Upcycling of Polyethylene Terephthalate to High-Value Aromatics via Catalytic Pyrolysis over Zeolites

Catalytic upcycling, a process for the valorization of plastic waste toward value-added products, has garnered attention as a promising approach to plastic waste management. This study investigated the aromatic product distribution from the thermal and catalytic fast pyrolysis of PET using Py-GC-MS/FID. Thermal pyrolysis (550–800 °C) of PET revealed that acetophenone increases sharply with rising temperatures, becoming the dominant aromatic product at 800 °C. Catalytic pyrolysis of PET was conducted with three zeolites (HZSM-5, HBeta, and HY). HBeta yielded the highest benzene, while HZSM-5 exhibited the highest total yields of benzene, toluene, ethylbenzene, xylene, styrene, and naphthalene. HY significantly promoted the production of acetophenone, a new finding that was further investigated by using vinyl benzoate and ethylene dibenzoate as model compounds. A new formation route of acetophenone was proposed, involving the homolysis of Calkyl–O bond in PET, rearrangement, and decarbonylation. Further, the effects of various reaction conditions, including catalyst/feedstock ratios, pyrolysis temperatures, SiO2/Al2O3 ratios, and the mode of operation (in situ vs ex situ), on the distribution and selectivity of aromatic products were systematically explored. The new findings in this work contribute to the application of catalytic pyrolysis technology in the upcycling of oxygen-containing organic solid waste.