Facile catalytic decomposition at low temperature of energetic ionic liquid as hydrazine substitute

Article abstract of DOI:10.1002/ejic.200500095

Platinum supported on doped alumina catalysts were prepared and evaluated for the decomposition of NH₃OHNO₃/ water energetic liquid. Powdered and shaped catalysts remain active after 23 injections at 45 °C. Wiley-VCH Verlag GmbH & Co

Full text of DOI:10.1002/ejic.200500095

SHORT COMMUNICATION
Facile Catalytic Decomposition at Low Temperature of Energetic Ionic Liquid
as Hydrazine Substitute
[a]
[a]
[a]
[a]
Laurence Courthéoux, Dan Amariei, Sylvie Rossignol* and Charles Kappenstein
Keywords: Platinum-based catalyst / Sol-gel synthesis / Ionic liquids / Alumina-silica / Catalyst activity
Platinum supported on doped alumina catalysts were pre-
pared and evaluated for the decomposition of NH OHNO
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
3
3
/
water energetic liquid. Powdered and shaped catalysts re-
main active after 23 injections at 45 °C.
Energetic liquid compounds known as monopropellants In this paper, we present the activity of powdered and
are used for propulsion and gas generator purposes. For shaped (spheres) catalysts for successive HAN/water injec-
example, the orbit and attitude control of satellites is ob- tions. These successive injections were carried out to simu-
tained through small thruster engines using the catalytic de- late the pulse mode of the satellite thrusters. The catalysts
composition of hydrazine, N H , on supported iridium cat- (160 mg) are preheated at 45 °C during 1 h, then 100 μL
2
4
alysts. The high toxicity of hydrazine induces high costs and (150 mg) of a binary 79 wt.-% HAN/water mixture (i.e.
its replacement by a less toxic propellant is of current inter- 1.23 mmol) was injected manually 23 times, using a syringe,
est.[ The most currently proposed and studied hydrazine in the constant volume reactor (167 cm ). Each injection
substitutes are energetic aqueous ionic liquids and a repre- is made after the thermal re-equilibration (approximately
sentative mixture contains hydroxylammonium nitrate (or 4 min); the number of injections is limited by the pressure
1,2]
3
+
–
[3–5]
NH OH NO , HAN) as oxidizer, water and a fuel.
gauge and by the size of the sample holder.
3
3
Nevertheless, the use of such mixtures involves more drastic
The evolution of pressure and temperature (catalyst and
conditions than for hydrazine, due to the high temperature gas phase) as a function of time during the successive injec-
reached during the decomposition (up to 1400 °C) and the tions using the sphere-shaped catalyst are represented in
need of frequent restarts that involve a preheating of the part a of Figure 1. Each peak corresponds to the decompo-
catalyst (300–400 °C). Therefore, a high catalytic activity at sition following the injection, with an ignition delay of
low temperature (20–200 °C) associated with a high thermal about 0.5 s; the catalysts are still active after all the injec-
stability of shape formed catalysts remain critical parame- tions. The decomposition reaction can form the thermo-
ters for the future development of new engines.
dynamic products N , O and H O [Equation (1)] or give
2 2 2
Previous studies performed by our group have revealed additional kinetic products, in the form of nitrogen oxides
that platinum supported on thermally stable Si-doped alu- [i.e. Equation (2)]. The calculated values of pressure in-
[
6,7]
mina displays a good activity at low temperatures
The crease (gas phase temperature: 25 °C) using the perfect gas
powder or shaped Si-doped alumina (xerogel) are obtained formula are 365 mbar and 91 mbar, respectively, for a reac-
by sol-gel procedure and were demonstrated to be stable at tion giving thermodynamic [Equation (1)] and kinetic
high temperature (1200 °C, 5 h);[ the metallic phase (10 [Equation (2)] products.
8]
[11]
wt.-% Pt) is added by the wet impregnation procedure.
NH
2
OHNO
3
(aq) Ǟ N
2
(g) + O
2
(g) + 2 H
2
O(l)
(1)
(2)
These catalysts have been evaluated for the decomposition
of HAN/water solutions in a lab-made constant volume
[
9]
batch reactor, and lead to decomposition at very low tem- NH OHNO (aq) Ǟ NO (g or aq) + 0.5 N (g) + 2 H O(l)
3
3
2
2
2
[10]
peratures, less than 60 °C, whereas the thermal decompo-
sition temperature is in the range 115–120 °C.[ Another
key point concerns the long-term stability of the catalysts,
particularly in the presence of a large amount of propellant.
4]
Moreover, in both cases, the reaction produces water,
which stay for the main part in the sample holder. An en-
largement of a catalytic decomposition peak is given in Fig-
[
a] Laboratoire de Catalyse par les Métaux, University of Poitiers, ure 1b; for each peak, the pressure increase (ΔP) due to
LACCO UMR 6503,
[10]
the formation of gaseous products
and the rate of the
4
0 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France
–1
decomposition (slope: ΔP/Δt in mbar·s ) between the
Fax: +33-5-49454157
E-mail: sylvie.rossignol@univ-poitiers.fr
points 1 and 2 are determined. The catalyst temperature-
Eur. J. Inorg. Chem. 2005, 2293–2295
DOI: 10.1002/ejic.200500095
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2293

