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 N-2 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).