Pt/V/MCM-41 has a high activity for the selective catalytic reduction (SCR) of NO with C3H6 over a wide temperature range. Its broad activity-temperature window is due to three different reactions occurring in each different temperature range. One of these reactions is the reaction occurring on usual Pt-based catalysts. The experimental result of Pt dispersion effect suggested that this reaction follows the redox mechanism. The second reaction is that of molecularly adsorbed NO on Pt with surface carbonaceous species on Pt/V/MCM-41. Experiments for the reaction of NO with carbonaceous materials present on Pt/V/MCM-41 used in the SCR of NO confirmed that carbonaceous species can take part in the reaction. The third reaction is that occurring on support V/MCM-41. (C) 2003 Elsevier Science B.V. All rights reserved.