Method for synthesizing cyclic carbonate through urea alcoholysis under photo-thermal synergistic catalysis

Abstract

The invention belongs to the technical field of chemical synthesis, and discloses a method for synthesizing cyclic carbonate through urea alcoholysis under photo-thermal synergistic catalysis. Uniformly mixing the mixed solution of methanol and ionic liquid, zinc salt and other metal salts, and reacting; and after the reaction is finished, centrifugally separating a product, washing, drying, and calcining to obtain the zinc-based homojunction photo-thermal catalyst. The method comprises the following steps: mixing urea, dihydric alcohol and a zinc-based homojunction photo-thermal catalyst, and reacting for 1-6 hours under the conditions that the light intensity is 1-150 mW / cm, the temperature is 130-160 DEG C and the pressure is 5-30 kPa to obtain the cyclic carbonate. The catalyst used in the method effectively overcomes the limitations of low target product synthesis efficiency and high reaction energy barrier in single thermocatalysis, and the yield of the synthesized cyclic carbonate can reach up to 84.1%. Through light energy excitation coupling thermocatalysis, the harshness of reaction conditions is significantly reduced, and efficient synthesis of cyclic carbonate under mild conditions is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical synthesis, in particular to a method for synthesizing cyclic carbonates. BACKGROUND

[0002] Cyclic carbonates (such as ethylene carbonate (EC) and propylene carbonate (PC)) are important environmentally friendly chemical products, which are widely used in lithium ion battery electrolyte, high-performance polymer monomer (such as polycarbonate), green solvent, gas separation membrane and pharmaceutical intermediates. With the rapid development of new energy industry, the global cyclic carbonate market demand grows at an average annual rate of over 10%, and green and efficient synthesis process is urgently needed to meet the demand of large-scale production. The mainstream method of industrial synthesis of cyclic carbonates has the following problems: using ethylene oxide / propylene oxide and CO2 as raw materials, although it meets the requirements of atom economy, but the flammable and explosive nature of alkylene oxide leads to high storage and transportation cost and poor safety, and the reaction requires high temperature and high pressure conditions, which results in high energy consumption and easy deactivation of catalyst.

[0003] Urea alcoholysis method uses cheap urea and dihydric alcohol (such as ethylene glycol) as raw materials, and the reaction conditions are mild, and the by-product ammonia can be recycled for urea synthesis, which is considered as a promising green process. However, this technology still has the following problems: the existing catalysts (such as metal oxides, ionic liquids, etc.) have large dosage, and the reaction conditions are harsh. For example, Zhang et al. prepared Zn / Mg composite oxide catalyst by urea precipitation method, compared with pure ZnO, the zinc-magnesium composite oxide has strong basicity and high specific surface area, which can effectively stabilize the catalyst and improve the yield of PC. Under the conditions of reaction time 1 h, reaction temperature 170℃ and reaction pressure 300mmHg, the yield of PC reaches 99.8%, but under the relatively mild temperature (140℃) conditions, the yield of PC is only 25%, which highlights the deficiency of the catalyst in activating the C-N bond of urea and promoting the efficiency of the cyclization reaction (10.1016 / j.catcom.2015.03.014). Deng designed a series of ionic liquid / salt binary catalysts, and used them to catalyze the alcoholysis reaction of urea and dihydric alcohol to synthesize cyclic carbonates, which confirmed that the increase of the length of imidazole alkyl side chain can improve the catalytic performance of the reaction, and the optimal catalyst C 16 mmCl-ZnCl2, under the reaction conditions of 160℃, 15kPa, 3h, the dosage of ionic liquid is 4% mol (urea), the dosage of ZnCl2 is 8% mol (urea), and the yield of EC reaches 92.2%. Although the ionic liquid can provide Lewis acid sites, its structure stability is limited at high temperature and gradually carbonizes during the recycling process, and it also faces the difficulty of separation and recovery, which is far from meeting the requirements of industrial application (10.1016 / j.molliq.2020.113883).

[0004] The current urea alcoholysis process has double limitations in catalyst design and energy utilization efficiency, how to realize high-efficiency cracking of urea C-N bond and ring esterification under near normal temperature and pressure, break through the dependence of traditional thermal catalysis on high temperature, and put forward a feasible scheme of novel urea alcoholysis synthesis of cyclic carbonate is crucial. SUMMARY

[0005] In view of the technical problems of harsh conditions and low catalytic efficiency in the process of single thermal catalytic urea alcoholysis synthesis of cyclic carbonate, the application provides a method for photo-thermal co-catalytic urea alcoholysis synthesis of cyclic carbonate.

