-CeO2catalyst was the same as that in Example 16.

[0132] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 30mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0133] Example 22

[0134] The preparation method of the 5% Co-CeO2catalyst was the same as that in Example 16.

[0135] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 5mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 30mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0136] Example 23

[0137] 5% Co-CeO2catalyst was prepared as in Example 16.

[0138] Ethylene carbonate was prepared by the reaction of CO2and ethylene glycol catalyzed by 5% Co-CeO2in a 50ml stirred tank reactor with Teflon liner. The amount of ethylene glycol was 15mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 30mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was taken for GC detection, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0139] Example 24

[0140] 5% Co-CeO2catalyst was prepared as in Example 16.

[0141] Ethylene carbonate was prepared by the reaction of CO2and ethylene glycol catalyzed by 5% Co-CeO2in a 50ml stirred tank reactor with Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 5ml, the amount of 2-CP was 30mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was taken for GC detection, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0142] Example 25

[0143] 5% Co-CeO2catalyst was prepared as in Example 16.

[0144] Ethylene carbonate was prepared by the reaction of CO2and ethylene glycol catalyzed by 5% Co-CeO2in a 50ml stirred tank reactor with Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 15ml, the amount of 2-CP was 30mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was taken for GC detection, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0145] Example 26

[0146] 5% Co-CeO2catalyst was prepared as in Example 16.

[0147] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 15mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0148] Example 27

[0149] The preparation method of the 5% Co-CeO2catalyst was the same as that in Example 16.

[0150] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.15g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0151] Example 28

[0152] The preparation method of the 5% Co-CeO2catalyst was the same as that in Example 16.

[0153] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.25g, the reaction pressure was 4Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0154] Example 29

[0155] The preparation method of the 5% Co-CeO2catalyst was the same as that in Example 16.

[0156] Ethylene carbonate was prepared by using 5% Co-CeO2catalyst to catalyze the reaction of CO2and ethylene glycol in a 50ml stirred tank with polytetrafluoroethylene lining. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 3Mpa, the reaction temperature was 140℃, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0157] Example 30

[0158] The 5% Co-CeO2catalyst was prepared according to the method of Example 16.

[0159] Ethylene carbonate was prepared by the reaction of CO2and ethylene glycol catalyzed by 5% Co-CeO2in a 50ml stirred tank reactor with a Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 2Mpa, the reaction temperature was 140°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0160] Example 31

[0161] The 5% Co-CeO2catalyst was prepared according to the method of Example 16.

[0162] Ethylene carbonate was prepared by the reaction of CO2and ethylene glycol catalyzed by 5% Co-CeO2in a 50ml stirred tank reactor with a Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 130°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0163] Example 32

[0164] The 5% Co-CeO2catalyst was prepared according to the method of Example 16.

[0165] Ethylene carbonate was prepared by the reaction of CO2and ethylene glycol catalyzed by 5% Co-CeO2in a 50ml stirred tank reactor with a Teflon liner. The amount of ethylene glycol was 10mmol, the amount of solvent DMF was 10ml, the amount of 2-CP was 20mmol, the amount of catalyst was 0.2g, the reaction pressure was 4Mpa, the reaction temperature was 110°C, the reaction time was 5h, and the stirring speed was 500rpm. The sample was detected by GC, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0166] Example 33

[0167] The 5% Co-CeO2catalyst was prepared according to the method of Example 16.

[0168] Ethylene carbonate was prepared by reacting CO2 and ethylene glycol in a 50 ml stirred tank lined with polytetrafluoroethylene (PTFE) using a 5% Co-CeO2 catalyst. The amount of ethylene glycol was 10 mmol, the amount of DMF solvent was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 MPa, the reaction temperature was 140 °C, the reaction time was 2 h, and the stirring speed was 500 rpm. Samples were taken for GC analysis, and the reaction results, based on the ratio of reactants to products, are shown in Table 2.

[0169] Example 34

[0170] The preparation method of the 5% Co-CeO2 catalyst is the same as in Example 16.

