Surface and catalytic properties of Co3O4-doped CuO–Al2O3 catalysts

The effect of Co3O4-doping on surface and catalytic properties of CuO–Al2O3 solids was investigated by using nitrogen adsorption at −196 °C and catalytic oxidation of CO by O2 at 125–225 °C. Pure and doped solids were subjected to thermal treatment at 600 and 800 °C prior to surface and catalytic measurements. The results showed that Co3O4-doping of CuO–Al2O3 solids at 600 °C caused a measurable increase in their specific surface area and the activity of CO oxidation. However, this treatment of solids calcined at 800 °C brought about a marked decrease in their catalytic activity and specific surface area. This discrepancy is discussed in terms of the effect of Co3O4-doping in increasing the dispersity of CuO crystallites for solids calcined at 600 °C and the role of Co3O4 in enhancing CuAl2O4 and CoAl2O4 formation upon heating at 800 °C. The activity of pure CuO–Al2O3 catalyst samples decreased progressively by regeneration while that of Co3O4 containing catalysts increased monotonically by regeneration to attain a high constant value after the fourth regeneration. Co3O4-treatment did not modify the mechanism of catalytic oxidation of CO with O2 but changed the concentration of catalytically-active constituents.