The reaction route and active site of catalytic decomposition of hydrazine over molybdenum nitride catalyst

Article abstract of DOI:10.1016/j.jcat.2004.02.035

The catalytic properties of the passivated, reduced passivated, and fresh bulk molybdenum nitride for hydrazine decomposition were evaluated in a microreactor. The reaction route of hydrazine decomposition over molybdenum nitride catalysts seems to be the same as that of Ir/γ-Al ₂O₃ catalysts. Below 673 K, the hydrazine decomposes into N₂ and NH₃. Above 673 K, the hydrazine decomposes into N₂ and NH₃ first, and then the produced NH₃ further dissociates into N₂ and H₂. From the in situ FT-IR spectroscopy, hydrazine is adsorbed and decomposes mainly on the Mo site of the Mo₂N/γ-Al₂O₃ catalyst.

Full text of DOI:10.1016/j.jcat.2004.02.035

Journal of Catalysis 224 (2004) 473–478
www.elsevier.com/locate/jcat
Research Note
The reaction route and active site of catalytic decomposition of hydrazine
✩
over molybdenum nitride catalyst
∗
∗
Xiaowei Chen, Tao Zhang, Mingyuan Zheng, Zili Wu, Weicheng Wu, and Can Li
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, PO Box 110, Dalian 116023, China
Received 14 November 2003; revised 10 February 2004; accepted 10 February 2004
Abstract
The catalytic properties of the passivated, reduced passivated, and fresh bulk molybdenum nitride for hydrazine decomposition were
evaluated in a microreactor. The reaction route of hydrazine decomposition over molybdenum nitride catalysts seems to be the same as that
of Ir/γ -Al O catalysts. Below 673 K, the hydrazine decomposes into N and NH . Above 673 K, the hydrazine decomposes into N and
2
3
2
3
2
NH first, and then the produced NH further dissociates into N and H . From the in situ FT-IR spectroscopy, hydrazine is adsorbed and
3
3
2
2
decomposes mainly on the Mo site of the Mo N/γ -Al O catalyst.
2
2 3

2004 Elsevier Inc. All rights reserved.
Keywords: Molybdenum nitride; Hydrazine decomposition; FT-IR spectroscopy; Hydrazine adsorption
1
. Introduction
Generally speaking, there are two typical reaction routes
for hydrazine decomposition as depicted in Eqs. (1) and (2)
[
8,9,11]. The produced ammonia decomposes further into
Recently, the catalytic performances of transition metal
nitrogen and hydrogen at elevated temperatures according
to Eq. (3). Eq. (4) describes the overall reaction of hydrazine
decomposition. In Eq. (4), X is defined as the selectivity of
hydrazine decomposition, which is the decomposition per-
centage of hydrazine followed by Eq. (1):
nitride and carbide catalysts for hydrazine decomposition
have been studied because of their low cost and platinum-
like behavior in catalysis [1–6]. Transition metal nitride and
carbide catalysts have the potential to substitute for the tradi-
tional noble metal catalyst (20–40 wt% Ir/Al2O3), which has
been widely applied to hydrazine decomposition in space
technology since the 1970s [7–10].
In 1997, hydrazine decomposition over molybdenum ni-
tride and tungsten carbide catalysts was reported for the first
time [1]. Their catalytic properties were similar to those of
the iridium catalyst in a thruster. Three years later, tungsten
nitride and niobium nitride catalysts were also studied for
hydrazine decomposition reaction. The activity of niobium
nitride was lower than that of tungsten nitride and iridium
catalysts [2]. Moreover, alumina-supported molybdenum ni-
tride and carbide catalysts are active as Ir catalysts for hy-
drazine decomposition in the thruster [5,6].
N2H4 = N2 + 2H2,
3
(1)
(2)
(3)
(4)
N2H4 = N2 + 4NH3,
NH3 = N2 + 3H2,
2
3N2H4 = 4(1 − X)NH3 + (1 + 2X)N2 + 6XH2.
It has been reported that the reaction route of hydrazine
decomposition depends on the metal and the temperature
range [11]. For instance, the main reaction over Ir, Ni, Co,
Ru, Ag, and Cu catalysts proceeds through Eq. (2), while
reactions (1) and (2) can take place over Rh, Pt, and Pd cat-
alysts at the same time between 333 and 433 K [3]. Further-
more, the products of hydrazine decomposition over tung-
sten carbide catalysts are nitrogen and ammonia, suggesting
that the reaction route is through Eq. (2) [3].
