This study reports the characterization of the basic properties of supported sulfide phases (Mo, CoMo, Ru and Pt) using pyrrole and deuterated chloroform as probe molecules. Both molecules adsorb dissociatively on the Al2O3 support, preventing the characterization of the sulfide phase. On SiO2 supported catalysts, no basic sites are detected on the support and CDCl3 adsorption leads to the formation of a (C-D...S) hydrogen bond which is evidenced by a new ?(C-D) band, downward shifted by ~31 cm-1 as compared  to the gas phase. This assignmrent has been confirmed by comparing the ?(CD)  IR spectra obtained on the sulfided catalysts with those obtained in CDCl3-organic sulfide solutions and by DFT modeling. The latter leads to computed ?(C-D) frequency shifts of 25-40 cm-1, consistent with the experiment. Such a ?(C-D) frequency indicates that these metal sulfides present a weak basicity and should lead to acid �SH groups upon hydrogen dissociation.

Basic properties of supported transition metal sulfides: Combined DFT and infrared study

240th National Meeting (2010)

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