A wire microcalorimetric study of catalytic ignition of methane-air mixtures over palladium oxide

Catalytic ignition and heat release of methane oxidation over a Pd wire covered with a 1-2 mu m PdO surface layer were investigated by wire microcalorimetry over the temperature range of 600-770 K and pressure range of 0.5-4 atm. Ignition temperatures and heat release rates for different methane concentrations (1-4 vol.% in dry air) were determined, showing that the ignition temperatures decrease with increasing the methane concentration and increasing ambient pressure. At total pressure of 1 atm and 2% methane concentration, the global activation energy for the catalytic reaction is 21.5 +/- 0.9 kcal/mol and 14.3 +/- 0.2 kcal/mol in the temperature ranges of 600-670 K and 670-770 K, respectively. The reaction order for methane is 0.9 +/- 0.1 over the temperature range of 630-770 K. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.