Effect of Sulfur on Mn/Ti Catalysts Prepared Using Chemical Vapor Condensation (CVC) for Low-Temperature NO Reduction

Mn/Ti catalysts prepared through impregnation of manganese acetate and a manganese nitrate precursor via the chemical vapor condensation (CVC) method were investigated in this study to assess NH3-selective catalytic reduction (SCR) activity. Manganese (Mn) loaded on a synthesized TiO2 catalyst showed good low-temperature NO reduction activity and better resistance to sulfur poisoning in presence of SO2. Mn loaded on synthesized TiO2 prepared from manganese acetate precursor especially exhibited a high NO conversion of 98.4% at 150 °C. Moreover, it presented high NO conversions within the entire operating temperature window in comparison with other catalysts, which may be attributed to smaller particle size, scattered amorphous Mn over the catalyst surface, higher dispersion, and an abundant Mn2O3 phase. X-ray photoelectron spectroscopy (XPS) analysis of the spent catalyst following the SCR reaction in presence of SO2 verified that the formation of sulfated titanium and manganese sulfate was significantly inhibited, and that the deposition concentration of ammonium sulfate on active sites was low owing to impregnation of Mn acetate onto synthesized TiO2. FT-IR analysis indicated that the catalyst also contained larger quantities of N–H bonds in NH3, synchronizing with Lewis acid sites on its surface.