Synthesis method and synthesis device of cyclic carbonate

Abstract

The invention provides a synthesis method and a synthesis device of cyclic carbonate. The synthesis device comprises a first reactor, an external circulation cooler, a circulation pump and a second reactor, and the first reactor and / or the second reactor are / is filled with a heterogeneous catalyst with the height larger than or equal to 2 m. According to the synthesis method, a reactor with a large height-diameter ratio is selected, the reactor is filled with a heterogeneous catalyst with the height larger than or equal to 2 m, and the temperature in the reactor is controlled to be stabilized in a low range, so that the concentration of the catalyst in a reaction product and the chromaticity of the product are reduced; the purity of the cyclic carbonate in the reaction product and the quality of the product are improved. When the synthesis device and / or the synthesis method are / is applied to synthesis of cyclic carbonate, a product containing cyclic carbonate with high purity and low chroma can be obtained, and the method is simple and convenient to operate and has industrial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a synthesis method and a synthesis device of cyclic carbonate. Background Art

[0002] Carbonate compounds can be divided into cyclic carbonates (ethylene carbonate EC, propylene carbonate PC, butylene carbonate BC) and chain carbonates (dimethyl carbonate DMC, diethyl carbonate DEC and ethyl methyl carbonate EMC) according to their structures. Cyclic carbonates are generally prepared by the cycloaddition reaction of carbon dioxide and alkylene oxides, and are one of the few ways to fix carbon dioxide that have been industrially applied. 2 Among chemical fixed chemical products, cyclic carbonates have high boiling points, high polarity, stable properties, safety and non-toxicity, and are therefore widely used, such as monomers for the synthesis of polycarbonate or other polymers, intermediates for fine chemical products, polar aprotic solvents, and lithium-ion battery electrolytes. 2 The synthesis of cyclic carbonates as raw materials is a way to achieve CO 2 One of the most promising ways of resource utilization in industrial applications.

[0003] At present, the industrialized or nearly industrialized catalysts used in the process of synthesizing cyclic carbonates from carbon dioxide and alkylene oxide can be divided into four generations: the first generation, quaternary ammonium salt catalysts, such as tetraethylammonium bromide; the second generation, KI / polymer catalysts; the third generation, quaternary phosphonium salt catalysts; the first three generations are homogeneous catalysts, and the fourth generation is a heterogeneous catalyst developed by Sinopec and its Shanghai Petrochemical Research Institute. Compared with the first three generations, the advantage of the fourth generation catalyst is that the reaction product and the catalyst are easy to separate, and the reaction raw materials carbon dioxide and alkylene oxide react in a close stoichiometric ratio, that is, a large amount of carbon dioxide gas circulation is not required during the reaction process, which effectively saves equipment investment and reduces energy consumption. Once the fourth generation catalyst is developed and put into production, the process research on the use of heterogeneous catalysts to make carbon dioxide and alkylene oxide react heterogeneously to synthesize cyclic carbonates has also been carried out one after another. For example, the existing literature also discloses some methods and applicable equipment for synthesizing cyclic carbonates using carbon dioxide and alkylene oxide as raw materials and using heterogeneous catalysts to catalyze the synthesis of cyclic carbonates.

[0004] CN111087378A discloses a method for preparing ethylene carbonate, which comprises: 2The gas enters the tube-type fixed bed reactor, and ethylene oxide is fed into the tube-type fixed bed reactor to react and obtain ethylene carbonate. The method is carried out in a tube-type reactor, achieving uniform distribution of gas and liquid in each tube, eliminating the dead zone and retention layer of ethylene oxide in the liquid cavity, and avoiding the hidden danger of explosion caused by self-polymerization of ethylene oxide; it solves the engineering design problems of uneven gas-liquid-solid distribution, local flow stagnation, slow heat transfer, and low reaction efficiency in the carbonylation reaction in the preparation of ethylene carbonate. By using a solid-supported catalyst, the catalyst will not be taken out by the reaction product, avoiding the process of separating the traditional homogeneous catalyst from the product ethylene carbonate, reducing the process energy consumption, and simplifying the process flow. The method uses an organic polymer-supported ionic liquid catalyst, the reaction temperature is 40-70°C, and the reaction heat is removed by tube-type heat removal.

