Double metal cyanide complex as a heterogeneous catalyst for depolymerization of polyesters

Plastic wastes have caused a series of environmental issues, and it has become imperative to promote the recycling of them. As an effective means to solve environmental problems and resource utilization, the chemical depolymerization of polyester via transesterification reaction was practical. Therefore, finding industrially viable transesterification catalysts is an effective strategy for establishing a recycling route for polyester plastics. Herein, we report double metal cyanide complex (DMC) directly catalyze polyester depolymerization to recover the corresponding monomers or chemicals. Poly(ethylene terephthalate) (PET) was used as representative polyester to investigate the influences of experimental conditions including the loading of the catalyst and the molar ratio of ethylene glycol (EG) to PET on the depolymerization of polyester and the selectivity of monomeric products. The kinetics of the glycolysis has been measured. PET could be completely depolymerized at 190 °C by 2 h with the molar ratio of EG/PET of 15: 1 and the catalyst loading of 1 wt%. DMC also showed high catalytic activity on the depolymerizations of other commercial plastics of ester main-chains. DMC, a solid catalyst enjoyed inexpensive, robust, and water tolerant features in industrial process, showed prominent activity and selectivity in polyester depolymerizations and suggested scale commercial application scenario.