System and method for producing dimethyl carbonate

Abstract

The invention relates to a system and a method for producing dimethyl carbonate, and belongs to the technical field of organic chemical synthesis. The system comprises a methanol source, an ethylene oxide source, a carbon dioxide source, an EC reactor, a condenser, a gas-liquid separator and a DMC rectifying tower, the methanol source, the ethylene oxide source and the carbon dioxide source are respectively communicated with the EC reactor; a gas phase outlet I of the EC reactor is communicated with a feeding hole of the condenser, and a liquid phase outlet I of the EC reactor is communicated with the DMC rectifying tower; and a gas phase outlet II of the condenser is communicated with the gas-liquid separator. According to the invention, the problems of difficult control of reaction heat, uneven temperature distribution in the reactor, low product conversion rate, low purity and high chromaticity in the ethylene carbonate section in the prior art can be solved. Meanwhile, a reaction path is further optimized, reaction heat of ethylene carbonate synthesis is used as a heat source of a dimethyl carbonate section, and the energy consumption of a reaction system is reduced.

Description

Technical Field

[0001] The invention relates to a system and a method for producing dimethyl carbonate, and belongs to the technical field of organic chemical synthesis. Background Art

[0002] Dimethyl carbonate (DMC) is an important organic compound, which was listed as a non-toxic chemical by Europe in 1992. DMC is used as a raw material to synthesize polycarbonate monomer diphenyl carbonate, isocyanate, carbamate and other chemical products. DMC is non-toxic and contains functional groups such as methyl and carbonyl in its structure. It can replace highly toxic dimethyl sulfate, methyl chloroformate and phosgene for methylation reaction to synthesize many high value-added downstream products, eliminate the pollution of these highly toxic chemicals to the environment, and is widely used in fine chemical fields such as medicine and pesticides.

[0003] DMC has the characteristics of high dielectric constant, high electrochemical stability and low viscosity, and is the main solvent for lithium-ion battery electrolyte. DMC has the advantages of high oxygen content, high octane number, good gasoline / water partition coefficient, low toxicity and rapid biodegradation, and is an excellent gasoline and diesel additive. Therefore, DMC is widely used in the fields of materials and chemical industry and has high industrial application value. DMC is divided into two categories according to purity: industrial grade (99.9%) and battery grade (above 99.999%). The production process requirements of battery-grade DMC are higher.

[0004] At present, the ester exchange method is still the main production method in the DMC production process and has been applied in industry. This method first uses CO2 and propylene oxide (PO) or ethylene oxide (EO) to synthesize propylene carbonate (PC) or ethylene carbonate (EC), and then PC or EC is ester exchanged with methanol to obtain DMC and 1,2-propylene glycol (PG) or ethylene glycol (EG). However, this production process has the following technical difficulties: First, the reactions for synthesizing PC or EC are all exothermic reactions, and they are strongly exothermic reactions, especially the reaction between EO and CO2, which releases more heat. If the heat of the reaction is not removed in time, the reactor will overheat and cause safety accidents. Secondly, the ester exchange alcoholysis of EC and methanol to produce DMC is a reversible reaction, which is carried out in a reaction distillation tower. During the reaction process, DMC needs to be removed in time to improve the equilibrium conversion rate. The molar ratio of methanol to EC is usually 10:1 to 15:1. Methanol is greatly in excess. The purpose of the excess methanol is to form an azeotrope with the product DMC and go out from the top of the reaction distillation tower to break the balance of the transesterification reaction, thereby increasing the conversion rate of PC (or EC). The excess methanol is to be vaporized in the reaction distillation tower, and the energy for vaporization comes from the steam in the tower kettle reboiler to provide heat. This makes it extremely difficult to control the reaction temperature. Too high a temperature can easily lead to the intensification of side reactions, resulting in a decrease in the yield and purity of EC or PC.