[0006] To achieve the above object, the technical scheme of the application is as follows:

[0007] A method for photo-thermal co-catalytic urea alcoholysis synthesis of cyclic carbonate, comprising the following steps:

[0008] (1) mixing methanol and ionic liquid solution, zinc salt and other metal salts, uniformly mixing and then reacting;

[0009] (2) after the reaction is completed, the product is separated by centrifugation, washed with ethanol for three times, dried and calcined in a box furnace to obtain a zinc-based homogenous photo-thermal catalyst;

[0010] (3) mixing urea, dihydric alcohol and the zinc-based homogenous photo-thermal catalyst prepared in step (2), and reacting under the conditions of light intensity of 1-150 mW / cm 2 , temperature of 130-160 DEG C and pressure of 5-30 kPa for 1-6 h to obtain cyclic carbonate.

[0011] In step (3), the general formula of photo-thermal co-catalytic urea alcoholysis synthesis of cyclic carbonate is as follows:

[0012]

[0013] In the general formula, R1 and R2 are any one of H atom or C1-C8 alkyl; Photothermal catalysis refers to photo-thermal co-catalytic conditions.

[0014] In step (1), the molar ratio of ionic liquid to metal salt is (1-6):1.

[0015] In step (1), the molar ratio of zinc salt to other metal salt is 1:(0.15-4). Further preferably, the molar ratio of zinc salt to other metal salt is 1:(0.15-1).

[0016] The zinc salt in the above step (1) is any one of zinc sulfate, zinc chloride, zinc nitrate, zinc carbonate, zinc borate, zinc phosphate and zinc acetate; and the other metal salt is any one of calcium salt, magnesium salt, iron salt, aluminum salt, copper salt, lanthanum salt, zirconium salt and cerium salt.

[0017] Further, the anion in the other metal salt is any one of halogen ion, nitrate, sulfate, carbonate, acetate and phosphate.

[0018] The ionic liquid in the above step (1) has any one of the following structural formulae:

[0019]

[0020] wherein R1, R2, R3 and R4 are any one of C1-C8 alkyl; and the anion is any one of halogen ion, hydroxide, tetrafluoroborate, hexafluorophosphate, carboxylate and imide.

[0021] The reaction temperature in the above step (1) is 60-100℃, and the reaction time is 6-24h.

[0022] The calcination temperature in the above step (2) is 400-800℃, and the calcination time is 2-6h.

[0023] The amount of the zinc-based homojunction photo-thermal catalyst in the above step (3) is 1%-10% of the mass of urea. Further preferably, the amount of the zinc-based homojunction photo-thermal catalyst is 3%-10% of the mass of urea.

[0024] The molar ratio of urea to dihydric alcohol in the above step (3) is 1:(1-6).

[0025] The dihydric alcohol in the above step (3) is any one of ethylene glycol, 1,2-propanediol, 1,2-butanediol, cyclohexanediol, o-dihydroxybenzene, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3-chloro-1,2-propanediol and phenyl glycol.

[0026] The present application has the following advantages:

[0027] (1) The improved solvothermal method for constructing zinc-based homojunction photo-thermal catalyst provided by the present application has the advantages of simple preparation process, low cost, high catalytic performance, no environmental pollution, stable performance, easy recovery and suitability for mass production.

[0028] (2) The application provides a method for synthesizing cyclic carbonates by photo-thermal synergistic catalysis of urea alcoholysis, a zinc-based homojunction photo-thermal catalyst is constructed by improved solvothermal method, and a zinc-magnesium composite photo-thermal catalytic material with a gradient content of ZnO is controllably synthesized by adjusting the content of zinc in the assistance of ionic liquid and methanol solution. The built-in electric field formed by the homojunction interface in the structure can drive the directional separation of photo-generated carriers and inhibit the recombination of the photo-generated carriers, and the crystal face regulation realizes the spatial matching of photo-generated electrons and thermally activated molecules, thereby optimizing the reaction path. Therefore, the low synthesis efficiency and high reaction energy barrier of the target product in single thermal catalysis are effectively overcome, and the yield of the cyclic carbonates synthesized by photo-thermal catalysis under optimal conditions reaches 84.1%.

[0029] (3) In the method of the application, the process is coupled with thermal catalysis by light energy, which significantly reduces the harshness of the reaction conditions, realizes the efficient synthesis of cyclic carbonates under mild conditions, and provides a new route for the urea alcoholysis process. Moreover, the operation is simple, the product and the catalyst are easy to separate, and continuous production can be easily realized. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0031] Embodiment 1

[0032] The method for synthesizing cyclic carbonates by photo-thermal synergistic catalysis of urea alcoholysis in the embodiment is as follows:

[0033] (1) Preparation of a zinc-based homojunction photo-thermal catalyst constructed by improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate are dissolved in 30 mL of methanol, 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution is added dropwise under vigorous stirring, and after sufficient stirring, the reaction is carried out at 80°C for 12 h. After the reaction is completed, the product is centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain a zinc-based homojunction photo-thermal catalyst (ZnO@ZnMg-LDO) constructed by improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt is 4:1, and the molar ratio of ionic liquid to total amount of metal salt is 3:1.

[0034] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0035] Comparative Example 1

[0036] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 1 in that step (2) is carried out solely by thermal catalysis, as follows:

[0037] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as in Example 1.

