Kinetic study on the one-pot synthesis of dimethyl carbonate in supercritical CO2 conditions

The kinetics of one-pot synthesis of dimethyl carbonate (DMC) was investigated using ethylene epoxide (EO), methanol, and CO2 as raw materials and a mixture of KI and K2CO3 as a catalyst under supercritical CO2 conditions. The reaction pathway of the one-pot process is that EO first reacts with CO2 to form ethylene carbonate (EC) and then EC reacts with methanol to produce DMC and ethylene glycol (EG). EC formation is a relatively fast reaction, whereas the transesterification of EC with methanol to form DMC is a relatively slow reaction and the rate-control step of the one-pot synthesis. 2-Methoxyethanol (ME), which is the exclusive byproduct, is predominantly formed by the reaction of EC with methanol. An isothermal kinetics model and an isobaric kinetics model for the one-pot synthesis of DMC were developed. The relative standard deviations of the models from the experiment data were less than +/-15% and +/-10%, respectively. The effects of temperature and CO2 density on the reaction rates and selectivity were discussed.