Determination of the NO(x) Loading of an Automotive Lean NO(x) Trap by Directly Monitoring the Electrical Properties of the Catalyst Material Itself

Recently, it has been shown that the degree of loading of several types of automotive exhaust aftertreatment devices can be directly monitored in situ and in a contactless way by a microwave-based method. The goal of this study was to clarify whether this method can also be applied to NO(x) storage and reduction catalysts (lean NO(x) traps) in order to obtain further knowledge about the reactions occurring in the catalyst and to compare the results with those obtained by wirebound NO(x) loading sensors. It is shown that both methods are able to detect the different catalyst loading states. However, the sensitivity of the microwave-based method turned out to be small compared to that previously observed for other exhaust aftertreatment devices. This may limit the practical applicability of the microwave-based NO(x) loading detection in lean NO(x) traps.