[0038] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C and 10 kPa for 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified using the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0039] Example 2

[0040] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that magnesium nitrate is replaced with aluminum nitrate in step (1). The steps are as follows:

[0041] (1) Preparation of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of aluminum nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnAl-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0042] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0043] Comparative Example 2

[0044] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example is different from Example 2 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0045] (1) Preparation of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of aluminum nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnAl-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0046] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0047] Example 3

[0048] The method of photocatalytic urea alcoholysis for synthesizing cyclic carbonates in this example is different from Example 1 in that zirconium nitrate is used instead of magnesium nitrate in step (1), and the steps are as follows:

[0049] (1) Preparation of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of zirconium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnZr-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0050] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0051] Comparative Example 3

[0052] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example is different from Example 3 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0053] (1) Preparation of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of zirconium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnZr-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0054] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0055] Example 4

[0056] The method of photocatalytic urea alcoholysis for synthesizing cyclic carbonates in this example is different from Example 1 in that the molar ratio of zinc salt to magnesium salt is changed to 6:1, and the steps are as follows:

[0057] (1) Preparation of zinc-based homojunction photocatalyst constructed by improved solvothermal method: 12.84 mmol of zinc nitrate and 2.14 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 1:4, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0058] (2) Synthesis of cyclic carbonates: The specific process of synthesizing cyclic carbonates by urea alcoholysis was the same as in Example 1. The results of synthesizing cyclic carbonates by urea alcoholysis are shown in Table 1.

[0059] Comparative Example 4

[0060] The method of synthesizing cyclic carbonates by urea alcoholysis in this comparative example was different from Example 4 in that only thermal catalysis was used in step (2), and the steps were as follows:

[0061] (1) Preparation of zinc-based homojunction photocatalyst constructed by improved solvothermal method: The preparation steps were the same as in Example 4.

[0062] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) constructed by the improved solvothermal method prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after being separated by centrifugation and washed. The results of synthesizing cyclic carbonates by urea alcoholysis are shown in Table 1.

[0063] Example 5

[0064] The method of synthesizing cyclic carbonates by urea alcoholysis in this example was different from Example 1 in that the molar ratio of zinc salt to magnesium salt was changed to 2:1, and the steps were as follows:

[0065] (1) Preparation of zinc-based homojunction photocatalyst constructed by improved solvothermal method: 10 mmol of zinc nitrate and 5 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 1:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0066] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0067] Comparative Example 5

[0068] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example is different from Example 5 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0069] (1) Preparation of zinc-based homojunction photocatalyst constructed by improved solvothermal method: 10 mmol of zinc nitrate and 5 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 1:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0070] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0071] Example 6

[0072] The method of photocatalytic urea alcoholysis for synthesizing cyclic carbonates in this example is different from Example 1 in that the molar ratio of ionic liquid to total amount of metal salt is 1:1, and the steps are as follows:

[0073] (1) Preparation of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 15 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 1:1.

[0074] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0075] Comparative Example 6

[0076] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example is different from Example 6 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0077] (1) The preparation steps of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method are the same as in Example 6.

[0078] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0079] Example 7

[0080] The method of photocatalytic urea alcoholysis for synthesizing cyclic carbonates in this example is different from Example 1 in that the molar ratio of ionic liquid to total amount of metal salt is 6:1, and the steps are as follows:

[0081] (1) Preparation of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 90 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After stirring, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 6:1.

[0082] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0083] Comparative Example 7

[0084] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example is different from Example 7 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0085] (1) The preparation steps of the zinc-based homojunction photocatalyst constructed by the improved solvothermal method are the same as those in Example 7.

[0086] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the product yield. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0087] Example 8

[0088] The method of photocatalytic urea alcoholysis for synthesizing cyclic carbonates in this example is different from Example 1 in that the ionic liquid is tetrabutylphosphonium bromide, and the steps are as follows:

[0089] (1) The preparation of the improved solvothermal method for constructing zinc-based homojunction photocatalyst: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetrabutylphosphonium bromide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring. After stirring thoroughly, the reaction was carried out at 80°C for 12 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0090] (2) The synthesis of cyclic carbonates was carried out according to the specific process of Example 1. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0091] Comparative Example 8

[0092] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example was different from Example 8 in that only thermal catalysis was used in step (2), and the steps were as follows:

[0093] (1) The preparation of the improved solvothermal method for constructing zinc-based homojunction photocatalyst was the same as in Example 8.

[0094] (2) The synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photocatalyst (5% of the mass of urea) prepared by the improved solvothermal method in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield. The catalyst was recovered after being separated by centrifugation and washed. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0095] Example 9

[0096] The method of photocatalytic urea alcoholysis for synthesizing cyclic carbonates in this example was different from Example 1 in that the molar ratio of urea to ethylene glycol in step (2) was 1:1, and the steps were as follows:

[0097] (1) The preparation of the improved solvothermal method for constructing zinc-based homojunction photocatalyst was the same as in Example 1.