[0005] Chinese invention patent disclosure CN113387811A discloses an energy-saving and consumption-reducing method for producing dimethyl carbonate by the transesterification method. The heat released in the process of synthesizing propylene carbonate (or ethylene carbonate) by reacting propylene oxide (or ethylene oxide) with CO2 is removed by gasifying the reaction heat with methanol through a kettle evaporator, and the excess methanol enters the transesterification reaction distillation tower in the gas phase, reducing the steam usage in the tower kettle reboiler and the heat load of the reaction distillation tower, thereby achieving energy-saving effects. However, this invention only focuses on energy saving and consumption reduction in the DMC section, and does not involve the control of the reaction heat in the EC section. In fact, the reaction process control level of the EC section is more important to the final DMC yield and purity. Summary of the invention

[0006] The problems to be solved by the present invention are as follows: 1) timely removal of reaction heat in the EC section; 2) process control in the EC section; 3) thermal integration of the EC / DMC section, etc. The present invention introduces a solvent into the reaction system and controls the temperature fluctuation of the reaction process by means of heat transfer through solvent phase change, gasification, evaporation and heat transfer. The introduced solvent can further dilute the reaction raw materials, reduce the intensity of the reaction, and improve the yield and purity of the EC product.

[0007] The system for producing dimethyl carbonate comprises: a methanol source, an alkylene oxide source, a carbon dioxide source, an olefin carbonate reactor, a condenser, a gas-liquid separator and a DMC distillation tower; the olefin carbonate reactor has a gas phase outlet I and a liquid phase outlet I; the condenser has a gas phase outlet II and a condensation reflux port II; the methanol source, the alkylene oxide source and the carbon dioxide source are respectively connected to the EC reactor; the gas phase outlet I is connected to the feed port of the condenser, and the liquid phase outlet I is connected to the DMC distillation tower; the gas phase outlet II is connected to the gas-liquid separator; and the condensation reflux port II is connected to the EC reactor.

[0008] The methanol source described in the present invention is a feed pipeline or a storage tank that can provide methanol.

[0009] The alkylene oxide source of the present invention is a feed pipeline or a storage tank that can provide alkylene oxide.

[0010] The carbon dioxide source described in the present invention is a feed pipeline or a storage tank that can provide carbon dioxide.

[0011] Optionally, the methanol source is provided with two parallel branches, namely branch P1 and branch P2; branch P1 is connected to the EC reactor; branch P2 is connected to the DMC distillation tower.

[0012] Optionally, the gas phase outlet I is located at the top of the EC reactor, and the liquid phase outlet I is located at the upper part of the olefin carbonate reactor.

[0013] Optionally, the gas phase outlet II is located at the top of the condenser, and the condensation reflux port II is located at the bottom of the condenser.

[0014] Optionally, the alkylene oxide source contains ethylene oxide and / or propylene oxide.

[0015] Optionally, the olefin carbonate is ethylene carbonate and / or propylene carbonate.

[0016] Optionally, the methanol source is further provided with a parallel branch P3; the branch P3 serves as a cold source for the condenser.

[0017] Optionally, P3 is connected to the shell side of the condenser, and the shell side outlet is connected to the DMC distillation tower; the gas phase outlet I of the olefin carbonate reactor is connected to the tube side of the condenser.

[0018] Optionally, the system further comprises a buffer tank; the methanol source and the alkylene oxide source are respectively connected to the buffer tank, and the buffer tank is connected to the EC reactor.

[0019] Optionally, the system further comprises a purification unit, and the gas phase outlet of the DMC distillation tower is connected to the purification unit.

[0020] The reaction system of the present invention mainly consists of ethylene carbonate synthesis, tail gas condensation section and dimethyl carbonate synthesis section. Ethylene oxide and carbon dioxide are used as reactants, and methanol is used as solvent. They enter the EC reactor from the bottom of the reactor for reaction. The reaction adopts a solid catalyst, and carbon dioxide is continuously introduced. The reaction is a strong exothermic reaction. The heat generated vaporizes the solvent methanol, which is discharged from the top of the reactor together with the unreacted carbon dioxide and enters the condenser at the top of the reactor. Part of the condensable gas is condensed and returned to the reactor. The non-condensable gas is further separated and absorbed in a separation tank and discharged into the tail gas absorption system. The separated liquid returns to the reactor. The product of the reaction, crude ethylene carbonate, overflows from the upper part of the reactor and enters the dimethyl carbonate reaction distillation tower as a raw material. It undergoes an ester exchange reaction with methanol in the reaction distillation tower to generate dimethyl carbonate. The methanol entering the dimethyl carbonate device to participate in the reaction is first used as a cold source for the condenser of the ethylene carbonate section, and enters the reaction distillation tower after heat exchange with the gas evaporated from the ethylene carbonate section.

