Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 11, pp. 2052−2054.
Pleiades Publishing, Ltd., 2010.
Original Russian Text © V.S. Leont’ev, A.S. Malin, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 11, pp. 1922−1924.
Minimization of Negative Phenomena Arising
at Rectiﬁ cation of Reactive Mixtures
V. S. Leont’ev and A. S. Malin
Russian Scientiﬁ c Center “Applied Chemistry”, St. Petersburg, Russia
Received July 5, 2010
Abstract—Using the technology of ethyl alcohol production as an example, a scheme of the transformation of
admixed components in rectifying columns was considered and procedures for the minimization of negative side
processes by chemical and instrumental-technological methods were offered.
The instrumental-technological optimization of pro-
cesses occurring on the rectiﬁ cation of reactive mixtures
and thermolabile products is an interesting and poorly
studied problem, as chemical reactions proceeding in
rectifying columns can lead to a concentration disbalance
of the system with respect to one or several components,
can lower its technological stability and result in degrada-
tion of marketable products.
Let us consider in more detail the effect of chemical
processes on the choice and correction of rectiﬁ cation
technological regimens (P, T ) and instrumental execution
(effectiveness of columns, liquid phase dynamic delay,
holding time, and hydraulic resistance) by the example
of the technology of ethyl alcohol isolation.
Ethyl alcohol is one of key products widely applied
in various chemical production branches as basic or aux-
iliary raw materials. Furthermore ethanol is widely used
in food, perfume, pharmaceutical, and other industries.
At the same time, depending on a production method,
ethanol contains several admixtures worsening its quality
and lowering a possibility of application without special
reﬁ ning. The most spread method of reﬁ ning ethanol is
rectiﬁ cation. A number of impurity compounds inherent in
ethanol are rather reactive and inclined to generate other
conversion products on the rectiﬁ cation, the removal of
which is rather difﬁ cult.
With the purpose to detect possible chemical trans-
formations, which can proceed during rectiﬁ cation, the
impurity compounds contained in ethanol were analyzed.
Aldehydes, ketones, organic acids, and esters should be
assigned to admixtures inclined to chemical transforma-
tions upon rectiﬁ cation.
Using chromatography-mass spectrometry, we have
detected acetaldehyde, diethylacetal, isobutyl acetate,
crotonaldehyde, 1,1-diethoxypentane, and some other
compounds in samples of the ethyl alcohol head fraction.
It is necessary to note that acetaldehyde contained in the
ethyl alcohol head fraction in an amount of several per-
cents seems to be responsible for the formation of dieth-
ylacetate, 1,1-diethoxypentane, and crotonaldehyde. The
mechanism of the acetaldehyde reaction with alcohols
can be presented by the following schemes:
Hence the formation of acetals is caused by the reac-
tion of acetaldehyde with two moles of ethanol, which
results in the diethylacetal formation. The formation of
acetals is reversible, basic media (рН > 7) inhibiting
these reactions by shifting the equilibrium aside mother
compounds, acetaldehyde and ethanol. At the same time,
according to the mass action law, an appreciable excess
of ethyl alcohol in relation to acetaldehyde promotes the
chemical binding of an acetaldehyde up to semi- and
diacetals. The addition of optimal amounts of alkaline
reagents (sodium hydroxide and others) in a reaction
system and a rectiﬁ cation temperature decrease promote
the formation of undesirable side diacetals.
The mechanism of the 1,1-diethoxypentane formation