Interaction of thiophene with a molybdenum disulfide catalyst—an inelastic neutron scattering study

The inelastic neutron scattering (INS) spectra of thiophene adsorbed on alumina, MoS2/alumina and CoMoS2/alumina catalysts reduced in hydrogen were obtained for surface concentrations of one thiophene monolayer or less. A series of model complexes was also investigated: [Cr(CO)3(η5-thiophene)], [Mn(CO)3(η5-thiophene)][CF3SO3], [Fe(η5-C5H5)(CO)2(η1-S-thiophene)][BF4] and [Fe(η5-C5H5) (CO)2]2. The spectra of adsorbed thiophene were obtained by subtraction of the spectra of the bare catalysts. Adsorbed thiophene was identified on the alumina support. The mass of thiophene adsorbed on the catalysts increased with increasing molybdenum content in the catalyst and most significantly with cobalt. Adsorbed thiophene interacts weakly with the surface; it is more like pure thiophene than co-ordinated thiophene. It lies mostly with the molecule aligned parallel with the surface with possibly a small proportion (5–10%) upright (S-bound). We discuss how these results help us to understand the role of the catalyst in thiophene hydrodesulfurisation.