Controllable Synthesis of Defect-Rich CoMoS Catalysts with Different Morphologies for the Ultradeep Hydrodesulfurization of 4,6-Dimethydibenzothiophene

CoMoS catalysts with controllable morphology are prepared by a single-source precursor hydrothermal method using sodium diethyldithiocarbamate trihydrate (DDTC) as the ligand and the sulfur source. The effects of the single-source precursor, the pH of the hydrothermal solution, and the surfactant with respect to the morphology, nanostructure, and hydrodesulfurization (HDS) activity of the CoMoS catalyst are investigated. It is revealed that the coordination between the metal atom and DDTC can effectively control the in-plane and out-of-plane crystal growth of MoS2 and promote the formation of the CoMoS active phase. The lower pH value of the hydrothermal solution facilitates the synthesis of CoMoS catalysts with improved purity, lower crystallinity, and smaller nanocrystallites, and the different surfactants would significantly change the morphologies. For HDS activity, the conversion efficiency of 4,6-DMDBT is increased from 71 to 99% by the CoMoS catalysts that have fewer stacking layers of MoS2 slabs. While the high HDS activity is maintained, a notable improvement in selectivity for the direct desulfurization (DDS) pathway is observed for the CoMoS-CTAB catalyst, where the average slab length of MoS2 is the longest.