Rapid alcoholysis of PET enhanced by its swelling under high temperature

The development of catalysts with high thermal stability, high catalytic activity and high cycling performance has been an important challenge in PET alcoholysis research. PET degradation is a surface interface controlled process, but PET as a dense solid with lower specific surface area severely reduces its degradation rate. Here, the high specific surface area (0.4–3.3 m2/g) and the large number of pores (0–17.5 nm) formed by the swelling of PET at high temperature were used to break the interfacial confinement between the reactants; then the rapid and complete degradation of PET was achieved under the multi-hydrogen bonding microenvironment formed by the multi-active site polyoxometalate (POM) catalysts K10[M4(H2O)2(PW9O34)2]-H2O (M = Zn, Mn, Cu, Ni, Co) and EG. Finally, accompanied by the attack of the transition metal active site on CO of PET, 1.0 g of PET could be completely degraded in 5 min under the optimal reaction conditions (2.0 wt% of catalyst to PET, 240 °C) and the bis(hydroxyethyl) terephthalate (BHET) yield of 92.8% was achieved within 8 min. Moreover, the catalyst could be recycled more than 30 times, which is very meaningful. In the same time, the mechanism of PET alcoholysis was investigated and proposed a mechanism of PET alcoholysis.