Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 10, pp. 1767−1771.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © I.L. Glazko, S.V. Levanova, E.A. Martynenko, A.A. Sokolova, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 10,
ORGANIC SYNTHESIS AND INDUSTRIAL
Optimization of a Cyclohexanone Distillation Stage
in the Presence of Alkali
I. L. Glazko, S. V. Levanova, E. A. Martynenko,
and A. A. Sokolova
Samara State Technical Unversity, Samara, Russia
Received April 12, 2011
Abstract—Kinetics of two reactions: hydrolysis of esters and condensation of cyclohexanone in an alkaline
environment, was studied in model mixtures. Derived kinetic equations were used to assess optimal parameters
of proceeding cyclohexanone distillation in the presence of alkali.
It is known that the quality of commercial caprolac-
tam, obtained by oxidation of cyclohexane from cyclo-
hexanone by the oxidation scheme, depends on a quality
of the latter. The main impurities of cyclohexanone, which
reduce the caprolactam quality, are products containing
ether, aldehyde groups, unsaturated and macromolecular
compounds [1–3]. They are formed in an oxidation stage
and, remaining in cyclohexanone in distillation, continue
to participate in a various secondary reactions, increase
a permanganate index (PI) of target products, therewith
reducing quality and increasing losses.
Due to the constant increase in requirements for qual-
ity of caprolactam, much attention is paid to cleaning of
raw materials and intermediates, mainly, of cyclohexa-
At factories producing caprolactam, cyclohexane oxi-
dation is carried out following the scheme of extraction
of cyclohexanone from reaction mixture obtained after
oxidation by means of distillation: sequentially unreacted
cyclohexane is removed, then commercial cyclohexanone
and cyclohexanol, as well as high-boiling waste, Oil-X,
are extracted (Fig. 1).
To clean cyclohexanone from impurities in reﬂ ux
columns 3 and 3A for the selection of end product is
added 25–30% aqueous solution of
alkali (KOH), which
promotes the hydrolysis of esters, thereby reducing
the permanganate index . However, it dramatically
increases an amount of condensation products of cyclo-
hexanone (Oil-X), which leads to an increase in its loss
(20–50 kg t
It is known that alkali can catalyze the hydrolysis reac-
tions as well as other processes occurring by nucleophilic
mechanism: decomposition, condensation, dimerization,
etc. So revealing of patterns of competing reactions pro-
ceeding in the presence of alkali at high temperatures is
topical to optimize the distillation stage of cyclohexanone
and to improve its quality.
Crude cyclohexanone (food of column 3A), cyclo-
hexanone-distilled prior to feeding and after feeding of
alkali in the distillation column were used as objects of
the study. Essential number, the value of the PI, and the
content of high-boiling impurities were determined in
the samples by standard methods. The results are shown
in Table 1.
It turned out that during the distillation in the presence
of alkali the essential number is reduced 3 times. This is
due to proceeding the hydrolysis of esters (Scheme 1).
Along with the hydrolysis occur side reactions of
a cyclohexanone autocondensation, which resulted in