Catalytic pyrolysis of low-density polyethylene to produce sustainable aviation fuel fractions: Improving isomerized alkane selectivity via magnetic metal-modified HY zeolites

To produce isomerized sustainable aviation fuel (SAF) fractions through plastic wastes' atmospheric pyrolysis is rarely reported. This study addresses the catalytic pyrolysis of low-density polyethylene (LDPE) over magnetic metal-modified HY zeolite catalysts for producing isomerized alkane-type SAF fractions without requiring external hydrogen in an atmospheric fixed-bed reactor. The findings reveal that a lower Si/Al ratio enhances the formation of acid sites on the HY zeolite, which results in increased olefin conversion and produces oil with alkanes' selectivity achieving 60 area%, especially HY12 shows the best performance. The introduction of three magnetic metal oxides (Fe, Co, and Ni) into HY12 changes the acid site distribution with the strong to weak acid site ratio ranging from 0.18 to 0.31. It elevates isomerized alkanes’ selectivity in the aviation fuel range to more than 50 area%. The 6 wt% Fe2O3/HY12 catalyst corresponds to an iso-alkane selectivity of 51.57 area%, a total SAF fraction selectivity of 84.27 area% and an oil yield of 74.33 wt%. Furthermore, this catalyst operates without pre-reduction as the metal oxides can be reduced in situ during pyrolysis, and it also allows for the magnetic recovery of the spent catalyst. Finally, the mechanism for the formation of iso-alkanes and coke deposition onto the catalyst has been proposed. This research provides essential insights for optimizing plastic waste pyrolysis for preparing SAF and tailoring its composition.