Effect of Nickel as Dopant in Mn/TiO2 Catalysts for the Low-Temperature Selective Reduction of NO with NH3

Abstract

Nickel doped manganese oxide supported on titania materials were investigated for the low-temperature NH3-SCR. For this purpose, a series of Ni modified Mn/TiO2 catalysts were prepared and evaluated for the low-temperature SCR of NO with ammonia in the presence of excess oxygen. The catalytic performance of these materials was compared with respect to the nickel weight percentage in order to examine the correlation between physicochemical characteristics and reactivity of optimized materials. It was found that the 5% Mn–2% Ni/TiO2 catalyst showed the highest activity and yielded 100% NO conversion at 200 °C. XRD results reveal highly dispersed manganese–nickel species on TiO2 support for the Mn–Ni/TiO2 catalysts. Our TPR data results suggested an increase in reducibility of manganese species in Mn–Ni/TiO2 catalysts. The absence of the high-temperature (736 K) peak indicates that the dominant phase is MnO2. This increase of reducibility and dominant MnO2 phase seems to be the reason for the enhanced activity and time on stream patterns of nickel-promoted titania-supported manganese catalysts. BET results illustrate that the high NO conversion is strongly dependant on the specific surface area and pore volume of this catalyst. All the physicochemical techniques we used suggested that the composition of manganese and nickel oxides on the support surface is playing an important role for the enhancement of NO conversion and the prominent time on stream stability.