ACTIVE SURFACE OF GAMMA-AL2O3-SUPPORTED CO3O4

Samples of Co3O4 deposited on two types of γ-Al2O3 with different textures are investigated. A kinetic method employing reduction by hydrogen is used to provide a differential determination of the transition metal oxide surface, and magnetic and XPS measurements are also employed. It is found that, depending on the concentration of the impregnating solution, the value of the surface area of supported Co3O4 passes through a maximum. The concentration at which a maximum surface area of the active phase should be expected has been calculated, and a good correlation has been found with the experimental value. It is established that the differences in the support texture characteristics such as specific surface area, pore volume, and pore size distribution affect the active phase distribution on the support surface, and hence the interaction between the active phase and the support. It is concluded that the amount of the Co3O4 phase formed and its surface area depend not only on the impregnating solution concentration and the preparation temperature but also on the support texture. © 1994 Academic Press, Inc.