Electrode Potential of a Dispersed Raney Nickel Electrode During Acetone Hydrogenation: Influence of the Solution and Reaction Kinetics

The hydrogenation of acetone was investigated in basic aqueous solutions with undoped and chromium-doped catalysts. The reaction was carried out under pressure in an autoclave equipped with a reference electrode. The consumption of hydrogen and the electrode potential were measured during the course of the reaction. A mathematical model was applied which fits the experimental kinetic data well. It allows the computation of the rate constant and the adsorption equilibrium constants. The kinetics obey a Langmuir-Hinshelwood mechanism with competitive adsorption. The metallic catalyst particles behave like a dispersed electrode and an electrochemical double layer is formed at their surface. In the presence of hydrogen alone, the metal potential obeys the Nernst law for the hydrogen electrode. During acetone hydrogenation, the double layer is modified and the measured potential goes to the positive region for several tens of millivolts, depending on whether the catalyst is doped or not. In all cases an experimental correlation was found between this experimental potential rise and the reaction rate.