Abstract: The dispersion of Co and Mo on phosphorus and potassium modified γ-Al₂O₃ was investigated by X-ray diffraction, BETsurface areas and magnetic susceptibility analysis. It was found that molybdenum can no longer reach a single layered dispersion as it does on γ-Al₂O₃ support, but forms large crystallite of MoO₃ on the H₃PO₄ treated γ-Al₂O₃ support. While, cobalt oxide is highly dispersed with the help of phosphorus treatment. The resulting surface cobalt compound was recognized as staying in the tetrahedral coordination state. A-AlPO₄ like surface compound on the phosphorus modified γ-Al₂O₃ was supposed and the influence of phosphorus on the dispersion of Co and Mo was explained accordingly. Effects of potassium on the dispersion of Co and Mo were also reported and discussed here in.

Key words: γ-Al₂O₃, Co-Mo based catalyst, dispersion