(403j) Sustainable Upcycling of Low-Density Polyethylene into Light Olefins Via Iron-Modified ZSM-5 Catalysis

Global plastic production has surged from 2 million metric tons in 1950 to over 450 million metric tons in recent years, yet only 9% is recycled, with polyethylene (PE) constituting 30% of plastic waste. Catalytic upcycling offers a sustainable route to convert PE into high-value short-chain olefins like ethylene and propylene—key precursors for polymers and chemicals. However, effectively and selectively decomposing PE into light olefins remains a significant challenge due to the polymer's chemical inertness and the complexities involved in controlling product distributions during degradation. Here, we report a Fe-modified ZSM-5 catalyst for efficient polyethylene pyrolysis into short-chain olefins under mild conditions. Systematic investigation of Fe loading, temperature, and pressure revealed optimal performance at 400°C under ambient pressure, achieving complete low-density polyethylene (LDPE) conversion within 1 hour in an inert atmosphere. The process yielded ~65% short-chain α-olefins, with light alkanes and minor cyclic compounds as byproducts. Crucially, the ZSM-5 framework retained structural stability post Fe incorporation and across 10 reaction cycles, demonstrating robust recyclability. These findings position Fe-ZSM-5 as a high-performance catalyst for selective plastic upcycling, enabling energy-efficient valorization of polyethylene waste under industrially feasible conditions.