Selectivity and Optimization Considerations in the Design of Isothermal Reactors

Selectivity and Optimization Considerations in the Design of Isothermal Reactors 

For purposes of reactor design, the distinction between a single reaction and multiple reactions is made in terms of the number of extents of reaction necessary to describe the kinetic behavior of the system, the former requiring only one reaction progress variable. Because the presence of multiple reactions makes it impossible to characterize the product distribution in terms of a unique fraction conversion, we will find it most convenient to work in terms of species concentrations. Division of one rate expression by another will permit us to eliminate time as an explicit independent variable, thereby obtaining expressions that are convenient for examining the effects of changes in process variables on the product distribution. 

In discussions of systems in which only a single chemical reaction is involved, one may use the words yield and conversion as complementary terms. However, in dealing with multiple reactions, conversion refers to the proportion of a reagent that reacts, whereas yield refers to the amount of a specific product that is obtained. When a number of 

To avoid the possibility of obtaining yields in excess of 100%, it is necessary to employ stoichiometric coefficients to normalize one s calculations properly. It is also necessary to state whether the yield is computed relative to the amount of reactant introduced into the system or relative to the amount of reactant consumed. For example, for the reaction 

There are many industrial situations where reactor designers have opted for selective catalysts or reaction conditions even though they lead to low reactivity. Although large reactor volumes are required, the economics of these sitoations are more favorable than those leading to high reactivity but low selectivity. The latter situation is 

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