[0021] A method for producing dimethyl carbonate, comprising:

[0022] S1 alkylene oxide, methanol, and CO2 enter the olefin carbonate reactor and react under the action of catalyst I to obtain gas phase products and a liquid phase containing EC;

[0023] The S2 gas phase product flows out of the olefin carbonate reactor and enters the condenser for condensation, and the condensed condensable gas flows back to the EC reactor;

[0024] The liquid phase containing olefin carbonate generated in the S3 EC reactor enters the DMC reaction distillation tower;

[0025] In the S4 DMC reaction distillation tower, olefin carbonate and methanol undergo transesterification and alcoholysis reaction under the action of catalyst II to generate DMC, and the gas phase containing DMC is extracted from the distillation tower.

[0026] Optionally, in S2, methanol enters the condenser as a cold source, and the gas phase product exchanges heat with the methanol in the condenser.

[0027] Optionally, methanol enters the DMC reactive distillation tower as a reaction feedstock;

[0028] Optionally, catalyst I and catalyst II are both heterogeneous catalysts; preferably, catalyst I is a halogen-type hydroxyimidazole resin; preferably prepared by the method of Example 1 in CN105503608B); preferably, catalyst II is a carboxyimidazole resin; preferably prepared by the method of Example 1 in CN105503519B.

[0029] Preferably, in the EC reactor, the temperature fluctuation range during the reaction is 3-4°C.

[0030] Optionally, in the olefin carbonate reactor, the molar ratio of alkylene oxide to methanol is 1:1 to 1:10.

[0031] Optionally, the reaction temperature of the olefin carbonate reactor is 100-160°C.

[0032] Optionally, the operating pressure of the olefin carbonate reactor is 2.0 to 6.0 MPa.

[0033] Optionally, the minimum flow rate of the branch P3 (methanol feed) in the condenser is controlled by the temperature of the gas phase outlet I of the EC reactor, and the outlet temperature is 40-100°C.

[0034] Optionally, the reaction temperature in the DMC reaction distillation tower is 60-100°C; the tower top temperature is 67.8-111°C.

[0035] Optionally, the operating pressure in the DMC reaction distillation tower is 0.1-0.5 MPa; the tower top pressure is 0.03-0.4 MPag.

[0036] Optionally, the reflux ratio in the DMC reaction distillation tower is 0.05-10.

[0037] Optionally, the molar ratio of methanol to olefin carbonate in the DMC reaction distillation tower is 6:1 to 15:1.

[0038] Optionally, the conditions of the gas-liquid separator are: temperature of 40-100°C and pressure of 2.0-8.0 MPa. The amount of branch P1 - the ratio of ethylene oxide to methanol is 1:1-1:10; the amount of branch P2 - the molar ratio of methanol to olefin carbonate is 6:1-15:1; the amount of branch P3 - controlled by the temperature of the gas phase outlet I of the ethylene carbonate reactor. Preferably, the flow ratio of P1, P2, and P3 = 1-10:0-12:3-10.

[0039] The present invention provides a process method in which ethylene oxide (preferably ethylene oxide) and carbon dioxide are catalyzed in a methanol solvent to generate ethylene carbonate, and the generated ethylene carbonate and methanol undergo an ester exchange alcoholysis reaction to generate dimethyl carbonate, which mainly solves the problems of difficult control of reaction heat in the ethylene carbonate section in the prior art, uneven temperature distribution in the reactor, low product conversion rate, low purity and high chroma. At the same time, the reaction path is further optimized, and the reaction heat of ethylene carbonate synthesis is used as a heat source for the dimethyl carbonate section to reduce the energy consumption of the reaction system. The present invention uses solvent phase change vaporization for heat exchange, which can effectively control the temperature fluctuation of the ethylene carbonate reaction device. At the same time, carbon dioxide is used to flow continuously in the reaction system, which can make the flow field distribution in the reactor more uniform, eliminate the temperature difference in the reactor, improve the overall reaction conversion rate and selectivity, improve the product purity and reduce the product chroma. Another advantage of the present invention is the rational use of heat. The reaction heat of ethylene carbonate is used as a heat source for the dimethyl carbonate section, which can reduce the energy consumption of the dimethyl carbonate section, realize the rational use of energy, and the co-production process is more green and economical.

