System and method for producing high-purity electronic grade ethylene carbonate

Abstract

The invention provides a system and a method for producing high-purity electronic-grade carbonic ester, and the system comprises a heterogeneous reaction section, a separation section and a crystallization section along the material flow direction, the heterogeneous reaction section is used for carrying out heterogeneous reaction on ethylene oxide and carbon dioxide to prepare carbonic ester; the separation section is used for separating materials from the heterogeneous reaction section and comprises a flash evaporation unit and a rectification unit in the material flow direction, and the flash evaporation unit comprises at least one flash evaporation tank; the rectification unit comprises at least one rectification tower, and the side-draw of the rectification unit is communicated with the feed port of the crystallization section; and the crystallization section is used for crystallizing and purifying the material mainly containing carbonic ester from the separation section. According to the method, high-purity ethylene carbonate used as a power battery can be obtained from the crystallization section, and crystallization mother liquor can be selectively returned to the separation section to be concentrated. The method can effectively improve product purity, reduce product chromaticity and reduce energy consumption, and can be applied to industrial production of carbonic ester.

Description

Technical Field

[0001] The present invention relates to a system and method for producing high-purity electronic-grade ethylene carbonate, which can be applied to the industrial production of carbonates. Background Art

[0002] Ethylene carbonate is an environmentally friendly chemical raw material. Under the booming situation of the carbonate industry in China, the production technology of ethylene carbonate has been continuously innovated. However, there are many production processes for ethylene carbonate, and different production processes have different application advantages.

[0003] The phosgene synthesis method is an early method for producing ethylene carbonate. The three main raw materials are: the first is ethylene glycol, the second is pyridine, and the third is phosgene. These three materials are placed in a toluene solvent or a dichlorotoluene solvent and heated until the temperature rises to 70°C. Then, pyridine and phosgene will undergo a complexation reaction to form an ionic complex. The ionic complex continues to react with ethylene glycol to produce ethylene carbonate. Using the phosgene synthesis method for the production of ethylene carbonate has the following main drawbacks. First, in the actual reaction process, a large amount of pyridine is added. Even after the reaction is completed, a large amount of pyridine remains in the residue and must be properly treated. Hydrochloric acid is the main substance used to neutralize pyridine. Using hydrochloric acid to neutralize pyridine not only makes the production process of ethylene carbonate complicated, but its strong corrosiveness will also corrode the production equipment. Second, both phosgene and pyridine are toxic substances, and the complexation reaction must occur under sealed conditions. The product generated after the reaction contains a large amount of chlorine elements. If not properly treated, it will inevitably cause serious pollution to the surrounding ecological environment. This early production method of ethylene carbonate has been eliminated by the market.

[0004] The production of ethylene carbonate by the haloalcohol method needs to be carried out under high temperature and high pressure conditions. There are two reaction raw materials, one is sodium bicarbonate and the other is chloroethanol. The reaction solvent is acetonitrile. Using the haloalcohol method for the production of ethylene carbonate has the following main drawbacks. First, water is generated during the reaction process; second, ethylene carbonate can also undergo a decomposition reaction to produce ethylene oxide and carbon dioxide, which affects the final product yield ratio.

[0005] The urea method uses urea and ethylene glycol as raw materials and places them in a specific device to undergo catalytic alcoholysis reaction, thus generating ethylene carbonate. This is one of the most concerned methods for preparing ethylene carbonate in recent years. Compared with other methods, the application advantages of the urea alcoholysis method are mainly reflected in the following aspects. First, the reaction conditions of the urea alcoholysis method are milder. Second, urea and ethylene glycol are the two main production raw materials, belonging to bulk chemical raw materials, with a wider source, lower procurement cost, and very sufficient market supply. Finally, the application of the urea alcoholysis method has prominent economic and environmental protection characteristics.

[0006] The synthesis of ethylene carbonate by the addition method of ethylene oxide and carbon dioxide is the most common production process of ethylene carbonate at home and abroad. Ethylene oxide and carbon dioxide are the main production raw materials. It should be noted that when applying this process, not only ethylene carbonate will be generated, but also two side reactions will occur, producing a large amount of water. Therefore, it is necessary to strictly control the water content in the process system to ensure the effective generation of ethylene carbonate. In order to use this process to produce ethylene carbonate and improve the production economy of ethylene carbonate, it is necessary to upgrade and optimize the corresponding process system, and the focus of the process system optimization should be concentrated on "how to use catalysts to control the degree of side reaction occurrence". Through experiments, it is found that the use of solid catalysts has the following advantages. First, the reaction conditions have changed; second, the reaction process flow is simpler; third, the reaction selectivity and conversion rate are higher; fourth, the separation difficulty of the catalyst after the reaction is not great, and it has the characteristics of recovery and regeneration.

[0007] The domestic production capacity of electronic-grade ethylene carbonate is basically concentrated in a few enterprises such as Shandong Dongyue Dailylong New Material Co., Ltd., Dongying Haike New Materials Co., Ltd., Ouke Chemical Co., Ltd., Liaoning Ganglong New Material Co., Ltd., Yingkou Hengyang New Material Co., Ltd., and Zhongke Hongye New Material Co., Ltd. The more technically difficult electronic-grade EMC is even more concentrated in a few enterprises such as Shandong Dongyue Dailylong New Material Co., Ltd., Dongying Haike New Materials Co., Ltd., Liaoning Ganglong New Material Co., Ltd., and Liaoyang Baishida New Material Co., Ltd., with a relatively high industrial concentration. At present, the main production method of electronic-grade ethylene carbonate is obtained by using homogeneous reaction technology and rectification separation technology.

[0008] The boiling point of ethylene carbonate under atmospheric pressure is very high (up to 246 °C). Using traditional distillation methods, it must be operated under reduced pressure, which leads to problems such as unqualified product chromaticity and limited purity upper limit. Since the crystallization separation process is carried out under atmospheric pressure and low temperature conditions, the crystals have a specific crystal form, and impurities are not easily embedded inside the crystals, so that a crystal product with higher purity can be obtained, which is especially suitable for the preparation of electronic-grade high-purity chemicals. At the same time, the crystallization heat of most chemicals is only 1 / 4 to 1 / 7 of their latent heat of vaporization. Coupled with the large reflux ratio in the distillation process, therefore, using crystallization to separate and purify chemicals has obvious energy-saving advantages compared with distillation. The simple crystallization yield is low, and the intermittent sweating method is mostly used, which requires continuous switching of hot and cold media for heating and cooling, wasting a large part of the energy consumption and not being able to well reflect the energy-saving advantages of the crystallization process.

