A Zeolite-Based Cascade System to Produce Jet Fuel from Ethylene Oligomerization

Jet fuel production from ethylene oligomerization opens a sustainable pathway to clean sulfur-free fuel that is increasingly in demand due to the potential renewable origin of ethylene. The key to a viable heterogeneously catalyzed process is to improve the selectivity of the jet fuel while prolonging the catalyst lifetime. To this end, we have assessed and optimized a dual-bed cascade system based on a dimerization bed that is followed by an oligomerization bed using Ni supported on Y zeolite and ZSM-5 zeolite catalysts, respectively. Our optimization approach uses different catalyst acidities, temperatures, and bed configurations for determining the best yield-conversion relationship. Under optimized dual-bed conditions, we can produce 64 wt % of jet fuel at the beginning of the reaction and maintain a 50 wt % selectivity of this fraction for over 20 h on stream. This paper also analyzes coke deposition (content and nature) at the different experimental conditions and catalyst bed arrangements using temperature-programmed combustion. We demonstrate that the dual-bed approach is effective for protecting the main oligomerization bed (ZSM-5 catalyst) from deactivation, leading to the formation of a lighter type of coke compared with that using the initial Ni²⁺HY-based dimerization catalyst, which deactivates at a faster rate.