[0098] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 30 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0099] Comparative Example 9

[0100] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 9 in that step (2) is carried out solely by thermal catalysis, as follows:

[0101] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as those in Example 9.

[0102] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 30 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C and 10 kPa for 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified using the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0103] Example 10

[0104] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that the molar ratio of urea to ethylene glycol in step (2) is 1:6. The steps are as follows:

[0105] (1) The preparation of zinc-based homojunction photothermal catalysts by the improved solvothermal method is the same as in Example 1.

[0106] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 5 mmol of urea, 30 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0107] Comparative Example 10

[0108] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 10 in that step (2) is carried out solely by thermal catalysis, as follows:

[0109] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as those in Example 10.

[0110] (2) Synthesis of cyclic carbonates: 5 mmol of urea, 30 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C and 10 kPa for 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product yield was calculated based on the internal standard curve method. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0111] Example 11

[0112] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that the amount of catalyst used in step (2) is 3% of the urea mass. The steps are as follows:

[0113] (1) The preparation of zinc-based homojunction photothermal catalysts by the improved solvothermal method is the same as in Example 1.

[0114] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (3% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0115] Comparative Example 11

[0116] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 11 in that step (2) is carried out solely by thermal catalysis, as follows:

[0117] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as those in Example 11.

[0118] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (3% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C and 10 kPa for 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified using the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0119] Example 12

[0120] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that the amount of catalyst used in step (2) is 10% of the urea mass. The steps are as follows:

[0121] (1) The preparation of zinc-based homojunction photothermal catalysts by the improved solvothermal method is the same as in Example 1.

[0122] (2) Synthesis of cyclic carbonate: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (10% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1. 2 , the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0123] Comparative Example 12

[0124] The method of urea alcoholysis synthesis of cyclic carbonate in this comparative example is different from Example 12 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0125] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 12.

[0126] (2) Synthesis of cyclic carbonate: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (10% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0127] Example 13

[0128] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate in this example is different from Example 1 in that the temperature of the catalytic reaction in step (2) is 140°C, and the steps are as follows:

[0129] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0130] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 140 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0131] Comparative Example 13

[0132] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 13 in that step (2) is carried out solely by thermal catalysis, as follows:

[0133] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as those in Example 13.

[0134] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at a temperature of 140 °C, a pressure of 10 kPa, and a reaction time of 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified using the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0135] Example 14

[0136] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that the temperature of the catalytic reaction in step (2) is 160°C. The steps are as follows:

[0137] (1) The preparation of zinc-based homojunction photothermal catalysts by the improved solvothermal method is the same as in Example 1.

[0138] (2) Synthesis of cyclic carbonate: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 160°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1. 2

[0139] Comparative Example 14

[0140] The method of urea alcoholysis synthesis of cyclic carbonate in this comparative example is different from Example 14 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0141] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 14.

[0142] (2) Synthesis of cyclic carbonate: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 160°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0143] Example 15

[0144] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate in this example is different from Example 1 in that the pressure of the catalytic reaction in step (2) is 5 kPa, and the steps are as follows:

[0145] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0146] ​(2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 5 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0147] Comparative Example 15

[0148] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 15 in that step (2) is carried out solely by thermal catalysis, as follows:

[0149] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as those in Example 15.

[0150] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C, a pressure of 5 kPa, and a reaction time of 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified using the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0151] Example 16

[0152] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that the pressure of the catalytic reaction in step (2) is 30 kPa. The steps are as follows:

[0153] (1) The preparation of zinc-based homojunction photothermal catalysts by the improved solvothermal method is the same as in Example 1.

[0154] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonates was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 30 kPa, the light intensity was 100 mW / cm 2 , and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1.

[0155] Comparative Example 16

[0156] The method of urea alcoholysis synthesis of cyclic carbonates in this comparative example is different from Example 16 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0157] (1) The preparation of the zinc-based homojunction photo-thermal catalyst by the improved solvothermal method is the same as in Example 16.

[0158] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 30 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1.

[0159] Example 17

[0160] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonates in this example is different from Example 1 in that the light intensity in step (2) is changed to 1 mW / cm 2 , and the steps are as follows:

[0161] (1) The preparation of the zinc-based homojunction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0162] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonates was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 1 mW / cm 2 , and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1.

[0163] Comparative Example 17

[0164] The method of urea alcoholysis synthesis of cyclic carbonates in this comparative example is different from Example 17 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0165] (1) The preparation of the zinc-based homojunction photo-thermal catalyst by the improved solvothermal method is the same as in Example 17.

[0166] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1.

[0167] Example 18

[0168] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonates in this example is different from Example 1 in that the light intensity in step (2) is changed to 150 mW / cm 2 , and the steps are as follows:

[0169] (1) The preparation of the zinc-based homojunction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0170] (2) Synthesis of cyclic carbonate: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 150 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1. 2 , the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0171] Comparative Example 18

[0172] The method of urea alcoholysis synthesis of cyclic carbonate in this comparative example is different from Example 18 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0173] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 18.