[0009] CN 111100003A discloses a crystallization purification process for high-purity ethylene carbonate, which adopts the following steps: the raw material containing ethylene carbonate enters a static crystallizer for primary static crystallization and sweating. While obtaining a high-purity ethylene carbonate crystal product, the crystallization mother liquor and sweating liquor continue to enter a static crystallizer with the same structure for secondary static crystallization and sweating. This technical solution preferably solves the technical problems of high energy consumption, low product purity, and low yield in the prior art when separating and purifying ethylene carbonate, and can be used in the industrial production of ethylene carbonate, especially ethylene carbonate for power batteries. However, it has the defect of being unsuitable for continuous production.

[0010] CN 110878078A discloses a method for preparing electronic-grade fluoroethylene carbonate by fractional crystallization, including the following steps: the crude fluoroethylene carbonate is distilled, and fluoroethylene carbonate with different purities is collected in stages; according to the different purities of fluoroethylene carbonate, fractional crystallization is carried out under different crystallization conditions to improve the utilization rate, reduce the impurity content, and improve the product purity; then distillation and material melting are carried out; finally, decolorization and dehydration are carried out to obtain electronic-grade fluoroethylene carbonate. The invention has the advantages of economy, environmental protection, and easy industrialization, and has good purification effect. The obtained product has high purity, and the chromatographic purity is not less than 99.99%, and it can be directly used as an additive for battery electrolytes. However, it has the problems of various crude product purities and long process.

[0011] CN 108440489A discloses a crystallization device for the refining and purification of ethylene carbonate, and also discloses a method for purifying ethylene carbonate using the above device, specifically including the following steps: the ethylene carbonate obtained by distillation and purification is transported to a crystallizer for crystallization in a gradually cooling manner, and then through a gradually heating melting and complete melting method, ethylene carbonate with a purity greater than 99.99% is obtained. However, it has the defect of being unsuitable for continuous production.

[0012] CN107501230A discloses a device and method for preparing electronic-grade ethylene carbonate by coupling crystallization and rectification, including a raw material storage tank, a falling film crystallizer, a rectification column, a first product tank, a transition tank and a second product tank; the raw material storage tank is communicated with the feed inlet of the falling film crystallizer, and a main discharge pipe is provided at the discharge outlet of the falling film crystallizer. The main discharge pipe is respectively communicated with the feed inlet of the falling film crystallizer, the first product tank and the transition tank; the transition tank is communicated with the rectification column, the top outlet of the rectification column is communicated with the second product tank, and the bottom outlet of the rectification column is communicated with the raw material storage tank. This invention couples the two technologies of falling film crystallization and rectification, making use of their respective advantages to achieve better separation operation. The prepared ethylene carbonate can reach the ultra-high purity electronic level. However, it has the defects of complex operation and being unsuitable for continuous production.

[0013] In summary, in the existing processes for preparing carbonates, there are problems such as the catalyst in the reaction unit being difficult to separate, low rectification efficiency and high energy consumption in the separation process, complex static crystallization operation, and being unsuitable for continuous production. The main problems to be solved are large amounts of three wastes, high energy consumption, and complex operation. Summary of the Invention

[0014] Aiming at the problems of large amounts of three wastes and high energy consumption in the existing reaction processes for preparing carbonates, the present invention provides a method and system for producing high-purity electronic-grade ethylene carbonate that can improve product purity, reduce product chromaticity, and reduce energy consumption.

[0015] The present invention first proposes to adopt heterogeneous catalysis technology, and through the combination of a reaction section, a separation section and a crystallization section, effectively solves the above problems.

[0016] According to the first aspect of the present invention, the present invention provides a system for producing high-purity electronic-grade carbonate. Along the material flow direction, the system includes: a heterogeneous reaction section, a separation section and a crystallization section;

[0017] The heterogeneous reaction section is used for the heterogeneous reaction of alkylene oxide and carbon dioxide to prepare carbonate;

[0018] The separation section is used for separating the materials from the heterogeneous reaction section. Along the material flow direction, it includes a flash unit and a rectification unit. The flash unit includes at least one flash tank; the rectification unit includes at least one rectification column, and the side stream extraction of the rectification unit is communicated with the feed inlet of the crystallization section;

[0019] The crystallization section is used for crystallizing and purifying the materials mainly containing carbonate from the separation section.

[0020] According to the second aspect of the present invention, the present invention provides a method for producing high-purity electronic-grade carbonate, and this method is carried out in the system of the present invention.

[0021] The alkylene oxide and carbon dioxide enter the reaction section for heterogeneous reaction;

[0022] The reaction products in the reaction section enter the flash unit for flashing in sequence, and the tail gas containing CO 2 is discharged. The liquid phase rich in carbonate enters the rectification unit. The light components are taken out from the top of the column, the heavy components are taken out from the bottom of the column, and the concentrated carbonate is taken out from the side line and enters the crystallization section for crystallization purification.

[0023] Currently, the mainstream method in industrial plants is as follows: the reaction is a homogeneous method, and the separation is carried out by rectification in 2 or 3 columns to obtain carbonate products. During the rectification process, due to the existence of multiple azeotropes among the impurities (carbonate, ethylene glycol, and polyethylene glycol) in the reaction products, and the boiling point of diethylene glycol is close to that of the carbonate, although products can be obtained by rectification, generally speaking, it is not economical enough. The method of the present invention has the advantage that catalyst separation is not required, thus saving the equipment for separating the catalyst and part of the energy consumption. Crystallization separation can fully utilize the different freezing points of different substances to obtain carbonate products, which is not affected by impurity azeotropes. And theoretically, the heat of crystallization is 1 / 2 - 1 / 3 of the heat of vaporization, which can effectively save the energy consumption generated during the separation process. Moreover, the present invention adopts a continuous crystallization operation mode to realize the continuity of reaction + separation, with convenient operation and low energy consumption.

[0024] In the method of the present invention, the EC concentration in the heterogeneous reaction section product is ≥ 99.5 wt% (it can reach ≥ 99.9 wt% in industrial plants), the epoxy concentration is ≤ 200 ppm. The reaction products enter the separation section, and in the separation section, the carbon dioxide dissolved in the carbonate is flashed out by pressure relief flashing in a flash tank; the liquid after flashing enters a rectification column, and the rectification column operates under high vacuum. In the rectification column, trace amounts of carbon dioxide, epoxy, and ethylene glycol are continuously taken out from the top of the column, the heavy components containing polyethylene glycol are taken out from the bottom of the column, and high-quality ethylene carbonate can be obtained from the side line and enter the crystallization unit; the crystallization unit, for example, uses a refrigerant to cool and crystallize the ethylene carbonate taken out from the side line. Utilizing the difference in melting point / freezing point, the ethylene carbonate is crystallized into a solid in the crystallizer. Since there will be impurity encapsulation and adhesion during the crystallization process, multi-stage crystallization is adopted, and the temperature is gradually increased, and the product purity is gradually improved, finally meeting the requirements of electronic-grade products and obtained through solid-liquid separation. The mother liquor of crystallization is heat-exchanged with the material entering the crystallization unit and then recycled to the rectification column for further concentration and purification.

