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 MxOy (at) Zn-dpot. 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 MxOy at Zn-dpot 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] Carbon dioxide (CO2) emissions are the main factor causing global warming. Carbon capture, utilization and storage are key technologies for addressing global climate change. In recent years, countries around the world have stepped up their research and development efforts to achieve large-scale industrial CO2 emission reduction. At the same time, CO2 is also a cheap, non-toxic and abundant carbon resource that can be converted into high-value-added chemical products such as urea, methanol, acetic acid, cyclic carbonates, etc. 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. However, due to its high thermodynamic stability, CO2 must react with high-energy starting materials to be converted into low-energy target compounds. At the same time, the catalytic reaction system can significantly reduce the energy of the reaction and promote the smooth progress of the reaction. Therefore, it is necessary to use a catalyst in the CO2 cycloaddition reaction.

[0003] Cyclic carbonate compounds are an important class of chemical raw materials, which can be directly used to prepare electrolytes, form polymer materials through ring-opening polymerization, etc. Among them, trimethylene carbonate (TMC) is an important polymerization monomer, which is mainly used to synthesize polytrimethylene carbonate (PTMC) biodegradable medical materials. PTMC materials are non-toxic, have certain elasticity and good mechanical processing properties at body temperature, and have been widely used in the fields of degradable ligature devices, controlled drug release, and in vivo implant materials (bone fixation, tissue engineering scaffolds). Compared with other carbonates, TMC has no by-products in the ring-opening polymerization process, low thermal effect, fast polymerization speed, and can reach a very high molecular weight in a short time. At the same time, it will not decarbonize, making it an ideal monomer for synthesizing high molecular weight polycarbonate.

[0004] From the perspective of green chemistry, a synthetic route with simple operation, mild reaction conditions and high selectivity is more excellent. The synthesis of trimethylene carbonate by cyclization of CO2 and 1,3-propanol is a synthetic route that is more in line with the concept of green chemistry. However, due to the low reactivity of CO2, a highly active catalyst is required to achieve large-scale synthetic applications. Therefore, it is of great significance to obtain a catalyst with good catalytic performance. For this purpose, the present invention provides a method for synthesizing cyclic carbonates. 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 vacuum separate the solution to obtain the target product.

[0010] The catalyst is a heterogeneous catalyst M x O y @Zn-dpot.

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

[0012] The M x O y @M in Zn-dpot x O y It represents one of V2O5, CeO2, PdO, MgO, CuO, Fe2O3, MnO2, and Nb2O5;

[0013] The M x O y @Zn-dpot in Zn-dpot represents the metal organic framework material synthesized from Zn(NO3)26H2O and 5,5',5"-((1,3,5-triazine-2,4,6-triyl)trioxy)triisophthalic acid [Zn7(dpot)2(H2O) 11 ]2OH 3H2O 5DMA.

[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 MxOy@Zn-dpot comprises the following steps:

[0020] Step 1: Place Zn(NO3)26H2O and H6dpot in a Pyrex vial, add a certain amount of mixed solvent, dissolve under ultrasonication at room temperature for 30 to 60 minutes to obtain a colorless transparent solution, then store the colorless transparent solution in an oven at 80 to 120°C for 24 to 36 hours, cool to room temperature, centrifuge, and filter to obtain Zn-dpot;

[0021] Step 2: Add alkali to the metal salt to make it precipitate completely, centrifuge and dry to obtain metal hydroxide M(OH) a ;

[0022] Step 3: Disperse the Zn-dpot in step 1 and the M(OH)a in step 2 in a solvent, ultrasonically disperse for 30 to 90 minutes, transfer them to a high-pressure reactor, heat and react at 120 to 180°C for 2 to 5 days, cool and release the pressure, and centrifuge, dry the solid phase in a vacuum oven at 80 to 120°C, and grind it continuously in an agate mortar for 30 to 90 minutes after cooling to finally obtain the catalyst MxOy-Zn-dpot.

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

[0024] The mixed solvent in the step 1 is a combination of ethanol and water, methanol and water, acetonitrile and water, ethylene glycol and water, isopropanol and water, 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, and DMF and isopropanol.

[0025] As a further description of the above technical solution:

[0026] The metal salt is one of VOCl3, CeCl3, PdCl2, MgCl2, CuCl2, FeCl3, MnCl2, and NbCl5.

