The process of dimethyl carbonate to diphenyl carbonate: Thermodynamics, reaction kinetics and conceptional process design

Diphenyl carbonate (DPC) is a precursor in the production of Polycarbonate (PC), a widely employed engineering plastic. To overcome the drawbacks of the traditional PC process - e.g. phosgene as a reactant and methylene chloride as solvent- a new process route starting from Dimethyl carbonate (DMC) via Methyl Phenyl carbonate (MPC) to DPC is investigated in this thesis. First the general applicability of activities in reaction rate equations is examined, both theoretically and experimentally, for the system CO2-OH—salts. The results show that the activity based reaction rate yields fundamentally better results compared to the traditional concentration based approach and moreover establishes a fundamental link to the activity based description of chemical equilibria. For the derivation of activity based reaction kinetics as well as chemical equilibria, activity coefficients are required. Hence, available VLE data of relevant carbonate systems has been taken from literature to fit corresponding UNIFAC parameters which have subsequently been used for the description of the relevant chemical equilibria and reaction kinetics. The chemical equilibria encountered in the process from DMC to DPC have been experimentally determined thereby studying the influence of the molar reactant ratio DMC/phenol (0.25-3.0) and temperature (160-200C). The activity based and concentration based chemical equilibria have been compared to each other and the temperature dependence of the chemical equilibria has been described. A comprehensive study has been performed to determine the kinetics of the three reactions involved in the carbonate system. The influence of the reactant ratio DMC/phenol (0.25-3.0), temperature (160-200C) and the catalyst amount has been investigated. The concept of a closed ideally stirred, isothermal batch reactor incorporating an activity based reaction rate model, has been used to fit kinetic parameters to the experimental data. For exploring the industrial production process of DPC from DMC using reactive distillation, a tray column model originating from the software package ChemSep was used. The influence of various parameters - feed location(s), number of stages, temperature and pressure - was studied and the results are evaluated. First a process comprising of one reactive distillation column and then a process employing two reactive distillation columns has been investigated.