Modeling of semibatch and continuous melt polycondensation reactors for the synthesis of poly(ethylene terephthalate)

The semibatch and continuous reactors for melt transesterification and prepolymerization in the PET synthesis process are studied. A molecular species model is developed and validated experimentally for the zinc acetate catalyzed transesterification of DMT/EG and DMT/BHET reaction systems. Both on-line condensate measurement and off-line HPLC analysis data have been used to validate the reactor model. The proposal of the catalyst dissociation and Zn;For the modeling of the prepolymerization process, a detailed molecular species model is developed to describe the reaction progress and side-products formation in a semibatch prepolymerization reactor. It has been observed that incomplete conversion of methylester groups in the transesterification stage may be beneficial in obtaining high molecular weight in the prepolymerization stage even when only moderate vacuum is applied. A functional group model is also developed to investigate the steady-state and transient behavior of a continuous stirred tank prepolymerization reactor. The effects of various reactor operating conditions on the polymer molecular weight, carboxyl acid end group concentration, and DEG content have been analyzed through model simulations.