Reaction Kinetics of Aged NOx Storage Catalysts

Abstract

NOx storage catalysts (NSCs) are utilized to reduce the emissions in lean-burning engines such as diesel and lean-burn Otto engines. One of the current limitations of this technology is catalyst aging due to high-temperature excursions. To guarantee high conversions and to adapt engine and catalyst management, simulations of the exhaust line require a proper description of the conversion behavior of aged NSCs. Because of their complex chemical constitution (three precious metals, two storage components), kinetic models of NSCs encompass a large number of model parameters, which are determined from extensive experimental investigations. In this contribution, we show that the kinetics of aged NSCs can be derived from the kinetics of the fresh catalyst plus a relatively small set of experiments needed to quantify catalyst degradation. Seven scaling factors are necessary, which can be regressed one by one from simple test experiments. The scaling factors account for precious-metal sintering, reduced barium an...