Apparatus system and method for preparing cyclic carbonate by cycloesterification of diol

Abstract

Provided are an apparatus system and method for preparing a cyclic carbonate by cycloesterification of a diol. The apparatus system comprises a reaction unit, a gas-liquid separation unit, and a refining unit which are connected in sequence; in the reaction unit, a nitrile compound is used as an auxiliary agent to achieve cycloesterification of a diol and CO2 to synthesize a cyclic carbonate; the reaction unit comprises any one of a fixed bed reactor, a bubbling fluidized bed reactor, or a fluidized bed reactor; the liquid feeding and discharging mode of the reaction unit comprises liquid feeding from the top and discharging from the bottom, or liquid feeding from the bottom and discharging from the top; the gas-liquid separation unit comprises a first separation apparatus and a second separation apparatus which are connected in series; the refining unit comprises a light component removal tower, a heavy component removal tower, and a high-purity tower which are connected in sequence. By using a nitrile compound as an auxiliary agent to achieve efficient cycloesterification of a diol to synthesize a cyclic carbonate, the advantages of safe production process, high conversion rate, and easy and convenient operation are achieved, and a revolutionary new route is provided for industrial preparation of cyclic carbonates.

Description

A device system and method for preparing cyclic carbonate by cyclic esterification of diols Technical Field

[0001] The present application relates to the technical field of cyclic carbonate preparation, for example, a device system and method for preparing cyclic carbonate by cyclic esterification of diols. Background Art

[0002] Cyclic carbonates are primarily five-membered ring carbonates. They have excellent properties such as high solubility, low toxicity, and stable chemical properties. They are widely used as chemical intermediates and aprotic polar solvents. They can be used in lithium-ion battery electrolytes, monomers for synthesizing polycarbonates and polyurethanes, pharmaceuticals, and other fine chemical intermediates in organic synthesis. They generally have the following general formula:

[0003] At present, there are three main methods for industrial production of cyclic carbonates, namely phosgene method, transesterification method, CO2 and epoxy compound addition method and urea alcoholysis method. The traditional synthesis method phosgene method is the earliest method to realize the industrial preparation of cyclic carbonates. Because this process uses highly toxic phosgene and causes serious pollution to the environment, it does not meet the requirements of green environmental protection and has been eliminated. The transesterification method is to use linear carbonates to react with polyols to synthesize cyclic carbonates under the action of a catalyst. Because the reaction is a reversible reaction, there are problems such as low yield of the product carbonate. The method of directly catalyzing the synthesis of cyclic carbonates by CO2 and epoxy compounds has a high atomic utilization rate. Most of the existing cyclic carbonate preparation processes use this method, but the raw material epoxy compound is flammable and explosive, the production process is highly dangerous, and the tail gas recovery and treatment is difficult.

[0004] CN107915713A discloses a method for producing ethylene carbonate, and CN105541781A discloses a process for preparing cyclic carbonates. Both utilize ethylene oxide and CO₂ to react in the presence of a catalyst to produce cyclic ethylene carbonate, resulting in high yields. However, ethylene oxide has an explosion risk over almost its entire concentration range, posing significant safety risks during the production process. CN115724819A discloses an apparatus and method for preparing ethylene carbonate. This method utilizes low-concentration ethylene oxide and CO₂ to synthesize ethylene carbonate, thereby reducing safety risks during the production process. However, achieving low ethylene oxide concentrations requires the use of a large amount of ethylene carbonate as an absorbing liquid for the ethylene oxide, resulting in high equipment investment and heavy operating loads. CN104059047A discloses a continuous reaction process for synthesizing cyclic carbonates from urea. This method uses a multi-reactor reaction device connected in series, and uses urea and polyols as raw materials to synthesize cyclic carbonates with a yield of over 96%. However, the process is long and the operation is complicated. In addition, the recovery of ammonia released during the reaction increases energy consumption and environmental protection costs.

[0005] At present, the preparation of cyclic carbonates from diol compounds at home and abroad is basically in the laboratory basic research stage, and there is no public report on industrialization.

[0006] Huang Shiyong et al. reported that CO2 and 1,2-propylene glycol were reacted to prepare propylene carbonate under the conditions of anhydrous zinc acetate as catalyst and acetonitrile as solvent and dehydrating agent, and the yield reached 24.2%. Under the same reaction conditions, the yield of CO2 and ethylene glycol reaction was only 10.8% (referring to "Synthesis of Cyclic Carbonates from Carbon Dioxide and Diols on Acetate", Huang Shiyong et al., Journal of Fuel Chemistry, Vol. 35, No. 6, pp. 701-705). Du Ya et al. reported that 1,2-propylene glycol and supercritical CO2 were catalyzed by an organotin compound to synthesize propylene carbonate. By adding a cosolvent DMF and a dehydrating agent ketal to the reaction system, the reaction was promoted. However, both the reagent propylene glycol and DMF required dehydration and distillation pretreatment before the reaction (referring to "Sn-catalyzed synthesis of propylene carbonate from propylene glycol and CO2 under supercritical conditions", J. Mol. Catal. A-Chem., Vol. 241, No. 1-2, pp. 233-237). Yu Na Lim et al. reported the synthesis of cyclic and linear carbonates from CO2 and various alcohol compounds in the absence of metal catalysts and inorganic bases. The reaction system used two equivalents of the organic base DBU as an auxiliary agent, an ionic liquid as a catalyst, and dibromomethane as a reaction solvent. The yield of ethylene carbonate could reach 74% (see "Metal-Free Synthesis of Cyclic and Acyclic Carbonates from CO2 and Alcohols", Yu Na Lim et al., Eur. J. Org. Chem., Vol. 2014, No. 9, pp. 1823-1826). However, this reaction has problems such as the high price of dibromomethane and the recovery of the ionic liquid. A. Brege et al. reported the use of a dual organic system combining an organic base and an organic halide to promote the coupling reaction of CO2 and diols. They introduced two dual organic catalytic systems, DBU / EtBr and TEA / TsCl, respectively. When ethylene glycol was used as the reaction substrate, the selectivity for ethylene carbonate was 69% and the yield was 44% (see "The coupling of CO2 with diols promoted by organic dual systems: Towards products divergence via benchmarking of the performance metrics", A. Brege et al., J. CO2 Util., Vol. 38, pp. 88-98). However, both systems produced a large amount of byproducts, and the byproducts of the DBU / EtBr system were mainly dicarbonate compounds.

