Catalytic depolymerization of poly(ethylene terephthalate) plastic into value-added monomers using metal-modified mesoporous silica

The glycolysis of poly(ethylene terephthalate) (PET), a polymer extensively used in food packaging, into bis(2-hydroxyethyl) terephthalate (BHET) monomers was investigated using mesoporous silica supported by metal oxide as catalysts. Among these, a catalyst composed of ZnO supported on KIT-6 (5%ZnO/KIT-6) showed an effective performance in PET glycolysis, achieving a BHET yield of 92.1% with complete conversion of PET. Additionally, the catalyst demonstrated exceptional reusability and high efficiency in handling post-consumer PET plastics, with BHET yields reaching up to 89%. Characterization studies revealed that the highly dispersed ZnO nanoparticles trapped in KIT-6 channels formed strong interactions with surface Si-OH groups, leading to an enhanced acid strength and an increased number of acid sites, which significantly improved PET depolymerization. This study presents an innovative solution for the recycling of PET plastic, contributing to industrial development and reducing the impact of plastic waste.