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[Chemical Knowledge]：Production method and process of dimethyl carbonate

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Dimethyl carbonate (DMC) is an important chemical raw material, widely used in synthetic fibers, plastics, pesticides, pharmaceuticals, fuels and other fields. This article will introduce the manufacturing method of dimethyl carbonate.

1. Transesterification

Transesterification is the main method for the production of dimethyl carbonate at home and abroad, the principle of which is the transesterification of methanol and dimethyl carbonate to produce diphenyl carbonate and methanol, and then the dimethyl carbonate is separated by distillation. Transesterification method can be divided into liquid phase method and gas phase method.

1. Liquid Phase Method
The
liquid phase method is a transesterification reaction of methanol and dimethyl carbonate in the presence of a catalyst. Commonly used catalysts include alkaline absorbents, acidic catalysts and metal complex catalysts. The reaction temperature is generally between 100 and 200 ° C. and the pressure between 0.5 and 2.0MPa. After the reaction, dimethyl carbonate and methanol are separated by distillation, and the purity of dimethyl carbonate can reach more than 99%.

2. Gas Phase Process

gas phase process is a transesterification reaction of gaseous methanol and dimethyl carbonate in the presence of a catalyst. The catalysts commonly used in gas phase method include acidic catalysts and alkaline absorbents. The reaction temperature is generally 200-400 ° C. and the pressure is between 0.1-1.0MPa. After the reaction, dimethyl carbonate and methanol are separated by condensation, and the purity of dimethyl carbonate can reach more than 99%.

2. Methanol oxidative carbonylation

Methanol oxidative carbonylation is a new method for the production of dimethyl carbonate, the principle of which is to react methanol, carbon monoxide and oxygen to produce dimethyl carbonate and water. This method has the advantages of easy access to raw materials, mild reaction conditions and high yield, and is one of the hotspots in the production of dimethyl carbonate. The catalysts

the oxidative carbonylation of methanol mainly include noble metal catalysts and non-noble metal catalysts. The reaction temperature is generally between 100 and 200°C and the pressure is between 1.0 and 5.0MPa. After the reaction, dimethyl carbonate and water are separated by distillation, and the purity of dimethyl carbonate can reach more than 99%.

3. Urea Methanolysis

Urea Methanolysis is a traditional method of producing dimethyl carbonate, the principle of which is to react urea and methanol in the presence of a catalyst to produce dimethyl carbonate and ammonia. This method has the advantages of simple process and easy access to raw materials, but the yield is low and the production cost is high. There are two main types of catalysts

urea methanol hydrolysis: acidic catalysts and alkaline catalysts. The reaction temperature is generally between 150 and 250 ° C. and the pressure is between 1.0 and 5.0MPa. At the end of the reaction, dimethyl carbonate and ammonia gas are separated by distillation, and the purity of dimethyl carbonate is generally between 95% and 98%.

In short, there are many production methods of dimethyl carbonate, and different methods have different advantages and disadvantages and scope of application. In actual production, the appropriate production method should be selected according to the specific situation to improve the yield, reduce the cost and ensure the quality of the product.

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