Influence of Coking on the Selectivity

Coking may alter the selectivity when the different reactions have different deactivation functions (see Froment and Bischoff [13] and Weekman [21, 22, 23]). Weekman and Nace [24] represented the catalytic cracking of gasoil A) into gasoline (0, dry gas and coke (S) by the following equations  

In their study of -pentane isomeritation on a Pt/AljOs catalyst, to be discussed in more detail later, De Pauw and Froment [IS] found the main reaction to be accompanied by hydrocracking and coking. The latter two reactions were shown to occur on sites different from those involved in the main reaction. The three rates decayed through coking, but at different rates, so that the selectivity varied with time as shown in Fig. 5.3.C-2. 

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