Azeotrope maximum boiling-point type

Two types of azeotrope, maximum boiling point (Figure 3.9(a)) and minimum boiling point (Figure 3.9(b)), can be represented on this type of diagram. 

Figure 9.16 Different types of liquid-vapor phase diagrams for a binary liquid mixture of component A and B as functions of the mole fraction of the component with the higher boiling temperature, (a) The phase diagram for a system with a low-boiling azeotrope (minimum boiling point) and (b) the phase diagram for a system with a high-boiling azeotrope (maximum boiling point). The arrows show how the paths for various distillation processes depend upon the position of the initial composition relative to the azeotrope.

III also crosses the 45 line but curve II cuts the 45 line with the slope less than 1 while curve III crosses the 45 line with the slope greater than 1. Curve III is of the maximum boiling-point type, and the particular composition at which the curve crosses the 45 line is called a maximum constant boiling mixture or a maximum boiling azeotrope. 

Figure 8.9d is practically the vertical mirror image of Figure 8.8d. It shows that this system has a maximum boiling point, and two regions with different behaviors on either side of the liquid composition at which that maximum occurs. This type of azeotrope is less common than minimum boiling azeotropes, but it also makes separation by distillation difficult. If we start with a mixture to the left of the azeotrope in...

In the systems that we have examined so far, the bubble point and the dew point of the mixture vary monotonically with the composition. This is the case for ideal systems. However, for very non-ideal systems, there may be a maximum or a minimum in the bubble and dew point curves. This is the case for azeotropic systems. An example of a system that exhibits a low-boiling azeotrope is a mixture of 77-heptane and ethanol, which is shown in Figure 3.5. For this type of system, both the bubble and dew point temperature curves have a local minimum at the same composition. At this composition, these two curves meet. This point is known as the azeotrope. At the azeotrope, the composition of the coexisting liquid and vapor phases are identical. In this case at the azeotrope, the boiling temperature... 

The results of the studies on separating minimum and maximum boiling azeotropes with light, intermediate, or heavy entrainers are compared according to their operation steps and feasibility domains. The decisive property for designing an effective BED process, separating azeotropes, is the relative position of the entrainer to the azeotrope in the bubble point series. But the type of the azeotrope (minimum or maximum) can modify the existence of some limiting parameters (FA a , N,., >.,). 

Binary homogeneous (single-phase) liquid mixtures having an extremum (maximum or minimum) vapor pressure P at constant temperature T, as a function of composition, are called azeotropic mixtures, or simply azeotropes. The composition is usually expressed as mole fractions, where for component 1 in the liquid phase and i for component 1 in the vapor phase are identical. Mixtures that do not show a maximum or minimum are called zeotropic. A maximum (minimum) of the P xi) or P(yi) curves corresponds to a minimum (maximum) of the boiling temperature T at constant P, plotted as a function of. Vj or yi [see T xj) and T(yi) curves. Types 1 and 111, in Fig.l]. Azeotropes in which the pressure is a maximum (temperature is a minimum) are often called positive azeotropes, while pressure-minimum (temperature-maximum) azeotropes are called negative azeotropes. The coordinates of an azeotropic point are the azeotropic temperature Taz> pressure arid the vapor-phase composition, which is the same as the liquid-phase composition... 

---