[0040] (1) The temperature of the reactor has a great influence on the reaction. A temperature difference of 1°C is very obvious. The existing technology mainly adopts external circulation heat removal, jacket heat removal and cooling coil heat removal. Affected by the operation and changes in external conditions, it will significantly increase the by-products and make the impurity content in the product high. The temperature control of the reactor of the present invention is easier and more stable, with small temperature fluctuations, less by-products, low impurity content, and high product purity.

[0041] (2) In the prior art, the gas phase in the reactor is basically not circulated and a compensation method is adopted. The present invention adopts continuous gas flow in and out, which can increase the gas-liquid dispersion in the reaction system and make the reaction temperature more uniform.

[0042] (3) In the process of the present invention, methanol is used as a solvent in the ethylene carbonate section and does not need to be separated from the product; in the dimethyl carbonate section, methanol is used as a reaction raw material for reaction and also as an azeotropic agent to azeotropically extract the generated dimethyl carbonate, thereby reducing energy consumption and equipment investment.

[0043] (4) The present invention introduces a portion of the methanol that needs to be supplemented in the dimethyl carbonate section to the ethylene carbonate section as a cold source for heat exchange with the high-temperature steam at the top of the ethylene carbonate reactor. Heat exchange is performed in the condenser, which can fully utilize the reaction heat of the ethylene carbonate section. The methanol is overheated and enters the DMC reaction distillation tower, further reducing the overall energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The process flow chart of the present invention for synthesizing carbonate is as follows:

[0045] Figure 1 1 buffer tank, 2 EC reactor, 3 condenser, 4 gas-liquid separator, 5 DMC distillation tower, 6 purification unit

[0046] Reaction stream: 101 is methanol, 102 is reaction raw material (mainly methanol and ethylene oxide), 103 is gas phase outlet stream of the reactor (mainly methanol, CO2 and a small amount of EC, EO), 104 is non-condensable gas CO2, 105 is condensable gas reflux, 106 is reaction product I (mainly EC and solvent methanol), mainly (EC+methanol), 107 is methanol, which is used as cold stream of the reactor at the top of the reactor, 108 is methanol after heat exchange, 109 is methanol entering the DMC distillation tower, 110 is the top discharge of the distillation tower, 111 is the top product of the purification unit refluxed to the DMC distillation tower, 112 is the DMC product discharge; 113 is the bottom of the tower. DETAILED DESCRIPTION

[0047] Method for producing carbonate ester: adopt the following steps

[0048] S1 Fresh alkylene oxide and methanol are mixed in the buffer tank and enter the EC reactor (bubbling bed reactor) from the bottom. CO2 enters the EC reactor through the bottom and reacts under the action of the catalyst.

[0049] The gas phase evaporated by the exothermic reaction of S2 is condensed by the condenser on the top of the EC reactor, and the condensed condensable gas returns to the EC reactor to continue to participate in the reaction

[0050] The EC and solvent methanol generated in the S3 EC reactor are discharged from the upper overflow of the reactor and enter the DMC reaction distillation tower as raw materials for synthesizing DMC.

[0051] Methanol flows through the shell of the S4 condenser. After heat exchange between the condenser and the EC reactor, methanol enters the DMC reaction distillation tower as a reaction raw material.

[0052] In the DMC reaction distillation tower S5, EC and methanol undergo ester exchange and alcoholysis reaction under the action of the catalyst to generate DMC. DMC and methanol generate the lowest azeotropic product which is distilled out from the top of the tower for further purification.

[0053] The present invention will be further described below by way of examples, but are not limited thereto.

[0054] Catalyst I in the embodiment is a halogen-type hydroxyimidazole resin, which is prepared by the method of Example 1 in CN105503608B; Catalyst II is a carboxyimidazole resin, which is prepared by the method of Example 1 in CN105503519B.

[0055] Example 1 System for producing dimethyl carbonate

[0056] like Figure 1 As shown, methanol (MEOH) material is connected to three parallel branches, namely branch 101, branch 107 and branch 109, and the flow ratio of the three branches is 4:1:5.

[0057] The methanol and fresh ethylene oxide (EO) from the 101 branch are mixed in the buffer tank 1 and enter the EC reactor 2 from the bottom of the EC reactor 2 as the reaction raw material 102, and the gaseous CO2 enters the EC reactor 2 from the lower part of the reactor 2.

