Cyclohexanol nitration by a mixture of ammonium nitrate and sulfuric acid in a two-phase system

Article abstract of DOI:10.1134/S1070427211020303

Cyclohexanol nitration by a mixture of ammonium nitrate and sulfuric acid in the presence of an organic solvent was studied.

Full text of DOI:10.1134/S1070427211020303

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 2, pp. 338−340. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.V. Logvinov, S.F. Melnikova, A.A. Astrat’ev, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 2, pp. 342−344.
BRIEF
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Cyclohexanol Nitration by a Mixture of Ammonium Nitrate
and Sulfuric Acid in a Two-Phase System
A. V. Logvinov, S. F. Melnikova, and A. A. Astrat’ev
St. Petersburg State Technological Institute, St. Petersburg, Russia
Federal State Unitary Enterprise “Technologist” Special Engineering and Technological Bureau,
St. Petersburg, Russia
Received June 21, 2010
Abstract—Cyclohexanol nitration by a mixture of ammonium nitrate and sulfuric acid in the presence of an organic
solvent was studied.
DOI: 10.1134/S1070427211020303
Cyclohexyl nitrate (CHN) is an effective addition
agent raising a cetane number of diesel fuel [1]. One of
promising methods of CHN synthesis is the cyclohexanol
nitration by a mixture of sulfuric and nitric acids, however
it requires lower temperatures (–20…–30°С) owing to
the tendency of cyclohexanol and CHN to be oxidized
by nitric acid [2, 3].
addition of an inert solvent makes it possible to increase
the yield of a reaction product and to raise considerably
stability of the waste acid mixture. Conditions and results
of the experiments are given in the table; the nitrating
mixture composition is specified without taking into ac-
count formed ammonium bisulfate.
For comparison we used solutions of ammonium ni-
trate (experiments nos. 1–6) and nitric acid (experiments
nos. 7, 8) in sulfuric acid, taking methylene chloride as
an inert solvent. The highest yield was reached for the
nitrating mixture containing 3.5% of water at the nitration
temperature of 10–11°С (experiment no. 4). Decrease
in sulfuric acid concentration (experiment no. 5) or in
ammonium nitrate excess (experiment no. 6), and also
the absence of the organic solvent cause uncontrollable
heat release while an alcohol dosing, which hinders the
reaction completion. The composition of the nitrating
mixture obtained when nitric acid was used (experiments
nos. 7, 8) was selected as optimal on the basis of a series
of previous experiments.
It is known that the application of nitrating mixtures
with increased water contents or of mixtures based on
nitric acid salts allows the temperature of cyclohexanol
nitration to be increased up to 5–10°С [4, 5]. However,
as a result of side processes a hazard of an uncontrollable
decomposition of the waste acid mixture accompanied by
heat and gas release increases. The use of an inert organic
solvent in the cyclohexanol nitration by a sulfuric-nitric
mixture makes it possible to increase the CHN yield and
the admissible temperature of the process up to 10–15°С,
but in this case the probability of the decomposition of
the acid layer remains, which demands its fast separation
and neutralization [6, 7]. The uncontrollable heat effect
gives rise to a hazard of exceeding the process critical
temperature and thus can result in contingency situations
connected with equipment decompression, ejection of
a reaction mass, and complete product loss.
Stability of the waste acid mixture after separation of
layers was estimated by varying its temperature during
holding in equal conditionals without effective cooling.
The results obtained are shown in the figure.
As follows from the figure, when ammonium nitrate
is used instead of nitric acid, exhausted nitro mixture
It was found that the application of an ammonium
nitrate and sulfuric acid mixture in combination with
338

