In order to improve a "Three Function Catalysts Model", the present paper deals with alumina based catalysts containing cobalt and palladium for the NO reduction by methane. The deNO(x) temperature window was estimated by adsorption and subsequent desorption of NO in lean conditions. Two NO, desorption peaks were detected for both catalysts. For Pd(0.63)Co(0.58)/Al2O3, the two desorption peaks appeared at 205 and 423 degrees C, whereas for Pd(0.14)Co(0.57)/Al2O3, the maxima desorption temperature peaks were at 205 and 487 degrees C. In addition, NO oxidation was also studied to evaluate the catalyst first function. It was found that, the oxidation begins on Co-Pd/Al2O3 around 250 degrees C. On Pd(0.63)Co(0.8)/Al2O3, 8% of deNO(x) were found in the range of the second NO, desorption peak temperature (410 degrees C). During TPSR, CxHyOz species such as formaldehyde were detected. These oxygenate species are the reactive intermediate for deNO(x) by methane. (c) 2006 Elsevier B.V. All rights reserved.