Conversion of hydrous bio-ethanol on Zn_xZr_yO_z catalyst to renewable liquid chemicals and additives to gasoline

The conversion of ethanol on the Zn_xZr_yO_z catalyst was studied over a wide range of operating conditions to determine the possibility of producing organic liquid (olefins, aromatics and oxygenates). The content of water in the feed was found to be the key parameter. At ≥60 wt% water, no organic liquid is formed. As water content decreased, the yield of organic liquid increased. Furthermore, increasing pressure increased the yield of organic liquids. Experiments conducted at increasing residence time indicated that ethanol was first converted to oxygenates then to aromatics and higher olefins (C₅–C₁₁) with propylene, ethylene, carbon dioxide and hydrogen as the main by-products. Increasing temperature at high residence time (WHSV = 0.8 h⁻¹) decreased the yield of liquid oxygenates while increasing the yield of aromatics and higher olefins. A tentative scheme of reactions was proposed considering the special nature of the Zn_xZr_yO_z catalyst with balanced basic-acidic sites. The catalyst was stable, tested for >300 h. Tail gas containing light olefins, mainly propylene and ethylene, was converted by oligomerization on a commercial H-ZSM-5 catalyst to higher olefins (>90%) and aromatics at high conversion (>90%). The organic liquid from the two reactors can be used as feedstock for chemicals or as blending stock for gasoline.