Experimental investigation of the reduction of NOx species by CO over Pt-Ba/Al2O3 Lean NOx Trap systems

Introduction Lean NOx Traps (LNTs) represent a viable solution for the abatement of NOx emissions from lean–burn engines [1]. Several studies were published on the mechanisms of both the NOx storage [1] and reduction [2], but a complete understanding of these processes has not yet been achieved. We have previously shown that on Pt-Ba/Al2O3 LNT systems the reduction of nitrates by H2 involves a catalytic pathway involving Pt, and is not initiated by the thermal decomposition of the stored NOx ad-species [2]. We also showed that this process involves a 2-steps in series molecular pathway in which NH3 is formed as intermediate [3]. In this study the reaction mechanism involved in the reduction of stored NOx when CO is used as reducing agent are analyzed, and the pathways originating the main reduction product (N2) are addressed.