Oxidation of propylene with air in barrier discharge in the presence of octane

Article abstract of DOI:10.1134/S1070427211080180

Oxidation of propylene with air in barrier discharge was studied. The effect exerted on the propylene conversion and on the selectivity of propylene oxide formation by replacement of oxygen with air in the course of propylene oxidation was examined. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S1070427211080180

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 8, pp. 1404–1407. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.V. Kudryashov, A.N. Ochered’ko, G.S. Shchegoleva, A.Yu. Ryabov, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84,
No. 8, pp. 1339–1342.
ORGANIC SYNTHESIS AND INDUSTRIAL
ORGANIC CHEMISTRY
Oxidation of Propylene with Air in Barrier Discharge
in the Presence of Octane
S. V. Kudryashov, A. N. Ochered’ko, G. S. Shchegoleva, and A. Yu. Ryabov
Institute of Petroleum Chemistry, Siberian Branch, Russian Academy of Sciences, Tomsk, Russia
Received July 13, 2010
Abstract—Oxidation of propylene with air in barrier discharge was studied. The effect exerted on the
propylene conversion and on the selectivity of propylene oxide formation by replacement of oxygen with air in
the course of propylene oxidation was examined.
DOI: 10.1134/S1070427211080180
Propylene oxide is a valuable raw material for
petrochemical and organic synthesis. Today the most
efficient synthetic route to propylene oxide is the
hydroperoxide procedure ensuring 95–99% yield of
propylene oxide in the reaction of hydrogen peroxide
with propylene in the presence of a titanium–silicon
catalyst [1]. However, both the catalyst and hydrogen
peroxide are expensive, which makes it topical to look
for cheaper procedures for propylene oxide production.
Gas-phase processes attract the greatest attention as
being more convenient in implementation. For ex-
ample, with oxygen and a silver-containing catalyst
modified with various additives, 14 wt % conversion
of propylene with 34–53 wt % selectivity of propylene
oxide formation is attained [2, 3]. With air as oxidant
and silver- or gold-containing catalysts, propylene
oxide is formed with 18–30 wt % selectivity at 1.5–12
wt % conversion of propylene [4–6]. The other
products formed along with propylene oxide are
acetaldehyde, propanal, acetone, acrolein, methanol,
and ethanol. All the above methods have such
drawbacks as the need for preparation and regeneration
of catalysts and the use of high temperatures (150–
alternative to catalytic methods, promising for prac-
tical use.
In this study we examined the possibility of using a
cheaper oxidant, air, for preparing propylene oxide in
BD.
EXPERIMENTAL
Experiments were performed in a flow-through gas-
discharge coaxial reactor. The installation and analysis
procedure are described elsewhere [8]. Propylene was
3
–1
fed to the reactor at a rate of 5.4 cm min (9 vol %),
3
–1
and oxygen, at a rate of 54.6 cm min (91 vol %).
3
–1
The total flow rate of the gas mixture was 60 cm min .
The propylene oxidation products were removed from
the discharge zone with octane: Octane vapor was fed
to the reactor from the vaporizer and was condensed
on the cooled wall of the reactor [9]. The liquid
hydrocarbon film formed on the wall drained to the
receiver together with the dissolved reaction products.
3
–1
The octane flow rate was 0.1 cm min (counting on
liquid). Experiments were performed at atmospheric
pressure. The reactor walls were cooled to 10°С. For
more complete trapping of the reaction products, the
receiver was cooled to –20°С with a mixture of NaCl
and ice. Barrier discharge was excited with a generator
of unipolar attenuating pulses. The voltage pulse
amplitude was 12.8 kV, and the pulse repetition
frequency was 400 Hz. The active power of the
discharge was calculated by the procedure described in
[10]; it was about 2 W at the discharge burning voltage
4
00°С).
As we showed previously [7], in oxidation of
propylene with oxygen in barrier discharge (BD)
propylene oxide is formed in a yield of approximately
4
3 wt % [7]. The reaction occurs at atmospheric
pressure without catalysts and does not require
elevated temperatures. These facts make the plasma-
chemical procedure for preparing propylene oxide, as
1
404

