NO conversion in presence of O2, H2O and SO2: Improvement of a Pt/Al2O3 catalyst by Zr and Sn, and influence of the reducer C3H6 or C3H8

The aim of this work was to improve the SCR activity of a Pt/Al2O3 model catalyst by ZrO2 (20 wt%) and/or SnO2 (2 wt%) addition. The activity of the catalysts was measured in lean mixture containing C3H6 or C3H8, O2, H2O, CO2 and SO2 (0–700 ppm).With propene, ZrO2 and SnO2 addition improve the optimal NOx conversion (near 250 °C) and decrease the corresponding N2O selectivity, especially with SO2 in the feed stream (sulfated catalysts). For higher temperatures, the NOx conversion decrease is associated with the formation of nitric acid at the reactor outlet (25% nitrate selectivity at 300 °C). With propane, the NOx conversion is only attributable to the formation of nitric acid, no significant reduction was observed.