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

Abstract

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, N2 adsorption (BET method), H2-TPR, and NH3-TPD. The Ce–Mn/TiO2 exhibited a higher NO conversion than Ce–Mn/ZSM-5 in the 100-200°C temperature range, but the NO conversion of Ce–Mn/ZSM-5 increases with reaction temperature (being the N2 selectivity close to 100%) whereas, for Ce–Mn/TiO2, the N2 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% N2 selectivity at 300°C) is related to the presence of well-dispersed Ce–Mn mixed oxide nanoparticles, high reducibility, and a large number of surface acid sites.