Sono synthesis and characterization of nano-phase molybdenum-based materials for catalytic hydrodesulfurization

Unsupported nano-phase MoS₂, CoS, and CoS-MoS₂ (Mo/ Co mole ratio ∼6/1) materials were prepared in hexadecane by sonolysis of the corresponding metal carbonyls at ∼50 °C in high (>90%) yields as measured by the evolved carbon monoxide. Direct sonolysis of commercial micron-sized MoS₂ in hexadecane did not result in nano-sizing. The TEM images showed that the synthesized MoS₂ were aggregates of ∼20 nm mean particle diameter, CoS was ∼50 nm and the mixed-metal CoS-MoS₂ could be viewed as a composite in which smaller MoS ₂ particles resided on the larger crystallites of CoS. The broad XRD peaks were consistent with nano-structured MoS₂ and the sharp peaks were consistent with a more crystalline CoS-MoS₂ species. The sharp peaks did not fit any single CoS pattern suggesting multiple phases. The XRD data showed that sonolysis did not alter the morphology of the micron-sized commercial MoS₂ sample. In the HDS comparative activity study of dibenzothiophene, the synthesized nano-phase MoS₂ exhibited more than an order of magnitude higher activity than its commercial micron-sized counterpart and the addition of Co further enhanced the activity. The HDS activity mirrored the temperature programmed reduction data. Interestingly, the nano-phase materials were less active for hydrogenation of 1-octene during the HDS study.