Application of Oxygen Concentration Cells to Kinetic Study of Heterogeneous Reactions at Elevated Temperature

Abstract

An oxygen concentration cell with zirconia and lime electrolyte has two characteristics in its performance at elevated temperature; First, the cell shows good reversibility against the change of oxygen pressure and temperature at the interface of the solid electrolyte and the electronic-conductor electrode. Second, the response time of the electromotive force is very short against the change of oxygen pressure and temperature.The two characteristics have been applied to kinetic study of heterogeneous reactions at elevated temperature as follows:(1) Gas composition profiles in the vicinity of the reaction surface have been continuously measured during the decarburization of liquid iron by carbon dioxide gas at 1550°C. It was shown that there is concentration gradient of carbon dioxide in the vicinity of the reaction surface and the gas phase is in unstable motion under the present experimental condition.(2) Intraparticle gas composition of metal oxide powders has been continuously measured during the reduction by hydrogen gas and carbon monoxide gas. The change of the electromotive force demonstrated the step-wise change of the intraparticle gas composition in relation to the two intermediate phases equilibria.(3) The rate of the change of oxygen pressure in the liquid metal and liquid oxide phases has been measured, when the oxygen pressure in the gas phase is quickly changed.The micromechanism of the reactions under consideration was discussed from both results obtained by the electromotive force method and by other methods.