Simplified, fast, and efficient microwave assisted chemical recycling of poly (ethylene terephthalate) waste

The widespread adoption of chemical recycling of poly (ethylene terephthalate) (PET) is hampered by long reaction times, high energy consumption and the use of metal catalysts that are either toxic or cost prohibitive for industrial use. Herein, we report a simple PET glycolytic process that combines an environmentally friendly and cheap heterogenous catalyst, calcium oxide (CaO) with microwave irradiation to obtain the monomer bis(2-hydroxyethyl) terephthalate (BHET), which can be easily separated by crystallisation. After the process optimisation, depolymerisation of PET waste was achieved in 3.5 min under atmospheric pressure, to obtain highly crystalline BHET with a yield of 75%. To our knowledge, this is the fastest heterogeneous glycolytic process reported in the literature to-date, using a cheap and eco- friendly catalyst. Moreover, by using a heterogenous catalyst and avoiding the need for product precipitation by water addition, CaO and ethylene glycol materials were separated and reused, thus validating this protocol as a potential green and scalable route for PET recycling.