Fe-Ni Bimetallic Modified HZSM-5 for Efficient Preparation of Monocyclic Aromatic Hydrocarbons via Co-Pyrolysis of PET and LDPE

Plastic waste has become a serious global issue. Thermal treatment of waste PET faces critical drawbacks including severe reactor clogging and low-value oxygen-rich bio-oil, restricting large-scale chemical recycling. Co-pyrolysis with hydrogen-rich low-density polyethylene (LDPE) over modified zeolite provides a viable route to overcome these barriers. In this study, reaction parameters including temperature, plastic/catalyst ratio and PET/LDPE ratio were optimized, and Fe-Ni bimetallic modified HZSM-5 was fabricated via impregnation to boost monocyclic aromatic hydrocarbons (MAHs) production. LDPE served as a hydrogen donor to facilitate PET deoxygenation via synergistic effects. At 550 °C with a plastic/catalyst ratio of 1:4 and PET/LDPE ratio of 2:3, the liquid yield hit 80.2%, and all detectable organic compounds in the liquid phase identified by GC–MS were aromatic hydrocarbons. Among all prepared mono- and bimetallic zeolites, 3Fe7Ni/HZ delivered optimal MAHs selectivity at 80.5%. This 20% promotion over unmodified HZSM-5 stems from balanced metal dispersion and tuned acid sites unique to Fe–Ni co-loading. This work offers a feasible strategy for converting waste plastics into high-value aromatics and further trials with varied metal contents will be needed to extend industrial applicability.