The activity of carbonyl cluster derived [formula omitted] and [formula omitted] catalysts in CO hydrogenation

Abstract

We studied systematically the use of tetranuclear cobalt, cobalt-ruthenium, cobalt-rhodium and rhodium carbonyl clusters as catalyst precursors. The catalytic activities and the product distributions of the hydrogenation of carbon monoxide over Co 4−nRu n SiO 2 and Co 4−nRh n SiO 2 catalysts (where n = 0−4) and (Co 4 + Ru 4) SiO 2 and (Co 4 + Rh 4) SiO 2 catalysts derived from the transition-metal carbonyl clusters were compared. Activities were highest for the catalysts derived from homometallic clusters, and lowest for catalysts with 1:1 ratio of Co Ru or Co Rh . Interestingly enough, the highly active homometallic cobalt catalyst was the most resistant to deactivation. On Co 4−nRh n SiO 2 catalysts the deactivation was stronger on bimetallic sites and on the Co 4−nRu n SiO 2 catalysts the deactivation was closely related to the presence of ruthenium. The selectivities for oxygenated compounds were clearly promoted by the bimetallic sites of Co-Rh catalysts. This result is very plausible since the probability to find dual active sites responsible for the formation of oxygenates is greater in bimetallic than in homometallic catalysts.