Abstract
Cobalt and manganese oxide samples supported on cordierite (commercial grade) were prepared by wet impregnation method using finely powdered support material and cobalt or manganese nitrate. The extent of loading was varied between 5 and 20
wt.% Co
3O
4 or Mn
2O
3. The physicochemical, surface and catalytic properties of the thermally treated solids (350 and 700
°C) were investigated using XRD, EDX, nitrogen adsorption at −196
°C, CO-oxidation by O
2 at 225–275
°C and H
2O
2-decomposition in a aqueous solution at 30–50
°C.
The results obtained revealed that the employed cordierite preheated at 350–700
°C was orthorhombic well crystallized magnesium aluminum silicate (Mg
2Al
4Si
5O
18). The manganese oxide-containing cordierite samples consisted of manganese oxide–cordierite solid solution. While all diffraction peaks of Co
3O
4 were observed in the diffractograms of cobalt-containing cordierite preheated at the same temperatures. The specific surface area of cordierite support material increases progressively by increasing the amount of manganese or cobalt oxide present.
The catalytic activity of cordierite was found to increase almost linearly by increasing the amount of cobalt or manganese oxide added. Cobalt oxide-containing catalysts calcined at 350–700
°C exhibited catalytic activity in CO-oxidation by O
2 higher than those measured for manganese oxide-containing catalysts calcined at the same temperatures. Opposite results have been observed in the case of H
2O
2-decomposition. These findings indicate that the active sites taking part in CO-oxidation by O
2 are different from those involved in H
2O
2-decomposition.