Method for continuously preparing cyclic carbonate from carbon dioxide and polyol

Abstract

The invention relates to a method for continuously preparing cyclic carbonate from carbon dioxide and polyol, which is characterized in that a continuous flow circulation reactor is adopted, cerium oxide is used as a heterogeneous catalyst, carbon dioxide and polyol are used as raw materials, and the cyclic carbonate is continuously prepared through a dehydration reaction under the conditions that the pressure is 1-10 MPa and the temperature is 80-180 DEG C. Compared with the existing intermittent reaction process, the continuous process disclosed by the invention has the characteristics of mild reaction conditions, environment friendliness, high production efficiency, stable and controllable reaction and stable quality parameters of the product.

Description

Technical Field

[0001] The invention relates to the technical field of cyclic carbonate preparation, in particular to a method for continuously preparing cyclic carbonate from carbon dioxide and polyol. Background Art

[0002] With the energy and resource crisis faced by mankind, the reduction of carbon dioxide (CO2) emissions and its chemical or physical fixation as an important C1 resource on the earth has become one of the most concerned strategic research topics in the world. Cyclic carbonates can be prepared from carbon dioxide under the action of catalysts. Cyclic carbonates are a multi-purpose industrial raw material and an important organic intermediate for the production of fine chemicals such as medicines, pesticides and dyes. They can also be used in polar aprotic solvents, lithium-ion battery electrolyte additives, polymer precursors and fuel additives. Therefore, the development of carbon dioxide to prepare cyclic carbonate technology has potential scientific significance and application value.

[0003] At present, the production processes of cyclic carbonates mainly include polyol and carbonate transesterification, CO2 and epoxide cycloaddition, and direct preparation of cyclic carbonates by CO2 and polyols. Among them, the polyol and carbonate transesterification method is limited by the preparation process of carbonates, and the CO2 and epoxide cycloaddition method has strong regionality because epoxide is a toxic and carcinogenic substance, flammable and explosive, and not suitable for long-distance transportation. For the preparation of cyclic carbonates by direct dehydration of CO2 and renewable resource polyols, the reaction raw material CO2 is cheap and easy to obtain, and renewable biomass-based polyols such as 1,2-propylene glycol, ethylene glycol, and glycerol are widely available. Therefore, the development of efficient CO2 and polyol direct dehydration catalysts is of great economic and practical significance.

[0004] At present, there are relevant literature reports on the direct preparation of cyclic carbonates from carbon dioxide and polyols at home and abroad. Tomishige used carbon dioxide and diols as reactants to directly prepare propylene carbonate in a batch reactor under the action of cerium oxide catalyst (ACS Catal. 2014, 4, 1893-1896). Lemaire used carbonate as a catalyst to catalyze the reaction of 1,2-propylene glycol and carbon dioxide to directly prepare propylene carbonate. The conversion rate of 1,2-propylene glycol was 44% and the yield of propylene carbonate was 20% (Catal. Commun. 2012, 29, 58-62). Some domestic research experts have also made certain breakthroughs in the preparation of carbonic cyclic esters from carbon dioxide and polyols. He Dehua used rod-shaped cerium oxide as a catalyst to catalyze carbon dioxide and glycerol to directly prepare glycerol carbonate in a batch reactor (Applied Catalysis A: General 2016, 513, 9-18). Wang Yanji used carbonate and acetate as catalysts to catalyze the reaction of 1,2-propylene glycol and carbon dioxide to directly prepare propylene carbonate in autoclave and fixed-bed tubular reactors, respectively. However, the selectivity of propylene carbonate and the conversion rate of 1,2-propylene glycol were both low (<60% and <25%, respectively).

[0005] The above-mentioned methods for preparing cyclic carbonates by dehydrating polyols and carbon dioxide all adopt conventional batch reactor or tubular reaction processes, which have the problems of low efficiency, high energy consumption, low conversion rate of polyols and low selectivity of product cyclic carbonates.

