Composite catalytic systems: A strategy for developing the low temperature NH3-SCR catalysts with satisfactory SO2 and H2O tolerance

Mn-based catalysts were believed to be promoting low temperature NH3-SCR catalysts for their satisfactory catalytic activity, whereas their poor SO2 and H2O tolerance inhibited their applications. In this work, utilizing poor SO2 tolerance of Mn oxides, composite catalytic systems containing Mn oxides as deSO(x) catalyst was designed and synthesized, which exhibited excellent low temperature NH3-SCR performance in the presence of SO2 and H2O. The deSOx mechanism of Mn oxides was systematically investigated. In results, SO2 was catalytic oxidized on the surface of Mn oxides. Oxidized sulfur species could flow away from Mn oxides surface through feed gas flow or form MnSO4. When NH3 and H2O were introduced into the feed gas, the oxidized sulfur species were completely deposited as NH4HSO4 instead of forming MnSO4. Thus, SO2 was removed from feed gas entirely resulting in the superb low temperature NH3-SCR performances. This work provided a general strategy to enhance SO2 and H2O tolerance of NH3-SCR catalysts at low temperature by removing SO2 using NH3 and H2O who existed in the exhaust gas from stationary sources.