STUDIES ON RUTHENIUM CATALYSTS .1. REACTIONS OF CYCLOPROPANE AND OF ETHANE WITH HYDROGEN ON RUTHENIUM TITANIA CATALYSTS - REACTION-MECHANISMS

The hydrogenation of cyclopropane to propane is accompanied by hydrogenolysis to equimolar amounts of methane and ethane on a Ru/TiO2 catalyst pretreated both by high- and low-temperature reduction (HTR or LTR). The rate after oxidation and LTR is much faster than after a second HTR, when (due to the absence of Cl-) the catalyst enters the SMSI state. Even more marked variations of rate with pretreatment are found with ethane. Cleavage of the second C - C bond in cyclopropane is detectable just above room temperature, where the (extrapolated) rates for propane and ethane hydrogenolysis would be negligible. Previous proposals to account for this process are examined, and found wanting. The dissociation of cyclopropane into adsorbed methylene and ethene is thought to be a more plausible route to the hydrogenolysis products.