Catalytic properties of catalysts derived from supported H 3Re 3(CO) 12

Abstract

Supported rhenium catalysts prepared by immobilization of H 3Re 3-(CO) 12 clusters on silica, alumina and titania were tested with regard to their activity in hydrogenolysis and dehydrogenation of hydrocarbons. Activity tests were carried out at 400 °C using a micropulse reactor and hydrogen-containing carrier gas. Depending on the reactant and the catalyst, either hydrogenolysis or dehydrogenation was prevalent. Hydrogenolysis of n-heptane and 2,2-dimethylbutane occurred over all catalysts, indicating that under the reaction conditions the rhenium existed as larger groupings of rhenium metal atoms and not as isolated monomeric rhenium complexes. Thus the originally well-dispersed rhenium underwent migration to finally form small rhenium clusters. Highest hydrogenolysis activity was observed for the titania-supported rhenium catalysts. Silica- and alumina-supported rhenium exhibited selective dehydrogenation of cyclopentane and methyl-cyclopentane to cyclopentene and methylcyclopentene, respectively. On the titania-supported rhenium, hydrogenolysis was the dominant reaction observed with cyclopentane and methylcyclopentane.