Electronegativity-driven d-band center shifts in Ru–Ni alloys for low methane hydrogenolysis of polyolefin plastics

Abstract

Ruthenium (Ru) catalysts are highly efficient in the hydrogenolysis of polyolefin waste, converting the waste into valuable alkanes. However, excessive C–C bond cleavage of strongly adsorbed olefin intermediates often leads to low-value byproducts, primarily methane (CH₄). In this study, we developed a Ru–Ni bimetallic catalyst supported on silica (Ru_xNi_y/SiO₂) that directly modulates olefin intermediate adsorption to suppress CH₄ formation during polyolefin hydrogenolysis. By alloying low-electronegativity Ni with high-electronegativity Ru, we shift the Ru d-band center through electron transfer from Ni, weakening the adsorption of olefin intermediates. This modification facilitates hydrogenation and desorption pathways while suppressing excessive C–C bond cleavage. The resulting catalyst achieved complete polyethylene (PE) conversion at 250 °C, with 96.9 wt% liquid product yield and only 2 wt% CH₄ production. Gasoline- and diesel-range alkanes (C5–C22) accounted for 77.1 wt% of the products. Additionally, the catalyst demonstrated excellent performance with real-world single-use polyolefin products. This work provides a new approach for controlling intermediate adsorption in polyolefin recycling, offering a promising path to enhance the efficiency and selectivity of plastic recycling technologies.