Influence of oxygen on activity of Pd-Fe/α-Al₂O₃ catalyst for CO coupling reaction to diethyl oxalate

The effect of different contents of O₂ (5-10%) in the raw gas on the activity of Pd-Fe/α-Al₂O₃ catalyst for CO coupling reaction to diethyl oxalate (DEO) was studied at 105° 120°C. The conversion of CO and the space time yield of DEO increased with increasing O₂ concentration and reaction temperature, but the selectivity for DEO decreased, and a new by-product, ethyl acetate, was formed in the reaction system with O₂. The O₂, whose concentration was not more than 10% in the reaction system, could not cause the deactivation of the Pd-containing catalyst but accelerated simultaneously the main reaction and the side-reaction of CO coupling. Oxygen, reacting rapidly with NO product of CO coupling reaction, made the decrease in concentration of the adsorbed NO on the catalyst surface, providing a more efficient space field for CO coupling main reaction and side-reaction. The activity and selectivity of the catalyst can be fully recovered after removing O₂ from the reaction system.