CN216497526U - A system for co-production of dimethyl carbonate and diol - Google Patents

Abstract

The utility model relates to a system for coproducing dimethyl carbonate and dihydric alcohol, wherein a methanol and dimethyl carbonate azeotrope material is adopted at the tower top of a reaction rectifying tower to enter a first azeotropic rectifying tower, a material extracted at the tower bottom of the reaction rectifying tower enters a methanol, dihydric alcohol and catalyst separation unit, a material at the tower bottom of the first azeotropic rectifying tower enters a second azeotropic rectifying tower, a first steam material, a second steam material and a third steam material which are rich in methanol are extracted at the tower top of the first azeotropic rectifying tower, the first steam material enters the reaction rectifying tower, the second steam material enters a reboiler at the tower bottom of the reaction rectifying tower, and the third steam material enters a reboiler at the tower bottom of the second azeotropic rectifying tower; and obtaining a DMC product at the bottom of the second azeotropic distillation tower. Through the structural design, the utility model fully utilizes the latent heat of the high-pressure steam at the top of the first azeotropic distillation tower, improves the energy efficiency to the maximum extent and reduces the equipment investment.

Description

A system for co-production of dimethyl carbonate and diol

technical field

The utility model belongs to the technical fields of chemical industry, materials and environmental protection, in particular to a system for co-producing dimethyl carbonate and diol.

Background technique

Dimethyl Carbonate (DMC for short, also known as dimethyl carbonate) is an environmentally friendly organic chemical product and an important intermediate in organic synthesis. Its molecular structure contains functional groups such as carbonyl, methyl and methoxy groups, and has a variety of reactive properties; it is also a green, non-toxic solvent that can replace aromatic hydrocarbons and acetate solvents, and it can also be used as an oxygen-containing solvent for gasoline. Additive to replace MTBE. At present, DMC is mainly used as an electrolyte solvent for lithium-ion batteries, and the annual demand exceeds 1 million tons. Diols mainly include ethylene glycol and propylene glycol, which are important organic chemical raw materials. They are mainly used in the production of lubricants, plasticizers, and antifreeze agents, especially in polyester fibers, unsaturated polyester resins and other polyester industries. application, the annual demand exceeds 20 million tons.

There are various processes for DMC production. Among them, the transesterification method of generating DMC and by-product ethylene (propylene) glycol through the reaction of methanol and ethylene (propylene) carbonate is a green chemical process with 100% atomic and molecular utilization. The advantage is that it is the most commonly used production process at present. Ethylene (propylene) carbonate can be prepared from carbon dioxide and ethylene oxide (propylene) under high pressure. The process of producing DMC and co-producing ethylene glycol with the transesterification reaction process of methanol and ethylene carbonate below illustrates the existing problems, and the process of producing DMC and propylene glycol with the transesterification reaction process of methanol and propylene carbonate has the same characteristics.

In the transesterification process of methanol and ethylene carbonate to generate DMC and by-product ethylene glycol, the complete conversion of ethylene carbonate can be achieved by reactive distillation. Since methanol and DMC form a binary azeotrope, in practice, excess methanol (the feed molar ratio of methanol to ethylene carbonate is 9-11, far greater than the reaction metering ratio 2) is introduced into the reactive distillation process, and the azeotrope will be The DMC product generated by the reaction is continuously distilled from the top of the tower, thereby improving the conversion rate of ethylene carbonate. At the same time, the tower still needs to retain a small amount of methanol and ethylene glycol to be extracted together to reduce the temperature of the tower still to prevent the dehydration and condensation reaction of ethylene glycol. The transesterification reaction process is thermodynamically controlled, and the equilibrium conversion rate of the reaction decreases with the increase of the reaction temperature.

At present, the process of separating methanol and DMC binary azeotrope includes extractive distillation method and pressurized distillation separation method. The concentration of the binary azeotrope formed by methanol-DMC changes with the pressure, and the pressurized rectification method uses the increased pressure to break the azeotrope composition under normal pressure, as shown in the following table. Compared with the extractive rectification method, the pressurized rectification method can avoid the introduction of the extractant, and at the same time, the top temperature of the pressurized column is higher, and the latent heat of the column top steam can be coupled and utilized.

Table 1: Methanol-DMC azeotropic composition and azeotropic temperature at different pressures

pressure/bar Azeotropic temperature/℃ DMC azeotrope concentration/mass % DMC azeotropic concentration/mol% 0.5 46.6 33.6 15.3 0.6 50.8 32.8 14.8 0.8 57.8 31.4 14.02 1 64 30 13.34 2 82 26.6 11.22 4 104 20.7 8.72 6 118 17.5 7.06 8 129 14.8 5.77 10 138 12.4 4.70 12 144 9.98 3.79 15 155 7.04 2.62 18 161 4.42 1.62 20 166 2.81 1.02 twenty two 170 1.29 0.46

As shown in Table 1, increasing the pressure of the pressurized rectification column can reduce the residual DMC concentration of methanol at the top of the column, and can also utilize the latent heat of vaporization of the distillation stream at the top of the column through thermal coupling, but the heating temperature of the column kettle reboiler must also be corresponding Increase, put forward higher requirements for heating heat source and reboiler material.

However, the current methanol and DMC binary azeotrope separation process has the problem of large energy consumption, and the production cost of DMC is relatively high, which is not competitive compared with other process routes. The main reasons are in two aspects: first, the methanol circulation is very large, 1mol of DMC product generated in the reactive distillation process under normal pressure needs to be distilled out with 6.5mol of methanol, and a large amount of methanol needs to be distilled out again in the pressurized rectification column; Secondly, in industrial practice, a large amount of high-concentration methanol at the top of the pressurized rectification column is passed into the atmospheric separation column for separation, and the high-purity methanol obtained at the bottom of the atmospheric separation column is recycled back to the reactive rectification, and the methanol at the top of the atmospheric separation column is recycled. The relative volatility of -DMC azeotrope and methanol at the bottom is very low, the reflux ratio is high, the steam energy consumption is also high, and the equipment is huge.