[0007] In summary, the current industrial method for preparing cyclic carbonates is the reaction of epoxides with CO2. However, the flammability and explosion hazards of epoxides have limited the market development of this technology. The route for preparing cyclic carbonates using CO2 and diols is still in the basic exploration stage, with no publicly available process equipment or methods. Therefore, after years of tireless research and exploration, our team has developed and proposed a safer, simpler, and more revolutionary device and method for preparing cyclic carbonates. Using CO2 and diols as raw materials, the reaction, with the aid of nitrile compounds, produces high-purity cyclic carbonates, achieving transformative development in the carbonate industry.

[0008] Summary of the Invention

[0009] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0010] The present application provides an apparatus system and method for preparing cyclic carbonates by cyclic esterification of diols, which utilizes nitrile compounds as auxiliary agents to achieve efficient cyclic esterification of diols to synthesize cyclic carbonates. The method has a high diol conversion rate and has the advantages of a safe and simple process and stable product quality, providing a revolutionary new route for the preparation of cyclic carbonates.

[0011] In a first aspect, the present application provides a device system for preparing cyclic carbonate by cyclic esterification of diols, the device system comprising a reaction unit, a gas-liquid separation unit and a refining unit connected in sequence;

[0012] The reaction unit uses a nitrile compound as an auxiliary agent to realize the cyclic esterification of diol and CO2 to synthesize cyclic carbonate; the reaction unit includes any one of a fixed bed reactor, a bubbling bed reactor or a fluidized bed reactor; the liquid inlet and outlet mode of the reaction unit includes upper inlet and lower outlet or lower inlet and upper outlet;

[0013] The gas-liquid separation unit comprises a first separation device and a second separation device arranged in series;

[0014] The refining unit includes a light removal tower, a heavy removal tower and a high-purity tower which are connected in sequence.

[0015] The device system for preparing cyclic carbonates by cyclic esterification of diols described in this application uses diol compounds and CO2 as reaction raw materials and nitrile compounds as dehydrating agents in the reaction unit to safely and efficiently prepare cyclic carbonates. The material at the outlet of the reaction unit enters a gas-liquid separation unit, which can not only improve the purity of the cyclic carbonate but also effectively reduce the loss of the raw material CO2. The liquid phase then enters a refining unit to further ensure that the target product cyclic carbonate meets high purity index requirements. The entire process has a high conversion rate of diol raw materials and stable quality of cyclic carbonates.

[0016] The light removal tower, heavy removal tower and high-purity tower described in this application are all equipped with a liquid inlet, a tower top liquid outlet and a tower bottom liquid outlet. The internal parts can be one of the packings or tower trays or a combination of the two. The tower bottom reboiler can be any one of a kettle reboiler, a vertical thermosyphon reboiler or a horizontal thermosyphon reboiler.

[0017] The light-removing tower, weight-removing tower and high-purity tower of the refining unit described in this application are all vacuum operations, and the top of the tower is connected to the vacuum pump through a pipeline. In order to reduce the loss of materials due to vacuum extraction, a condenser, a gas-liquid separator and a mechanical pump are provided on the top liquid outlet of the light-removing tower and the liquid inlet connecting pipeline of the reaction unit, respectively. It is possible to remove a small amount of gas in the circulating nitrile compound and circulate the nitrile compound to the reaction unit for reuse; the pipeline after the mechanical pump is divided into two roads, one of which flows back to the top of the light-removing tower through a pressure reducing valve, and the other is circulated to the reaction unit to continue the reaction. A mechanical pump is provided on the tower bottom liquid outlet of the light-removing tower and the liquid inlet connecting pipeline of the weight-removing tower.

[0018] In one embodiment, the reaction unit includes any one of a jacket heat exchanger, a shell and tube heat exchanger, or a built-in heat exchanger.

[0019] In one embodiment, when the reaction unit is a fixed bed reactor, a material input and output method of liquid inlet from top and liquid outlet from bottom is adopted.

[0020] In one embodiment, when the reaction unit is a bubbling bed reactor, a material input and output method of liquid inlet at the bottom and liquid outlet at the top is adopted.

[0021] In one embodiment, when the reaction unit is a fluidized bed reactor, a material input and output method of liquid inlet at the bottom and liquid outlet at the top is adopted.

[0022] In one embodiment, the reaction unit is provided with a heater for maintaining the temperature of the reaction process and ensuring the reaction conversion efficiency, wherein the medium of the heater is any one of hot water, steam or thermal oil.

[0023] In one embodiment, the gas outlet of the first separation device is connected to the gas inlet of the reaction unit via a compression device, so that the gas phase in the reaction liquid can be separated and circulated to the reaction unit for reuse.

[0024] A heat exchange device is also provided on the pipeline connecting the air outlet of the first separation device of the present application and the air inlet of the reaction unit to ensure that the temperature of the circulating gas before entering the compressor meets the safe operation requirements.

[0025] In one embodiment, a heat exchange device is provided on the pipeline connecting the liquid outlet of the second separation device and the liquid inlet of the lightness removal tower, for controlling the thermal state of the material entering the lightness removal tower.

[0026] In one embodiment, the liquid outlet of the light-removal tower is connected to the liquid inlet of the reaction unit, and the light component nitrile compounds and unreacted diol compounds separated by the light-removal tower are recycled to the reaction unit, which can effectively improve the conversion rate of the diol raw material.

[0027] In one embodiment, the heavy removal tower is connected to the lower part of the light removal tower.

[0028] The majority of the heavy components, such as amide compounds, separated by the de-weighting tower described in this application enter the additive regeneration unit, where they are regenerated into effective additives through catalytic dehydration. The de-weighting tower separates the small amount of recombinant compounds introduced from the product cyclic carbonate. High-purity cyclic carbonate is extracted from the sideline of the high-purity tower and the top of the tower as an industrial-grade product. The heavy components in the bottom of the tower are analyzed and tested and then recycled to the de-weighting tower for further use.

[0029] In one embodiment, a mechanical pump is provided in the pipeline connecting the liquid outlet of the bottom of the de-heavy tower and the lower liquid inlet of the de-light tower, and the produced liquid from the liquid outlet of the bottom of the de-heavy tower is circulated to the lower liquid inlet of the de-light tower after being tested and analyzed.

[0030] In one embodiment, the refining unit further includes a crystallization device to prevent by-product heavy components or light components that form azeotropes and are difficult to separate from the by-products from being carried into subsequent refining systems and affecting product quality.

[0031] In one embodiment, the crystallization device is disposed between the deweighting tower and the high-purity tower.

[0032] When cyanopyridine solvent is used as an auxiliary agent to prepare cyclic propylene carbonate in the present application, since cyanopyridine solvent and cyclic propylene carbonate easily form an azeotrope, a crystallization device needs to be set between the deweighting tower and the high-purity tower to achieve the preparation of high-purity cyclic propylene carbonate.

