Reduction property and catalytic activity of Ce 1− XNi XO 2 mixed oxide catalysts for CH 4 oxidation

Abstract

Ce 1− X Ni X O 2 oxides with X varying from 0.05 to 0.5 were prepared by different methods and characterized by XRD and TPR techniques. Ce 0.7Ni 0.3O 2 sample prepared by sol–gel method shows the highest reducibility and the highest catalytic activity for methane combustion. Three kinds of Ni phases co-exist in the Ce 1− X Ni X O 2 catalysts prepared by sol–gel method: (i) aggregated NiO on the support CeO 2, (ii) highly dispersed NiO with strong interaction with CeO 2 and (iii) Ni atoms incorporated into CeO 2 lattice. The distribution of different Ni species strongly depends on the preparation methods. The highly dispersed NiO shows the highest activity for methane combustion. The NiO aggregated on the support CeO 2 shows lower catalytic activity for methane combustion, while the least catalytic activity is found for the Ni species incorporated into CeO 2. Any oxygen vacancy formed in CeO 2 lattice due to the incorporating of Ni atoms adsorbs and activates the molecular oxygen to form active oxygen species. So the highest catalytic activity for methane combustion on Ce 0.7Ni 0.3O 2 catalyst is attributed not only to the highly dispersed Ni species but also to the more active oxygen species formed.