Labelled 15NO experiments for the study of NOx reduction over Pt-Ba/Al2O3 LNT catalyst

Lean NOx Traps (LNT) are considered to be one of the most promising solutions for NOx removal from lean burn engine exhausts. Recently, the reduction by H2 of NOx stored onto a Pt-Ba/Al2O3 LNT model catalyst has been studied in our labs and a reduction pathway has been proposed. The reduction proceeds trough a 2-steps in series molecular pathway, in which the first step (fast) is the reduction of stored NOx with H2 giving the formation of NH3. in the second step (slow) the so formed ammonia reacts with residual stored NOx to give N2. The present study aims to better elucidate the pathways involved in the reduction of the stored NOx, and in particular the second step of the proposed mechanism for N2 formation involving stored NOx and ammonia. For this purpose experiments have been carried out using isotopically labelled molecules and different reductants, including H2 and NH3.