Characterization and reactivity of Ce-promoted PtBa lean NOx trap catalysts

The effect of cerium addition to a model Pt-Ba/Al2O3 lean NOx trap catalyst (LNT) is investigated in this paper by a combination of characterization techniques and reactivity experiments. It is found that the presence of Ce does not alter the morphological and structural characteristics of the catalyst, although slight changes in the Ba-carbonate phase are apparent. On the other hand, the presence of Ce does not seem to affect significantly the characteristics of Pt, in particular its redox state. CO adsorption experiments pointed out the presence of Pt° particles presenting different coordination degree, whose characteristics are however not significantly affected by the presence of Ce. The storage capacity of the PtBa/Al sample is hardly affected by the presence of Ce; however Ce favours the thermal decomposition of the stored NOx species. The Ce-doped sample also shows a slightly higher reactivity in the reduction of the stored NOx by H2: in fact the reaction is monitored at lower temperatures. A slightly higher selectivity towards the formation of N2 is also observed.