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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.
Yin et al. (Fri,) studied this question.