Complete n-hexane oxidation over supported Mn–Co catalysts

Two series of Co–Mn samples were prepared by impregnation of silica with aqueous solutions of Co(NO3)2·6H2O and/or Mn(NO3)2·6H2O. Cobalt oxide was the predominant phase in one of the series and manganese was used as the promoter. The major component in the second series was manganese oxide and Co was the promoter. The prepared samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) and tested in the reaction of complete n-hexane oxidation. The catalytic activity of both single component cobalt and manganese samples was similar, however, a combination between the two elements changed significantly the activity and this depended on the method of preparation. Catalysts prepared by a common solution of Co- and Mn nitrates manifested a considerable increase in activity as a result of very low crystallinity of the supported metal oxide phases, partial enrichment of the surface with cobalt and uniform distribution of oxide agglomerates on the support.