Modeling of Chemical Equilibrium and Gas Phase Behavior for the Direct Synthesis of Dimethyl Carbonate from CO2 and Methanol

The chemical and gas phase equilibrium of the direct synthesis of dimethyl carbonate (DMC) from methanol (MeCH) and CO2 was modeled under mild conditions of temperature and pressure. Deviations from ideality for the quaternary mixtive (CO2 + MeOH + DMC + H2O) were estimated using the gamma - phi thermodynamic approach. Binary interaction parameters (k(ij)) and UNIQUAC parameters (A(ij)) were extracted from VLE data reported in the literature. The results show that MeOH conversion is enhanced by increasing the pressure and reducing the temperature; however, pressure and temperature are bounded by the dew point. Data of P, T, and vapor compositions obtained from modeling chemical equilibrium were used to predict dew points of the reacting mixture and to establish the region of T and P where the gas-phase reaction could be carried out. To avoid condensation, an increase in pressure must be accompanied by a temperature increase. Moreover, the larger the methanol concentration in the feed mixture is, the higher is the required temperature.