SEMISEQ - Sequential-Parallel Reactions in a Semi-Continuous Reactor

2 SEMISEQ - Sequential-Parallel Reactions in a Semi-Continuous Reactor 

A complex reaction is run in a semi-batch reactor with the purpose of improving the selectivity for the desired product P, compared to that of the waste Q. The kinetics are sequential with respect to components A, P and Q but are parallel with respect to B, The relative magnitudes of the orders of the two reactions determine the optimal feeding policy. 

The total material balance under constant density conditions is 

The relative magnitudes of the orders of reaction, nei and nB2, determine whether the concentration Cb in the reactor should be maintained high or low. The total reaction time must be adjusted such that product P is obtained at its maximum concentration, and this will also influence how B should be fed to the reactor. 

If the feeding rate is high the maximum reactor volume may be reached, which will cause the feeding rate of B to stop. The reaction then continues batchwise until the simulation is stopped. In the program the reaction orders are set as n j=np2 and nBi nB2. The selectivity for the desired product will be highest at the lowest feeding rates, since the desired reaction is then promoted by low concentrations of B. 

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