分析，过程工程学报，2018，1308-1313)研究了常压反应精馏塔+高压共沸精馏塔+常压精馏的工艺，产品碳酸二甲酯从常压塔底采出，虽然利用加压精馏塔顶蒸汽热耦合作为反应精馏塔和常压塔的再沸器热源，但高压能量没有得到利用，且循环甲醇中碳酸二甲酯浓度较高，能耗仍然较大；论文(反应精馏合成碳酸二甲酯过程优化及热集成研究，现代化工，2020，226-229)研究了反应精馏+加压精馏+常压精馏的工艺，碳酸二甲酯从加压精馏塔底采出，并研究了热集成技术，但由于常压塔采出甲醇，能耗仍然较大。专利文献200610137892公开了一种酯交换法生产碳酸二甲酯过程中能量综合利用技术，将加压精馏塔顶馏出物作为常压反应精馏塔和常压精馏塔的热源，但能量利用效率不高，且设备投资较大；专利文献201310692281公开了一种碳酸二甲酯和甲醇生产和分离的节能工艺，反应精馏塔能量消耗大，加压精馏塔能量利用效率不高，设备投资也较大；专利文献201410755182公开了一种酯交换法连续生产碳酸二甲酯联产1,2丙二醇的方法，包括常压反应精馏塔和高压共沸精馏塔，共沸精馏塔塔底得到产品二甲基碳酸酯，塔顶得到富甲醇物料，此物料再进入后续的常压共沸精馏塔，塔底得到甲醇循环到反应精馏塔循环使用，能耗较高，设备投资也较大；专利文献201810706120公开了一种联产乙二醇和碳酸二甲酯的设备和方法，采用加压精馏分离，从塔底得到碳酸二甲酯，塔顶物料进入后续的甲醇常压分离塔，塔底得到高纯度的甲醇，能耗高，设备庞大；专利文献202011484989公开了一种酯交换法碳酸二甲酯的生产装置及其使用方法，采用了与201410755182和201810706120相似方法，同样存在着能耗较大的问题。The paper (Research on New Technology of Pressurized Separation of Methanol and Dimethyl Carbonate Azeotrope, 2001, Anhui Chemical Industry, 2-3) disclosed for the first time the combination of pressurized distillation column and atmospheric distillation column to separate methanol and dimethyl carbonate However, there is no coupling utilization of energy, and the energy efficiency is low; the paper (Phase Equilibrium and Process Simulation of Separation of Methanol-Dimethyl Carbonate by Pressurized-Atmospheric Pressure Distillation, 2003, Chinese Journal of Process Engineering, 453-458) published Similar research work does not involve the comprehensive utilization of energy; the paper (Novel Procedure for the Synthesis of Dimethyl Carbonate by ReactiveDistillation, Ind.Eng.Chem.Res.2014, 3321-3328) studies the atmospheric The combined technology of pressure azeotropic distillation column and atmospheric distillation column, dimethyl carbonate is extracted from the pressurized distillation column, and methanol is extracted from the atmospheric distillation column, which has high energy consumption and huge equipment; the paper (Optimization and control of a reactive distillation process for the synthesis of dimethyl carbonate, Chinese Journal of Chemical Engineering, 2017, 1079–1090) studied the process of atmospheric pressure reactive distillation column + pressurized azeotropic distillation column, dimethyl carbonate from the pressurized column The bottom output, the methanol at the top of the column is recycled into the reactive distillation column, and the energy consumption is also high;

Analysis, Chinese Journal of Process Engineering, 2018, 1308-1313) studied the process of atmospheric reactive distillation column + high pressure azeotropic distillation column + atmospheric distillation, the product dimethyl carbonate was extracted from the bottom of the atmospheric pressure column, although using The thermal coupling of the top steam of the pressurized rectification tower is used as the heat source of the reboiler of the reactive distillation tower and the atmospheric tower, but the high pressure energy is not utilized, and the concentration of dimethyl carbonate in the circulating methanol is high, and the energy consumption is still large; (Research on Process Optimization and Thermal Integration of Synthesis of Dimethyl Carbonate by Reactive Distillation, Modern Chemical Industry, 2020, 226-229) The process of reactive distillation + pressurized distillation + atmospheric distillation was studied. The bottom of the distillation column is extracted, and the heat integration technology has been studied, but the energy consumption is still relatively large due to the extraction of methanol in the atmospheric column. Patent document 200610137892 discloses a technology for comprehensive utilization of energy in the process of producing dimethyl carbonate by transesterification. The utilization efficiency is not high, and the equipment investment is relatively large; patent document 201310692281 discloses an energy-saving process for the production and separation of dimethyl carbonate and methanol, the energy consumption of the reactive distillation column is large, and the energy utilization efficiency of the pressurized distillation column is not high, Equipment investment is also relatively large; patent document 201410755182 discloses a method for continuous production of dimethyl carbonate by transesterification to co-produce 1,2 propylene glycol, including atmospheric pressure reactive distillation column and high pressure azeotropic distillation column, azeotropic distillation The product dimethyl carbonate is obtained at the bottom of the tower, and the methanol-rich material is obtained at the top of the tower. This material enters the subsequent atmospheric pressure azeotropic rectification tower, and the methanol obtained at the bottom of the tower is recycled to the reactive rectification tower for recycling, and the energy consumption is high. Equipment investment is also relatively large; patent document 201810706120 discloses a kind of equipment and method for co-production of ethylene glycol and dimethyl carbonate, adopts pressurized rectification separation, obtains dimethyl carbonate from the bottom of the tower, and the top material enters the subsequent methanol Atmospheric separation tower, obtaining high-purity methanol at the bottom of the tower, with high energy consumption and huge equipment; Patent document 202011484989 discloses a production device for transesterification dimethyl carbonate and its use method, and adopts methods similar to 201410755182 and 201810706120 , there is also the problem of large energy consumption.

In conclusion, there is still much room for improvement and improvement in the prior art in terms of energy consumption and equipment optimization.

Utility model content

Aiming at the current situation of relatively large energy consumption and equipment investment in the methanol and DMC binary azeotrope separation technology in the prior art, the utility model provides a system for co-producing dimethyl carbonate and diol.

The scheme provided by the utility model is a system for producing dimethyl carbonate and glycol in a transesterification reaction process with low energy consumption and low investment.