[0025] Currently, the mainstream technology in the industry is to adopt homogeneous catalytic technology. Homogeneous means that since the catalyst is a liquid, it needs to be continuously discharged externally after separation during the reaction, so the amount of three wastes is large.

[0026] Advantages of the process flow of the present invention: (1) By adopting heterogeneous catalysis technology, the problems of difficult catalyst separation and large amounts of three wastes in the traditional process are solved; (2) By adopting continuous crystallization, the energy consumption is reduced, continuous production of the whole process is realized, and the product quality is improved.

[0027] The method of the present invention can obtain high-purity ethylene carbonate for power batteries from the crystallization section, and the crystallization mother liquor can be selectively returned to the separation section for concentration. By using this method, the product purity can be effectively improved, the product chromaticity can be reduced, the energy consumption can be reduced, and it can be applied to the industrial production of carbonates. Brief Description of the Drawings

[0028] Figure 1 It is a simplified process flow diagram of high-purity electronic-grade ethylene carbonate according to an embodiment of the present invention;

[0029] Figure 2 It is a process flow schematic diagram of high-purity electronic-grade ethylene carbonate according to an embodiment of the present invention;

[0030] Figure 3 It is a process flow of high-purity electronic-grade ethylene carbonate using an integrated crystallizer according to an embodiment of the present invention;

[0031] Figure 4 It is the front view and top view of the scraper of the crystallizer according to an embodiment of the present invention;

[0032] Figure 5 It is a process flow schematic diagram of the prior art.

[0033] Description of the Reference Numerals in the Drawings

[0034] Figure 2 In the figure:

[0035] 1 is alkylene oxide, 2 is carbon dioxide, 3 is the product of the first reaction, 4 is the total reaction product, 5 is the flash gas, 6 is the flash liquid, 7 is the light component containing ethylene glycol, 8 is the heavy component containing poly-ethylene glycol, 9 is the side stream extraction of the distillation column, 10 is the first-stage crystallization slurry, 11 is the first-stage crystallization mother liquor, 12 is the first-stage crystallization filter cake, 13 is the second-stage crystallization slurry, 14 is the second-stage crystallization filter cake, 15 is the second-stage crystallization mother liquor, 16 is the washing slurry, 17 is the mother liquor of the washing kettle, 18 is the product washing liquid, 19 is the high-purity electronic-grade ethylene carbonate product;

[0036] I is the first reactor, II is the second reactor, III is the flash tank, IV is the distillation column, V is the first-stage crystallizer, VI is the first-stage centrifuge, VII is the second-stage crystallizer, VIII is the second-stage centrifuge, IX is the washing kettle, X is the third-stage centrifuge.

[0037] Figure 3 In the figure:

[0038] I is the first reactor, II is the second reactor, III is the flash tank, IV is the distillation column, 100 is the crystallization zone, 200 is the bed zone, and 300 is the melting zone;

[0039] 1 is an alkylene oxide, 2 is carbon dioxide, 3 is the product of the first reaction, 4 is the total reaction product, 5 is the flash gas, 6 is the flash liquid, 7 is the light component containing ethylene glycol, 8 is the heavy component containing polyethylene glycol, 9 is the side stream of the distillation column, 15 is the crystallization mother liquor, and 19 is the high-purity electronic-grade ethylene carbonate product.

[0040] Figure 4 Among them:

[0041] 100 is the stirring shaft, 101 is the stirring blade, 102 is the scraper, and 103 is the connecting piece of the scraper to the stirring shaft;

[0042] Figure 5 Among them:

[0043] I is the first reactor, II is the second reactor, III is the evaporator, IV is the light component removal tower, V is the heavy component removal tower, 3 is the gas containing CO 2 and 4 is the material flow containing ethylene carbonate, and 5 is the material flow containing the catalyst. Detailed Embodiments

[0044] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention and are not intended to limit the present invention.

[0045] In the present invention, unless otherwise specified, the orientation terms such as "upper, lower, left, and right" generally refer to the upper, lower, left, and right shown in the reference drawings; "inner and outer" refer to the inner and outer relative to the contour of each component itself.

[0046] In the present invention, unless otherwise specified, the orientation terms such as "upper, lower, top, and bottom" generally refer to the directions shown in the drawings or the relative position relationship descriptions of each component in the vertical, perpendicular, or gravitational directions.

[0047] The "vertical direction" refers to the up and down directions of the paper surface shown in the figure, and the "horizontal direction" refers to the roughly horizontal left and right directions of the paper surface shown in the figure; "inner and outer" generally refer to the inside and outside of the chamber relative to the chamber or the radial inside and outside relative to the center of the circle.

[0048] The present invention provides a system for producing high-purity electronic-grade carbonates. Along the material flow direction, the system includes: a heterogeneous reaction section, a separation section, and a crystallization section;

[0049] The heterogeneous reaction section is used for the heterogeneous reaction of alkylene oxide and carbon dioxide to prepare carbonate;

[0050] The separation section is used for separating the materials from the heterogeneous reaction section. Along the material flow direction, it includes a flash unit and a rectification unit. The flash unit includes at least one flash tank; the rectification unit includes at least one rectification column, and the side stream extraction of the rectification unit is connected to the feed inlet of the crystallization section;

[0051] The crystallization section is used for crystallizing and purifying the material mainly containing carbonate from the separation section.

[0052] In the existing preparation and separation of carbonate, multi-column rectification is adopted. The advantage of the crystallization separation adopted in the present invention is that: the rectification method has a higher temperature, while the crystallization method has a lower temperature. And the carbonate product is a thermosensitive substance, which is easily decomposed at high temperature and the chromaticity is not easy to meet the standard. The crystallization method is more conducive to the product meeting the standard.

[0053] According to a preferred embodiment of the present invention, along the material flow direction, the heterogeneous reaction section includes at least two reactors. The first reactor is a bubble column, and the reactors after the first reactor are bubble columns or fixed beds.

[0054] According to a preferred embodiment of the present invention, preferably, the last reactor is a fixed bed.

[0055] According to a preferred embodiment of the present invention, more preferably, the heterogeneous reaction section includes two reactors. The first reactor is a bubble column, and the second reactor is a fixed bed.

