The efficiency and product formation as a function of temperature, time and gas stoichiometry, in the regeneration of an SO_2 poisoned NOx storage and reduction (NSR) catalyst has been studied. using these results a simple model for suphur posioning and regeneration of this type of catalyst is proposed. SO_2 poisons the catalyst, which results ina decrease of the NOx conversion with increasing SO_2 exposure time. The NOx storage capacity ca be regained after regeneration of the catalysts. The regeneration is most effective using long regeneration time, high temperautre and low lambda value. A measure of the regeneration efficiency, activity based sulpuhur removal (ASR), is defined, ASR is used to model the regeneration efficiency with the independent variables; regenration time, temperature and lambaa value. The model describes the experiemntal results well. The amounts of released SO_2, H_2S and COS, during the regeneration differ depending on regeneration conditions. Low lambda values. The production of COS is low in all cases. The results can schematically be sescribed with a model there sulphur can migrate between deactivating and non-deactivating positions on the catalyst surface.
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