[0005] CN106414422A discloses a continuous manufacturing device and manufacturing method of cyclic carbonate, the manufacturing device of cyclic carbonate of the invention comprises: an adiabatic reactor, filled with a heterogeneous catalyst for reacting epoxide with carbon dioxide; a circulation path, returning at least a part of the liquid mixed fluid flowing out of the outlet of the reactor to the reactor; a carbon dioxide supply mechanism, continuously supplying liquid or supercritical carbon dioxide into the circulation path; and an epoxide supply mechanism, continuously supplying liquid or solution epoxide into the circulation path. The method adopts liquid and supercritical CO 2 raw material.

[0006] However, although the prior art discloses some methods for synthesizing cyclic carbonates using heterogeneous catalysts, the currently disclosed methods still have problems such as high chroma, many impurities, and low purity of the reaction products. Summary of the invention

[0007] In view of the shortcomings of the prior art, the object of the present invention is to provide a method and a device for synthesizing a cyclic carbonate, which reduces the concentration of the catalyst in the reaction product and the chromaticity of the product, thereby improving the purity of the cyclic carbonate in the reaction product and the quality of the product by selecting a reactor with a larger height-to-diameter ratio, loading a heterogeneous catalyst with a height of ≥2m in the reactor, and controlling the temperature in the reactor to be stable in a lower range.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a method for synthesizing a cyclic carbonate, the method comprising synthesizing the cyclic carbonate using alkylene oxide and carbon dioxide as raw materials, using a heterogeneous catalyst during the synthesis process and controlling the catalyst concentration in the reaction product at the outlet of the reactor for synthesizing the cyclic carbonate to be ≤0.01wt%.

[0010] In some embodiments of the present invention, the heterogeneous catalyst is a resin catalyst, and the resin catalyst is preferably a resin catalyst researched and produced by China Petroleum and Chemical Corporation or Shanghai Petrochemical Research Institute of China Petroleum and Chemical Corporation, such as the resin catalysts described in patent applications CN114433229A, WO2021057835A1, CN112619705A, CN109575162A, CN109575292A, CN109569717A, and CN109590029A.

[0011] In some embodiments of the present invention, the catalyst concentration in the reaction product at the outlet of the reactor for synthesizing cyclic carbonate is controlled to be ≤0.005wt%, preferably ≤0.003wt%, more preferably ≤0.002wt%, and most preferably ≤0.001wt%.

[0012] In some embodiments of the present invention, a mesh structure for intercepting a catalyst is provided at the front end of the reactor outlet for synthesizing cyclic carbonate, the mesh of the mesh structure being smaller than the particle size of the heterogeneous catalyst, such as the particle size of the heterogeneous catalyst being 0.2-1 mm, and the mesh size of the mesh structure being selected from 50-80 meshes. Preferably, the mesh of the mesh structure is truncated cone-shaped or quadrangular cone-shaped, the mesh surface with small meshes faces the side with high catalyst concentration in the reactor, and the mesh on the mesh surface with small meshes is smaller than the particle size of the heterogeneous catalyst.

[0013] In some embodiments of the present invention, the mesh area of ​​the mesh surface with large meshes of the mesh structure is 1.1-2.5 times the mesh area of ​​the mesh surface with small meshes.

[0014] In some embodiments of the present invention, the truncated cone shape includes a regular or irregular truncated cone.

[0015] In some embodiments of the present invention, the tetrahedral pyramid shape includes a regular or irregular tetrahedral pyramid.

[0016] In some embodiments of the present invention, the mesh structure is composed of transverse ribs and longitudinal ribs, wherein the longitudinal ribs are rectangular strips and the transverse ribs are triangular prism strips. Preferably, the width of the cross section where the longitudinal ribs connect to the transverse ribs is 0.1-10 mm, preferably 1-5 mm; the gap between adjacent longitudinal ribs is 1-100 mm, preferably 10-50 mm; the width of the cross section where the transverse ribs connect to the longitudinal ribs is 0.1-10 mm, preferably 0.5-5 mm; the gap between adjacent transverse ribs is 0.1-2 mm, preferably 0.1-0.5 mm.

[0017] In some embodiments of the present invention, the thickness of the longitudinal ribs is not greater than 2 mm, preferably 0.1-2 mm, more preferably 0.5-1.5 mm. The thickness of the mesh structure is 0.5-15 mm, preferably 1-10 mm, more preferably 2-8 mm.

[0018] In some embodiments of the present invention, the filling height of the heterogeneous catalyst in the reactor for synthesizing cyclic carbonate is ≥2 m, preferably ≥3 m.

[0019] In some embodiments of the present invention, the reactor for synthesizing cyclic carbonate has a height-to-diameter ratio of 3-10, preferably 5-8.