CYCLOHEXANOL NITRATION BY A MIXTURE OF AMMONIUM NITRATE
339
is heated up much slower and only by a few degrees
higher than the temperature of ambient air (19–20°С).
The organic layer containing the main part of the product
after acid separation appears sufficiently stable without
backwashing.
Nitrating mixtures based on ammonium nitrate are
characterized by the absence of nitrous acid initiating
oxidative processes. Furthermore, the presence of am-
monium salts decreases CHN solubility in the waste acid,
which on the whole is responsible for the increase in the
process stability. Thus, owing to the reached decrease in
the rate of nitromass decomposition, the necessity of the
fast CHN separation after the reaction and of the acid
layer dilution with water is excluded. According to GLC
data, the resulting CHN samples contain no more than
1.4% of cyclohexanone.
Character of heat release during holding exhausted acid mixture.
(T) temperature of mixture (°С), (τ) time after separation of
acid layer (min). After nitration: (1) using HNO3; (2), (3) using
NH4NO3 at 10–11 and 14–15°С, respectively.
EXPERIMENTAL
added to the resulting mixture and then 4.7 g (0.047 mol)
of cyclohexanol was dosed with intensive stirring, main-
taining temperature at 10–11°С.After dosing termination
the reaction mass was stirred for 10 min more and then
layers were separated. An organic layer was sequentially
washed out by 50 ml of water, 50 ml of 4% Na2CO3 so-
lution, again by water, and dried by anhydrous Na2SO4.
A solvent was removed on a rotor evaporator, and 6.5 g
(95%) of cyclohexyl nitrate was obtained. The acid layer
was placed back in a reactor and held with mixing without
additional cooling.
The GLC analysis was carried out on a Khromos
GKh-1000.1 instrument; a steel column 1 m × 3 mm;
temperature of an evaporator and PID 210, of the column
80°С; the stationary immobile phase 5% SE-30; the car-
rying agent Chromaton-N-AW; the gas-carrier helium;
the volume flow rate 30 ml min–1.
Nitration of cyclohexanol with application of am-
monium nitrate (experiment no. 4). NH4NO3, 5.7 g
(0.071 mol), was dissolved in 20 g of 97% H2SO4 at
10–15°С and held within 1 h.At first 15 ml of CH2Cl2 was
Results of cyclohexanol nitration by sulfuric-nitric acid mixtures
Calculated composition
of nitrating mixture, %
Amount of the initial components,a g
Molar
HNO3
excess
Temperature
of nitration,
°С
Experiment
no.
CHN
yield, %
HNO3
(97%)
H2SO4
(94%)
NH4NO3
HNO3
H2SO4
H2O
1
2
3
4
5
6
7
8
–
–
5.7
5.7
5.7
5.7
5.7
4.5
–
20.0
20.0
20.0
20.0b
15.0
15.8
12.0
12.0
25.7
25.7
25.7
25.6
35.9
25.5
26.4
26.4
67.5
67.5
67.5
70.9
56.9
67.2
68.4
68.4
6.8
6.8
6.8
3.5
7.2
7.3
5.2
5.2
1.5
1.5
1.5
1.5
1.5
1.2
1.5
1.5
4…5
87
85
82
95
–
10…11
14…15
10…11
10…11
10…11
10…11
14…15
–
–
–
–
–
4.5
4.5
88
74
–
a Amount of methylene chloride in all experiments was 15 ml.
b Concentration of sulfuric acid was 97%.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 2 2011

340
LOGVINOV et al.
Nitration of cyclohexanol with nitric acid application
(experiment no. 7). To a mixture of 12.0 g of 94% H2SO4
and 4.5 g (0.069 mol) of 97% HNO3 10 ml of CH2Cl2 was
added, and 4.7 g (0.047 mol) of cyclohexanol was dosed
with stirring, maintaining temperature of 10–11°С.After
dosage termination the reaction mass was held for 5 min
and treated as described above to obtain 6.0 g (88%) of
cyclohexyl nitrate.
REFERENCES
1. Danilov, A.M., Primenenie prisadok v toplivakh dlya avto-
mobolei: Spravochnik (Application of Addition Agents in
Car Fuels: Handbook), Moscow: Khimiya, 2000.
2. Kornblum, N. and Teitelbaum, C., J. Am. Chem. Soc., 1952,
vol. 74, no. 12, pp. 3076–3078.
3. USSR Inventor’s Certificate no. 687791.
4. Piterkin, R.N., Pranov, E.A., and Moskalenko, N.I., Khim.
Promst’., 1997, no. 7, pp. 20–24.
CONCLUSION
5. Piterkin, R.N. and Chesalov, A.M., Khim. Promst’., 2002,
Mixtures of ammonium nitrate and sulfuric acid
containing 3.5% of water with addition of methylene
chloride are most suitable for a safety cyclohexanol nitra-
tion. Necessary molar excess of nitric acid is 1.5 and the
optimal process temperature is 10–11°С.
no. 7, pp. 37–38.
6. German Patent 1016701.
7. Piterkin, R.N. and Chesalov, A.M., Khim. Promst’., 2000,
no. 9, pp. 41–44.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 2 2011