Effects of stoichiometric composition and surface characteristics on the catalytic activity of CoO catalyst

Abstract

The catalytic oxidation of CO on various CoO catalysts was studied using a static technique at temperatures of 110 and 170 °C and a pressure of 2 Torr ( CO+ 1 2 O 2 ). The CoO samples were prepared by the thermal decomposition of basic cobalt carbonate under a reduced pressure of 10 -6 Torr at temperatures varying between 225 and 350 °C. The catalytic activity of the various samples in the oxidation of CO at 110 °C was found to be dependent on the specific surface area, the pore size and the degree of deviation from stoichiometric composition. In contrast, these properties had no influence on catalyst activity when the catalytic reaction was carried out at 170 °C. These results are attributed to the formation of the Co 3O 4 phase by the interaction between the oxygen of the reaction mixture and the CoO. The newly formed phase catalyses the oxidation of CO with much more efficiency than CoO does. This enhanced activity overlaps the role played by the surface characteristics of the solid. The results obtained for the oxidation of CO on CoO catalysts at 110 °C are in agreement with the electronic theory of catalysis.