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(0.9037, 0.0963)

(0.6875, 0.3125)

(0.73, 0.27) HAc/BuOH/BuAc 121.58 °C (0.4181, 0.2396, 0.3423)

HAc/BuOH 123.21 °C (0.5359, 0.4641)

H Ac/AmOH 140.07 °C (0.2585, 0.7415)

Heteroazeotropes are in bold, and experimental data of Horsley8 are in italic.

Heteroazeotropes are in bold, and experimental data of Horsley8 are in italic.

(100.02

(100.02

HAc (118.01 °c)

Figure 7.1 Azeotropes and two-liquid zone for five quaternary systems for acetic acid esterification: MeAc, EtAc, IP Ac, BuAc, and AmAc.

model parameters give a reasonably good description of existing experimental azeotropic data8 for all five systems. Moreover, the models also predict ternary azeotropes for four quaternary systems except the MeAc system (Table 7.3).

The phase equilibria results reveal that the MeAc quaternary system has two minimum boiling binary azeotropes (Fig. 7.1a), and this is the only system without any ternary azeotrope. For the EtAc and IPAc quaternary systems, the models predict three minimum boiling azeotropes and one minimum boiling ternary azeotrope (Figs. 7.1b and 7.1c). The BuAc quaternary system has three minimum boiling and one maximum boiling binary azeotropes and two ternary azeotropes (Fig. 7.1d), and the AmAc system gives three minimum boiling binary azeotropes and two ternary azeotropes (Fig. 7.1e). It is important to note that, for the EtAc, IPAc, BuAc, AmAc systems, the minimum temperature in the composition space is the ternary minimum boiling azeotrope. Significant LL envelopes are also observed for these five quaternary systems, especially for the acid-free ternary systems (Fig. 7.1). The MeAc, EtAc, and IPAc systems show type I LL envelopes and the BuAc and AmAc systems give type II envelopes as shown in Figure 7.1. The tie lines slope into the pure water node, and it becomes more evident as the carbon number in the alcohol increases. This means that relatively pure water can be recovered from the LL separation for four out of the five systems (except the MeAc system) and the separation (for achieving high purity water) becomes easier as the carbon number in the alcohol increases. For the EtAc system, the ternary minimum boiling azeotrope lies close to the edge of the LL envelope. For the IPAc, BuAc, and AmAc systems, the ternary minimum boiling azeotrope lies inside the LL envelope and it moves further inside the LL zone as the carbon number increases. As will be shown later, this has important implications in flowsheet development.

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