Cycloalkyldecalins as components of jet fuels

Article abstract of DOI:10.1134/S1070427210050307

The possibility of obtaining cycloalkyldecalins by the alkylation of 1- and 2-methylnaphthalenes by cycloolefins with subsequent hydrogenation of methylcycloalkylnaphthalenes was studied. Physicochemical parameters of reaction products were determined, and their structure was defined on the basis of IR and NMR spectra. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S1070427210050307

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 5, pp. 918−920.  Pleiades Publishing, Ltd., 2010.
Original Russian Text  N.F. Akhmedov, S.E. Mamedov, R.A. Akhmedova, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 5, pp. 865−867.
BRIEF
COMMUNICATIONS
Cycloalkyldecalins as Components of Jet Fuels
N. F. Akhmedov, S. E. Mamedov, and R. A. Akhmedova
Baku State University, Baku, Azerbaijan
Received July 22, 2009
Abstract—The possibility of obtaining cycloalkyldecalins by the alkylation of 1- and 2-methylnaphthalenes
by cycloolefins with subsequent hydrogenation of methylcycloalkylnaphthalenes was studied. Physicochemical
parameters of reaction products were determined, and their structure was defined on the basis of IR and NMR
spectra.
DOI: 10.1134/S1070427210050307
As flight velocities in aviation increase the require-
ments to the quality of applied jet fuels raise. They should
have a high density, a maximal heat of combustion, and
a low solidification temperature. The most suitable com-
ponents of jet fuels are cycloalkylnaphtene hydrocarbons
possessing optimal properties for such fuels. However the
content of such hydrocarbons in commercial-grade fuel,
as a rule, is not sufficiently high, therefore the attempts
to find synthetic methods for obtaining fuels with high
contents of naphthene hydrocarbons are undertaken [1,
2]. From this point of view the hydrogenation of cyclo-
alkylnaphthalene hydrocarbons with the aim of obtaining
cycloalkyldecalins and their applications as components
of jet fuels seems promising.
The aim of the present work was to obtain cycloal-
kyldecalins promising as highly heat-producing stable
components of jet fuel.
EXPERIMENTAL
To synthesize cycloalkyldecalins, we used naphtha-
lene and 1- and 2-methylnaphthalenes as initial feed
stock, which were isolated by the fractionation and
crystallization methods from the fraction 200–250°С of
heavy pyrolysis resins (HPR). Cycloalkyldecalins were
synthesized in two stages.
(1) The alkylation of naphthalene and 1- and 2-meth-
ylnaphthalenes by cycloolefins (С5Н10, С6Н12, and
С6Н11СН3) was carried out onY-form zeolite catalysts in
a flowing system at 250°С. Physicochemical parameters
of the cycloalkylnaphthalenes are presented in Table 1.
It was found on the basis of IR and NMR spectra that
1- and 1,2-substituted naphthalenes are the main reac-
tion products.
In the pyrolysis of low-octane petrol and gas oils with
the purpose of obtaining low-molecular olefins a pyrolysis
resin is formed as a side product containing significant
amounts of naphthalene (~27%), methylnaphthalenes
(~20%), and other aromatic hydrocarbons, which do
not find a qualified application as yet, but can be a good
source for obtaining naphthene hydrocarbons. It is known
[3] that the fraction 200–350°Сobtained in the pyrolysis of
oil hydrocarbons during their hydrogenation on Raney
nickel gives a product meeting the requirements for jet
fuels by its quality. It was also offered [4] to hydroge-
nate the fraction 150–320°С of liquid pyrolysis products
on NiO/Al2O3 or on a tungsten-nickel sulfide catalyst at
temperatures of 150–350°С and pressures of 5–25 MPa
with the formation of naphthenes.
(2) Resulting cycloalkylnaphthalenes were subjected
to hydrogenation on a nickel-chromic catalyst. The
hydrogenation was carried out in a rotating (50 rpm)
stainless-steel autoclave of volume 1 l in the presence of
a nickel-chromic catalyst. Cycloalkylnaphthalene, 310 g,
and the catalyst, 10% the cycloalkylnaphthalene weight,
were loaded into the autoclave.After blowing through by
hydrogen, the autoclave was filled with hydrogen up to
the pressure of 9 MPa.At170–190°Сhydrogen absorption
918

