Hydrogen-rich gas by catalytic pyrolysis of polyethylene via mono and bimetallic Fe/Ni catalysts

Abstract

Catalytic thermal conversion represents a promising strategy for transforming waste plastics into high value products. This research demonstrates a two-stage pyrolysis catalysis integrated system for polyethylene valorization and hydrogen-enriched syngas production. Mono-/bimetallic Fe/Ni-ZSM catalysts were synthesized and systematically characterized to evaluate their structural and catalytic properties. Key operational parameters including metal loading, catalyst-to-polyethylene ratio, and steam flow rate were optimized to maximize gas yield and hydrogen selectivity. Experimental results revealed that bimetallic catalysts, particularly those with higher Ni content, exhibited superior catalytic performance compared to monometallic analogues due to the synergistic Fe–Ni alloy formation and enhanced metal-support interactions. Under optimal conditions (6 mL/h steam flow, 1:1 polyethylene-to-catalyst ratio), the 5Fe10Ni-ZSM catalyst achieved a hydrogen yield of 133.99 mmol/g_PE with 70.40 % volumetric concentration in syngas. It was also found that irregular carbon nanostructures were formed on the surface of the spent catalyst. This study offers a novel method for repurposing waste polyethylene.