Yanshan Yin, Shuo Wang, LIANG ZHAO, Wei Zhang, Wenran Gao, Bo Gu, Rui Liu, Shitong Liu, Ruiqi Wang, Hong Tian, Nai Shi, Zhiliang Wu
Global plastic production continues to grow rapidly, and the short service life of most plastics has intensified waste accumulation and environmental pressures. Most waste plastics contain over 90 wt% volatile matter, with extremely low ash and fixed carbon contents, making them ideal feedstocks for pyrolysis. Pyrolysis has emerged as a promising thermochemical pathway for transforming heterogeneous plastic waste into plastic pyrolysis oils (PPOs). Certain PPOs exhibit high heating values of 36.53–49.70 MJ/kg, highlighting their potential as liquid fuels and chemical feedstocks. This review provides a comprehensive and mechanistic assessment of PPOs production, emphasizing how the structural features of plastics dictate chain scission pathways, radical formation, aromatization, and heteroatom-related reactions. Key process parameters, including temperature control, heating rate, residence time, reactor configuration, and feedstock pre-treatment, are critically evaluated for their roles in determining PPOs yield and physicochemical properties. Catalytic pyrolysis using acidic zeolites and basic oxides can increase PPOs yield to over 80 wt%, promote gasoline- and diesel-range hydrocarbons, reduce moisture and oxygenated compounds, and remove impurities. Co-pyrolysis with biomass or other organic wastes is further shown to produce strong hydrogen-donation and deoxygenation synergies that improve oil quality. Emerging upgrading pathways, such as distillation, catalytic cracking, hydrotreating, and hydrocracking are discussed as complementary routes for specification-compliant fuels. Finally, techno-economic analysis and life-cycle assessment are integrated to assess cost-effectiveness, energy efficiency, and environmental implications. By consolidating mechanistic knowledge, process optimization strategies, and sustainability considerations, this review provides a comprehensive framework for developing cleaner, more efficient, and circular plastic-to-oil systems.