[0033] In one embodiment, the crystallization device comprises an evaporative crystallizer or a cooling crystallizer.

[0034] In one embodiment, the high-purity column is connected to a weight removal column.

[0035] In one embodiment, the bottom liquid outlet of the deweighting column is connected to an auxiliary agent regeneration unit, enabling the regeneration and recycling of the nitrile compound auxiliary agent. Within the auxiliary agent regeneration unit, the amide compounds in the heavy fraction can be nitrilated and regenerated using a high-efficiency dehydrating agent, such as potassium oxide, sodium oxide, calcium oxide, or phosphorus pentoxide, to regenerate the amide compounds into nitrile compounds for further use.

[0036] In a second aspect, the present application further provides a method for preparing cyclic carbonate by cyclic esterification of diols, wherein the method is carried out using the apparatus system for preparing cyclic carbonate by cyclic esterification of diols described in the first aspect;

[0037] The method comprises using a nitrile compound as an auxiliary agent to realize the cyclic esterification of diols to synthesize cyclic carbonates. The specific reaction process is as follows:

[0038] wherein the diol comprises a vicinal diol;

[0039] The R1 and R2 groups in the molecular structure of the diol include any one of a hydrogen group, a methyl group, an ethyl group or a propyl group;

[0040] The R3 group in the molecular structure of the nitrile compound includes any one of ethyl, benzyl, pyridine, pyrimidine, pyrazine, imidazole or quinoline.

[0041] In one embodiment, the method comprises the following steps:

[0042] (a) CO2 gas is introduced from the gas inlet of the reaction unit, and a mixed solution of diol and nitrile compound is introduced from the liquid inlet of the reaction unit. Under the action of the catalyst in the reaction unit, the diol and CO2 are cyclically esterified to form a cyclic carbonate;

[0043] (b) the reaction material extracted from the reaction unit in step (a) enters a first separation device and a second separation device in sequence for gas-liquid separation, wherein the gas phase is extracted from the gas outlet of the first separation device and enters the gas inlet of the reaction unit; the liquid phase is extracted from the liquid outlet of the second separation device and enters the refining unit for refining;

[0044] (c) the solution extracted from the liquid outlet of the second separation device in step (b) passes through a light fraction removal tower, and the light component is extracted from the top liquid outlet of the light fraction removal tower and circulated to the reaction unit in step (a) to continue the reaction;

[0045] (d) The cyclic carbonate solution extracted from the bottom liquid outlet of the light removal tower in step (c) enters a de-weighting tower for removal of heavy components, the solution extracted from the top liquid outlet of the de-weighting tower is extracted or circulated to the lower liquid inlet of the de-weighting tower for further light separation, and the liquid phase extracted from the de-weighting tower enters a high-purity tower for separation and purification before extraction.

[0046] In one embodiment, the reaction unit is filled with a heterogeneous catalyst and / or a homogeneous catalyst.

[0047] In one embodiment, the heterogeneous catalyst comprises any one of silicon oxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, tin oxide, lanthanum oxide, cerium oxide, cobalt oxide, dialkyl zinc oxide, dialkyl tin oxide, dialkyl lanthanum oxide, dialkyl cerium oxide or dialkyl cobalt oxide, or a combination of at least two thereof, wherein typical but non-limiting combinations include a combination of silicon oxide and aluminum oxide, a combination of iron oxide and copper oxide, a combination of zinc oxide and tin oxide, a combination of lanthanum oxide and cobalt oxide or a combination of dialkyl zinc oxide and dialkyl cerium oxide.

[0048] In one embodiment, the shape of the heterogeneous catalyst includes any one of powder, granules, spheres, rods, cubes or polyhedrons, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of powder and granules, a combination of spheres and rods, a combination of cubes and powders, or a combination of polyhedrons and spheres.

[0049] In one embodiment, the homogeneous catalyst comprises any one or a combination of at least two of zinc bromide, tin bromide, cerium bromide, tetraalkylphosphonium bromide, trialkylethylphosphonium bromide, tetraphenylphosphonium bromide, triphenylbutylphosphonium bromide, zinc acetate, tin acetate or cerium acetate, wherein typical but non-limiting combinations include a combination of zinc bromide and cerium bromide, a combination of tetraalkylphosphonium bromide and trialkylethylphosphonium bromide, a combination of tetraphenylphosphonium bromide and zinc acetate or a combination of tin acetate and tetraalkylphosphonium bromide.

[0050] In one embodiment, the nitrile compound includes any one or a combination of at least two of acetonitrile, cyanoquinoline, cyanopyridine, cyanopyrazine, benzyl cyanide, cyanopyrimidine or 1H-imidazole-4-carbonitrile, wherein typical but non-limiting combinations include a combination of acetonitrile and cyanoquinoline, a combination of cyanopyridine and cyanopyrazine or a combination of benzyl cyanide and 1H-imidazole-4-carbonitrile.

[0051] In one embodiment, the molar ratio of the diol to the nitrile compound in step (a) is 1:(1-20), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:8, 1:10, 1:15 or 1:20, etc., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, and 1:5 can be selected.

[0052] In one embodiment, the feed molar ratio of the diol to CO2 in step (a) is 1:(1-10), for example, it can be 1:1, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and 1:1.5 can be selected.

[0053] In one embodiment, the temperature of the reaction unit in step (a) is 50 to 200°C, for example, 50°C, 70°C, 90°C, 110°C, 130°C, 150°C, 170°C or 200°C, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable; it can be optionally 100 to 130°C.

[0054] The pressure is 100-1500 kPa, for example, it can be 100 kPa, 200 kPa, 300 kPa, 400 kPa, 500 kPa, 800 kPa, 1000 kPa or 1500 kPa, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable; it can be selected as 500-800 kPa.

[0055] In one embodiment, the pressure of the first separation device in the gas-liquid separation unit in step (b) is 100 to 1500 kPa, for example, it can be 100 kPa, 200 kPa, 300 kPa, 400 kPa, 500 kPa, 800 kPa, 1000 kPa or 1500 kPa, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In one embodiment, the pressure of the second separation device in step (b) is 100 to 600 kPa, for example, it can be 100 kPa, 200 kPa, 300 kPa, 400 kPa, 500 kPa or 600 kPa, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable; it can be optionally 100 to 300 kPa.

[0057] In one embodiment, the operating pressure of the lightness removal tower in step (c) is 2 to 100 kPa, for example, it can be 2 kPa, 4 kPa, 6 kPa, 8 kPa, 10 kPa, 20 kPa, 50 kPa or 100 kPa, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable; it can be optionally 2 to 5 kPa.

