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.