Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 7, pp. 1172−1177.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
A.A. Gaile, A.S. Erzhenkov, L.L. Koldobskaya, I.A. Solovykh, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 7,
OF SYSTEMS AND PROCESSES
Liquid–Liquid Phase Equilibrium in the System
Heptane–Toluene–Mixed Extractant Triethylene
A. A. Gaile, A. S. Erzhenkov, L. L. Koldobskaya, and I. A. Solovykh
St. Petersburg State Technological Institute (Technical University), St. Petersburg, Russia
KINEF Limited Liability Company, Kirishi, Leningrad Oblast, Russia
Received February 24, 2009
Abstract—The experimental data on the liquid–liquid equilibrium in the system heptane–toluene–mixed extractant,
a 38.4 : 57.5 : 4.1 wt% triethylene glycol–sulfolane–water mixture, at 50°C were obtained and compared with
the data for the same model hydrocarbon system with sulfolane–triethylene glycol–8 wt% water mixture as
For recovery of С
arenes from reforming catalysts
he 62–105°С fraction, KINEF Limited Liability
Company employs extraction with mixed extractant,
triethylene glycol (TEG)–sulfolane–water mixture,
containing 20–30 wt% sulfolane. Replacement of
TEG by the mixed extractant enabled a decrease in the
extractant: feed ratio (by weight) from 8 : 1 to 4.9 : 1, as
well as additional treatment in the extraction block of the
benzene, and a part of the forxylene, fraction obtained at
mixed xylenes setup  .
Examination of the liquid–liquid equilibrium in
the pseudoternary systems comprised of saturated
arenes, and mixed extractant
represented by triethylene glycol–sulfolane–water
mixtures of various compositions showed that, when
the sulfolane : TEG ratio is increased to 60 : 40 wt%,
the equilibrium diagram is represented by a closed
binodal curve even at 50°С. A decrease in the extraction
temperature should enhance the selectivity of recovery of
arenes, decrease the amount of spent recycling streams,
and additionally improve the performance characteristics
of the setup with respect to the feed.
To elucidate the advantages offered by a 38.4 : 57.5 : 4.1
wt% TEG–sulfolane–water mixture as mixed extractant,
we examined the liquid–liquid phase equilibrium at 50°С
in the model system heptane–toluene–mixed extractant
with indicated composition (Table 1).
Table 1 presents the toluene concentrations in the
rafﬁ nate and extract, the toluene recovery in one-step
extraction, distribution coefﬁ cients of toluene and hept-
, and separation coefﬁ cients β =
characterizing the extractant selectivity.
All these parameters were calculated with the use of the
To compare the performance characteristics of the
mixed extractant, individual sulfolane, and TEG with 8
wt% water we used published data on the liquid–liquid
equilibrium for the same model system heptane–toluene
in the presence of sulfolane  and of TEG with 8 wt%
water  and calculated the same extraction parameters
The correctness of our experimental data and those
available in the literature was checked by the Othmer–
Tobias and Hand methods (Table 2) .
Table 2 lists the correlation coefﬁ cients r and constants
a and b from the linear equations. The r values suggest
a higher degree of thermodynamic consistency of our
experimental data, especially in comparison with the
data available from the
All-Russia Research Institute for
Petrochemical Processes .