Synthesis method of cyclic carbonate

Abstract

The present invention provides a cyclic carbonate synthesis method, and belongs to the technical field of organic ester compound synthesis, and the cyclic carbonate synthesis method comprises the following steps: S1, 1, 3-propylene glycol, a dehydrating agent and a catalyst are added into a high pressure reaction kettle, and CO2 is introduced into the high pressure reaction kettle for a reaction; s2, after the reaction is finished, after the high-pressure reaction kettle is cooled to the room temperature, redundant gas in the high-pressure reaction kettle is discharged, after the gas in the high-pressure reaction kettle is completely discharged, the high-pressure reaction kettle is opened, the catalyst is filtered out, and the solution is subjected to vacuum-pumping separation to obtain a target product; the catalyst is a heterogeneous catalyst MO (at) Complex (Co). Carbon dioxide conversion is carried out in a chemical utilization mode, a chemical product trimethylene carbonate can be produced, the synthesis route is easy to operate, and after the MO-Complex (Co) catalyst is added, the yield is high, the high additional value is achieved, and the green chemistry concept is met.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of organic ester compounds, in particular to a method for synthesizing cyclic carbonate. Background Art

[0002] Climate change is one of the most serious challenges facing mankind. Carbon dioxide is the main factor causing global climate change. As a greenhouse gas emitted by human activities, most of carbon dioxide comes from various industrial processes and the burning of fossil fuels. Carbon dioxide is a cheap, non-toxic, non-flammable and abundant carbon source. Therefore, converting carbon dioxide into more valuable chemicals such as urea, methanol, cyclic carbonates, hydrocarbon compounds, etc. can not only achieve efficient utilization of carbon dioxide but also reduce its impact on the environment to a certain extent. Therefore, developing new routes for the synthesis of chemical products based on the utilization of carbon dioxide is a good strategy to kill two birds with one stone.

[0003] Cyclic carbonates are an important class of compounds, which are widely used as starting materials for polycarbonate resins, electrolytes for lithium batteries, inert solvents, alkyl and carbonyl reagents, etc. Among cyclic carbonates, trimethylene carbonate is an important one. Trimethylene carbonate is the monomer of polytrimethylene carbonate, which is a class of non-toxic, biocompatible, biodegradable biomedical materials. At the same time, because it has certain elasticity and good mechanical processing properties at human body temperature, it has been widely used in biomedical fields such as degradable ligature devices, drug controlled release, and in vivo implant materials.

[0004] The synthesis of TMC (Trimethylcarbonate) mainly includes phosgene method, ester exchange method, propylene glycol-urea method and carbon dioxide-epoxide method. From the perspective of green chemistry, the synthesis route with simple operation, mild reaction conditions and high selectivity is better. The synthesis of trimethylene carbonate using CO2 as raw material is a synthesis route that is more in line with the concept of green chemistry. However, due to the low reaction activity of CO2, large-scale synthetic application cannot be achieved. For this reason, the present invention provides a method for synthesizing cyclic carbonate. Summary of the invention

[0005] In order to solve the problem that in the synthesis route of trimethylene carbonate using CO2 as a raw material, large-scale synthesis and application cannot be achieved due to the low reaction activity of CO2, the present invention provides a method for synthesizing cyclic carbonate.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for synthesizing a cyclic carbonate comprises the following steps:

[0008] S1, adding 1,3-propylene glycol, a dehydrating agent and a catalyst into a high-pressure reactor, and introducing CO2 into the high-pressure reactor for reaction;

[0009] S2. After the reaction is completed, wait for the autoclave to cool to room temperature and discharge the excess gas in the autoclave. After all the gas in the autoclave is discharged, open the autoclave, filter to remove the catalyst, and vacuumize the solution to remove the dehydrating agent to obtain the target product.

[0010] The catalyst is a heterogeneous catalyst MO@Complex(Co), wherein MO represents a metal oxide.

