ALKENE AND ARENE COMBUSTION ON PD(111)

Oxidation reactions of ethene, propene, 1-butene, 1,3-butadiene, benze ne, and toluene were studied on oxygen-precovered Pd(111) (0.25 ML-1.2 ML) using temperature-programmed reaction spectroscopy (TPRS). Combus tion is the sole reaction pathway; no partial oxidation products are f ormed. Comparison of these results with those from Pd(100) demonstrate s that the structure of the metal surface does not significantly affec t the mechanism of catalytic oxidation of most of the olefins or aroma tic hydrocarbons studied, although, in general, combustion occurs at h igher temperatures on Pd(111). Only for benzene combustion is there an appreciable structure sensitivity. For all the hydrocarbons studied t he CO2 and CO yields are maximized for an oxygen precoverage of 0.34 o xygen atoms per surface palladium atom. Abrupt increases in carbon oxi de production at specific oxygen coverages indicate that oxygen-induce d surface reconstructions may play a role In the combustion activity. (C) 1998 Academic Press.