[0058] In the EC reactor 2, EO and CO2 react under the action of the catalyst to produce ethylene carbonate (EC). The reaction releases a large amount of heat, causing the solvent methanol to evaporate, and the heat is taken out. The evaporated gas phase is condensed by the condenser 3 at the top of the reactor 2, and the gas phase enters the tube side of the condenser 3. After heat exchange with the shell side, the condensed condensable gas (methanol, EO) returns to the EC reactor 2 to continue to participate in the reaction. The reaction product I 106 (mainly EC and solvent methanol) generated in the reactor 2 is discharged from the upper overflow of the EC reactor 2 and enters the DMC distillation tower 5 as a raw material for preparing dimethyl carbonate (DMC).

[0059] The methanol from the 107 branch enters the shell side of the condenser, and after heat exchange with the gas phase in the tube side, enters the DMC distillation tower 5 as the heat-exchanged methanol 108 as a raw material for preparing DMC.

[0060] The gas phase logistics 103 (mainly methanol, CO2 and a small amount of EC, EO) flowing out of the top of the condenser is separated by the gas-liquid separator 4, the gas phase 104 (non-condensable gas carbon dioxide) 104 is discharged from the top of the gas-liquid separator, and the liquid phase 105 (condensable gas, mainly methanol and EO) returns to the buffer tank with a temperature of 40-100°C and a pressure of 2.0-8.0MPa.

[0061] The methanol from branch 109 enters the DMC distillation tower 5. In the DMC distillation tower 5, EC and methanol undergo ester exchange and alcoholysis reaction under the action of the catalyst to generate DMC. DMC and methanol generate the lowest azeotropic mixture, i.e., the top discharge 110 of the DMC distillation tower (the main components are methanol + DMC). The top discharge 110 is extracted from the DMC distillation tower 5 and is further purified by the purification unit 6 (the purification is to separate methanol and DMC. The purification adopts a multi-tower distillation mode. According to the required purity requirement of DMC, a combination of multiple distillation towers is used for purification. DMC is extracted as a product (112), and methanol is recycled (111)). Finally, a DMC product is obtained. 113 is the material extracted from the bottom of the tower, and the main components are methanol, ethylene glycol, and diethylene glycol.

[0062] Example 2 Method for producing dimethyl carbonate

[0063] according to Figure 1 The process flow of synthesizing carbonate is described. Fresh ethylene oxide and methanol are mixed in the buffer tank and enter the EC reactor from the bottom of the EC reactor. The molar ratio of EO to methanol in the EC reactor is 1:4. Gas phase CO2 enters the EC reactor from the bottom of the EC reactor and reacts under the action of catalyst I. The reaction temperature is 120℃ and the reaction pressure is 2.2MPag. The reaction releases a large amount of heat, causing the solvent methanol to evaporate and the heat is taken out. The gas phase outlet temperature of the EC reactor is 120℃, and the temperature fluctuation range of the reaction process is 118.1~122.2℃. The evaporated gas phase is condensed by the condenser at the top of the EC reactor, and the gas phase goes through the pipe side. The temperature of the condensed condensable gas is controlled to be 40℃ and returns to the EC reactor to continue to participate in the reaction. Methanol goes through the shell side of the condenser. After the methanol exchanges heat with the evaporated gas phase from the condenser, it enters the DMC distillation tower as a reaction raw material. EC (sampling and analysis of EC product molar yield of 98.05%, analysis using the chromatographic analysis method commonly used in the art, impurity ethylene glycol content of 0.0305%, diethylene glycol content of 0.0150%) and solvent methanol are discharged from the upper part of the reactor and enter the DMC distillation tower as raw materials for generating DMC. In the DMC distillation tower, EC and methanol undergo ester exchange alcoholysis reaction under the action of catalyst II to generate DMC, the reaction temperature is 88°C, the tower top temperature is 67.8°C, the tower top pressure is 0.03MPag, the reflux ratio is 0.05, and the molar ratio of methanol to EC is 1:10; DMC and methanol generate the lowest azeotropic product, which is distilled from the tower top and further purified in the purification unit, and finally the total yield of DMC and EG products is 98.04wt%, and the purity of DMC is 99.99%.

[0064] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0065] Comparative Example 1 Method for producing dimethyl carbonate

[0066] according to Figure 1 The process flow for synthesizing carbonate esters described herein adopts the method of Example 2, the only difference being that methanol only passes through 101 and 109, and does not pass through 107 and 108.