[0171] Ethylene carbonate was prepared by reacting CO2 and ethylene glycol in a 50 ml stirred tank lined with polytetrafluoroethylene (PTFE) using a 5% Co-CeO2 catalyst. The amount of ethylene glycol was 10 mmol, the amount of DMF solvent was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 MPa, the reaction temperature was 140 °C, the reaction time was 0.5 h, and the stirring speed was 500 rpm. Samples were taken for GC analysis, and the reaction results, based on the ratio of reactants to products, are shown in Table 2.

[0172] Comparative Example 6

[0173] 4.3 g of cobalt(II) nitrate hexahydrate and cerium(III) nitrate hexahydrate (cobalt:cerium atomic molar ratio of 0.03:1) were dissolved in 25 mL of deionized water, while 48 g of NaOH was dissolved in 175 mL of deionized water. The cerium nitrate and cobalt nitrate mixed solution was added dropwise to the NaOH solution, stirred at room temperature for 30 min, and then transferred to a hydrothermal reactor for aging for 12 h. The turbid liquid was separated by centrifugation, and the product was washed with anhydrous ethanol and deionized water until neutral, and then freeze-dried for 24 h. Finally, it was calcined in air at 600 °C for 5 h to obtain the target 3% Co-CeO2 catalyst.

[0174] Ethylene carbonate was prepared by reacting CO2 and ethylene glycol in a 50 ml stirred tank lined with polytetrafluoroethylene (PTFE) using a 3% Co-CeO2 catalyst. The amount of ethylene glycol was 10 mmol, the amount of DMF solvent was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 MPa, the reaction temperature was 140 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. Samples were taken for GC analysis, and the reaction results, based on the ratio of reactants to products, are shown in Table 2.

[0175] Comparative Example 7

[0176] Cobalt(II) nitrate hexahydrate and cerium(III) nitrate hexahydrate (4.3 g) with cobalt to cerium atomic molar ratio of 0.1:1 were dissolved in 25 ml of deionized water, while 48 g of NaOH was dissolved in 175 ml of deionized water. The mixed solution of cerium nitrate and cobalt nitrate was added dropwise into the NaOH solution, which was stirred at room temperature for 30 min and then transferred into an autoclave for aging for 12 h. The turbid solution was centrifugally separated, and the product was washed with anhydrous ethanol and deionized water until neutral, and then freeze-dried for 24 h. Finally, the target 10% Co-CeO2catalyst was obtained by calcination in air at 600 °C for 5 h.

[0177] Ethylene carbonate was prepared by using 10% Co-CeO2to catalyze the reaction of CO2and ethylene glycol in a 50 ml stirred tank with a polytetrafluoroethylene lining. The amount of ethylene glycol was 10 mmol, the amount of solvent DMF was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 Mpa, the reaction temperature was 140 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. Sampling was performed for GC detection, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0178] Comparative Example 8

[0179] Aluminum(III) nitrate nonahydrate and cerium(III) nitrate hexahydrate (4.3 g) with aluminum to cerium atomic molar ratio of 0.05:1 were dissolved in 25 ml of deionized water, while 48 g of NaOH was dissolved in 175 ml of deionized water. The mixed solution of cerium nitrate and aluminum nitrate was added dropwise into the NaOH solution, which was stirred at room temperature for 30 min and then transferred into an autoclave for aging for 12 h. The turbid solution was centrifugally separated, and the product was washed with anhydrous ethanol and deionized water until neutral, and then freeze-dried for 24 h. Finally, the target 5% Al-CeO2catalyst was obtained by calcination in air at 600 °C for 5 h.

[0180] Ethylene carbonate was prepared by using 5% Al-CeO2to catalyze the reaction of CO2and ethylene glycol in a 50 ml stirred tank with a polytetrafluoroethylene lining. The amount of ethylene glycol was 10 mmol, the amount of solvent DMF was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 Mpa, the reaction temperature was 140 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. Sampling was performed for GC detection, and the reaction results were obtained according to the proportion of raw materials and products, as shown in Table 2.

