The inelastic neutron scattering (INS) spectra of thiophene adsorbed on MoSdalumina catalysts are compared with the spectrum of free thiophene. Changes in the vibrational modes of thiophene due to interaction of thlophene with the catalyst are observed. On the sulfided not-reduced catalyst out-of-plane C-H motions of thiophene are modified. On the reduced catalyst In-plane motions of a-H's are also modified. Evidently the thiophene molecules lie flat on the sulflded catalyst and, in addition on the reduced catalyst, bind to the exposed molybdenum centre through ring sulfur with consequent modification of the a-H motions.

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