[0020] In some embodiments of the present invention, the reactor for synthesizing cyclic carbonate adopts external circulation to remove heat, and the circulation ratio is 5-40.

[0021] In some embodiments of the present invention, the reactor for synthesizing cyclic carbonate comprises two reactors connected in series, and alkylene oxide and carbon dioxide are introduced only into the first reactor; both reactors are filled with heterogeneous catalysts, and the catalyst concentration in the reaction product at the outlet of the second reactor is controlled to be ≤0.01wt%. Preferably, the filling height of the heterogeneous catalyst in the second reactor is ≥2m.

[0022] In some embodiments of the present invention, the feed flow ratio of alkylene oxide to carbon dioxide is 1:(1.05-2).

[0023] In some embodiments of the present invention, the concentration of the cyclic carbonate in the reaction product is ≥ 99 wt %; preferably, the concentration of the cyclic carbonate in the reaction product is ≥ 99.9 wt %.

[0024] In some embodiments of the present invention, the reaction bed temperature in the reactor for synthesizing cyclic carbonate is ≤120°C, preferably, the reaction bed temperature is 90-120°C, more preferably, the reaction bed temperature is 95°C-115°C, such as the reaction bed temperature may be 95°C, 100°C, 105°C, 110°C or 115°C.

[0025] In some embodiments of the present invention, the chromaticity of the reaction product is ≤10, more preferably, the chromaticity of the reaction product is ≤8.

[0026] In some embodiments of the present invention, the method further comprises decolorizing the synthesized cyclic carbonate using an adsorbent, which is preferably a resin adsorbent and / or a molecular sieve adsorbent.

[0027] Preferably, the adsorbent is one or more of a composite carboxy imidazole resin, a halogen-type composite hydroxy imidazole resin, a porous alumina molecular sieve adsorbent, and a 5A molecular sieve adsorbent.

[0028] In some embodiments of the present invention, the reactor for synthesizing cyclic carbonate is a bubbling bed, a fixed bed or a combination thereof.

[0029] According to the synthesis method provided by the present invention, the method comprises synthesizing ethylene carbonate with liquid ethylene oxide and gaseous carbon dioxide as raw materials or synthesizing propylene carbonate with liquid propylene oxide and gaseous carbon dioxide as raw materials.

[0030] In some embodiments of the present invention, the impurities contained in the synthetic product of the reactor for synthesizing cyclic carbonates include ethylene glycol, diethylene glycol, and triethylene glycol, but do not contain quaternary ammonium salts, quaternary phosphonium salts, I - Br - , Cl- and other metal impurities.

[0031] In a second aspect, the present invention provides a synthesis device for cyclic carbonate, comprising a first reactor, an external circulation cooler, a circulation pump, and a second reactor, wherein the first reactor is provided with a feed port for alkylene oxide, a feed port for carbon dioxide, and a discharge port, wherein the discharge port on the first reactor is connected to the material inlet of the external circulation cooler, the material outlet of the external circulation cooler is connected to the inlet of the circulation pump, and the outlet of the circulation pump is simultaneously connected to the feed port for alkylene oxide on the first reactor and the feed port of the second reactor.

[0032] According to the synthesis device provided by the present invention, the feed inlet of alkylene oxide is arranged in the upper section of the first reactor, and the feed inlet of carbon dioxide is arranged in the lower section of the first reactor.

[0033] According to the synthesis device provided by the present invention, the first reactor is filled with a heterogeneous catalyst with a height of ≥2m.

[0034] In some embodiments of the present invention, the first reactor has a height-to-diameter ratio of 3-10, preferably 5-8.

[0035] In some embodiments of the present invention, the height of the straight section of the first reactor is ≥3 m.

[0036] In some embodiments of the present invention, the feed opening of the alkylene oxide is higher than the filling height of the heterogeneous catalyst.

[0037] In some embodiments of the present invention, the feed inlet of carbon dioxide is lower than the filling section of the heterogeneous catalyst.

[0038] In some embodiments of the present invention, a liquid distributor is provided near the feed port of the alkylene oxide in the first reactor to evenly distribute the alkylene oxide so that the alkylene oxide can contact the heterogeneous catalyst and carbon dioxide more fully. Preferably, the liquid distributor is above the filling section of the heterogeneous catalyst, and the material coming from the feed port of the alkylene oxide is evenly distributed to the filling section of the heterogeneous catalyst through the liquid distributor.

