Low-temperature selective catalytic reduction of NO with NH3 over Mn–Ce–Ox/TiO2: a comparison between catalyst preparation methods

Three Mn–Ce–Ox/TiO2 mixed oxides (MCT) were prepared by sol–gel (SG), citric acid complexing (CA), and co-precipitation (CP) methods and used as catalysts for selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures (75–200 °C). The physicochemical properties of the prepared catalysts were investigated by N2 adsorption, X-ray diffraction (XRD), temperature-programmed reduction by H2 (H2-TPR), adsorption of NH3 and NO followed by temperature-programmed desorption (NH3/NO-TPD), X-ray photoelectron spectroscopy (XPS), and in situ diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy. The results show that both the low-temperature de-NOx activity and the resistance to SO2 poisoning of the Mn–Ce–Ox/TiO2 catalyst decrease in the order of MCT-CP > MCT-SG > MCT-CA. These disparities can be mainly attributed to the difference in specific surface area, fractions of Mn4+ (Mn4+/(Mn2++Mn3++Mn4+)) and surface adsorbed oxygen (surface adsorbed oxygen/(surface adsorbed oxygen + lattice oxygen)) species, and the adsorption capacity for NH3 and NO of the different catalysts.