The purpose of the present utility model can be achieved through the following technical solutions:

The utility model firstly provides a system for co-producing dimethyl carbonate and diol, comprising a transesterification reaction unit, a methanol and dimethyl carbonate azeotrope separation unit, and a methanol, diol and catalyst separation unit, The transesterification reaction unit is composed of a reactive distillation column, the methanol and dimethyl carbonate azeotrope separation unit is composed of a first azeotropic distillation column and a second azeotropic distillation column, and the methanol, two The alcohol and catalyst separation unit is used to realize methanol recovery, glycol refining, catalyst recovery and by-product recovery, and the top of the reactive distillation column uses methanol and dimethyl carbonate azeotrope materials to enter the first co-product. Boiling rectification column, the material extracted at the bottom of the reactive rectification column of the reactive rectification column enters the methanol, glycol and catalyst separation unit, and the bottom of the first azeotropic rectification column of the first azeotropic rectification column The material enters the second azeotropic distillation column, and three steam materials rich in methanol are extracted from the top of the first azeotropic distillation column, which are the first steam material, the second steam material, and the third steam material. Materials, the first steam material enters the reactive rectification tower, the second steam material enters the reboiler at the bottom of the reactive rectification tower, and the third steam material enters the second azeotropic rectification tower bottom for reboiler. In the boiler; the bottom of the second azeotropic distillation column obtains the DMC product.

The utility model makes full use of the latent heat of the high-pressure steam at the top of the first azeotropic rectification tower through such a structural design, maximizes the energy efficiency and reduces equipment investment.

In one embodiment of the present utility model, the reactive distillation column is used to receive methanol material, alkene carbonate material and catalyst material, and make the methanol material and alkene carbonate material undergo transesterification reaction.

In one embodiment of the present invention, the reactive rectification column is used as a reactor, selected from a packed column or a tray column, and is divided into a rectification section and a reaction section.

In one embodiment of the present invention, the reactive rectification column is a vacuum rectification column, and the absolute pressure at the top of the column is less than 80 kPa and greater than 50 kPa. In this way, it is convenient to reduce the reaction temperature, improve the reaction rate of reactive rectification, and at the same time, it is convenient to increase the DMC content at the top of the reactive rectification tower, reduce the methanol circulation flow, and reduce the energy consumption of the DMC and methanol azeotrope separation process.

In one embodiment of the present utility model, the first azeotropic rectification tower is a high-pressure rectification tower, and the absolute pressure at the top of the tower is greater than 1.3MPa and less than 2.2Mpa; it is convenient to improve the methanol at the top of the first azeotrope rectification tower. The steam temperature, as the heat source of the bottom reboiler of the reactive distillation column and the second azeotropic distillation column, is also convenient to further reduce the content of DMC in the top steam, reduce the reflux ratio, and further reduce the energy consumption.

In one embodiment of the present utility model, the second azeotropic rectification column is a pressurized rectification column, and the absolute pressure at the top of the column is greater than 200kPa and less than 500kPa, which facilitates the utilization of the latent heat of the steam at the top of the column and further improves the energy efficiency.

In one embodiment of the present invention, a steam turbine generator is installed on the pipeline for the first steam material to enter the reactive distillation column. The steam turbine generator is used to recover the energy of the first steam material for power generation, so that the high-temperature and high-pressure organic steam becomes low-temperature and low-pressure organic steam and then enters the reactive distillation column, which can significantly increase the energy At the same time, the steam material directly enters the bottom of the reactive distillation column for direct heating, which saves the indirect heat exchanger and saves the investment.

In one embodiment of the present invention, the second steam material enters the reboiler at the bottom of the reactive rectification column and becomes condensed liquid, and then flows back to the top of the first azeotropic rectification column. As a reflux liquid, the design facilitates the coupling of the reactive distillation column to utilize the latent heat of steam at the top of the first azeotropic distillation column and reduces energy consumption.

In one embodiment of the present utility model, the third steam material enters into the reboiler at the bottom of the second azeotropic rectification column and becomes condensed liquid, and then flows back to the bottom of the first azeotropic rectification column. The top of the column is used as the reflux liquid, and the design facilitates the coupling of the second azeotropic rectification column to utilize the steam latent heat from the column top of the first azeotropic rectification column, thereby further reducing energy consumption.

In one embodiment of the present utility model, a liquid turbine is installed on the pipeline for the bottom material of the first azeotrope rectification column to enter the second azeotrope rectification column, so as to recover the first azeotrope The energy of the high pressure liquid at the bottom of the rectification column is used to generate electricity.

In one embodiment of the present invention, the methanol and dimethyl carbonate azeotrope material first enters the second azeotrope rectification tower overhead condenser of the second azeotrope rectification tower, and then passes through thermal coupling. The methanol and dimethyl carbonate azeotrope material after the temperature increase is obtained after the latent heat of the column top steam of the second azeotrope rectifying column is preheated and heated up, and the methanol and dimethyl carbonate azeotrope material after the temperature increase is reheated. Entering into the first azeotropic distillation column can further improve the energy utilization efficiency of the system.

In one embodiment of the present utility model, the top of the reactive rectification tower is provided with a reactive rectification tower overhead condenser, and after the circulating cooling water feed enters the reactive rectification tower overhead condenser for heat exchange, the circulating cooling water flows out. Discharge, the circulating cooling water discharge is used to flow to the circulating water pump.

In one embodiment of the present utility model, the bottom of the first azeotrope rectification column is provided with a first azeotrope rectification column bottom reboiler, and the steam stream enters the first azeotrope rectification column bottom reboiler After the heat exchange of the boiler, the condensed water stream flows out, and the condensed water stream is used to flow to the boiler.

In one embodiment of the present utility model, the methanol, glycol and catalyst separation unit receives the material extracted from the bottom of the reactive distillation column and separates the recovered methanol material, by-product 1 material, by-product 2 material, refined glycol product and recovery catalyst,

The refined glycol product is selected from refined ethylene glycol or propylene glycol products; the by-product 1 material is selected from ethylene glycol monomethyl ether or propylene glycol monomethyl ether; the by-product 2 material is selected from diethanol or propylene glycol.

Compared with the prior art, the utility model has the following remarkable effects:

1. The reaction distillation column of the reaction unit adopts negative pressure operation, which can increase the concentration of the azeotrope DMC steamed at the top of the column, reduce the methanol steaming and the circulation amount; at the same time, reduce the temperature of the reaction section in the column, which is beneficial to improve the ester Equilibrium conversion rate of exchange reaction, reducing reflux ratio and steam energy consumption;

2. Three secondary organic steams are produced from the top of the first azeotrope rectification tower of the azeotrope separation unit, and a steam turbine and a liquid turbine are prepared at the same time, and the optimized combination of process conditions is also included to maximize the use of the mechanical energy of the secondary steam and latent heat, which significantly improves energy efficiency, reduces primary energy consumption, and saves equipment investment;

3. The second azeotropic distillation column of the azeotrope separation unit is operated under pressure, which can utilize the latent heat of the top steam, which further improves the energy coupling degree and energy utilization efficiency of the rectification system.

