Effect of carbon black combustion on NOx trap catalyst performances

The effect of carbon–NSR catalyst contact on the ability of the catalyst to store NOx is investigated. The catalysts used are model catalysts composed of Pt and/or Ba supported on Al2O3 (2%Pt/γ-Al2O3, 20%BaO/γ-Al2O3 and 2%Pt–20%BaO/γ-Al2O3). It is shown that the presence of carbon black in the catalytic bed involves a decrease of the NOx storage capacity (NSC) of the catalysts. Participation of a direct reaction between carbon particles and NOx storage sites to form carbonate adsorbed species is proposed. However, the loss of NSC measured in the presence of carbon varies as a function of the catalyst composition. It is shown that the presence of platinum limits the influence of carbon–catalyst contact. The influence of the proximity between the storage sites, Pt sites and their contact with carbon is discussed.