Although the catalytic performances of transition metal
nitrides and carbides for hydrazine decomposition have been
studied extensively, little attention has been paid to the in-
trinsic activity, reaction route, and active site on transition
✩
This work was supported by a grant from the Natural Science Founda-
tion of China (NSFC) for Outstanding Youth (No. 20325620).
*
Corresponding authors.
E-mail addresses: taozhang@dicp.ac.cn (T. Zhang), canli@dicp.ac.cn
C. Li).
(
0021-9517/$ – see front matter  2004 Elsevier Inc. All rights reserved.
doi:10.1016/j.jcat.2004.02.035

474
X. Chen et al. / Journal of Catalysis 224 (2004) 473–478
metal nitride and carbide catalysts. In this work, the cat-
alytic activities of passivated, reduced passivated, and fresh
molybdenum nitride catalysts for hydrazine decomposition
evaluated in a microreactor are compared in order to corre-
late the catalysis nature and surface chemistry of molybde-
num nitride catalysts. FT-IR spectroscopy, combined with
the adsorption of probe molecules, has been employed to
characterize the surface of molybdenum nitride catalysts
through the liquid hydrazine. The feedstock consists of about
3 vol% N H in Ar. The space velocity of the N H /Ar mix-
ture was 17,000 h . A 0.04 ml catalyst and 0.26 ml silica
were mixed together and placed in the quartz reactor. Dif-
ferent activation procedures were used. Before the reaction
2
4
2
4
−1
test, the fresh Mo N was obtained by renitriding the passi-
2
vated Mo2N through a flow of ammonia (ꢀ 99.99%). The
flow rate of ammonia is 100 ml/min. The temperature was
raised to 973 K with a rate of 10 K/min and held at this
temperature for 1 h. The passivated Mo2N catalyst was re-
duced by H2 at 773 K for 1 h and is called reduced passivated
Mo2N catalyst. The 31.6 wt% Ir/Al2O3 catalyst was also re-
duced by H2 at 773 K for 1 h before the catalytic test. The
initial reaction temperature was 303 K and was gradually in-
creased until N2 and H2 were detected as the main products
of reaction.
[
12–14]. The hydrazine adsorption and decomposition over
a Mo2N/γ -Al2O3 catalyst were investigated by in situ FT-IR
spectroscopy for the first time. The reaction route of hy-
drazine decomposition over molybdenum nitride catalyst is
also proposed.
2
. Experimental
The feedstock and the product analysis were carried
out using an on-line gas chromatograph (Agilent-6890)
equipped with a thermal conductivity detector and an au-
tomatic injection valve. The carrier gas is argon. Separation
of the products is achieved using a Chromosorb 102 column
and a 13 X molecular sieve column before the detector.
2
.1. Catalyst preparation
Bulk molybdenum nitride catalyst was prepared by
temperature-programmed reaction of MoO3 and ammonia
ꢀ 99.99%). The temperature was increased from room tem-
(
perature to 573 K at a rate of 5 K/min and then to 973 K at
a rate of 1 K/min, and finally was kept at the terminal tem-
perature for 2 h. The nitrided sample was cooled to room
temperature in a flow of ammonia and passivated with a mix-
ture of 1 vol% O2/N2 to avoid the violent oxidation of the
prepared catalyst before exposure to air. The BET specific
2.3. NH3-TPD characterization
Catalysts (200 mg) were reduced at 773 K for 1 h and
then were flushed for 0.5 h at 773 K with He. When the
temperature was decreased to room temperature, NH3 was
injected using a syringe until saturation. During the TPD
process the desorbed products were monitored by TCD and
a mass spectrometer (Omnistar) at the same time. The sig-
nals of m/e = 2, 14, 15, 16, 17, 18, and 28 were detected
simultaneously.
2
surface area of the passivated bulk Mo2N is 104 m /g. The
XRD result shows that the main phase of this sample is γ -
Mo2N.