Description of drawings

FIG. 1 is a schematic structural diagram of a system for the co-production of dimethyl carbonate and diol provided in Example 1 of the present utility model.

The numbers in the figure show:

100. Reactive distillation column, 101. Reboiler at the bottom of reactive distillation column, 102. Reactive distillation column overhead condenser

200, the first azeotropic rectifying tower, 201, the reboiler at the bottom of the first azeotropic rectifying tower,

300, the second azeotrope rectifying tower, 301, the reboiler at the bottom of the second azeotrope rectifying tower, 302, the second azeotrope rectifying tower overhead condenser;

400, methanol, glycol and catalyst separation unit;

500. Turbine generator

600, hydraulic turbine,

1. Alkenyl carbonate material, 2. Catalyst material, 3. Methanol material, 4. Methanol and dimethyl carbonate azeotrope, 5. Reactive distillation column bottom material, 6. First steam material , 7, the second steam material, 8, the third steam material, 9, the first azeotropic distillation column bottom material, 10, the DMC product, 12, the methanol and dimethyl carbonate azeotrope after heating Material, 16, Recovery catalyst, 17, Refined glycol product, 18, By-product 2 material, 19, By-product 1 material, 20, Recovered methanol material, 21, Steam stream, 22, Condensate stream, 23, Circulating cooling water inlet 24. Discharge of circulating cooling water.

Detailed ways

The present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the difference between the various components under a certain posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly.

In addition, descriptions such as "first", "second", etc. in the present invention are only for description purposes, and should not be interpreted as indicating or implying their relative importance or implicitly indicating the number of indicated technical features. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically defined.

In the present utility model, unless otherwise expressly specified and limited, the terms "connection", "fixed", etc. should be understood in a broad sense, for example, "fixed" can be a fixed connection, a detachable connection, or an integrated; It can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication between two elements or the interaction relationship between the two elements, unless otherwise expressly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the technical solutions The combination does not exist and is not within the protection scope required by the present invention.

Example 1

Referring to FIG. 1, this embodiment provides a system for co-producing dimethyl carbonate and diol, including a transesterification reaction unit, a methanol and dimethyl carbonate azeotrope separation unit, and methanol, diol and a catalyst Separation unit 400, the transesterification reaction unit is composed of a reactive distillation column 100, and the methanol and dimethyl carbonate azeotrope separation unit is composed of a first azeotropic distillation column 200 and a second azeotropic distillation column 300 Composition, the methanol, glycol and catalyst separation unit 400 is used to realize methanol recovery, glycol refining, catalyst recovery and by-product recovery, and the top of the reactive distillation column 100 is made of methanol and dimethyl carbonate. Boiler material 4 enters the first azeotropic distillation column 200, and material 5 extracted from the bottom of the reactive distillation column of the reactive distillation column 100 enters the methanol, glycol and catalyst separation unit 400. The first azeotropic rectifying tower bottom material 9 of the boiling rectifying tower 200 enters the second azeotropic rectifying tower 300, and the top of the first azeotropic rectifying tower 200 extracts three steam materials rich in methanol, They are the first steam material 6, the second steam material 7, and the third steam material 8, respectively. The first steam material 6 enters the reactive rectification tower 100, and the second steam material 7 enters the reactive rectification tower. In the tower bottom reboiler 101, the third stream of steam material 8 enters the second azeotropic distillation tower bottom reboiler 301; the DMC product 10 is obtained from the bottom of the second azeotropic distillation tower 300.

This embodiment makes full use of the latent heat of the high-pressure steam at the top of the first azeotropic distillation column 200 through such a structural design to maximize energy efficiency and reduce equipment investment.

In this embodiment, the reactive distillation column 100 is used to receive methanol material 3, alkene carbonate material 1 and catalyst material 2, and make the methanol material 3 and alkene carbonate material 1 undergo transesterification.

In this embodiment, the reactive distillation column 100 is used as a reactor, which is selected from a packed column or a tray column, and is divided into a rectification section and a reaction section.

In this embodiment, the reactive rectification tower 100 is a vacuum rectification tower, and the absolute pressure at the top of the tower is less than 80 kPa and greater than 50 kPa. In this way, it is convenient to reduce the reaction temperature, improve the reaction rate of reactive rectification, and at the same time, it is convenient to increase the DMC content at the top of the reactive rectification tower, reduce the methanol circulation flow, and reduce the energy consumption of the separation process of DMC and methanol azeotrope.

In this embodiment, the first azeotropic distillation column 200 is a high-pressure distillation column, and the absolute pressure at the top of the column is greater than 1.3 MPa and less than 2.2 Mpa; it is convenient to increase the methanol vapor temperature at the top of the first azeotropic distillation column 200, As the heat source of the bottom reboiler of the reactive distillation column 100 and the second azeotropic distillation column 300, it is also convenient to further reduce the content of DMC in the top steam, reduce the reflux ratio, and further reduce the energy consumption.

In this embodiment, the second azeotropic rectification tower 300 is a pressurized rectification tower, and the absolute pressure at the top of the tower is greater than 200 kPa and less than 500 kPa, which facilitates the utilization of the latent heat of the vapor at the top of the tower and further improves the energy efficiency.

In this embodiment, a steam turbine generator 500 is installed on the pipeline for the first steam material 6 to enter the reactive distillation column 100 . The steam turbine generator 500 is used to recover the energy of the first steam material 6 for power generation, so that the high-temperature, high-pressure organic steam becomes the low-temperature and low-pressure organic steam and then enters the reactive distillation column 100, which can The energy utilization efficiency is significantly improved, and the steam material directly enters the bottom of the reactive distillation column 100 for direct heating, which saves the indirect heat exchanger and saves the investment.

In this embodiment, the second steam material 7 enters the reboiler 101 at the bottom of the reactive rectification column and becomes a condensed liquid, and then flows back to the top of the first azeotropic rectification column 200 as a reflux The design is convenient for the reactive distillation column 100 to couple and utilize the steam latent heat at the top of the first azeotropic distillation column 200, thereby reducing energy consumption.

In this embodiment, the third steam material 8 enters into the reboiler 301 at the bottom of the second azeotrope rectification tower and turns into a condensed liquid, and then returns to the top of the first azeotrope rectification tower 200 As a reflux liquid, the design facilitates the coupling of the second azeotropic distillation column 300 to utilize the steam latent heat at the top of the first azeotropic distillation column 200, thereby further reducing energy consumption.

