Multistep Countercurrent Extraction of Organic Sulfur
Compounds and Arenes from the High-Sulfur Diesel Fraction
A. A. Gaile, B. M. Saifidinov, V. V. Kolesov, and L. L. Koldobskaya
St. Petersburg State Institute of Technology (Technical University), St. Petersburg, Russia
Oil and Gas Company, Limited Liability Company, Moscow, Russia
Received September 15, 2009
Abstract―The results of seven-step extractive refining of high-sulfur diesel fraction to remove organic sulfur
compounds and arenes using dimethylformamide, furfuryl alcohol, phenol, and the extraction systems
dimethylformamide–hexane and phenol–hexane are reported.
ORGANIC SYNTHESIS AND INDUSTRIAL
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 3, pp. 473–476. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.A. Gaile, B.M. Saifidinov, V.V. Kolesov, L.L. Koldobskaya, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 3,
Experiments on single-step extractive refining of
the diesel fraction recovered from a mixture of South
Uzbekistan crude oils and containing 2.02 wt % S
showed that the most efficient extractant of organic
sulfur compounds consisting mainly of thiacyclanes is
phenol with addition of water .
However, phenol has some drawbacks, the most
important of which is too high solvency leading to
relatively low yield of the raffinate, and also high
values of toxicity, melting point, and viscosity.
Therefore, we also examined as extractants furfuryl
alcohol and DMF, which are inferior to phenol in the
degree of removal of organic sulfur compounds but
surpass it in certain physicochemical properties im-
portant for extraction technology.
Multistep countercurrent extraction was performed
by the classical scheme in a system of temperature-
controlled separating funnels serving as mixers and
settlers . The number of theoretical plates was taken
equal to seven, taking into account the following facts.
The performance of commercial extraction columns
with sieve plates on LG-35-8/300B installations in
extraction of benzene and its homologs from reformer
naphthas corresponds to approximately seven
theoretical plates . The performance of plate extrac-
tors or columns packed with Raschig rings in selective
refining of oil fractions corresponds to 3–4 theoretical
plates. However, recently regular packings came into
wide use in extractors. For example, installation of
contact units produced by IMPA Engineering Ltd. in
an extractor for refining of deasphalted oil with N-
methylpyrrolidone led to an increase in the number of
theoretical plates of extraction to 5.3, i.e., by a factor
of 2 . The height equivalent to theoretical plate in
extraction depends also on viscosity of the system.
Because the diesel fraction is considerably less viscous
than deasphalted oil, the extractor performance
corresponding to seven theoretical plates can be
readily attained with the same regular packing.
The conditions of experiments on seven-step
countercurrent extractive refining of the diesel fraction
whose characteristics are presented in  are given in
The temperature of the extractants was chosen
equal to 50°C in the majority of experiments, taking
into account the fact that at a higher temperature the
complexes with organic sulfur compounds and
polycyclic arenes become unstable, and the extractant
selectivity and raffinate yield correspondingly de-
crease. The extraction at a still lower temperature is
complicated by problems with cooling of the rege-
nerated extractant. With furfuryl alcohol, the extraction
temperature was increased to 60°С taking into account
lower solvency and high selectivity of this extractant.
The material balance of the extraction refining is
given in Table 2 for run no. 5 as example. The
characteristics of the combined raffinates and extracts
obtained are given in Table 3.