Reduction of sulfate species by H2S on different metal oxides and promoted aluminas

Sulfate species formed by heating SO2 in excess of O-2 at 723 K on TiO2, ZrO2, Al2O3 and Al2O3 promoted by Fe, Cu, Ni, Mo, W or V were studied by FT-IR spectroscopy. The presence of Ni, Cu or Fe enhance sulfate formation on the alumina support. The sulfated samples were then heated under H2S at different temperatures. It was found that sulfate species on TiO2 and ZrO2 were much more easily reduced than those on alumina. The presence of promoting elements on alumina increased the sulfate reducibility. CS2 hydrolysis was also performed at 593 K, on pure and promoted aluminas. Under flow of CS2+H2O, alumina was more active than Cu/Al2O3 and Fe/Al2O3. However, in more realistic conditions, e.g. in presence of SO2 and/or O-2, addition of H2S to the flow maintained the activity of Cu and Fe doped catalysts with time-on-stream whereas that of pure Al2O3 drastically decreased, in agreement with H2S sulfates reduction results. The inactivity of Mo, W or V/Al2O3 samples toward CS2 hydrolysis was explained involving the acidity induced by these promoters. (C) 2000 Elsevier Science B.V. All rights reserved.