Catalysis by supported group VIII metal compounds I. The interaction of n -butene with hydrogen over silica-supported ruthenium carbonyl catalysts

Abstract

The reaction of but-1-ene with hydrogen and with deuterium has been studied over the temperature range 353–415K by using catalysts prepared from silica-supported triruthenium dodecacarbonyl. Infrared and radiochemical studies show that the supported complex undergoes decomposition in a series of well defined stages, and that in the temperature range studied the active catalyst is a ruthenium subcarbonyl containing five carbonyl ligands per ruthenium triad. Kinetics and activation energies for hydrogenation and hydroisomerization are reported, together with the variations in product distributions with hydrogen uptake and the distributions of deuterium in the reaction products. But-1-ene isomerization occurs in the absence of molecular hydrogen. The relative rates of hydrogenation of the n –butenes are in the order but-1-ene < cis -but-2-ene < trans -but-2-ene. The results are consistent with a mechanism in which hydrogenation occurs by the attack of molecular hydrogen on a π -butene metal complex, whereas isomerization involves a hydrogen abstraction–addition mechanism and the formation of a 1-methyl- π -allyl intermediate.