CATALYTIC PROPERTIES OF NIX ZEOLITES IN THE PRESENCE OF CERIUM ADDITIVES

Cerium-containing NiX zeolites were prepared by the method of incipient-wetness impregnation. The nickel dispersion and the catalytic properties of the prepared catalysts were dependent on the Ce3+-to-Ni2+ ratio in zeolites. In the presence of cerium additives, NiX zeolites are able to exhibit a remarkable increase in nickel dispersion, and an enhanced reactivity in carbon monoxide hydrogenation with a shift of the product selectivity to heavier hydrocarbons. The results can be ascribed to the presence of the highly polarizing Ce3+ ions which induced some kind of metal-support interactions and thus led to the greater reducibility of nickel, to more accessible sites for carbon monoxide adsorption and to a larger surface concentration of hydrogen, which enhanced the hydrogen-assisted carbon monoxide dissociation during carbon monoxide-hydrogen reactions. The Ce3+ cations acted not only as "chemical anchors" but also as catalyst promoters. © 1990.