[0058] In one embodiment, the operating pressure of the deweighting tower in step (c) is 2 to 100 kPa, for example, it can be 2 kPa, 4 kPa, 6 kPa, 8 kPa, 10 kPa, 20 kPa, 50 kPa or 100 kPa, but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable; it can be optionally 2 to 5 kPa.

[0059] In one embodiment, the operating pressure of the high-purity tower in step (c) is 2 to 100 kPa, for example, it can be 2 kPa, 4 kPa, 6 kPa, 8 kPa, 10 kPa, 20 kPa, 50 kPa or 100 kPa, but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable; it can be optionally 2 to 5 kPa.

[0060] In one embodiment, the liquid phase extracted from the deweighting tower in step (d) first enters a crystallization device and then enters a high-purity tower for separation and purification.

[0061] According to the needs of product separation and purification, in order to prevent the by-product heavy components or residual light component solvent from being carried into the subsequent refining system and affecting product quality, the refining unit can be equipped with a crystallizer to achieve separation and purification of the product and the heavy components or light components. The crystallizer can be arranged between the de-weighting tower and the high-purity tower and connected by a pipeline; the liquid inlet of the high-purity tower is connected to the side line liquid outlet of the de-weighting tower, the tower bottom liquid outlet, or at least one of the withdrawal ports of the crystallizer by a pipeline. In particular, when cyanopyridine solvent is used as an auxiliary agent to prepare cyclic ethylene carbonate, the by-product amide heavy components have a high melting point, so the cyclic ethylene carbonate can be separated and purified by a crystallizer. The purified cyclic ethylene carbonate can then be refined by a high-purity tower to obtain high-purity cyclic ethylene carbonate; however, if the process is not treated by a crystallizer, the purity of the final cyclic ethylene carbonate will not change much.

[0062] In the preparation process of cyclic propylene carbonate, since cyanopyridine solvent and cyclic propylene carbonate easily form azeotropes, ordinary distillation is difficult to separate them. A crystallizer and a high-purity tower must be used to prepare high-purity cyclic propylene carbonate.

[0063] As an optional technical solution of this application, the method includes the following steps:

[0064] (a) CO2 gas is introduced from the air inlet of the reaction unit, and a mixed solution of a diol and a nitrile compound in a molar ratio of 1:(1-20) is introduced from the liquid inlet of the reaction unit, and the diol and CO2 are cyclically esterified under the action of a catalyst in the reaction unit to form a cyclic carbonate; the feed molar ratio of the diol to the CO2 is 1:(1-10); the temperature of the reaction unit is 50-200°C, and the pressure is 100-1500 kPa;

[0065] (b) the reaction material extracted from the reaction unit in step (a) enters a first separation device with a pressure of 100 to 1500 kPa and a second separation device with a pressure of 100 to 600 kPa in sequence for gas-liquid separation, the gas phase is extracted from the gas outlet of the first separation device and enters the gas inlet of the reaction unit; the liquid phase is extracted from the liquid outlet of the second separation device and enters the refining unit for refining;

[0066] (c) the solution extracted from the liquid outlet of the second separation device in step (b) passes through a light fraction removal tower having an operating pressure of 2 to 100 kPa, and the light component is extracted from the top liquid outlet of the light fraction removal tower and circulated to the reaction unit in step (a) for further reaction;

[0067] (d) The cyclic carbonate solution extracted from the bottom liquid outlet of the lightness removal tower in step (c) enters a deweighting tower with an operating pressure of 2 to 100 kPa to remove heavy components, the solution extracted from the top liquid outlet of the deweighting tower is extracted or circulated to the lower liquid inlet of the deweighting tower to continue lightness separation, and the liquid phase extracted from the deweighting tower directly enters a high-purity tower with an operating pressure of 2 to 100 kPa for separation and purification, or first enters a crystallization device and then enters a high-purity tower with an operating pressure of 2 to 100 kPa for separation and purification before being extracted.

[0068] Compared with the related art, this application has at least the following beneficial effects:

[0069] (1) The device system for preparing cyclic carbonates by cyclic esterification of diols provided in this application utilizes CO2 and diol compounds in excess in the market as raw materials to produce cyclic carbonates, a high-value new energy solvent product, which is in line with the concept of green, environmentally friendly and low-carbon development and expands the preparation route of cyclic carbonates;

[0070] (2) The present application utilizes nitrile compounds as auxiliary agents to efficiently promote the cyclic esterification reaction of diols and CO2 to prepare cyclic carbonates, thereby avoiding the use of flammable and explosive alkylene oxides as reaction raw materials, improving the safety of the cyclic carbonate production process and facilitating market promotion and use;

[0071] (3) The present application utilizes a gas-liquid separation unit and a refining unit to recycle the separated CO2 and nitrile compounds, which greatly improves the raw material conversion rate, thereby improving the production efficiency and economy of the process;

[0072] (4) The method for preparing cyclic carbonates by cyclic esterification of diols provided in this application is an endothermic reaction with mild reaction conditions, a simple separation process, and is easy to scale up for production.

[0073] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0075] FIG1 is a schematic diagram of an apparatus system for preparing cyclic carbonates by cyclic esterification of diols provided in Example 1 of the present application.

[0076] FIG2 is a schematic diagram of the apparatus system for preparing cyclic carbonates by cyclic esterification of diols provided in Example 4 of the present application.

[0077] In the figure: 1-reaction unit; 2A-first separation tank; 2B-second separation tank; 3-light removal tower; 4-heavy removal tower; 5-high purity tower; 6-compression device; 7-first mechanical pump; 8-second mechanical pump; 9-crystallization device. DETAILED DESCRIPTION

[0078] The technical solution of the present application will be further explained below with reference to the accompanying drawings and through specific implementation methods.

[0079] The following is a further detailed description of the present application. However, the following examples are merely simplified examples of the present application and do not represent or limit the scope of protection of the present application. The scope of protection of the present application shall be subject to the claims.

[0080] It should be understood that in the description of this application, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise specified, "multiple" means two or more.

[0081] It should be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0082] Those skilled in the art should understand that this application must include the necessary pipelines, conventional valves and general pump equipment for realizing the complete process, but the above content does not belong to the main application points of this application. Those skilled in the art can add layouts on their own based on the process flow and equipment structure selection, and this application does not make special requirements and specific limitations on this.

[0083] Example 1

[0084] This embodiment provides a device system for preparing cyclic carbonates by cyclic esterification of diols, a schematic diagram of which is shown in FIG1 .

