Comparison of low-temperature catalytic activity and H2O/SO2 resistance of the Ce-Mn/TiO2 NH3-SCR catalysts prepared by the reverse co-precipitation, co-precipitation and impregnation method

Ce-Mn/TiO2 mixed oxides catalysts were prepared by reverse co-precipitation (RC), conventional co-precipitation (C) and impregnation (I) methods for low-temperature selective catalytic reduction of NOx by NH3. The effect of the calcination temperature, aging time and space velocity on the de-NOx activities of the 4Ce-10Mn/TiO2-RC was investigated. The 4Ce-10Mn/TiO2-RC catalyst exhibited a more excellent low-temperature activity and a higher SO2 resistance than those prepared by the co-precipitation and impregnation methods. The NO conversion over 90% of in the temperature of 120 ∼ 330 °C was achieved, which only decreased from 99% to 85% after adding 5% H2O at 180 °C for 1 h. The excellent performance of the 4Ce-10Mn/TiO2-RC may be owing to its low crystallinity, high specific surface area, uniform dispersion of active sites, high content of Mn4+, Ce3+ and adsorbed oxygen species, acid sites on the surface. The XPS results showed electron transfer may exist between the manganese oxide and cerium oxide: Mn3+ + Ce4+→Mn4+ + Ce3+. Moreover, the in situ DRIFTS revealed the NH3-SCR reactions over 4Ce-10Mn/TiO2-RC and 4Ce-10Mn/TiO2-I catalysts were mainly controlled by the Eley-Rideal mechanism.