Effect of Promoters on the Catalytic Performance and SO2/H2O Resistance of α-MnO2 Catalysts for Low Temperature NH3-SCR

Abstract

A series of α-MnO2 catalysts doped with Fe, Ce, Cr, Zr, or Co as metal promoters were synthesized via a hydrothermal method. The effects of these metal promoters on the physicochemical properties and deNOX activity of the α-MnO2 catalysts were systematically investigated, among which α-MnO2 catalyst doped with Co behaved with the best selective catalytic reduction (NH3-SCR) activity at low temperatures. The α-MnO2 catalyst with Mn/(Mn + Co) = 0.8 (molar ratio) displayed an outstanding NH3-SCR activity with 100% NO conversion between 140 and 280 °C, excellent N2 selectivity and stability which may be due to plenty of acid sites, a strong adsorption capacity for NH3/NO at 100–300 °C, and abundant Mn4+, Co3+, and surface adsorbed oxygen species. Further, the catalyst exhibited excellent H2O/SO2 resistance and the NO conversion activity remained 100% after adding 5% H2O, 200 ppm of SO2, or 5% H2O + 100 ppm of SO2 at 200 °C.