[0067] Fresh ethylene oxide and methanol are mixed in the buffer tank and enter EC reactor 2 from the bottom of EC reactor. The molar ratio of EO to methanol in EC reactor 2 is 1:4. Gas phase CO2 enters EC reactor 2 from the bottom of EC reactor and reacts under the action of catalyst I. The reaction temperature is 120°C, the temperature fluctuation range of the reaction process is 118.1-122.2°C, and the reaction pressure is 2.2MPag. The reaction releases a large amount of heat, causing the solvent methanol to evaporate and the heat is taken out. The gas phase outlet temperature of EC reactor 2 is 120°C. The evaporated gas phase is condensed by condenser 3 at the top of EC reactor 2. The gas phase goes through the tube side, and the temperature of the condensed condensable gas is controlled to be 40°C, and returns to EC reactor 2 to continue to participate in the reaction. The shell side of condenser 3 uses public engineering circulating cooling water to remove heat (methanol does not go to 107 and 108).

[0068] EC (sampling and analysis of EC product molar yield of 98.03%, analysis using the chromatographic analysis method commonly used in the art, impurity ethylene glycol content of 0.0308%, diethylene glycol content of 0.0154%) and solvent methanol generated in EC reactor 2 overflow from the upper part of the reactor and enter DMC distillation tower 5 as raw materials for generating DMC. In DMC distillation tower 5, EC and methanol undergo ester exchange alcoholysis reaction under the action of catalyst II to generate DMC, the reaction temperature is 88°C, the tower top temperature is 67.8°C, the tower top pressure is 0.03MPag, the reflux ratio is 0.05, and the molar ratio of methanol to EC is 1:10; DMC and methanol generate the lowest azeotropic product, which is distilled from the tower top and further purified in the purification unit, and finally the total yield of DMC and EG products is 98.01wt%, and the purity of DMC is 99.99%. The energy consumption is increased by 10.02% compared with Example 1 (the energy consumption is the increased cooling capacity of the utility circulating cooling water and the heat required for evaporating methanol in the bottom of the DMC distillation tower).

[0069] Comparative Example 2 Method for producing dimethyl carbonate

[0070] The method of Example 2 is adopted, the only difference is that methanol only goes through 109, and does not go through 101, 107 and 108.

[0071] Fresh ethylene oxide enters the EC reactor from the bottom of the EC reactor 2 (methanol does not enter the EC reactor 2, methanol only goes to 109, not 101, 107, 108), gaseous CO2 enters the EC reactor 2 from the bottom of the EC reactor 2, and reacts under the action of the catalyst I, the reaction temperature is 120°C, and heat is removed by a jacket, or a cooling coil, or an external circulation (the liquid in the EC reactor 2 is extracted out of the reactor for heat removal, the liquid includes liquid ethylene oxide, EC and gaseous CO2 dissolved in liquid ethylene oxide), the temperature fluctuation range of the reaction process is 115.2-126.3°C, the reaction pressure is 2.2MPag, and the EC generated in the EC reactor 2 is discharged from the overflow of the upper part of the reactor (sampling and analysis of the EC product molar yield is 96.83%, and the analysis adopts the chromatographic analysis method commonly used in the field, and the impurity ethylene glycol content is 0.0624%, and the diethylene glycol content is 0.0335%). Enter the DMC distillation tower 5 as a raw material for generating DMC. In the DMC distillation tower 5, EC and methanol undergo ester exchange alcoholysis reaction under the action of catalyst II to generate DMC, the reaction temperature is 88°C, the tower top temperature is 67.8°C, the tower top pressure is 0.03MPag, the reflux ratio is 0.05, and the molar ratio of methanol to EC is 1:10; DMC and methanol generate a minimum azeotropic product which is distilled from the top of the tower and further purified in the purification unit, and finally the total yield of DMC and EG products is 97.64wt%, and the purity of DMC is 98.97%.

[0072] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0073] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. 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.