In the present embodiment, a liquid turbine 600 is installed on the pipeline for making the bottom material 9 of the first azeotropic rectification tower enter the second azeotropic rectification tower 300 to recover the first azeotropic rectification tower The energy of the high pressure liquid at the bottom of column 200 is used to generate electricity.

In this embodiment, the methanol and dimethyl carbonate azeotrope material 4 first enters the second azeotropic distillation column overhead condenser 302 of the second azeotropic distillation column 300, and utilizes the The latent heat of the column top steam of the second azeotrope rectifying column 300 is preheated and heated to obtain methanol and dimethyl carbonate azeotrope material 12 after heating, and methanol and dimethyl carbonate azeotrope material 12 after heating Re-entering the first azeotropic distillation column 200 can further improve the energy utilization efficiency of the system.

In this embodiment, the top of the reactive rectification tower 100 is provided with a reactive rectification tower overhead condenser 102, and the circulating cooling water feed 23 enters the reactive rectification tower overhead condenser 102 for heat exchange, and flows out of the circulating cooling water out of Material 24, circulating cooling water discharge material 24 is used to flow to the circulating water pump.

In this embodiment, the bottom of the first azeotropic rectification column 200 is provided with a first azeotropic rectification column bottom reboiler 201, and the steam stream 21 enters the first azeotropic rectification column bottom reboiler 201 After heat exchange, a condensate stream 22 flows out, and the condensate stream 22 is used to flow to the boiler.

In this embodiment, the methanol, glycol and catalyst separation unit 400 receives the material 5 extracted from the bottom of the reactive distillation column and separates the recovered methanol material 20, by-product 1 material 19, by-product 2 material 18, refined glycol product 17 and The catalyst 16 is recovered, and the refined glycol product 17 is selected from refined ethylene glycol or propylene glycol products; the by-product 1 material 19 is selected from ethylene glycol monomethyl ether or propylene glycol monomethyl ether; the by-product 2 material 18 is selected from Diethanol or Propylene Glycol.

Example 2

The present embodiment provides a method for co-producing dimethyl carbonate and diol, which is carried out using a system as shown in FIG. 1 , and the method for co-producing dimethyl carbonate and diol includes the following steps:

A, transesterification reaction:

The olefinic carbonate material 1, the methanol material 3 and the catalyst material 2 enter the reactive distillation column 100, and the methanol material 3 and the olefinic carbonate material 1 undergo transesterification under the action of the catalyst material 2. Methanol and dimethyl carbonate azeotrope material 4 is extracted from the top of the tower, material 5 is extracted from the bottom of the reactive rectification tower 100, and material 5 is extracted from the bottom of the reactive rectification tower. Liquid mixtures comprising methanol, ethylene glycol, propylene glycol, ethylene glycol methyl ether, propylene glycol methyl ether, diethylene glycol catalysts or dipropylene glycol catalysts;

B. Separation of methanol and dimethyl carbonate, heat coupling and energy recovery:

The methanol and dimethyl carbonate azeotrope 4 obtained from step A enters the first azeotropic distillation column 200 after being preheated by the second azeotropic distillation column overhead condenser 302, and the first azeotropic distillation column The top of the rectifying tower 200 obtains the first steam material 6, the second steam material 7 and the third steam material 8 rich in methanol, and these steam materials are close to the azeotrope under the corresponding pressure, and the first total steam The bottom of the boiling distillation column 200 obtains the first azeotropic distillation column bottom material 9 that is rich in dimethyl carbonate;

The bottom material 9 of the first azeotropic rectification tower first enters the liquid turbine 600 to reduce the pressure to recover energy, and then enters the second azeotropic rectification tower 300 as a feed;

The reboiler 301 at the bottom of the second azeotropic distillation column uses the third steam material 8 as a heat source for coupling heat utilization, and the third steam material 8 is condensed and returned to the first azeotrope. 200 tops of distillation column are used as reflux liquid;

The first steam material 6 enters the steam turbine generator 500 to recover energy, and after cooling and depressurizing, it enters the lower column body of the reactive distillation column 100 as a methanol circulating feed;

The second stream of steam material 7 enters the reactive rectification tower bottom reboiler 101 of the reactive rectification tower 100 as a heat source, and the coupling heat is utilized, and condensed into a liquid to return to the tower of the first azeotropic rectification tower 200 top as reflow;

The methanol and dimethyl carbonate azeotrope material 4 of the reactive distillation column 100 first enters the second azeotropic distillation column overhead condenser 302 of the second azeotropic distillation column 300, and is utilized by thermal coupling The latent heat of the top steam is preheated and heated up and then enters the first azeotropic distillation column 200;

The refined DMC product 10 is obtained from the bottom of the second azeotropic rectification column 300; in this way, the high pressure and high temperature organic steam at the top of the first azeotropic rectification column or the mechanical energy and latent heat of secondary steam can be effectively and Fully utilized, the energy utilization efficiency is maximized and the primary energy consumption is reduced.

C. Separation of methanol, glycol and catalyst:

The material 5 extracted from the bottom of the reactive distillation column 100 obtained from the bottom of the reactive distillation column enters the methanol, glycol and catalyst separation unit 400, and the recovered methanol material 20, by-product 1, material 19, and by-product 2 are obtained by vacuum distillation. Material 18, refined glycol product 17 and recovery catalyst 16,

Described refined glycol product 17 is selected from refined ethylene glycol or propylene glycol product;

Described by-product 1 material 19 is selected from ethylene glycol monomethyl ether or propylene glycol monomethyl ether;

The by-product 2 material 18 is selected from diethanol or propylene glycol.

The recovered catalyst 16 is allowed to be recycled, and the recovered methanol material 20 is allowed to be returned to the reactive distillation column 100 for recycling.

In this embodiment, the content of dimethyl carbonate in the first steam material 6, the second steam material 7, and the third steam material 8 obtained at the top of the first azeotropic distillation column 200 is less than 5% mol, preferably less than 3% mol.

In this embodiment, the content of dimethyl carbonate in the bottom material 9 of the first azeotropic rectifying tower 200 of the first azeotropic rectifying tower 200 is greater than 50%, preferably greater than 60% mol. Ensure optimized reflux ratio and reduce energy consumption.

In this embodiment, the difference between the temperature of the vapor at the top of the first azeotropic distillation column 200 and the temperature of the liquid at the bottom of the second azeotropic distillation column 300 is 5 to 20°C, which can maximize the improvement of the second azeotropic distillation column. The pressure of the distillation column is used to utilize the latent heat of the top steam.

