Ultrasmall Ni-Promoted WS₂ Nanocatalyst with Enhanced Number of Edge Atoms for Hydrodesulfurization

Ni-promoted WS₂ catalysts are preferred over Ni/Co-promoted MoS₂ catalysts due to their enhanced hydrodesulfurization (HDS) catalytic capability toward methylated dibenzothiophene compounds. However, it is challenging to prepare the active Ni-promoted WS₂ phase with optimal number of edge/brim sites because WO₃ and NiO have different sulfidation temperatures, which favors the formation of nonpromoted WS₂ and NiS_x phases instead of an active NiWS phase. Herein, we report a versatile method to prepare ultrasmall Ni-promoted WO₃ nanoclusters (∼3 nm) supported over γ-Al₂O₃ followed by sulfidation. The prepared nanocatalysts possess increased hydrodesulfurization catalytic activity towards dibenzothiophene (conversion for the best catalyst was 92% at 580 K) and 4,6-dimethyldibenzothiophene (conversion for the best catalyst was 57% at 580 K) compared to the conventional wet impregnated catalyst possessing similar chemical composition. The increased catalytic activity is attributed to easier reducibility (confirmed by the temperature-programmed reduction method) and sulfidability (confirmed by high-resolution transmission electron microscopy (HRTEM)) of the catalyst. Furthermore, the catalyst did not display any decrease in activity till 24 h, showcasing the catalyst stability.