Design of Experiments and Model Discrimination

The most import consideration is the design of the reactor that is used to collect kinetic data. A CSTR (called a chemostat in the biological field) is ideal because a significant volume is at a uniform composition and temperature and gives a significant extent of reaction so that chemical analysis is easy. Operation at steady state allows measurements to be repeated, further improving experimental accuracy. 

Continuous flow stirred tank reactors are wonderful for kinetic experiments since they allow a direct determination of the reaction rate at known concentrations of the reactants. One other type of reactor allows this in principle. Dijferential reactors have such a small volume that concentrations and temperatures do not change appreciably from their inlet values. However, the small change in concentration makes it very hard to determine an accurate rate. The use of differential reactors is akin to numerical differentiation and is not recommended. If a CSTR cannot be used, a batch or piston flow reactor is preferred over a differential reactor even though the reaction rate is not measured directly but must be inferred from measured outlet concentrations. See also Sections 4.3.3 and 4.5.3, which describe a common technique for converting a differential reactor to a CSTR through the use of recycle. 

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