Synthesis of dimethyl carbonate from methyl carbamate and methanol with modified 4A zeolite as catalyst

• 1、Faculty of Chemical Engineering, Kunming University of Science and Technology
• 2、State Key Laboratory of Coal Conversion, Institute of Coal Chemistry

Abstract： The synthesis method of dimethyl carbonate from urea and methanol has more industrialization prospect than many other synthesis methods. In this method, the rate-control step is the reaction of intermediate methyl carbamate with methanol. This work firstly applied ions exchange method to preparing a series of 4A zeolite catalysts modified by Zn、Cu、Pb、Ni. The effect of reaction conditions on the ions exchange degree was investigated. The results showed that the initial ion concentration has greater impact on the degree of exchange, and the reaction time and temperature have less impact on the degree of exchange. According to this theoretical basis, a series of modified zeolite with ions exchange degree about 100% were prepared and used to catalyze the rate-control step reaction of dimethyl carbonate synthesis. Results showed that the activity of zinc and lead modified 4A zeolite was poor, but the homogenous catalyst was heterogenized. This work further examined the activity of impregnated zinc-modified zeolite in dimethyl carbonate synthesis. It is found that the activity of catalysis was obvious, but zinc ion would fall off in the catalytic reaction process, producing diammine chloride zinc precipitation. It indicated that the homogeneous catalyst can not be heterogenized with impregnation.

Keywords： Dimethyl carbonate；methyl carbamate；ion exchange method；impregnation method； heterogeneous catalyst