[0011] As a further description of the above technical solution:

[0012] MO in the MO@Complex (Co) is one of MgO, CuO, NiO, Fe2O3, ZnO, MnO2, Sm2O3, and In2O3;

[0013] The Complex(Co) in the MO@Complex(Co) is a metallic crystalline material [Co(Htpim)2(OH)Cl·7H2O] synthesized from CoCl2·6H2O and 2,4,5-tri(4-pyridine)-1H-imidazole.

[0014] As a further description of the above technical solution:

[0015] The dehydrating agent is one of 2-cyanopyridine, 3-cyanopyridine, 2-cyanofuran, 2-cyanothiophene, 2-cyanopyrimidine, isopropanol, n-butanol, tert-butanol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0016] As a further description of the above technical solution:

[0017] In the step S1, the pressure in the autoclave is controlled to be 1-5 MPa and the temperature is controlled to be 60-120° C., and the reaction is carried out for 2-8 hours under stirring conditions.

[0018] As a further description of the above technical solution:

[0019] The preparation of the MO@Complex (Co) comprises the following steps:

[0020] Complex (Co) and metal nitrate are dispersed in a solvent, stirred at room temperature for 30 to 90 minutes, and citric acid is added thereto and stirred evenly, and then PEG is added and stirred for 30 to 60 minutes to form a sol. The obtained sol is dried at 100 to 120°C, transferred to a tubular furnace and heated to 300 to 500°C at a heating rate of 5°C / min, and kept at a constant temperature for 8 to 12 hours, and then taken out and cooled to room temperature to obtain the catalyst MO@Complex (Co).

[0021] As a further description of the above technical solution:

[0022] The metal nitrate is any one of Mg(NO3)2·6H2O, Cu(NO3)2, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O, Mn(NO3)2·4H2O, Sm(NO3)3·6H2O, and In(NO3)3.

[0023] As a further description of the above technical solution:

[0024] The preparation method of the Complex (Co) comprises:

[0025] The ligand Htpim and CoCl2·6H2O were dissolved in a mixed solvent, ultrasonically mixed for 30 minutes, the pH was adjusted to 5-7, ultrasonication was continued for 20 minutes, and the mixture was heated at 100-120°C for 12-24 hours. The obtained mixture was allowed to stand at room temperature for 10-12 hours, filtered, and the solid product was washed with anhydrous ethanol, and dried at 60-80°C to obtain Complex (Co).

[0026] As a further description of the above technical solution:

[0027] The mixed solvent is any combination of N,N-dimethylacetamide (DMA) and water, N,N-dimethylformamide (DMF) and water, DMA and ethanol, DMF and ethanol, DMA and methanol, DMF and methanol, DMF and acetonitrile, DMA and acetonitrile, DMA and ethylene glycol, DMF and ethylene glycol, DMA and isopropanol, DMF and isopropanol, ethanol and water, methanol and water, acetonitrile and water, ethylene glycol and water, and isopropanol and water.

[0028] Beneficial effects of the present invention:

[0029] 1. The present invention converts carbon dioxide in a chemical utilization manner to produce a chemical product, trimethylene carbonate. The synthesis route is easy to operate, and the yield is high after adding the MO@Complex (Co) catalyst. It has high added value and is in line with the concept of green chemistry.

[0030] 2. The MO@Complex (Co) catalyst provided by the present invention has good catalytic reusability when used for cyclic carbonate synthesis reaction, can be reused more than 5 times, has high catalytic activity and high reaction conversion rate.

[0031] 3. In the catalyst MO@Complex(Co), the metal oxide MO has good dispersion, large specific surface area, and many catalytic sites. It is tightly connected with Complex(Co) through intermolecular interactions, and the electron transfer between the Co metal site and MO improves its catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate a method for synthesizing a cyclic carbonate, the following drawings are shown;

[0033] Figure 1 Schematic diagram of the crystal structure of Complex (Co) in the present invention. DETAILED DESCRIPTION

[0034] Example 1

[0035] The present application provides an embodiment of the present invention also provides a method for synthesizing trimethylene cyclic carbonate:

[0036] The synthesis method of trimethylene cyclic carbonate mainly comprises the following steps: adding MO@Complex (Co) catalyst, 1,3-propylene glycol and dehydrating agent to a 100 mL high-pressure stainless steel reactor in sequence, and then introducing CO2 into the high-pressure stainless steel reactor, the pressure in the high-pressure stainless steel reactor is 1-5 MPa, the reaction temperature is 60-120° C., and the preferred reaction temperature is 80-90° C. The reaction time is 2-8 hours, preferably 4-5 hours.