[0039] In some embodiments of the present invention, a gas exhaust hole is further provided at the top of the first reactor for exhausting the non-condensable gas of the first reactor.

[0040] According to the synthesis device provided by the present invention, the second reactor is filled with a heterogeneous catalyst with a height of ≥2m.

[0041] In some embodiments of the present invention, the second reactor has a height-to-diameter ratio of 3-10, preferably 5-8.

[0042] In some embodiments of the present invention, the height of the straight section of the second reactor is ≥3 m.

[0043] In some embodiments of the present invention, a mesh structure for intercepting the catalyst is provided at the front end of the discharge port of the second reactor, and the mesh holes of the mesh structure are smaller than the particle size of the heterogeneous catalyst; preferably, the mesh holes of the mesh structure are truncated cone-shaped or quadrangular cone-shaped, with the side with small mesh holes facing the side with high catalyst concentration in the reactor, and the mesh holes on the side with small mesh holes are smaller than the particle size of the heterogeneous catalyst.

[0044] In some embodiments of the present invention, the mesh area of ​​the mesh surface with large meshes of the mesh structure is 1.1-2.5 times the mesh area of ​​the mesh surface with small meshes.

[0045] In some embodiments of the present invention, the mesh structure is composed of transverse ribs and longitudinal ribs, wherein the longitudinal ribs are rectangular strips and the transverse ribs are triangular prism strips. Preferably, the width of the cross section where the longitudinal ribs connect to the transverse ribs is 0.1-10 mm, preferably 1-5 mm; the gap between adjacent longitudinal ribs is 1-100 mm, preferably 10-50 mm; the width of the cross section where the transverse ribs connect to the longitudinal ribs is 0.1-10 mm, preferably 0.5-5 mm; the gap between adjacent transverse ribs is 0.1-2 mm, preferably 0.1-0.5 mm.

[0046] In some embodiments of the present invention, the thickness of the longitudinal ribs is not greater than 2 mm, preferably 0.1-2 mm, more preferably 0.5-1.5 mm. The thickness of the mesh structure is 0.5-15 mm, preferably 1-10 mm, more preferably 2-8 mm.

[0047] In some embodiments of the present invention, the above mesh structure for intercepting the catalyst is also provided at the front end of the discharge port of the first reactor.

[0048] In some embodiments of the present invention, when the mesh structure meets the load-bearing standard requirements, the mesh structure can be directly used as a supporting structure for loading a heterogeneous catalyst in a reactor.

[0049] In some embodiments of the present invention, the apparatus for synthesizing cyclic carbonate further comprises an adsorption device connected to the discharge port of the second reactor.

[0050] In some embodiments of the present invention, the adsorbent filled in the adsorption device is preferably a resin adsorbent and / or a molecular sieve adsorbent.

[0051] Preferably, the adsorbent is one or more of a composite carboxy imidazole resin, a halogen-type composite hydroxy imidazole resin, a porous alumina molecular sieve adsorbent, and a 5A molecular sieve adsorbent.

[0052] In a third aspect, the present invention provides an application of the synthesis device described in the second aspect and / or the method described in the first aspect in synthesizing cyclic carbonates, wherein the cyclic carbonates include ethylene carbonate and propylene carbonate.

[0053] The process of synthesizing cyclic carbonate using the synthesis device of the second aspect according to the method of the first aspect is as follows: liquid alkylene oxide enters from the alkylene oxide feed port of the first reactor, is evenly distributed by the liquid distributor, and then contacts and reacts with the carbon dioxide gas entering from the carbon dioxide feed port of the first reactor to synthesize cyclic carbonate under the catalytic action of the heterogeneous catalyst; the product of the first reactor exits from the discharge port of the first reactor and enters the external circulation cooler to exchange heat with the refrigerant; a part of the material coming out of the external circulation cooler is sent to the alkylene oxide feed port of the first reactor through a circulation pump and enters the first reactor together with the alkylene oxide, and the other part is sent to the second reactor through a circulation pump, and the reaction is continued in the second reactor. The reaction product of the second reactor can be directly used in industrial production, or can be passed into an adsorption device to further reduce the chromaticity of the product.

