Dependence of the Exchange Reaction Rate in Catalyst Bed upon the Rate of Feed Gases and the Length of the Bed

Abstract

Abstract (1) Exchange reaction has the prominent feature that the rate does not change with the progress of the reaction and can be determined only by the mechanism of the reaction. Therefore we can immediately detect the effect of variation in any one of the reacting conditions by the observed conversion of the isotopic exchange reaction. (2) The relation between exchange reaction and isotopic exchange reaction is considered and an equation which gives the exchange reaction rate (R) using the integral conversion of the isotopic exchange reaction (x) is introduced. (3) The method is applied to the exchange reaction of oxygen atoms between gaseous oxygen and water vapor catalyzed by chromic oxide, and examination is made of the effect of the variation in the rate of feed gases and in the length of the catalyst bed. (4) At feed rates higher than 32.0 cc. (S. C.)/sec. cm2 the value R remains almost constant, but by the lowering of the feed rate more than this and by the shortening of the bed length, R is decreased. This decrease accompanied decreases both in activation energy and in frequency factor. (5) The results are explained by the effects of mass-transfer through the gas film, of eddy or diffusional mixing of the reacting gases and of other kinds of disturbances. Masstransfer resistance of the gas film is a small fraction of the retardation. Mixing of the reacting gases may contribute a higher percent. (6) The results are compared with the rate of exchange between hydrogen and deuterium measured by Holm and Blue.