(180a) Multi-Layer Monolith Catalysts for Lean NOx Reduction

The challenge of  achieving high NOx conversion and N₂ selectivity and minimal release of unreacted NOx and NH₃ in lean burn vehicle emission aftertreatment calls for structured catalysts with multiple functions.  We describe experimental and modeling studies of three different multi-layer applications. The first application combines Fe- and Cu-exchanged zeolitic layers to expand the high NOx conversion temperature range.  The second application combines periodic NOx storage and reduction with in situ NH₃ generation and selective catalytic reduction.  The third application combines a Pt/Al₂O₃ bottom layer and a zeolitic toplayer to oxidize NH₃ with high selectivity to N₂.