Chapter 10: Global Kinetic Modelling of the NSR Catalysts

This chapter focuses on a global kinetic model of NO_x storage and reduction catalyst that serves as an effective software tool for design and optimization of exhaust gas aftertreatment systems in the automotive industry. Only key adsorbed components are considered and individual reaction steps on the surface are lumped into global reactions to minimize the system complexity. The aim is to predict the catalyst performance in a wide range of temperatures, flow rates and component concentrations in real exhaust mixture under highly dynamic operating conditions, enabling the optimization of monolith configuration and location in the exhaust treatment line, lean and rich phase timing, rich mixture composition, and LNT interaction with the other catalysts in the exhaust aftertreatment system (such as DOC and SCR). First, suitable transport models for monolith channel, catalytic washcoat and surface particle scale are introduced. The formulation of global rate laws is then discussed for main reactions that take place on the Pt(Pd)Rh/BaO/CeO₂/Al₂O₃ catalyst type under varying air–fuel ratio: CO, H₂ and hydrocarbon oxidation, water–gas shift and steam reforming, steady NO reduction, NO oxidation, NO₂ reduction, oxygen storage effects, NO_x adsorption, and reduction of the stored NO_x that includes temporally and spatially distributed formation of by-products (N₂, NH₃ and N_xO) during the catalyst regeneration.