Dynamic Models and Chemisorption Mechanisms

From the mass balance equation (4.49) we can obtain the unsteady-state equations for a dynamic model by using an accumulation term as follows. 

Differentiation of ua in equation (4.54) with respect to time t gives us 

Thus we have obtained a differential equation in which two variables, Ca and Cas, are functions of time. To solve for these coupled functions, either we have to find a simple relation between Ca and Cas, or we need to develop an additional differential equation for CAs- 

We will follow the first path and build on the following physically justified details regarding the relation between Ca and Cas- We consider the chemisorption step of the gas-solid catalytic reaction A — D as follows  

Considering low concentrations of Ca, he., a linear relation between Ca and Cas, we obtain 

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