Azeotropic distillation

This practice of adding an entrainer which forms a separate phase is a specific sub-set of (industrial) azeotropic distillation methods, or combination thereof.

The addition of a material separation agent, such as benzene to an ethanol/water mixture, changes the molecular interactions and eliminates the azeotrope.

Greater deviations from Raoult's law make it easier to achieve significant changes in relative volatility with the addition of another component.

The added entrainer should be recovered by distillation, decantation, or another separation method and returned near the top of the original column.

Several entrainers can be used for this specific process: benzene, pentane, cyclohexane, hexane, heptane, isooctane, acetone, and diethyl ether are all options as the mixture.

Phase diagram (left) and process flow diagram (right) of an apparatus for the azeotropic distillation with "material separation agent". In this case the phase diagram includes a zone where components are not miscible, so following the condensation of the azeotrope, it is possible to separate the liquid components through decantation .
Common Equipment used in Azeotropic Distillation
A Dean–Stark apparatus is used in azeotropic drying or dehydration processes: 1 stirrer bar/anti-bumping granules, 2 still pot, 3 fractionating column, 4 thermometer/boiling point temperature, 5 condenser, 6 cooling water in, 7 cooling water out, 8 burette, 9 tap, 10 collection vessel