Comparative Study of In situ/Ex situ Activated Trimetallic NiMoW Sulfide Catalysts Prepared from Ammonium Thiomolybdotungstates

摘要

Unsupported trimetallic NiMoW sulfide catalysts with high hydro-desulphurization activities are prepared from Ni-containing ammonium thiomolybdo tungstates by in situ and ex situ activation. These precursors are prepared by adding an aqueous NiCl2 solution to an aqueous (NH4)4MoWS8 solution in either a 1:1 or 0.5:1 Ni/Mo(W) molar ratio. The resulting precursors Ni0.5/(NH4)4MoWS8 and Ni/(NH4)4MoWS8 yield Ni0.5MoW-in situ, NiMoW-in situ, Ni0.5MoW-ex situ and NiMoW-ex situ sulphide catalysts, respectively. The activation method affects both physical and chemical properties, such as macro and microstructure, crystalline structure, specific surface area, N2 adsorption–desorption isotherms. The in situ/ex situ activation of these ammonium thiotrimetallate precursors leads to a mesoporous structure with a pore size ranging from 20 to 60 ? and type IV N2 adsorption–desorption isotherms. X-ray diffraction patterns of unsupported NiMoW sulfide catalysts correspond to those of a microcrystalline material, with outstanding reflections attributed to MoS2, WS2, NiS, and Ni9S8 phases.