22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Nitric oxide and propene abatement by pulsed sub-microsecond corona
discharge reactor
S. Loganathan and A. Khacef
GREMI -UMR 6744, CNRS-Université d'Orléans, 14 rue d’Issoudun, BP 6744, 45067 Orléans Cedex 02, France
Abstract: Nitric oxide (NO) and propene (C 3 H 6 ) removal is carried out at room
temperature using atmospheric pressure multi-pin-to-plate corona discharge reactor.
Results have revealed a mutual sensitization of the oxidation of NO and C 3 H 6 since the
oxidation of C 3 H 6 is accompanied by the conversion of NO, resulting in NO 2 , CO, CO 2 ,
CH 2 O, and CH 3 CHO as the major products. It is evidenced that more than 80% of NO and
C 3 H 6 were converted at 42 W plasma input power.
Keywords: NTP, multi-pin-to-plate, corona discharge, NO, C 3 H 6
1. Introduction
Nitrogen oxides, NO X (NO and NO 2 ) are the major
pollutants in the atmosphere, which lead to acid rain,
photochemical smog. Automobiles and other mobile
sources contribute about 50% of the NO X that is emitted
to the atmosphere [1]. In that, major portion is contributed
by NO. When NO is released into the atmosphere in less
than an hour it is oxidised to NO 2 . The NO 2 , under the
UV light, produces NO and atomic oxygen. The latter one
further reacts with the oxygen (O 2 ) and significantly
increases the atmospheric ozone (O 3 ) concentration.
As a consequence several methods have been
developed to treat the effluents of mobile sources and
power plants. Among them Selective Catalytic Reduction
(SCR) and Selective Non-Catalytic Reduction (SNCR)
are currently in application [2].
The atmospheric pressure non-thermal electrical
discharge is a potential method for NOx reduction and it
has been extensively studied [3, 4]. Several reactors like
pulsed corona discharge, dielectric barrier discharge
(DBD), surface discharge and ferro-electric pellet packedbed discharge have been studied for NO X and HCs
removal. Among them, pulsed corona discharge process
has proved a competitive technology to remove
NOx [2, 5, 6].
In this study, NO and propene (C 3 H 6 ) removal have
been studied by pulsed sub-microsecond corona discharge
reactor. The influence of C 3 H 6 concentration on NO
conversion and vice-versa has been investigated as a
function of plasma input power. A special attention has
been paid to account the total carbon balance and to
identify the organic products.
2. Experimental
Fig. 1 reports the photograph of a multi-pin-to-plate
sub-microsecond corona discharge reactor. The total
length of the reactor is 230 mm. In the total length 17 pins
are placed and the distance between two pins is 13 mm.
The discharge gap between the pins and the plate is 12
mm. The corona reactor was powered using homemade
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high voltage pulsed power supply (kV/ns). The applied
pulsed voltage was varied between 3 and 11 kV, whilst
the frequency was kept constant as 350 Hz.
The applied voltage and current were measured using a
high voltage probe (Tektronix P6015A, 1000x) and a
current probe (Pearson 4100), respectively. The output
signals were transmitted to a digitizing oscilloscope
(Tektronix DPO3054). The maximum measured pulse
energy and the total power injected into the reactor were
about 6 mJ and 52 W, respectively.
Fig. 1. Photograph of the multi-pin-to-plate corona
reactor. The insert shows the ICCD image of the
discharges.
For all the experiment, the total gas flow rate was fixed
as 1 L min-1, unless otherwise mentioned. The calibrated
gas cylinders (1% NO/N 2 , 1% C 3 H 6 /N 2 ) are supplied by
Air liquid company. The inlet concentrations of NO and
O 2 are fixed as 500 ppm and 10%, respectively. For a
given plasma input power, the inlet C 3 H 6 concentration
has been varied between 100 and 500 ppm.
