CARBON MONOXIDE OXIDATION WITH AN OXYGEN TRACER OVER A VANADIUM PENTOXIDE CATALYST

The oxidation reaction of carbon monoxide with gaseous oxygen on a powdered V2O5 catalyst was studied over the temperature range from 345 to 410°, using heavy oxygen 18O (about 3 atom %) as the tracer. When the lattice oxygen of the catalyst was partially substituted by concentrated heavy oxygen before the experiment, the percentage of 18O in the produced carbon dioxide changed gradually during the oxidation, in accordance with the 18O concentration in the catalyst, even though the percentage of 18O in oxygen and in carbon monoxide was practically invariant. When a mixture of oxygen and carbon dioxide, both containing about 60 atom % of 18O, was brought into contact with the catalyst at 370°, only the oxygen in carbon dioxide was found to be exchangeable with the lattice oxygen. The exchange rate of carbon dioxide was increased by the presence of carbon monoxide. The oxidation of carbon monoxide on vanadium pentoxide was explained by the oxidation-reduction mechanism. The relative rate of each elementary step and the surface intermediates during the reaction are discussed, and a detailed reaction scheme is proposed.