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

Abstract

The surface interaction of an iron-improved MnO_x/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 N₂ selectivity. The increased NO conversion was caused by the higher Mn oxide dispersion, while selectivity evaluation showed that N₂O formation on the MnO_x/TiO₂ catalyst was much higher than that on the iron-improved catalyst. Isotopic labelling experiments using ¹⁵NH₃ with NO indicated that NH was the key species for N₂O generation. NH was easily generated on MnO_x/TiO₂ without iron, which had a higher oxidability than the iron-improved catalyst, as identified by H₂ temperature-programmed reduction experiments.