Property of a highly active bimetallic catalyst based on a supported manganese oxide for the complete oxidation of toluene

Transition metal (Cu, Co, Ni or Fe)-manganese oxide supported catalysts were prepared using a conventional impregnation technique. γ-Al₂O₃ was used as a support. Their catalytic performance in the complete oxidation of toluene was studied. Of the supported manganese catalysts evaluated, the 15wt.% Mn loading catalyst (15 Mn/Al) was found to provide the best catalytic activity. The catalytic activity of the 5wt.% Cu, Co, Ni or Fe supported catalysts was in the order 5 Cu/Al>5 Co/Al>5 Fe/Al>5 Ni/Al. A 5wt.% Cu, Co, or Ni loading on 15 Mn/Al increased the level of toluene conversion whereas a 5wt.% Fe loading resulted in a decrease in toluene conversion. The catalytic activity of the bimetal supported catalysts was in the following order: 5 Cu-15 Mn/Al>5 Co-15 Mn/Al>5 Ni-15 Mn/Al>15 Mn/Al>5 Fe-15 Mn/Al. The properties and performance of the catalysts were examined by measuring the Brunauer Emmett Teller (BET) surface area, inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR). Instrumental analysis indicated that the crystal structure, crystallinity and dispersion of the manganese oxide were strongly affected by the addition of transition metals, and that the catalytic activities of the catalysts were associated with the lattice oxygen mobility on the catalyst surface.