The activity and promoter effect of Co and Ni for MoS2/Al2O3 and MOS2/TiO2 catalysts during the hydrodesulfurization of three sulfur containing molecules (thiophene, DBT and 4,6-DMDBT) that are transformed with different contributions of the direct desulfurization (DDS) or hydrogenation (HYD) reaction pathways was investigated. The results show that the greater activity displayed by Mo/TiO2 comes from a moderate increase in the direct desulfurization capability but mostly from the increase in the hydrogenating character due to the stronger MoS2 metallic character induced by TiO2. Therefore, the HDS selectivity is strongly influenced by the support. MoS2 supported on TiO2 is not as effectively promoted by Co or Ni as MoS2 supported on alumina, because it presents fewer defects and mostly exposes the Mo-edge, which is difficult to promote. The promoter incorporation benefits mainly the direct desulfurization route and the activity of the hydrogenation sites in MoS2/TiO2 is only weakly sensitive to the promotion. (C) 2015 Elsevier B.V. All rights reserved.