Ternary mixtures separation regions

The overwhelming majority of all ternary mixtures that can potentially exist are represented by only 113 different residue curve maps (35). Reference 24 contains sketches of 87 of these maps. For each type of separation objective, these 113 maps can be subdivided into those that can potentially meet the objective, ie, residue curve maps where the desired pure component and/or azeotropic products He in the same distillation region, and those that carmot. Thus knowing the residue curve for the mixture to be separated is sufficient to determine if a given separation objective is feasible, but not whether the objective can be achieved economically. 

E.xample problems are included to highlight the need to estimate the entire set of products that can be reached for a given feed when using a particular type of separation unit. We show that readily computed distillation curves and pinch point cur es allow us to identify the entire reachable region for simple and e.xtractive distillation for ternary mixtures. This analysis proves that finite reflux often permits increased separation we can compute exactly how far we can cross so-called distillation boundaries. For extractive distillation, we illustrate how to find minimum. solvent rates, minimum reflux ratios, and, interestingly, ma.xinnim reflux ratios. 

Figure 8.31 Ternary diagram showing complex coacervation region for mixtures of gum arabic and gelatin at pH 4.5 below the curved line the mixture separates into two sols (US Patent 2800457). Insert Typical droplets formed by coacervation (Ronald T. Dodge).

Because of its more extended aromatic system naphthalene is expected to be more acidic than benzene, but the difference is hardly observed in synthetic experiments. Treatment of naphthalene with BuLi TMEDA in hexane results in the formation of comparable amounts of the 1- and 2-lithio compounds and a dilithio derivative (possibly 1,8-) so that this method is not interesting from a synthetic point of view. If the metallation is carried out with the ternary mixture BuLi f-BuOK, TMEDA in hexane at temperatures in the region of — 20 °C, subsequent addition of dimethyl disulfide affords a mixture of 1-methylthio-, 2-methylthio- and l,8-bis(methyl-thio)naphthalene. The mono- and disubstitution products can be separated by distillation. The favourable ratio of about 15 85, together with the fact that the 2-isomer is solid at room temperature (whereas the 1-isomer is a liquid), permits an easy purification of the predominant product by crystallization. For practical reasons (difficult separation from the products) the use of an excess of naphthalene is avoided (compare the metallation of benzene, Exp. 3), and consequently yields (based on BuLi) are not optimal, since part of the base may react with TMEDA. 

Stichlmair, J., J.R. Fair, J. L. Bravo, 1989, Separation of azeotropic mixture via enhanced distillation, Chem. Eng. Progress, 85(1), 63-69 Stichlmair, J., J. R. Herguijuela, 1992, Separation regions and processes of zeotropic and azeotropic ternary distillation, AIChEJ, 38, p. 1523-1535 Stichlmair, J. G., J. R. Fair, 1999, Distillation, Principles and Practice, Willey-VCH Strathmann, H., 1990, Membrane and Membrane Separation Processes, Ullmann s Encyclopaedia of Industrial Chemistry, vol. A16 Taylor, R., Krishna, R., 2000, Modelling reactive distillation, Chem. Eng. Sci., 52, 993-1005... 

Figure 9.9 Separation regions for a ternary zeotropic mixture...

In the case of a liquid-liquid extraction operation, the solvent L must be chosen such that it is very miscible with the solute of the original binary mixture T/S yet immiscible with the carrier liquid T. Simple extraction processes for a common type of ternary mixture with components T, L, and S are presented in Fig. l-Il. A vapor phase and two liquid phases (in the two phase region) coexist in the heterogeneous system. S is completely soluble in T and L. In the area between A and B, T and L are insoluble in each other. The binary mixture of A and B, according to point M, will separate into two liquid phases of compositions A and B corresponding to the mass ratio AM/MB. 

Let at sides 1-2 and 2-3 of the concentration triangle be a region of order of components RegJ. Is it possible to use extractive distillation to separate this ternary mixture Wiich component can be the entrainer The top product ... 

For extraction, the extracting agent (C) is added to a binary mixture (E). The ternary mixture is represented by a point within the triangle (e.g., D in Figure 3.3.34a). For extraction, this point must lie in the two-phase region that is separated from the... 

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