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

The MO (M = Cu, Mn, Co)/CePO support was firstly prepared via the hydrothermal and impregnated method. Selective catalytic reduction of NO with NH (NH-SCR) results showed that the MnO modifications greatly improved the SCR activities at low temperatures. The NOx conversion of the MnO/CePO 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 NH 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 O-TPD and NO oxidation tests. The process of NO oxidation to NO plays a key role to produce the absorbed monodentate nitrate as indicated by the In-situ DRIFTS. The support CePO acts as the acid sites to form highly active NH species. The synergic effect between the MnO and CePO contributed to the high SCR activity over the MnO/CePO catalyst. Additionally, the MOx/CePO catalyst exhibits an excellent water tolerance and N selectivity. Consequently, the MnO/CePO catalyst becomes the potential catalyst for the practical process.