Novel Process Design of Synthesizing Propylene Carbonate for Dimethyl Carbonate Production by Indirect Alcoholysis of Urea

Dimethyl carbonate (DMC) is a green compound with a broad variety of application. Recently, CO2-based routes to produce DMC have attracted much attention because of the environment benefits of CO2 utilization. In the study, we investigate the process design of synthesizing propylene carbonate (PC) for the DMC production using CO2 as a raw material by indirect alcoholysis of urea. The indirect alcoholysis route of urea shows many advantages because of cheap raw materials, mild and safe operation conditions, and environmentally friendly chemicals. Some different processes for PC synthesis by this route are proposed, designed, and optimized in this work. These processes can be classified in terms of two operation types: near-neat operation and excess reactant operation. Reactive distillation (RD) and heat integration technologies are used to intensify PC synthesis processes. Two processes are designed under the near-neat operation. Three RD plus conventional distillation (CD) processes with heat integration are designed under the excess reactant operation. Simulation results reveal that the novel intensified process containing a RD column and a CD column with internal vapor compression provides the most economical design by fully utilizing the special azeotrope characteristic of the propylene carbonate and propylene glycol pair.