The inhibition effect of oxygen in the calcination atmosphere on the catalytic performance of MnOx–CeO2 catalysts for NO oxidation

Abstract

In this study, the widely studied MnCe (MnOx–CeO2) catalyst prepared by the co-precipitation method was used for investigating the effects of oxygen in the calcination atmosphere (referred as Oca) on its catalytic performance for NO oxidation. The evaluation of catalytic performance showed that MnCe-O (calcined in O2/Ar) exhibited a much lower NO conversion in comparison with MnCe-A (calcined in Ar) catalyst. The characterization results revealed that Oca could cause the sintering of MnCe catalysts and then reduce the surface area, which decreased the active sites for catalytic reaction. Simultaneously, Oca inhibited the incorporation of Mn ions into CeO2 lattice, which could weaken the interaction between MnOx and CeO2 supports. This weak interaction decreased the amounts of active oxygen species and weakened the redox properties of MnCe catalyst. Furthermore, the nitrate species adsorbed on MnCe-O was more stable than that on MnCe-A. Therefore, the inferior catalytic performance of MnCe-O could be attributed to the collective effect of low concentration active sites and active oxygen species, poor redox properties and stable adsorbed nitrate species.