The hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities of an unsupported rhenium sulfide and a sulfided CoMo/Al2O3-SiO2 catalyst are compared using 4 6-diethyldibenzothiophene (46DEDBT) and 3-ethylcarbazole (3ECBZ) as probe molecules The active site densities and adsorption-reaction rate constants are determined from transient experiments It is found that ReS2 has an unusually high selectivity toward hydrogenation As such it has a far higher activity than CoMo/Al2O3-SiO2 for desulfurizing 46DEDBT in the absence of 3ECBZ The higher activity of ReS2 arises from a higher turnover frequency as the active site density on ReS2 is about one-third that on CoMo/Al2O3-SiO2 Due to ReS2 s higher hydrogenation power the HDS of 46DEDBT on ReS2 is less resilient to 3ECBZ inhibition than that on CoMo/Al2O3-SiO2 ReS2 shows about a sevenfold activity advantage over the CoMo/Al2O3-SiO2 catalyst in the hydrodenitrogenation of 3ECBZ The results shed some light on the HDS-HDN interactions in real-feed deep HDS (C) 2010 Elsevier Inc All rights reserved