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.

Keywords:

• Manganese
• Nickel
• Precipitation
• Preparation
• SCR
• Surface
• Titania