[0027] As a further description of the above technical solution:

[0028] The solvent in step 3 is one of water, DMA, DMF, dimethyl sulfoxide, benzyl alcohol, ethyl benzoate, and dimethyl phthalate, preferably DMF;

[0029] The alkali in step 3 is one of NaOH, KOH and ammonia water.

[0030] Beneficial effects of the present invention:

[0031] 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 MxOy@Zn-dpot catalyst. It has high added value and is in line with the concept of green chemistry.

[0032] 2. The MxOy@Zn-dpot 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.

[0033] 3. In the present invention, the metal oxide in the catalyst MxOy-Zn-dpot has high catalytic activity and good dispersibility, the Zn-based metal organic framework has abundant active sites, the transition metal sites have strong catalytic activity, and the specific surface area is large, which promotes the contact and action of 1,3-propylene glycol and CO2, and shows good catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate a method for synthesizing a cyclic carbonate, the following drawings are shown;

[0035] Figure 1 Schematic diagram of the crystal structure of Zn-dpot in the present invention. DETAILED DESCRIPTION

[0036] Example 1

[0037] The present application provides an embodiment of the present invention also provides a method for synthesizing trimethylene cyclic carbonate:

[0038] The synthesis method of trimethylene cyclic carbonate mainly comprises the following steps: in an anhydrous and oxygen-free environment, MxOy-Zn-dpot catalyst, 1,3-propylene glycol and a dehydrating agent are sequentially added to a 100mL high-pressure stainless steel reactor, wherein the dehydrating agent is 2-cyanopyridine, 3-cyanopyridine, 2-cyanofuran, 2-cyanothiophene, 2-cyanopyrimidine, isopropanol, n-butanol, tert-butanol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc., preferably 2-cyanopyridine, CO2 is introduced, and the pressure in the reactor is 1-5MPa. The reaction temperature is 60-120°C, and the preferred reaction temperature is 80-90°C. The reaction time is 2-8h, preferably 4-5h.

[0039] The reaction route is as follows:

[0040]

[0041] Example 2

[0042] This embodiment provides a method for preparing Zn-dpot, which specifically includes:

[0043] 53.5 mg Zn(NO3)26H2O and 12.4 mg H6dpot were placed in a Pyrex vial, a certain amount of mixed solvent was added, and the mixture was dissolved by ultrasonication at room temperature for 30 min to obtain a colorless transparent solution. The mixed solution was stored in an oven at 90°C for 24 h, cooled to room temperature, centrifuged, and filtered to obtain Zn-dpot. The yield was 76% (based on Zn(II)), and its crystal structure is as follows Figure 1 as shown in .

[0044] Example 3

[0045] The catalyst V2O5-Zn-dpot was prepared based on the crystalline Zn-dpot in Example 2.

[0046] Specifically, 8 mol / L ammonia water was added to VOCl3, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide V(OH)3. The prepared Zn-dpot and V(OH)3 were dispersed in DMA, ultrasonically dispersed for 30 minutes, transferred to a high-pressure reactor, and heated at 120°C for 2 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 120°C, cooled and ground, and finally the catalyst V2O5-Zn-dpot was obtained.

[0047] Example 4

[0048] The catalyst CeO2-Zn-dpot was prepared based on the crystalline Zn-dpot in Example 2.

[0049] Specifically, 8 mol / L NaOH aqueous solution was added to CeCl3, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide Ce(OH)3. The prepared Zn-dpot and the prepared Ce(OH)3 were dispersed in water, ultrasonically dispersed for 60 minutes, transferred to a high-pressure reactor, and heated at 140°C for 2 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 90°C, cooled and ground, and finally the catalyst CeO2-Zn-dpot was obtained.

[0050] Example 5

[0051] Based on the crystalline Zn-dpot in Example 2, the catalyst PdO-Zn-dpot was prepared.

[0052] Specifically, 8 mol / L KOH aqueous solution was added to PdCl2, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide Pd(OH)2. The prepared Zn-dpot and the prepared Pd(OH)2 were dispersed in DMP, ultrasonically dispersed for 30 minutes, transferred to a high-pressure reactor, and heated at 180°C for 4 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 120°C, cooled and ground, and finally the catalyst PdO-Zn-dpot was obtained.

[0053] Example 6

[0054] Based on the crystalline Zn-dpot in Example 2, the catalyst MgO-Zn-dpot was prepared.