CYCLOALKYLDECALINS AS COMPONENTS OF JET FUELS
919
Table 1. Characteristics of cycloalkylnaphthalenes CH3C10H6R,
R = CnH2n-1
and methylnaphtene hydrocarbons are characterized by
anomalously high density and viscosity as compared with
corresponding non-methylated hydrocarbons. It seems to
be connected with a heightened intermolecular interaction
in such compounds.
bp, °С/1
kPa
Cycloalkylnaphthalene
MW
d420
nD20
1-C5H9–С10Н7
160
196 1.0387 1.6129
210 1.0321 1.6019
224 1.0088 1.7008
224 1.0792 1.6055
224 1.0791 1.5960
Spectral identification of cycloalkylnaphthalenes
and their hydrogenated derivatives was fulfilled on
a Bruker-300 spectrophotometer with MDS as an internal
standard and on an FT-IR Varian IR spectrometer.
1-С6Н11–С10Н7
173
186
190
191
1-С6Н10СН3–С10Н7
1-СН3-2-С6Н11–С10Н6
2-СН3-1-С6Н11–С10Н6
The IR spectrum of methylcyclohexylnaphthalene
(MCN) contains intensive absorption bands in the range
1500–1600 cm–1 corresponding to the C–C stretching
vibrations of the aromatic cycle and also in the range
1030–1080 cm–1 connected with planar vibrations of the
C–H bonds. The methylene group in the cycloalkyl radi-
cal manifests itself at 1448 cm–1, and the tertiary carbon
atom shows itself as a doublet with different intensity
of two peaks at 1385–1399 cm–1, which is confirmed by
a band at 3050 cm–1.
began and pressure dropped up to 6 MPa. Then a fresh
portion of hydrogen was fed into the autoclave until
pressure in it raised up to 9 MPa. In the same way two
more times the feeding with hydrogen was carried out.
The reaction was considered finished when at 170–190°С
and pressure of 9 MPa no hydrogen absorption proceeded
within 2 h. After cooling the autoclave the product was
unloaded, filtered from the catalyst, and subjected to
vacuum distillation.
Absorption bands most typical for the naphthalene
molecule are connected with out-of-plane bending C–H
vibrations located in the range of 900–675 cm–1. These
bands can be correlated with the number of adjacent
hydrogen atoms in a ring. Absorption bands observed in
this range correspond to four C–H bonds of one ring and
to two C–H bonds of the second ring, i.e. it is 1-methyl-
2-cyclohexylnaphthalene. Absorption bands in the range
of 1500–1600 cm–1 corresponding to the vibrations of
C–C bonds in the aromatic cycle are absent from the IR
spectrum of its hydrogenated derivative.
Fractions of cycloalkyldecalins were separated and
their physicochemical parameters were determined:
molecular weight, density, refraction index nD20, kine-
matic viscosity at 20 and 50°С, solidification and flash
temperatures, and calorific power (Table 2).
It is seen from Table 2 that cycloalkyldecalins have
a high calorific power, 41197–42820 kJ kg–1, at a high
density (0.92–0.97). It is especially important that cyclo-
pentyl- and cyclohexyldecalins have low solidification
temperatures (–60 and –62°С), whereas solidification
temperatures of methylcyclohexyldecalins are even lower
(–68 and –70°С). High density and kinematic viscosity of
methylcyclohexyldecalins attract attention. This phenom-
enon is known in the chemical literature: methylaromatic
In the NMR spectra of methylcyclohexylnaphthalenes
equivalent protons of the naphthalene series give rise to a
complicated signal in the region of 7.5 ppm, a signal with
δ = 2.1 ppm belongs to protons (3Н) of the methyl group,
and protons of the cyclohexyl group are exhibited at δ =
Table 2. Physicochemical parameters of cycloalkyldecalins СН3С10Н16R, R = CnH2n-1
Kinematic
viscosity ν
Height
of non-
smoking
flame, mm
T, °С
solidifaca-
Calorific
power,
kJ kg–1
bp, °С/1
kPa
20
20
Cycloalkylnaphthalene
MW d4
nD
20°С 50°С
flash
tion
1-С5Н9–С10Н17
138
153
166
165
166
206 0.9209 1.5146
220 0.9119 1.5124
234 0.9176 1.5114
9.3
6.3
5.2
6.5
3.5
41197
42381
42058
42820
42820
–60
167
177
186
185
186
22
24
26
25
26
1-С6Н11–С10Н17
–62
–58
–68
–70
1-С6Н10СН3–С10Н17
1-СН3-2-С6Н11–С10Н16
2-СН3-1-С6Н11–С10Н16
3.8
234 0.9750 1.5256 78.7
234 0.9785 1.5282 81.7
13.05
14.3
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920
AKHMEDOV et al.
1.42–1.8 ppm. The hydrogen atom in the α-position to the
aromatic ring is exhibited at δ = 2.5 ppm, the signal here
being more intensive, because the signal of methyl-group
protons is imposed on it. In the spectrum of the hydroge-
nated derivative, methylcyclohexyldecalin, the signal of
protons of naphthalene series disappears, and the signal
of protons of the methylene groups becomes stronger.
–70°С) and a high calorific power (41197–42820 kJ kg–1)
and correspond to the requirements imposed upon jet
fuels.
(2) A rather low-cost raw material base in the form
of liquid products of heavy pyrolysis resin has been
determined.
REFERENCES
Thus, we can conclude that cycloalkyldecalins, being
high-density and high-caloric products leaning upon a suf-
ficient raw-material base, can find application as components
of jet fuels with a high volume calorific power.
1. Zainulin, R.A., Kukovinets, O.S., Kunakova, R.V., and Tols-
tikov, G.A., Neftekhimiya, 2001, vol. 41, no. 3, pp. 169–177.
2. Norihito Hiyoshi, Mitsumasa Osada, Chandrashekar V.
Rode, et al., Appl. Catal. A: General, 2007, vol. 331, pp. 1–7.
CONCLUSIONS
3. Popl, M., Kuraŝ, M., and Mostesky, J., Erdől und Kőhle,
1970, vol. 23, pp. 492–498.
(1) Cycloalkyldecalins were synthesized by cycloal-
kylation of naphthalene and its methyl derivatives with
subsequent hydrogenation. They represent high-density
stable liquids with a low solidification temperature (–58…
4. Berents, A.D., Vol’-Epshtein, A.B., Mukhina, T.N., and
Avrekh, G.L., Pererabotka zhidkikh produktov piroliza
(Treatment of Liquid Pyrolysis Products), Moscow: Khi-
miya, 1985.
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