Comparison of Mn doped CeO2 with different exposed facets for NH3-SCR at low temperature

Abstract

Herein, the Mn-doped different exposed crystal surfaces of CeO2 were prepared and used for the low-temperature NH3-SCR process. The results showed that Mn/CeO2-NC catalyst possessed the higher catalytic activity than Mn/CeO2-NP and Mn/CeO2-NR catalysts at low temperature, which achieved over 90% NO conversion at 200 °C. XRD and SEM analysis verified that though the grain size was different, the active manganese species still maintained the highly uniform distribution on all catalysts. The excellent low-temperature redox property and strong surface acidity jointly served as the inherent motivations for the superior catalytic performance of Mn/CeO2-NC catalyst. During the transient reaction process, no obvious derivatives transformation behavior was observed on CeO2-NP-based catalyst, while both E-R and L-H reaction mechanisms occurred on both Mn/CeO2-NC and Mn/CeO2-NR catalysts. And the Mn/CeO2-NC catalyst had the greater transient reaction efficiency than Mn/CeO2-NR catalyst at whichever pathways, which might clarify the difference in catalytic activity between Mn/CeO2-NC and Mn/CeO2-NR catalysts. Finally, the possible reaction mechanism model for low-temperature SCR over Mn-modified different exposed crystal surfaces of CeO2 catalysts was proposed.