For the first time hydrodesulfurization reaction of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was performed on bulk NiB alloy in the presence of nitrogen compound - carbazole. Before and after reaction the catalysts were characterized by X-ray diffraction (XRD), also by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and differential scanning calorimetric analysis (DSC) and by X-ray photoelectron spectroscopy (XPS) - after HDS reaction. The surface and metallic phase were determined by N-2 physisorption and CO chemisorption. During the HDS reaction partially formed Ni3S2, metallic Ni and Ni3B were observed. The activity of the catalyst was mainly attributed to the presence of Ni and Ni3B phases. In the absent of N-compound the main product was the 3-(3'-methylcyclohexyl)-toluene (MCHT) - formed via hydrogenation route (HYD route). At lower contribution of direct desulfurization route (DDS route), products like 3,3'-dimethylbiphenyl (3,3'-DMBPh) were also formed, but no fully hydrogenated product (3,3'-dimethylbicyclohexyl) was observed. In the presence of carbazole the distribution of HDS products was the same, but the activity was lower due to the HDN competition reaction. Based on these results and after calculated kinetics, it can be assumed that the rate of HDS of the 4,6-DMDBT, catalyzed by NiB alloy, is a first order reaction with respect to the substrate concentration for alone process of HDS, while for the same catalyst in case of simultaneous HDS/HDN reactions, this rate is independent of the 4,6-DMDBT concentration (zero-order) in the range of contact times studied. (C) 2014 Elsevier B.V. All rights reserved.