Abstract
Samples of Co/SiO2 and Co/Al2O3 were prepared by means of incipient wetness impregnation (IW) and precipitation-adsorption (PA). The prepared samples were further oxidized by calcined in air and treatment of H2O2. The extent of oxidation in oxidized samples was characterized with temperature-programmed reduction (TPR). Co2O3 was dominated in PA samples, while Co3O4 was favored in IW samples.TPR results also indicated that dispersed cobalt oxides might be distinguished in two types, i.e., deposit particles (D type) negligibly perturbed by support and a species interacted with support surface (I type). Distribution of dispersed cobalt oxides between these two types depended on the method of preparation and the property of support. The IW method and silica support favored a formation of D type. However, I type was generally formed by the PA method and on alumina support. The type of Co2O3 has a significant effect on its reductive phenomena in TPR. The D type was reduced in sequential steps (Co2O3→Co3O4→CoO→Co), and Co2O3 of I type was reduced in a single step to metallic Co (Co3+→Co).