Flue gas desulphurisation: Catalytic removal of sulphur dioxide by carbon monoxide on sulphided La 1− xSr xCoO 3: I. Adsorption of sulphur dioxide, carbon monoxide and their mixtures

Abstract

Temperature-programmed desorption mass spectrometry (TPD-MS) and thermogravimetric analysis of freeze-dried La 1− x Sr x CoO 3 ( x=0.3, 0.5, 0.6, 0.7) on exposure to sulphur dioxide and carbon monoxide was performed for the gases alone and their mixtures. The theory of TPD-MS is presented and the method used to determine activation energies of desorption. The ease of oxygen loss from the catalysts heated in vacuo to 650°C increased with x. Subsequent adsorption of carbon monoxide leads to a further mass loss for x=0.3 but a gain in mass occurs for x=0.7 suggesting strong adsorption at oxygen vacancies. Mass increases were recorded for the adsorption and reaction of sulphur dioxide at 500°C that increased with lanthanum content. Exposure to mixtures of sulphur dioxide and carbon monoxide were accompanied by reaction yielding elemental sulphur, carbonyl sulphide and great increases of mass of the catalyst. The X-ray diffraction patterns of the catalysts after adsorption of carbon monoxide at 500°C showed little change from the perovskite structure. However a mixture of sulphates and sulphides in addition to the underlying perovskite were found after exposure to sulphur dioxide, and for exposure to both gases the original structure was lost and replaced by a mixture of sulphides and oxosulphides of the metals. No perovskite sulphides were detected.