[0174] (2) Synthesis of cyclic carbonate: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0175] Example 19

[0176] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate in this example is different from Example 1 in that the reaction time in step (2) is 1 h, and the steps are as follows:

[0177] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0178] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 1 hour. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0179] Comparative Example 19

[0180] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 19 in that step (2) is carried out solely by thermal catalysis, as follows:

[0181] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as those in Example 19.

[0182] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C and 10 kPa for 1 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified using the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0183] Example 20

[0184] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment differs from that in Example 1 in that the catalytic reaction time in step (2) is 6 hours. The steps are as follows:

[0185] (1) The preparation of zinc-based homojunction photothermal catalysts by the improved solvothermal method is the same as in Example 1.

[0186] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonates was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 6 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1. 2 , the reaction time was 6 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1.

[0187] Comparative Example 20

[0188] The method of urea alcoholysis synthesis of cyclic carbonates in this comparative example is different from Example 20 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0189] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 20.

[0190] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homogeneous junction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 6 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonates are shown in Table 1.

[0191] Example 21

[0192] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonates in this example is different from Example 1 in that the diol in step (2) is 1,2-propanediol, and the steps are as follows:

[0193] (1) The preparation of the zinc-based homogeneous junction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0194] (2) Synthesis of cyclic carbonate: The photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of 1,2-propanediol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1. 2 , the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0195] Comparative Example 21

[0196] The method of urea alcoholysis synthesis of cyclic carbonate in this comparative example is different from Example 21 in that only thermal catalysis is used in step (2), and the steps are as follows:

[0197] (1) The preparation of the zinc-based homojunction photo-thermal catalyst by the improved solvothermal method is the same as in Example 21.

[0198] (2) Synthesis of cyclic carbonate: 30 mmol of urea, 90 mmol of 1,2-propanediol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method in step (1) (5% of the mass of urea) were added to the 50 mL reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis synthesis of cyclic carbonate are shown in Table 1.

[0199] Example 22

[0200] The method of photo-thermal synergistic catalytic urea alcoholysis synthesis of cyclic carbonate in this example is different from Example 1 in that the diol in step (2) is 1,2-propanediol, and the steps are as follows:

[0201] (1) The preparation of the zinc-based homojunction photo-thermal catalyst by the improved solvothermal method is the same as in Example 1.

[0202] (2) Synthesis of cyclic carbonates: The photo-thermal synergistic catalytic reaction of urea alcoholysis to synthesize cyclic carbonates was carried out in a 50 mL photothermal reactor. The photothermal reactor was connected in sequence to a reflux condenser, an ammonia absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of 1,2-propanediol, and the zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to the 50 mL photothermal reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the light intensity was 100 mW / cm². 2 The reaction time was 3 hours. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product was quantified based on the internal standard curve method, and the product yield was calculated. The catalyst was recovered by centrifugation and washing. The results of catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0203] Comparative Example 22

[0204] The method for synthesizing cyclic carbonates by urea alcoholysis in this comparative example differs from that in Example 22 in that step (2) is carried out solely by thermal catalysis, as follows:

[0205] (1) The preparation steps of the zinc-based homojunction photothermal catalyst constructed by the improved solvothermal method are the same as in Example 22.

[0206] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of 1,2-propanediol, and a zinc-based homojunction photothermal catalyst (5% of the mass of urea) prepared in step (1) using the improved solvothermal method were added to a 50 mL reactor. The reaction was carried out under magnetic stirring at 130 °C and 10 kPa for 3 h. After the reaction, the liquid product was detected by gas chromatography equipped with a capillary column and a flame ionization detector. The product yield was calculated based on the internal standard curve method. The catalyst was recovered by centrifugation and washing. The results of the catalytic synthesis of cyclic carbonates from urea alcoholysis are shown in Table 1.

[0207] Example 23

[0208] The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis in this embodiment comprises the following steps:

[0209] (1) Preparation of the Zn-based homojunction photocatalyst constructed by improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring. After stirring sufficiently, the reaction was carried out at 60 °C for 24 h. After the reaction was completed, the product was centrifugally separated, washed with ethanol three times, dried at 100 °C for 24 h, and finally calcined at 400 °C for 6 h to obtain the Zn-based homojunction photocatalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0210] (2) Synthesis of cyclic carbonates: The reaction of urea alcoholysis for synthesizing cyclic carbonates was carried out in a photocatalytic reactor with a volume of 50 mL. The photocatalytic reactor was connected with a condensation reflux device, an ammonia gas absorption device and a vacuum pump in turn, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the Zn-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added into the photocatalytic reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield of the product. The catalyst was recovered after centrifugal separation and washing. The results of the urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1. 2 , the reaction pressure was 10 kPa, the light intensity was 100 mW / cm2, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield of the product. The catalyst was recovered after centrifugal separation and washing. The results of the urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0211] Comparative Example 23

[0212] The method of urea alcoholysis for synthesizing cyclic carbonates in this comparative example was different from Example 23 in that only thermal catalysis was used in step (2), and the steps were as follows:

[0213] (1) The preparation steps of the Zn-based homojunction photocatalyst constructed by the improved solvothermal method were the same as those in Example 23.

