1070-4272/03/7601-0140$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 1, 2003, pp. 140 !143. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 1,
2003, pp. 146!149.
Original Russian Text Copyright + 2003 by Gaile, Dyurik, Semenov, Chagovets, Ustalov, Koldobskaya, Stepanova.
OF FOSSIL FUEL
Preparation of Transformer Oil Body by Extraction Refining
of 3003500oC Fraction of Low-Paraffinicity Oil
A. A. Gaile, N. M. Dyurik, L. V. Semenov, A. N. Chagovets, A. V. Ustalov,
L. L. Koldobskaya, and G. F. Stepanova
St. Petersburg State Technological Institute, St. Petersburg, Russia
Slavneft Oil and Gas Company, Joint-Stock Company, Moscow, Russia
Slavneft3Mendeleev Yaroslavl Oil Refining Plant, Open Joint-Stock Company, Yaroslavl, Russia
Received May 30, 2002
Abstract-A raffinate meeting the requirements for the transformer oil body was obtained from the 3003
350oC fraction of low-paraffinicity oil by five-step countercurrent extraction of aromatic hydrocarbons and
organoelement compounds with aqueous methyl Cellosolve in the presence of pentane.
Hydraulic oils and transformer oil body are pro-
duced from the 2003300 and 3003350 or 3003400oC
fractions of low-paraffinicity oil, respectively. Low-
paraffinicity oils, among them Troitsk-Anastasievsk
oil, contain virtually no n-alkanes, which allows pro-
duction of low-freezing oils without dewaxing as the
most expensive stage. However, the aromatic hydro-
carbon content in the fraction 2003430oC of the
Troitsk-Anastasievsk oil amounts to 40% (hereinafter,
wt %, unless otherwise stated) . According to the
existing technical specifications, the optimal content
of arenes in it should be within 18322%, the major
part of arenes being represented by monocycloarenes
Transformer oils can be produced from the 3003
400oC fraction by solvent extraction followed by hy-
drogenation. For example, this combined method is
used in production of T-1500U transformer oil [TU
(Technical Specification) 38.401-58-107]. The advant-
age of solvent-extracted oils is in high gas resistance
coefficient, which is caused by the optimal content of
aromatic hydrocarbons (18322%). As their drawbacks,
we can indicate high dielectric loss tangent tan a,
which is due to excessive resin content, resulting in
deteriorated insulating characteristics and oxidation
resistance of the oil. The resin content can be reduced
from 3.2 to 1.231.3% by additional adsorption refin-
ing of a solvent-extracted oil. In this case, tan a de-
creases from 2.2 to 0.243 0.29%, meeting the require-
ments of the technical specifications to T-750 trans-
former oil .
Solvent extraction of oil fractions is performed
with phenol, furfural, or N-methylpyrrolidone [4, 5].
However, all these solvents are relatively high-boiling,
which complicates their regeneration. N-Methylpyr-
rolidone, the most selective and high-boiling of them,
forms azeotropic mixtures with a series of saturated
hydrocarbons of the 2003400oC fraction, which
causes oiling of the solvent and complicates its regen-
eration, thus deteriorating the solvent extraction ef-
ficiency . Regeneration of a solvent by aqueous
backwashing or back extraction of arenes from the
extract phase with saturated hydrocarbons is insuf-
ficiently efficient, causing complication of the process
flowsheet and increase in the power consumption.
Furthermore, all the indicated solvents have certain
inherent drawbacks: phenol, low selectivity with re-
spect to arenes and high toxicity; furfural, low thermal
oxidation resistance; and N-methylpyrrolidone, high
cost and corrosion activity .
To obtain the transformer oil body from low-paraf-
finicity oil fractions, sulfuric acid refining is used.
However, this method does not longer meet the mod-
ern environmental criteria, because of formation of
large amounts of acid tar to be utilized or disposed of.
The goal of this work is to examine the possibility
of production of the transformer oil body from the
3003350oC fraction of low-paraffinicity oil by solvent
extraction using a low-boiling extraction system readi-
ly regenerable by distillation.
Since the oil in hand contains no n-alkanes, one
may draw an analogy between the composition of its
kerosene3gas-oil fractions and that of 2003320oC
fraction dewaxed by adsorption on zeolites (denorma-
lization product of the Parex plant). Previously we