The influence of zinc on the surface properties of cobalt-alumina catalysts

Abstract

Addition of a small quantity of zinc to γ-Al 2O 3 was studied with respect to influence on the surface properties of a series of Co Al 2O 3 catalysts. ESCA and ISS results indicate that at low cobalt concentrations (≤8% Co) the presence of zinc can enhance formation of a cobalt “surface spinel” resulting from the diffusion of Co ions into tetrahedral sites of the γ-Al 2O 3 support. At higher cobalt loadings a drastic increase in the ESCA and ISS metal/support intensity ratios is seen relative to catalysts without zinc. X-Ray diffraction data indicate that the increases in intensity ratios result from an increase in dispersion, i.e., generation of smaller cobalt oxide crystallites in the zinc-doped catalysts. For a series of catalysts having fixed cobalt concentrations, the influence of particle size on ESCA and ISS intensity ratios was determined.