Active manganese oxide on MnOx-CeO2 catalysts for low-temperature NO oxidation: Characterization and kinetics study

MnOx-CeO2 catalysts were synthesized to investigate the active sites for NO oxidation by varying the calcination temperature. XRD and TEM results showed that cubic CeO2 and amorphous MnOx existed in MnOx-CeO2 catalysts. High temperature calcination caused the sintering of amorphous MnOx and transforming to bulk crystalline Mn2O3. H-2-TPR and XPS results suggested the valence of Mn in MnOx-CeO2 was higher than pure MnOx, and decreased with the increasing calcination temperature. The turnover frequency (TOF) was calculated based on the initial reducibility according to H-2-TPR quantitation and kinetic study. The TOF results indicated that the initial reducibility of amorphous MnOx with high valence manganese ions was equivalent to the active sites for NO oxidation. It can be inferred that the amorphous MnOx plays a key role in low-temperature NO oxidation. (C) 2018 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.