Cobalt catalysts supported on silica were prepared by an impregnating method and characterized using temperature-programmed reduction (TPR). H, was used as the reduction agents. The two-stage reduction was observed. Co3O4 was reduced to CoO and then reduced to metallic Co. The activation energies for the two reduction steps of cobalt oxide are 94.43 and 82.97 kJ mol(-1), respectively. The simulation by reduction models of the TPR patterns presents well-fitting of two-dimensional nucleation according to Avarmi-Erofeev model for the reduction Of Co3O4 to CoO and unimolecular model for the reduction of CoO to Co. (C) 2004 Elsevier B.V. All rights reserved.