Kinetics of the Isotopic Exchange Reaction Between Carbon Monoxide and Carbon Dioxide

Abstract

The rate of exchange of the C¹³ isotope between carbon monoxide and carbon dioxide has been studied. It has been found to be a surface catalyzed reaction on quartz, gold, and silver surfaces. Within the limits of experimental error, which are rather large because of change of surface activity, the reaction is independent of pressure and composition of the gas mixture. The exchange is accelerated by hydrogen or water vapor. Oxygen produces a rapid initial exchange attributed to a chain process of oxidation of carbon monoxide, but is without effect on the subsequent exchange. Isotope exchange takes place with a velocity convenient for study around 900°C, and at this temperature the apparent energy of activation is about 100 kcal. Several mechanisms for the exchange of C¹³ have been examined. One which is not entirely free of difficulties accounts for the experimental data. This assumes the presence of H and OH molecules (or other activated forms of H₂ and H₂O) on the surface with the condition that the total amounts of these molecules is constant.