[0054] The beneficial effects of the present invention are as follows:

[0055] 1. The inventor of the present invention has found that, first, by strictly controlling the catalyst concentration in the reaction product at the outlet of the reactor for synthesizing cyclic carbonate during the synthesis process, the purity of the cyclic carbonate in the obtained product can be higher; second, the cyclic carbonate with lower chromaticity can be obtained by synthesizing cyclic carbonate at a lower temperature, but the lower reaction temperature is also easy to reduce the conversion rate of alkylene oxide and the purity of cyclic carbonate. Therefore, the present invention proposes, on the one hand, to catalyze the synthesis of cyclic carbonate using a heterogeneous catalyst, so that the synthesized product is more easily separated from the heterogeneous catalyst; further, by setting a mesh structure for intercepting the catalyst at the outlet of the reactor for synthesizing cyclic carbonate, the catalyst is kept in the reactor as much as possible; further, two reactors in series are used for synthesis reaction and only alkylene oxide and carbon dioxide are introduced into the first reactor, and a certain height of heterogeneous catalyst is filled in the first reactor and the second reactor, and the heterogeneous catalyst filling layer of the second reactor is used to form a filter layer to intercept the heterogeneous catalyst dust generated by the reaction in the first reactor in the second reactor, and the catalyst concentration in the reaction product at the outlet of the reactor is strictly controlled, so as to produce a product with low catalyst content and high purity of cyclic carbonate. On the other hand, the present invention produces a product with a chromaticity lower than 10 by controlling the reaction bed temperature in the reactor for synthesizing cyclic carbonate to be ≤120°C, so as to meet the demand for low-chromaticity cyclic carbonate in industrial production.

[0056] 2. The present invention also proposes to produce a product with high purity and low chromaticity of cyclic carbonate by increasing the filling height of heterogeneous catalyst in the reactor, because when the filling height of heterogeneous catalyst in the reactor is high, the contact time of alkylene oxide with carbon dioxide and heterogeneous catalyst in the reactor can be extended, thereby improving the conversion rate of alkylene oxide and the purity of cyclic carbonate at the reactor outlet; at the same time, increasing the filling height of heterogeneous catalyst in the reactor is also conducive to heat dissipation and reducing the reaction temperature in the reactor, thereby reducing the chromaticity of the product. The use of a reactor with a height-to-diameter ratio of 3-10 to synthesize cyclic carbonate is convenient for loading heterogeneous catalysts, and can also reduce the amount and cost of heterogeneous catalysts while maintaining a high filling height of heterogeneous catalysts in the reactor.

[0057] 3. The present invention provides a synthesis device for cyclic carbonate, which includes two reactors arranged in series and an external circulation heat removal structure arranged between the two reactors, and the reactor is filled with a heterogeneous catalyst with a height of ≥2m. Using two reactors arranged in series and filled with a heterogeneous catalyst with a height of ≥2m for synthesis reaction, the reaction time of the raw materials in the reactor can be extended, so that the epoxy alkane reacts more fully, which is conducive to improving the purity of the cyclic carbonate in the product; the external circulation heat removal structure arranged in the middle is conducive to timely withdrawing the reaction heat in the reactor so as to stabilize the reaction temperature in the reactor and reduce the chromaticity of the product. A mesh structure for intercepting the catalyst is arranged at the discharge port of the second reactor or the second reactor and the first reactor, which can effectively intercept the heterogeneous catalyst to reduce the content of the heterogeneous catalyst in the final product and improve the purity of the cyclic carbonate in the product. In addition, in order to further obtain a product with lower chromaticity, the chromaticity can also be adsorbed by connecting an adsorption device filled with an adsorbent after the second reactor, and the adsorption effect is good, and a low-chromaticity cyclic carbonate can be quickly obtained. The whole synthesis device of the present invention has a simple structure and low manufacturing cost, and can be directly used for producing industrial-grade ethylene carbonate and propylene carbonate.

[0058] 4. The present invention proposes to use a mesh structure with a truncated cone or a quadrangular cone at the front end of the reactor outlet, with the mesh surface with small meshes facing the inside of the reactor, and the mesh on the mesh surface with small meshes is smaller than the particle size of the heterogeneous catalyst. The heterogeneous catalyst is not easily stuck in the meshes by using the mesh structure, and the number of shutdowns caused by clogging of the filter can be reduced; and the mesh structure provided by the present invention has good strength, is not easy to deform, has a long service life, and can be directly used as a support structure for loading heterogeneous catalysts in the reactor when it meets the load-bearing standard requirements.