[0006] Therefore, there is an urgent need for a new method for directly preparing cyclic carbonates from carbon dioxide and polyols to solve the above-mentioned technical and product quality problems existing in the prior art. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a stable and efficient method for continuously preparing cyclic carbonate from carbon dioxide and polyols.

[0008] To solve the above problems, the present invention discloses a method for continuously preparing cyclic carbonates from carbon dioxide and polyols, characterized in that the method adopts a continuous flow circulation reactor, uses cerium oxide as a heterogeneous catalyst, uses carbon dioxide and polyols as raw materials, and performs a dehydration reaction under a pressure of 1 to 10 MPa and a temperature of 80 to 180°C to continuously prepare cyclic carbonates.

[0009] A reaction liquid containing a catalyst, a polyol, a dehydrating agent and a solvent is continuously added to the first reactor of the continuous flow circulation reactor, and 1-8 MPa of CO2 is introduced at the same time. The reaction liquid is heated by a circulation pump through a heat exchanger to make the pressure in the first reactor 1-10 MPa and the temperature 80-180°C. After the material level in the first reactor reaches the set value, the reaction material begins to be transferred to the aging tank. After the material level in the aging tank rises to 50%-80% of the total liquid level and the conversion rate of the polyol is ensured to reach 50%-95%, the reaction material is thermally separated by a filter to separate the catalyst and the mixed liquid containing the product; the unreacted CO2 in the aging tank is circulated; the catalyst is recycled after being calcined and regenerated at 400-900°C; the mixed liquid containing the product is separated by a distillation tower to obtain a cyclic carbonate, and the incompletely reacted polyol and the solvent are circulated at the same time.

[0010] Reaction diagram: The polyol is any one of 1,2-propylene glycol, ethylene glycol and glycerol.

[0011] The cyclic carbonate is one of ethylene carbonate, propylene carbonate and glycerol carbonate.

[0012] The dehydrating agent is 2-cyanopyridine or furan-2-cyanopyridine.

[0013] The solvent refers to one or more of 1,4-dioxane, toluene, N,N,-dimethylformamide (DMF) or N,N,-dimethylacetamide (DMAC).

[0014] The molar ratio of the continuously added catalyst to the polyol is 1:1-1:20, the mass ratio of the continuously added polyol to the solvent is 1:1-1:10, and the molar ratio of the continuously added polyol to the dehydrating agent is 1:1-1:10.

[0015] The temperature of the distillation tower is 40-160°C.

[0016] The continuous flow circulation reactor comprises a first reactor, a heat exchanger, an aging tank and a distillation tower; the top of the first reactor is respectively provided with a material reaction liquid input pipe, a CO2 input pipe and a reaction material input pipe, and the bottom is respectively provided with pipelines I and II; the material reaction liquid input pipe is connected to the mixed dissolution kettle through a feed pump; the pipeline I is connected to the bottom of the heat exchanger through a circulation pump, and the top of the heat exchanger is connected to the reaction material input pipe; the pipeline II is connected to the bottom of the aging tank, and the top of the aging tank is provided with a CO2 circulation pipe; the CO2 circulation pipe It is connected to the CO2 input pipe; the bottom of the aging tank is connected to a filter through pipeline III, and the filter is respectively provided with a catalyst drying and activation regeneration output pipeline and a pipeline IV; the pipeline IV is communicated with the top of the distillation tower, and the bottom of the distillation tower is respectively provided with a product cyclic carbonate discharge pipe and a dehydrating agent hydration product amide discharge pipe; the top of the distillation tower is provided with a polyol / dehydrating agent / solvent circulation pipe, and the polyol / dehydrating agent / solvent circulation pipe is communicated with the mixed dissolution kettle; the catalyst drying and activation regeneration output pipeline is connected to the mixed dissolution kettle.

