tems. Most recent papers dealing with this subject were written on the butyl acetate esterification system and only mentioned phase-splitting behavior as a side phenomenon [14-16]. Westerberg et al. [17] published a survey of the possible combinations of many phenomena including the three involved in this case, but they did not deal in detail with the occurrence of liquid-phase splitting in RD. Gumus and Ciric [18] specifically tried to simulate such a system. Their focus was on the simultaneous reaction/distillation/phase splitting behavior because its prediction is computation-time intensive so that it is ideally suited to show the efficiency of a new numerical algorithm. Recently, Qi et al. [19] developed a model for studying the effects of chemical kinetics on the residue curve maps of pseudohomogeneous and heterogeneous reactive mixtures. The kinetic effects in the two kinds of systems were compared. The special case in which the chemical reaction only occurs in one of the two liquid phases inside the L-L region was also taken into account. As reaction system of technical relevance, these authors considered the liquidphase hydration of cyclohexene and water to form cyclohexanol

cyclohexene +H20 ^ cyclohexanol (5-42)

For this reaction system, the liquid-phase non-ideality can be described by the UNIFAC activity coefficient model [20]. Panneman and Beenackers [21] studied the reaction kinetics of (5.42) catalyzed by macroporous strongly acidic ion-exchange resins. Based on their results, Qi et al. [19] proposed an activity-based reaction rate expression for this reaction with the equilibrium constant and the forward rate constant as functions of temperature

The pseudohomogeneous chemical equilibrium (PCE) for the cyclohexanol reaction system is illustrated in Fig. 5.21a and the non-reactive isobaric L-L phase diagram is plotted in Fig. 5.21b. The raffinate phase is very close to the pure water vertex (see enlarged view in the right block). The two L-L envelopes intersect the PCE at two points * = (0.3466, 0.1840) and * = (0.0003, 0.9969). The two parts of the PCE outside the L-L region and the so called 'unique reactive liquid-liquid tie line' [19] comprise the heterogeneous chemical equilibrium line (HCE), which is the bold line in Fig. 5.21b.

Chemical Equilibrium

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