Atomic-scale insight into adsorption of sterically hindered dibenzothiophenes on MoS and Co-Mo-S hydrotreating catalysts

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  • A.K. Tuxen, Denmark
  • H.G. Füchtbauer, Denmark
  • Burcin Temel, Department of Physics, Denmark
  • Berit Hinnemann, Department of Physics, Denmark
  • H. Topsoe, Haldor Topsoe A/S
  • ,
  • K.G. Knudsen, Haldor Topsoe A/S, Denmark
  • F. Besenbacher
  • J.V. Lauritsen
Sterical hindrance of large S-containing molecules is known to be a significant cause of low hydrodesulfurization activity. To shed light on the atomistic aspects of such steric effects, we use atom-resolved scanning tunneling microscopy (STM) to probe the detailed adsorption configurations of dibenzothiophene (DBT) and alkyl-substituted DBT molecules on both unpromoted and Co-promoted MoS nanoclusters. We show that the unsubstituted DBT molecule can adsorb directly through its sulfur atom at sulfur vacancies on the nanocluster. However, only vacancies at corner sites are found to be accessible for DBT adsorption. In a similar way, DBT is found to adsorb on the Co-Mo-S sites exposed at the corners of the Co-promoted nanoclusters. In contrast, the 4,6-DMDBT molecule adsorbs in a flat configuration on the brim sites of the MoS clusters without the requirement of a nearby vacancy. Our findings support a model where hydrogenation and sulfur extrusion may take place on different sites.
Original languageEnglish
JournalJournal of Catalysis
Pages (from-to)146-154
Number of pages9
Publication statusPublished - 1 Nov 2012

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