Azeotrope heterogeneous minimum-boiling

FIG. 13-98 Flow sheet for making esters which form a heterogeneous minimum-boiling azeotrope with water. 

FIGURE 10.2 Separating heterogeneous minimum-boiling azeotropes. 

Figure 6-8 Boiling-point diagram for a heterogeneous minimum-boiling azeotrope. (M. Van Winkle, Distillation, 1967, by courtesy McGraw-Hill Book Company.)...

The formation of minimum-boiling mixtures makes azeotropic distillation a useful tool in those cases where separation by fractional distillation is not feasible. In the example cited for separation operation (10) in Table 1.1, n-butyl acetate, which forms a heterogeneous minimum-boiling azeotrope with water, is used to facilitate the separation of acetic acid from water. The azeotrope is taken overhead, the acetate and water layers are decanted, and the MSA is recirculated. 

The simplest case of combining T E and LLE is the separation of a binaiy heterogeneous azeotropic mixture. One example is the dehydration of 1-butanol, a self-entraining system, in which butanol (117.7°C) and water form a minimum-boiling heterogeneous azeotrope (93.0°C). As shown in Fig. 13-69, the fresh feed may be added... 

At atmospheric pressure, the n-butanol-water system exhibits a minimum boiling azeotrope and partial miscibility, and hence a binary heterogeneous azeotrope. Figure 1.8 shows the Tyx and Pyx phase diagrams for l-propanol(l)-water(2) azeotropic mixture obtained from the Aspen Plus simulator using the NRTL activity coefficient model. 

Example 1.17 Heterogeneous azeotrope The heterogeneous mixture -butanol( 1 )-water(2) exhibits a minimum boiling azeotrope. The temperature composition data at 1 atm is shown in Table 1.11. 

Ethanol-water Minimum-boiling azeotrope None Alternative to extractive distillation, salt extractive distillation, heterogeneous azeotropic distillation must reduce pressure to less than 11.5 kPa for azeotrope to disappear... 

An example of heterogeneous-azeotrope formation is shown in Fig. 13-13 for the water-normal butanol system at 101.3 kPa. At hquid compositions between 0 and 3 mole percent butanol and between 40 and 100 mole percent butanol, the liquid phase is homogeneous. Phase splitting into two separate liquid phases (one with 3 mole percent butanol and the other with 40 mole percent butanol) occurs for any overall liquid composition between 3 and 40 mole percent butanol. A minimum-boiling heterogeneous azeotrope occurs at 92°C (198°F) when the vapor composition and the overall composition of the two liquid phases are 75 mole percent butanol. 

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