METHANE COUPLING AT LOW-TEMPERATURES ON RU(0001) AND RU-11(2)BAR-0 CATALYSTS

The conversion of methane to higher hydrocarbons on single crystal Ru catalysts has been investigated using combined elevated-pressure kinetic measurements/surface science studies. The reaction consists of activation of methane on Ru(0001) and Ru(1120BAR) surfaces to produce carbonaceous intermediates at temperatures (T(CH4)) between 350 and 700 K and rehydrogenation of these species to ethane and propane at T(H2) almost-equal-to 370 K. It is found that under the reaction conditions employed, the maximum yield in ethane/propane production occurs at T(CH4) almost-equal-to 500 K on both surfaces. Influence of the hydrogenation temperature on the production of ethane and propane is also examined. On Ru(0001), the yields of ethane and propane maximize at T(H2) = 400 K, whereas no maximum yield was observed on Ru(1120BAR) in the 300-500 K temperature range. Under optimum reaction conditions, hydrocarbon products consist of 16% ethane and 2% propane. High-resolution electron energy-loss spectroscopy (HREELS) has been used to identify various forms of hydrocarbonaceous intermediates following methane decomposition. An effort is made to relate the hydrocarbon intermediates identified by HREELS to the gas phase products observed in the elevated pressure experiments.