The sulfation and combination of MnO<sub><italic>x</italic></sub> and Fe<sub>2</sub>O<sub>3</sub> catalysts forNH<sub>3</sub>-SCR denitration reaction

Abstract

Firstly, the metal oxide catalysts of MnO x and Fe2O3 were prepared by precipitation method. Thereafter, SO42−/ MnO x and SO42−/Fe2O3 were prepared by acidification with sulfuric acid in the synthesis step. After investigating their activities for selective catalytic reduction of NO x with NH3 (NH3-SCR) in turn, it was found that the denitrification of the sulfating SO42−/MnO x and SO42−/Fe2O3 were greatly improved. The characterization results showed that the introduction of SO42− suppressed the redox activity of MnO x and restrained ammonia oxidative reaction in high temperature; SO42− and Fe2O3 can form solid super acid to greatly improve the acidity of Fe2O3 and in favor of adsorbing and stabilizing alkaline reducing agent. Finally, the denitrification properties of MnO x and Fe2O3 were developed. In this paper, the modified SO42−/MnO x and SO42−/Fe2O3 were combined to form three combined catalysts. After combination, the two catalysts produced a good synergistic effect, exhibited respective advantages at both low temperatures and high temperatures, and displayed wider high activity-temperature window (200–450 °C; NO conversion >90%), lower yield of the by-product and higher nitrogen selectivity. It was also realized that the combining way, which put the high temperature activity SO42−/Fe2O3 in the first half unit and put the low temperature activity SO42−/MnO x in the second half unit could achieve the best denitrification effect with higher N2 yield (>80%, 100–450 °C) . It is effective to optimize the nitrogen selectivity of the manganese-based catalyst and the board activity-temperature window of the iron-based catalyst.