Enhancing the deNOx performance of MnOx/CeO2-ZrO2 nanorod catalyst for low-temperature NH3-SCR by TiO2 modification

Abstract

In the present work, we chose MnOx/CeO2-ZrO2 nanorod (i.e., Mn/CZ-NR) as a benchmark catalyst, and used TiO2 as a modifier with the purpose of inhibiting the formation of N2O (by-product) as well as further enhancing the catalytic activity and H2O + SO2 tolerance of Mn/CZ-NR catalyst. These samples were characterized by TEM, HRTEM, XRD, Raman, H2-TPR, XPS, NH3-TPD, and in situ DRIFTS. DeNOx performance and H2O + SO2 tolerance of these samples were evaluated by low-temperature NH3-SCR reaction. The obtained results show that the TiO2 modified catalyst (i.e., Mn-Ti/CZ-NR) exhibits higher catalytic activity than Mn/CZ-NR catalyst due to larger amount of oxygen vacancy accompanied with more Ce3+, higher ratios of Mn4+ and surface adsorbed oxygen species, as well as the improvement of surface acidity. Furthermore, TiO2 modification effectively inhibits the non-selective oxidation of NH3 to N2O through appropriately weakening the redox property of Mn/CZ-NR catalyst, which is beneficial to the enhancement of N2 selectivity. Finally, Mn-Ti/CZ-NR catalyst exhibits excellent H2O + SO2 tolerance, which indicates that it has the potential to be used for practical low-temperature deNOx application.