Significantly enhanced low-temperature activity and SO2/H2O tolerance of Mn–Ce-Ox/TiO2 catalyst prepared by a facile citric acid assisted impregnation method

Abstract

Two different Mn–Ce-Ox/TiO2 catalysts were prepared by ordinary impregnation (denoted as MCT) and citric acid assisted impregnation (denoted as MCT-CA) methods, respectively. Excellent NOx removal is achieved over MCT-CA for selective catalytic reduction with NH3 (NH3-SCR), and 100% NOx conversion is obtained at 125 °C under weight hour space velocity (WHSV) of 80000 mL/(gcat·h). Particularly, 100% NOx is converted on MCT-CA in the presence of 10 vol% H2O at 175 °C. As H2O and SO2 coexist in the reaction system for 9 h, NOx conversion can still be maintained >90%, much higher than that (22%) of MCT. A series of characterization results indicates that MCT-CA exhibits a larger BET specific surface area, pore volume, and pore size, which enhances the dispersion of Mn and Ce oxides and promotes the rapid adsorption of reactants and desorption of products. Additionally, MCT-CA possesses more Mn4+, Ce3+, chemisorbed oxygen species, and stronger reducibility, facilitating the conversion of NO to NO2. Specially, the amount of active NH3 species and active nitrate species on MCT-CA is much more than that over MCT. The combined effect of the aforementioned factors devotes to the excellent low-temperature SCR performance and tolerance to H2O/SO2 over MCT-CA.