Hydroprocessing of synthetic kerosene over a non-sulphided Ni/Al2O3 catalyst: Impact of alcohols and ketones on alkene conversion

Abstract

Synthetic jet fuel containing non-petroleum-derived kerosene can be produced from synthetic kerosene obtained through processes that include a hydroprocessing step. The potential use of non-sulphided (reduced) nickel supported on alumina (Ni/Al₂O₃) was evaluated as an alternative to sulphided catalysts to saturate alkenes in sulphur-free synthetic kerosene during hydrotreating operations. Performance of a 5 wt.% Ni/Al₂O₃ catalyst for hydrotreating a model feed comprising n-decane, 1-dodecene, and cumenes was evaluated at 50°C–220°C, 2 MPa, weight hourly space velocity of 1.75 h⁻¹, and a normal volumetric H₂-to-feed ratio of 500 m³/m³. At 50°C–110°C, alkene conversion was incomplete. Initial selectivity of alkene conversion was 20%–40% toward double bond isomerization (catalyzed by Ni) and about 60%–80% toward hydrogenation to alkanes. Aromatic saturation under these conditions was <4%. At 220°C, alkene saturation was nearly complete, and aromatic saturation was 40%–50%. A kerosene hydrotreater with steam heating, as opposed to furnace heating, could therefore be considered when using non-sulphided Ni/Al₂O₃. Additionally, the impact of co-feeding 1-octene with oxygenates was determined. At 100°C, the presence of either alcohol or ketone co-feed suppressed alkene conversion and shifted the selectivity toward double bond isomerization. These effects persisted after the oxygenate co-feed was discontinued. At 220°C, co-feeding alcohol led to near-complete alkene conversion, but suppressed aromatic conversion, while oxygenate conversion remained incomplete. The threshold oxygenate tolerance of the catalyst was not established. In conclusion, the non-sulphided Ni/Al₂O₃ could be used for hydrotreating sulphur-free synthetic kerosene to saturate alkenes; however, its performance is adversely affected when the feed contains oxygenates at percentage levels.