[0214] (2) Synthesis of cyclic carbonates: 30 mmol of urea, 90 mmol of ethylene glycol and the Zn-based homojunction photocatalyst (5% of the mass of urea) prepared in step (1) were added into the photocatalytic reactor. Under magnetic stirring, the reaction temperature was 130 °C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield of the product. The catalyst was recovered after centrifugal separation and washing. The results of the urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0215] Example 24

[0216] The method of the present embodiment for the photo-thermal synergistic catalysis of urea alcoholysis to synthesize cyclic carbonates has the following steps:

[0217] (1) Preparation of the zinc-based homojunction photo-thermal catalyst constructed by the improved solvothermal method: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in a methanol solution was added dropwise under vigorous stirring. After sufficient stirring, the reaction was carried out at 100°C for 6 h. After the reaction was completed, the product was centrifuged and washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 800°C for 2 h to obtain the zinc-based homojunction photo-thermal catalyst (ZnO@ZnMg-LDO) constructed by the improved solvothermal method. At this time, the molar ratio of zinc salt to magnesium salt was 4:1, and the molar ratio of ionic liquid to total amount of metal salt was 3:1.

[0218] (2) Synthesis of cyclic carbonates: The reaction of photo-thermal synergistic catalysis of urea alcoholysis to synthesize cyclic carbonates was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected in turn to a condensation reflux device, an ammonia gas absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photo-thermal catalyst (5% of the mass of urea) prepared in step (1) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm 2 , and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield of the product. The catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis to synthesize cyclic carbonates are shown in Table 1.

[0219] Comparative Example 24

[0220] The method of the present comparative example for the urea alcoholysis to synthesize cyclic carbonates is different from Example 24 in that only thermal catalysis is used in step (2), which has the following steps:

[0221] (1) The preparation of the zinc-based homojunction photo-thermal catalyst constructed by the improved solvothermal method is the same as in Example 24.

[0222] (2) Synthesis of cyclic carbonate: 30 mmol of urea, 90 mmol of ethylene glycol and the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method (5% of the mass of urea) prepared in step (1) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the catalytic urea alcoholysis for synthesizing cyclic carbonates are shown in Table 1.

[0223] Example 25

[0224] The method of the present embodiment for photo-thermal synergistic catalysis of urea alcoholysis for synthesizing cyclic carbonates is different from that of Example 1 in that the molar ratio of zinc salt to magnesium salt is changed to 1:4, and the steps are as follows:

[0225] (1) Preparation of zinc-based homojunction photo-thermal catalyst prepared by improved solvothermal method: 3 mmol of zinc nitrate and 12 mmol of magnesium nitrate were dissolved in 30 mL of methanol, 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring, and the mixture was stirred thoroughly and then reacted at 80°C for 12 h. After the reaction was completed, the product was centrifugally separated, washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method (ZnO@ZnMg-LDO). At this time, the molar ratio of zinc salt to magnesium salt is 1:4, and the molar ratio of ionic liquid to total amount of metal salt is 3:1.

[0226] (2) The synthesis of cyclic carbonate is the same as in Example 1.

[0227] Example 26

[0228] The method of the present embodiment for photo-thermal synergistic catalysis of urea alcoholysis for synthesizing cyclic carbonates is different from that of Example 1 in that the molar ratio of zinc salt to magnesium salt is changed to 1:4, and the steps are as follows:

[0229] (1) Preparation of zinc-based homojunction photo-thermal catalyst prepared by improved solvothermal method: 3 mmol of zinc nitrate and 12 mmol of magnesium nitrate were dissolved in 30 mL of methanol, 45 mmol of tetraethylammonium hydroxide with a content of 25 wt.% in methanol solution was added dropwise under vigorous stirring, and the mixture was stirred thoroughly and then reacted at 80°C for 12 h. After the reaction was completed, the product was centrifugally separated, washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the zinc-based homojunction photo-thermal catalyst prepared by the improved solvothermal method (ZnO@ZnMg-LDO). At this time, the molar ratio of zinc salt to magnesium salt is 1:4, and the molar ratio of ionic liquid to total amount of metal salt is 3:1.

[0230] (2) Synthesis of cyclic carbonate The specific process of the synthesis of cyclic carbonate is the same as that in Example 1.

[0231] Example 27

[0232] The method of the present example for the synthesis of cyclic carbonate by urea alcoholysis is different from that of Example 1 in that the amount of catalyst used in step (2) is 1% of the mass of urea, and the steps are as follows:

[0233] (1) Preparation of zinc-based homojunction photo-thermal catalyst by improved solvothermal method The preparation of the zinc-based homojunction photo-thermal catalyst by improved solvothermal method is the same as that in Example 1.

