Abstract: The chemical states and composition of the surface species of sulfided MoO_3/γ-Al_2O_3 catalysts with the promotion of variable KCI contents have been investigated and correlated to the sulfidation and reduction properties of the catalysts by means of XPS, XRD, ESR and TPR techniques. An interaction between the potassium cations and the molybdenum component occurred and was stoichiometrically saturated at a KCI loading with the K/Mo atomic ratio of 0.8. At the K/Mo ratios below 0.8 the potassium cations interacted with molybdenum component to form the interacting species and were enriched on the catalyst surface, while chloride anions were free and lost during preparation. At the K/Mo ratios above 0.8 the surplus potassium cations directly combined with the chloride anions to form bulk KCl crystallites. Due to the existence of the potassium promoter, the interaction between the supported Mo(VI) and the γ-Al_2O_3 became weaker and the sulfidation and reduction for catalysts were partly retarded. The active sites or phases, which were responsible for the alcohol formation activity, could be produced by sulfiding the interacting species composed of the potassium and molybdenum components.

Key words: Potassium promoter, K-MoO₃/γ-Al₂O₃ catalysts, Structure characterization, Sulphidation, Reduction