MnOx-pillared rectorite prepared by in situ deposition as efficient catalysts for low-temperature NH3-SCR: The influences of manganese (II) precursors

Abstract

MnOx pillared rectorite (REC) catalysts (10 wt% based upon Mn element and the mass of clay) were prepared by in situ deposition using different manganese (II) precursors, e.g., Mn(NO3)2, Mn(Ac)2, MnSO4 and MnCl2 to react with KMnO4, respectively. Unsupported MnOx was also prepared through reaction between Mn(Ac)2 and KMnO4 solution. The samples were characterized by XRD, SEM, low-temperature N2 adsorption, HRTEM, H2-TPR, NH3-TPD, TPSR and XPS. And the deNOx performances for low-temperature NH3-SCR were evaluated. The results showed that the unsupported amorphous MnOx had much higher deNOx performance than different MnO2 phases. For the MnOx pillared REC catalysts, deNOx performances decreased in the order of Mn10/REC-Ac- > Mn10/REC-Cl- > Mn10/REC-SO42- > Mn10/REC-NO3-. The Mn10/REC-AC- MnOx-Ac-/REC showed the best redox properties, richest weak acid sites and best dispersion of MnOx and content of Mn4+, which contributed to its high activity. Moreover, even under working conditions with GHSV up to 105,000 h−1, high deNOx performance and good stability was also observed for Mn10/REC-Ac- catalyst.