The supported Mo2N/γ -Al2O3 (8.7 wt%) catalyst was
synthesized by nitriding MoO3/γ -Al2O3 precursor with am-
monia. The nitrided and passivated procedures are the same
as those for the bulk molybdenum nitride sample. The
MoO3/γ -Al2O3 precursor was prepared by the incipient
wetness method using an aqueous (NH4)6Mo7O24·4H2O so-
lution and γ -Al2O3, followed by drying at 393 K for 12 h
and calcination at 773 K for 4 h. The BET specific surface
2
.4. FT-IR studies
2
All the infrared spectra were collected at room temper-
area of γ -Al2O3 is 198 m /g.
ature on a Fourier transform spectrometer (Nicolet Impact
A commercial 31.6 wt% Ir/Al2O3 catalyst with BET spe-
−
1
2
410) with a resolution of 4 cm and 64 scans in the region
4
cific area of 164.9 m /g was used and compared with the
−1
000–1000 cm . A passivated 8.7 wt% Mo2N/γ -Al2O3
molybdenum nitride catalyst in the catalytic activity test and
NH3-TPD experiment. In order to obtain good transmission
in IR measurements, Ir/Al2O3 and Mo2N/Al2O3 with lower
metal loadings (7.7 and 8.7 wt%, respectively) were used.
The 7.7 wt% Ir/γ -Al2O3 catalyst was prepared by the incip-
ient wetness method using an aqueous solution of H2IrCl6
sample was pressed into a self-supporting wafer and put into
a quartz IR cell with CaF2 windows. The passivated sample
was heated in ammonia from room temperature to 623 K at
a rate of 10 K/min, and then to 723 K at a rate of 1 K/min,
further from 723 to 903 K at a rate of 3 K/min, and then
held at this temperature for 1 h. The passivated sample ren-
itrided by NH3 in the IR cell is called fresh Mo2N/γ -Al2O3
sample, while the passivated sample treated with H2 at 773 K
for 1 h is denoted as reduced passivated Mo2N/γ -Al2O3. Be-
fore adsorption the as-prepared sample was held in vacuum
at 773 K for 1 h and then cooled to room temperature. All the
spectra were obtained at RT after the system was evacuated
2
and γ -Al2O3 (198 m /g), and then dried at 393 K for 12 h
and calcinated at 673 K for 4 h.
2
.2. Catalyst tests
The catalytic activities were evaluated in a fixed-bed con-
tinuous flow microreactor. The temperature of liquid hy-
drazine remained at 303 K and a flow of Ar gas was passed
−
2
at 10 Pa.

X. Chen et al. / Journal of Catalysis 224 (2004) 473–478
475
3
. Results and discussion
order to know the reaction route of hydrazine decomposi-
tion over molybdenum nitride catalysts, thermal decomposi-
tion and catalytic decomposition over the commercial Ir/γ -
Al O catalyst and fresh bulk Mo N catalyst are shown in
Previous literature shows that the surface of fresh, re-
duced passivated, and passivated molybdenum nitride cat-
alyst is quite different [12,13]. However, most studies about
the catalytic decomposition of hydrazine over passivated
transition metal nitrides and carbides were investigated in
thrusters on which there is a thin oxynitride or oxycarbide
layer on the surface of the catalyst [1,2,4–6]. In order to gain
sight into the intrinsic catalytic property of molybdenum ni-
tride catalyst, the catalytic activities of passivated, reduced
passivated, and fresh bulk Mo2N catalysts for hydrazine de-
composition versus reaction time at 303 K were compared
in the microreactor (Fig. 1). It can be seen that the conver-
sion of hydrazine over the passivated Mo2N catalyst is only
about 20% at the beginning and then decreases slightly with
reaction time. The hydrazine conversion declines to 7% af-
ter 240 min on stream. After the passivated Mo2N catalyst
was reduced with H2 at 773 K for 1 h, the catalytic activities
for hydrazine decomposition increase significantly. The hy-
drazine conversion is around 90% and then tends to be stable
at the level of 80%. It was reported that after the passivated
Mo2N sample was renitrided at 973 K, the BET specific
surface area, the crystal structure, and the H2 uptake charac-
teristics are similar to those of the fresh one [12–15]. As seen
in Fig. 1, the conversion of hydrazine over a fresh Mo2N cat-
alyst remains 100% in the initial 20 min on stream, and then
decreases slightly with the increase of reaction time. This
result indicates that there is no big difference between the
fresh and the reduced passivated Mo2N catalysts. However,
the catalytic activities of the passivated Mo2N catalyst are
relatively lower than those of the fresh Mo2N catalyst. The
lower activity of the passivated Mo2N catalyst is due to the
passivated procedure, which leads to great change on the sur-
face of the Mo2N catalyst.
