Synthesis of Ni–Mo–W sulphide catalysts by ex situ decomposition of trimetallic precursors

Nickel–molybdenum–tungsten sulphide unsupported catalysts were prepared by ex situ decomposition of trimetallic (Ni–Mo–W) precursors. The precursors were synthesized by impregnation of ammonium or tetraalkylammonium thiomolybdates on tungsten thiosalts (ammonium or tetraalkylammonium thiotungstates). Finally, the bimetallic precursors (Mo–W) were impregnated with Ni(NO3)2·6H2O previously dissolved in water in order to give a final molar ratio Ni:Mo:W of 2:1:1. By the ex situ decomposition (activation), the precursors were transformed under a flow of H2S (15%) in hydrogen from room temperature to 673 K at 4 K/min, dwell of 4 h at 673 K. All catalysts were tested in the hydrodesulphurization (HDS) of dibenzothiophene (DBT) and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM). Furthermore, the specific surface areas were measured using the BET method. The catalysts obtained present low specific surface areas, poorly crystalline structures with cavities and disordered structure and different catalytic activities in the HDS of DBT. The best HDS catalytic activity was shown by the sample labeled as NiMoW–H (k = 13.4 × 10−7 mol/g* s).