The direct synthesis of methanethiol from H2S-rich syngas was investigated over sulfided Mo-based catalysts supported on SiO2. K-promoted MO/SiO2 catalysts exhibited a high activity for the synthesis of CH3SH. The incorporation of cobalt into the K-Mo/SiO2 catalyst increased the catalytic activity, but slightly decreased the selectivity to methanethiol. The selected catalysts were characterized by using X-ray diffraction (XRD), CO temperature-programmed desorption (CO-TPD), electron spin resonance (ESR), and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the potassium interacts with Mo component and increases the active sites for the CH3SH synthesis by changing the concentration of Mo5+ species after sulfidation. A mechanism for the synthesis of CH3SH was proposed. (c) 2007 Elsevier B.V. All rights reserved.