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

MnOx-CeO2catalysts were synthesized to investigate the active sites for NO oxidation by varying the calcination temperature. XRD and TEM results showed that cubic CeO2and amorphous MnOxexisted in MnOx-CeO2catalysts. High temperature calcination caused the sintering of amorphous MnOxand transforming to bulk crystalline Mn2O3, H2-TPR and XPS results suggested the valence of Mn in MnOx-CeO2was higher than pure MnOx, and decreased with the increasing calcination temperature, The turnover frequency(TOF) was calculated based on the initial reducibility according to H2-TPR quantitation and kinetic study. The TOF results indicated that the initial reducibility of amorphous MnOxwith high valence manganese ions was equivalent to the active sites for NO oxidation. It can be inferred that the amorphous MnOxplays a key role in low-temperature NO oxidation.