Unsupported nano-phase MoS2, Cos, and CoS-MoS2 (Mo/Co mole ratio similar to6/1) materials were prepared in hexadecane by sonolysis of the corresponding metal carbonyls at similar to50degreesC 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 similar to20 nm mean particle diameter, Cos was similar to50 nm and the mixed-metal CoS-MoS2 could be viewed as a composite in which smaller MoS2 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. (C) 2003 Elsevier B.V. All rights reserved.