Insight into the enhanced catalytic activity and H2O/SO2 resistance of MnFeOx/Defect-Engineered TiO2 for low-temperature selective catalytic reduction of NO with NH3

Abstract

A series of Mn-Fe mixed oxide (MnFeOx) supported on high-surface-area TiO2 (Tiov) containing engineered Ti3+/oxygen vacancies was demonstrated for NH3-SCR of NO. The best catalyst MnFe/Tiov(0.05)-1 exhibited excellent NH3-SCR activity (>99 % conversion) over 60–260 °C and superior resistance to high H2O content (20 vol%), with NO conversion exceeding 90 % at temperatures lower than 150 °C. Furthermore, MnFe/Tiov(0.05)-1 exhibited outstanding durability over 70 h of sustained operation in the co-presence of H2O and SO2, whereas catalytic deactivation was observed for the conventional TiO2-supported catalyst (MnFe/Ti). The combined results of various characterization techniques confirmed that the interactions between the MnFeOx and Tiov supports were strengthened. The defect-rich surface of the Tiov support promoted the dispersion of MnFeOx and facilitated the redox cycle Mn4+ + Ti3+ ↔ Mn3+ + Ti4+, thus facilitating the adsorption and activation of NH3 and NO molecules. Moreover, the in situ diffuse reflectance infrared Fourier transform results indicated that H2O strongly suppressed the adsorption/activation of NH3 and NOx and the reactions between NH3 and NOx through the Langmuir–Hinshelwood pathway on MnFe/Ti, while such adverse effects were significantly reduced when using MnFe/Tiov(0.05)-1, in which the Eley–Rideal mechanism was dominant.