[0056] In the industrial mainstream technology, the homogeneous method is adopted, basically using 2 reactors, and the catalyst is liquid, which exists in the whole reaction system. The first one is a bubble column reactor, and the second reaction product and the catalyst directly pass through. The present invention adopts the heterogeneous technology, using at least two reactors, both filled with catalysts. The first / second one is a bubble column reactor, and the last one is a fixed bed reactor. There is backmixing in the bubble column, and part of the alkylene oxide cannot be completely consumed. The last fixed bed reactor ensures the complete conversion of the alkylene oxide.

[0057] According to a preferred embodiment of the present invention, the crystallization section has the functions of crystallization and solid-liquid separation and purification.

[0058] According to a preferred embodiment of the present invention, the crystallization section includes: at least two-stage crystallization units; preferably, each stage of crystallization unit is provided with a crystallizer; each of the crystallizers is a vertical crystallizer.

[0059] According to a preferred embodiment of the present invention, preferably, the vertical crystallizer adopts a vertical scraper crystallizer and / or an integrated crystallizer including a crystallization zone, a bed layer zone and a melting zone.

[0060] According to a preferred embodiment of the present invention, when the vertical crystallizer is selected as a vertical scraper crystallizer, a solid-liquid separation unit is provided after each crystallization unit, and preferably the solid-liquid separation unit is set as a centrifuge.

[0061] According to a preferred embodiment of the present invention, when an integrated crystallizer of a crystallization zone, a bed zone and a melting zone is selected, the solid-liquid separation in the crystallization section is achieved by means of solid sedimentation using the solid-liquid density difference.

[0062] The mainstream method in the existing device is multi-column rectification separation. It is reported that some enterprises have adopted the sweating crystallization method. The present invention adopts a combination of rectification and continuous crystallization. The reaction product is concentrated by rectification, and trace carbon dioxide, ethylene oxide and light and heavy components in the reaction product are separated. The carbonate ester after side-line concentration goes to the crystallization unit, and the mother liquor of the crystallization unit is recycled back to the rectification tower for concentration, so as to realize the recycling of the whole process. The light and heavy components are separated from the top and bottom of the rectification tower, avoiding the accumulation of impurities in the whole system.

[0063] According to a preferred embodiment of the present invention, the vertical scraper crystallizer is provided with a stirring shaft, and the stirring shaft includes at least 1 layer of scraper facilities. Each layer of scraper facilities includes at least 2 scraper blades; half of each scraper blade is a vertical scraper, which scrapes the crystals on the wall of the crystallizer by stirring and rotating, preferably made of non-metallic material; the other half is in the form of a blade to make the temperature and mixing inside the crystallizer uniform. Through research and analysis of the present invention, since the concentration of the raw material entering the crystallization is relatively high, it is easy to form a wall in the crystallizer, so a stirring shaft with a scraper is required, and the current equipment also has this function. However, the existing vertical scraper crystallizer lacks the function of stirring. Therefore, the present invention adopts a combination of a scraper and a blade, which can not only realize the function of the scraper, but also facilitate uniform heat transfer and uniform solid-liquid mixing, thereby reducing the phenomenon of solid blockage.

[0064] According to a preferred embodiment of the present invention, the crystallization section further includes: a washing unit, which includes a washing kettle and a solid-liquid separation unit arranged after the washing kettle along the material flow direction, and is used for washing the solid discharge of each crystallization unit and performing solid-liquid separation.

[0065] According to a preferred embodiment of the present invention, preferably, a part of the mother liquor after solid-liquid separation in the washing kettle is returned to the crystallization section, and the other part is recycled back to the washing kettle as washing liquid, and the temperature of the washing kettle is adjusted by exchanging heat with the side-line discharge of the rectification unit. The separation in the prior art adopts rectification separation, and there is no relevant report on the washing kettle in the sweating crystallization process. The present invention sets up a washing kettle, mainly for the purpose of improving the product purity. During the crystallization process, crystallization will include impurities, and the crystal surface will also adhere to impurities. By heating and dissolving in the washing kettle, the crystals are further purified.

[0066] According to a preferred embodiment of the present invention, the crystallization section includes, connected in series: a primary crystallizer, a primary centrifuge, a secondary crystallizer, a secondary centrifuge, a washing kettle, a tertiary centrifuge, and the connections include: (1) the side outlet of the rectification unit is communicated with the inlet of the primary crystallizer;

[0067] (2) the outlet of the primary crystallizer is communicated with the inlet of the primary centrifuge, the solid outlet of the primary centrifuge is communicated with the inlet of the washing kettle, and the liquid phase outlet is communicated with the inlet of the secondary crystallizer;

[0068] (3) the outlet of the secondary crystallizer is communicated with the inlet of the secondary centrifuge, the solid outlet of the secondary centrifuge is communicated with the inlet of the washing kettle, and the liquid phase outlet is communicated with the top inlet of the rectification unit;

[0069] (4) the solid inlet of the washing kettle is communicated with the solid outlets of the primary crystallizer and the secondary crystallizer, and the outlet of the washing kettle is communicated with the inlet of the tertiary centrifuge;

[0070] (5) the inlet of the tertiary centrifuge is communicated with the outlet of the washing kettle, the solid outlet of the tertiary centrifuge is the high-purity ethylene carbonate product, and the liquid outlet of the tertiary centrifuge is communicated with the inlet of the primary crystallizer and / or the washing liquid inlet of the washing kettle.

[0071] According to another preferred embodiment of the present invention, the crystallization section includes: two integrated crystallizers connected in series, and each crystallizer includes: a crystallization zone, a bed zone, and a melting zone. The material mainly containing carbonate from the separation section enters the first integrated crystallizer, crystallizes in the crystallization zone, then settles to the bed zone and enters the melting zone. A part of the liquid in the melting zone is taken out as a product, and a part is used as a washing liquid to pass through the bed zone from bottom to top. The top outlet of the first integrated crystallizer enters the second integrated crystallizer to complete the same operation.

[0072] The present invention provides a method for producing high-purity electronic-grade carbonate, and this method is carried out in the system described in the present invention.

[0073] The alkylene oxide and carbon dioxide enter the reaction section for a heterogeneous reaction;

[0074] The reaction product of the reaction section enters the flash unit for flashing in sequence, discharging the tail gas containing CO 2 The liquid phase rich in carbonate enters the rectification unit, the light components are taken out from the top of the tower, the heavy components are taken out from the bottom of the tower, and the concentrated carbonate is taken out from the side line and enters the crystallization section for crystallization purification.

[0075] The present invention mainly lies in the process design, and there are no special requirements for specific reaction conditions, raw material formulas, etc. The following is a demonstration, but it does not limit the scope of the present invention.

[0076] According to the present invention, the types of the alkylene oxides have a relatively wide optional range. For the present invention, preferably, the alkylene oxide is selected from one or more of ethylene oxide and propylene oxide.

[0077] According to an embodiment of the present invention, the feed molar ratio of the alkylene oxide to carbon dioxide is 1.0 - 1.2:1.

