The insight into the role of Al2O3 in promoting the SO2 tolerance of MnOx for low-temperature selective catalytic reduction of NOx with NH3

This research aims to enhance the SO2 tolerance of manganese oxide (MnOx) catalysts for low-temperature selective catalytic reduction (SCR) de-NOx. Based on the deactivation mechanism of MnOx, we target at the promotion of the byproduct (NH4HSO4) decomposition and the inhibition of the byproduct (MnSO4) formation. To achieve this target, thermogravimetric (TG) and temperature programmed desorption of SO2 (SO2-TPD) are performed upon as many as 21 kinds of single metal oxides to explore the potentially effective chemical composition as the additive of MnOx catalysts. The TG result indicates that Al2O3 can remarkably decrease the thermal stability of NH4HSO4. In addition, the SO2-TPD analysis reveals that the formed species after SO2 adsorption are weakly adsorbed on Al2O3. Thus, Al2O3 is selected to mix with MnOx to optimize its SO2 tolerance. Further experimental results demonstrate that the proper introduction of Al2O3 can effectively enhance the low-temperature SCR de-NOx activity and the SO2 tolerance of MnOx. It is revealed that the introduction of Al2O3 into MnOx can not only facilitate the decomposition of NH4HSO4 but also lead to reduced thermal stability of the adsorbed SO2 species to some extent. As compared to the pristine MnOx, the slight introduction of Al2O3 as the additive is beneficial to the low-temperature SCR de-NOx activity and SO2 tolerance of MnOx.