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

• Published in: Surface science Vol. 429; no. 1; pp. L462 - L468
• Main Authors: Rodriguez, J.A., Dvorak, J., Capitano, A.T., Gabelnick, A.M., Gland, J.L.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.06.1999; Amsterdam Elsevier Science; New York, NY
• Subjects: Aromatics; Chemisorption; Chemistry; Exact sciences and technology; General and physical chemistry; Molybdenum sulfide; Nickel; Photoelectron spectroscopy; Solid-gas interface; Sulfur; Surface physical chemistry; Thiophene; Aromatics; Chemisorption; Molybdenum sulfide; Nickel; Thiophene; Sulfur; Photoelectron spectroscopy; Gas solid adsorption; Transition metal compounds; Gas solid interface; Photoelectron spectrometry; Transition metal; Experimental study
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(99)00348-9

Synchrotron-based high-resolution photoemission has been used to study the interaction of thiophene with pure and Ni promoted MoS x films. The films exhibit Mo 3d and valence spectra that are very similar to those of MoS 2. On the MoS x systems, the chemistry of thiophene closely resembles that seen on MoS 2(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 MoS x . On the NiMoS x systems, the adsorption energy of thiophene is at least 5–10 kcal mol −1 larger than on pure MoS x . No dissociation of the molecules is observed on the NiMoS x surfaces. The Ni↔S interactions reduce the reactivity of nickel, and the presence of this metal alone is not enough to promote or facilitate the cleavage of C–S bonds in hydrodesulfurization (HDS) reactions. Hydrogen seems to play an important role in this aspect. The behavior of NiMoS x catalysts in HDS processes is discussed in the light of these results.