A new mechanism for the kinetics of simultaneous depolymerization reaction inside and outside poly (ethylene terephthalate) particles

The depolymerization and recycling of PET is important for waste reduction, resource efficiency and production cost reduction. However, among the industrialized methods for recycling waste PET, the main challenge applicable to the PET glycolysis strategy is the low efficiency and low purity in recovering polyester, which is mainly due to the imperfections in the reaction kinetics model. In this study, we developed a kinetic model for PET glycolysis at different reaction temperatures by investigating the glycolysis process of PET chips at different reaction temperatures to discover new PET glycol depolymerization mechanisms. It was found that the zinc acetate-catalyzed PET glycolysis followed a first-order reversible kinetic model at higher temperature (206-210 degrees C). However, at lower temperatures (180 degrees C-205 degrees C), the experimental curve of the kinetic model is similar to the theoretical curve of the nucleation-controlled model, and in this temperature range, EG depolymerized PET in a manner that internal and external depolymerization proceeded simultaneously. This finding is expected to guide the establishment of a more efficient PET depolymerization process, which is an important guide for recycling waste PET.