Constructing a superior Co-Mo HDS catalyst from a crystalline precursor separated from the impregnating solution

In this work, a Co tetra-capped Keggin crystalline Co4Mo12 was separated from the impregnating solution through a self-assembly strategy. The crystalline Co4Mo12 was structurally characterized and used as a molecular platform to reveal the sulfidation procedure of the precursor in the construction of a superior Co-Mo hydrodesulfurization (HDS) catalyst. The higher HDS reactivity of the sulfide can be attributed to the structure-directing effects of the crystalline Co4Mo12 precursor. During the sulfidation procedure of the crystalline Co4Mo12 precursor, it initially decomposes at 100 degrees C and MoOxSy is produced due to the simple O-S exchange. With the temperature increasing to 180 degrees C, the Keggin-type structure in crystalline Co4Mo12 begins to collapse and four groups of edge-shared CoMo2O(S)(13) triplets are formed. As the temperature continues to increase, the CoMo2O(S)(13) triplets collapse and MoS2 is formed due to the deep O-S exchange at 200 degrees C. In this procedure, the water molecules serving as ligands can retard the sulfidation of Co promoters, which can guarantee Co-promoter interaction and re-dispersion at the edges of MoS2 nanoparticles to form the type II CoMoS active phase with higher performance. These results suggest that the crystalline Co4Mo12 precursor can be a superior precursor for the rational design and controllable preparation of HDS active sites.

Automated summary

In this study, a Co4Mo12 crystalline material was isolated from an impregnating solution using a self-assembly strategy. This crystalline Co4Mo12 was then used as a molecular platform to understand the sulfidation process in the construction of a high-performance Co-Mo hydrodesulfurization catalyst. The results show that the crystalline Co4Mo12 precursor can serve as an excellent precursor for the rational design and controllable preparation of HDS active sites.