Hydrogenation of Acetylene over Supported Metal Catalysts: Part 1.—Adsorption of [14C]Acetylene and [14C]Ethylene on Silica Supported Rhodium, Iridium and Palladium and Alumina Supported Palladium

Abstract

The adsorption of [14C]ethylene and [14C]acetylene on supported palladium, rhodium and iridium catalysts occurs irreversibly at 298 K in two distinct stages; a non-linear primary region, in which the species are predominantly dissociatively adsorbed, and a linear secondary region. Hydrogenation catalysis is associated with the hydrocarbon species adsorbed on the secondary region. From [14C]carbon monoxide adsorptions it is concluded that the hydrocarbon primary region is associated with the metal, whilst the secondary region probably involves the formation of overlayers on the primary adsorbed species. The co-adsorption of ethylene and acetylene shows that, under acetylene hydrogenation conditions, both are adsorbed at separate sites and undergo hydrogenation independently of each other. The relevance of these observations to the selective hydrogenation of acetylene is discussed.