Solution synthesis of the unsupported Ni–W sulfide hydrotreating catalysts

Abstract

Three solution synthesis routes for the preparation of unsupported Ni–W–S hydrotreating catalysts were compared. In all of them WO 2S 2 2− core was applied as precursor, but the reaction between Ni and W species was done in different ways. The preparation methods included solution reaction between WO 2S 2 2− and nickel species in the presence of organic surfactant (liquid–liquid route), reaction of amorphous high surface area nickel compound with aqueous WO 2S 2 2− species (liquid–solid route) and reaction of amorphous WOS 2 solid with aqueous solution of nickel salt (solid–liquid route). The catalysts were characterized by several techniques including X-ray powder diffraction, specific surface area and pore volume measurements, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The catalytic activities were evaluated in thiophene hydrodesulfurization (HDS), toluene hydrogenation (HYD) and pyridine hydrodenitrogenation (HDN) reactions. It has been shown that highly active unsupported sulfides can be obtained from three routes. The highest weight activity was observed for the most finely dispersed liquid–liquid preparation. However, the relation between catalytic activity and texture is not linear and the preparation having low surface area and containing NiS bulky particles covered by curved WS 2 slabs showed the highest activity per unit of surface area.