Distillation of partially miscible
liquids
Mariana Reyes Cortez
Edgar O. Hernández Saab
Alfredo Jiménez
CONCEPTS
 The immiscible liquids that dissolve in the median ratio are called "partially
miscible".
 Consider a pair of liquids that are partially miscible and form a low boiling
azeotrope (a common system, because both properties reflect the
tendency o the two kinds of molecules to avoid each other).
 Can’t be separated by simple distillation
Why do azotropic mixtures are form?
 Due to differences in intermolecular forces of attraction among the
mixture components (hydrogen bounding and others).
 The tendency of a mixture to form an azeotrope depends on two
factors: (i) the difference in the pure component boiling points, and
(ii) the degree of nonideality (Horsley, 1973; King, 1980).
 A heuristic rule is given in Perry and Chilton (1973) that azeotropes
occur frequently between compounds whose boiling points is less
than 30 °C.
 The presence of some specific groups, particularly polar groups
(oxygen, nitrogen, chlorine and fluorine), often results in the
formation of azeotropes.
Characteristics
 1. Positive deviation from Raoult’s law: The attraction between identical
molecules is stronger than between different molecules. This may cause the
formation of a minimum-boiling azeotrope and heterogeneity.
 2. Negative deviation from Raoult’s law: The attraction between different
molecules is the strongest. This may cause the formation of a maximumboiling azeotrope.
 3. Ideal mixture obeys Raoult’s law: The components have similar
physiochemical properties. The intermolecular forces between identical
and different molecules are equal.
EXAMPLE
EXAMPLE
 Water and ethanol form an azotropic
mixture, which means that cant be
completely separated, however you can
change the composition of the mixture by
adding Benzene as a separation agent, so
you can skip azotropic point and it can now
be separated.
 Other way to skip the azotropic point is
changing the pressure.
APLICACIONES
Environmental policies
as the entry into effect of the Month
September 2005, Act 693 of 2001
Ministry of Mines and Energy of
Colombia,
where it regulates the gasoline must
contain 10% by volume of ethanol,
which
technical limitations should possess a
very low water content.
Referencias:
 http://people.cst.cmich.edu/teckl1mm/PChemI/Chm351Ch8aF01.htm
 http://destilacionquimica.blogspot.mx/
 http://www.nt.ntnu.no/users/skoge/publications/thesis/2000_hilmen/Thesis_
Hilmen.pdf
 https://books.google.com.mx/books?id=dVGP7pmCh10C&pg=PA187&lpg
=PA187&dq=destilacion+de+liquidos+parcialmente+miscibles&source=bl&
ots=itEGs3UMIY&sig=KVwgdzE9OSxHS5vslWaxfjI2z3c&hl=es419&sa=X&ei=Fg80VYvbDcvRtQWU7oCwBg&ved=0CB8Q6AEwAQ#v=onep
age&q=destilacion%20de%20liquidos%20parcialmente%20miscibles&f=false