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DMSO as an Entrainer to Separate a Water-Isopropyl Alcohol Mixture

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The binary mixture of water and isopropyl alcohol (isopropanol or propan-2-ol) presents a positive azeotrope at 1 atm. This azeotrope is labeled
A
in the ternary diagram and contains
69.8
mole % isopropanol. It is possible to break this azeotrope using extractive distillation. A list of entrainers includes: (1) 1,2-ethanediol or ethylene glycol, (2) DSMO (dimethyl sulfoxide), (3)
N
-methyl-2-pyrrolidone or NMP, (4)
N
-methyl-2-piperidone, and (5)
N
-methyl-6-caprolactam; see[1].
In this Demonstration, residue curves are computed for a ternary mixture composed of DSMO, water, and isopropanol. It is clear that (1) the high boiling DSMO is a stable node, (2) the azeotrope between water and isopropanol,
A
, is an unstable node, and (3) two pure components (water and isopropyl alcohol) are saddle points. It is possible to break the azeotrope between water and isopropanol,
A
, using DSMO as an entrainer, since it does not introduce new azeotropes and there is only one distillation region (i.e. there are no distillation boundaries that separate water and isopropyl alcohol).
You can change the vapor pressure constants, the molar volumes, and the Wilson model binary interaction parameters in order to check that all chemical components suggested in[1] are possible entrainers for the extractive distillation operation to separate water-isopropanol mixtures.

References

[1] J. Gmehling and C. Mollmann, "Synthesis of Distillation Process Using Thermodynamic Models and the Dortmund Data Bank," Industrial and Engineering Chemistry Research, 37(8), 1998 pp. 3112–3123.

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