A Low Temperature Pathway Operating the Reduction of Stored Nitrates in Pt-Ba/Al2O3 Lean NOx Trap Systems

In this paper the low temperature reduction process of nitrates stored at high temperatures over model Pt-Ba/Al₂O₃ LNT catalysts using both H₂ and C₃H₆ is analyzed. The results indicate that over the Pt-Ba/Al₂O₃ catalyst the reduction of stored NO_x with both H₂ and C₃H₆ occurs at temperature below those corresponding to their thermal stability. Accordingly, the reduction process occurs through a Pt-catalyzed surface reaction, which does not involve, as a preliminary step, the thermal decomposition of the adsorbed NO_x species. The occurrence of such a pathway also requires the co-presence of the storage element and of the noble metal on the same support.