Ni-MoS₂ supported on carbon nanofibers as hydrogenation catalysts: Effect of support functionalisation

Fishbone carbon nanofibers (CNF) were functionalised in acidic media using nitric or nitric/ sulfuric mixtures in order to introduce variations in their surface chemistry. The textural properties and surface chemistry of the functionalised CNF were characterized by Transmission Electron Microscopy (TEM), N2 adsorption, X-ray diffraction, temperature programmed desorption and X-ray photoelectron spectroscopy. Functionalised CNF thus prepared were used as catalytic support for NiMo catalysts. Resulting catalysts were composed by CNF coaxially coated by Ni-decorated MoS₂ slabs, with different lengths and stacking degrees as a function of the functionalisation treatment, as TEM study revealed. Catalysts were evaluated in the hydrogenation of anthracene, a model compound representing polyaromatic groups present in heavy oil fractions. Catalysts prepared with the support functionalised by the less severe treatment, which led to short and defective MoS₂ slabs, showed higher hydrogenation activity. On the other hand, harsher functionalisation treatment led to the formation of long stacked MoS₂ slabs, resulting in lower performance towards anthracene hydrogenation.