Upcyclingof Polyethylene Terephthalate to High-ValueAromatics 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 C_alkyl–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 (<i>in situ</i> vs <i>ex situ</i>), 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.