[0059] 5. The synthesis method and synthesis device of the cyclic carbonate provided by the present invention make it possible to produce low-chroma and / or industrial-grade high-quality cyclic carbonate at a lower cost and a simpler process, and has a prospect of industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a simplified flow chart of the production process of cyclic carbonate of the present invention;

[0061] Indicated in the figure:

[0062] I is the first reactor, II is the external circulation cooler, III is the circulation pump, and IV is the second reactor;

[0063] 1 is liquid alkylene oxide, 2 is gaseous carbon dioxide, 3 is the product of the first reactor, 4 is the product of the first reactor going to the second reactor, 5 is the circulating material returned to the first reactor through the circulating pump, 6 is non-condensable gas, and 11 is the product of the second reactor.

[0064] Figure 2 These are the front view and top view of the mesh structure in the first reactor and the second reactor of the present invention. DETAILED DESCRIPTION

[0065] The following examples further illustrate the technology of the present invention. These examples are for illustration and example of the present invention and are not intended to limit the scope of the present invention in any form.

[0066] Example 1

[0067] A device for synthesizing cyclic carbonates, comprising a first reactor I, an external circulation cooler II, a circulation pump III, and a second reactor IV, such as Figure 1 The first reactor I and the second reactor IV are filled with heterogeneous catalysts.

[0068] A mesh structure for intercepting the catalyst is provided at the front end of the discharge port of the first reactor I and the second reactor IV. Since the mesh structure meets the load-bearing standard requirements, it is directly used as a support structure for loading the heterogeneous catalyst in the reactor, such as Figure 2 As shown. The mesh structure is composed of transverse ribs and longitudinal ribs, wherein the longitudinal ribs are rectangular strips, and the transverse ribs are triangular prism strips; the cross-sectional width of the longitudinal ribs connecting the transverse ribs is 2mm; the gap between adjacent longitudinal ribs is 10mm; the cross-sectional width of the transverse ribs connecting the longitudinal ribs is 5mm; the gap between adjacent transverse ribs is 0.5mm. The thickness of the longitudinal ribs is 0.5mm, and the thickness of the mesh structure is 5mm. The mesh of the mesh structure is in the shape of a quadrangular pyramid.

[0069] The first reactor 1 is provided with an alkylene oxide feed port at the top, a carbon dioxide feed port at the bottom, a vent at the top, and a discharge port at the bottom, and a liquid distributor is also provided near the alkylene oxide feed port in the first reactor 1. The alkylene oxide feed port is higher than the filling section of the heterogeneous catalyst, the carbon dioxide feed port is lower than the filling section of the heterogeneous catalyst, and the liquid distributor is above the filling section of the heterogeneous catalyst.

[0070] The material outlet of the first reactor I is connected to the material inlet of the external circulation cooler II, the material outlet of the external circulation cooler II is connected to the inlet of the circulation pump III, and the outlet of the circulation pump III is simultaneously connected to the alkylene oxide feed inlet of the first reactor and the feed inlet of the second reactor.

[0071] Example 2

[0072] A device for synthesizing cyclic carbonate comprises a first reactor I, an external circulation cooler II, a circulation pump III, a second reactor IV, and an adsorption device V. The first reactor I and the second reactor IV are filled with a heterogeneous catalyst.

[0073] A mesh structure for intercepting the catalyst is provided at the front end of the discharge port of the first reactor I and the second reactor IV. Since the mesh structure meets the requirements of the load-bearing standard, it is directly used as a support structure for loading heterogeneous catalysts in the reactor. The mesh structure is composed of transverse ribs and longitudinal ribs, wherein the longitudinal ribs are square strips, and the transverse ribs are triangular prism strips; the cross-sectional width of the longitudinal ribs connected to the transverse ribs is 2mm; the gap between adjacent longitudinal ribs is 10mm; the cross-sectional width of the transverse ribs connected to the longitudinal ribs is 5mm; the gap between adjacent transverse ribs is 0.5mm. The thickness of the longitudinal ribs is 0.5mm, and the thickness of the mesh structure is 5mm. The mesh of the mesh structure is a quadrangular pyramid.

[0074] The first reactor 1 is provided with an alkylene oxide feed port at the top, a carbon dioxide feed port at the bottom, a vent at the top, and a discharge port at the bottom, and a liquid distributor is also provided near the alkylene oxide feed port in the first reactor 1. The alkylene oxide feed port is higher than the filling section of the heterogeneous catalyst, the carbon dioxide feed port is lower than the filling section of the heterogeneous catalyst, and the liquid distributor is above the filling section of the heterogeneous catalyst.

[0075] The material outlet of the first reactor I is connected to the material inlet of the external circulation cooler II, the material outlet of the external circulation cooler II is connected to the inlet of the circulation pump III, the outlet of the circulation pump III is simultaneously connected to the alkylene oxide feed inlet of the first reactor and the feed inlet of the second reactor, and the material outlet of the second reactor IV is connected to the feed inlet of the adsorption device V.

