Exfoliated manganese oxide nanosheets as highly active catalysts for glycolysis of polyethylene terephthalate

Abstract

Glycolysis of poly(ethylene terephthalate) (PET) is one of the main methods by which PET is recycled, which is in the need of an inexpensive and efficient catalyst. We report a glycolysis reaction of PET into bis(hydroxyethyl) terephthalate (BHET) catalyzed by ultrathin exfoliated MnO2 nanosheets (e-MON). The exfoliation of MnO2 was achieved using a shear flow system with a mixing behavior that facilitates the intercalation of potassium ions into the interlayer voids of MnO2, delaminating MnO2 into the mono- and few-layer e-MON. Glycolysis was optimized by varying the reaction temperature, time, and loading of e-MON. The e-MON catalyst provided a BHET yield of 100 % for a reaction lasting 30 min at 200 °C, which was much higher than the 77.6 % yield achieved with bare bulk MnO2. The high yield persisted over five cycles, demonstrating the reusability of the e-MON catalyst.