In this embodiment, in step A, both the olefinic carbonate material 1 and the catalyst material 2 are removed from the reactive rectification tower 100 between the rectification section and the reaction section of the reactive rectification tower 100, and the methanol material 3 Entering the lower part of the reactive distillation column 100, the methanol material 3 and the olefinic carbonate material 1 undergo a transesterification reaction under the action of the catalyst material 2.

In this embodiment, in step A, the methanol material 3 also includes the first steam material 6 that is recycled from the first azeotropic distillation column 200 .

In this embodiment, in step A, the absolute pressure at the top of the reactive distillation column 100 is between 50-80 kPa, and the temperature of the reactive distillation column 100 differs from the temperature of the circulating cooling water by 5-25° C. The optimum temperature is between 10-20°C, and the reflux ratio of the reactive distillation column 100 is between 0.3-1.0, and the optimum is between 0.4-0.6.

In this embodiment, in step A, the alkene carbonate material 1 is selected from one or both of ethylene carbonate and propylene carbonate.

In this embodiment, in step A, the catalyst material 2 is the sodium salt of alcohol, the alcohol is methanol or ethanol, and the sodium salt of alcohol and the solvent are prepared into a solution, and the solvent is selected from methanol, ethylene glycol, One or a mixture of propylene glycol, diethylene glycol or dipropylene glycol.

In this embodiment, in step A, the feed flow rate of the catalyst material 2 is between 1:200 and 1:20 according to the molar ratio of the sodium salt of alcohol to ethylene carbonate or propylene carbonate, preferably 1 :100 to 1:40, which can overcome the influence of trace amounts of water and other impurities such as _CO2 on the catalyst.

In this embodiment, in step B, the first azeotropic distillation column 200 is a high-pressure column, and the absolute pressure at the top of the column is 1.3-2.2 Mpa.

In this embodiment, in step B, the reboiler 201 at the bottom of the first azeotropic rectification tower adopts high-pressure steam or high-temperature heat-conducting oil as the heat source, the steam pressure is between 1.0-2.5MPaG, and the high-temperature heat-conducting oil is used as the heat source. The oil temperature is between 185-225°C.

In this embodiment, in step B, the second azeotropic rectification tower 300 is a pressurized tower, the absolute pressure at the top of the tower is between 200-500kPa, and the reboiler 301 at the bottom of the second azeotropic rectification tower adopts the The third steam material 8 is used as a heat source, and the coupling heat is utilized, and the third steam material 8 is condensed and returned to the top of the first azeotropic distillation column 200 as a reflux liquid.

Example 3

Specific application example 1

Using the system as shown in Figure 1 to co-produce DMC and ethylene glycol, the reactive distillation column 100 includes 10 theoretical plates in the upper rectifying section and 30 theoretical plates in the lower reaction section, ethylene carbonate EC raw material 140 kmol/h, circulating and The supplemented sodium methoxide catalyst is introduced from the 10th theoretical plate together, and the steam generated and depressurized by the steam turbine generator 500 contains methanol (contains DMC2.5%), and enters from the 20th theoretical plate of the reaction section, from methanol, binary The methanol and the supplemented methanol recovered by the alcohol and catalyst separation unit 400 total 330kmol/h, and are introduced from the bottom of the reaction section; the absolute pressure at the top of the reactive distillation column 100 is 0.6 bar, the temperature at the top of the column is 50.9 °C, and the temperature at the bottom of the column is 99 °C. The methanol and dimethyl carbonate azeotrope is extracted from the top of the distillation column 100, and the DMC content is 34.5% wt. Distillation tower 200; Reactive rectification tower bottom extraction material at the bottom of reactive rectification tower contains 196kmol/hr of ethylene glycol, methanol, sodium methoxide catalyst and other components, and enters methanol, glycol and catalyst separation unit 400 for separation;

The first azeotropic distillation column 200 contains 60 theoretical plates, the absolute pressure at the top of the column is 18 bar, the temperature at the top of the column is 161 °C, and the temperature at the bottom of the column is 177 °C. Material, the first steam material 6 is depressurized by the steam turbine generator 500, and the mechanical energy and latent heat can be used to recover mechanical power of 2000kW. After the reduction, the steam enters the column body of the reactive distillation column tower 100, and the second steam material 7 enters the reaction distillation column. The reboiler 101 at the bottom of the distillation column is used as a heat source for coupling, becomes a condensate, and then returns to the top of the first azeotropic distillation column 200 as a reflux liquid, and the third stream of steam material 8 enters the second azeotrope. The reboiler 301 at the bottom of the distillation column is used as a heat source for coupling, and becomes a condensed liquid, which is also returned to the top of the first azeotropic distillation column 200 as a reflux liquid. Methanol 40kmol/h and DMC 144kmol/h are output, and 30kW of mechanical power is recovered by depressurization of the liquid turbine 600, and enters the second azeotropic distillation column 300 as the feed;

The second azeotropic distillation column 300 includes 45 theoretical plates, the absolute pressure at the top of the column is 4 bar, the temperature at the top of the column is 104 °C, and the temperature at the bottom of the column is 140 °C. The feed of the first azeotrope rectification tower 200 is preheated, passed through the second azeotrope rectification tower tower top condenser 302, and the extracted material from the tower top is returned to the first azeotrope rectification tower 200 to recover DMC;

The liquid material at the bottom of the reactive distillation column 100 enters the methanol, glycol and catalyst separation unit 400, and adopts vacuum distillation to obtain the recovered catalyst, recovering methanol 50kmol/h, refined ethylene glycol 137kmol/h, and by-product 1 material (ethylene glycol monomethyl ether) 1kmol/h, by-product 2 materials (diethylene glycol) 1kmol/h; the recovered catalyst is returned to the catalyst preparation step for recycling, and the recovered methanol is returned to the reactive distillation column for recycling;

The total heating energy consumption of reactive distillation column 100, the first azeotropic distillation column 200 and the second azeotropic distillation column 300 in operation is 18.0Gcal/h, and the cooling load is 15.6Gcal/h. The energy consumption of producing 0.689 tons of ethylene glycol is equivalent to 2.60 tons of steam and 176 tons of circulating cooling water (7 degrees temperature rise). Compared with the results disclosed in the existing literature (generally 10-15 tons of steam/ton of DMC), the implementation effect of the present invention is remarkable.

