CN-121135582-B - Method for preparing dimethyl carbonate

Abstract

The invention belongs to the technical field of organic synthesis, and relates to a method for preparing dimethyl carbonate. The method takes a eutectic solvent (DES) as a catalyst, and catalyzes CO 2 to react with methanol to prepare dimethyl carbonate in the presence of an organic solvent and a dehydrating agent, wherein the reaction condition is that the initial pressure of CO 2 is 1-6MPa, the temperature is 100-120 ℃ and the time is 4-10h. Standing for layering after reaction, directly recycling the lower DES layer after centrifugal separation of a dehydrating agent, rectifying an upper product phase to remove an organic solvent, thus obtaining the product dimethyl carbonate, and recycling the organic solvent. The invention is characterized in that the DES-dehydrating agent system can realize high-yield and high-purity synthesis of dimethyl carbonate, solves the problems of difficult recovery of catalyst, more byproducts, low yield and the like in the traditional method, has the advantages of recyclable catalyst and solvent, low cost and simple and convenient operation, and is suitable for industrial production.

Inventors

• Geng sai
• LIU YUE
• ZHANG ZHANYU
• YU HAILONG
• WANG HUIHUI
• SUN LULIN
• GONG WENBO
• LIU SHIWEI
• YIN JIALI
• WU SHUANG
• LIU YUFEI
• LAO JINGYI

Assignees

• 青岛科技大学

Dates

Publication Date

20260508

Application Date

20250811

Claims (4)

1. 1. A method for preparing dimethyl carbonate is characterized by comprising the following steps of taking a eutectic solvent DES as a catalyst, catalyzing CO 2 to react with methanol in the presence of an organic solvent and a dehydrating agent to prepare dimethyl carbonate, standing and layering after the reaction is finished to obtain a lower DES phase and an upper product phase containing the organic solvent, recycling the lower DES phase after centrifugally separating the dehydrating agent, directly recycling the lower DES phase, rectifying the upper product phase containing the organic solvent to remove the organic solvent to obtain the product dimethyl carbonate, and recycling the rectified organic solvent; The DES consists of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is selected from one of choline chloride, polyethylene glycol and glycerin, the hydrogen bond donor is selected from one of trifluoro methane sulfonic acid, trichloroacetic acid and p-toluenesulfonic acid, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-1:3.
2. 2. The method for preparing dimethyl carbonate according to claim 1, wherein the conditions of the catalytic reaction are that the initial pressure of CO 2 is 1-6MPa, the molar ratio of methanol to a dehydrating agent is 1:1-1:3, the molar ratio of methanol to DES is 1:2-1:4, the reaction temperature is 100-120 ℃ and the reaction time is 4-10h.
3. 3. The method for preparing dimethyl carbonate according to claim 1, wherein the organic solvent is selected from one of toluene, methyl tertiary butyl ether and methylcyclohexane.
4. 4. The method for preparing dimethyl carbonate according to claim 1, wherein the dehydrating agent is selected from one of 4A molecular sieve, anhydrous magnesium sulfate and silica gel, and is recyclable after drying and dehydration.

Description

Method for preparing dimethyl carbonate Technical Field The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing dimethyl carbonate by catalyzing CO 2 and methanol to react in the presence of an organic solvent by taking DES as a catalyst. Background Dimethyl carbonate (DMC) is used as an important green chemical raw material, and the molecular structure of the DMC has functional groups such as carbonyl, methyl, methoxy and the like, has good reactivity and biocompatibility, and is widely applied to the fields of medicines, pesticides, coatings, lithium battery electrolyte, fuel additives and the like. The traditional preparation method has obvious defects, such as that the gas and the methanol are used as raw materials, the process is mature, but phosgene has extremely toxic and has been listed as a limiting process, the methanol oxidative carbonylation method is divided into a liquid phase method and a gas phase method, methanol, CO and O 2 are used as raw materials, copper catalysts such as CuCl are used for reaction, cl - loss causes the problems of quick deactivation of the catalysts, difficult separation of the catalysts and products, aggravated equipment loss and corrosion of byproduct HCl and the like, the transesterification method uses cyclic carbonates such as Ethylene Carbonate (EC) and methanol for reaction, the raw materials are high in cost, high-pressure reaction conditions are required, and a large amount of alkylene glycol is required as byproducts, the urea alcoholysis method uses urea and methanol as raw materials, and the raw materials react under the action of heterogeneous or homogeneous catalysts such as dibutyl dimethyl stannane, tetraphenyl tin and the like, the raw materials are low in price, but the reaction needs high temperature and high pressure, the byproduct ammonia is difficult to treat, and the product purity is low. In the existing catalytic system, the catalytic activity of an Ionic Liquid (ILs) catalyst, such as EMIM-BF4, is fast to decrease, the separation process is complex, a metal oxide catalyst, such as China patent CN106478421A, takes a multi-component composite metal oxide as a catalyst, and catalyzes alkylene glycol and urea to generate cyclic carbonate and ammonia through alcoholysis reaction, the cyclic carbonate and methanol are subjected to transesterification reaction to prepare dimethyl carbonate, nitrogen impurities are required to be removed before the transesterification reaction, the reaction is complex and the energy consumption is high, a supported catalyst, such as China patent CN107649158B, takes porous spherical active alumina as a carrier, loads potassium carbonate and sodium carbonate on the porous spherical active alumina, the preparation is complex, and the requirement of reaction equipment is high. According to the invention, through the synergistic effect of the DES and the organic solvent, the unique hydrogen bond network of the DES can activate CO 2 and methanol simultaneously, the product yield is stabilized to be more than 91.5%, the purity is more than or equal to 99.2%, and the method is obviously superior to the prior art. Based on the method, the invention provides a method for preparing the dimethyl carbonate by reacting CO 2 with methanol in the presence of an organic solvent by adopting DES as a catalyst, the reaction condition is mild, the initial pressure of CO 2 is 1-6MPa, the reaction temperature is 100-120 ℃, the condition of high temperature and high pressure is not needed, the requirements on reaction equipment and energy consumption are reduced, and the synergistic effect of DES and the organic solvent can realize the efficient recovery and recycling of the catalyst by standing and layering and centrifugal separation after the reaction is finished, the product and the organic solvent are separated by rectification and recycling, and the production cost is obviously reduced. The method realizes the high-yield and high-purity synthesis of the dimethyl carbonate, has simple and convenient process operation and has good industrial application prospect. Disclosure of Invention The invention aims to provide a method for synthesizing dimethyl carbonate with high efficiency and high selectivity. Based on the above, the invention relates to a method for preparing dimethyl carbonate, which is characterized in that DES is used as a catalyst, CO 2 and methanol are catalyzed to react in the presence of an organic solvent to prepare dimethyl carbonate, wherein the initial pressure of CO 2 is 1-6MPa, the molar ratio of methanol to a dehydrating agent is 1:1-1:3, the molar ratio of methanol to DES is 1:2-1:4, the reaction temperature is 100-120 ℃ and the reaction time is 4-10 hours, standing and layering are carried out after the reaction is finished, a lower DES phase and an upper product phase containing the organic solvent are obtained, the separated and recovered lower DES p