1070-4272/03/7608-1351 $25.00 C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 8, 2003, pp. 1351!1353. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 8, 2003,
Original Russian Text Copyright + 2003 by Begak, Syroezhko.
OF FOSSIL FUEL
Improving the Cetane Number of Diesel Fuels
O. Yu. Begak and A. M. Syroezhko
St. Petersburg State Technological Institute, St. Petersburg, Russia
Mendeleev Russian Research Institute of Metrology, St. Petersburg, Russia
Received March 27, 2003
Abstract-Effect of paraffins C
, tert-butyl hydroperoxide, cumyl hydroperoxide,
and isopropyl nitrate as cetane number improvers for summer- and winter-grade diesel fuels
, added in amount
of 0.435 wt %, is studied.
In recent years, the share of diesel fuel (DF) and,
correspondingly, its total annual production volume
have been growing steadily . This is associated, in
particular, with the fact that, in diesel engines, the
compression ratio is higher, and the fuel consumption,
lower by 25!30%, than in carburetter engines .
The cetane number (CN) is the most important
characteristic of DF. It is a measure of the ignitability,
which, in turn, determines the power, ecological, and
economical characteristics of an engine. With increas-
ing CN, the NO
and CO contents in the exhaust de-
The cetane number depends on the group and frac-
tion composition of DF. The cetane number of do-
mestic summer-, winter-, and arctic-grade diesel fu-
els is 47!51, 45!49, and 38!40, respectively. At the
same time, the requirements to the quality of DF, in-
prosed by the World Fuel Charter become more strin-
gent; CN from 48 for DF of the first group to 55 for
DF of the third group . Now, advanced diesel en-
gines are being designed, meant for DT with CN =
The goal of this study was to select cetane number
improvers for commercial diesel fuels from the Kirishi
Refinery and to analyze the effect of these additives
on the performance of DF.
Samples of diesel fuels (DTZ-0.2 minus 35,
DTL-0.2-40, and DTL-0.2-62) and also of paraffins
Fuel from the Kirishi Refinery was studied.
Pour point below 335oC.
, and C
were provided by
the Kirishi Refinery.
The paraffin fraction C
was treated to re-
move arenes by urea dewaxing, recrystallization from
acetone, or acid!base purification, followed by car-
bamide urea. The quality of the resulting product
was controlled by n
 using reference data .
The recrystallization proved to be the most efficient
Paraffin fraction C
had after recrystallization
the minimal refraction intercept (difference between
the refractive index and half of the relative density)
typical of paraffins (1.04!1.0461). For arenes, the re-
fraction intercept is much higher (1.0592!1.0627).
The arene content in the test samples of DF was
determined using the aniline point technique , sul-
fonation, or directly from
C NMR spectra.
n-Alkanes were determined from the
NMR data and also by the urea dewaxing method .
The cloud and pour points of DF were determined
as in , with a mixture of acetone and dry ice as
a coolant. The
C NMR spectra were recorded
on a Bruker AM-500 instrument (500 MHz) with
, and CDCl
as internal references.
The CN of the initial DF samples and those mod-
ified with cetane number improvers was determined
on an IDT-69 device. Isopropyl nitrate was prepared
in accordance with TU (Technical Specifications)
6-14-944!73 . Physical characteristics of tert-
butyl hydroperoxide and cumyl hydroperoxide used
were consistent with reference data .