Adsorption of thiophene on surfaces of clean and Ni-promoted molybdenum sulfide

Citation
Ja. Rodriguez et al., Adsorption of thiophene on surfaces of clean and Ni-promoted molybdenum sulfide, SURF SCI, 429(1-3), 1999, pp. L462-L468
Citations number
35
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
SURFACE SCIENCE
ISSN journal
00396028 → ACNP
Volume
429
Issue
1-3
Year of publication
1999
Pages
L462 - L468
Database
ISI
SICI code
0039-6028(19990610)429:1-3<L462:AOTOSO>2.0.ZU;2-C
Abstract
Synchrotron-based high-resolution photoemission has been used to study the interaction of thiophene with pure and Ni promoted MoSx films. The films ex hibit Mo 3d and valence spectra that are very similar to those of MoS2. On the MoSx systems, the chemistry of thiophene closely resembles that seen on MoS2(0002). The molecules are weakly chemisorbed, and most of them desorb at temperatures around 200 K. A small fraction of the adsorbed thiophene is bonded to Mo sites that have S vacancies and desorbs between 250 and 300 K . The addition of Ni enhances the chemical activity of MoSx. On the NiMoSx systems, the adsorption energy of thiophene is at least 5-10 kcal mol(-1) l arger than on pure MoSx. No dissociation of the molecules is observed on th e NiMoSx surfaces. The Ni<->S interactions reduce the reactivity of nickel, and the presence of this metal alone is not enough to promote or facilitat e the cleavage of C-S bonds in hydrodesulfurization (HDS) reactions. Hydrog en seems to play an important role in this aspect. The behavior of NiMoSx c atalysts in HDS processes is discussed in the light of these results. (C) 1 999 Elsevier Science B.V. All rights reserved.