Carbon-NSR catalyst interaction: Impact on catalyst structure and NOx storage efficiency

The impact of the presence of carbon on the structure of model NOx storage catalysts (NSR) and their ability to store NOx were investigated. Three catalysts, composed of Pt and/or Ba supported on Al2O3, were prepared. Reactivity of the catalysts toward NOx storage was studied during adsorption/TPD cycles. Comparison of the results obtained in the presence and absence of carbon in the catalytic bed revealed that a carbon-catalyst contact leads to a decrease in NOx storage capacity attributed to a destabilization of nitrate species formed far from Pt sites. Both Al and Ba sites are affected. During the carbon oxidation process, an aging of the catalysts, caused by Pt sintering and Ba agglomeration, as observed using TEM technology. These structural modifications reduce the proximity between the Pt sites and adsorption sites (Ba and/or Al), which results in a decrease in the NOx storage toward the 'nitrite route'. (C) 2013 Elsevier B.V. All rights reserved.