In situ DRIFTS study of the NO + CO reaction on Fe-Co binary metal oxides over activated semi-coke supports

Abstract

Activated semi-coke loaded with Fe and Co species by a hydrothermal method exhibited excellent CO-deNOx performance. In this study, the reaction mechanism and the evolution of surface-adsorbed species were investigated by CO-TPR, NO-TPO, and in situ DRIFTS. The results demonstrated that in the temperature range of 100-350 °C, the adsorbed CO coordinated to Fe species, inducing an electron migration that influenced the valence state of Fe. Furthermore, the Fe3+ species were found to be the active sites for the transformation of adsorbed CO, whereas the Co3+ species provided the sites for NO evolution. In the catalytic reaction, the Fe-Co interaction could also promote the transformation of adsorbed NO and CO. The DRIFTS spectra revealed that at relatively low temperatures, the transformation of NO species occurred in the following order: NO → NO2− → NO-NO3− → N2O; at higher temperatures, the NO species evolved in the order: NO → NO2− → bidentate NO3− → chelate NO3− + N2. However, the CO transformation process was the same at both low and high temperatures: CO → COO− → CO32− → CO2. NO2− proved to be an important intermediate in the NO + CO reaction.