[0017] The pipeline II, the CO2 circulation pipe, the pipeline III, the pipeline IV, and the polyol / dehydrating agent / solvent circulation pipe are respectively provided with control valves.

[0018] Compared with the prior art, the present invention has the following advantages: 1. The present invention uses CO2 and biomass-based polyols represented by ethylene glycol, 1,2-propylene glycol and propylene glycol as raw materials, and adopts a continuous flow circulation reactor to stably and continuously prepare cyclic acid esters with high yield. Not only is the reaction stable and controllable, but the operation method is simple and has good universality. At the same time, various quality parameters of the product are stable.

[0019] 2. Compared with the existing intermittent reaction process, the continuous process of the present invention has the characteristics of mild reaction conditions, environmental friendliness and high production efficiency.

[0020] 3. By adopting the method of the present invention, the conversion rate of polyols can reach up to 99%, and the selectivity of cyclic carbonate can reach up to 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0022] Figure 1 It is a schematic diagram of the continuous flow circulation reactor in the present invention.

[0023] In the figure: 1—first reactor; 21—feed pump; 22—circulation pump; 3—heat exchanger; 4—aging tank; 5—filter; 6—distillation tower; 7—material reaction liquid input pipe; 8—CO2 input pipe; 9—reaction material input pipe; 10—pipeline I; 11—pipeline II; 12—mixed dissolution kettle; 13—CO2 circulation pipe; 14—pipeline III; 15—catalyst drying and activation regeneration output pipeline; 16—pipeline IV; 17—product cyclic carbonate discharge pipe; 18—dehydrating agent hydration product amide discharge pipe; 19—polyol / dehydrating agent / solvent circulation pipe; 20—control valve. DETAILED DESCRIPTION

[0024] A method for continuously preparing cyclic carbonate from carbon dioxide and polyols, the method is to use a continuous flow circulation reactor, cerium oxide as a heterogeneous catalyst, carbon dioxide and polyols as raw materials, and carry out dehydration reaction under the conditions of pressure of 1-10 MPa and temperature of 80-180°C to continuously prepare cyclic carbonate. The specific process is as follows: A reaction liquid containing a catalyst, a polyol, a dehydrating agent and a solvent is continuously added to the first reactor 1 of the continuous flow circulation reactor, and 1-8 MPa CO2 is introduced at the same time. The circulating pump 22 is used to heat the heat exchanger 3 so that the pressure in the first reactor is 1-10 MPa and the temperature is 80-180°C. After the material level in the first reactor 1 reaches the set value, the reaction material begins to be transferred to the aging tank 4. After the material level in the aging tank 4 rises to 50%-80% of the total level and the conversion rate of the polyol is ensured to reach 50%-95%, the reaction material is thermally separated by the filter 5 to separate the catalyst and the mixed solution containing the product; the unreacted CO2 in the aging tank 4 is circulated; the catalyst is recycled after being calcined and regenerated at 400-900°C; the mixed solution containing the product is separated by the distillation tower 6 to obtain a cyclic carbonate, and the polyol and the solvent that have not been completely reacted are circulated.

[0025] In the whole process of the present invention, the material inlet and outlet balance in the first reactor 1 and the aging tank 4 needs to be controlled to maintain a stable state of continuous feeding reaction and discharging collection; the reaction residence time is controlled by adjusting the material liquid level in the first reactor 1.

[0026] Wherein: the polyol includes any one of 1,2-propylene glycol, ethylene glycol and glycerol.

[0027] The cyclic carbonate is one of ethylene carbonate, propylene carbonate and glycerol carbonate.

[0028] The dehydrating agent is 2-cyanopyridine or furan-2-cyanopyridine.

[0029] The solvent refers to one or more of 1,4-dioxane, toluene, N,N,-dimethylformamide (DMF) or N,N,-dimethylacetamide (DMAC).

