The superior HDS catalyst derived from a new Waugh Co-Mo polyoxometalate via cationic substitution.

• Cationic substitution was used to increase the Co/Mo ratio. • Well-defined new Waugh Co-Mo POM was used to prepare HDS catalyst. • Highly dispersed and stacked MoS 2 was controllably prepared via the POM route. • New reference for the rational design and controllable fabrication of efficient HDS catalysts. In this paper, the Waugh Co-Mo polyoxometalate (POM) (NH 4) 6 [CoMo 9 O 32 ] was prepared and cationic substituted to increase the Co/Mo ratio to 0.44 with Mo and Co atoms in a new Waugh Co-Mo POM molecule. The method was verified by X-ray diffraction, X-ray fluorescence, and infrared spectroscopy. Then, two series of Co-Mo hydrodesulfurization (HDS) catalysts were prepared using the Waugh Co-Mo POMs and traditional precursors, respectively. The HDS evaluation results showed the activities of catalysts prepared from the new Waugh Co-Mo POM is higher than the reference catalysts. For the catalyst prepared from the new Waugh Co-Mo POM, the cationic substitution provides a higher Co/Mo ratio and atomic-level proximity between Mo and Co atoms, leading to shorter and less stacked MoS 2 nano-particles and more exposure of unsaturated edges and corner sites. In addition, a weak interaction between the new Waugh Co-Mo POM and Al 2 O 3 leads to more CoMoS active phases. Catalysts prepared from the new Waugh Co-Mo POM showed excellent HDS performance, demonstrating the new Waugh Co-Mo POM is a superior precursor to construct the efficient HDS catalyst. [ABSTRACT FROM AUTHOR]