[0234] (2) Synthesis of cyclic carbonate: The reaction of the synthesis of cyclic carbonate by urea alcoholysis was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected in turn to a condensation reflux device, an ammonia gas absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and the zinc-based homojunction photo-thermal catalyst prepared by improved solvothermal method (1% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm 2 , and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield of the product. The catalyst was recovered after centrifugal separation and washing.

[0235] Comparative Example 25

[0236] The method of the present example for the synthesis of cyclic carbonate by urea alcoholysis is different from that of Example 1 in that the catalyst is a commercially available zinc oxide, and the steps are as follows:

[0237] The reaction of the synthesis of cyclic carbonate by urea alcoholysis was carried out in a photo-thermal reactor with a volume of 50 mL. The photo-thermal reactor was connected in turn to a condensation reflux device, an ammonia gas absorption device, and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol, and commercially available zinc oxide (5% of the mass of urea) were added to the 50 mL photo-thermal reactor. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm 2 , and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, and the product was quantified based on the internal standard curve method to calculate the yield of the product. The catalyst was recovered after centrifugal separation and washing. The results of the synthesis of cyclic carbonate by catalytic urea alcoholysis are shown in Table 1.

[0238] Comparative Example 26

[0239] The method of synthesizing cyclic carbonate by urea alcoholysis in the present comparative example is different from comparative example 25 in that only thermal catalysis is used, and the steps are as follows:

[0240] 30 mmol of urea, 90 mmol of ethylene glycol and commercially available zinc oxide (5% of the mass of urea) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the synthesis of cyclic carbonate by catalytic urea alcoholysis are shown in Table 1.

[0241] Comparative example 27

[0242] The method of synthesizing cyclic carbonate by urea alcoholysis in the present comparative example is different from example 1 in that no ionic liquid is added in the preparation method of the catalyst, and the steps are as follows:

[0243] (1) Preparation of zinc-based homogeneous junction photo-thermal catalyst: 12 mmol of zinc nitrate and 3 mmol of magnesium nitrate were dissolved in 30 mL of methanol, and under vigorous stirring, the mixture was stirred thoroughly and then reacted at 80°C for 12 h. After the reaction was completed, the product was separated by rotary evaporation, washed with ethanol three times, dried at 100°C for 24 h, and finally calcined at 600°C for 3 h to obtain the catalyst. At this time, the molar ratio of zinc salt to magnesium salt was 4:1.

[0244] (2) Synthesis of cyclic carbonate: the synthesis of cyclic carbonate by photo-thermal catalytic urea alcoholysis was carried out in a photo-thermal reaction kettle with a volume of 50 mL. The photo-thermal reaction kettle was connected in turn to a condensation reflux device, an ammonia gas absorption device and a vacuum pump, and a xenon lamp was used as the light source. 30 mmol of urea, 90 mmol of ethylene glycol and the catalyst prepared in step (1) (5% of the mass of urea) were added to the 50 mL photo-thermal reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, the light intensity was 100 mW / cm 2 , and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the product yield was calculated, and the catalyst was recovered after centrifugal separation and washing. The results of the synthesis of cyclic carbonate by catalytic urea alcoholysis are shown in Table 1.

[0245] Comparative example 28

[0246] The method of synthesizing cyclic carbonate by urea alcoholysis in the present comparative example is different from comparative example 27 in that only thermal catalysis is used, and the steps are as follows:

[0247] (1) The preparation steps of the zinc-based homogeneous junction photo-thermal catalyst are the same as those in comparative example 27.

[0248] (2) Synthesis of cyclic carbonate: 30 mmol of urea, 90 mmol of ethylene glycol and the catalyst prepared in step (1) (5% of the mass of urea) were added to a 50 mL reaction kettle. Under magnetic stirring, the reaction temperature was 130°C, the reaction pressure was 10 kPa, and the reaction time was 3 h. After the reaction was completed, the liquid product was detected by gas chromatography equipped with a capillary column and a hydrogen flame detector, the product was quantified based on the internal standard curve method, the yield of the product was calculated, and the catalyst was recovered after being washed by centrifugal separation. The results of the synthesis of cyclic carbonate by catalytic urea alcoholysis are shown in Table 1.

[0249] The results of the yield of ethylene carbonate in the above part of the examples and comparative examples are shown in Table 1.