[0030] The molar ratio of the continuously added catalyst to the polyol is 1:1-1:20, the mass ratio (g / g) of the continuously added polyol to the solvent is 1:1-1:10, and the molar ratio of the continuously added polyol to the dehydrating agent is 1:1-1:10.

[0031] The temperature of the distillation tower 6 is 40-160°C.

[0032] like Figure 1 As shown, the continuous flow circulation reactor includes a first reactor 1, a heat exchanger 3, an aging tank 4 and a distillation tower 6. The top of the first reactor 1 is respectively provided with a material reaction liquid input pipe 7, a CO2 input pipe 8 and a reaction material input pipe 9, and the bottom is respectively provided with a pipeline I 10 and a pipeline II 11; the material reaction liquid input pipe 7 is connected to the mixed dissolution kettle 12 through a feed pump 21; the pipeline I 10 is connected to the bottom of the heat exchanger 3 through a circulation pump 22, and the top of the heat exchanger 3 is connected to the reaction material input pipe 9; the pipeline II 11 is connected to the bottom of the aging tank 4, and the top of the aging tank 4 is provided with a CO2 circulation pipe 13; the CO2 circulation pipe 13 is connected to the CO2 input pipe 8; the aging tank The bottom of 4 is connected to a filter 5 through a pipeline III 14, and the filter 5 is respectively provided with a catalyst drying and activation regeneration output pipeline 15 and a pipeline IV 16; the pipeline IV 16 is communicated with the top of the distillation tower 6, and the bottom of the distillation tower 6 is respectively provided with a product cyclic carbonate discharge pipe 17 and a dehydrating agent hydration product amide discharge pipe 18; the top of the distillation tower 6 is provided with a polyol / dehydrating agent / solvent circulation pipe 19, and the polyol / dehydrating agent / solvent circulation pipe 19 is communicated with the mixed dissolution kettle 12; the catalyst drying and activation regeneration output pipeline 15 is connected to the mixed dissolution kettle 12.

[0033] Control valves 20 are provided on pipeline II 11, CO2 circulation pipe 13, pipeline III 14, pipeline IV 16, and polyol / dehydrating agent / solvent circulation pipe 19, respectively.

[0034] Example 1 In the mixed dissolution kettle 12, the reaction liquid containing ethylene glycol, dehydrating agent 2-cyanopyridine and 1,4-dioxane solvent containing cerium oxide catalyst is first added to the first reactor 1 through the feed pump 21 at 2.1 kg / h, the molar ratio of catalyst to ethylene glycol is controlled to be 1:10, the molar ratio of ethylene glycol to dehydrating agent is controlled to be 1:1, the temperature of the reaction system is controlled at 140°C, and CO2 is introduced to control the pressure of the reaction system to be 4 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 4 h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through the pressure relief valve. The catalyst in the reaction liquid is separated by filtration, dried, calcined at 600°C, and recycled. The separated reaction liquid is used to separate ethylene carbonate by reactive distillation. According to analysis and calculation, the conversion rate of ethylene glycol is 95%, and the selectivity of ethylene carbonate is 99%. After continuous operation for 12 hours, about 8.4 kg of ethylene carbonate was obtained, and the remaining dehydrating agent and solvent, about 5.2 kg, were recycled and reused.

[0035] Example 2 In the mixed dissolution kettle 12, the reaction liquid containing 1,2-propylene glycol, a dehydrating agent furan-2-cyanopyridine and an acetonitrile solvent containing a cerium oxide catalyst is added to the first reactor 1 through a feed pump 21 at a rate of 1.5 kg / h, the molar ratio of the catalyst to 1,2-propylene glycol is controlled to be 1:10, the molar ratio of 1,2-propylene glycol to the dehydrating agent is controlled to be 1:2, the temperature of the reaction system is controlled to be 140°C, and CO2 is introduced to control the system pressure to be 5 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 2 h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through a pressure relief valve. The catalyst in the reaction liquid is separated and dried by filtration, and then calcined at 700°C and recycled. The separated reaction liquid is used to separate propylene carbonate by a reactive distillation method. According to analysis and calculation, the conversion rate of 1,2-propylene glycol is 98%, and the selectivity of propylene carbonate is 99%. After continuous operation for 24 h, about 11.2 kg of propylene carbonate was obtained, and the remaining dehydrating agent and solvent, about 8.2 kg, were recycled and reused.

