High temperature measurements on solid and gaseous sulphide systems

Abstract

An electrochemical cell (I), based on the oxygen ion conductor calcia-stabilized zirconia, has been designed to measure the equilibrium partial pressures of sulphur in H 2-H 2S gas mixtures: Pt, H 2, H 2S|CaO|ZrO 2-CaO|air, Pt(I). An auxiliary electrode of CaO allows the conversion of the H 2-H 2S gas mixture to a corresponding H 2-H 2O gas mixture via: CaO+H 2S→CaS+H 2O. The resultant EMF can subsequently be related to the H 2S content of the test gas mixture. Data were obtained over the ranges of 1000–1400 K and 10–1000 ppm H 2S in H 2. Galvanic cells of the type: Pt, Cu, Cu 2S, CaS|ZrO 2-CaO|CaS, M, MS, Pt (II) have been employed to determine the Gibbs free energy of formation of transition metal sulphides, MS, where M=Fe, Mn. ΔG 0 f(MnS)=−274.8+0.0620 T±0.500 kJ/mol (950–1250 K); ΔG 0 f(FeS)=−158.7+0.0458 T±1.1 kJ/mol (800–1200 K). Results are in reasonable agreement with data reported in the literature. The design of a micro integrated thin film sensor for SO 2/SO 3 based on a sulphate solid electrolyte is described. The advantages of fabrication of a sensor utilizing thin film technology are discussed.