Dependence of the Isotopic Exchange Reaction Rate in Catalytic Bed upon the Rate of Feed Gases

Abstract

The rate of the exchange of oxygen atoms between gaseous oxygen and water vapor was examined under various conditions ranging between 487-598°C of temperature and 30.1-136.1cc/sec of feed rate. Cylindrical pellets of height and diameter each equal to 0.2cm were prepared from the mixture of 1:3 of chromic oxide and the Naegi kaolin, and packed in a silica tube of 1.6cm inside diameter by 23.5-24.0cm height. Random dense arrangement of the bed was measured by the pressure drop of the gas flowing through the tube.The relations between the logarithms of the total exchange reaction rate R and the reciprocal of the temperature T in °K are plotted in the Fig. 3. These plots are for convenience sake, divided into two classes, one belonging to the lower feed rate less than 48cc/sec and the other to the higher feed rate above 64cc/sec. The values of R in these two classes differ by the factor of about 1.3 at lower temperature and 1.6 at higher temperature. These differences are explained by the effects of mass-transfer of the gas film, of longitudinal diffusion of reactants and products, and of the pressure drop through the bed. Mass transfer resistance of the gas film is less than 3% of the overall reaction resistance under the restricted conditions of the experiments. Longitudinal diffusion may contribute a higher percent.These results are compared with the rate of exchange between hydrogen and deuterium measured by Holm and Blue. The effect of space velocity of the reacting gases on the rate of the exchange is more remarkable than that observed above.