Heterogeneous continuous kinetics modeling of PET depolymerization in supercritical methanol

The kinetics of PET depolymerization in supercritical methanol was investigated. A continuous kinetics model was developed to analyze PET decomposition behavior. This model includes molecular weight distribution (MWD) changes in the polymer by random and specific scissions and secondary reactions of monomer components for complex macromolecular reactions. The changes of MWD and monomers as a function of time were simulated by continuous kinetics. Reactions in two phases, polymer melt phase and supercritical phase, were considered. By comparing simulated and experimental results, values of the rate constants were determined. These results indicated that random scission proceeds predominantly in the heterogeneous phase during the initial stage of PET depolymerization in supercritical methanol and specific scission proceeds predominantly in the homogeneous phase during the final stage. It was also shown that mass transfer influences the depolymerization of PET.