Simultaneous effect of carbon and water on NOx adsorption on a stabilized Pt-Ba/Al2O3 catalyst

The influence of the presence of H2O on the contact between carbon, used as model soot, and a model four-way catalyst (1% Pt-10% BaO/Al2O3) was investigated. NOx adsorption/TPD cycles at 300 degrees C together with XRD, XPS and DRIFTS characterizations showed that only surface nitrate species are destabilized by the carbon present in the catalytic bed, leading to a decrease of the NOx storage capacity and carbonate species formation. In another way, injection of water in the reactive gas flow decreases also the NOx storage capacity of the catalyst, but promotes the formation of stable nitrate species. A non-cumulative effect of carbon and water was observed. It was proposed that a competition between the destabilization, by carbon, of weakly bonded surface nitrate species and the enhancement of bulk nitrate species formation in the presence of water occurs. (C) 2014 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.