Butyl Acetate Thermodynamic Consistency

From a theoretical standpoint, it is obvious that only thermodynamic consistent models of chemical and phase equilibria should be applied in RD modeling. We will discuss the subject from a more practical standpoint here, using typical liquid-phase reactions as examples, for which the thermodynamic consistent chemical equilibrium constant is given by equations (4.12) and (4.13). 

The question of whether it is possible to predict the concentration dependence of from information on Ky via equation (4.22) is discussed here using the esterification of 1-butanol with acetic acid at 80 °C as an example. The experimental data given in Fig. 4.9 show that is a strong function of the composition for that liquid-phase reaction. The numbers for are in the range 2-8 and systematically vary with composition. In the studied system, there is a liquid-liquid miscibility gap intersecting with the chemical equilibrium surface. No measurements with liquid-liquid phase split were carried out in the present work. 

K = 22.7. Based on that single number, the activity coefficient model predicts the influence of concentration on via equation (4.22). It can be seen from Fig. 4.9 that the comparison of that prediction to the experimental data generally shows good agreement. Larger deviations are only observed for a few diluted samples and may partially be due to experimental errors. Results such as those shown in Fig. 4.9 are typical also for other esterifications. 

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Thermodynantics of Reactive Separations 81 4.4.2.3 Butyl Acetate Thermodynamic Consistency... 

Fig. 4.9 Concentration dependence of the mass action law equilibrium constant /C, of the reaction 1-butanol + acetic acid butyl acetate + water at 80 °C comparison of experimental data (this work) with predictions from a thermodynamic consistent model using activity coefficients from a NRTL model with parameters from phase equilibrium data K = 22.7)...

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