Atomic scale analysis of sterical effects in the adsorption of 4,6-dimethyldibenzothiophene on a CoMoS hydrotreating catalyst

Signe S. Grønborg, Manuel Šaric, Poul Georg Moses, Jan Rossmeisl, Jeppe V. Lauritsen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The low catalytic hydrodesulfurization (HDS) activity toward sterically hindered sulfur-containing molecules is a main industrial challenge in order to obtain ultra-low sulfur diesel. In this study we report a combined Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) investigation of the adsorption of the sterically hindered sulfur-containing molecule 4,6-dimethyldibenzothiophene (4,6-DMDBT) onto a hydrotreating model catalyst for the Co promoted MoS2 (CoMoS) phase. The molecular adsorption occurs exclusively on the Co-promoted S-edge, most predominantly in a precursor-like diffusive physisorption referred to as delocalized π-mode. 4,6-DMDBT adsorption directly in a S-edge sulfur vacancy is observed exclusively in S-edge corner vacancies in an adsorption configuration reflecting a σ-coordination. STM movies reveal dynamic conversion between the σ-mode and an on-top π-adsorption providing a link between different adsorption sites and hence between the hydrogenation and direct desulfurization pathways in HDS. The low overall direct desulfurization activity of 4,6-DMDBT and related molecules is consistent with the low occurrence of S-vacancies on CoMoS S-edges predicted under HDS conditions in this study.
Original languageEnglish
JournalJournal of Catalysis
Volume344
Pages (from-to)121-128
Number of pages8
ISSN0021-9517
DOIs
Publication statusPublished - 2016

Keywords

  • CoMoS
  • Density functional theory
  • Hydrodesulfurization
  • Hydrotreating
  • Scanning tunneling microscopy
  • Sterical hindrance
  • Ultra-low sulfur diesel

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