Example 4

Specific application example 2

Using the system as shown in Figure 1 to co-produce DMC and propylene glycol, the reactive distillation column 100 includes 10 theoretical plates in the upper rectifying section and 30 theoretical plates in the lower reaction section, 70 kmol/h of propylene carbonate PC raw material, circulating and supplementary The sodium methoxide catalyst is introduced together from the 10th theoretical plate, and the steam after the steam turbine generator 500 depressurizes and generates electricity contains 425kmol/h of methanol and 10.5kmol/h of DMC, and enters from the 20th theory of the reaction section. The 25kmol/h recovered by the alcohol and catalyst separation unit 400 and the supplemented 140kmol/h, a total of 165kmol/h of high-purity methanol is introduced from the bottom of the reaction section at the 40th theoretical; 50.9 ℃, the bottom temperature of the column is 99 ℃, the reflux ratio is 0.55, the methanol 425kmol/h and the DMC 80kmol/h are extracted from the top of the reactive rectification 100 column, and the DMC mass concentration is 34.5%, which is passed into the first azeotropic distillation column 200; The bottom of the distillation column contains 70kmol/h of ethylene glycol, 25kmol/h of methanol, catalyst and other components, and enters methanol, glycol and catalyst separation unit 400 for separation;

The first azeotropic distillation column 200 includes 40 theoretical plates in the upper rectifying section and 20 theoretical plates in the lower refining section, the absolute pressure at the top of the column is 20 bar, the temperature at the top of the column is 171 °C, and the temperature at the bottom of the column is 182 °C. The first azeotropic distillation The reboiler at the bottom of the tower is heated by 1.8MPa water vapor. There are three steam materials at the top of the tower. The first steam material 6 is depressurized by the steam turbine generator 500 and can recover mechanical power of 1000kW. After depressurization, the steam enters the reactive distillation tower 100 In the tower body, the second steam material 7 contains 510kmol/h of methanol and 12kmol/h of DMC, enters the reboiler 101 at the bottom of the reactive distillation tower to realize thermal coupling utilization, becomes condensed liquid, and then returns to the first azeotrope. The top of the distillation column 200 is used as reflux liquid, and the third steam material 8 steam contains 212 kmol/h of methanol and 5 kmol/h of DMC, and enters the second azeotropic distillation column bottom reboiler 301 to realize thermocouple utilization, and becomes condensed liquid. , also return to the top of the first azeotrope rectifying tower 200 as a reflux liquid, the first azeotrope rectifying tower bottom extraction methanol 20kmol/h and DMC70kmol/h, through the liquid turbine 600 depressurization can be recovered The mechanical power is 15kW, entering the second azeotropic distillation column 300;

The second azeotropic distillation column 300 includes 15 theoretical plates in the upper rectifying section and 30 theoretical plates in the lower refining section, the absolute pressure at the top of the column is 5 bar, the temperature at the top of the column is 112°C, and the temperature at the bottom of the column is 150°C, and high-purity DMC is obtained at the bottom of the column. The product is 70kmol/h, and the vapor material at the top of the tower first preheats the methanol and dimethyl carbonate azeotrope 4 entering the first azeotropic rectification tower 200, and passes through the top of the second azeotropic rectification tower. Condenser 302 is divided into two parts after steam condensation, methanol 50kmol/h and DMC5kmol/h are used as overhead reflux, methanol 20kmol/h and DMC42kmol/h are returned to described first azeotropic distillation column 200 to reclaim DMC;

The liquid material is extracted from the bottom of the reactive distillation column 100, and enters the separation unit 400 for methanol, propylene glycol and catalyst separation, and the recovered catalyst is obtained by vacuum distillation, the recovered methanol is 25kmol/h, the refined propylene glycol is 69kmol/h, and the secondary The product propylene glycol monomethyl ether is 1 kmol/h; the recovered catalyst is returned to the catalyst preparation step for recycling, and the recovered methanol is returned to the reactive distillation column for recycling;

The total heating energy consumption of reactive distillation column 100, the first azeotropic distillation column 200 and the second azeotropic distillation column 300 in operation is 9.1Gcal/h, and the cooling load is 7.82Gcal/h. The energy consumption of producing 0.844 tons of propylene glycol is equivalent to 2.45 tons of steam and 170 tons of circulating cooling water (7 degrees temperature rise). Compared with the results disclosed in the existing literature (generally 10-15 tons of steam/ton of DMC), the implementation effect of the present invention is remarkable.

Example 4

Specific application example 3

The system as shown in the figure is used to co-produce DMC and ethylene glycol. The reactive distillation column 100 includes 10 theoretical plates in the upper rectifying section and 20 theoretical plates in the lower reaction section, 14 kmol/h of ethylene carbonate EC raw material, circulation and supplementation The sodium methoxide is introduced from the 10th theoretical plate together. After the pressure is reduced by the steam turbine 500, the steam contains 100kmol/h of methanol and 3kmol/h of DMC. The recovered 5kmol/h and the supplemented 28kmol/h, a total of 33kmol/h of high-purity methanol is introduced from the bottom of the reaction section at the 40th theoretically; the absolute pressure at the top of the reactive distillation column is 0.7bar, the temperature at the top of the column is 51.4°C, and the temperature at the bottom of the column is 97 ℃, the reflux ratio is 0.7, methanol 100kmol/h and DMC 16.9kmol/h are extracted from the top of the reactive distillation tower 100, and the DMC mass concentration is 32.2%, which is passed into the first azeotropic distillation tower 200; the bottom of the reactive distillation tower contains ethyl alcohol Diol 14kmol/h, methanol 5kmol/h, catalyst and other components enter methanol, glycol and catalyst separation unit 400 for separation;

The first azeotropic distillation column 200 includes 40 theoretical plates, the absolute pressure at the top of the column is 14 bar, the temperature at the top of the column is 155 °C, and the temperature at the bottom of the column is 169 °C. Steam material, the first steam material 6 can recover mechanical power of up to 200kW through the steam turbine generator 500. After the pressure is released, the steam enters the reactive distillation column 100. The second steam material 7 contains methanol 130kmol/h, DMC4kmol/h, after entering the reboiler 101 at the bottom of the reactive distillation column, it becomes a condensed liquid, and then refluxes to the top of the first azeotropic distillation column 200 as a reflux liquid, and the third steam material 8 contains 33kmol of methanol /h and DMC1kmol/h, after entering the reboiler 301 at the bottom of the second azeotropic rectification column, it becomes a condensed liquid, and it also returns to the top of the first azeotropic rectification column 200 as a reflux liquid, the first Methanol 4kmol/h and DMC 14.3kmol/h are extracted from the bottom of the azeotropic distillation column 200, and directly enter the second azeotropic distillation column 300;

