A procedure for the preparation and promotion of highly loaded MoS2/Al2O3 catalysts (21 wt% Mo) obtained in aqueous solution by the reduction of (NH4)(2)MOS4 with N2H4 in the presence of Al2O3 was studied. Treating the freshly prepared material with acetone results ill the formation of carbon species (ca. 1 wt% C) that make it possible to maintain a high dispersion of the MoS2 particles. Several Co-promoted MoS2/Al2O3 catalysts were prepared with different methods and Co precursors. Refluxing with Co(acac)(2) (.) 2H(2)O dissolved in organic solvent proved to be the most efficient method for promoting highly loaded carbon-stabilized MoS2/Al2O3. The catalysts obtained can be used directly in the thiophene hydrodesulfurization reaction without any additional sulfidation, and they exhibit a much higher activity than a commercial reference catalyst. An EXAFS study revealed that the acetylacetonate precursor is decomposed during the refluxing treatment and gives new species in which Co is surrounded by sulfur instead of oxygen. The formation of a highly dispersed CoMoS phase was observed after further thiophene hydrodesulfurization reaction. (C) 2004 Elsevier Inc. All rights reserved.