[0036] Example 3 In the mixed dissolution kettle 12, the reaction liquid containing cerium oxide catalyst, ethylene glycol, dehydrating agent 2-cyanopyridine and solvent DMF is first added to the first reactor 1 through the feed pump 21 at 2.1 kg / h, the molar ratio of the catalyst to ethylene glycol is controlled to be 1:5, the molar ratio of ethylene glycol to dehydrating agent is controlled to be 1:2, the temperature of the reaction system is controlled at 130°C, and CO2 is introduced to control the pressure of the reaction system to be 5 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 3 h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through the pressure relief valve. The catalyst in the reaction liquid is separated by filtration, and the catalyst is dried and calcined at 600°C and then recycled. The separated reaction liquid is used to separate ethylene carbonate by reactive distillation. According to analysis and calculation, the conversion rate of ethylene glycol is 98% and the selectivity of ethylene carbonate is 99%. After continuous operation for 24 hours, about 15.8 kg of ethylene carbonate was obtained, and the remaining dehydrating agent and solvent, about 10.2 kg, were recycled and reused.

[0037] Example 4 In the mixed dissolution kettle 12, the reaction liquid of glycerol, dehydrating agent 2-cyanopyridine and acetonitrile solvent containing cerium oxide catalyst is first added to the first reactor 1 through the feed pump 21 at 1.8 kg / h, the molar ratio of catalyst to glycerol is controlled to be 1:1, the molar ratio of glycerol to dehydrating agent is controlled to be 1:10, the temperature of the reaction system is controlled at 160°C, and CO2 is introduced to control the system pressure to be 5 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 5h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through the pressure relief valve. The catalyst in the reaction liquid is separated by a filter, dried, calcined at 600°C, and recycled. The separated reaction liquid is separated from glycerol carbonate by reactive distillation. According to analysis and calculation, the conversion rate of glycerol is 75% and the selectivity of glycerol carbonate is 93%. After continuous operation for 12 h, about 5.1 kg of glycerol carbonate was obtained, and the remaining unconverted glycerol, dehydrating agent and solvent, about 15.2 kg, were recovered and reused.

[0038] Example 5 In the mixed dissolution kettle 12, the reaction liquid containing 1,2-propylene glycol, a dehydrating agent 2-cyanopyridine and a DMAC solvent containing a cerium oxide catalyst is first added to the first reactor 1 through a feed pump 21 at 1.8 kg / h, and the molar ratio of the catalyst to 1,2-propylene glycol is controlled to be 1:5, and the molar ratio of 1,2-propylene glycol to the dehydrating agent is controlled to be 1:3. The temperature of the reaction system is controlled at 120°C, and CO2 is introduced to control the pressure of the reaction system to be 5 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 2 h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through a pressure relief valve. The catalyst in the reaction liquid is separated by filtration, and the catalyst is dried and calcined at 600°C and then recycled. The separated reaction liquid is used to separate propylene carbonate by a reactive distillation method. According to analysis and calculation, the conversion rate of 1,2-propylene glycol is 92%, and the selectivity of ethylene carbonate is 99%. After continuous operation for 24 h, about 15.3 kg of propylene carbonate was obtained, and the remaining unconverted 1,2-propylene glycol, dehydrating agent and solvent, about 11.4 kg, were recovered and reused.

