Reaction from Dimethyl Carbonate to Diphenyl Carbonate. 1. Experimental Determination of the Chemical Equilibria

Abstract

New experimental equilibrium data of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of MPC to diphenyl carbonate (DPC) are presented and interpreted in terms of the reaction equilibrium coefficients. Experiments have been carried out in the temperature range between 160 and 200 °C and for initial reactant ratios of DMC/phenol from 0.25 to 3. By employing activities instead of “only” mole fractions in the calculation of the reaction equilibrium coefficients, the influence on the reactant ratio DMC/phenol on the derived equilibrium values for the reaction of DMC to MPC could be reduced, especially for temperatures of 160 °C. The activity based equilibrium coefficient for the transesterification reaction from MPC with phenol to DPC and methanol is constant within experimental uncertainty and, therefore, largely independent of the initial reactant ratio DMC/phenol at temperatures of 160 and 180 °C. The temperature dependence of the equilibrium coefficients Ka,1 and Ka,2 has been fitted by applying the well-known Van’t Hoff equation, resulting in the expressions ln Ka,1 = −2702/T[K] + 0.175 and ln Ka,2 = −2331/T[K] − 2.59. It has been demonstrated that these equations have fair, in the case of ln Ka,1, and excellent, in the case of ln Ka,2, predictive capabilities, even for experimental conditions that deviate significantly from those used in this study. Hence, it is expected that the derived temperature dependent correlations for Ka,1 and Ka,2 based on activities can be used in reactive distillation models to assess different process configurations in the manufacture of DPC starting from DMC and phenol.