ZnO nanodispersion as pseudohomogeneous catalyst for alcoholysis of polyethylene terephthalate.

• The highly stable dispersions of ultrasmall ZnO nanocrystals were prepared. • They were used as pseudohomogeneous catalyst for chemical depolymerization of PET. • ZnO nanodispersions displayed an excellent catalytic activity at 170 °C. • The methanolysis had shorter reaction time and higher activity than the glycolysis. Chemical depolymerization and recycling of polyethylene terephthalate (PET) is a sustainable way to preserve the resources and protect the environment. In this work, methanol and ethylene glycol dispersions of ultrasmall ZnO nanoparticles are firstly adopted as pseudohomogeneous catalysts for alcoholysis of PET. The as-prepared ZnO nanoparticles have a uniform size of 4 nm and can be stable in dispersions for 6 months. In the methanolysis process of PET, the effects of various parameters on the conversion of PET and the yield of dimethyl terephthalate (DMT) were investigated. The results show that higher temperature (170 °C) was beneficial to the conversion of PET and the yield of DMT, which can reach about 97% and 95% after 15 min, respectively. The excellent activity of 553 g PET h−1 (g ZnO)−1 was achieved. Furthermore, the methanolysis of PET have shorter reaction time (1/4) and higher activity (4.7 times) than the glycolysis of PET. [ABSTRACT FROM AUTHOR]