The Effect of Precipitants on MnOx-Ni/TiO2 SCR Catalysts Prepared by Titanium Slag as Raw Material

Abstract

Mn-Ni/TiO2 catalysts were prepared using a joint precipitation method with acid-dissolved titanium slag as raw material for selective catalytic reduction of nitrogen oxide. The joint precipitation method was accomplished with different precipitants, such as sodium hydroxide, carbamide, ammonia, or hydrogen peroxide. The deNOx activities of the catalysts prepared by different precipitants were investigated with SCR activity reactor within temperatures of 90–350°C. It is evident that the Mn-Ni/TiO2 catalyst with carbamide-ammonia-hydrogen peroxide as precipitant has superior catalytic activity, which the NO conversion can reach 90% at 120°C, with a wider temperature window (120–300°C) for the NH3-SCR reaction. H2-TPR results showed that the reduction potential of MnOx species on Mn-Ni/TiO2 catalysts is increased compared to that of Mn/TiO2 catalysts. Oxygen mobility is enhanced by interaction between Ni and Mn atoms due to use of carbamide-ammonia peroxide as precipitant. XPS results suggest that the presence of MnO2 is the major phase in nickel-doped Mn/TiO2 catalysts. Our NH3-TPD results illustrated that the catalysts have a lot of acid-active sites, which lead to attracting more ammonia to participate in the catalytic reaction.