Unraveling the Role of HZSM-5 Zeolite Catalyst Acid Properties in Fuel Production and Coke Deactivation in Low-Pressure Ethylene Oligomerization

A series of experimental runs have been carried out for the ethylene oligomerization process at slightly above atmospheric pressure (1.5 bar) using three catalysts prepared with HZSM-5 zeolites of different Si/Al ratio (15−140). The aim is to determine the Si/Al ratio of greater interest for the reaction. For that purpose, the kinetic results have been evaluated in terms of ethylene conversion and main lumped product yields (especially C₅₊ lump, within gasoline fraction), by also considering the nature (olefinic, paraffinic, or aromatic) of the different hydrocarbons formed, to elucidate their role in the proposed oligomerization reaction network. Furthermore, the effect of the Si/Al ratio of the zeolite on the liquid products obtained as fuel blends has also been analyzed, aiming to maximize the gasoline and jet fuel fractions. Finally, an extensive study of coke deactivation is included using several characterization techniques (N₂-TPS-TPO, GC/MS of soluble coke). This study has allowed us to distinguish between the content and location of the soft coke (retained oligomers) and hard coke (more developed carbonaceous species) by also providing information about the composition of the coke precursors (light adsorbed compounds) and intermediate species evolving toward hard coke.