Promoting synergy in CoW sulfide hydrotreating catalysts by chelating agents

Adding chelating agents such as 1,2-cyclohexanediamine-N,N,N',N'-tetraaceti c acid (CyDTA) and triethylenetetraaminehexa acetic acid (TTHA) to the aque ous solution of cobalt nitrate and ammonium metatungstate used for impregna ting the silica support results in enhanced activities for the hydrodesulfu rization of thiophene after the catalysts have been sulfided. These chelati ng 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 dec orate the edges of WS2, analogous to the well-known CoMoS phase. (C) 2001 A cademic Press.