Influence of the support acidity of Pt/aluminum-silicate catalysts on the continuous reduction of NO under lean conditions

This study focuses on the influence of the support acidity on the continuous reduction of nitric oxide by hydrocarbons over supported Pt catalysts under lean conditions. The support materials used were alumina, silica and co-precipitated aluminum-silicates. Activity studies of NO reduction with either propene or propane as the reducing agent, CO chemisorption, CO oxidation, isopropylamine temperature programmed desorption (TPD) and ammonia TPD experiments have been performed. The isopropylamine TPD experiments indicated the presence of Brّnsted acid sites in the samples that contained alumina. The activity for NO reduction and the selectivity for N2 formation with propene as the reducing agent showed no pronounced differences between the samples studied. For propane, on the other hand, expressed differences in NO reduction activity between the samples were observed. The activation of propane and consequently the reduction of NO, seemed to be promoted by the presence of acidic sites on the surface of the support. The selectivity towards N2 formation seemed to be strongly connected to the amount of Brّnsted acid sites present in the samples.