Reactor Choice for Maximizing Yields and Selectivities

In reactions where the product does not react further (i.e., parallel reactions), yields and selectivities can be easily calculated from the ratios of the rates. Where a product reacts further, no such simple analysis is possible, and resort to numerical solution is often necessary. As a general rule, however, whenever an intermediate product is the desired product, PFR is the preferred reactor. 

The questions now are What type of reactor would be best suited for a given parallel scheme Is the choice to be made on the basis of conversion or yield The answers to these questions depend largely on the nature of the Fp versus A] curve and whether A can be separated from the product and recycled at a 

Choice of reactor becomes relatively easy if the orders of the two reactions of scheme 11.4 are known. If reaction 1 is first order and 2 is second order in A, 

Where the orders of the two steps are the same, it is clear that the yield would be the same irrespective of the concentration profiles within the reactor, since any profile would have identical effects on the two reactions. The yield and selectivity for any situation would be given by 

One of the reactants undergoes a second reaction Let us now consider the scheme 

---