Selective catalytic reduction (SCR) with NH3 and most probably with urea is unanimously regarded as one of the most promising technologies for the abatement of NO, on-board. For this application at low temperatures. carbon-based monolithic catalysts have been prepared using, a blend of polymers on cordieritc monoliths, doped with two different vanadium compounds and two different loadings (3 and 5%). The active phase precursors were either the ashes of a petroleum coke (PCA) ora commercial NH4VO3. An experimental design was carried out to study the reduction of NO emissions, the selectivity towards N-2 and the release of ammonia-slip in the outlet reactor gasses. Both primary measures (temperature. gas space velocity per hour (GSVH) and the molar ratio of NH3/NO) as well as secondary SNR influences were evaluated using a 2(3) factorial design for the two types of catalysts. Polinomial modellings were deducted from statistical analysis of the experiments, and a good agreement between models and measured data was obtained. The evaluation showed that the temperature is the variable which has a greater influence on all the response variables studied. Spatial velocity shows approximately an equal importance on NO conversion and selectivity towards N-2 whereas the molar ratio of NH3/NO is only an important factor in the interaction to other parameters. Catalysts prepared using PCA have similar catalytic behaviour than those prepared with NH4VO3. Although they show a slightly lower catalytic activity, similar selectivity towards N-2 and higher values of ammonia-slip. The physical-chemical features of the catalysts, analysed by N-2 physisorption, ammonia adsorption and temperature programme desorption have a close relation with the catalysts behaviour. The physical-chemical features are of key importance for achieving a considerable catalytic activity. The values of apparent activation energy calculated for the catalysts presented in this paper were similar to other carbon-based catalysts and smaller than the ones Corresponding to TiO2-supported systems. (c) 2008 Elsevier B.V All rights reserved.