Canadian Journal of Chemical Engineering, Vol.99, No.2, 467-478, 2021
Comparative thermodynamic analysis of CO2 based dimethyl carbonate synthesis routes
The chemical equilibrium analysis of various possible reactions involved in the five CO2-based routes for the synthesis of dimethyl carbonate (DMC), a green chemical reagent, was performed in the present study. The variation of the molar Gibbs free energy change with temperature for the major reactions of DMC synthesis in all five routes was studied in the specified temperature range of 298.15 K-453.15 K and at both 1 bar and 28 bar pressures (1 bar = 10(5) Pa) to observe the thermodynamic favourability of all routes. To observe the temperature effect, the molar heat capacities for various compounds were estimated in terms of temperature. A second-order group additivity method called the Ruzicka-Domalski method was used to estimate these heat capacity values. The major reactions of DMC synthesis in urea methanolysis, EC transesterification, PC transesterification, and direct CO2 synthesis routes were compared by investigating the effect of temperature (in the range of 298.15 K-453.15 K) on the chemical equilibrium constants and the equilibrium conversions of methanol at a constant pressure of 28 bar. The one-pot propylene oxide (PO) synthesis route was observed to be better among all the five CO2 based routes when it was compared with respect to values of the chemical equilibrium constant and equilibrium conversion of methanol at standard conditions. The reliability of the EC transesterification route was found better among all the routes at initial conditions (T = 298.15 K; P = 28 bar). While the urea methanolysis route was found as least favourable at initial conditions.