Applied Catalysis A: General 258 (2004) 83–91 Sono synthesis and characterization of nano-phase molybdenum-based materials for catalytic hydrodesulfurization Devinder Mahajan a,b,∗ , Christopher L. Marshall c , Norma Castagnola c , Jonathan C. Hanson d a Energy Sciences and Technology Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA b Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY 11794-2275, USA c Chemical Engineering Division, Argonne National Laboratory, Argonne, IL 60439-4837, USA d Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973-5000, USA Received 23 April 2003; received in revised form 5 August 2003; accepted 14 August 2003 Abstract Unsupported nano-phase MoS 2 , CoS, and CoS-MoS 2 (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 MoS 2 in hexadecane did not result in nano-sizing. The TEM images showed that the synthesized MoS 2 were aggregates of ∼20 nm mean particle diameter, CoS was ∼50 nm and the mixed-metal CoS-MoS 2 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 MoS 2 and the sharp peaks were consistent with a more crystalline CoS-MoS 2 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 MoS 2 sample. In the HDS comparative activity study of dibenzothiophene, the synthesized nano-phase MoS 2 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. © 2003 Elsevier B.V. All rights reserved. Keywords: Sonolysis; Hydrodesulfurization; Nano-catalysis 1. Introduction The continuing degradation of crude oil quality and the new impending environmental regulations to further limit sulfur to <30 ppm in refined fuels are new challenges fac- ing refineries. For the pretreatment of heavy oils to remove heteroatoms such as sulfur, a two-stage chemical upgrading process that involves removal of heteroatoms and hydrogen addition is employed with most of the work reported on hy- drodesulfurization (HDS) and hydrodenitrogenation (HDN) [1,2]. Dealing specifically with sulfur, it is the organic form, present as thiophene, dibenzothiophene (DBT), other large S-containing aryl-ring systems, and linear alkyl sulfides that are difficult to remove. Catalyst systems involving heteroge- neous [2], homogeneous [3] and enzyme [4,5] based systems have been evaluated for sulfur removal from diesel and heavy crudes. Typically, commercial hydrodesulfurization (HDS) ∗ Corresponding author. Tel.: +631-344-4985; fax: +631-344-7905. E-mail address: dmahajan@bnl.gov (D. Mahajan). catalysts are heterogeneous bimetallic systems, namely mi- crometer (m)-sized MoS 2 supported on -Al 2 O 3 , contain- ing Co or Ni promoters, that operate at high temperatures of ∼400 ◦ C but S removal is limited to ∼300 ppm [2]. It is highly desirable to develop new commercially viable pro- cesses that can essentially achieve complete sulfur removal from crudes. An extensive body of data has been reported on the Mo and W based catalyst systems [2]. It is known that only a fraction of potentially active catalyst sites are utilized in typ- ical micrometer-sized heterogeneous catalysts. Daage and Chianelli argued that creating smaller particles of MoS 2 (with a concomitant increase in “edge” sites) should im- prove both the activity and selectivity of HDS catalysis [6]. This model was validated in the work carried out with pil- lared MoS 2 with Co 6 S 8 clusters when it was shown that HDS activity increased with smaller MoS 2 particles without increasing undesirable ring hydrogenation [7]. It is gener- ally agreed that in the promoted HDS catalysts, the Co (or Ni) active sites lie along the edges [8] and MoS 2 is viewed 0926-860X/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2003.08.014