CORRELATION BETWEEN CHEMISORPTION AND THE MECHANISM OF CARBON-MONOXIDE HYDROGENATION OVER PT-CO/NAY CATALYSTS

A series of monometallic platinum and cobalt as well as Pt-Co/NaY bimetallic catalysts prepared by ion exchange were characterized by chemisorption of H-2, O2, CO and O2-H-2 titration along with their activity for carbon monoxide hydrogenation. The surface properties of platinum in the Pt-Co/NaY were modified by cobalt with an increasing cobalt mole fraction in the catalyst, which was evidenced by the continuous increase in the relative adsorption amount of oxygen and carbon monoxide compared to hydrogen. While the turn-over frequency of the overall reaction for carbon monoxide hydrogenation increases with cobalt content, maximum methanol selectivity is found for catalysts with optimum composition. The formation of Pt-Co bimetallic particles inside NaY-zeolite cages is proposed and the carbon monoxide hydrogenation results are correlated with the surface properties of the catalysts for both hydrogen and carbon monoxide adsorptions as well as for activation.