An EXAFS study of the interaction of different reactant gases over nanometer scale Pt clusters deposited on gamma-Al2O3

Face to the difficulty to find an efficient catalyst in the reduction of NO by hydrocarbon in diesel exhaust gases, we have examined the interaction o f some concerned reactant gases, NO, C3H6 and O-2, with a catalyst constitu ted of nanometer scale platinum particles deposited on alumina. Indeed, in order to understand the catalytic process, it seems essential to have infor mation on the adsorption process and on the evolution of the structural par ameters of the particles when submitted to such gases. This work has been p erformed on a 1% Pt/Al2O3 catalyst by using in situ EXAFS measurements. We have concentrated our study, on the one hand, on the influence of NO, C3H6 in the presence or not of an excess of oxygen and, on the other hand, on th e influence of the total mixture. The most striking result is the growth of the platinum particles under NO. Moreover, when the catalyst is submitted either to a mixture of NO + O-2 or C3H6 + O-2, the particles are not fully oxidised. With the total mixture, the particles both grow and are oxidised.