Enhancement of NO and C3H6 oxidation by SO2 treatment over Pt/Al2O3

Conference poster, 2013

Oxidation catalyst is used in automotive exhaust treatment to convert CO and hydrocarbons into CO2 and water. They also have the specific function of converting NO into NO2 in Diesel vehicles, which increases the efficiency of NOx-removal system and participates in the particle filter regeneration. Automotive catalysts are affected by thermal treatments and gas composition. SO2 is one of the undesirable compounds of exhaust gases that is able to store on the catalyst [1] and hinder the reaction. Despite its low concentration, SO2 affects significantly the catalyst. Ageing in SO2-containing atmosphere has shown to promote platinum migration and increase the ability of Pt/Al2O3 catalysts to oxidize NO in dry conditions [2]. In the present work, model catalysts were aged in presence of SO2 at 250 °C and tested for NO and C3H6 oxidation in wet conditions. Various reductive treatments were performed after ageing in order to shed a light on the stability and impact on activity of the different types of adsorbed sulfur species. The hysteresis phenomenon observed for both reactions was also affected by the presence of surface sulfur. The performance of a typical oxidation catalyst was improved by pretreatment in presence of SO2 and subsequent elimination of the less stable stored sulfur species. Further activity was gained during the cooling for both NO and C3H6 oxidation after complete removal of sulfur.