One-Step Production of Isoalkane-Rich Sustainable Aviation Fuel Fractions via Catalytic Pyrolysis of Low-Density Polyethylene over Y-Type Zeolite

This study introduces an innovative approach for producing isoalkane-enriched sustainable aviation fuel (SAF) fractions. It involves catalytic pyrolysis of low-density polyethylene (LDPE) using Y-type zeolites as catalysts without an external hydrogen supply, all of which can be conducted in one step under atmospheric pressure in a fixed-bed reactor. The Y zeolite catalysts, including HY, HUSY, and Meso-HY, are compared, and the influences of feedstock-to-catalyst ratio and pyrolysis temperatures on the yield and composition of the resulting fuels are evaluated. The optimal conditions are identified to use the Meso-HY catalyst with a feedstock-to-catalyst mass ratio of 3:2 at 500 °C, achieving an optimum SAF component selectivity of 78 area% and SAF fractions’ yield of 54.13 wt %. The resultant liquid fuel exhibits a high selectivity of isoalkanes (51 area%) and relatively low selectivity of aromatics (21.9 area%). The superior performance of the Meso-HY catalyst is attributed to its mesoporous structure and weak acidity, which favor the formation of isoalkanes. Additionally, a novel Fe/Meso-HY catalyst with magnetic properties has been developed to facilitate catalyst recovery after pyrolysis, showing good stability and minimal impact on isomerization efficiency. Hydrogen transfer during pyrolysis is explored by combining experiments and ReaxFF MD simulations; and a reaction pathway elucidating the mechanism of hydrogen self-supply during LDPE isomerization has also been proposed. The findings offer a foundational understanding required for producing SAF from waste plastics and provide valuable insights into the optimization of the production methods.