Mn/CeO2 catalysts for SCR of NOx with NH3: comparative study on the effect of supports on low-temperature catalytic activity

Two Mn/CeO2 catalysts were successfully prepared by the impregnation of Mn precursor on two supports, CeO2 microspheres (CeO2-MSS) and CeO2 microrods (CeO2-MRs), respectively. The obtained Mn/CeO2-MSs and Mn/CeO2-MRs catalysts were characterized by SEM, TEM, XRD, N-2 physical adsorption, Raman spectroscopy, XPS, H-2-TPR, NH3-TPD and in situ DRIFT in detail, and their catalytic activities and N-2 selectivities were studied by selective catalytic reduction (SCR) of NOx with NH3. The results showed that the Mn/CeO2-MSs catalyst presented much superior catalytic activity to the counterpart Mn/CeO2-MRs catalyst, and an almost 100% NOx conversion was maintained at 150-240 degrees C under a high space velocity of 36,000h(-1). The high catalytic performance of Mn/CeO2-MSs can be attributed to a series of better properties in comparison with Mn/CeO2-MRs, such as unique yollavoid@shell microsphere structure, much larger specific surface area, higher relative percentages of Mn4+/Mnn+ and Ce3+/(Ce3+Ce4+): more easily reduced of Mn species, more Bronsted acid sites. Furthermore, Mn/CeO2-MSs catalyst presented excellent resistance to H2O deactivation and SO2 poison, and the SCR reaction mechanism over Mn/CeO2-MSs followed both E-R and L-H mechanisms. (C) 2017 Elsevier B.V. All rights reserved.