Infrared study of the adsorption of sulphur compounds on silica and silica-supported nickel

Abstract

Hydrogen bonding interactions between isolated hydroxyl groups on silica and adsorbed hydrogen sulphide, n-propyl mercaptan, dimethyl sulphide and thiophene molecules have been detected by infrared spectroscopy. Chemisorption of n-propyl mercaptan and dimethyl sulphide on silica primarily involved reaction of adsorbate molecules with strained siloxane bridges in the oxide surface. Thiophene was slowly chemisorbed on silica to give surface species, infrared spectra of which showed no evidence for unsaturation. The formation of the species involved slow exchange of hydrogen atoms between thiophene molecules and surface hydroxyl groups. Adsorption of carbonyl sulphide on silica could not be detected by infrared spectroscopy.

Infrared spectra of n-propyl mercaptan and thiophene on nickel/silica resembled the corresponding spectra for the adsorbates on silica alone. No infrared bands due to surface species formed from hydrogen sulphide or carbonyl sulphide on nickel were detected. Dimethyl sulphide was predominantly associatively chemisorbed on nickel although some dissociative adsorption to give species containing CH2 groups may also have taken place.