Modeling and Optimization of Multi-layer Structured Catalysts for Selective Elimination of NOx and NH3

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. The role of modeling is paramount in gaining a fundamental understanding of these catalytic reactors and in improving their design, control and operating strategies. The modeling of two different multi-layer catalysts will be described. The first application combines periodic NOx storage and reduction with in situ NH3 generation and selective catalytic reduction. The second application combines a Pt/Al2O3 bottom layer and a zeolitic top layer to oxidize NH3 with high selectivity to N2. The models are used to determine the thicknesses of the layers to properly exploit the coupling between reaction and transport.