[0085] The device system comprises a reaction unit 1, a gas-liquid separation unit and a refining unit connected in sequence;

[0086] The gas-liquid separation unit comprises a first separation tank 2A ​​and a second separation tank 2B arranged in series;

[0087] The refining unit includes a light removal tower 3, a heavy removal tower 4 and a high-purity tower 5 which are connected in sequence.

[0088] The reaction unit 1 is a fixed bed tubular reactor with a built-in immobilized heterogeneous catalyst and a reaction temperature maintained by steam at 150°C.

[0089] The gas outlet of the first separation device 2A is connected to the gas inlet of the reaction unit 1 via the compression device 6;

[0090] The liquid outlet of the light removal tower 3 is connected to the liquid inlet of the reaction unit 1;

[0091] The heavy removal tower 4 is connected to the lower part of the light removal tower 3.

[0092] In this embodiment, the fixed-bed tubular reactor is used to realize the loading of the immobilized heterogeneous catalyst, thereby avoiding the problem of catalyst separation and simplifying the process; at the same time, the heat medium can realize uniform heat supply during the reaction process through the shell cavity of the tubular reactor, with high heat transfer efficiency and stable temperature control during the reaction process.

[0093] Example 2

[0094] This embodiment provides an apparatus system for preparing cyclic carbonates by cyclic esterification of diols. The apparatus system is the same as that of Example 1, except that reaction unit 1 is a bubbling bed reactor, the cyclic esterification of diols is catalyzed by continuously replenishing a homogeneous catalyst, and 150°C heat transfer oil is passed into the jacket of the bubbling bed reactor or the built-in heat exchanger to maintain the reactor bed temperature.

[0095] In this embodiment, a bubbling bed reactor is used to achieve sufficient contact between the gas CO2 and the diol raw material and the homogeneous catalyst, and the high gas-liquid mass transfer rate promotes the improvement of the reaction rate; at the same time, the heat medium is passed through the jacket shell of the bubbling bed or the built-in heat exchanger to ensure the heat required for the reaction. The structure is simple, the cost is low, and it is easy to scale up.

[0096] Example 3

[0097] This embodiment provides an apparatus system for preparing cyclic carbonates by cyclic esterification of diols. The apparatus system is the same as that of Example 1, except that the reaction unit 1 is a fixed-bed tubular reactor, inert random metal fillers are built into the reaction tubes, the diol cyclic esterification is catalyzed by continuously replenishing a homogeneous catalyst, and the reactor bed temperature is maintained by using shell medium-pressure 150°C boiler hot water.

[0098] In this embodiment, a fixed-bed tubular reactor and its system are used, and metal fillers loaded in the reactor tubes are used to enhance the gas-liquid contact mass transfer efficiency. At the same time, the advantages of high activity and uniform contact of homogeneous catalysts are combined to ensure the uniformity of the reaction rate in the reactor.

[0099] Example 4

[0100] This embodiment provides a device system for preparing cyclic carbonates by cyclic esterification of diols, a schematic diagram of which is shown in FIG2 .

[0101] The device system is characterized by a fluidized bed reactor, in which the reaction unit 1 is a fluidized bed reactor, which is filled with a granular or powdered heterogeneous catalyst to catalyze the cyclic esterification of diols, and the reactor bed temperature is maintained by steam at 150°C;

[0102] The refining unit further includes a crystallization device 9; the crystallization device 9 is arranged between the deweighting tower 4 and the high-purity tower 5; the crystallization device 9 is an evaporation crystallizer; except that the high-purity tower 5 is connected to the deweighting tower 4, the rest is the same as Example 1.

[0103] In this embodiment, the reaction unit is a fluidized bed reactor, primarily suitable for heterogeneous catalyst systems with smaller particle sizes. This provides a large contact area between the gas, liquid, and solid phases, and low diffusion resistance within the reaction mass transfer. This significantly increases the reaction mass and heat transfer rates, fully utilizing the catalyst's effectiveness. During the reaction, the reactor is preloaded with heterogeneous catalyst particles. The flow of gas and liquid drives the catalyst particles through the bed, improving the reaction mass and heat transfer efficiency.

[0104] Example 5

[0105] This embodiment provides a method for preparing cyclic carbonate by cyclic esterification of diols. The method is carried out using the apparatus system for preparing cyclic carbonate by cyclic esterification of diols described in Example 1. The method specifically comprises the following steps:

[0106] (1) Cyanopyridine was used as an auxiliary agent. The feed rate of the reaction raw material ethylene glycol s1 was 96 kg / h, and the feed rate of CO2 (s3) was 66.3 kg / h. The heterogeneous catalyst ZnO / Al2O3 was loaded into the tubes of the fixed-bed tube reactor. The operating pressure was 500 kPa. The reaction temperature was controlled at 100°C by medium-pressure steam. The molar ratios of ethylene glycol to cyanopyridine and CO2 at the reactor inlet were controlled to be 1:5 and 1:1.5, respectively. An ethylene carbonate solution s5 containing 6.9% CO2 was extracted from the reactor outlet and entered into a first separation tank 2A ​​for gas-liquid separation. The operating pressure of the first separation tank 2A ​​was controlled to be 500 kPa for adiabatic flash evaporation. 96% CO2 (s6) was extracted from the top of the first separation tank 2A ​​and returned to the reactor through a compressor 6 for further use. The total gas feed entering the reactor was s4. The pressure of the second separation tank 2B is controlled to be 300 kPa, and the liquid phase is extracted from the liquid outlet at the bottom of the first separation tank 2A ​​and enters the second separation tank 2B to continue separating the residual gas phase components;

[0107] (2) the liquid phase s8 extracted from the second separation tank 2B in step (1) is fed into a lightness removal column 3 for separation, wherein the feed s8 contains 7.4% ethylene carbonate and 77.4% cyanopyridine, the operating pressure at the top of the lightness removal column 3 is controlled to be 4 kPa, the top temperature is controlled to be 118° C., the number of theoretical plates is 21, the feed position is the 9th plate, the gas phase extracted from the top is condensed, 70% of the material s7 is pressurized by a first mechanical pump 7 (s9) and circulated back to the reactor, the total liquid feed entering the reactor is s2, and 30% of the material is refluxed to the top of the lightness removal column 3 after passing through a pressure reducing valve;

[0108] (3) The ethylene carbonate solution s10 extracted from the bottom of the light removal tower 3 enters the heavy removal tower 4, the tower top operating pressure is controlled to 2 kPa, the theoretical number of tower plates is 18, and the feed position is the 13th tower plate. The 99% ethylene carbonate solution s11 extracted from the top of the heavy removal tower is pressurized by a mechanical pump 8 (s12) and circulated back to the light removal tower. The 97.2% amide heavy components s13 extracted from the bottom of the tower are sent to the auxiliary agent regeneration unit, and 99.9% ethylene carbonate is extracted from the side line.

