Insights into the depolymerization of polyethylene terephthalate in methanol

摘要

With concern to sustainable development, it is necessary to establish a recycling process of polyethylene terephthalate (PET). Methanolysis of PET is promising for chemical recovery of PET and the products are mainly dimethyl terephthalate (DMT) and ethylene glycol (EG), but the conditions of state-of-art depolymerization are severe. Here, we synthesized ionic liquid [HO3S-(CH2)(3)-NEt3]Cl-[ZnCl2](0.67) with Bronsted-Lewis di-acid and used it to efficiently catalyze the methanolysis of PET (m(methanol):m(PET) about 4) at milder temperature of 195 degrees C with yield of DMT about 78.4%. Reaction kinetics was studied and the result indicated the depolymerization of PET was a first-order kinetic reaction with the apparent activation energy of DMT formation about 17.63 kJ mol(-1). Random sampling experiment was also conducted and the results showd that DMT was the product of deep depolymerization of PET and two methanol molecules were needed to form DMT and EG in the depolymerization process. This study provides an efficient method to the recycling use of PET and wais significant to waste recovery and green environment.