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-A model, of the adso,rption/desorption type, is used to examine the behavior of a catalytic reaction system during forced cycling of the feed composition. It is shown that this model can predict the occurrence of resonant behavior. This rate enhanment during periodic operation is due to the system being forced to operate for part of each cycle in a region where multiple operating states could potentially exist. It is also shown that both sine and square wave forcing functions produce resonant behavior, with the forcing frequency determining which type of function will produce the maximum rate In two recent publications, Feimer et al. [I] and Jain et al. [2] examined the behavior of several kinetic models which were subjected to periodic variation of the feed stream reactant compositions. These models were of the adsorption/desorption (AD) type, namely, only kinetic steps involving adsorption, surface reaction and desorption are included in the mechanisms. From these studies, the authors concluded that AD models cannot be used to predict rate improvement during periodic operation. Thus, these authors have stated that AD models are not useful for explaining the many experimental observations of rate enhancement