Phase-composition and selectivity: Solid electrolyte potentiometry aided study of the oxidation of propene on copper oxides

Abstract

It is commonly accepted in propene oxidation on copper oxide that it is partially oxidized to acrolein on Cu 2O but totally oxidized on CuO. It is therefore the reaction of choice to illustrate the usefulness of solid electrolyte potentiometry in the case of oxidic catalysts. In fact, the potentiometric determination of the oxygen activity in the catalyst under working conditions indicates the thermodynamically stable phase-composition, the selectivity measurements allow the experimental verification if the thermodynamically stable phase has really been formed. The combined kinetic and electrochemical study has been performed in a gradientless recirculation system in the temperature range 420<Θ/°C<510 at constant propene and varying oxygen partial pressures. The results show clearly that both the onset and the maximum rate of acrolein formation occur in the domain of oxygen activity where copper(I) oxide is thermodynamically stable.