(547d) NOx Storage Isocapacity Curves for Operation of NSR Catalysts

In order to optimise the global behaviour of the NSR catalyst two aspects should be foreseen. One is the chemical and structural characteristics of the catalyst itself (e.g. surface area of the alumina, metallic dispersions of active phases, etc.) [1]. But not less important are the operational conditions under which the catalyst has to operate in the automobile converter. In this sense, the concentration of the reductant agent, the duration of the lean and rich periods, and the temperature are the key variables to be considered. Most importantly, only such operational variables can be modified once the NSR catalyst has been already manufactured.

Information on how one given NSR catalyst will perform under real operation is of vital importance for car manufacturers, car assistance shops and car drivers. The motivation for this communication was to find any simple relation between the operational variables and the final behaviour of the catalyst referred as the NO_x storage capacity and selectivity to N₂, a tool which will be named ?operation map?. Also this kind of tool will allow one to compare easily the behaviour of catalysts supplied by several manufacturers. To the best of our knowledge, such or similar operation maps are not available in the literature.

The proposed theory will be verified with experimental data. Such "operation map" will relate the behavior of the catalyst (in terms of given NO_x storage capacity and complete reduction with the minimum amount of reductant) with various operational variables such as the lean and rich period duration and reductant concentration, at a fixed operation temperature. These maps may be helpful to know in advance and to compare thye NSR behavior of manufactured catalysts.

[1] B. Pereda-Ayo, R. López-Fonseca, J.R. González-Velasco, Appl. Catal. A: General (2009), doi: 10.1016/j.apcata.2009.04.043