The oxidation state of Co, Pt and Rh containing MCM-41 after co-adsorption of NO, CH4, and O-2 in the presence of water vapor was studied by in situ XANES experiments. All catalysts were oxidized after the adsorption of NO and reduced after the coadsorption of NO and CH4. The presence of water vapor did not influence the oxidation/reduction of Rh/MCM-41 and Pt/MCM-41,while Co/MCM-41 was oxidized by the presence of H2O at reaction temperature.