[0037] After the reaction is completed, wait for the autoclave to cool to room temperature and discharge excess gas in the autoclave. After all the gas in the autoclave is discharged, open the autoclave, filter to remove the catalyst, and vacuum separate the solution to obtain the target product.

[0038] The reaction route is as follows:

[0039]

[0040] Example 2

[0041] This embodiment provides a method for preparing Complex (Co), which specifically includes:

[0042] 10 mg of ligand Htpim and 47.5 mg of CoCl2·6H2O were dissolved in 2 mL of DMA and 2 mL of H2O, and ultrasonically mixed for 30 min. The pH was adjusted to 5, and ultrasonication was continued for 20 min. The mixture was heated at 100°C for 24 h. The mixture was allowed to stand at room temperature for 10 h. The solid product was filtered and washed with anhydrous ethanol, and dried at 60°C to obtain Complex (Co) with a yield of 84%. Its crystal structure is shown in Figure 1 as shown in .

[0043] Example 3

[0044] The catalyst MgO@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0045] Specifically, 0.2 mmol Complex(Co) and 0.2 mmol Mg(NO3)2·6H2O were dispersed in 40 mL H2O, stirred at room temperature for 30 min, 0.4 mmol citric acid was added thereto and stirred evenly, and then 0.2 g PEG was added and stirred for 30 to 60 min to form a sol. The obtained sol was dried at 120°C, transferred into a tubular furnace and heated to 500°C at a heating rate of 5°C / min, and kept at a constant temperature for 12 h, taken out and cooled to room temperature to obtain the catalyst MgO@Complex(Co).

[0046] Example 4

[0047] The catalyst CuO@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0048] Specifically: 0.2mmol Complex(Co) and 0.2mmol Cu(NO3)2 were dispersed in 40mLH2O, stirred at room temperature for 30min, 0.4mmol citric acid was added thereto and stirred evenly, and then 0.2g PEG was added and stirred for 30min to form a sol. The obtained sol was dried at 100°C, transferred into a tubular furnace and heated to 350°C at a heating rate of 5°C / min, and kept at a constant temperature for 8h, taken out and cooled to room temperature to obtain the catalyst CuO@Complex(Co).

[0049] Example 5

[0050] The catalyst NiO@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0051] Specifically: 0.2mmol Complex(Co) and 0.2mmol Ni(NO3)2·6H2O were dispersed in 40mL EtOH and stirred at room temperature for 60min. 0.4mmol citric acid was added thereto and stirred evenly. Then 0.2g PEG was added and stirred for 30min to form a sol. The obtained sol was dried at 120°C, transferred into a tubular furnace and heated to 300°C at a heating rate of 5°C / min, and kept at a constant temperature for 12h. Then, it was taken out and cooled to room temperature to obtain the catalyst NiO@Complex(Co).

[0052] Example 6

[0053] The catalyst Fe2O3@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0054] Specifically, 0.2mmol Complex(Co) and 0.2mmol Fe(NO3)3·9H2O were dispersed in 40mL H2O and stirred at room temperature for 30min. 0.4mmol citric acid was added thereto and stirred evenly. Then 0.2g PEG was added and stirred for 60min to form a sol. The obtained sol was dried at 120°C, transferred into a tubular furnace and heated to 350°C at a heating rate of 5°C / min, and kept at a constant temperature for 8h. The catalyst Fe2O3@Complex(Co) was obtained after being taken out and cooled to room temperature.

[0055] Example 7

[0056] The catalyst ZnO@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0057] Specifically, 0.2mmol Complex(Co) and 0.2mmol Zn(NO3)2·6H2O were dispersed in 40mLH2O, stirred at room temperature for 30min, 0.4mmol citric acid was added thereto and stirred evenly, and then 0.2g PEG was added and stirred for 60min to form a sol. The obtained sol was dried at 120°C, transferred into a tubular furnace and heated to 300°C at a heating rate of 5°C / min, and kept at a constant temperature for 12h, taken out and cooled to room temperature to obtain the catalyst ZnO@Complex(Co).