2
3
2
Fig. 2.
Without any catalyst, no reaction occurs when the reac-
tion temperature is below 473 K. As soon as the reaction
temperature is up to 473 K, hydrazine begins to decompose
into N and NH . The conversion of hydrazine increases
with increasing reaction time. Hydrazine decomposes com-
pletely at 513 K. When the reaction temperature is increased
gradually, H2 begins to appear and the selectivity to reac-
tion (1) increases. The selectivity to H2 is about 15% at
2
3
9
73 K. For the thermal decomposition of hydrazine, the main
reaction is reaction (2) below 873 K.
The hydrazine conversion is 100% over 31.6 wt% Ir/Al2-
O3 catalyst even at 303 K. Below 573 K, the main products
of hydrazine decomposition are N2 and NH3, and then the
selectivity increases with increasing reaction temperature.
N2, H2, and NH3 exist in the products of hydrazine decom-
position at the same time. When the temperature is up to
7
23 K, NH3 vanishes, and the selectivity of the catalyst is
As noted in Section 1, hydrazine decomposes into hy-
drogen, nitrogen, and ammonia by two reaction routes. In
Fig. 2. Thermal decomposition of hydrazine and catalytic decomposition of
hydrazine on fresh bulk Mo N and 31.6 wt% Ir/γ -Al O catalysts: (a) hy-
Fig. 1. Hydrazine decomposition over fresh, reduced passivated, and passi-
2
2 3
vated bulk Mo N catalysts at 303 K.
drazine conversion, (b) selectivity of hydrazine decomposition.
2

476
X. Chen et al. / Journal of Catalysis 224 (2004) 473–478
1
00%; that is, hydrazine decomposes mainly through reac-
tion (1). Similar to the Ir/γ -Al2O3 catalyst, the main prod-
ucts are N2 and NH3 below 673 K over fresh Mo2N catalyst
and then the selectivity of the catalyst begins to increase with
increasing reaction temperature. H2 starts to be produced
when the temperature is above 773 K and the hydrazine de-
composition is mainly followed by reaction route (1).
The produced ammonia could decompose into nitrogen
and hydrogen at elevated temperatures. It has been reported
that both Ir/γ -Al2O3 and transition metal nitrides are ex-
cellent catalysts for NH3 decomposition [16–20]. In order
to make sure that the produced ammonia decomposes into
N2 and H2 at the elevated temperatures, NH3-TPD over
γ -Al2O3, commercial 31.6 wt% Ir/Al2O3, and bulk Mo2N
catalysts were studied. As seen in Fig. 3, the maximum
NH3 desorption (mass = 16) appears around 370 K on the
γ -Al2O3 support. No N2 (mass = 28) and H2 (mass = 2)
desorption peaks are observed. NH3 desorbs from the Ir/γ -
Al2O3 catalyst from 330 to 430 K. The desorption of N2
commences in the temperature region of 500–700 K; mean-
while, a H2 desorption peak appears. Therefore, the desorp-
tion peaks of N2 and H2 are attributed to NH3 decompo-
sition on Ir/γ -Al2O3 catalyst. NH3-TPD for reduced passi-
vated bulk Mo2N is also shown in Fig. 3. Although there are
two kinds of NH3 desorption peaks in the low temperature
range (300–600 K), which are different from the Ir/Al2O3,
the desorption of N2 and H2 can also be found in temper-
atures higher than 600 K. The N2 desorption between 600
and 800 K is accompanied by H2 desorption. It must come
from the decomposition of NH3. On the other hand, the N2
desorption peak at temperatures higher than 800 K should
be the result of Mo2N decomposition. The NH3-TPD results
suggest that there are active sites for NH3 decomposition on
both the Ir/γ -Al2O3 and Mo2N catalysts, and also at elevated
temperatures the produced NH3 really decomposes into N2
and H2. The similar product distributions of hydrazine de-
composition and similar NH3-TPD profiles over Ir/γ -Al2O3
and molybdenumnitride catalysts indicate that hydrazinede-
composition experiences similar reaction routes on Ir/Al2O3
catalysts and fresh Mo2N catalysts. At lower temperatures,
hydrazine decomposes into nitrogen and ammonia. Above
6
73 K, hydrazine decomposes into nitrogen and ammonia.
Fig. 3. The NH -TPD profiles (mass spectroscopy) of γ -Al O , 31.6 wt%
3
2 3
In the second step the produced ammonia dissociates into
nitrogen and hydrogen.