[0055] Specifically, 8 mol / L NaOH aqueous solution was added to MgCl2, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide Mg(OH)2. The prepared Zn-dpot and the prepared Mg(OH)2 were dispersed in DMF, ultrasonically dispersed for 90 minutes, transferred to a high-pressure reactor, and heated at 120°C for 2 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 100°C, cooled and ground, and finally the catalyst MgO-Zn-dpot was obtained.

[0056] Example 7

[0057] Based on the crystalline Zn-dpot in Example 2, the catalyst CuO-Zn-dpot was prepared.

[0058] Specifically, add 8 mol / L NaOH aqueous solution to CuCl2, stir and precipitate it completely, centrifuge and dry to obtain metal hydroxide Cu(OH)2. Disperse the prepared Zn-dpot and the prepared Cu(OH)2 in water, ultrasonically disperse for 30 minutes, transfer them to a high-pressure reactor, and heat and react at 120°C for 5 days. After cooling and depressurizing, centrifuge and separate, vacuum dry the solid phase at 100°C, grind after cooling, and finally obtain the catalyst CuO-Zn-dpot.

[0059] Example 8

[0060] The catalyst Fe2O3-Zn-dpot was prepared based on the crystalline Zn-dpot in Example 2.

[0061] Specifically, 8 mol / L NaOH aqueous solution was added to FeCl3, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide Fe(OH)3. The prepared Zn-dpot and the prepared Fe(OH)3 were dispersed in DMF, ultrasonically dispersed for 90 minutes, transferred to a high-pressure reactor, and heated at 120°C for 5 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 100°C, cooled and ground, and finally the catalyst Fe2O3-Zn-dpot was obtained.

[0062] Example 9

[0063] The catalyst Nb2O5-Zn-dpot was prepared based on the crystalline Zn-dpot in Example 2.

[0064] Specifically, 8 mol / L NaOH aqueous solution was added to NbCl5, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide Nb(OH)5. The prepared Zn-dpot and the prepared Nb(OH)5 were dispersed in water, ultrasonically dispersed for 90 minutes, transferred to a high-pressure reactor, and heated at 120°C for 2 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 80°C, cooled and ground, and finally the catalyst Nb2O5-Zn-dpot was obtained.

[0065] Example 10

[0066] The catalyst MnO2-Zn-dpot was prepared based on the crystalline Zn-dpot in Example 2.

[0067] Specifically, 8 mol / L NaOH aqueous solution was added to MnCl2, stirred and precipitated completely, and centrifuged and dried to obtain metal hydroxide Mn(OH)2. The prepared Zn-dpot and the prepared Mn(OH)2 were dispersed in water, ultrasonically dispersed for 30 minutes, transferred to a high-pressure reactor, and heated at 120°C for 2 days. After cooling and depressurizing, centrifuged, the solid phase was vacuum dried at 80°C, cooled and ground, and finally the catalyst MnO2-Zn-dpot was obtained.

[0068] Embodiment 11

[0069] A method for synthesizing trimethylene cyclic carbonate: 0.04 g MnO2-Zn-dpot, 10 mmol (0.76 g) 1,3-propylene glycol and 30 mL dehydrating agent are sequentially added to 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 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.

[0070] 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:

[0071]

[0072]

[0073] Table 1

[0074] 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).

[0075] It can be seen from Table 1 that when MnO2-Zn-dpot is used as the catalyst, 2-cyanopyridine is used as the dehydrating agent, the reaction temperature is 80°C, the reaction time is 4h, and the reaction pressure is 2, 3 or 2MPa, 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 as 1MPa.

[0076] Embodiment 26

[0077] Synthesis of trimethylene carbonate using V2O5-Zn-dpot as catalyst

[0078] 0.04g V2O5-Zn-dpot, 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 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%.

[0079] Embodiment 27

[0080] Synthesis of trimethylene carbonate using CeO2-Zn-dpot as catalyst

[0081] 0.04g CeO2-Zn-dpot, 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 69%.

[0082] Embodiment 28

[0083] Synthesis of trimethylene carbonate using PdO-Zn-dpot as catalyst

[0084] 0.04g PdO-Zn-dpot, 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, and the catalyst was filtered out. The solution was vacuum-separated to obtain the target product with a yield of 75%.

