Influence of sulfidation conditions on morphology and hydrotreating performance of unsupported Ni-Mo-W catalysts

Oxidic unsupported Ni-Mo-W catalysts were prepared from a precipitate by high-temperature hydrothermal synthesis. The catalysts were sulfided in-situ by CS2 and H2 under different sulfiding conditions. The catalytic activity and selectivity were studied in the model reactions of naphthalene hydrogenation (HYD), quinoline hydrodenitrogenation (HDN), and dibenzothiophene (DBT) hydrodesulfurization (HDS). The sulfided catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and energy dispersive spectrum (EDS) mapping. Sulfided unsupported Ni-Mo-W catalysts showed visible diffraction peaks of Ni3S2 and MoS2/WS2. As the sulfiding temperature or time increased, the Ni3S2 and MoS2/WS2 nanoparticles agglomerated, with MoS2/WS2 lamella curved to some extent. Specifically, the stacking of the MoS2/WS2 slabs increased with increasing sulfidation time. Meanwhile, the catalysts showed higher HDS, HDN, and HDAr activities when the sulfiding temperature was 320 °C. However, the hydrogenation activity decreased above 340 °C.