Synergism in alumina-supported noble metals and molybdenum stacked-bed catalysts via spillover hydrogen in gas–oil hydrodesulphurization

A study is made of Ru/γ-Al2O3//Mo/γ-Al2O3, Rh/γ-Al2O3//Mo/γ-Al2O3, Pd/γ-Al2O3//Mo/γ-Al2O3, and Pt/γ-Al2O3//Mo/γ-Al2O3 stacked beds, separated by SiO2, in the gas–oil hydrodesulphurization reaction. Synergism between these beds is clearly detected. This synergism occurs in the absence of mixed phases. The results show that the presence of hydrogen spillover must be considered to explain the promotion effects in all HDS the reactors in which sulphides of Ru, Rh, Pd or Pt, and Mo are present.