[0085] Embodiment 29

[0086] Synthesis of trimethylene carbonate using MgO-Zn-dpot as catalyst

[0087] 0.04g MgO-Zn-dpot, 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, and the catalyst was filtered out. The solution was vacuum-separated to obtain the target product with a yield of 72%.

[0088] Embodiment 30

[0089] Synthesis of trimethylene carbonate catalyzed by CuO-Zn-dpot

[0090] 0.04g CuO-Zn-dpot, 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%.

[0091] Embodiment 31

[0092] Synthesis of trimethylene carbonate using Fe2O3-Zn-dpot as catalyst

[0093] 0.04g Fe2O3-Zn-dpot, 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 65%.

[0094] Embodiment 32

[0095] Synthesis of trimethylene carbonate using Nb2O5-Zn-dpot as catalyst

[0096] 0.04g Nb2O5-Zn-dpot, 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, and the catalyst was filtered out. The solution was vacuum-separated to obtain the target product with a yield of 72%.

[0097] Embodiments 33 to 37

[0098] Verification of the reusability of MnO2-Zn-dpot catalyst

[0099] The multiphase catalyst separated in Example 16 can be reused after washing with ether and drying. The catalytic yields of the five times are 86%, 86%, 85%, 85% and 83% respectively.

[0100] Comparative Example 1

[0101] Synthesis of trimethylene carbonate without catalyst

[0102] 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%.

[0103] Comparative Example 2

[0104] Synthesis of trimethylene carbonate using Zn-dpot catalyst

[0105] 0.04g Zn-dpot, 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 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 48%.

[0106] The above examples show that the use of the multiphase catalyst M of the present invention x O y -Zn-dpot is used to prepare trimethylene carbonate. The catalyst is easy to recover and reuse, has high catalytic activity, simple synthesis reaction process, high product yield, and simple and easy operation.

[0107] 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.

[0108] 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 M x O y @Zn-dpot.

2. The method for synthesizing a cyclic carbonate according to claim 1, characterized in that: The M x O y @M in Zn-dpot x O y It represents one of V2O5, CeO2, PdO, MgO, CuO, Fe2O3, MnO2, and Nb2O5; The M x O y @Zn-dpot in Zn-dpot represents the metal organic framework material synthesized from Zn(NO3)26H2O and 5,5',5"-((1,3,5-triazine-2,4,6-triyl)trioxy)triisophthalic acid [Zn7(dpot)2(H2O) 11 ]2OH 3H2O 5DMA.

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 MxOy@Zn-dpot includes the following steps: Step 1: Place Zn(NO3)26H2O and H6dpot in a Pyrex vial, add a certain amount of mixed solvent, dissolve under ultrasonication at room temperature for 30 to 60 minutes to obtain a colorless transparent solution, then store the colorless transparent solution in an oven at 80 to 120°C for 24 to 36 hours, cool to room temperature, centrifuge, and filter to obtain Zn-dpot; Step 2: Add alkali to the metal salt to make it precipitate completely, centrifuge and dry to obtain metal hydroxide M(OH) a ; Step 3: Disperse the Zn-dpot in step 1 and the M(OH)a in step 2 in a solvent, ultrasonically disperse for 30 to 90 minutes, transfer them to a high-pressure reactor, heat and react at 120 to 180°C for 2 to 5 days, cool and release the pressure, and centrifuge, dry the solid phase in a vacuum oven at 80 to 120°C, and grind it continuously in an agate mortar for 30 to 90 minutes after cooling to finally obtain the catalyst MxOy-Zn-dpot.

6. The method for synthesizing a cyclic carbonate according to claim 5, characterized in that: The mixed solvent in the step 1 is a combination of ethanol and water, methanol and water, acetonitrile and water, ethylene glycol and water, isopropanol and water, 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, and DMF and isopropanol.

7. The method for synthesizing a cyclic carbonate according to claim 5, characterized in that: The metal salt is one of VOCl3, CeCl3, PdCl2, MgCl2, CuCl2, FeCl3, MnCl2, and NbCl5.

8. The method for synthesizing a cyclic carbonate according to claim 5, characterized in that: The solvent in step 3 is one of water, DMA, DMF, dimethyl sulfoxide, benzyl alcohol, ethyl benzoate, and dimethyl phthalate, preferably DMF; The alkali in step 3 is one of NaOH, KOH and ammonia water.

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