L. Courthéoux, D. Amariei, S. Rossignol, C. Kappenstein
SHORT COMMUNICATION
Figure 2. Evolution of pressure increase (ΔP) values during the 23
2
successive injections of 79 wt.-% HAN/H O at 45 °C on both cata-
lysts.
–1
4
00 mbar·s . The nonreproducible oscillations are due to
the manual injection procedure. An automatic injection sys-
tem using a microburette failed for this pulse injection
mode. These results show the very good efficiency of both
catalysts and the noninhibiting effect of the shaping. Never-
theless, mechanical breaking of the spheres has been ob-
served during the reaction probably due to the strong exo-
thermic decomposition of the HAN/H O solution. This me-
Figure 1. (a) Catalytic decomposition of 79 wt.-% HAN/H
2
O at
2
4
5 °C with the sphere-shaped sample (23 injections) and (b) en- chanical breaking could be avoided by a preheating at
largement of one decomposition peak (see arrow, part a): Determi-
nation of pressure increase and the slope between points 1 and 2.
100 °C.
decrease is due to the heat transfer to the reactor; the pro-
gressive reduction of the temperature maxima (106 to
70 °C; Figure 1a) is related to the increasing amount of
water in the sample holder. The pressure increase (ΔP) vari-
ations of the two catalysts are similar, as shown in Figure 2.
The values gradually decrease from 140 mbar at the begin-
ning, to 110 mbar at the end of the 23 injections, corre-
sponding to 0.94 and 0.74 mmol of gaseous product formed
during the decomposition reaction. This decrease can be
explained by a small deactivation of the catalyst related to
the increasing amount of water in the sample holder. The
pressure-increase values for both samples are close to the
kinetic value (91 mbar), indicating the formation of nitro-
gen oxides. Other experiments carried out in a dynamic re-
actor with on-line MS analysis are in progress in order to
determine the gas phase composition during the decompo-
sition reaction. The first results show the formation of kin-
Figure 3. Evolution of ΔP/Δt slopes during the successive injections
of HAN/H O at 45 °C on the powder and sphere-shaped catalysts.
2
All these experiments display the very good activity and
etics products, such as NO, NO and lower amounts of stability of our catalysts. Indeed they allowed the efficient
2
[
12]
N O.
2
decomposition of the HAN/water solution at low tempera-
The evolution of the decomposition rate (measured by ture (45 °C) even in presence of a large amount of solution.
the ΔP/Δt slope) during the 23 successive injections on both Moreover, these materials remain active, showing a high re-
catalysts is given in Figure 3. Whatever the catalyst, an in- action rate and an important pressure increase, after 23
crease of the reaction rate is evidenced until the seventh monopropellant injections which remains a challenge for
–
1
injection to reach 434 mbar·s for the sphere-shaped sam- the development of new satellites thrusters. Nevertheless,
–
1
ple and 323 mbar·s for the powder, indicating a fast reac- the breaking of the sphere implies to find a more mechani-
tion rate. Then, the slope values oscillate between 200 and cally stable shaped catalyst support.
2294
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2293–2295

Catalytic Decomposition of Energetic Ionic Liquid as Hydrazine Substitute
SHORT COMMUNICATION
[
[
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The authors wish to thank the CTI Company for the shape forming
of the samples, the French Space Agency (CNES, Nicolas Pillet)
and the European Space Agency (Mark Ford) for funding this
study.
[
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Eur. J. Inorg. Chem. 2005, 2293–2295
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2295