Hot Pickering emulsion interfacial catalysis accelerates polyethylene terephthalate (PET) glycolysis

Abstract

Pickering emulsion interfacial catalysis (PEIC) could be a feasible strategy to improve the efficiency of catalytic reactions, but it is difficult to achieve in hot conditions because conventional Pickering emulsions are unstable at high temperatures. Herein, a stable hot Pickering emulsion interfacial catalysis (HPEIC) system for efficient depolymerization of polyethylene terephthalate (PET) was constructed by using modified asymmetric nanonets (M-ANNs), a super-performance emulsifier that we have reported. In the HPEIC system, biphenyl that can disperse PET is chosen to be the dispersed phase, and ethylene glycol that can dissolve glycolysis catalyst Zn(OAc)₂ is designed as the continuous phase. The HPEIC system achieved 100% depolymerization of PET and yielded more than 90% of PET monomer within 5 minutes at 170 °C, due to the suitably designed respective dissolution of PET and Zn(OAc)₂ in the two different solvents, the large emulsion interface area, and the enrichment of catalyst at the emulsion droplets interface. The degradation time is extremely shortened and the reaction temperature is at least 20 °C lower than that of the traditional homogeneous catalytic systems. The HPEIC system maintained a high PET depolymerization rate after six times of recycles.