[0109] (4) Ethylene carbonate s14 withdrawn from the side line of deweighting tower 4 enters high-purity tower 5. The operating pressure at the top of the tower is controlled to 3 kPa, the number of theoretical plates is set to 25, the feed position is the 20th plate, the top material s15 and the bottom material s17 are the withdrawal ports for light components and heavy components, respectively. 131.4 kg / h of ethylene carbonate product s16 is withdrawn from the side line.

[0110] In this embodiment, the yield of ethylene carbonate is 96.5%, and the purity of the ethylene carbonate product is greater than 99.99 wt %. The key logistics and composition calculation results of this embodiment are shown in Table 1.

[0111] Table 1

[0112] Example 6

[0113] This embodiment provides a method for preparing cyclic carbonate by cyclic esterification of diols. The method is carried out using the apparatus system for preparing cyclic carbonate by cyclic esterification of diols described in Example 2. The method specifically comprises the following steps:

[0114] (1) Cyanopyrazine is used as an auxiliary agent, the flow rate of the reaction raw material ethylene glycol feed s1 is 96 kg / h, the flow rate of CO2 (s3) feed is 65.9 kg / h, the operating pressure of the bubbling bed reactor is 800 kPa, and heat transfer oil is introduced into the heating jacket to maintain the reaction temperature at 130°C. The molar ratio of ethylene glycol to cyanopyrazine and CO2 in the bubbling bed reactor is controlled to be 1:5 and 1:1.5 respectively. By continuously adding a homogeneous catalyst tin bromide / trialkylethylphosphonium bromide composite catalyst, CO2 and ethylene glycol are continuously converted to prepare ethylene carbonate. The ethylene carbonate solution containing 6.3% CO2 is extracted from the reactor outlet s5 and enters the first separation tank 2A ​​for gas-liquid separation. The pressure of the first separation tank 2A ​​is controlled to 800 kPa. 96% CO2 (s6) is extracted from the top of the first separation tank and returned to the reactor through a compressor 6 to continue participating in the reaction. The total gas feed entering the reactor is s4. The pressure of the second separation tank 2B is controlled to be 100 kPa, and the liquid phase is extracted from the liquid outlet at the bottom of the first separation tank 2A ​​and enters the second separation tank 2B to continue separating the residual gas phase components;

[0115] (2) the liquid phase extracted from the second separation tank 2B in step (1) is fed into a light-removal column 3 for separation, wherein the feed s8 contains 5.8% ethylene carbonate and 78.5% cyanopyrazine, the tower top operating pressure is controlled to be 4 kPa, the tower top temperature is 118° C., the theoretical number of plates is set to 21, the feed position is the 9th plate, the gas phase extracted from the tower top is condensed, 70% of the material s7 is pressurized by a mechanical pump 7 (s9) and circulated back to the reactor, the total liquid feed entering the reactor is s2, and 30% of the material is refluxed to the top of the light-removal column 3 after passing through a pressure reducing valve;

[0116] (3) The ethylene carbonate solution s10 extracted from the bottom of the light-removal tower 3 enters the de-weighting tower 4, the tower top operating pressure is controlled to be 2 kPa, the theoretical number of tower plates is 18, and the feed position is the 13th tower plate. The 99% ethylene carbonate solution s11 extracted from the top of the de-weighting tower is pressurized by the mechanical pump 8 (s12) and circulated back to the light-removal tower. The 96.3% heavy component s13 extracted from the bottom of the de-weighting tower 4 is sent to the auxiliary agent regeneration unit. The purity of the ethylene carbonate solution s14 extracted from the side line reaches 99.9%.

[0117] (4) The ethylene carbonate material s14 withdrawn from the side line of the deweighting tower 4 is sent to the high-purity tower 5 for further refining. The operating pressure at the top of the high-purity tower 5 is controlled to be 3 kPa, the number of theoretical plates is 25, the feed position is the 20th plate, the top material s15 and the bottom material s17 are the withdrawal ports for the light component and the heavy component, respectively. 129.5 kg / h of ethylene carbonate product s16 is withdrawn from the side line of the high-purity tower 5.

[0118] In this embodiment, the yield of ethylene carbonate is 95%, and the purity of the ethylene carbonate product is 99.99 wt %. The key logistics and composition calculation results of this embodiment are shown in Table 2.

[0119] Table 2

[0120] Example 7

[0121] This embodiment provides a method for preparing cyclic carbonate by cyclic esterification of diols. The method is carried out using the apparatus system for preparing cyclic carbonate by cyclic esterification of diols described in Example 3. The method specifically comprises the following steps:

[0122] (1) Cyanopyrimidine was used as a reaction aid, the feed rate of the reaction raw material ethylene glycol s1 was controlled to 144 kg / h, and the feed rate of CO2 (s3) was controlled to 97.2 kg / h. Inert metal fillers were filled in the tubes of the fixed-bed tubular reactor to enhance gas-liquid distribution and heat transfer. The operating pressure of the reactor was controlled to 1500 kPa. The reactor temperature was maintained at 100°C using medium-pressure hot water in the reactor shell. The molar ratios of cyanopyrimidine and CO2 to ethylene glycol were controlled to be 5:1 and 1.5:1, respectively. By continuously adding a homogeneous catalyst zinc bromide / tetrabutylphosphine bromide composite catalyst, CO2 and ethylene glycol were continuously converted to produce ethylene carbonate. From the reactor outlet, s5 of ethylene carbonate solution containing 7.4% CO2 is drawn into the first separator 2A for gas-liquid separation. The pressure of the first separator 2A is controlled at 1500 kPa. 96% of the CO2 (s6) is drawn from the top of the first separator and returned to the reactor via compressor 6 to continue the reaction. The total gas feed entering the reactor is s4. The pressure of the second separator 2B is controlled at 200 kPa. The liquid phase is drawn from the bottom outlet of the first separator 2A and enters the second separator 2B for further separation of the remaining gaseous components.

