ISOTOPIC TRANSIENT KINETIC-ANALYSIS OF ETHANE HYDROGENOLYSIS ON RU/SIO2

Steady-state isotropic transient kinetics analysis has been applied to determine attributes of the active intermediates and the surface kinetics of ethane hydrogenolysis, known to be a very structure-sensitive reaction, on Ru/SiO2. The abundances, coverages, and lifetimes of surface intermediates of the reaction were measured under reaction conditions and their dependence upon temperature was determined. The results show that intrinsic activities and abundances of surface di-carbon and mono-carbon species change in different ways with temperature. The surface coverage of di-carbon species is much lower than that of mono-carbon species, while the reactivity of the mono-carbon species is greater than that of the di-carbon species. The surface coverage of di-carbon species was not found to change with temperature under the conditions studied, while that of mono carbon species increased with increasing temperature. The results suggest that the breakage of the C-C bond is the slowest step for ethane hydrogenolysis. The activation energies of the surface reactions of di- and mono-carbon species were found to be 36 +/- 3 and 9 +/- 3 kcal/mole, respectively. The exchange reaction of ethane with deuterium was also investigated in order to understand better the reaction mechanism. (C) 1995 Academic Press, Inc.