Selective catalytic reduction of NO by ammonia and NO oxidation Over CoO_x/CeO₂ catalysts

The selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) at low temperatures is still a major challenge in environmental catalysis research. Metal oxide based catalysts have attracted great attention due to their excellent low-temperature activity. In this study, CeO₂-supported cobalt (Co)-oxide with variable Co/Ce weight ratios were prepared by the incipient-wetness impregnation method. The effect of Co loading as well as the effect of temperature on catalytic behaviors have been studied for the NO reduction and NO oxidation reactions. Thorough characterization by means of BET, XRD, and Raman has shown the topological model of the catalyst and interpretation of the observed reactivity trends. The activity test of CoO_x/CeO₂ catalysts showed that the addition of Co enhanced the activity of NO reduction as well as that of NO oxidation. The most active catalyst with 10 wt% Co loading showed 70% NO reduction and 85% NO oxidation activity. Catalyst characterization results indicated that Co was monodispersed on ceria surface with the low Co loading amount, while Co₃O₄ was formed on ceria with high Co loading amounts that affected the overall catalytic activity.