Investigation of RuOx doping stimulated the high catalytic activity of CeOx-MnOx/TiO2 catalysts in the NH3-SCR reaction: Structure-activity relationship and reaction mechanism

Abstract

CeO x -MnO x /TiO 2 (CMT) is the prototype, low-temperature (150–250 ℃) mixed oxide NH 3 -deNO x catalyst with the greatest potential for industrial application. The improvement of ultra-low temperature (60–150 ℃) denitration activity, SO 2 and alkali resistance of CMT catalysts received significant attention. RuO x has been widely utilized in selective catalytic oxidation (SCO), and we believe that the catalyst must first undergo SCO before selective catalytic reduction (SCR). Therefore, a series of RuO x -CMT catalysts were prepared by impregnating RuO x with CMT as the carrier and their catalytic mechanism at low temperature and activity analyzed in detail through XRF, XRD, BET, TEM, HRTEM, STEM+EDS, XPS, H 2 -TPR, NH 3 -TPD-MS and in situ DRIFTS characterizations. The obtained results show that RuO x modification significantly improved the low-temperature denitrification activity of CMT by enhancing the interaction of Ce, Mn and Ti, promoting the conversion of inactive bidentate nitrate to the active monodentate nitrate and strengthening the Mars-van Krevelen (M-K), Langmuir-Hinshelwood (L-H), and Eley-Rideal (E-R) mechanisms. • RuO x doping stimulates the high NH 3 -SCR activity of CeO x -MnO x /TiO 2 catalysts. • RuO x modification significantly promotes the dispersion of Ce, Mn, and Ti elements. • Addition of RuO x strengthens the M-K, L-H and E-R mechanisms at low temperature. • RuO x converts inactive bidentate nitrate into active monodentate nitrate. • Monodentate nitrate is the main NO activation species reacting with NH x species.