[0058] Example 8

[0059] The catalyst MnO2@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0060] Specifically, 0.2mmol Complex(Co) and 0.2mmol Mn(NO3)2·4H2O were dispersed in 40mLH2O, stirred at room temperature for 30min, 0.4mmol citric acid was added thereto and stirred evenly, and then 0.2g PEG was added and stirred for 80min to form a sol. The obtained sol was dried at 100°C, transferred into a tubular furnace and heated to 400°C at a heating rate of 5°C / min, and kept at a constant temperature for 18h, taken out and cooled to room temperature to obtain the catalyst MnO2@Complex(Co).

[0061] Example 9

[0062] The catalyst Sm2O3@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0063] Specifically, 0.2mmol Complex(Co) and 0.2mmol Sm(NO3)3·6H2O were dispersed in 40mLH2O, stirred at room temperature for 30min, 0.4mmol citric acid was added thereto and stirred evenly, and then 0.2g PEG was added and stirred for 30min to form a sol. The obtained sol was dried at 110°C, transferred into a tubular furnace and heated to 350°C at a heating rate of 5°C / min, and kept at a constant temperature for 12h, taken out and cooled to room temperature to obtain the catalyst Sm2O3@Complex(Co).

[0064] Example 10

[0065] The catalyst In2O3@Complex(Co) was prepared based on the crystalline Complex(Co) in Example 2.

[0066] Specifically: 0.2mmol Complex(Co) and 0.2mmol In(NO3)3 were dispersed in 40mLH2O, stirred at room temperature for 30min, 0.4mmol citric acid was added thereto and stirred evenly, and then 0.2g PEG was added and stirred for 60min to form a sol, the obtained sol was dried at 120°C, transferred into a tubular furnace and heated to 500°C at a heating rate of 5°C / min, and kept at a constant temperature for 8 to 12h, taken out and cooled to room temperature to obtain the catalyst In2O3@Complex(Co).

[0067] Embodiment 11

[0068] A method for synthesizing trimethylene cyclic carbonate: 0.04 g Sm2O3@Complex (Co) catalyst, 10 mmol (0.76 g) 1,3-propylene glycol and 30 mL dehydrating agent are sequentially added into a 100 mL high-pressure stainless steel reactor. The air in the reactor is replaced with CO2 three times after the reactor is sealed, a certain pressure of CO2 is filled into the reactor at room temperature, and the reaction is carried out at a certain temperature for a certain time. After the reaction is completed, the reactor is cooled to room temperature and the excess gas in the reactor is discharged. The reactor can be opened only after all the gas in the reactor is discharged, the catalyst is filtered out, and the solution is vacuum-separated to obtain the target product.

[0069] According to the above method, the dehydrating agent, reaction temperature, reaction time and reaction pressure were adjusted to obtain the trimethylene carbonate yield Table 1 as follows:

[0070]

[0071]

[0072] Table 1

[0073] The NMR data of trimethylene carbonate are as follows: 1HNMR (400 MHz, CDCl3) δ (ppm): 4.24 (t, J = 6.0 Hz, 4H), 2.08-2.02 (m, 2H).

[0074] It can be seen from Table 1 that when Sm2O3@Complex(Co) is used as a catalyst, 2-cyanopyridine is used as a dehydrating agent, the reaction temperature is 80°C, the reaction time is 4h, and the reaction pressure is 2 or 3MPa, the yield is the highest. Under the above conditions, the reaction pressure of 1-5MPa has little effect on the yield, and the reaction pressure can be selected to be 1MPa. The reaction temperature has the greatest impact, and the reaction temperature should be controlled at around 80°C.

[0075] Embodiment 26

[0076] Synthesis of trimethylene carbonate catalyzed by MgO@Complex(Co)

[0077] 0.04g MgO@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After sealing the reactor, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled in at room temperature. The temperature was raised to 80°C for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened only after all the gas in the reactor was discharged. The catalyst was filtered out and the solution was separated by vacuum to obtain the target product with a yield of 70%.

