Ethylene oxidation to acetic acid with Pd-V2O5 type catalysts I. Gas-solid reactions

Palladium added to V2O5 enhances the reducibility of this oxide. The reduction can then be performed at low temperature so as to produce selectively a reduced phase with the formula V4O9. The influence of ethylene partial pressure on the initial reduction rate of Pd-V2O5 and the influence of oxygen partial pressure on the initial oxidation rate of the reduced phase have been established. Kinetic equations are proposed for these two gas-solid reactions. The selective formation of acetaldehyde and acetic acid occurs during the reduction. In the presence of both ethylene and oxygen reactants, i.e., for the condition of catalytic reaction, we observe a change of the initial composition of the solid toward a final state which depends on the partial pressure of the reactants. Qualitatively, from an initially oxidized form, there is a partial reduction, while from an initially reduced form, V4O9, there is a partial oxidation.