[0039] Example 6 In the mixed dissolution kettle 12, the ethylene glycol containing cerium oxide catalyst, the dehydrating agent 2-cyanopyridine and the THF solvent reaction liquid are first added to the first reactor 1 through the feed pump 21 at 1.2 kg / h, and the molar ratio of the catalyst to ethylene glycol and the molar ratio of ethylene glycol to the dehydrating agent are controlled to be 1:5. The temperature of the reaction system is controlled at 130°C, and CO2 is introduced to control the pressure of the reaction system to be 2 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 6h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through the pressure relief valve. The catalyst in the reaction liquid is separated by filtration, and the catalyst is dried and calcined at 600°C and then recycled. The separated reaction liquid is used to separate ethylene carbonate by reactive distillation. According to analysis and calculation, the conversion rate of ethylene glycol is 94% and the selectivity of ethylene carbonate is 99%. After continuous operation for 24 h, about 4.6 kg of ethylene carbonate was obtained, and the remaining unconverted dehydrating agent and solvent, about 15.8 kg, were recovered and reused.

[0040] Example 7 In the mixed dissolution kettle 12, the reaction liquid containing cerium oxide catalyst, glycerol, dehydrating agent 2-cyanopyridine and DMF solvent is added to the first reactor 1 through the feed pump 21 at 1.5 kg / h, and the molar ratio of catalyst to glycerol is controlled to be 1:3, and the molar ratio of glycerol to dehydrating agent 2-cyanopyridine is controlled to be 1:3. The system temperature is controlled at 140°C, and CO2 is introduced to control the pressure to 6 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 5h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through the pressure relief valve. The catalyst in the reaction liquid is separated and dried by filtration, and then calcined at 800°C and recycled. The separated reaction liquid is used to separate glycerol carbonate by reactive distillation. According to analysis and calculation, the conversion rate of glycerol is 55%, and the selectivity of glycerol carbonate is 95%. After continuous operation for 24 hours, about 4.3 kg of glycerol carbonate was obtained, and the remaining unconverted glycerol, dehydrating agent and solvent, about 16.4 kg, were recovered and reused.

[0041] Example 8 In the mixed dissolution kettle 12, the reaction liquid containing 1,2-propylene glycol, a dehydrating agent furan-2-carbonitrile and a DMF solvent containing a cerium oxide catalyst is first added to the first reactor 1 through the feed pump 21 at 3.8 kg / h, and the molar ratio of the catalyst to ethylene glycol is controlled to be 1:3, and the molar ratio of ethylene glycol to the dehydrating agent is 1:1. The temperature of the reaction system is controlled at 140°C, and CO2 is introduced to control the pressure of the reaction system to be 8 MPa. The feed amount of the reaction materials is regulated so that the residence time of the reaction materials in the first reactor 1 is 3 h, and then the reaction liquid is transferred to the aging tank 4, and the excess CO2 is introduced to the first reactor 1 through the pressure relief valve. The catalyst in the reaction liquid is separated and dried by filtration and recycled after calcination at 600°C. The separated reaction liquid is separated from propylene carbonate by distillation. According to analysis and calculation, the conversion rate of 1,2-propylene glycol is 95%, and the selectivity of propylene carbonate is 99%. After continuous operation for 24 h, about 14.5 kg of propylene carbonate was obtained, and the remaining unconverted dehydrating agent and solvent, about 17.3 kg, were recovered and reused.

[0042] The reaction results of Examples 1 to 8 are shown in Table 1.

[0043] Table 1 Comparison of reaction results under different reaction conditions As can be seen from Table 1, the present invention has good technical effects, and the conversion rate of the raw material polyol and the selectivity of the target product cyclic carbonate are both relatively ideal.

Claims

1. A method for continuously preparing cyclic carbonates from carbon dioxide and polyols, characterized in that: The method refers to using a continuous flow circulation reactor, cerium oxide as a heterogeneous catalyst, carbon dioxide and polyols as raw materials, and performing a dehydration reaction under a pressure of 1 to 10 MPa and a temperature of 80 to 180°C to continuously prepare cyclic carbonates.