OXIDATION OF PROPYLENE WITH AIR IN BARRIER DISCHARGE
1405
of 3.5 kV. An oscillogram of the voltage pulse exciting
the discharge and an example of the calculation of the
active power and voltage of discharge burning are
given in [11]. The reaction products were analyzed on
a chromatograph equipped with a thermal conductivity
detector. The chromatographic analysis was performed
under the following conditions: packed column 3 m
long, 3 mm i.d.; sorbent Porapak QS; isothermal mode,
Propylene conversion X and selectivity S of product
formation in propylene oxidation with oxygen and air
S, wt %
Product
oxygen
air
Propylene oxide
Propanal
45.00
26.51
3.20
1.70
1.27
8.31
2.32
9.69
2.00
12.9
22.71
23.61
21.76
8.72
4.57
6.68
1.04
7.60
3.31
7.5
1
10°С. To identify the reaction products and determine
Acetone
their amounts, we used reference substances.
Acrolein
The data on propylene conversion and composition
of reaction products in propylene oxidation with air
and oxygen are given in the table.
Allyl alcohol
Methanol
As seen from the table, the selectivity of the
propylene oxide formation with air used as oxidant
decreases to 23 wt %. This value, as well as the
propylene conversion (7.5 wt %), are comparable with
those attained in catalytic oxidation of propylene [4–
Ethanol
Acetaldehyde
Unidentified
X, wt %
6
]. The products formed by propylene oxidation with
air and oxygen have identical compositions.
According to the existing views on the mechanism
of hydrocarbon oxidation in BD, the reaction products
are mainly formed in the reaction of propylene with
atomic oxygen generated from molecular oxygen
under the action of electron impact [12–14]:
Cooling of the receiver allowed more complete
collection and analysis of the propylene oxidation
products, compared to the results given in [7]. We
additionally identified acrolein, ethanol, allyl alcohol,
and propanal. Similar products are formed in the
course of catalytic oxidation of propylene [4–6]. It
should be noted that octane also undergoes oxidation.
The major products of its oxidation are hydroxy and
carbonyl compounds with the same number of C atoms
as in the starting compounds. However, the octane
conversion is low (less than 1 wt %).
O
2
6
+ e → 2O + e,
(1)
(2)
C
3
H
+ O → products.
The lack of proportionality between a decrease in
the propylene conversion and a decrease in the oxygen
concentration in the starting mixture may be due to
generation of an additional amount of atomic oxygen
in the reaction of molecular oxygen with an
electronically excited nitrogen molecule [10]:
It is also seen from the table that the propylene
conversion with air as oxidant decreases by a factor of
only 1.7 relative to the reaction with oxygen (from
*
2
3
+
u
3
N
2
+ e → N
(A Σ
, C П
u
) + e,
(3)
1
2.9 to 7.5 wt %), whereas the oxygen content of the
gas phase decreases by a factor of 4.8. In this con-
nection, it was interesting to examine in more detail
how the concentrations of nitrogen and oxygen affect
the propylene oxidation.
Figure 1 shows the dependence of the propylene
conversion on the nitrogen content of the oxygen–
nitrogen mixture, with the propylene concentration in
the starting mixture kept constant, 9 vol %.
Linear correlation is observed between the
propylene conversion and nitrogen concentration in the
starting mixture. As in the experiments with air, a
decrease in the propylene conversion is not propor-
tional to a decrease in the oxygen concentration in the
starting mixture.
c, vol %
Fig. 1. Propylene conversion X as a function of the nitrogen
concentration с in oxygen–nitrogen mixtures.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 8 2011

