Low-Temperature NH3-SCR on Cex-Mn-Tiy Mixed Oxide Catalysts: Improved Performance by the Mutual Effect between Ce and Ti

A series of Ce-x-Mn-Ti-y catalysts were synthesized using the coprecipitation method, and sodium carbonate solution was used as a precipitant. The various catalysts were assessed by selective catalytic reduction of NOx with NH3, and characterized by X-ray diffraction, Raman spectroscopy, H-2 temperature-programmed reduction, NH3 temperature-programmed desorption, and X-ray photoelectron spectroscopy to investigate the physicochemical properties, surface acidity, and redox abilities of the Ce-x-Mn-Ti-y catalysts. The Ce-0.1-Mn-Ti-0.1 catalyst exhibited the best catalytic performance (more than 90% NOx conversion in the range of 75 to 225 degrees C), as a result of proper redox ability, abundant acid sites, high content of Mn4+ and Ce3+, and surface-adsorbed oxygen (O-S). The results of in situ DRIFT spectroscopy showed that the NH3-SCR reaction followed both the E-R and L-H paths over the Ce-0.1-Mn-Ti-0.1 catalyst, and it occurred faster and more sharply when it mainly abided by the E-R mechanism.