Infrared studies of the adsorption and surface reactions of hydrogen sulfide and sulfur dioxide on some aluminas and zeolites

Abstract

Adsorption of hydrogen sulfide, sulfur dioxide, and their mixtures on four different catalysts has been studied by infrared spectroscopy of the catalyst surfaces. The four catalysts, which show a wide range of acidity and are all active for the Claus reaction (2H 2S + SO 2 → 3S + 2H 2O), were γ-alumina (the main constituent of commercial bauxite catalysts), γ-alumina doped with NaOH, sodium Y zeolite, and hydrogen Y zeolite. All catalysts showed physical adsorption of both reactants with strong hydrogen bonding to surface OH groups. This would suggest that the role of the catalyst is primarily to bring the reactants together in suitable orientation. On the other hand, γ-alumina shows, on heating with SO 2, a chemisorbed SO 2 species which may be a reaction intermediate. The NaOH-treated γ-alumina shows a second chemisorbed SO 2 species which is irreversibly adsorbed and thus may be a catalyst poison.