Fine regulation of Ru species improved the polyethylene hydrogenolysis performance over Ru/Al₂O₃ catalyst

Thermocatalytic technologies are the most promising approach for converting plastic waste into valuable chemicals. The Ru-based catalysts are the most active catalysts reported, which are highly efficient for C-C bond breaking during thermocatalytic plastic degradation. Still, significant challenges remain in controlling the selectivity of the valuable liquid product. A trade-off relationship between the activity and selectivity is commonly found during thermocatalytic plastic degradation. Herein, we demonstrated that a Ru/γ-Al₂O₃-Ar catalyst, prepared from commercial γ-Al₂O₃ pre-calcined under an air atmosphere, achieved 100% conversion over low-density polyethylene (LDPE) hydrogenolysis and an 85.9% selectivity for fuel-range and wax hydrocarbons at 250 °C for 4 h. In contrast, Ru loaded on the synthesized γ-Al₂O₃ showed only a 17.9% selectivity toward fuel range and wax hydrocarbons, with methane being the predominant product. Comprehensive characterizations revealed a strong metal-support interaction (MSI) at the interface between Ru and γ-Al₂O₃-Ar, leading to the abundance of Ruⁿ⁺ species at the Ru-Al₂O₃ interface. Combined experimental and DFT computational studies reveal that the incorporation of Ruⁿ⁺ effectively suppresses excessive dehydrogenation into methane intermediates. Simultaneously, it promotes the hydrogenation of hydrocarbon intermediates through a synergistic hydrogen spillover effect, driven by high H* coverage, which ultimately boosts catalytic efficiency.