Mesoporous Mn–Ti amorphous oxides: a robust low-temperature NH3-SCR catalyst

A series of mesoporous Mn–Ti amorphous oxides (MnaTi1−a) fabricated by a combined strategy of in situ deposition and freeze-drying were studied for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperature. The physico-chemical properties of MnaTi1−a catalysts were characterized systematically by XRD, TEM, Raman, EXAFS, N2-sorption, XPS, H2-TPR and NH3-TPD. The results revealed that the increased amount of Mn4+ species greatly promoted the NO conversion at low temperature. Additionally, the highly dispersed active sites, abundant surface Lewis acid sites and strong interaction between Mn and Ti contributed to the remarkable low-temperature SCR activity. Among these MnaTi1−a catalysts, the Mn0.5Ti0.5 catalyst exhibited the best low-temperature NH3-SCR performance (61% NO conversion at 100 °C and over 95% N2 selectivity at 150–250 °C) and excellent H2O/SO2 durability. In situ FTIR was used to investigate the reaction mechanism, and the results indicated that both the L–H and E–R mechanisms were present and NH3-SCR mainly proceeded via the L–H reaction pathway at low temperature.