Low-temperature NH3-SCR of NOx over MnCeOx/TiO2 catalyst:Enhanced activity and SO2 tolerance by modifying TiO2 with Al2O3

A series of TiO-AlOcomposites with Al/Ti molar ratios of 0.1,0.2,and 0.4 were synthesized by a coprecipitation method and used as supports to prepare supported MnCeOcatalysts by an impregnation method.The physico-chemical properties of the samples were extensively characterized by N2 physisorption,X-ray diffraction,Raman spectroscopy,scanning electron micro scopy and energy-dispersive Xray spectroscopy element mapping,X-ray photoelectron spectroscopy,H-temperature programmed reduction,ammonia temperature programmed desorption,and in-situ diffuse reflectance infrared Fourier transform spectroscopy.The catalytic activity and resistance to water vapor and SOof the asprepared catalysts for the SCR of NOwith NH3 were evaluated at 50-250℃ and GHSV of 80000 mL/(g·h).The results reveal that MnCeO/TiO-AlOexhibits higher activity and better SO2 tolerance than MnCeO/TiO.Combining with the characterization results,the enhanced activity and SO2 tolerance of MnCeO/TiO-AlOcan be mainly attributed to higher relative concentrations of Mnand chemisorbed oxygen species,stronger reducibility,and larger adsorption capacity for NH3 and NO,which originate from the larger specific surface area and pore volume,higher dispersion of Mn and Ce species compared with MnCeO/TiO.Moreover,in situ DRIFTS was used to investigate the reaction mechanism,and the results indicate that the NH3-SCR reaction over MnCeO/TiOand MnCeO/TiO-AlOtakes place by both the E-R and L-H mechanisms.