Syntheses with complete conversion the semi-batch reactor

Syntheses with complete conversion the semi-batch reactor 

Often the kinetics of the side reactions are not known. But in any case we need a complete reaction scheme, indicating what reactions take place, and preferably a qualitative indication of the reaction orders. From this follows which reactant has to be used in excess, and which has to be put into the reactor first. Usually this is the same reactant. When the kinetics of the main reaction and the possible side reactions are known, exact concentration profiles (in time) can be computed. In sections 3.2.2 and 3.4.2 - 3.4.4 some relevant principles were presented. From these calculations an optimum feeding programme can be found. 

Two cases will be discussed relatively slow reactions and very rapid reactions. 

Let us consider an imaginary example of a synthesis, where one undesired side reaction takes place (of the competitive type). These reactions are represented by the following reaction scheme  

The reaction is carried out in a solvent S, that also acts as a catalyst for the main reaction. P is the desired product Q is the accompanying byproduct, X is a unwanted byproduct. We wish to have complete conversion of B and the lowest possible pri uction of X. (Note that the letters are used as in section 3.2.2, but not as in section 3.4). The obvious choice is to use a high concentration and a certain excess of reactant A see figure 3.4. 

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