A comparative study of MOx (M = Mn, Co and Cu) modifications over CePO4 catalysts for selective catalytic reduction of NO with NH3.

Abstract

The MOx (M = Cu, Mn, Co)/CePO4 support was firstly prepared via the hydrothermal and impregnated method. Selective catalytic reduction of NO with NH3 (NH3-SCR) results showed that the MnOx modifications greatly improved the SCR activities at low temperatures. The NOx conversion of the MnOx/CePO4 catalyst was above 80% even at 180 °C. In-situ DRIFTS results suggest that the SCR reaction is majorly conducted between the absorbed monodentate nitrate and NH3 species (i.e., the Langmuir-Hinshelwood mechanism). MOx (M = Cu, Mn, Co) exists in the formation of nano-size particles obtained by SEM and TEM directly. These nano-size particles can provide active surface adsorbed oxygen and thus improve the NO oxidation ability as indicated by the O2-TPD and NO oxidation tests. The process of NO oxidation to NO2 plays a key role to produce the absorbed monodentate nitrate as indicated by the In-situ DRIFTS. The support CePO4 acts as the acid sites to form highly active NH4+ species. The synergic effect between the MnOx and CePO4 contributed to the high SCR activity over the MnOx/CePO4 catalyst. Additionally, the MOx/CePO4 catalyst exhibits an excellent water tolerance and N2 selectivity. Consequently, the MnOx/CePO4 catalyst becomes the potential catalyst for the practical process.