[0250] Table 1

[0251] Group Photo-thermal synergistic catalytic yield (%) Group Thermal catalytic yield (%) Example 1 84.1 Comparative Example 1 48.8 Example 2 70.0 Comparative Example 2 40.3 Example 3 63.9 Comparative Example 3 37.7 Example 4 75.3 Comparative Example 4 30.7 Example 5 70.9 Comparative Example 5 25.1 Example 6 52.2 Comparative Example 6 30.5 Example 7 72.9 Comparative Example 7 42.8 Example 8 60.9 Comparative Example 8 35.7 Example 9 54.3 Comparative Example 9 30.2 Example 10 62.3 Comparative Example 10 35.2 Example 11 68.6 Comparative Example 11 32.5 Example 12 67.6 Comparative Example 12 32.2 Example 13 81.1 Comparative Example 13 52.6 Example 15 73.4 Comparative Example 15 43.2 Example 16 59.8 Comparative Example 16 32.2 Example 18 73.0 Comparative Example 18 47.6 Example 19 58.5 Comparative Example 19 20.5 Example 20 74.3 Comparative Example 20 38.5 Example 21 80.4 Comparative Example 21 45.4 Example 22 83.2 Comparative Example 22 40.2 Example 23 59.7 Comparative Example 23 31.3 Example 24 78.8 Comparative Example 24 54.1 Comparative Example 25 32.9 Comparative Example 26 24.5 Comparative Example 27 10.1 Comparative Example 28 6.5

[0252] The following points can be seen from Table 1:

[0253] (1) As can be seen from Examples 1-24, the zinc-based homojunction photo-thermal catalyst constructed by the improved solvothermal method has good catalytic effect in the synthesis of cyclic carbonate by photo-thermal synergistic catalytic urea alcoholysis in a mild reaction process, and the yield of cyclic carbonate can reach 84.1%.

[0254] (2) As can be seen from Examples 1-8 and Examples 23-24, when the zinc-based homojunction photo-thermal catalyst is constructed by the improved solvothermal method, the appropriate ZnO complex metal salt, the proportion of ZnO in the metal oxide, the appropriate proportion of ionic liquid, the appropriate reaction temperature and the calcination temperature have a significant influence on the structure of the catalyst. With the increase of the proportion of ZnO in the metal oxide, the photo-thermal catalytic activity also increases, and when the molar ratio of Zn to Mg is 4:1, the reaction is optimal.

[0255] (3) As can be seen from Comparative Examples 25-28, the single zinc oxide has poor photo-thermal catalytic activity, and the improved solvothermal method plays an important role in the construction of zinc-based homojunction. The catalyst synthesized under the condition of no ionic liquid has almost no activity under photo-thermal catalysis.

[0256] (3) As can be seen from Comparative Examples 1-24 and Examples 1-24, the reaction conditions play an important role in photo-thermal synergistic catalysis. This photo-thermal process relies on the synergistic effect of surface acid-base sites and photo-generated radicals. The photo-generated radicals act on the substrate adsorbed on the surface of the catalyst to reduce its activation energy barrier, and the surface acid-base sites promote the production of intermediates, thereby forming cyclic carbonate.

[0257] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for the photothermal synergistic catalytic synthesis of cyclic carbonates from urea alcoholysis, characterized in that, The steps are as follows: (1) Mix methanol and ionic liquid, zinc salt and other metal salts, and carry out the reaction after mixing evenly; (2) After the reaction is completed, the product is separated by centrifugation, washed, dried and then calcined to obtain a zinc-based homojunction photothermal catalyst. (3) Mix urea, diol and the zinc-based homojunction photothermal catalyst prepared in step (2), and heat them under light intensity of 1-150 mW / cm. 2 The reaction is carried out at a temperature of 130-160℃ and a pressure of 5-30kPa for 1-6 hours to obtain cyclic carbonates.

2. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 1, characterized in that, In step (1), the molar ratio of the total amount of ionic liquid to metal salt is (1-6):1; the molar ratio of zinc salt to other metal salts is 1:(0.15-4).

3. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 1 or 2, characterized in that, In step (1), the zinc salt is any one of zinc sulfate, zinc chloride, zinc nitrate, zinc carbonate, zinc borate, zinc phosphate, and zinc acetate.

4. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 3, characterized in that, In step (1), the other metal salts are any one of calcium salts, magnesium salts, iron salts, aluminum salts, copper salts, lanthanum salts, zirconium salts, and cerium salts.

5. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 4, characterized in that, The ionic liquid in step (1) has any of the following structural formulas: Wherein, R1, R2, R3, and R4 are any one of C1-C8 alkyl groups; the anion is any one of halide ions, hydroxide ions, tetrafluoroborate ions, hexafluorophosphate ions, carboxylate ions, and imide ions.

6. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 5, characterized in that, The reaction temperature in step (1) is 60-100℃ and the reaction time is 6-24h.

7. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 6, characterized in that, The calcination process in step (2) is carried out at a temperature of 400-800℃ for 2-6 hours.

8. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 7, characterized in that, In step (3), the amount of zinc-based homojunction photothermal catalyst used is 1%-10% of the urea mass.

9. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 8, characterized in that, In step (3), the molar ratio of urea to diol is 1:(1-6).

10. The method for synthesizing cyclic carbonates by photothermal synergistic catalytic urea alcoholysis according to claim 9, characterized in that, In step (3), the diol is any one of ethylene glycol, 1,2-propanediol, 1,2-butanediol, cyclohexanediol, catechol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3-chloro-1,2-propanediol, and phenylethylene glycol.

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