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

The inelastic neutron scattering (INS) spectra of thiophene adsorbed on alu mina, MoS2/alumina and CoMoS2/alumina catalysts reduced in hydrogen were ob tained for surface concentrations of one thiophene monolayer or less. A ser ies of model complexes was also investigated: [Cr(CO)(3)(eta(5)-thiophene)] , [Mn(CO)(3)(eta(5)-thiophene)][CF3SO3], [Fe(eta(5)-C5H5)(CO)(2)(eta(1)-S-t hiophene)][BF4] and [Fe(eta(5)-C5H5) (CO)(2)](2). The spectra of adsorbed t hiophene were obtained by subtraction of the spectra of the bare catalysts. Adsorbed thiophene was identified on the alumina support. The mass of thio phene adsorbed on the catalysts increased with increasing molybdenum conten t in the catalyst and most significantly with cobalt. Adsorbed thiophene in teracts weakly with the surface; it is more like pure thiophene than co-ord inated thiophene. It lies mostly with the molecule aligned parallel with th e surface with possibly a small proportion (5-10%) upright (S-bound). We di scuss how these results help us to understand the role of the catalyst in t hiophene hydrodesulfurisation.