Ethanol Conversion to Short-Chain Olefins Over ZSM-5 Zeolite Catalysts Enhanced with P, Fe, and Ni

The ethanol dehydration and subsequent ethylene oligomerization to short-chain olefins using catalysts based on ZSM-5 zeolite was studied in detail. P, Fe, and Ni were added by incipient wetness impregnation on zeolites with two SiO2/Al2O3 molar ratios (50 and 80). The catalysts were characterized by N2 adsorption–desorption, XRD, SEM–EDX, FTIR spectroscopy of adsorbed pyridine, and XPS techniques, while the catalytic activity was evaluated using an isothermal fixed-bed reactor. The impregnation of P, Fe, and Ni significantly improved the formation of the desired C3+ olefins (olefins having three or more C atoms). Particularly, the zeolite with SiO2/Al2O3 molar ratio = 50 and impregnated with P, exhibited the highest selectivity (C3+ olefins > 45 wt% at TOS = 5 h) in comparison with the rest of the evaluated catalysts. On the contrary, catalysts with SiO2/Al2O3 molar ratio = 80 showed lower selectivity to C3+ olefins, producing more side products (i.e. paraffins, aromatics and diethyl-ether).