SiO2-supported Co-Mo and Co-W sulfide catalysts with varying, Mo(W) content were prepared from Mo(W)S-2/SiO2 presulfided at 673-873 K with a CVD technique using Co(CO)(3)NO as a precursor to Co Sulfide. The Al2O3-supported counterparts were also briefly studied. The catalysts were characterized by NO adsorption. TEM, XPS, W L-3-edge XANES, and the magnetic measurements of Co. The Co atoms in the Co-W-S phase showed an antiferromagnetic property. The TOF of the hydrodesulfurization of thiopene on the Co-Mo(W)-S phase significantly increased as the presulfidation temperature of Mo(W)S-2/SiO2 increased front 673 to 873 K, whereas it was independent of the loading of Mo(W). The TOFs on the Co-Mo-S phase and the Co-W-S phase were close to each other but strongly dependent on the support. It is suggested that complete sulfidation and the formation of stacked Mo(W)S-2 particles do not necessarily result in the formation of Co-Mo(W)-S Type II. (c) 2005 Elsevier Inc. All rights reserved.