[0076] Example 3

[0077] The process of synthesizing ethylene carbonate is as follows (using the device of Example 1):

[0078] (1) A reactor with a diameter of 1000 mm and a straight section height of 5000 mm is selected as the first reactor I and the second reactor IV, and a halogen-type composite hydroxyimidazole resin with a particle size of 0.2-1 mm is loaded into the first reactor I and the second reactor IV so that the loading height of the halogen-type composite hydroxyimidazole resin is 3000 mm.

[0079] (2) The feed rate of liquid ethylene oxide was controlled to be 500 kg / h, the feed rate of gaseous carbon dioxide was controlled to be 600 kg / h, the bed temperature of the first reactor I was controlled to be 115° C., the circulation ratio was controlled to be 13, and the bed temperature of the second reactor IV was controlled to be 115° C. The content of heterogeneous catalyst entrained in the product at the discharge port of the second reactor IV was ≤0.001 wt%, and there was substantially no catalyst entrainment (almost undetectable); the chromaticity of the product at the discharge port of the second reactor IV was 10, and the product purity was 99.93 wt%.

[0080] Example 4

[0081] The process is the same as that of Example 3, except that the bed temperature of the first reactor I is 150° C.; at this time, the chromaticity of the reactants at the discharge port of the second reactor IV is 30, and the product purity is 99.00 wt%.

[0082] Example 5

[0083] The process is the same as that of Example 3, except that the bed temperature of the first reactor I is 95° C.; at this time, the chromaticity of the product at the discharge port of the second reactor IV is 8 and the product purity is 95.00 wt%.

[0084] Example 6

[0085] The process is the same as that in Example 3, except that a reactor with a diameter of 1000 mm and a straight section height of 7500 mm is selected as the first reactor I, the height of the halogen-type composite hydroxyimidazole resin loaded in the first reactor I is 6000 mm, and the bed temperature of the first reactor I is 110°C; at this time, the chromaticity of the product at the discharge port of the second reactor IV is 8 and the product purity is 99.93wt%.

[0086] Example 7

[0087] The process is the same as that in Example 3, except that the bed temperature of the first reactor I is 110° C. and the circulation ratio is 15; at this time, the chromaticity of the product at the discharge port of the second reactor IV is 8 and the product purity is 99.50wt%.

[0088] Example 8

[0089] The process is the same as that in Example 3, except that the product of the second reactor IV is passed into the adsorption device V using the apparatus of Example 2, and the composite carboxyimidazole resin is used as an adsorbent to further reduce the chromaticity of the product of the second reactor IV; at this time, the chromaticity of the product coming out of the discharge port of the adsorption device V is 8 and the product purity is 99.95wt%.

[0090] Example 9

[0091] The process is the same as that of Example 3, except that the height of the halogen-type composite hydroxyimidazole resin loaded in the second reactor IV is 2000 mm. At this time, the content of the heterogeneous catalyst entrained in the product at the discharge port of the second reactor IV is about 0.005 wt%, the chromaticity of the product is 15, and the purity of the product is 99.20 wt%.

[0092] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation of the present invention. The embodiments describe the present invention and it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention.

Claims

1. A method for synthesizing a cyclic carbonate, characterized in that: The synthesis method comprises the following steps: synthesizing cyclic carbonate ester with alkylene oxide and carbon dioxide as raw materials; using a heterogeneous catalyst in the synthesis process and controlling the catalyst concentration in the reaction product at the outlet of the reactor for synthesizing the cyclic carbonate ester to be less than or equal to 0.01 wt %.

2. The synthesis method according to claim 1, characterized in that The heterogeneous catalyst is a resin catalyst; And / or, a mesh structure for intercepting the catalyst is provided at the front end of the outlet of the reactor for synthesizing cyclic carbonate, and the mesh holes of the mesh structure are smaller than the particle size of the heterogeneous catalyst; preferably, the mesh holes of the mesh structure are truncated cone-shaped or quadrangular cone-shaped, the mesh surface with small mesh holes faces the side with high catalyst concentration in the reactor, and the mesh holes on the mesh surface with small mesh holes are smaller than the particle size of the heterogeneous catalyst; more preferably, the mesh hole area on the mesh surface with large mesh holes of the mesh structure is 1.1-2.5 times the mesh hole area on the mesh surface with small mesh holes; further preferably, the mesh structure is composed of transverse ribs and longitudinal ribs, wherein the longitudinal ribs are square strips and the transverse ribs are triangular prism strips; and / or, the heterogeneous catalyst is filled at a height of ≥2 m, preferably ≥3 m, in a reactor for synthesizing cyclic carbonate; and / or, the reactor for synthesizing the cyclic carbonate has a height-to-diameter ratio of 3-10, preferably 5-8; And / or, the reactor for synthesizing cyclic carbonate adopts external circulation to remove heat, and the circulation ratio is 5-40; And / or, the feed flow ratio of alkylene oxide to carbon dioxide is 1:(1.05-2).

