Insight into the activity and SO2 tolerance of hierarchically ordered MnFe1-δCoδOx ternary oxides for low-temperature selective catalytic reduction of NOx with NH3

Manganese (Mn)-based mixed oxides are considered the most efficient catalysts for low-temperature ammonia selective catalytic reduction of nitrogen oxides (NO x ) (NH 3 -SCR of NO x ). Water resistance and sulfur tolerance, especially the SO 2 tolerance of Mn-based catalysts, are the main obstacles preventing their practical application. Therefore, in this study, a series of cobalt (Co)-doped MnFeO x ternary mixed oxides catalysts with a hierarchically ordered structure (Hierc-MnFe 1-δ Co δ O x , δ = 0.2, 0.4 and 0.6) were developed and applied for NH 3 -SCR of NO x at low temperature. Compared with Hierc-MnFeO x , Hierc-MnFe 1-δ Co δ O x catalyst exhibited enhanced low-temperature activity and a broadened temperature window (NO x conversion above 80% was between 90 and 343 °C over Hierc-MnFe 0.6 Co 0.4 O x ), as well as better H 2 O resistance and SO 2 tolerance. The enhanced low-temperature activity was attributed to a larger amount of active oxygen species, a higher proportion of Mn 4+ , Fe 3+ and Co 3+ content, and the improvement of surface acidity, which can facilitate the adsorption and activation of NO and NH 3 . Additionally, the Hierc-MnFe 0.6 Co 0.4 O x catalyst exhibited superior soot tolerance due to its special hierarchically ordered architecture. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the Co-modified Hierc-MnFe 1-δ Co δ O x ternary oxide catalyst could efficiently protect nitrate species on Hierc-MnFe 0.6 Co 0.4 O x from the poisoning effect of SO 2 , thereby boosting its SO 2 tolerance. This study provides a good candidate for low-temperature de NO x application with enhanced SO 2 and soot tolerance.