Enhanced low-temperature NO oxidation by iron-modified MnO2 catalysts

Series of Fe-modified MnO2 catalysts were prepared to improve low-temperature NO oxidation. Introduction of Fe3+ resulted in a phase transformation from alpha-MnO2 to epsilon-MnO2. Hexagonal Fe0.32MnO2 exhibited the highest activity with the lowest T-50 of 156 degrees C and the maximum NO conversion of 80% at 250 degrees C. It also possessed the best reducibility and abundant readily available oxygen species, which facilitated the oxidation of NO. Major differences in the NO oxidation reaction route between alpha-MnO2 and Fe0.32MnO2 were the adsorption sites and the type of intermediates. The synergetic effect between Fe and Mn enhanced the activation of NO and O-2.