[0181] Comparative Example 9

[0182] Copper and cerium atomic molar ratio of 0.05:1 copper (II) nitrate trihydrate and cerium (III) nitrate hexahydrate (4.3 g) were dissolved in 25 ml of deionized water, while 48 g of NaOH was dissolved in 175 ml of deionized water. The mixed solution of cerium nitrate and copper nitrate was added dropwise into the NaOH solution, and after stirring at room temperature for 30 min, it was transferred into an autoclave for aging for 12 h. The turbid liquid was centrifuged, and the product was washed with anhydrous ethanol and deionized water until neutral, and freeze-dried for 24 h. Finally, the target 5% Cu-CeO2catalyst was obtained by calcination in air at 600 °C for 5 h.

[0183] In a 50 ml stirred tank reactor with a polytetrafluoroethylene lining, 5% Cu-CeO2catalyzed the reaction of CO2and ethylene glycol to produce ethylene carbonate. The amount of ethylene glycol was 10 mmol, the amount of solvent DMF was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 Mpa, the reaction temperature was 140 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. Sampling was performed for GC detection, and according to the proportion of raw materials and products, the reaction results are shown in Table 2.

[0184] Comparative Example 10

[0185] The preparation method of 5% Co-CeO2catalyst was the same as that of Example 16.

[0186] In a 50 ml stirred tank reactor with a polytetrafluoroethylene lining, 5% Co-CeO2catalyzed the reaction of CO2and 1,3-propanediol to produce propylene carbonate. The amount of 1,3-propanediol was 10 mmol, the amount of solvent DMF was 10 ml, the amount of 2-CP was 20 mmol, the amount of catalyst was 0.2 g, the reaction pressure was 4 Mpa, the reaction temperature was 140 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. Sampling was performed for GC detection, and according to the proportion of raw materials and products, the reaction results are shown in Table 2.

[0187] Comparative Example 11

[0188] The preparation method of 5% Co-CeO2catalyst was the same as that of Example 16.

[0189] In a 50 ml stirred tank reactor with a polytetrafluoroethylene lining, 5% Co-CeO2catalyzed the reaction of CO2and glycerol to produce glycerol carbonate. The amount of glycerol was 10 mmol, the amount of solvent DMF was 10 ml, the amount of 2-CP was 30 mmol, the amount of catalyst was 0.34 g, the reaction pressure was 4 Mpa, the reaction temperature was 140 °C, the reaction time was 5 h, and the stirring speed was 500 rpm. Sampling was performed for GC detection, and according to the proportion of raw materials and products, the results are shown in Table 2.

[0190] Comparative Example 12

[0191] 5% Co-CeO2catalyst preparation method is same as example 16.

[0192] In 50ml stirred tank, 5% Co-CeO2catalyze the reaction of CO2and ethylene glycol to prepare ethylene carbonate. Ethylene glycol amount is 12g, 2-CP dosage is 15g, catalyst dosage is 0.2g, reaction pressure is 2Mpa, reaction temperature is 130℃, reaction time is 6h, stirring speed is 500rpm. Sampling for GC detection, according to the proportion of raw materials and products, the reaction results are shown in table 2.

[0193] Performance comparison

[0194] Table 2: reaction results of examples 16-34, comparative examples 6-12

[0195] From the results of table 2, with 5% Co-CeO2as catalyst, 2-CP as dehydrating agent, under the solvent effect of DMF, catalyze the reaction of ethylene glycol and carbon dioxide to directly synthesize EC, high yield of EC can be obtained, and little by-product is produced. In addition, this scheme is also suitable for the reaction of other polyols and carbon dioxide. It is proved that the present application is a high efficient scheme for synthesizing cyclic carbonate, and is expected to be popularized to industrial application.

[0196] The raw materials and equipment used in the present application are all common raw materials and equipment in the art if not otherwise specified; the methods used in the present application are all conventional methods in the art if not otherwise specified.

[0197] The above is only the preferred embodiment of the present application, and does not limit the present application in any way, any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.