1
406
KUDRYASHOV et al.
c, vol %
Fig. 2. Relative distribution E of BD electron energy over
excitation levels of molecules of the starting mixture in
relation to the nitrogen concentration с in oxygen–nitrogen
mixtures. Levels: (1) electronic of oxygen, (2) vibration of
nitrogen, and (3) electronic of nitrogen. The populations of
the vibration and electronic excitation levels of propylene
are about 12 and 7%, respectively.
c, vol %
Fig. 3. Selectivity S of formation of (1) propylene oxide,
(2) propanal, and (3) acetone as a function of the nitrogen
concentration с in oxygen–nitrogen mixtures.
*
N
2
+ O
2
→ 2O + N
2
.
(4)
propylene oxidation products on replacement of
oxygen with air.
Similar effect was observed in generation of ozone
from air [10].
Figure 3 shows how the selectivity of formation of
propylene oxide, propanal, and acetone depends on the
nitrogen concentration in the starting mixture. As can
be seen, for the formation of propylene oxide the trend
is opposite compared to acetone. This fact suggests
that the formation of propylene oxide and acetone is
interrelated and that these products may be formed
from a common intermediate. Apparently, further
transformations of this intermediate depend on the BD
electron energy distribution over the excitation levels
of molecules of the starting mixture. At the same time,
the selectivity of the propanal formation only slightly
depends on the nitrogen concentration in the starting
mixture. The similar composition of products in
propylene oxidation with both air and oxygen suggests
a common reaction mechanism.
This assumption is confirmed by the results of
calculations of the relative electron energy distribution
in BD (%) over excitation levels of molecules of the
starting mixture (Fig. 2). The calculations were
performed using Bolsig program [15] for the field
intensity in the discharge gap of the reactor of 100 T,
which corresponds to the amplitude of high-voltage
pulses of 12.8 kV. The initial data on the differential
cross sections of electron scattering on nitrogen and
oxygen molecules were taken from the database of the
program. Data on differential cross sections of electron
scattering on propylene molecule are available from
[
16, 17], except the cross sections of excitation of
electronic transitions. In this case, we used instead the
data for propane molecule [18–20].
Figure 2 shows that, with an increase in the
nitrogen concentration in the starting mixture, the BD
electron energy loss for the excitation of the electronic
levels of oxygen decreases, and for the excitation of
the electronic levels of nitrogen it, on the contrary,
increases. Hence, a significant part of atomic oxygen at
a nitrogen concentration in the starting mixture of
CONCLUSIONS
(
1) The selectivity of the formation of propylene
oxide in air, compared to oxygen, decreases from 45 to
3 wt %, and the propylene conversion decreases from
2.9 to 7.5 wt %.
2
1
(
2) Preparation of propylene oxide by propylene
7
8 vol % (model of air) can be formed by reactions (3)
oxidation with air in barrier discharge reactors can be
considered in the future as a procedure for commercial
production of propylene oxide, alternative to the cata-
lytic procedure.
and (4). The BD electron energy loss for the excitation
of the vibration levels of the ground electronic state of
the nitrogen molecule also increases. Apparently, the
above factors also affect the selectivity of formation of
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OXIDATION OF PROPYLENE WITH AIR IN BARRIER DISCHARGE
1407
REFERENCES
13. Tanner, D. and Kandanarachchi, P., J. Org. Chem.,
1
998, vol. 63, no. 14, pp. 4587–4593.
1
. Nijhuis, A.T., Makkee, M., Moulijn, J.A., and
Weckhuysen, B.M., Ind. Eng. Chem. Res., 2006, vol. 45,
pp. 3447–3459.
. US Patent 5698719.
. Jin, G., Lu, G., Guo, Y., et al., Catal. Lett., 2003, vol. 87,
nos. 3–4, pp. 249–252.
1
1
4. Zhao, H., Bian, W., and Liu, K.A., J. Phys. Chem. A,
006, vol. 110, pp. 7858–7866.
2
5. Morgan, W.L., Kinema Software BOLSIG, www.siglo-
kinema.com: BOLSIG: User-Friendly Boltzmann Solver
from the SIGLO Series, 1994, URL: http://www.siglo-
2
3
kinema.com/program/bolwin.exe
February 15, 2010).
(addressing
date
4
5
6
7
. Suoa, Z., Jina, M., Lub, J., et al., J. Natural Gas Chem.,
2
008, vol. 17, no. 2, pp. 184–190.
. Luo, M., Lu, J., and Li, C., Catal. Lett., 2003, vol. 86,
nos. 1–3, pp. 43–49.
16. Bettega, M.H.F., Winstead, C., Lima, M.A.P., and
McKoy, V., Abstracts of Papers, Int. Symp. on
Electron–Molecule Collisions and Swarms, Campinas,
SP (Brazil), July 27–30, 2005, p. 80.
. Lu, J., Luo, M., Lei, H., and Li, C., Appl. Catal. A:
General, 2002, vol. 237, nos. 1–2, pp. 11–19.
. Kudryashov, S.V., Ryabov, A.Yu., Sirotkina, E.E., and
Shchegoleva, G.S., Zh. Prikl. Khim., 2004, vol. 77,
no. 11, pp. 1922–1924.
1
7. Kim, Y.-K., Irikura, K.K., Rudd, M.E., et al., Electron-
Impact Cross Sections for Ionization and Excitation,
www.nist.gov: National Institute of Standards and
Technology’s Web Site, 2009, URL: http://
physics.nist.gov/cgi-bin/Ionization/bebcsdwnload?C3H6
8
9
. Kudryashov, S.V., Ryabov, A.Yu., Sirotkina, E.E., and
Shchegoleva, G.S., Khim. Vys. Energ., 2000, vol. 34,
no. 2, pp. 145–148.
. Kudryashov, S.V., Ryabov, A.Yu., Sirotkina, E.E., and
Shchegoleva, G.S., Khim. Vys. Energ., 2003, vol. 37,
no. 3, pp. 220–222.
(addressing date February 21, 2010).
1
1
2
8. Mertz, R. and Linder, F., J. Phys. B: At., Mol. Opt.
Phys., 2003, vol. 36, pp. 2921–2941.
9. Slovetskii, D.N., in Khimiya plazmy (Plasma Chemistry),
1
0. Samoilovich, V.G., Gibalov, V.I., and Kozlov, K.V.,
Fizicheskaya khimiya bar’ernogo razryada (Physical
Chemistry of Barrier Discharge), Moscow: Mosk. Gos.
Univ., 1989.
Moscow: Energoizdat, 1981, issue 8, pp. 189–230.
0. Kim, Y.-K., Irikura, K.K., Rudd, M.E., et al., Electron-
Impact Cross Sections for Ionization and Excitation,
www.nist.gov: National Institute of Standards and
Technology’s Web Site, 2009, URL: Electron-Impact
Cross-Sections for Ionization and Excitation. http://
physics.nist.gov/cgi-bin/Ionization/table.pl?ionization=
C3H8 (addressing date February 21, 2010).
1
1
1. Kudryashov, S.V., Ryabov, A.Yu., Shchegoleva, G.S.,
et al., Izv. Tomsk. Politekh. Univ., 2006, vol. 309, no. 6,
pp. 92–96.
2. Hirokami, S. and Cvetanovic, R., J. Am. Chem. Soc.,
1
974, vol. 96, no. 12, pp. 3738–3746.
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