[0078] According to an embodiment of the present invention, the operating conditions of the reaction section include: the operating temperature is 80 - 160 °C, preferably 100 - 140 °C, and the operating pressure is 2 - 5 MPa.

[0079] According to an embodiment of the present invention, the catalyst is a heterogeneous resin catalyst.

[0080] According to an embodiment of the present invention, ethylene carbonate product with a mass fraction of not less than 99.5% is withdrawn from the reactor outlet.

[0081] According to an embodiment of the present invention, the operating conditions of the distillation unit include: the operating pressure is 0 - 5 kPa, preferably 0 - 2 kPa; the top temperature of the tower is 90 - 120 °C, the bottom temperature of the tower is 120 - 150 °C, preferably 140 - 150 °C; light components containing carbon dioxide and ethylene glycol are withdrawn from the top of the distillation column, heavy components containing diethylene glycol and polyethyleneglycol are withdrawn from the bottom of the tower, and ethylene carbonate material with a mass fraction of not less than 99.9% is withdrawn from the middle side line of the distillation column.

[0082] According to an embodiment of the present invention, the crystallization section includes the following connected in series: a primary crystallizer, a primary centrifuge, a secondary crystallizer, a secondary centrifuge, a washing kettle, and a tertiary centrifuge.

[0083] According to an embodiment of the present invention, the temperature of the primary crystallizer is 10 - 40 °C, the temperature of the secondary crystallizer is -5 °C to 20 °C, and the temperature of the washing kettle is 25 - 40 °C.

[0084] Each crystallization unit uses a vertical crystallizer. The outside of the vertical crystallizer is provided with a jacket, and a refrigerant is introduced into the jacket. The refrigerant is selected from one or more of chilled brine, ethylene glycol aqueous solution, and ethylene refrigerant. The temperature of the refrigerant is preferably -30 °C to -10 °C. According to the prior art, carbonate crystallization mainly adopts static sweating crystallization. Column tube fin type or falling film evaporator and other types are used. Refrigerant is passed on one side and static crystallization occurs on the other side. After a certain residence time, the refrigerant side is switched to a heating medium to precipitate the product crystallized on the heat transfer surface. The present invention uses a vertical scraper crystallizer and adopts continuous crystallization without switching between cold and hot media.

[0085] According to an embodiment of the present invention, the method further includes: exchanging heat between the side line discharge of the distillation column and the high-purity ethylene carbonate solid product to melt and heat up the solid product.

[0086] According to an embodiment of the present invention, the side stream of the distillation column is heat-exchanged with the washing liquid in the washing kettle to adjust the temperature of the washing kettle.

[0087] According to an embodiment of the present invention, the side stream of the distillation column is heat-exchanged with the crystallization mother liquor obtained from the crystallization unit to reduce the inlet temperature of the primary crystallization unit.

[0088] The temperature of the material coming out of the side line of the distillation in the present invention is about 100 - 130 °C, while the temperature required for crystallization is 0 - 40 °C, and cooling is needed. Heat is required during the process of the washing liquid entering the washing kettle, the mother liquor returning to the distillation column, and the primary product melting and being withdrawn. Therefore, the hot and cold material streams can be fully utilized for heat exchange to save energy consumption.

[0089] For the high-purity electronic-grade carbonate of the present invention, the purity of the high-purity carbonate product is ≥ 99.99%, preferably, the purity of the product is ≥ 99.994%, the chromaticity is < 10, and preferably the chromaticity is < 8. For the preparation and separation of the existing carbonate, multi-column distillation is used. In addition to the influence of azeotropes, the advantage of using the crystallization separation of the present invention is that the temperature of the distillation method is relatively high, while the temperature of the crystallization method is low. The carbonate product is a thermosensitive substance, which is easily decomposed at high temperatures and the chromaticity is not easily up to standard. The crystallization method is more conducive to the product meeting the standard.

[0090] The process method for preparing carbonate of the present invention is as follows:

[0091] As shown in Figure 2, fresh alkylene oxide 1 and carbon dioxide 2 enter the first reactor I to react to generate a first reaction product 3, and then enter the second reactor II to obtain the total reaction product 4. Preferably, the reaction conditions include: pressure 1.5 - 5 MPag, temperature 80 - 200 °C. After flashing in the flash tank III, containing CO 2The tail gas (flash gas 5) goes outside the system, and the liquid phase rich in ethylene carbonate (flash liquid 6) enters distillation column IV. In distillation column IV, the light component 7 containing ethylene glycol is taken out from the top of the column, the heavy component 8 containing poly-ethylene glycol is taken out from the bottom of the column, and the concentrated ethylene carbonate is taken out from the side line to obtain the side line draw 9 of the distillation column. The side line draw 9 of the distillation column enters the first crystallizer V at a temperature of 20 - 40°C. The formed first crystallization crystal slurry 10 is subjected to solid-liquid separation by the first centrifuge VI, and the first crystallization filter cake 12 enters the washing kettle. The first crystallization mother liquor 11 enters the second crystallizer VII, and the temperature of the second crystallizer VII is -10°C to 20°C. The second crystallization crystal slurry 13 is subjected to solid-liquid separation by the second centrifuge VIII. The second crystallization mother liquor 15 is returned to distillation column IV for concentration. The second crystallization filter cake 14 enters the washing kettle IX, and the temperature of the washing kettle IX is 30 - 45°C. The washing crystal slurry 16 of the washing kettle IX is subjected to solid-liquid separation by the third centrifuge X, and the filter cake is melted and collected as the product. A part of the washing kettle mother liquor 17 is returned to the inlet of the first crystallizer, and a part is returned to the inlet of the washing kettle IX as the product washing liquid 18. The high-purity electronic-grade ethylene carbonate product 19 is obtained from the third centrifuge X. The vertical scraper crystallizer is equipped with a stirring shaft, and at least one layer of scraper facilities is included on the stirring shaft. Each layer of scraper facilities includes at least 1 scraper blade; half of each scraper blade is a vertical scraper, which scrapes the crystals on the wall of the crystallizer through stirring and rotation, made of non-metallic material; the other half is in the form of a blade to make the temperature and mixing inside the crystallizer uniform.

[0092] In the following examples, the scraper of the crystallizer is as shown in Figure 4 : Each layer uses three scraper blades. On the left side of each scraper blade, there are two-layer blade-type stirring paddles for mixing and stirring; on the right side, there is a vertical scraper for scraping the crystallized solid from the wall of the crystallizer to avoid wall formation and affect the cold quantity transfer.

