Extractive and azeotropic distillation have the common feature that a substance
not normally present in the mixture to be separated is deliberately introduced into the
system in order to increase the difference in volatility of the most hard to separate
components. Extractive distillation can be defined as distillation in the presence of a
substance which is relatively non-volatile compared to the components to be separa-
ted, and which, therefore, is charged continuously near the top of the fractionating
tower, so that an appreciable concentration is maintained on all plates in the tower
below its entry. Azeotropic distillation can be defined as distillation in which the add-
ed substance forms an azeotrope with one or more of the components in the feed, and
by virtue of this are present on most of the plates in the tower above its entry at an
These separation methods find their principal applications in the separation of
mixtures whose components boil too close together for the economical use of simple
fractionating equipment. These separation methods are particularly applicable when
the components to be separated differ in chemical type. The theoretical principles in-
volved are well documented, and will not be further considered here. The processes
differ in the means used to maintain be desired solvent concentration on the plates of
the tower. In extractive distillation the high concentration of solvent is maintained by
virtue of its non-volatility, and by the fact that it is charged at a high point in the
tower. The solvent is, necessarily, removed from the base of the principal tower.
In azeotropic distillation, most of the solvent is taken off from overhead, with rela-
tively small amounts (ideally, none) drawn off with the bottoms.
Extractive distillation is generally more flexible than azeotropic distillation, a
greater variety of solvents and a wider range of operation conditions are available; and
the concentration of solvent may be controlled by heat and material balances rather
than by the accident of azeotrope composition. Furthermore, since vaporization of
the solvent is not required beat loads are usually considerably less. It has been mainly
used for the separation of toluene, not benzene. But it is mentioned here for the sake
of completeness.
The use of azeotroptc distillation as a means of separation of BTX components
from other non-aromatic hydrocarbons has been known and employed for some thirty
years. Acetone is used as an entrainer to purify benzene from similar-boiling non-aro-
matic hydrocarbons. Toluene can be separated by the use of either methanol, or of
methyl ethyl ketone. Ethyl benzene may be separated from styrene either by isobuta-
nol, of by l-nitro-propane.
In a 1966 review paper, further information was made available. Fifty-eight pos-
sible entraining agents for separating ethyl benzene (bp. 136.20C) and para-xylene
(bp. 138.40C) have been examined. It would appear that 2-methyl butanol is the
most suceessful agent, requiring a column with only 48 percent of the number of the-
oretical plates required if no entrainet were used.
The separation of para-and meta-xylenes (bp. 138. 20C and 139. 2aC respectively ) is
much more difficult. Of thirty five entrainers examined the best appears to be 2-met-
bylbutanol, but the change of relative volatility is only from l. 020 t0 1. 029, and
hence it can be safely concluded that azeotropic distillation for the separation of the
para-and meta-xylenes is not an economic proposition.
Last, and easiest of the C8 aromatics is the separation of meta-from ortho-xylene
( bp. 139. 20C and 144. 50C respectively ). Twenty-eight entrainers were examined,
the best being formic acid, required a column containing only 70 percent of the theo-
retical plates required of no entrainer is used.
Two commercial processes have been developed for the separation of toluene
using azeotropic distillation. One using an aqueous solution of methyl ethyl ketone and wa-
ter and the other using methanol. Both processes operate on a narrow boiling range concen-
zeotrope is a liquid mixture that shows no local maximum or minimum when vapour pressure is plotted as a function of composition.[1] Such a mixture is separable into its component parts by fractional distillation azeotropic distillation[1] is any of a range of techniques used to break an azeotrope in distillation. In chemical engineering, azeotropic distillation usually refers to the specific technique of adding another component to generate a new, lower-boiling azeotrope that is heterogeneous (e.g. producing two, immiscible liquid phases), such as the example below with the addition of benzene to water and ethanol. This practice of adding an entrainer which forms a separate phase is a specific sub-set of (industrial) azeotropic distillation methods, or combination thereof. In some senses, adding an entrainer is similar to extractive distillation.
Distillation is based on the difference between boiling points of liquids. Ethanol is separated first.The distillation is possible only to an ethanol concentration of 95,63 % because an azeotropic mixture is formed.
The difference between evaporation and distillation is evaporation is a function of nature and distillation is a process whether it be to separate a liquid or purify it
what is the difference between fermentation and distillation? Distillation- the separation of alcohol from a fermented liquid by heating to vaportize the alcohol, then condensing the vapors. Fermentation- The action of yeast upon sugar in a solution, which breaks down the sugar into carbon dioxide and alcohol
Distillation is the separation of two liquids using their boiling point While Dehydration is the removal of water from a substance
zeotrope is a liquid mixture that shows no local maximum or minimum when vapour pressure is plotted as a function of composition.[1] Such a mixture is separable into its component parts by fractional distillation azeotropic distillation[1] is any of a range of techniques used to break an azeotrope in distillation. In chemical engineering, azeotropic distillation usually refers to the specific technique of adding another component to generate a new, lower-boiling azeotrope that is heterogeneous (e.g. producing two, immiscible liquid phases), such as the example below with the addition of benzene to water and ethanol. This practice of adding an entrainer which forms a separate phase is a specific sub-set of (industrial) azeotropic distillation methods, or combination thereof. In some senses, adding an entrainer is similar to extractive distillation.
Distillation is based on the difference between boiling points of liquids. Ethanol is separated first.The distillation is possible only to an ethanol concentration of 95,63 % because an azeotropic mixture is formed.
The key difference between fractional and simple distillation is that fractional distillation is used when the components in the mixture have closer boiling points, while simple distillation is used when the components in the mixture have a large difference in their boiling points
when there is less density difference between two liquids of mixture & proper difference in boiling point distillation can be used.
The difference between evaporation and distillation is evaporation is a function of nature and distillation is a process whether it be to separate a liquid or purify it
what is the difference between fermentation and distillation? Distillation- the separation of alcohol from a fermented liquid by heating to vaportize the alcohol, then condensing the vapors. Fermentation- The action of yeast upon sugar in a solution, which breaks down the sugar into carbon dioxide and alcohol
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Distillation is the separation of two liquids using their boiling point While Dehydration is the removal of water from a substance
Both start by boiling a liquid, but in distillation the vapor produced by boiling is captured, cooled, and condensed back to a liquid.
Whether it is better to use fractional or simple distillation depends on the liquids being separated and on the boiling points of the liquids. When there is a great difference between the boiling points of the liquids, simple distillation may be a better option. Likewise, if there is a small difference in boiling points, then fractional distillation is used.
Azotropic will only have one boiling or condensing point for each system pressure negligible fractionation or temperature glide will occur Zeotropic will have a range of boiling and condensing points for each system pressure noticeable fractionationand glide will occur.