Acetone residue curve

Fig. 5. The acetone—2-propanol—water system where I represents the 2-propanol—water azeotrope, (a) Residue curve map (34) (b) material balance lines...

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

FIG. 13-73 Residue curve maps for acetone-methanol systems, (a) With water, (h) With MIPK. 

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...

The boundary is curved. This, too, can be partially predicted by noting that the infinite-dilution A -values for acetone and chloroform in lots of benzene indicate that acetone is more volatile. Therefore, chloroform acts like an intermediate species in the benzene-rich end of the diagram. The residue curves start out aiming at chloroform from benzene. 

Fig. 25, Residue curve diagram for acetone/chloroform/benzene mixture. A residue curve boundary passes from the maximum-boiling azeotrope between acetone and chloroform to pure benzene.

Examine Fig. 60. We show the residue curves that have the same S-shape as those in the lower left part of the right-hand-side region for acetone, chloroform, and benzene. Each curve is convex to the left at the top (curves toward the left) and convex to the right at the bottom, and each switches the direction it curves at its inflection point. Point a is such an inflection point on one of these residue curves. Draw a straight line through point a such that it has the same slope as the residue curve. Above the inflection point, this straight line is entirely to the right of the residue curve, and below it is entirely to the left. 

Figure 9.4 displays RCMs for some typical azeotropic mixtures. Figure 9.4a presents the mixture acetone (56.2 °C) / benzene (80.1 °C) / heptane (98.4 °C). Acetone and heptane form a minimum boiling azeotrope with nbp of 55.1 °C, which is the lowest boiler. It may be observed that the residue curves emanate from the azeotropic point, take the direction to the benzene/heptane edge, and then deflect to the heptane vertex. Binary azeotrope and heptane are unstable and stable nodes, respectively. Acetone and benzene are saddles. In this case there is a single distillation region, as for zeotropic mixtures, but the shape of the residue curves is peculiar. 

Figure 9.4b displays the RCM for the mixture acetone (562 °C) / chloroform (61.2 °C) / toluene (110.8 °C). The first two components give a maximum-azeotrope (nbp 64.7 °C), but boiling lower than toluene. There are two unstable nodes (acetone and chloroform), one stable node (toluene), and a saddle (azeotrope acetone-chloroform). The residue curves can emanate either from the acetone or from the chloroform vertices, but all terminate in the toluene vertex. The direction of trajectories shows clearly the separation of the... 

FK>URE 23 A residue curve map for (a) a constant relative volali Iky system widi a = [5, 1 ] and (b) die nonideal acetone/benzene/chlorofonn system using the NRTL model atP= atm. 

This plot allows one to identify nodes from a different perspective. Rather than tracking the origin, direction, and termination of residue curves, one can now analyze the temperature contours to classify nodes. For the system at hand, the lowest temperature is observed at pure acetone, while the highest is at pure benzene. Also, the binary azeotrope is a maximum-boiling binary azeotrope between acetone and chloroform, and this is the point of highest temperature along that binary boundary (horizontal boundary of MET). However, this temperature is still lower... 

FKvURK 2.17 Entire residue curve maps for (a) a constant relative volatility stem with a = [5,1 and (b) the nonideal acetone/benzene/chloroform system using die NRTL model at... 

FKjURK 2.18 Entire residue curve map for the nonideal acetone/ethanol/methanol system (with numbered nodes) using the NRTL model 3t P = atm. 

FKjURE 3.22 Pinch point loci produced by tangent conditions between and arbitrarily chosen and the residue curves. The RCM for the system is given, with the tangent lines di layed as dashed lines. The pinch point loci are drawn by connecting all tangent points for the (a) benzene/p xylene/toluene system, and (b) acetone/benzene/chloroform system. 

This method is simple and easy to use, and all that is required is the RCM for the system in question. However, the accuracy of the method depends on the number of residue curves used. Of course, the same method can be used directly to locate pinch point loci outside the MET, as is done in the example in Figure 3.22b for the acetone/benzene/chloroform system at 1 atm. Thus, by understanding the graphical nature of the DPE, one is able to gather a plethora of information, and many insights can be gained from this. 

M Fora mixture of 70 mol% chloroform, 15 mol% acetone, d 15 mol% ethanol at 1 atm, show on a residue curve map the fatible compositions of the distillate and bottoms product. 

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