Ni(Co)-Mo-W sulphide unsupported HDS catalysts by ex situ decomposition of alkylthiomolybdotungstates

Ni(Co)-Mo-W sulphide unsupported hydrodesulphurization (HDS) catalysts were prepared by ex situ decomposition of trimetallic (Ni-Mo-W) precursors. The precursors were synthesized by reaction of the tetraalkylammonium thiomolybdotungstates salts, (R4N)4MoWS8 (where R=H, methyl, propyl) with an aqueous solution of Ni(Co)Cl2·6H2O in order to give molar ratios of Ni/[Ni+(Mo+W)]=0.5 and Co/[Co+(Mo+W)]=0.3. A new method by the ex situ activation was used. First, the precursors were treated in a stainless steel vessel of 45mL volume at 523K for 2h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H2S/H2 (15vol.% H2S) from room temperature to 673K, dwell of 2h at 673K. All catalysts were tested in the HDS of dibenzothiophene (DBT) and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET specific surface area measurements.