Selectivity mixed parallel-series networks

Derive the rate expression for this mixed-parallel series-reaction network and the expression for the percent selectivity to the epoxide. 

In Example 1.5.6, the expression for the maximum concentration in a series reaction network was illustrated. Example 1.5.8 showed how to determine the selectivity in a mixed-parallel series-reaction network. Calculate the maximum epoxide selectivity attained from the reaction network illustrated in Example 1.5.8 assuming an excess of dioxygen. 

Equation (19-22) indicates that, for a nominal 90 percent conversion, an ideal CSTR will need nearly 4 times the residence time (or volume) of a PFR. This result is also worth bearing in mind when batch reactor experiments are converted to a battery of ideal CSTRs in series in the field. The performance of a completely mixed batch reactor and a steady-state PFR having the same residence time is the same [Eqs. (19-5) and (19-19)]. At a given residence time, if a batch reactor provides a nominal 90 percent conversion for a first-order reaction, a single ideal CSTR will only provide a conversion of 70 percent. The above discussion addresses conversion. Product selectivity in complex reaction networks may be profoundly affected by dispersion. This aspect has been addressed from the standpoint of parallel and consecutive reaction networks in Sec. 7. 

In the previous chapter, we examined series and series-parallel kinetics. The extent of mixing can have an effect on the selectivity to the various products in such reaction networks. The selectivity is the percentage of the products that are any one of the products. To compute the yield we take the product of the conversion and the selectivity. Thus the yield is a fraction of a fraction. 

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