The kinetics and mechanism of the reduction of NO and N2O by H-2 over Ag/Al2O3 were studied with transient step response and isotope exchange techniques, Dissociation of hydrogen and deuterium was observed on the Ag/alumina catalyst. The reduction of NO with hydrogen gave N-2 as the main product and N2O, NH3 and H2O as by-products, while the catalyst showed low activity for the self-decomposition of NO and N2O. To clarify the reaction mechanism for the reduction of NO with hydrogen parameter estimation and modeling was carried out. (c) 2005 Elsevier B.V. All rights reserved.