Insight into the properties of MnO2-Co3O4-CeO2 catalyst series for the selective catalytic reduction of NOx by C3H6 and NH3

Highlights: • All of the catalysts were synthesized by a co-precipitation technique. • MCC-0.75 showed excellent performance at low-temperature conditions with both reductants. • Irrespective of ceria loading, the catalysts performed better for the C₃H₆-SCR than for NH₃-SCR. • MCC catalysts predominantly exhibited oxidative potential as exposed by TPR H₂. A series of MnO₂-Co₃O₄-CeO₂ catalysts with different ceria loading (0.75, 1.26 and 1.88 Ce/Mn molar ratio) were synthesized by a co-precipitation technique and the catalytic activity was tested for selective catalytic reduction of NO_x by C₃H₆ or NH₃. The catalysts were characterized by various physicochemical techniques to examine the effect of ceria loading on the properties of catalysts, such as crystallinity of metal species, surface area, porosity, and acidity using physical adsorption analysis, SEM-EDX, H₂-TPR, XRD, NH₃-TPD and in-situ FTIR spectroscopy. Ceria loading had a significant effect on the reduction of NO_x, with the catalyst having low amount of ceria loading (Ce/Mn = 0.75) showing excellent performance at low-temperature conditions, but the activity declined at higher temperature. The high ceria loading (Ce/Mn = 1.88) catalyst showed poor activity compared to the counterparts owing to the lower number of acid sites and the resulting lower adsorption capacity.