[0078] Embodiment 27

[0079] Synthesis of trimethylene carbonate catalyzed by CuO@Complex(Co)

[0080] 0.04g CuO@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After the reactor was sealed, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened only after all the gas in the reactor was discharged. The catalyst was filtered out and the solution was vacuum separated to obtain the target product with a yield of 57%.

[0081] Embodiment 28

[0082] Synthesis of trimethylene carbonate catalyzed by NiO@Complex(Co)

[0083] 0.04g NiO@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After sealing the reactor, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened after all the gas in the reactor was discharged, the catalyst was filtered out, and the solution was vacuum-separated to obtain the target product with a yield of 74%.

[0084] Embodiment 29

[0085] Synthesis of trimethylene carbonate catalyzed by Fe2O3@Complex(Co)

[0086] 0.04g Fe2O3@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After the reactor was sealed, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened only after all the gas in the reactor was discharged. The catalyst was filtered out and the solution was vacuum separated to obtain the target product with a yield of 63%.

[0087] Embodiment 30

[0088] Synthesis of trimethylene carbonate catalyzed by ZnO@Complex(Co)

[0089] 0.04g ZnO@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After sealing the reactor, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened after all the gas in the reactor was discharged, the catalyst was filtered out, and the solution was vacuum-separated to obtain the target product with a yield of 70%.

[0090] Embodiment 31

[0091] Synthesis of trimethylene carbonate catalyzed by MnO2@Complex(Co)

[0092] 0.04g MnO2@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After the reactor was sealed, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened only after all the gas in the reactor was discharged. The catalyst was filtered out and the solution was vacuum separated to obtain the target product with a yield of 75%.

[0093] Embodiment 32

[0094] Synthesis of trimethylene carbonate catalyzed by In2O3@Complex(Co)

[0095] 0.04g In2O3@Complex(Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After the reactor was sealed, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened only after all the gas in the reactor was discharged. The catalyst was filtered out and the solution was vacuum separated to obtain the target product with a yield of 66%.

[0096] Embodiments 33 to 37

[0097] Verification of the reusability of Sm2O3@Complex(Co) catalyst

[0098] The multiphase catalyst separated in Example 16 can be reused after washing with ether and drying. The catalytic yields of the five times are 88%, 86%, 86%, 87% and 85% respectively.

[0099] Comparative Example 1

[0100] Synthesis of trimethylene carbonate without catalyst

[0101] Add 10 mmol (0.76 g) of 1,3-propylene glycol and 30 mL of 2-cyanopyridine to a 100 mL high-pressure stainless steel reactor. After sealing the reactor, replace the air in the reactor with CO2 three times, fill it with a certain pressure of CO2 at room temperature, heat it to 80 ° C for 4 hours, monitor the pressure during the heating process, and ensure that the pressure in the reactor is 1 MPa during the reaction. After the reaction is completed, wait for the reactor to cool to room temperature and exhaust the excess gas in the reactor. The reactor can be opened only after all the gas in the reactor is exhausted, and the catalyst is filtered out. The solution is vacuum-separated to obtain the target product with a yield of 15%.

[0102] Comparative Example 2

[0103] Synthesis of trimethylene carbonate using Complex(Co) catalyst

[0104] 0.04g Complex (Co), 10mmol (0.76g) 1,3-propylene glycol and 30mL 2-cyanopyridine were added to a 100mL high-pressure stainless steel reactor. After sealing the reactor, the air in the reactor was replaced with CO2 three times, and a certain pressure of CO2 was filled at room temperature. The temperature was raised to 80℃ for 4h. The pressure was monitored during the heating process to ensure that the pressure in the reactor was 1MPa during the reaction. After the reaction was completed, the reactor was cooled to room temperature and the excess gas in the reactor was discharged. The reactor could be opened only after all the gas in the reactor was discharged, the catalyst was filtered out, and the solution was vacuum-separated to obtain the target product with a yield of 45%.