3. The synthesis method according to claim 1 or 2, characterized in that The concentration of the cyclic carbonate in the reaction product is ≥99 wt %; preferably, the concentration of the cyclic carbonate in the reaction product is ≥99.9 wt %.

4. The synthesis method according to any one of claims 1 to 3, characterized in that The reaction bed temperature in the reactor for synthesizing cyclic carbonate is ≤120°C, preferably, the reaction bed temperature is 90-120°C, more preferably, the reaction bed temperature is 95°C-115°C.

5. The synthesis method according to any one of claims 1 to 4, characterized in that The chromaticity of the reaction product is ≤10, preferably, the chromaticity of the reaction product is ≤8.

6. The synthesis method according to any one of claims 1 to 5, characterized in that The method further comprises decolorizing the synthesized cyclic carbonate by using an adsorbent.

7. The synthesis method according to claim 6, characterized in that The adsorbent is a resin adsorbent and / or a molecular sieve adsorbent; preferably, the adsorbent is one or more of a composite carboxy imidazole resin, a halogen-type composite hydroxy imidazole resin, a porous alumina molecular sieve adsorbent, and a 5A molecular sieve adsorbent.

8. A synthesis device for cyclic carbonate, characterized in that: The synthesis device comprises a first reactor, an external circulation cooler, a circulation pump and a second reactor. The first reactor is provided with an alkylene oxide feed port, a carbon dioxide feed port and a discharge port, wherein the discharge port on the first reactor is connected with the material inlet of the external circulation cooler, the material outlet of the external circulation cooler is connected with the inlet of the circulation pump, and the outlet of the circulation pump is simultaneously connected with the alkylene oxide feed port on the first reactor and the feed port of the second reactor; and a heterogeneous catalyst with a height of ≥2m is filled in the first reactor.

9. The synthesis device according to claim 8, characterized in that: A mesh structure for intercepting the catalyst is provided at the front end of the discharge port of the second reactor, and the mesh holes of the mesh structure are smaller than the particle size of the heterogeneous catalyst; preferably, the mesh holes of the mesh structure are truncated cone-shaped or quadrangular cone-shaped, the mesh surface with small mesh holes faces the side with high catalyst concentration in the reactor, and the mesh holes on the mesh surface with small mesh holes are smaller than the particle size of the heterogeneous catalyst; more preferably, the mesh hole area on the mesh surface with large mesh holes of the mesh structure is 1.1-2.5 times the area of ​​the mesh holes on the mesh surface with small mesh holes; further preferably, the mesh structure is composed of transverse ribs and longitudinal ribs, wherein the longitudinal ribs are square strips and the transverse ribs are triangular prism strips; and / or, the second reactor is filled with a heterogeneous catalyst having a height of ≥2 m; And / or, the height-to-diameter ratio of the first reactor and / or the second reactor is independently 3-10; preferably, the height-to-diameter ratio is 5-8; and / or, the height of the straight section of the first reactor and / or the second reactor is independently ≥3 m; and / or, a liquid distributor is provided near the feed port of the alkylene oxide in the first reactor; preferably, the liquid distributor is above the filling section of the heterogeneous catalyst; and / or, the feed port of the alkylene oxide is higher than the filling section of the heterogeneous catalyst; and / or, the feed port of carbon dioxide is lower than the filling section of the heterogeneous catalyst; And / or, the device for synthesizing cyclic carbonate further comprises an adsorption device connected to the discharge port of the second reactor, and preferably, the adsorbent filled in the adsorption device is a resin adsorbent and / or a molecular sieve adsorbent.

10. Use of the synthesis method according to any one of claims 1 to 7 and / or the synthesis device according to any one of claims 8 to 9 in synthesizing cyclic carbonate, preferably, the cyclic carbonate comprises ethylene carbonate or propylene carbonate.

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