[0093] In the left figure: 100 is the stirring shaft, 101 is the stirring paddle, 102 is the scraper, and 103 is the connecting piece between the scraper and the stirring shaft. The ratio of the paddle diameter to the crystallizer wall is 0.6, the ratio of the paddle width to the stirrer diameter is 0.2, the angle between the paddle and the horizontal plane is 45°, and the stirring shaft rotation speed is 20 r / min. The right figure is the top view.

[0094] As shown in Figure 3 : Fresh alkylene oxide 1 and carbon dioxide 2 enter the first reactor I to react to generate the first reaction product 3, and then enter the second reactor II to obtain the total reaction product 4. Preferably, the reaction conditions include: pressure 1.5 - 5 MPag, temperature 80 - 200°C. After flashing in the flash tank III, the CO 2The tail gas (flash gas 5) goes outside the system, and the liquid phase rich in ethylene carbonate (flash liquid 6) enters distillation column IV. In distillation column IV, the light component 7 containing ethylene glycol is taken out from the top of the column, the heavy component 8 containing poly-ethylene glycol is taken out from the bottom of the column, and the concentrated ethylene carbonate is taken out from the side line to obtain the side line draw 9 of the distillation column. The side line draw 9 of the distillation column enters the crystallization unit.

[0095] The crystallization unit includes two integrated crystallizers. Each crystallizer is divided into a crystallization zone 100, a bed zone 200, and a melting zone 300. The side line material of the distillation column enters the middle and lower part of the integrated crystallizer, passes through the crystallization zone from bottom to top. As the temperature decreases in the crystallization zone, crystals gradually precipitate and settle to the bed zone under the action of gravity. The lower part of the bed zone is heated with a heat medium to melt it into a liquid as the melting zone. Part of the liquid in the melting zone is taken out as a product, and part of it is used as a washing liquid to pass through the bed zone from bottom to top to displace and purify the liquid on the crystal surface. The top outlet of the first-stage integrated crystallizer enters the middle and lower part of the second-stage integrated crystallizer, and the operation steps are the same as those of the first-stage integrated crystallizer. Finally, a high-purity electronic-grade ethylene carbonate product 19 is obtained from the bottom of the integrated crystallizer. The crystallization mother liquor 15 is then returned to the distillation column.

[0096] The present invention will be further described below by way of examples, but is not limited to these examples.

[0097] In the present invention, the heterogeneous resin catalyst is one or more of solid-supported ionic liquid type, solid base type, and composite resin type. The heterogeneous resin catalyst used in the following examples is a composite resin type heterogeneous catalyst with the brand name SEC-20.

[0098]

Example 1

[0099] According to Figure 2 the shown process, 99.95% mass fraction of refined ethylene oxide and food-grade CO 2 (The mass ratio of CO 2 to ethylene oxide is 1.2:1) enter the first reactor (bubble column reactor: pressure 3 MPag, temperature 130 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kgEO / kgCat) and the second reactor (fixed bed reactor: pressure 2.9 MPag, temperature 132 °C, the catalyst is a heterogeneous resin catalyst, space velocity 0.2 kgEO / kgCat) to react to produce ethylene carbonate. After flashing in the flash tank, CO 2The tail gas is sent outside the system. The liquid phase containing 99.9 wt% ethylene carbonate enters a distillation column. The pressure of the distillation column is 1 kPaA, the top temperature is 110 °C, and the bottom temperature is 140 °C. In the distillation column, the light components containing ethylene glycol are taken out from the top, and the heavy components containing poly-ethylene glycol, etc. are taken out from the bottom. After concentration, 99.95 wt% ethylene carbonate is taken out from the side line and enters the first crystallizer at a temperature of 15 °C. The formed crystal slurry is separated by a centrifuge into solid and liquid phases. The first-stage crystallization filter cake enters the washing kettle, and the first-stage crystallization mother liquor enters the second crystallizer. The temperature of the second crystallizer is 0 °C. After the second-stage crystallization crystal slurry is separated by a centrifuge into solid and liquid phases, the second-stage crystallization mother liquor returns to the distillation column for concentration. The second-stage crystallization filter cake enters the washing kettle. The washing liquid is the mother liquor of the third centrifuge. The temperature of the washing kettle is 34 °C. After the crystal slurry in the washing kettle is separated by a centrifuge into solid and liquid phases, the filter cake is melted and collected as the product. Part (80%) of the mother liquor returns to the inlet of the first crystallizer, and part (20%) of the mother liquor returns to the inlet of the washing kettle as the product washing liquid.

[0100] The purity of the final ethylene carbonate product is 99.995 wt%, the yield is 85%, and the chromaticity is 6.

[0101]

Example 2

[0102] According to Figure 2 the shown process, 99.9% high-purity ethylene oxide and food-grade CO 2 (the mass ratio of CO 2 to ethylene oxide is 1.1:1) enter the first reactor (bubble column reactor: pressure 2.5 MPag, temperature 100 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kgEO / kgCat) and the second reactor (pressure 2.4 MPag, temperature 102 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kgEO / kgCat) to react to produce ethylene carbonate. After flashing in a flash tank, the tail gas of CO 2 is sent outside the system. The liquid phase containing 99.5 wt% ethylene carbonate enters a distillation column. The pressure of the distillation column is 1 kPaA, the top temperature is 110 °C, and the bottom temperature is 140 °C. In the distillation column, the light components containing ethylene glycol are taken out from the top, and the heavy components containing poly-ethylene glycol, etc. are taken out from the bottom. After concentration, 99.95 wt% ethylene carbonate is taken out from the side line and enters the first crystallizer at a temperature of 15 °C. The formed crystal slurry is separated by a centrifuge into solid and liquid phases. The first-stage crystallization filter cake enters the washing kettle, and the first-stage crystallization mother liquor enters the second crystallizer. The temperature of the second crystallizer is 0 °C. After the second-stage crystallization crystal slurry is separated by a centrifuge into solid and liquid phases, the second-stage crystallization mother liquor returns to the distillation column for concentration. The second-stage crystallization filter cake enters the washing kettle. The washing liquid is the mother liquor of the third centrifuge. The temperature of the washing kettle is 34 °C. After the crystal slurry in the washing kettle is separated by a centrifuge into solid and liquid phases, the filter cake is melted and collected as the product. Part (85%) of the mother liquor returns to the inlet of the first crystallizer, and part (15%) of the mother liquor returns to the inlet of the washing kettle as the product washing liquid.

[0103] The purity of the final ethylene carbonate product is 99.99 wt%, the yield is 80%, and the chromaticity is 6.

