IntroductionHydrodesulfurization (HDS) – the removal of sulfur atoms from sulfur-containing molecules in petroleum feedstocks by hydrotreatment – is one of the most important processes of thepetroleum refining industry, which is employed to upgrade the quality of fuels [1,2]. It is driven by ever stringent environmen-tal legislation demanding very low sulfur levels in fuels. CurrentHDS technology employs sulfided Co(Ni)Mo/Al2O3catalysts [1–3].Research into improvement of activity and selectivity of HDS catalysts continues globally at a fast pace. This, among others, includes the development of new methods of preparation of Co(Ni)Mo catalysts, for example, Co chemical vapor deposition [4], addition ofcitric acid [5] and phosphorus [4], the use of new active phases for HDS catalysts, such as noble metals [6], transition metal carbides[7], nitrides [8] and phosphides [9,10].