A highly active CoMoS/Al2O3 catalyst was prepared by sonochemically synthesizing MoS2 crystallites dispersed on Al2O3 and subsequently impregnating the prepared MoS2/Al2O3 with Co(acac)(2)center dot 2H(2)O. The formation of the catalytically active CoMoS phase was promoted when Co(acac)(2)center dot 2H(2)O, instead of relatively common Co(NO3)(2)center dot 6H(2)O, was used as a Co precursor. As a result, the newly prepared catalyst exhibited about two times higher activity for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) than in the case of a catalyst prepared by the sonochemical synthesis of MoS2/Al2O3 followed by impregnation with Co(NO3)(2)center dot 6H(2)O, and even about four times higher than the activity of a catalyst prepared by sequential impregnation with Mo and Co compounds. The newly prepared catalyst enhanced the direct desulfurization (DDS) route to a greater extent than the hydrogenation route (HYD). (c) 2010 Elsevier B.V. All rights reserved.