Claims

1. A system for producing dimethyl carbonate, comprising: Methanol source, alkylene oxide source, carbon dioxide source, olefin carbonate reactor, condenser, gas-liquid separator and DMC distillation tower; The olefin carbonate reactor has a gas phase outlet I and a liquid phase outlet I; The condenser has a gas phase outlet II and a condensation reflux outlet II; A methanol source, an alkylene oxide source, and a carbon dioxide source are respectively connected to an olefin carbonate reactor; The gas phase outlet II is connected to the gas-liquid separator; the condensation reflux port II is connected to the carbonate olefin reactor; The gas phase outlet I is connected to the feed inlet of the condenser, and the liquid phase outlet I is connected to the DMC distillation tower.

2. The system for producing dimethyl carbonate according to claim 1, characterized in that: The methanol source is provided with two parallel branches, namely branch P1 and branch P2; The branch P1 is connected to the olefin carbonate reactor; Branch P2 is connected to the DMC distillation tower; And / or, the gas phase outlet I is located at the top of the olefin carbonate reactor, and the liquid phase outlet I is located at the upper part of the olefin carbonate reactor; And / or, the gas phase outlet II is located at the top of the condenser; the condensation reflux port II is located at the bottom of the condenser; and / or, the alkylene oxide source contains ethylene oxide and / or propylene oxide; And / or, the olefin carbonate is ethylene carbonate and / or propylene carbonate.

3. The system for producing dimethyl carbonate according to claim 1 or 2, characterized in that: The methanol source is also provided with a parallel branch P3; the branch P3 serves as a cold source for the condenser; Preferably, P3 is connected to the shell side of the condenser, and the shell side outlet is connected to the DMC distillation tower; the gas phase outlet I of the olefin carbonate reactor is connected to the tube side of the condenser.

4. The system for producing dimethyl carbonate according to any one of claims 1 to 3, characterized in that: The system further comprises a buffer tank; the methanol source and the alkylene oxide source are respectively connected to the buffer tank, and the buffer tank is connected to the olefin carbonate reactor.

5. The system for producing dimethyl carbonate according to claim 1, characterized in that: The system further comprises a purification unit, and the gas phase outlet of the DMC distillation tower is connected to the purification unit.

6. A method for producing dimethyl carbonate, characterized in that include: S1 alkylene oxide, methanol, and CO2 enter the olefin carbonate reactor and react under the action of catalyst I to obtain a gas phase product and a liquid phase containing olefin carbonate; The S2 gas phase product flows out of the olefin carbonate reactor and enters the condenser for condensation, and the condensed condensable gas flows back into the olefin carbonate reactor; The liquid phase containing olefin carbonate generated in the S3 olefin carbonate reactor enters the DMC reaction distillation tower; In the S4 DMC reaction distillation tower, olefin carbonate and methanol undergo transesterification and alcoholysis reaction under the action of catalyst II to generate DMC, and the gas phase containing DMC is extracted from the distillation tower.

7. The method according to claim 6, characterized in that include: In S2, methanol enters the condenser as a cold source, and the gas phase product exchanges heat with the methanol in the condenser; and / or, methanol enters the DMC reaction distillation tower as a reaction raw material; And / or, both catalyst I and catalyst II are heterogeneous catalysts; preferably, the catalyst I is a halogen-type hydroxyimidazole resin; preferably, the catalyst II is a carboxyimidazole resin.

8. The method according to claim 6 or 7, characterized in that: In the EC reactor, the temperature fluctuation during the reaction is 3-4°C; and / or, in the olefin carbonate reactor, the molar ratio of alkylene oxide to methanol is 1:1 to 1:10; And / or, the reaction temperature of the olefin carbonate reactor is 100-160°C. And / or, the operating pressure of the olefin carbonate reactor is 2.0 to 6.0 MPa; And / or, the minimum flow rate of the branch P3 in the condenser is controlled by the temperature of the gas phase outlet I of the carbonate olefin reactor, and the outlet temperature is 40-100°C.

9. The method according to any one of claims 6 to 8, characterized in that: The reaction temperature in the DMC reaction distillation tower is 60-100°C; the tower top temperature is 67.8-111°C; and or, the operating pressure in the DMC reaction distillation tower is 0.1-0.5 MPa; the tower top pressure is 0.03-0.4 MPag; and or, the reflux ratio in the DMC reaction distillation tower is 0.05 to 10; And or, the molar ratio of methanol to olefin carbonate in the DMC reaction distillation tower is 6:1 to 15:

1.

10. The method according to any one of claims 6 to 9, characterized in that: The conditions of the gas-liquid separator are: temperature of 40-100°C and pressure of 2.0-8.0 MPa.

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