[0123] (2) the liquid phase extracted from the second separation tank 2B in step (1) is fed into a lightness removal column 3 for separation, wherein the feed s8 contains 6.6% ethylene carbonate and 78.8% cyanopyrimidine, the operating pressure at the top of the lightness removal column 3 is controlled to be 8 kPa, the number of theoretical plates is 21, and the feed position is the 9th plate. The gas phase extracted from the top of the column is condensed, 50% of the material s7 is pressurized by a mechanical pump 7 (s9) and circulated back to the reactor. The total liquid feed entering the reactor is s2, and 50% of the material is refluxed to the top of the lightness removal column 3 after passing through a pressure reducing valve;

[0124] (3) The ethylene carbonate solution s10 extracted from the bottom of the light-removal tower 3 enters the de-weighting tower 4, and the operating pressure at the top of the de-weighting tower 4 is controlled to be 2 kPa, the theoretical number of plates is 18, and the feed position is the 13th plate. The 99.5% ethylene carbonate solution s11 extracted from the top of the de-weighting tower is pressurized by the mechanical pump 8 (s12) and circulated back to the light-removal tower. The 95.5% heavy component s13 extracted from the bottom of the de-weighting tower 4 is sent to the auxiliary agent regeneration unit, and the 99.5% ethylene carbonate is extracted from the side liquid outlet s14.

[0125] (4) The ethylene carbonate solution s14 taken out from the side liquid outlet of the deweighting tower 4 enters the high-purity tower 5 for further refining and separation. The operating pressure at the top of the high-purity tower 5 is controlled to be 3 kPa, the theoretical number of tower plates is 25, the feed position is the 20th tower plate, the top material s15 and the bottom material s17 are the withdrawal ports for the light component and the heavy component, respectively. 192 kg / h of ethylene carbonate product s16 is taken out from the side line of the high-purity tower 5.

[0126] In this embodiment, the yield of ethylene carbonate is 94%, and the purity of the ethylene carbonate product is 99.99 wt %. The key logistics and composition calculation results of this embodiment are shown in Table 3.

[0127] Table 3

[0128] Example 8

[0129] This embodiment provides a method for preparing cyclic carbonate by cyclic esterification of diols. The method is carried out using the apparatus system for preparing cyclic carbonate by cyclic esterification of diols described in Example 4. The method specifically comprises the following steps:

[0130] (1) Cyanopyridine was used as a reaction aid, the feed rate of the reaction raw material 1,2-propylene glycol s1 was controlled to 96 kg / h, a heterogeneous catalyst ZnO particles were filled in the fluidized bed reactor, the reactor pressure was controlled to 1500 kPa by the CO2 (s3) inlet flow rate, low-pressure steam was introduced into the jacket to maintain the reaction temperature at 180°C, and the molar ratios of cyanopyridine, CO2 and 1,2-propylene glycol in the reactor were controlled to be 5:1 and 1.5:1 respectively by the feed rate. A propylene carbonate solution containing 18.1% CO2 s5 was extracted from the reactor outlet and entered the first separation tank 2A ​​for gas-liquid separation. The pressure of the first separation tank 2B was controlled to 800 kPa. 80.6% CO2 (s6) was extracted from the top of the first separation tank 2A ​​and returned to the reactor through compressor 6 to continue participating in the reaction. The total gas feed entering the reactor was s4. The pressure of the second separation tank 2B is controlled to be 100 kPa, and the liquid phase is extracted from the liquid outlet at the bottom of the first separation tank 2A ​​and enters the second separation tank 2B to continue separating the residual gas phase components;

[0131] (2) The liquid phase extracted from the second separation tank 2B in step (1) is fed into the de-lightness column 3 for separation, wherein the feed s8 contains 14.5% propylene carbonate and 59.8% cyanopyridine. The operating pressure at the top of the de-lightness column 3 is controlled to be 4 kPa, the top temperature is 123°C, the theoretical number of plates is 60, and the feed position is the 6th plate. The gas phase extracted from the top of the tower is condensed, and 575 kg / h of cyanopyridine material s7 is pressurized by a mechanical pump 7 (s9) and circulated back to the reactor. The total liquid feed entering the reactor is s2. 303 kg / h of propylene carbonate, by-product amide heavy components, and a small amount of residual cyanopyridine mixed solution s10 are extracted from the liquid outlet of the de-lightness column 3 and sent to the de-lightness column 4 for further separation;

[0132] (3) The propylene carbonate solution s10 extracted from the bottom of the light removal column 3 enters the de-weighting column 4. The operating pressure at the top of the de-weighting column 4 is controlled to be 2 kPa, the number of theoretical plates is 20, and the feed position is the 15th plate. 137 kg / h of amide heavy components s13 are extracted from the bottom of the de-weighting column 4 and sent to the auxiliary agent regeneration unit. 159.1 kg / h of propylene carbonate containing 86% is extracted from the top of the de-weighting column 4. The s12 is then successively fed into the crystallizer 9 and the high-purity column 5 for further separation and purification.

[0133] (4) The material s12 taken out from the top of the de-weighting tower 4 is separated from the residual cyanopyridine and the product propylene carbonate by cooling crystallization in the crystallizer 9, wherein the mother liquor s15 (23 kg / h) of the crystallizer 9 is taken out from the mother liquor outlet and sent to the de-weighting tower 3 for further separation and purification, and the crystal liquid s16 (136 kg / h) is sent to the high-purity tower 5 for further purification and purification through the crystal liquid outlet s16; the operating pressure of the top of the high-purity tower 5 is controlled to be 2 kPa, the theoretical number of tower plates is 25, the feed position is the third tower plate, 126 kg / h of propylene carbonate product solution s17 is taken out from the top of the tower, and the solution containing a small amount of heavy components s18 is taken out from the bottom of the tower and returned to the de-weighting tower 4 for further separation after being pressurized.

[0134] In this embodiment, the yield of propylene carbonate is 97.9%, and the purity of the propylene carbonate product is 99.94 wt %. The key logistics and composition calculation results of this embodiment are shown in Table 4.

[0135] Table 4

[0136] In summary, the device system for preparing cyclic carbonates by diol cyclic esterification provided in the present application utilizes CO2 and diol compounds as raw materials and nitrile compounds as auxiliary agents to produce high-value new energy solvent products, cyclic carbonates, which is in line with the concept of green, environmental protection and low-carbon development. At the same time, it avoids the use of flammable and explosive and other hazardous epoxides as reaction raw materials, thereby improving the safety of the cyclic carbonate production process; and utilizes the gas-liquid separation unit and the refining unit to recycle the separated CO2 and nitrile compounds, greatly improving the raw material conversion rate, thereby improving the production efficiency and economy of the process, and has prospects for large-scale promotion and application.

