EXPERIMENTAL AND MODELING STUDIES ON MELT TRANSESTERIFICATION OF DIMETHYL TEREPHTHALATE WITH ETHYLENE-GLYCOL IN A CONTINUOUS STIRRED TANK REACTOR

The steady-state and transient behaviors of a continuous melt transest erification process which is the first stage in the synthesis of therm oplastic poly(ethylene terephthalate) have been studied with dimethyl terephthalate and ethylene glycol as reactants and zinc acetate as a c atalyst. A molecular species model was developed for three major react ions in the transesterification stage. The effects of reactor residenc e time, feed ethylene glycol/dimethyl terephthalate mole ratio, and zi nc acetate concentration on the reactor performance have been investig ated through laboratory experiments and model simulations. The catalys t utilization factors were used to account for the relative availabili ty of catalytically active Zn2+ for ester interchange, transesterifica tion, and polycondensation reactions. The agreement between the model predictions and the experimental data was quite satisfactory. It was a lso observed that the transient reactor response time depends on the t ype of changes in the reactor operating conditions.