In this work we study a catalytic reaction model among three monomers in order to understand the chemical kinetics of the selective catalytic reduction of nitrogen oxide by ammonia (4NO + 4NH3 + O2 → 4N2 + 6H2O). Our model takes into account the formation of the intermediate species in the global scheme of the reaction. In order to determine the dynamical behaviour of the model we used single site approximation method. In this approach we have observed that, depending on the values of the control parameters, the model presents an active or an inactive phase. In fact, the dynamical phase diagram of the model exhibits a first order line separating these two phases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)