Ternary azeotropes chloroform

Schematic DRDs are particularly useful in determining the implications of possibly unknown ternary saddle azeotropes by postulating position 7 at interior positions in the temperature profile. Also note that some combinations of binary azeotropes require the existence of a ternary saddle azeotrope. As an example, consider the system acetone (56.4°C), chloroform (61.2°C), and methanol (64.7°C) at 1-atm pressure. Methanol forms minimum-boiling azeotropes with both acetone (54.6°C) and chloroform (53.5°C), and acetone-chloroform forms a maximum-boiling azeotrope (64.5°C). Experimentally there are no data for maximum- or minimum-boiling ternary azeotropes for this mixture. Assuming no ternary azeotrope, the temperature profile for this system is 461325, which from Table 13-18 is consistent with DRD 040 and DRD 042. However, Table 13-18 also indicates that the pure-component and binary azeotrope data are consistent with three temperature profiles involving a ternary saddle azeotrope, namely, 4671325, 4617325, and 4613725. All three of these temperature profiles correspond to DRD 107. Calculated residue curve trajectories for the acetone-chloroform-methanol system at 1-atm pressure, as...

Finally, Figure 9.4d illustrates a more complex situation, the mixture acetone/ chloroform/methanol, with four azeotropes (three binaries and one ternary). There are four distillation regions. Note that the ternary azeotrope is a saddle. 

Figure 9.6 shows the RCM for the mixture acetone/chloroform/methanol, for which the class is 311-S. The first digit represents the max-azeotrope acetone/chloroform, the second the minimum-azeotrope chloroform/methanol, the third the minimum-azeotrope acetone/methanol. The letter S signifies the ternary saddle azeotrope. More RCMs are presented in Perry (1997), from a total of 125 configurations. 

In addition to the binary azeotropes listed, chloroform enters into a number of ternary azeotropes that can interfere with its recovery (Table 16.10). 

Solvent recovery handbook Table 16.10 Ternary azeotropes of chloroform ... 

In a fortunate case, distillation aimed at purification may also result in the drying of the solvent. Distillation may be particularly effective in the removal of moisture if azeotropic mixtures with low boiling points are formed. For instance, the first step in the dehydration of ethanol is distillation after the addition of benzene, when water is removed in the volatile ternary azeotrope. Other solvents may also be dehydrated by distillation, e.g., benzene, chloroform, carbon tetrachloride, ethylene dichloride, heptane, hexane, toluene and xylene. In distillations with the aim of dehydration, the apparatus must be fitted with moisture traps (containing calcium chloride, silica gel or some other drying agent). It must be borne in mind that many anhydrous organic solvents are hygroscopic. 

FIG. 13-60 Residue curves for acetone-chloroform-methanol system suggesting a ternary saddle azeotrope. 

Figure 3.10 shows typical RCM for nonideal mixtures involving azeotropes. For the mixture ace tone/heptane /benzene (plot a) there is only one distillation field. The problem seems similar to a zeotropic system, except for the fact that the minimum boiler is a binary azeotrope and not a pure component. With the mixture acetone/chloroform/toluene (plot b) there is one distillation boundary linking the high-boiler with the low-boiler azeotrope. Consequently, there are two distillation regions. Similar behavior shows the plot c, with two azeotropes. The mixture acetone/chloroform/methanol (plotd) has four azeotropes (3 binaries and 1 ternary) displaying a behavior with four distillation regions. 

We predicted their behavior earlier using infinite-dilution /f-values, with the results at 1 atm shown in Table VIII. Only the acetone and chloroform appear to display azeotropic behavior. With this information and that for pure species boiling points at the pressure of interest, we can sketch the ternary diagram for this mixture. We can also use a computer code to generate it, which was done for Fig. 25. We see that there is one maximum-boiling azeotrope between acetone and chloroform. 

In a situation in which fractionating power is known to be barely adequate, the two solvents (DIPE and chloroform) with low-boiling binary azeotropes including water rather than ethanol have the advantage that it is positively helpful to have their water binaries admixed with the ternary in the decanter (Table 7.6). 

For modest-sized parcels of wet ACN, the need to dispose of the entrainer/ACN azeotropes after the recovery campaign may represent an unacceptable cost. Chloroform and methylene chloride both form binary water azeotropes without forming a ternary with ACN, but the former has the disadvantage of toxicity and the latter has a very low water-carrying capacity at a low condensing temperature. 

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