A study of Co/Mo/Al₂O₃ hydrodesulphurization catalysts and related model compounds by XPS and X-ray absorption spectroscopy (XANES and EXAFS)

Abstract

A detailed investigation of sulphided Co/Mo/Al₂O₃ catalysts, their oxide precursors and several model oxides and sulphides of cobalt and molybdenum has been carried out using X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XANES and EXAFS). Octahedrally coordinated Co(II) and Mo(IV) are shown to be present in a sulphidic environment on the surfaces of these catalysts. The surface species contain an excess of sulphur, probably involving disulphide linkages. The surface compositions of the catalysts examined conform to the general formula Co^IIMo_2n^IV (2n+3)S₂²⁻ (2n−2)S²⁻.