ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 4, pp. 595!599. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + A.A. Gaile, A.S. Erzhenkov, L.L. Koldobskaya, E.A. Kayfadzhyan, 2007, published in Zhurnal Prikladnoi Khimii, 2007,
Vol. 80, No. 4, pp. 608!611.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Extraction of Toluene and Xylenes
from the Toluene!Xylene Fraction of the Reforming
Catalyzate with Mixtures of Triethylene Glycol
A. A. Gaile, A. S. Erzhenkov, L. L. Koldobskaya, and E. A. Kayfadzhyan
St. Petersburg State Technological Institute, St. Petersburg, Russia
OOO [PA Kirishinefteorgsintez,] Kirishi, Leningrad oblast, Russia
Received July 5, 2006
Abstract-Seven-stage counterflow extraction of aromatic hydrocarbons from the toluene3xylene fraction of
the reforming catalysate with sulfolane and its mixtures with triethylene glycol was studied. A liquid3liquid
phase equilibrium diagram is presented for a pseudoternary system that includes saturated and aromatic
hydrocarbons of the toluene3xylene fraction of the reformate and a mixed extractive agent composed of
triethylene glycol, sulfolane, and water (48.1 : 48.1 : 3.8 wt %).
It has been suggested to use a mixed selective sol-
vent composed of triethylene glycol, sulfolane, and
water as an agent for extraction of arenes C
from the reformate of the 623105oC fraction [13 4].
In 2000, this method for extraction of arenes was
implemented on an LG-35-8/300B installation at
OOO [PA Kirishinefteorgsintez] .
In view of modern ecological requirements to
the quality of automotive gasolines, the maximum
permissible content of benzene in the gasolines is
limited by 1 vol % . Benzene can be effectively
removed from the benzene fraction of the reformate
by extractive distillation. For example, an installa-
tion for extractive distillation with a Tectiv-100 mixed
extractive agent composed of industrially available
selective solvents  is to be constructed at OOO
[PA Kirishinefteorgsintez] under license from Glitsch
Technology Co. After the new installation is put in
operation, the extracting unit of the working LG-
35-8/300B installation can be used to obtain toluene
and total xylenes. In doing so, there will be no need
to change the technological scheme of the installation,
provided that the TEG3sulfolane mixed extractive
agent will be used.
However, the activity coefficients and critical so-
lution temperatures (CST) of xylene isomers in polar
solvents markedly exceed those for benzene. For
example, a mixed TEG3sulfolane extractive agent of
70 : 30 wt % composition forms a homogeneous
system with benzene at 25oC, the CST with toluene
is 58.3oC and those with C
arenes are even higher
. Therefore, it is desirable to extract xylenes with
a mixed solvent with higher dissolving power, in-
creased content of sulfolane.
The aim of this study was to compare the efficien-
cies of extraction of arenes from the toluene3xylene
fraction with mixed TEG3sulfolane3water solvents of
Stable reformates from the LG-35-8/300B and
LCh-35-11/600 installations of catalytic reforming
of the benzene3toluene and xylene fractions at OOO
[PA Kirishinefteorgsintez] were used as the starting
raw material. A benzene fraction with IBP 90oC was
distilled-off on a rectification column with an effi-
ciency of 15 theoretical plates in yield of 64.0 and
11.5 wt %, respectively.