[0137] The applicant declares that while the above-mentioned embodiments are used to illustrate the detailed structural features of the present application, the present application is not limited to the above-mentioned detailed structural features, which does not mean that the present application must rely on the above-mentioned detailed structural features in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for selected components, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

[0138] The preferred embodiments of the present application are described in detail above. However, the present application is not limited to the specific details of the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the scope of protection of the present application.

[0139] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0140] In addition, the various implementation methods of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. An apparatus system for preparing cyclic carbonates by cyclic esterification of diols, characterized in that, the apparatus system includes a reaction unit, a gas-liquid separation unit and a refining unit connected in sequence; In the reaction unit, a nitrile compound is used as an auxiliary agent to realize the cyclic esterification of diol and CO 2 to synthesize cyclic carbonate; the reaction unit includes any one of a fixed bed reactor, a bubble bed reactor or a fluidized bed reactor; the liquid feeding and discharging mode of the reaction unit includes upward liquid feeding and downward liquid discharging or downward liquid feeding and upward liquid discharging; the gas-liquid separation unit includes a first separation device and a second separation device arranged in series; the refining unit includes a light component removal tower, a heavy component removal tower and a high-purity tower connected in sequence.

2. The apparatus system according to claim 1, wherein, the reaction unit includes any one of a jacket heat exchanger, a shell-and-tube heat exchanger or an internal heat exchanger.

3. The apparatus system according to claim 1, wherein, when the reaction unit is a fixed-bed reactor, an upward feed and downward discharge feeding method is adopted.

4. The apparatus system according to claim 1, wherein, when the reaction unit is a bubble-bed reactor, a downward feed and upward discharge feeding method is adopted.

5. The apparatus system according to claim 1, wherein, when the reaction unit is a fluidized-bed reactor, a downward feed and upward discharge feeding method is adopted.

6. The apparatus system according to claim 1, wherein, the gas outlet of the first separation device is connected to the gas inlet of the reaction unit through a compression device.

7. The apparatus system according to claim 1, wherein, the liquid outlet of the light component removal tower is connected to the liquid inlet of the reaction unit.

8. The apparatus system according to claim 1, wherein, the heavy component removal tower is connected to the lower part of the light component removal tower.

9. The apparatus system according to claim 1, wherein, the refining unit further includes a crystallization device.

10. The apparatus system according to claim 9, wherein, the crystallization device is arranged between the heavy component removal tower and the high-purity tower; Optionally, the crystallization device includes an evaporation crystallizer or a cooling crystallizer.

11. The apparatus system according to claim 9 or 10, wherein, the high-purity tower is connected to the heavy component removal tower.

12. A method for preparing cyclic carbonates by cyclic esterification of diols, wherein, the method is carried out by using the apparatus system for preparing cyclic carbonates by cyclic esterification of diols according to any one of claims 1 to 11; The method includes using nitrile compounds as additives to achieve the cyclic esterification of diols and synthesize cyclic carbonates. The specific reaction process is as follows: wherein the diol includes vicinal diol; In the molecular structure of the diol, R 1 and R 2 groups include any one of a hydrogen group, a methyl group, an ethyl group, or a propyl group; In the molecular structure of the nitrile compound, R 3 group includes any one of ethyl, benzyl, pyridine, pyrimidine, pyrazine, imidazole or quinoline.

13. The method according to claim 12, wherein, the method includes the following steps: (a) CO 2 The gas is introduced from the gas inlet of the reaction unit, and the mixed solution of diol and nitrile compound enters from the liquid inlet of the reaction unit. Under the action of the catalyst in the reaction unit, the ring esterification of diol and CO 2 occurs to generate cyclic carbonate; (b) The reaction materials taken out from the reaction unit in step (a) are successively fed into a first separation device and a second separation device for gas-liquid separation. The gas phase is taken out from the gas outlet of the first separation device and fed into the gas inlet of the reaction unit; the liquid phase is taken out from the liquid outlet of the second separation device and fed into the refining unit for refining; (c) The solution taken out from the liquid outlet of the second separation device in step (b) passes through the light component removal tower, and the light components are taken out from the top liquid outlet of the light component removal tower and recycled to the reaction unit in step (a) for continuous reaction; (d) The cyclic carbonate solution taken out from the bottom liquid outlet of the light component removal tower in step (c) enters the heavy component removal tower for removal of heavy components. The solution taken out from the top liquid outlet of the heavy component removal tower is taken out or recycled to the lower liquid inlet of the light component removal tower for continuous light component separation. The liquid phase taken out from the heavy component removal tower enters the high-purity tower for separation and purification and then is taken out.

14. The method according to claim 13, wherein, the reaction unit is filled with a heterogeneous catalyst and / or a homogeneous catalyst; Optionally, the heterogeneous catalyst includes any one or a combination of at least two of silica, alumina, iron oxide, copper oxide, zinc oxide, tin oxide, lanthanum oxide, cerium oxide, cobalt oxide, dialkyl zinc oxide, dialkyl tin oxide, dialkyl lanthanum oxide, dialkyl cerium oxide, or dialkyl cobalt oxide; Optionally, the shape of the heterogeneous catalyst includes any one or a combination of at least two of powder, granular, spherical, rod-shaped, cubic, or polyhedral; Optionally, the homogeneous catalyst includes any one or a combination of at least two of zinc bromide, tin bromide, cerium bromide, tetraalkyl phosphonium bromide, trialkyl ethyl phosphonium bromide, tetraphenyl phosphonium bromide, triphenyl butyl phosphonium bromide, zinc acetate, tin acetate, or cerium acetate; Optionally, the nitrile compound includes any one or a combination of at least two of acetonitrile, cyanoquinoline, cyanopyridine, cyanopyrazine, phenylacetonitrile, cyanopyrimidine, or 1H-imidazole-4-carbonitrile.

15. The method according to claim 13, wherein, the molar ratio of the diol to the nitrile compound in step (a) is 1∶(1 to 20); Optionally, the molar feed ratio of the diol described in step (a) to CO 2 is 1:(1 - 10); Optionally, the temperature of the reaction unit in step (a) is 50 to 200 °C, and the pressure is 100 to 1500 kPa; Optionally, the pressure of the first separation device in the gas-liquid separation unit in step (b) is 100 to 1500 kPa; Optionally, the pressure of the second separation device in step (b) is 100 to 600 kPa; Optionally, the operating pressure of the light component removal column in step (c) is 2 to 100 kPa; Optionally, the operating pressure of the heavy component removal column in step (c) is 2 to 100 kPa; Optionally, the operating pressure of the high-purity column in step (c) is 2 to 100 kPa; Optionally, the liquid phase drawn from the heavy component removal column in step (d) first enters the crystallization device and then enters the high-purity column for separation and purification.

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