Ir/γ -Al O , and reduced passivated bulk Mo N.
2
3
2
Fig. 4 shows the IR spectra of adsorbed NH3 and N2H4
on γ -Al2O3, N2H4 on 7.7 wt% Ir/γ -Al2O3 catalyst, and
gaseous N2H4. The gas phase of hydrazine has three char-
could be assigned to the adsorbed NH3 on the Lewis acid
−1
site of γ -Al2O3, and the band at 1484 cm could be at-
tributed to ammonium ions. N2H4 adsorption on the reduced
Ir/γ -Al2O3 catalyst at 773 K shows absorbance features at
−1
acteristic IR bands at 3330–3287, 1620, and 1262 cm
−1
(
Fig. 4, a). The 3330–3287 cm band can be attributed to
−1
the vibrations of N–H stretching, while the bands at 1620
1620, 1484, and 1262 cm (see Fig. 4,d). Considering the
−1
and 1262 cm are mainly assigned to the N–H bending
results of NH3 and N2H4 adsorption on γ -Al2O3, the band at
−
1
+
vibrations [21]. When N2H4 is adsorbed on γ -Al2O3, the
1484 cm can be attributed to the NH4 , which is produced
by NH3 adsorption on the surface of the catalyst. These re-
sults suggest that hydrazine decomposition occurs on the
−1
characteristic IR band of N2H4 is at 1620 cm . Adsorbed
NH3 on γ -Al2O3 gives three IR bands at 1620, 1484, and
−
1
−1
1
260 cm . These bands are similar to those observed by
Ir/γ -Al2O3 catalyst because the band at 1484 cm is not
−1
Contour and Pannetier [9]. IR bands at 1620 and 1260 cm
observed when N2H4 is adsorbed on the surface of γ -Al2O3;

X. Chen et al. / Journal of Catalysis 224 (2004) 473–478
477
Fig. 4. IR spectra of (a) gaseous N H , (b) N H adsorbed on γ -Al O ,
2
4
2
4
2 3
Fig. 5. IR spectra of N H adsorption on 7.7 wt% Ir/γ -Al O catalysts and
2
4
2 3
(
c) NH adsorbed on γ -Al O , and (d) N H adsorbed on 7.7 wt%
3 2 3 2 4
8
.7 wt% Mo N/γ -Al O catalysts with different states.
2 2 3
Ir/γ -Al O at RT.
2
3
cant effect on the adsorption and reaction properties of fresh
Mo2N/γ -Al2O3 catalyst for hydrazine decomposition. Yang
et al. found that the surface of reduced passivated Mo2N/γ -
Al2O3 catalyst is in a highly oxidic form; i.e., most Mo sites
are in high valence state (+4). When the sample is renitrided
at a temperature as high as 873 K, the surface molybdenum
Table 1
Assignment of the IR bands from NH and N H adsorption on γ -Al O ,
3
2
4
2 3
7
.7 wt% Ir/γ -Al O , and 8.7 wt% Mo N/γ -Al O catalysts
2 3 2 2 3
Species Gas phase γ -Al O
Ir/γ -Al O Mo N/γ -Al O Assignment
2
3
2
3
2
2 3
NH
3337–3414
ν(NH)
3
1
628
1620
484
1260
1620
1484
1260
1620
1484
1260
δ(NH)
δ+
+
atoms can be reduced to Mo (0 < δ < 2) cations [12].
