Promotional effect of iron oxide on the catalytic properties of Fe–MnOx/TiO2 (anatase) catalysts for the SCR reaction at low temperatures

The surface interaction of an iron-improved MnOx/TiO2 (anatase) catalyst for the selective catalytic reduction of nitric oxide was studied through detailed experiments. It was found that iron improved the catalyst by regulating the degree of polymerization and the dispersion of Mn oxide species supported on the anatase surface, which was the key factor for both the SCR activity and the N-2 selectivity. The increased NO conversion was caused by the higher Mn oxide dispersion, while selectivity evaluation showed that N2O formation on the MnOx/TiO2 catalyst was much higher than that on the iron-improved catalyst. Isotopic labelling experiments using (NH3)-N-15 with NO indicated that NH was the key species for N2O generation. NH was easily generated on MnOx/TiO2 without iron, which had a higher oxidability than the iron-improved catalyst, as identified by H-2 temperature-programmed reduction experiments.