Tandem Oligomerization of Ethylene for Production of Jet Fuel over FER and MFI Zeolites

This work studied ethylene oligomerization as a sustainable pathway to produce jet fuel over tandem zeolite-based catalysts. We investigated three zeolites HFER, HZSM-5, and HBeta with different pore topologies in the first oligomerization step and assessed HZSM-5 zeolite as the second oligomerization catalyst by varying the SiO2/Al2O3 ratio. A series of tandem catalysts including PM (physically mixed) and DB (dual-bed) catalysts were compared to determine the best activity and selectivity toward C9+ hydrocarbons. HFER zeolite with small and medium pores showed significantly higher selectivity to C4–C8 olefins (especially C6 olefins). In comparison, the HZSM-5 zeolite exhibited superior activity and produced more C9+ products with an optimal SiO2/Al2O3 ratio of 180. Tandem catalysts by using HFER and HZSM-5 zeolites obtained higher yields of C9+ hydrocarbons with an increase of 19–22% than when single HZSM-5 zeolite was used. This synergistic effect was ascribed to a lower reactivity of hydrogen transfer over the HFER zeolite and sequential oligomerization of C4–C8 olefins by the HZSM-5 zeolite at high conversion. Due to the closer micrometer-scale intimacy of active sites, the PM catalyst demonstrated a relatively better stability than the DB catalyst with millimeter-scale proximity.