Effects of lithium doping on the catalytic activity of Co 3O 4 in CO oxidation

Abstract

The catalytic oxidation of CO on the surface of pure and lithium-doped Co 3O 4 catalysts was carried out by a static method at various temperatures between 95 and 250 °C in an atmosphere containing 2 parts CO to 1 part oxygen at a pressure of 2 Torr. The catalyst samples were prepared by the thermal decomposition of pure basic cobalt carbonate and of cobalt carbonate mixed with different proportions of LiOH (0.75, 3 and 6 at.%) in air at 500 and 700 °C. All the doped catalysts exhibited lower activities than those of the pure oxides at all the reaction temperatures. The decrease in the catalytic activity was most pronounced for the doped catalysts prepared at 700 °C. Although doping at 500 °C was accompanied by a significant increase in the catalyst surface area, the catalytic activity of the sample was decreased. The apparent activation energy E of CO oxidation on pure Co 3O 4 prepared at 500 °C was 6.7 kcal mol −1 in the temperature range 95–150 °C. This value increased to 22.1 kcal mol −1 in the temperature range 110–145 °C on addition of 3 at.% Li to the pure catalyst. The value of E for pure Co 3O 4 prepared at 700 °C was 2.0 kcal mol −1 in the temperature range 150–220 °C which increased to 14.9 kcal mol −1 in the temperature range 200–250 °C on addition of 3 at.% Li.