Effective Methane Suppression in Upcycling of Polyethylene into Fuels via Alloying Platinum with Ruthenium Supported on ZSM-5 Zeolite

Ruthenium (Ru)-based catalysts are active in catalyzing polyethylene (PE) upcycling, but their tendency for methanation devalues the process. Although previous works confirmed that the regulation of the Ru structure can inhibit methane yields, the mechanism is still unclear, and the catalytic performance remains higher upside potential. Herein, we synthesized M-Ru/H-ZSM-5 (M = Pt, Pd, Rh) catalysts for PE upcycling. Pt-Ru/H-ZSM-5 had better conversion (84.36%) and liquid fuel selectivity (78.38%) and extremely low methane selectivity (8.43%), which can be ascribed to its more electron-deficient Ru^δ+ species and the synergistic catalytic effect induced by Pt doping. Through density functional theory calculations, the nature of methane inhibition was uncovered and the reaction pathway was proposed. Furthermore, the Pt-Ru/H-ZSM-5 catalyst demonstrated its stability and reusability, as well as its efficacy for upcycling various PEs. This work reveals the mechanism of Ru-based catalysts in PE upcycling reactions, promoting plastic recycling development.