The NO and C 3 H 6 conversions are studied at room
temperature. The concentration of NO, NO 2 , N 2 O, C 3 H 6
CO and CO 2 are followed by gas phase Fourier
Transform Infrared Spectroscopy (FTIR) equipped with
liquid N 2 cooled MCT detector (Nicolet 6700, Thermo
Scientific). The N 2 and O 2 concentrations were followed
using gas chromatography (MyGC, SRA). The sampling
was performed each 3 min. In addition, a multi-gas
1
analyzers (X-Stream, Emerson), equipped with TCD, IR,
and UV detectors, were used to follow the real time
evolution of NO X , N 2 O, CO, and acetylene (C 2 H 2 )
concentrations.
Fig. 3 shows the NO 2 selectivity, for various C 3 H 6 inlet
concentrations, as a function of plasma input power. The
C 3 H 6 additive hardly influences the NO X selectivity.
Filimonova et al [7] have observed the similar
phenomenon for the mixture of HC additives.
3. Results and discussion
The NO conversion (τ NO ) is determined using the
following equation:
𝜏𝑁𝑁 =
[𝑁𝑁]𝑖𝑖 − [𝑁𝑁]𝑜𝑜𝑜
[𝑁𝑁]𝑖𝑖
Eq. [1]
where, [NO] in and [NO] out respectively denote NO inlet
and outlet concentrations. Fig. 2 reports the NO
conversion, as a function of plasma input, power for
different C 3 H 6 concentration in the gas matrix. The NO
conversion increases by increasing the plasma input
power. As can be seen from Fig. 2, when NO (500
ppm)/10% O 2 is sent to the reactor, even under the
maximum input power of 52 W, only 37% of NO
conversion is reached. Moreover, up to 32 W, the NO
conversion rapidly increases and then it gradually
increases by increasing the plasma input power.
Fig. 2.
Influence of C 3 H 6 concentration on NO
conversion as a function of plasma input power. The gas
composition: 500 ppm NO+10% O 2 .
It is evidenced that the addition of C 3 H 6 in the gas
stream significantly increases the NO conversion [5].
When 500 ppm of C 3 H 6 is added to the gas stream, the
maximum of 85% NO conversion is reached. At 52 W
input power, the addition of 500 ppm of C 3 H 6 to the
mixture of 500 ppm NO and 10% O 2 , has increased the
NO conversion by 2.3 times. Indeed, the influence of
C 3 H 6 on NO conversion is more pronounced for input
power higher than 32 W.
Since NO conversion is evidenced the expected product
NO 2 is quantified and reported in Fig. 3. It is important to
mention that for all the experiments a small amount of
N 2 O was measured (16 ppm at the maximum plasma
input power used in this study). Under our experimental
conditions, neither C 3 H 6 concentration and nor plasma
input power has changed the N 2 O production.
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Fig. 3. Evolution of NO 2 selectivity as a function of
plasma input power (total flow rate: 1 L min-1, applied
voltage: 3-12 kV, repetition rate: 350 Hz).
As shown in Fig. 3, up to 24 W input power, the
addition of C 3 H 6 has significantly enhanced the NO 2
selectivity. In contrast, above 24 W, the increase in C 3 H 6
concentration decreases the NO 2 selectivity. For instance,
at 52 W, with 500 ppm of C 3 H 6 the NO 2 selectivity has
decreased by 10% as compared to NO/10% O 2 alone. . It
is widely reported that the high concentration of NO 2
certainly leads to the low temperature SCR reaction [8].
The decrease in NO 2 selectivity can be explained by the
following three hypotheses: (i) complete reduction of NO
to N 2 and O 2 , (ii) formation of nitrated organic
intermediate species, and (iii) production of nitric acid
(HNO 3 ).
To evidence these hypotheses the C 3 H 6 conversion is
followed as a function of plasma input power. Results are
reported in Fig. 4. In order to follow the influence of NO
concentration on C 3 H 6 removal, the conversion of C3H6
is studied in the absence of NO in the gas matrix, i.e.
(C 3 H 6 : 100 ppm, O 2 : 10%, 0 ppm NO), and compared in
Fig. 4. For gas mixture without NO, i.e. C 3 H 6 (100 ppm)O 2 (10%) mixture, total conversion of C 3 H 6 is reached at
only 25 W plasma input power. Indeed, the addition of
500 ppm of NO leads to dramatic decrease of the C 3 H 6
conversion efficiency (45% at 25 W). This evidences the
fact that the presence of NO compete with the active
species which are involved in C 3 H 6 conversion.