Claims

1. A method for producing a carbonate compound, characterized by comprising: The cobalt-doped nanorod ceria catalyst is prepared by the following steps: ​ The trivalent cerium salt and / or its hydrate and the divalent cobalt salt and / or its hydrate are dissolved in water to obtain a cobalt-cerium mixed solution; the cerium-cobalt mixed solution is added dropwise into a NaOH solution under stirring, and then the obtained mixed solution is stirred in a sealed state; the obtained mixture is subjected to hydrothermal aging, centrifugal separation, filtration to collect the solid product, and washing, drying and calcination to obtain the cobalt-doped nanorod ceria catalyst. The molar ratio of the trivalent cerium salt and / or its hydrate to the divalent cobalt salt and / or its hydrate is 0.01-0.20:1 in terms of the molar amount of cobalt atoms and cerium atoms.

2. The preparation method according to claim 1, wherein The trivalent cerium salt and / or its hydrate is cerium nitrate hexahydrate, and the divalent cobalt salt and / or its hydrate is cobalt nitrate hexahydrate. The molar ratio of the trivalent cerium salt and / or its hydrate to the divalent cobalt salt and / or its hydrate is 0.03-0.1:1 in terms of the molar amount of cobalt atoms and cerium atoms.

3. The production method according to claim 2, characterized by, The amount ratio of the cerium nitrate hexahydrate to water is 3-5 g:20-40 mL. The amount ratio of NaOH to water in the NaOH solution is 45-55 g:150-250 mL.

4. The preparation method according to claim 1, wherein The stirring time of the mixed solution is 20-40 min, and the stirring temperature is 20-40℃. The hydrothermal aging time is 8-15 h. The centrifugal separation speed is 8000-10000 rpm. The drying is freeze drying, and the time is 20-25 h. The calcination temperature is 500-700℃, and the time is 3-10 h. The calcination atmosphere is air, hydrogen or nitrogen.

5. A method for producing dimethyl carbonate, characterized by, The preparation method comprises the following steps: CO2 and methanol are used as raw materials, the cobalt-doped nanorod ceria catalyst prepared by the preparation method of any one of claims 1-4 is used as a catalyst, 2-cyanopyridine is used as a dehydrating agent, and dimethyl carbonate is obtained after reaction.

6. The preparation method according to claim 5, wherein The mass ratio of the methanol, 2-cyanopyridine and the cobalt-doped nanorod ceria catalyst is 8-20:8-20:0.1-0.

5. The reaction pressure is 1-4 MPa, the reaction temperature is 100-160℃, and the reaction time is 1-8 h.

7. A method for producing ethylene carbonate, characterized by, The preparation method comprises the following steps: CO2 and ethylene glycol are used as raw materials, the cobalt-doped nanorod ceria catalyst prepared by the preparation method of any one of claims 1-4 is used as a catalyst, 2-cyanopyridine is used as a dehydrating agent, and ethylene carbonate is prepared by cyclization and dehydration reaction in a solvent; Meanwhile, the hydration reaction of the dehydrating agent 2-cyanopyridine is coupled, and 2-cyanopyridine is hydrated to generate 2-pyridinecarboxamide.

8. The preparation method according to claim 7, wherein The molar ratio of the ethylene glycol to 2-cyanopyridine is 1:1.5-3. The amount ratio of the ethylene glycol to the solvent is 1-3 mmol:1-4 mL. The amount ratio of the catalyst to the ethylene glycol is 1-3 g:50-150 mmol. The solvent is one of tetrahydrofuran, N, N-dimethylformamide, N-methyl pyrrolidone and dimethyl sulfoxide.

9. The preparation method according to claim 7, characterized in that, The reaction pressure of the cyclization dehydration reaction is 1-4 MPa, the reaction temperature is 100-160℃, the reaction time is 0.5-5 h, and the reaction is carried out at a stirring speed of 400-800 rpm.

10. The preparation method according to claim 7, characterized in that, Further comprising the following steps: 2-pyridine carboxamide is separated from the product and further recycled by a dehydration reaction to produce 2-cyanopyridine.

Images