8.3.1 Selectivity

In this section, we discuss various means of minimizing the undesired product, U, through the selection of reactor type and operating conditions. We also discuss the development of efficient reactor schemes.

For the competing reactions

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the rate laws are

8-6

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8-7

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Rate laws for formation of desired and undesired products

The net rate of disappearance of A for this reaction sequence is the sum of the rates of formation of U and D:

8-8

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8-9

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where α1 and α2 are positive reaction orders. We want the rate of formation of D, rD, to be high with respect to the rate of formation of U, rU. Taking the ratio of these rates [i.e., Equation (8-6) to Equation (8-7)], we obtain the instantaneous selectivity, SD/U, which is to be maximized:

8-10

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Instantaneous selectivity

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