Effects of Surface Modification of H-ZSM-5 Catalysts on Direct Transformation of Ethanol into Lower Olefins

Various H-ZSM-5 catalysts were assessed for ethanol conversion into lower olefins. Ethanol was converted to lower olefins over H-ZSM-5 catalyst without modification. The selectivities for ethylene and propylene were much lower than those for aromatics such as benzene, toluene, and xylene (BTX), and C1-C4 saturated hydrocarbons. Addition of W and La was found to reduce aromatization and olefin hydrogenation, and, under ethanol conversion of almost 100%, the selectivity for propylene and ethylene was improved, whereas the selectivity for BTX was decreased. The amount of carbon deposit was almost the same as that without modification. The selectivity for propylene formation may be associated with the percentage of Brønsted acid sites on the catalyst surface.