[0104]

Example 3

[0105] According to Figure 2 the shown process, 99.95% mass fraction of refined ethylene oxide and food-grade CO 2 (the mass ratio of CO 2 to ethylene oxide is 1.2:1) enter the first reactor (bubble column reactor: parameters pressure 3 MPag, temperature 130 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kgEO / kgCat) and the second reactor (fixed bed reactor: 2.9 MPag, temperature 130 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kgEO / kgCat) to react to produce ethylene carbonate. After flashing in the flash tank, the tail gas of CO 2 goes outside the system. The liquid phase containing 99.9 wt% of ethylene carbonate enters the distillation column. The pressure of the distillation column is 5 kPaA, the top temperature is 110 °C, and the bottom temperature is 150 °C. In the distillation column, the light components containing ethylene glycol are taken out from the top, and the heavy components containing polyethyleneglycol, etc. are taken out from the bottom. After concentration, 99.95 wt% ethylene carbonate is taken out from the side line and enters the first crystallizer at a temperature of 20 °C. The formed crystal slurry is separated by solid-liquid separation, and the first-stage crystallization filter cake enters the washing kettle. The first-stage crystallization mother liquor enters the second crystallizer at a temperature of 5 °C. After the second-stage crystallization crystal slurry is separated by solid-liquid separation, the second-stage crystallization mother liquor returns to the distillation column for concentration. The second-stage crystallization filter cake enters the washing kettle. The washing liquid is the mother liquor of the three-stage centrifuge. The temperature of the washing kettle is 32 °C. After the crystal slurry in the washing kettle is separated by solid-liquid separation, the filter cake is melted as the product and collected. Part (80%) of the mother liquor returns to the inlet of the first crystallizer, and part (20%) of the mother liquor returns to the inlet of the washing kettle as the product washing liquid.

[0106] The purity of the final ethylene carbonate product is 99.991 wt%, the yield is 85%, and the chromaticity is 8.

[0107]

Example 4

[0108] The implementation method is similar to that of Example 3, except that an integrated crystallizer is used, and the process is as Figure 3 shown.

[0109] 99.95% mass fraction of refined ethylene oxide and food-grade CO 2 (CO 2enters the first reactor (bubble column reactor: 2.9 MPag, temperature 130 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kg EO / kg Cat) and the second reactor (fixed bed reactor: 2.8 MPag, temperature 130 °C, the catalyst is a heterogeneous resin catalyst, space velocity 2 kg EO / kg Cat) at a mass ratio of ethylene oxide to 1.08:1 to react to produce ethylene carbonate. After flashing in a flash tank, the tail gas of CO 2 goes outside the system, and the liquid phase containing 99.9 wt% ethylene carbonate enters a distillation column. The pressure of the distillation column is 5 kPaA, the top temperature is 110 °C, and the bottom temperature is 150 °C. In the distillation column, the light components containing ethylene glycol are taken out from the top of the column, and the heavy components containing polyethyleneglycol are taken out from the bottom of the column. After concentration, 99.95 wt% ethylene carbonate is taken out from the side line and enters the first crystallizer at a temperature of 20 °C. The material enters the crystallization zone from bottom to top, and the formed crystals are separated from the liquid material under the action of gravity and sink, entering the bed layer area. As the crystals accumulate, the crystals gradually settle to the melting zone. The melting zone is heated by steam to melt the crystals into a liquid product, which is pumped out. The crystallization mother liquor overflows from the top of the first crystallizer and enters the second crystallizer. The operation mode of the second crystallizer is similar to that of the first crystallizer, with a temperature of 5 °C, and the ethylene carbonate in the mother liquor is further recovered.

[0110] The purity of the final ethylene carbonate product is 99.991 wt%, the yield is 80%, and the chromaticity is 8.

[0111]

Comparative Example 1

[0112] Traditional homogeneous process technologies such as Figure 5 shown, the raw materials ethylene oxide, CO 2 and the homogeneous catalyst enter the first reactor I and the second reactor II together. The reaction products containing ethylene carbonate, catalyst, CO 2 , ethylene glycol, and polyethyleneglycol are separated in an evaporator III to obtain the gas 3 containing CO 2 , the stream 4 containing ethylene carbonate, and the stream 5 containing the catalyst. The stream 4 containing ethylene carbonate enters a light component removal column IV and a heavy component removal column V for separation, and an electronic grade ethylene carbonate product is obtained from the side line of the heavy component removal column. Since the reaction system contains a homogeneous catalyst and the separation system contains a homogeneous catalyst, it cannot be completely recycled and needs to be continuously discharged and replenished externally, generating waste liquid.

[0113] Compared with the traditional homogeneous process technology, the present invention does not generate waste liquid containing a catalyst, only generates a small amount of solid waste of heterogeneous catalyst, and can reduce the waste liquid discharge by more than 90%.

[0114] Compared with the traditional homogeneous method technology, the present invention does not require the energy consumption for separating the homogeneous catalyst evaporator III, and the energy consumption for separation by crystallization is lower than that by rectification, with the comprehensive energy saving being at least 15%.

[0115] Compared with the traditional method of "heterogeneous reaction + rectification separation", the present invention saves at least 10% of the energy consumption.

[0116] For any numerical values mentioned in the present invention, if there is only a two-unit interval between any minimum value and any maximum value, all values increasing by one unit from the minimum value to the maximum value are included. For example, if the amount of a component or the value of a process variable such as temperature, pressure, time, etc. is stated as 50 - 90, it means in this specification that 51 - 89, 52 - 88... as well as 69 - 71 and 70 - 71, etc. are specifically listed. For non-integer values, appropriate consideration can be given to taking 0.1, 0.01, 0.001, or 0.0001 as a unit. These are only some specifically indicated examples. In the present invention, in a similar manner, all possible combinations of the numerical values between the listed minimum value and the maximum value are considered to have been disclosed.

[0117] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0118] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including the combination of each specific technical feature in any suitable way. To avoid unnecessary repetition, the present invention does not separately explain various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A system for producing high-purity electronic-grade carbonate, characterized in that, along the material flow direction, the system includes: a heterogeneous reaction section, a separation section, and a crystallization section; the heterogeneous reaction section is used for the heterogeneous reaction of alkylene oxide and carbon dioxide to prepare carbonate; the separation section is used for separating the material from the heterogeneous reaction section. Along the material flow direction, it includes a flash unit and a rectification unit. The flash unit includes at least one flash tank; the rectification unit includes at least one rectification column, and the side-line draw of the rectification unit is connected to the feed inlet of the crystallization section; the crystallization section is used for crystallizing and purifying the material mainly containing carbonate from the separation section.

2. The system according to claim 1, wherein, along the material flow direction, the heterogeneous reaction section includes at least two reactors. The first reactor is a bubble column, and the reactors after the first reactor are bubble columns or fixed beds; preferably, the last reactor is a fixed bed; more preferably, the heterogeneous reaction section includes two reactors. The first reactor is a bubble column, and the second reactor is a fixed bed.

