Oxidative Fast Pyrolysis of Polyethylene Waste over Zeolite Catalyst: Product Distribution and Coking Regulation

High Resolution Image Download MS PowerPoint Slide Oxidative catalytic pyrolysis emerges as a viable strategy for upcycling plastic waste into value-added chemicals, where oxygen concentration governs product distribution. In this work, the oxidative fast pyrolysis of low-density polyethylene (LDPE) over ZSM-5 zeolites was investigated, focusing on the distinct roles of co-fed oxygen in driving reaction pathways. Results show that introducing oxygen initiates rapid radical scission of the polymer backbone, increasing gas yields from 1.4 to 16.3% while significantly reducing wax. The less pronounced influence of catalyst acidity under aerobic conditions suggests that oxygen-induced oxidative cracking dominates the initial macromolecular decomposition over traditional acid-catalyzed pathways. GC-MS (Gas chromatography-mass spectrometry) analysis reveals that 10% oxygen optimizes light oil and mono-aromatics by balancing cracking capability and over-oxidation. Furthermore, doubling the vapor-phase residence time over ZSM-5 elevates the gas yield from 41.9% to 59.5%, favoring C 3 −C 4 hydrocarbons and polycyclic aromatic hydrocarbons. Crucially, analysis of spent catalysts elucidates that oxygen mitigates deactivation by scavenging coke precursors, achieving in situ oxidative regeneration that reduces carbon deposition on ZSM-5(38) from 9.5% to 6.2%. This study provides a quantitative elemental framework and key experimental insights for developing highly efficient oxidative catalytic pyrolysis processes for plastic recycling.