Effect of water vapor on sulfur poisoning of MnOx–CeO2/Al2O3 catalyst for diesel soot oxidation

Abstract

MnO_x–CeO₂ mixed oxide supported on γ-Al₂O₃ was sulfated in dry and wet atmospheres to explore the effect of water during sulfur poisoning. The fresh and poisoned catalysts were characterized by Brunauer–Emmett–Teller (BET), thermo-gravimetric analysis (TGA), NH₃ temperature-programmed desorption (NH₃-TPD), infrared spectroscopy (IR), H₂ temperature-programmed reduction (H₂-TPR), NO temperature-programmed oxidation (NO-TPO) and soot temperature-programmed oxidation (soot-TPO). The results show that water hinders sulfate deposition on the catalyst. The wet sulfated catalyst with abundant surface hydroxyl groups has higher surface acidity than the dry sulfated one. Although the presence of water does not prevent the deprivation of redox properties, the generated surface acid sites may promote the NO₂ utilization efficiency and deep oxidation of soot by O₂, resulting in less deactivation of the wet sulfated catalyst.