NOx Adsorption Over Ce/Zr-Based Catalysts Doped with Cu and Ba

In this study, Ce/Zr-based materials without noble metals in their formulation have been prepared, characterized and tested in NOx adsorption at different temperatures. In particular, the effect of the presence of Ba and Cu in the catalytic formulation has been investigated. The catalyst characterization shows that the redox properties of the catalysts are enhanced by Cu and inhibited by Ba. Upon interaction with NO/O2, it is found that NOx are stored at low temperatures (150 °C) in the form of nitrites, without any relevant NO oxidation activity. This suggests a direct NO uptake. At higher temperatures (300 °C) a significant NO oxidation activity is observed, that is enhanced by Cu and depressed by Ba. In this case, NOx are stored in the form of nitrates; the samples containing both Ba and Cu exhibits the better performances in terms of NOx adsorption capacity.