Adding chelating agents such as 1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CyDTA) and triethylenetetraaminehexa acetic acid (TTHA) to the aqueous solution of cobalt nitrate and ammonium metatungstate used for impregnating the silica support results in enhanced activities for the hydrodesulfurization of thiophene after the catalysts have been sulfided. These chelating agents serve to retard the sulfidation of cobalt with respect to that of tungsten, which facilitates the formation of a phase in which Co atoms decorate the edges of WS2, analogous to the well-known CoMoS phase.