ULTRAFINE CATALYSTS FOR HYDRODESULFURIZAT ION .2. SURFACE-PROPERTIES OF UFP-MO AL2O3 CATALYSTS/

XPS was used for determining the surface properties of UFP-Mo/Al2O3. I t is shown that all molybdenum existed in Mo6+ form on the surface of oxidized UFP-Mo/Al2O3 catalysts, while a mixture of Mo6+, Mo4+, S6+ as well as S2- was observed on the surface of the catalysts after HDS re action. The ratio of Mo and S species with different valences ispronou ncedly affedted by the preparation method and the Mo loading. The port ion of Mo6+ and S6+ decreases with increasing Mo loading. The contents of Mo6+ and S6+ Of s-UFP-MO/Al2O3 catalysts are higher than those of i-UFP-Mo/Al2O3 for the same Mo loading.