Turnover rate and reaction orders for the complete oxidation of methane ona palladium foil in excess dioxygen

The turnover rate and reaction orders for the combustion of methane in exce ss oxygen over Pd foils were in agreement with literature results reported for supported catalysts. The rate equation was r = k[CH4](0.7)[O-2](0.2)[H2 O] (-0.9). The turnover rate on the Pd foil was 59 x 10(-2) s(-1) at 550 K, 160 Torr O-2, 16 Ton CH4, 1 Torr H2O, and N-2 balance to 800 Ton; with the number of active sites defined as the number of surface Pd atoms calculate d from the initial geometric area of the foil. This rate is 3 times higher than the highest value reported in the literature for supported catalysts. The surface area of the foil, measured by isotopic exchange of surface oxyg en with O-18(2), increased by a factor of approximately 2 after reaction, T he main species observed on the surface after reaction by XPS was PdO, Samp le activation during the reaction was not observed. The reaction was carrie d out in a batch reactor at 598 K and atmospheric pressure with characteriz ation before and after reaction by X-ray and Auger spectroscopies and tempe rature-programmed desorption, (C) 2001 Academic Press.