Temperature-programmed FT-IR study of the adsorption of CO and co-adsorption of CO and H-2 on Ni/Al2O3

The adsorption of CO and co-adsorption of CO and H-2, On Ni/Al2O3 catalyst prepared by a distinct procedure were studied by means of FT-IR technique. The study shows that only one kind of CO adsorption site - the linear CO adsorption site - exists on the Ni/Al2O3 catalyst used in present work. Temperature-programmed heating of CO adspecies in CO atmosphere reveals that the disproportionation of linearly adsorbed CO may occur at above 473 K. In H-2 + CO atmosphere, a new IR band centered near 1910 cm(-1) emerges, the intensity of which increases and decreases concomitantly with that of the band centered about 2050 cm(-1) with increasing temperature, indicating the occurrence of a new adspecies in the dynamic process of CO hydrogenation under reaction conditions. This new adspecies is tentatively ascribed to nickel carbonyl hydride species. The methanation of CO on Ni/Al2O3 may occur via a mechanism involving the formation of nickel carbonyl hydride species.