Synthesis of unsupported Ni–W–S hydrotreating catalysts from the oxothiosalt (NH4)2WO2S2

Synthetic routes for the preparation of unsupported Ni-W-S hydrotreating catalysts were studied. In the preparations studied, amorphous tungsten oxysulfide WOxSy was used obtained from the acid condensation or thermal decomposition of (NH4)2WO2S2 salt. Amorphous WOxSy solid was promoted by nickel salt solutions and eventually stabilized by addition of organic molecules. The products were characterized by X-ray powder diffraction, specific surface area and pore volume measurements. The catalytic activities of Ni-W-S systems were evaluated for the thiophene hydrodesulfurization (HDS) reaction. It has been shown that highly active unsupported tungsten sulfides can be obtained from thermal decomposition of (NH4)2WO2S2 but not from acid condensation. Addition of organics such as nonionic Triton 114 surfactant to the impregnating solution strongly improved the textural properties and HDS activity of the unsupported Ni-W-S catalysts.