Enhanced hydroconversion of polyethylene via dual-functional catalysis: Exploiting ZSM-22 pore-mouth catalysis and Ru electronic effect

Abstract

The subject of extensive research, the low-temperature hydrocracking of polyethylene reveals the one-step synthesis of iso-alkanes via metal–acid bifunctional catalysis as an emerging strategy. Zeolites, with their superior compatibility with existing petrochemical infrastructure, serve as the acidic supports of choice. In this research, Ru nanoparticles were loaded onto ZSM-22, a zeolite known for its effective pore-mouth catalysis. Mechanical ball milling enhanced the pore-mouth area and the proximity of metal–acid sites, significantly boosting the hydrocracking reaction. The electronic properties of Ru were modified by selecting various Ru precursors and adjusting loading amounts. In-situ infrared studies showed the detachment of olefin intermediates from Ru sites as a critical factor in controlling hydrocracking and the terminal hydrogenolysis reactions. By combining catalyst characterization with reaction barrier calculations from density functional theory (DFT), it was found that oxidized Ru species aid in the release of olefin intermediates, facilitating Brønsted acid-driven β-scission and isomerization reactions. The study achieved a liquid-phase yield exceeding 82 wt% and an iso/n ratio surpassing 60% under low-energy consumption conditions using commercially available catalysts.