1
NH
4
950
δ(NH)
These similar catalytic results are probably because there
is no obvious difference of hydrazine adsorption and reac-
tion behaviors. These suggest that when the valence state
of Mo atom on the surface of Mo2N/γ -Al2O3 catalysts is
lower than or equal to +4, the Mo N/γ -Al O catalysts have
N H
2
3330–3287 3330–3287 3330–3287 3330–3287
ν(NH)
δ(NH)
4
1620
262
1601
1620
1260
1620
1260
1484
1
δ(NH)
+
1484
NH
4
2
2
3
catalytic activities close to those of Ir/γ -Al2O3 catalysts for
hydrazine decomposition.
−1
however, the band at 1484 cm is seen when N2H4 is ad-
sorbed on the Ir/γ -Al2O3 catalyst. The assignment of the IR
bands from NH3 and N2H4 adsorption on γ -Al2O3 and Ir/γ -
Al2O3 catalysts is listed in Table 1.
As seen in Fig. 6, CO adsorption on the fresh Mo2N/γ -
Al2O3 catalyst gives two characteristic IR bands at 2045
−1
and 2200 cm , corresponding to the adsorbed CO on the
surface Mo and N sites, respectively, forming linearly ad-
sorbed CO and NCO species [12]. When N2H4 is adsorbed
on the CO-preadsorbed Mo2N/γ -Al2O3 catalyst, the band at
As described before, the fresh and reduced passivated
Mo2N/γ -Al2O3 catalysts have a much higher activity than
the passivated Mo2N/γ -Al2O3 catalyst. N2H4 adsorptions
on passivated, reduced passivated, and fresh Mo2N/γ -Al2O3
catalysts were therefore studied using in situ IR spectra
−1
−1
2
200 shifts to 2191 cm , while the band at 2045 cm dis-
appears, accompanied by the appearance of a new band at
−1
2
240 cm . This band may be assigned to one or several of
(
shown in Fig. 5). N2H4 adsorption on passivated Mo2N/γ -
the following possible species:
Al2O3 catalyst gives IR bands at 3330–3287, 1620, and
−1
1
455 cm . However, the characteristic IR bands of N2H4
(1) NCO species,
adsorption on reduced passivated and fresh Mo2N/γ -Al2O3
(2) Mo–NC (or Mo–CN) species,
(3) Al–NC (or Al-CN) species, or
(4) Al–NCO species [13].
−1
catalysts appear at 3330, 1620, and 1484 cm , similar to
the adsorption of N2H4 on Ir/γ -Al2O3 catalysts. The band
of NH3 adsorption on the Brønsted acid site of fresh and
−
1
−1
reduced passivated Mo2N/γ -Al2O3 catalysts (1484 cm
)
At the same time, the bands at 1620 and 1484 cm were
seen which can be attributed to N H adsorption and reac-
−1
shifts to lower frequencies (1455 cm ) when hydrazine is
adsorbed on the passivated Mo2N/γ -Al2O3 catalyst. This
result is possibly due to the oxynitride layer on the sur-
face of passivated catalyst [22]. The oxygen atom on the
surface of passivated Mo2N/γ -Al2O3 catalyst has a signifi-
2
4
tion on the Mo N/γ -Al O catalyst. The disappearance of
2
2
3
−1
the band at 2045 cm , which is assigned to the adsorbed
CO on the Mo site of the Mo N/γ -Al O catalyst, suggests
2
2
3
that N2H4 is adsorbed mainly on the Mo site and then de-

478
X. Chen et al. / Journal of Catalysis 224 (2004) 473–478
temperature is up to 673 K, hydrazine decomposes into N2
and NH3 at first, and then the produced NH3 begins to dis-
sociate into N2 and H2.
The hydrazine adsorption and reaction behaviors over
Mo2N/γ -Al2O3 catalysts were investigated by in situ FT-
IR spectroscopy for the first time. It is found that IR spectra
of adsorbed hydrazine over the reduced passivated and fresh
Mo2N/γ −Al2O3 catalysts are also similar to those of Ir/γ -
Al2O3 catalysts. This provides new evidence for the similar-
ities of molybdenum nitride with platinum metal in catalysis.
With assistance of the IR technique, N2H4 adsorption tests
on the nitride surface, containing preadsorbed CO, suggest
that the adsorption occurs mainly on the Mo site of Mo2N/γ -
Al2O3 catalysts.
References
[
[
[
1] J.A.J. Rodrigues, G.M. Cruz, G. Bugli, M. Boudart, G. Djéga-
Mariadassou, Catal. Lett. 45 (1997) 1.
