Sulphur Dioxide Deactivation of NOx Storage Catalysts

摘要

The influence of sulphur dioxide on the NOx storage performance of a Pt-Rh/BaO/Al_2O_3 model catalyst has been investigated. Addition of 2.5-25 vol.-ppm SO_2 to a synthetic lean-burn exhaust, comtaining NO, C_3H_6, O_2 and Ar, caused deactivation of the NOx storage function of the catalyst. The rate of deactivation was found to be proportional to the exposure of SO_2. This effect is sdeen for temperatures between 250 and 450degC. Together with in situ FTIR measurements, this leads to the conclusion that sulphur accumulates in the NOx storage component of the catalyst during the exposure. Furthermore, SO_2 also inhibits the oxidation capacity of the catalyst during lean periods as is observed by a decreased NO oxidation activity. The presence of SO_2 also reduces the reduction capacity of the catalyst under rich periods, which leads to an increased N_2O formation and a decreased NO conversion.