2. The method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 1, characterized in that: A reaction liquid containing a catalyst, a polyol, a dehydrating agent and a solvent is continuously added to a first reactor (1) of a continuous flow circulation reactor, and 1-8 MPa of CO2 is introduced at the same time. The reaction liquid is heated by a circulation pump (22) through a heat exchanger (3) to make the pressure in the first reactor 1-10 MPa and the temperature 80-180°C. After the material level in the first reactor (1) reaches a set value, the reaction material begins to be transferred to an aging tank (4). After the material level in the aging tank (4) rises to 50%-80% of the total liquid level and the conversion rate of the polyol reaches 50%-95%, the reaction material is thermally separated by a filter (5) to separate the catalyst and a mixed liquid containing the product; the unreacted CO2 in the aging tank (4) is circulated; the catalyst is calcined at 400-900°C for regeneration and then recycled; the mixed liquid containing the product is separated by a distillation tower (6) to obtain a cyclic carbonate, and the incompletely reacted polyol and the solvent are circulated at the same time.

3. A method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 1 or 2, characterized in that: The polyol is any one of 1,2-propylene glycol, ethylene glycol and glycerol.

4. A method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 1 or 2, characterized in that: The cyclic carbonate is one of ethylene carbonate, propylene carbonate and glycerol carbonate.

5. The method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 2, characterized in that: The dehydrating agent is 2-cyanopyridine or furan-2-cyanopyridine.

6. The method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 2, characterized in that: The solvent refers to one or more of 1,4-dioxane, toluene, N,N,-dimethylformamide or N,N,-dimethylacetamide.

7. The method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 2, characterized in that: The molar ratio of the continuously added catalyst to the polyol is 1:1-1:20, the mass ratio of the continuously added polyol to the solvent is 1:1-1:10, and the molar ratio of the continuously added polyol to the dehydrating agent is 1:1-1:

10.

8. The method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 2, characterized in that: The temperature of the distillation tower (6) is 40-160°C.

9. A method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 1 or 2, characterized in that: The continuous flow circulation reactor comprises a first reactor (1), a heat exchanger (3), an aging tank (4) and a distillation tower (6); the top of the first reactor (1) is provided with a material reaction liquid input pipe (7), a CO2 input pipe (8) and a reaction material input pipe (9), and the bottom is provided with a pipeline I (10) and a pipeline II (11); the material reaction liquid input pipe (7) is connected to the mixed dissolution kettle (12) through a feed pump (21); the pipeline I (10) is connected to the bottom of the heat exchanger (3) through a circulation pump (22), and the top of the heat exchanger (3) is connected to the reaction material input pipe (9); the pipeline II (11) is connected to the bottom of the aging tank (4), and the top of the aging tank (4) is provided with a CO2 circulation pipe (13); the CO2 The circulation pipe (13) is connected to the CO2 input pipe (8); the bottom of the aging tank (4) is connected to a filter (5) through a pipeline III (14), and the filter (5) is provided with a catalyst drying and activation regeneration output pipeline (15) and a pipeline IV (16); the pipeline IV (16) is connected to the top of the distillation tower (6), and the bottom of the distillation tower (6) is provided with a product cyclic carbonate discharge pipe (17) and a dehydrating agent hydration product amide discharge pipe (18); the top of the distillation tower (6) is provided with a polyol / dehydrating agent / solvent circulation pipe (19), and the polyol / dehydrating agent / solvent circulation pipe (19) is connected to the mixed dissolution kettle (12); the catalyst drying and activation regeneration output pipeline (15) is connected to the mixed dissolution kettle (12).

10. The method for continuously preparing cyclic carbonates from carbon dioxide and polyols as claimed in claim 10, characterized in that: The pipeline II (11), the CO2 circulation pipe (13), the pipeline III (14), the pipeline IV (16), and the polyol / dehydrating agent / solvent circulation pipe (19) are respectively provided with control valves (20).

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