In situ IR studies of Co and Ce doped Mn/TiO2 catalyst for low-temperature selective catalytic reduction of NO with NH3

Abstract

The Mn–Co–Ce/TiO2 catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH3 in the presence of oxygen. The adsorption and co-adsorption of NH3, NO and O2 on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH3 through NH3 migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn–Co–Ce/TiO2 was proposed. At low-temperature SCR reaction, coordinated NH3 reacted with NO2−, and amide reacted with NO (ad) or NO (g) to form N2. NO2 was related to the formation of nitrite on Co-contained catalysts and the generation of NH2− on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH3 and nitrate species, resulting in N2O yield increase.