Bohart-Adams model

Wheeler and Robell [18] were the first to make use of the Bohart-Adams model which, as we have said, was developed for a fixed-bed adsorption problem. They used the adsorption model to establish the sluq)e and motion of the poison proffles (c.f Figure 1) within the bed and then essentially solved a reaction/deactivation problem based on these profiles (in their case a simple first order system). However, it was also necessary to specify how the reaction rate constant, k, varied with the concentration of poison on the catdyst. In the simplest case we can choose a linear relationship (nonselective poisoning) as they did and write... 

The equilibrium-dispersive model had been discussed and studied in the literature long before the formulation of the ideal model. Bohart and Adams [2] derived the equation of the model as early as 1920, but it does not seem that they attempted any calculations based on this model. Wicke [3,4] derived the mass balance equation of the model in 1939 and discussed its application to gas chromatography on activated charcoal. In this chapter, we describe the equilibrium-dispersive model, its historical development, the inherent assumptions, the input parameters required, the methods used for the calculation of solutions, and their characteristic features. In addition, some approximate analytical solutions of the equilibrium-dispersive model are presented. 

The similar model was first proposed by Bohart and Adams [128] for one component adsorption. It is widely used to describe the dynamics of adsorption when chemical reaction takes place. Equation (34) represents the differential mass balance for component i in a fixed bed adsorber with corresponding boundary conditions (Eq. (36) and (37)). At an initial time, t = 0, the bed is free from adsorbates and reaction products. Concentrations of adsorbates in a gas phase, Ci, and an adsorbed phase, qi, are equal to zero at any point of the bed. Inlet concentrations of each gas components are constant and equal to Coi, at any moment of time. 

Note With fi - I this expression reduces to the solution for a linear system given in Table 8.1, model la, while for = 0 it reduces to the form given by Bohart and Adams for an irreversible system. 

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