Physicochemical Properties and NH3-SCR Performance of Supported CeO2-MnOx Mixed Oxides Catalysts

CeO2-MnOx mixed oxides supported on different carriers (ZSM-5, TiO2, and SAPO-34) were prepared by the sol-gel combustion method and evaluated for the selective catalytic reduction of NO with NH3. The physicochemical properties of the samples were determined by using XRD, TEM, N-2 adsorption (BET method), H-2-TPR, and NH3-TPD. The Ce-Mn/TiO2 exhibited a higher NO conversion than Ce-Mn/ZSM-5 in the 100-200 degrees C temperature range, but the NO conversion of Ce-Mn/ZSM-5 increases with reaction temperature (being the N-2 selectivity close to 100%) whereas, for Ce-Mn/TiO2, the N-2 selectivity extremely decreases. The reducibility and surface acidity of samples seems to explain the catalytic performance. Thus, although the reducibility of Ce-Mn/ZSM-5 and Ce-Mn/TiO2 was similar, the large number of surface acid sites of Ce-Mn/ZSM-5 could be a plausible reason for its excellent SCR activity. In fact, the superior SCR activity of Ce-Mn/ZSM-5 (94% NO conversion and 95% N-2 selectivity at 300 degrees C) is related to the presence of well-dispersed Ce-Mn mixed oxide nanoparticles, high reducibility, and a large number of surface acid sites.