[0105] The above examples and comparative examples show that the use of the composite material MO@Complex (Co) of the present invention as a catalyst to prepare trimethylene carbonate can produce high value-added polymerization monomers. The multiphase catalyst is easy to recover and reuse, has high catalytic activity, a simple synthesis reaction process, a high product yield, and a simple and easy-to-operate reaction process, which provides ideas and motivation for the chemical utilization of carbon dioxide.

[0106] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the disclosure of the invention herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0107] It should be understood that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for synthesizing a cyclic carbonate, characterized in that: The following steps are involved: S1, adding 1,3-propylene glycol, a dehydrating agent and a catalyst into a high-pressure reactor, and introducing CO2 into the high-pressure reactor for reaction; S2. After the reaction is completed, wait for the autoclave to cool to room temperature and discharge the excess gas in the autoclave. After all the gas in the autoclave is discharged, open the autoclave, filter to remove the catalyst, and vacuum separate the solution to obtain the target product. The catalyst is a heterogeneous catalyst MO@Complex(Co), wherein MO represents a metal oxide.

2. The method for synthesizing a cyclic carbonate according to claim 1, characterized in that: MO in the MO@Complex (Co) is one of MgO, CuO, NiO, Fe2O3, ZnO, MnO2, Sm2O3, and In2O3; The Complex(Co) in the MO@Complex(Co) is a metallic crystalline material [Co(Htpim)2(OH)Cl·7H2O] synthesized from CoCl2·6H2O and 2,4,5-tri(4-pyridine)-1H-imidazole.

3. The method for synthesizing a cyclic carbonate according to claim 1, characterized in that: The dehydrating agent is one of 2-cyanopyridine, 3-cyanopyridine, 2-cyanofuran, 2-cyanothiophene, 2-cyanopyrimidine, isopropanol, n-butanol, tert-butanol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

4. The method for synthesizing a cyclic carbonate according to claim 1, characterized in that: In the step S1, the pressure in the autoclave is controlled to be 1-5 MPa and the temperature is controlled to be 60-120° C., and the reaction is carried out for 2-8 hours under stirring conditions.

5. The method for synthesizing a cyclic carbonate according to claim 1, characterized in that: The preparation of MO@Complex(Co) includes the following steps: Complex (Co) and metal nitrate are dispersed in a solvent, stirred at room temperature for 30 to 90 minutes, and citric acid is added thereto and stirred evenly, and then PEG is added and stirred for 30 to 60 minutes to form a sol. The obtained sol is dried at 100 to 120°C, transferred to a tubular furnace and heated to 300 to 500°C at a heating rate of 5°C / min, and kept at a constant temperature for 8 to 12 hours, and then taken out and cooled to room temperature to obtain the catalyst MO@Complex (Co).

6. The method for synthesizing a cyclic carbonate according to claim 5, characterized in that: The metal nitrate is any one of Mg(NO3)2·6H2O, Cu(NO3)2, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O, Mn(NO3)2·4H2O, Sm(NO3)3·6H2O, and In(NO3)3.

7. The method for synthesizing a cyclic carbonate according to claim 5, characterized in that: The preparation method of the Complex (Co) comprises: The ligand Htpim and CoCl2·6H2O were dissolved in a mixed solvent, ultrasonically mixed for 30 minutes, the pH was adjusted to 5-7, ultrasonication was continued for 20 minutes, and the mixture was heated at 100-120°C for 12-24 hours. The obtained mixture was allowed to stand at room temperature for 10-12 hours, filtered, and the solid product was washed with anhydrous ethanol, and dried at 60-80°C to obtain Complex (Co).

8. The method for synthesizing a cyclic carbonate according to claim 7, characterized in that: The mixed solvent is any combination of N,N-dimethylacetamide (DMA) and water, N,N-dimethylformamide (DMF) and water, DMA and ethanol, DMF and ethanol, DMA and methanol, DMF and methanol, DMF and acetonitrile, DMA and acetonitrile, DMA and ethylene glycol, DMF and ethylene glycol, DMA and isopropanol, DMF and isopropanol, ethanol and water, methanol and water, acetonitrile and water, ethylene glycol and water, and isopropanol and water.

Images