Upgrading automotive plastic waste into aromatic hydrocarbon-rich oils with low halogen content via hydropyrolysis over bimetallic catalysts

Plastics from end-of-life vehicles (ELVs) are complex and underutilised waste, rich in engineering polymers and halogenated additives that hinder conventional recycling and may release persistent pollutants. This work investigates the hydropyrolysis of real ELV-derived plastics under both atmospheric and moderate (6 bar) pressures, integrating thermal decomposition with in-situ catalytic upgrading. Experiments were performed in a dual-zone fixed-bed reactor at 550 ◦C (thermal) and 450 ◦C (catalytic) using nanocrystalline ZSM-5-based catalysts containing Fe, Pd, or bimetallic Pd-Fe species. The heterogeneous feedstock, containing a complex mixture of polymers and chlorinated components (~0.7 wt% Cl), produces oils as main fraction (53.9–60.2 wt%) under thermal conditions. Pressure promotes chlorine retention in the char (up to 91 wt%) lowering its transfer to the oil. Likewise, catalysts drastically reduce chlorine levels in the oil (<41 ppm), with the Pd-Fe system achieving the lowest concentration (25.5 ppm) under pressurised hydropyrolysis. This superior performance arises from a synergistic interaction between Pd and Fe: Pd enhances Fe reducibility, boosting hydrodehalogenation activity, while Fe contributes to inorganic chlorine trapping, together minimising halogen content and preserving oil quality. GC-MS analyses reveal that oils are dominated by monoaromatic hydrocarbons, with variations in selectivity and oxygenate content depending on catalyst composition and reaction conditions. The results demonstrate that combining hydropyrolysis with tailored bifunctional catalysts offers a robust, integrated pathway for converting halogenated automotive plastics into feedstocks compatible in refineries and chemical value chains. Therefore, by a single processing step this underused complex waste is turned into a valuable resource tackling key environmental challenges.