Selective catalytic reduction of NO by propene in excess oxygen on Pt- andRh-supported alumina catalysts

A comparative study of Pt/alumina and Rh/alumina catalysts was performed fo r the selective catalytic reduction of NO with C3H6 in the presence of exce ss oxygen. Pt/alumina was more active for NO reduction at lower temperature s compared to Pi/alumina. However, the latter exhibited clearly superior pe rformance in terms of selectivity to N-2. This makes Rh/alumina a more suit able catalyst for the selective catalytic reduction of NO under excess oxyg en conditions. Detailed kinetic studies of the SCP of NO were performed on Pt/alumina and Pi/alumina to obtain low-temperature kinetic expressions for NO reduction and C3H6 oxidation in the presence and absence of NO. Qualita tive similarities yet quantitative differences in these kinetic expressions appear to indicate the existence of two partially similar mechanistic sche mes. One is based on the indirect participation of the reductant through re duction of the active sites, followed by dissociative adsorption of NO on r educed sites (applicable for Pt/alumina). The other is based on the direct participation of the reductant (apparently by its partial oxidation) in for ming an activated intermediate species, followed by its interaction with ac tivated NO (applicable for Rh/alumina). (C)1999 Elsevier Science B.V. All r ights reserved.