Moreover, it is observed that C 3 H 6 conversion decreases
with increasing the inlet concentration.
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also observed that the concentration of these species
decreases with increasing the plasma input power.
Fig. 4. Evolution of C 3 H 6 conversion as a function of
plasma input power for different initial concentrations.
To identify the C 3 H 6 reactions chemistry, CO, CO 2 ,
and organic products have been followed using FTIR. The
amount of CO and CO 2 quantified at the reactor outlet
has been integrated into the total carbon mass balance and
reported in Fig. 5 as a function of C 3 H 6 inlet
concentration.
The COx selectivity (S COx ) is calculated using Eq. 2,
where [CO+CO 2 ] represents the concentration of CO and
CO 2 quantified at the reactor out let.
𝑆𝐶𝐶𝐶 =
[𝐶𝐶+𝐶𝐶2 ]
3[𝐶3 𝐻6 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐]
Eq. [2]
Fig. 5.
Carbon balance as a function of C 3 H 6
concentration for a 52 W plasma input power. The
mixture composition is: 500 ppm NO+10% O 2 .
4. Conclusions
Hydrocarbon (C 3 H 6 ) added to NO/O 2 mixture
significantly enhanced the gas-phase oxidation of NO to
NO 2 by the plasma discharge. The NO and HC oxidation
reactions promote each other, resulting to the formation of
NO 2 , CO X , and CH 2 O as main products and CH 3 CHO,
methanol (CH 3 OH), and acetylene (C 2 H 2 ) as minor
products. The interactions between NO and hydrocarbons
are interesting not only for NOx chemistry, but also at
low temperature for the oxidation of hydrocarbons, a
subject extensively investigated in engine combustion and
ignition phenomena.
5. Acknowledgement
Experiments have been performed in the framework of
ANR REMOVAL project.
The authors greatly
acknowledge the ANR for the financial support and the
project partners (LAPLACE and SUPELEC) for the
fruitful discussions.
6. References
[1] Selective Catalytic Reduction Control of NOx
Emissions, SCR Committee of Institute of Clean Air
Companies, November 1997
[2] M. Koebel, G. Madia, M. Elsener, Catal. Today, 73
(2002) 239-247
[3] S. Masuda, H. Nakao, IEEE Trans. Ind. Appl. 26
(1990) 374–383.
[4] B.M. Penetrante, R.M. Brusasco, B.T. Merritt, G.E.
Vogtlin, Pure Appl. Chem. 71 (1999) 1829–1835.
[5] E.M. van Veldhulzen, W.R. Rutgers, V.A. Bityurin,
Plasma Chem. Plasma Process. 16 (1996) 227–247.
[6] A. Khacef, J.M. Cormier, J.M. Pouvesle, J. Phys. D:
Appl. Phys. 35 (2002) 1491.
[7] E A Filimonova, Y. H. Kim, S. H. Hong, Y.H. Song,
Multiparametric investigation on NO removal from
simulated diesel exhaust with hydrocarbons by
pulsed corona discharge, J. Phys. D: Appl. Phys. 35
(2002) 2795–2807.
[8] B.J. Cooper, A.C. McDonnald, A.P. Walker, M.
Sanchez, US DOE, 9th Diesel Engine Emissions
Reduction Conference (DEER), Newport, RI,
August 2003.
For gas mixture without NO, i.e., C 3 H 6 (100 ppm)-O 2
(10%) mixture, about 94% of total carbon balance is
reached (54% CO and 40% CO 2 ). Noticeably, when 500
ppm of NO is added, the carbon balance has decreased by
a factor 2. Furthermore, the increase in C 3 H 6
concentration does not change the CO and CO 2
production. Apart from CO and CO 2 , formaldehyde
(CH 2 O) and acetaldehyde (CH 3 CHO) are the major
organic species identified at the reactor downstream. It is
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