Dimethyl carbonate (DMC) is an important raw material for the production of chemicals, which is widely used in synthetic fibers, plastics, pesticides, pharmaceuticals, fuels and other fields. This article will introduce the manufacturing method of dimethyl carbonate.
I. Ester exchange method
Ester exchange method is the main method to produce dimethyl carbonate at home and abroad at present, and its principle is that methanol and dimethyl carbonate are subjected to ester exchange reaction to generate diphenyl carbonate and methanol, and then distill and separate out dimethyl carbonate. The ester exchange method can be divided into two types: liquid-phase method and gas-phase method.
1. Liquid-phase method
Liquid-phase method is to carry out the ester exchange reaction between methanol and dimethyl carbonate in the presence of a catalyst. Commonly used catalysts include alkaline absorber, acid catalyst and metal complex catalyst. The reaction temperature is generally in the range of 100-200°C and the pressure is between 0.5-2.0 MPa. 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 method
The gas-phase method involves the transesterification of gaseous methanol and dimethyl carbonate in the presence of a catalyst. The catalysts commonly used in the gas phase method include acid catalysts and alkaline absorbents. The reaction temperature is generally in the range of 200-400°C and the pressure is in the range of 0.1-1.0 MPa. At the end of the reaction, dimethyl carbonate and methanol are separated by condensation, and the purity of dimethyl carbonate can also reach more than 99%.
II. Methanol Oxidation Carbonylation Method
Methanol Oxidation Carbonylation Method is a new method to produce dimethyl carbonate, which is based on the principle of reacting methanol, carbon monoxide and oxygen to produce dimethyl carbonate and water. This method has the advantages of easy availability of raw materials, mild reaction conditions, high yield, etc. It is one of the hot spots in the current research of dimethyl carbonate production. The catalysts for
methanol oxidative carbonylation method are mainly of two types: precious metal catalysts and non-precious metal catalysts. The reaction temperature is generally in the range of 100-200℃ and the pressure is between 1.0-5.0MPa. After the reaction, dimethyl carbonate and water are separated by distillation, and the purity of dimethyl carbonate can reach more than 99%.
Third, 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. The method has the advantages of simple process and easy availability of raw materials, but the yield is low and the production cost is high. The catalysts for
urea methanolysis are mainly of two types: acidic and basic catalysts. The reaction temperature is generally in the range of 150-250°C and the pressure is in the range of 1.0-5.0 MPa. At the end of the reaction, dimethyl carbonate and ammonia are separated by distillation, and the purity of dimethyl carbonate is generally between 95% and 98%.
In short, there are various methods for the production of dimethyl carbonate, and different methods have different advantages and disadvantages and applicable scope. In the actual production, the suitable production method should be selected according to the specific situation in order to improve the yield, reduce the cost and ensure the quality of the product.
