In situ FTIR spectra of adsorbed O-2 and CH4 at different temperatures were obtained from 5 wt.% Pd/Al2O3 and Pd/Co3O4 catalysts. It was found that O-2 can be easily adsorbed on these catalysts to form reactive species, which appear at different bands with the change of temperature and the kind of the oxide support. These can explain why the catalytic activities of these Pd-containing catalysts are so dependent on the temperature and the oxide support. For CH4 adsorption, even at the temperature above light-off temperature, no adsorbed species of CH4 were detected by IR. In situ methane oxidation IR spectra proved that the intermediates of HCOO- and CO3- are formed during reaction, which decompose to form CO and CO2, respectively. (C) 2002 Published by Elsevier Science B.V.