3. The system according to claim 1 or 2, wherein, the crystallization section has the functions of crystallization and solid-liquid separation and purification; the crystallization section includes: at least two-stage crystallization units; preferably, crystallization vessels are arranged in each stage of crystallization units; each of the said crystallization vessels is a vertical crystallization vessel; preferably, the vertical crystallization vessel adopts a vertical scraper crystallizer and / or an integrated crystallizer including a crystallization zone, a bed zone, and a melting zone. When the vertical crystallization vessel is selected as the vertical scraper crystallizer, a solid-liquid separation unit is arranged after each stage of crystallization unit. Preferably, the solid-liquid separation unit is arranged as a centrifuge; When the integrated crystallizer including a crystallization zone, a bed zone, and a melting zone is selected, the solid-liquid separation in the crystallization section is realized by the way of solid sedimentation using the solid-liquid density difference.

4. The system according to claim 3, wherein, the vertical scraper crystallizer is provided with a stirring shaft, and there are no less than 1 layer of scraper facilities on the stirring shaft. Each layer of scraper facilities includes no less than 2 scraper blades; half of each scraper blade is a vertical scraper, which scrapes the crystals on the wall of the crystallizer by stirring and rotating, preferably made of non-metallic material; the other half is in the form of a blade to make the temperature and mixing inside the crystallizer uniform.

5. The system according to any one of claims 1-4, wherein, the crystallization section further includes: a washing unit, which includes a washing kettle and a solid-liquid separation unit arranged after the washing kettle along the material flow direction, and is used for washing the solid discharge of each stage of crystallization unit and performing solid-liquid separation; preferably, a part of the mother liquor after solid-liquid separation in the washing kettle is returned to the crystallization section, and the other part is circulated back to the washing kettle as washing liquid. The washing liquid adjusts the temperature of the washing kettle by exchanging heat with the side-line discharge of the rectification unit.

6. The system according to any one of claims 1-5, wherein, the crystallization section includes a series connection of: a first-stage crystallizer, a first-stage centrifuge, a second-stage crystallizer, a second-stage centrifuge, a washing kettle, a third-stage centrifuge. The connections include: (1) The side-line outlet of the rectification unit is communicated with the inlet of the first-stage crystallizer; (2) The outlet of the first-stage crystallizer is connected to the inlet of the first-stage centrifuge. The solid outlet of the first-stage centrifuge is connected to the inlet of the washing kettle, and the liquid-phase outlet is connected to the inlet of the second-stage crystallizer. (3) The outlet of the second-stage crystallizer is connected to the inlet of the second-stage centrifuge. The solid outlet of the second-stage centrifuge is connected to the inlet of the washing kettle, and the liquid-phase outlet is connected to the inlet at the top of the rectification unit. (4) The solid inlet of the washing kettle is connected to the solid outlets of the first-stage crystallizer and the second-stage crystallizer. The outlet of the washing kettle is connected to the inlet of the third-stage centrifuge. (5) The inlet of the third-stage centrifuge is connected to the outlet of the washing kettle. The solid outlet of the third-stage centrifuge is the high-purity ethylene carbonate product. The liquid outlet of the third-stage centrifuge is connected to the inlet of the first-stage crystallizer and / or the washing liquid inlet of the washing kettle. Or the crystallization section includes: two integrated crystallizers connected in series. Each crystallizer includes: a crystallization zone, a bed zone, and a melting zone. The material mainly containing carbonate from the separation section enters the first integrated crystallizer, crystallizes in the crystallization zone, then settles to the bed zone and enters the melting zone. A part of the liquid in the melting zone is taken out as a product, and a part is used as a washing liquid to pass through the bed zone from bottom to top. The top outlet of the first integrated crystallizer enters the second integrated crystallizer to complete the same operation.

7. A method for producing high-purity electronic-grade carbonate, which is carried out in the system described in any one of claims 1-6. The alkylene oxide and carbon dioxide enter the reaction section for heterogeneous reaction. The reaction product of the reaction section enters the flash unit for flashing in sequence, and the tail gas containing CO is discharged. 2 The liquid phase rich in carbonate enters the rectification unit. The light components are taken out from the top of the column, the heavy components are taken out from the bottom of the column, and the concentrated carbonate is taken out from the side line and enters the crystallization section for crystallization purification.

8. According to the method described in claim 7. Wherein, The alkylene oxide is selected from one or more of ethylene oxide and propylene oxide; and / or The feed molar ratio of alkylene oxide to carbon dioxide is 1.0-1.2:1; and / or The operating conditions of the reaction section include: The operating temperature is 80-160°C, and the operating pressure is 2-5 MPa; and / or The catalyst is a heterogeneous resin catalyst; The ethylene carbonate product with a mass fraction of not less than 99.5% is taken out at the reactor outlet.

9. According to the method described in claim 7 or 8. Wherein, The operating conditions of the rectification unit include: The operating pressure is 0-2 kPa, the top temperature of the tower is 90-120°C, and the bottom temperature of the tower is 120-150°C; The light components containing carbon dioxide and ethylene glycol are taken out at the top of the rectification tower, the heavy components containing diethylene glycol and polyethyleneglycol are taken out at the bottom of the tower, and the ethylene carbonate material with a mass fraction of not less than 99.9% is taken out from the middle upper side line of the rectification tower.

10. According to the method described in any one of claims 7-9. Wherein, The crystallization section includes the following connected in series: the first-stage crystallizer, the first-stage centrifuge, the second-stage crystallizer, the second-stage centrifuge, the washing kettle, and the third-stage centrifuge; The temperature of the first-stage crystallizer is 10-40°C, the temperature of the second-stage crystallizer is -5°C to 20°C, and the temperature of the washing kettle is 25-40°C; and / or Each crystallization unit uses a vertical crystallizer. The outside of the vertical crystallizer is provided with a jacket, and a refrigerant is introduced into the jacket. The refrigerant is selected from one or more of chilled brine, ethylene glycol aqueous solution, and ethylene refrigerant. The temperature of the refrigerant is preferably -30°C to -10°C.

11. According to the method described in any one of claims 7-10. Wherein, This method further includes: The side stream of the rectification column is heat-exchanged with the solid product of high-purity ethylene carbonate to melt and heat up the solid product; and / or The side stream of the rectification column is heat-exchanged with the washing liquid in the washing kettle to adjust the temperature of the washing kettle; and / or The side stream of the rectification column is heat-exchanged with the crystallization mother liquor obtained from the crystallization unit to reduce the inlet temperature of the primary crystallization unit.

12. The high-purity electronic grade carbonate obtained by the method according to any one of claims 7-11, characterized in that the purity of the high-purity carbonate product is ≥99.99%, preferably, the purity of the product is ≥99.994%, the chromaticity is <10, and preferably the chromaticity is <8.

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