2] R. Brayner, G. Djéga-Mariadassou, G.M. Cruz, J.A.J. Rodrigues,
Catal. Today 57 (2000) 225.
3] J.B.O. Santos, G.P. Valença, J.A.J. Rodrigues, J. Catal. 210 (2002) 1.
Fig. 6. IR spectra of CO and N H coadsorbed on fresh 8.7 wt% Mo N/
2
4
2
γ -Al O catalyst at RT: (a) CO alone, (b) CO preadsorbed, then N H ,
2
3
2 4
(
c) N H preadsorbed, then CO.
2 4
composes to NH3 and N2 over it. When N2H4 is preadsorbed
[4] J.A.J. Rodrigues, G.M. Cruz, G. Djéga-Mariadassou, J.N. Hinckel,
PCT Int. Appl., WO 96/33803, 1996.
on the Mo2N/γ -Al2O3 catalyst, subsequently adsorbed CO
[5] X. Chen, T. Zhang, L. Xia, T. Li, M. Zheng, Z. Wu, X. Wang, Z. Wei,
Q. Xin, C. Li, Catal. Lett. 79 (2002) 21.
−1
−1
gives one band at 2191 cm and the band at 2045 cm
does not appear. This reveals that N2H4 adsorption on the
Mo2N/γ -Al2O3 catalyst is so strong that it covers the ad-
sorption site of the catalyst, so the IR band of CO adsorption
on the Mo sites is not observed. These results show that hy-
drazine is mainly adsorbed and decomposes on the Mo site
of the Mo2N/γ -Al2O3 catalyst.
[
6] X. Chen, T. Zhang, P. Ying, M. Zheng, W. Wu, L. Xia, T. Li, X. Wang,
C. Li, Chem. Commun. (2002) 288.
[7] W.E. Armstrong, L.B. Ryland, H.H. Voge, US patent 4 124 538, 1978.
[
8] W. Keim, in: G. Ertl, H. Knözinger, J. Weitkamp (Eds.), Handbook of
Heterogeneous Catalysis, VCH, Weinheim, 1997, p. 1795.
9] J.P. Contour, G. Pannetier, J. Catal. 24 (1972) 434.
[
[
[
[
[
[
10] B.J. Wood, H. Wise, J. Catal. 39 (1975) 471.
11] R. Maurel, J.C. Menezo, J. Catal. 51 (1978) 293.
12] S. Yang, C. Li, J. Xu, Q. Xin, Chem. Commun. (1997) 1247.
13] Z. Wu, Y. Chu, S. Yang, Z. Wei, C. Li, Q. Xin, J. Catal. 194 (2000) 23.
14] Z. Wu, C. Li, Z. Wei, P. Ying, Q. Xin, J. Phys. Chem. B 106 (2002)
4
. Conclusions
979.
The performances of molybdenum nitride catalysts with
[
15] G.W. Haddix, J.A. Reimer, A.T. Bell, J. Catal. 108 (1987) 50.
16] S. Mary, C. Kappenstein, S. Balcon, S. Rossignol, E. Gengembre,
Appl. Catal. A 182 (1999) 317.
different states for hydrazine decomposition have been stud-
ied in the microreactor. The catalytic activity for hydrazine
decomposition over passivated molybdenum nitride is much
lower than those of reduced passivated and fresh molybde-
num nitride catalysts. The reaction route of hydrazine de-
composition over a molybdenum nitride catalyst is similar
to that of a Ir/γ -Al2O3 catalyst. Below 673 K, hydrazine
mainly decomposes into N2 and NH3; when the reaction
[
[17] S. Balcon, C. Kappenstein, S. Mary, E. Gengembre, Appl. Catal. A
196 (2000) 179.
[
[
[
18] C. Liang, W. Li, Q. Xin, C. Li, Ind. Eng. Chem. Res. 39 (2000) 3964.
19] S.T. Oyama, Catal. Today 15 (1992) 179.
20] S.T. Oyama, J. Catal. 133 (1992) 358.
[21] P.A. Giguère, I.D. Liu, J. Chem. Phys. 20 (1952) 136.
22] M. Nagai, Y. Goto, A. Irisawa, S. Omi, J. Catal. 191 (2000) 128.
[