Characteristic studies,by means of XRD,XPS and TPD,of MoS_x/K~+-SiO_2 catalysts for thesynthesis of mixed alcohols provided experimental evidence for the formation of Mo-S-K surface phaseand the presence of disulfide species,(S-S)~(2-),at the surface of catalysts.One of the origins of thepromoter action in shifting the selectivity from hydrocarbons to alcohols is likely that the addition ofalkali salt led to a decrease in concentration of(S-S)~(2-)at the surface,which in turn would reduce thegeneration of the reactive hydrogen. Characteristic studies, by means of XRD, XPS and TPD, of MoS_x / K ~ + -SiO_2 catalysts for thesynthesis of mixed alcohols provided experimental evidence for the formation of Mo-SK surface phase and the presence of disulfide species, (SS) ~ (2) -), at the surface of catalysts. One of the origins of the promoter action in shifting the selectivity from hydrocarbons to alcohols is likely that the addition ofalkali salt led to a decrease in concentration of (SS) ~ (2-) at the surface, which in turn would reduce the generation of the reactive hydrogen.