Effect of Mn addition on the low-temperature NH3-selective catalytic reduction of NOx over Fe2O3/activated coke catalysts: Experiment and mechanism

Fe2O3/activated coke (AC) and Mn-Fe2O3/AC catalysts were prepared by an impregnation method for the low-temperature selective catalytic reduction of nitrogen oxides (NOx) with ammonia (NH3). These catalysts were characterized by X-ray fluorescence, X-ray diffraction, isothermal N-2 adsorption/desorption, X-ray photoelectron spectroscopy, temperature program reduction by H-2, and temperature programmed desorption of NH3 methods. Experimental results show that Fe2O3/AC catalyst with Mn addition exhibits an excellent NOx conversion at low temperature. Nearly more than 94.7% NOx conversion of 8Mn6Fe/AC catalyst was obtained at 180-240 degrees C. The results of NH3 transient reaction and adsorption capacity of NOx indicate that 8Mn6Fe/AC catalyst has the capacity to adsorb gaseous NH3 and NOx on the catalyst surface. 6Fe/AC catalyst with a certain amount addition of Mn increases the dispersion of gamma-Fe2O3 phase, and ratios of Fe3+/(Fe2++Fe3+) and O beta/(O beta+O beta) obtained good reducibility and a lot of acid sites, which play important roles in improving the NOx conversion. The influences of SO2 and H2O on the NOx conversion over 8Mn6Fe/AC catalyst were also investigated. The good H2O poisoning resistance was obtained.