Oxidation of Palladium during the Olefin Oxidation over Palladium Salts-Active Charcoal Catalysts

Abstract

Oxidation of reduced palladium on active charcoal during the ethylene oxidation over palladium salts-active charcoal catalysts was studied. Effect of oxygen pressure on the reaction rate was determined from the rate of oxygen adsorption using the apparatus with constant volume and constant pressure equipment. Effect of oxygen pressure became evident only when its value was very little.
If we assume that the over-all reaction rate is determined in terms of the dynamic equilibrium between the oxidation of ethylene by palladium salts and the re-oxidation of reduced palladium compounds by oxygen, the conclusion, that the rate of re-oxidation is represented by the equation (01), can be derived from the analysis of experimental results, where K is the dissociative adsorption constant of oxygen. This suggests that the reduced palladium is oxidized by oxygen which is dissociatively adsorbed on active charcoal.
In the equation (01), κ2√K which is the measure of the re-oxidation activity, was found to vary with temperature, ethylene pressure and anions. The order of re-oxidation activity of palladium salts was Pd(NO₃)2>PdCl2>PdSO₄ under the same reaction condition.