Influence of Pt Loading in Aged NOx Storage and Reduction Catalysts

A series of Pt/BaO/Al2O3 samples have been prepared with nominal Pt loadings ranging from 0.5 to 3.5 wt %. These samples were characterized in their fresh state and then subjected to an accelerated, mild, aging process which involved exposure of the catalysts to alternating rich and lean gas mixtures at 773 K. Characterization and storage results for the aged catalysts have been obtained. Aging effects were dependent on Pt loadings although there was no clear correlation between loading and the extent to which dispersion was lost during the accelerated aging process. Particular attention was given to the loadings and their temperature sensitive impacts on the form of the storage and release profiles including the NOx release spike accompanying the switch from lean to rich operation. Higher Pt loadings reduce the extent of NOx slip during lean to rich transition for low temperature operation.