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

MnOx-CeO2 mixed oxide supported on g-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), H-2 temperature-programmed reduction (H-2-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 O-2, resulting in less deactivation of the wet sulfated catalyst.