The second azeotropic distillation column 300 includes 30 theoretical plates, the absolute pressure at the top of the column is 3 bar, the temperature at the top of the column is 95 °C, and the temperature at the bottom of the column is 128 °C. The feed of the first azeotropic distillation column 200 is divided into two parts after preheating and condensation, methanol 10kmol/h and DMC1kmol/h are refluxed as the top of the tower, and methanol 4kmol/h and DMC0.4kmol/h are returned to the first Azeotropic distillation column 200 reclaims DMC;

The bottom liquid material of the reactive distillation column enters methanol, glycol and catalyst separation unit 400, and adopts vacuum distillation to obtain the recovered catalyst, 0.1 kmol/h of ethylene carbonate, 5 kmol/h of recovered methanol, and purified ethylene glycol. Alcohol 13.7kmol/h, by-product 1 material (ethylene glycol monomethyl ether) 0.1kmol/h, by-product 2 material (diethylene glycol) 0.05kmol/h; the recovered catalyst is returned to the catalyst preparation step for recycling, and the recovered methanol Return to described reactive distillation column 100 for recycling with ethylene carbonate;

The total heating energy consumption of reactive distillation column 100, the first azeotropic distillation column 200 and the second azeotropic distillation column 300 in operation is 2.0Gcal/h, and the cooling load is 1.83Gcal/h, and every ton of DMC products (simultaneously connected The energy consumption of producing 0.689 tons of ethylene glycol is equivalent to 2.89 tons of steam and 206 tons of circulating cooling water (7 degrees temperature rise). Compared with the results disclosed in the existing literature (generally 10-15 tons of steam/ton of DMC), the implementation effect of the present invention is remarkable.

The above description of the embodiments is for the convenience of those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (10)

1. A system for coproducing dimethyl carbonate and dihydric alcohol comprises an ester exchange reaction unit, a methanol and dimethyl carbonate azeotrope separation unit, and a methanol, dihydric alcohol and catalyst separation unit (400),

the ester exchange reaction unit consists of a reaction rectifying tower (100),

the methanol and dimethyl carbonate azeotrope separation unit consists of a first azeotropic distillation tower (200) and a second azeotropic distillation tower (300),

the methanol, glycol and catalyst separation unit (400) is used for realizing methanol recovery, glycol refining, catalyst recovery and byproduct recovery,

it is characterized in that the preparation method is characterized in that,

the top of the reaction rectifying tower (100) adopts a methanol and dimethyl carbonate azeotrope material (4) to enter the first azeotropic rectifying tower (200), the bottom of the reaction rectifying tower (100) adopts a material (5) extracted from the bottom of the reaction rectifying tower to enter a methanol, dihydric alcohol and catalyst separation unit (400),

a first azeotropic distillation tower bottom material (9) of the first azeotropic distillation tower (200) enters the second azeotropic distillation tower (300), three steam materials rich in methanol are extracted from the top of the first azeotropic distillation tower (200) and respectively comprise a first steam material (6), a second steam material (7) and a third steam material (8), the first steam material (6) enters the reactive distillation tower (100), the second steam material (7) enters a reboiler (101) at the bottom of the reactive distillation tower, and the third steam material (8) enters a reboiler (301) at the bottom of the second azeotropic distillation tower;

the bottom of the second azeotropic distillation tower (300) obtains DMC products (10).

2. The system for co-producing dimethyl carbonate and diol according to claim 1, wherein the reactive distillation column (100) is a vacuum distillation column, the first azeotropic distillation column (200) is a high-pressure distillation column, and the second azeotropic distillation column (300) is a pressurized distillation column.

3. A system for co-producing dimethyl carbonate and diol according to claim 1, wherein a turbine generator (500) is installed on the pipeline for feeding the first stream of vapor material (6) into the reactive distillation column (100).

4. The system for co-producing dimethyl carbonate and dihydric alcohol according to claim 1, wherein the second steam material (7) enters a reboiler (101) at the bottom of the reactive distillation column to become a condensate and then flows back to the top of the first azeotropic distillation column (200).

5. The system for co-producing dimethyl carbonate and dihydric alcohol according to claim 1, wherein the third steam material (8) enters a reboiler (301) at the bottom of the second azeotropic distillation tower to become a condensate and then flows back to the top of the first azeotropic distillation tower (200).

6. A system for co-producing dimethyl carbonate and diol according to claim 1, wherein a liquid turbine (600) is installed on the line for the first azeotropic distillation column bottoms (9) to enter the second azeotropic distillation column (300).

7. The system for coproducing dimethyl carbonate and dihydric alcohol according to claim 1, wherein the methanol and dimethyl carbonate azeotrope material (4) firstly enters a second azeotropic distillation tower overhead condenser (302) of the second azeotropic distillation tower (300), the heated methanol and dimethyl carbonate azeotrope material (12) is obtained after the overhead vapor latent heat of the second azeotropic distillation tower (300) is utilized for preheating through thermal coupling, and the heated methanol and dimethyl carbonate azeotrope material (12) enters the first azeotropic distillation tower (200).

8. The system for coproducing dimethyl carbonate and dihydric alcohol according to claim 1, wherein a reaction rectifying tower top condenser (102) is arranged at the top of the reaction rectifying tower (100), and a circulating cooling water feed (23) enters the reaction rectifying tower top condenser (102) for heat exchange and then flows out of a circulating cooling water discharge (24).

9. The system for co-producing dimethyl carbonate and dihydric alcohol according to claim 1, wherein the bottom of the first azeotropic distillation column (200) is provided with a first azeotropic distillation column bottom reboiler (201), and the water vapor stream (21) enters the first azeotropic distillation column bottom reboiler (201) for heat exchange and then flows out of the condensed water stream (22).

10. The system for co-producing dimethyl carbonate and dihydric alcohol according to claim 1, wherein the methanol, the dihydric alcohol and the catalyst separation unit (400) receives a material (5) extracted from the bottom of the reactive distillation tower and separates a recovered methanol material (20), a byproduct 1 material (19), a byproduct 2 material (18), a refined diol product (17) and a recovered catalyst (16),

the refined glycol product (17) is selected from a refined ethylene glycol or propylene glycol product;

the byproduct 1 feed (19) is selected from ethylene glycol monomethyl ether or propylene glycol monomethyl ether;

the byproduct 2 feed (18) is selected from the group consisting of diethyl alcohol or propylene glycol.

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