Dehydrogenation of propane to Propylene over Ga2O3 supported on mesoporous HZSM-5 in the presence of CO2

Article abstract of DOI:10.1002/cjoc.201090265

Dehydrogenation of propane to propylene over mesoporous HZSM-5 supported Ga₂O₃ catalysts in the presence of CO₂ has been investigated, and compared with that of conventional HZSM-5 supported one. The initial activity of the catalysts descends while the stability and selectivity to propylene improve with increasing the Si/Al ratios of the support. The optimal Si/Al ratio is 240 for the propylene yield reaching 21.7% after reaction for 50 h. The introduction of the mesopores improves the activity as well as the stability of the catalyst, due to the better transport of the reactant and product molecules caused by its hierarchical structure. The selectivity for bulky products such as aromatics is also increased. The promoting effect of CO₂ on the dehydrogenation reaction is observed.

Full text of DOI:10.1002/cjoc.201090265

FULL PAPER
Dehydrogenation of Propane to Propylene over Ga O
2
3
†
Supported on Mesoporous HZSM-5 in the Presence of CO2
Xie, Yuqing(谢裕青)
Hua, Weiming(华伟明)
Yue, Yinghong*(乐英红)
Gao, Zi(高滋)
Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan
University, Shanghai 200433, China
2 3
Dehydrogenation of propane to propylene over mesoporous HZSM-5 supported Ga O catalysts in the presence
of CO has been investigated, and compared with that of conventional HZSM-5 supported one. The initial activity
2
of the catalysts descends while the stability and selectivity to propylene improve with increasing the Si/Al ratios of
the support. The optimal Si/Al ratio is 240 for the propylene yield reaching 21.7% after reaction for 50 h. The in-
troduction of the mesopores improves the activity as well as the stability of the catalyst, due to the better transport
of the reactant and product molecules caused by its hierarchical structure. The selectivity for bulky products such as
aromatics is also increased. The promoting effect of CO on the dehydrogenation reaction is observed.
2
Keywords dehydrogenation, gallium, supported catalysis, mesoporous HZSM-5
16-19
Introduction
presence of CO2.
The propylene yield can stabilize
at about 22% in 100 h without obvious deactivation.
The superb stability can be explained by the decrease in
the amount of acid sites with medium to strong strength,
which can suppress the side reactions such as oli-
Propylene is an important raw material for producing
polypropylene, acrolein, acrylic acid and other useful
chemical products. The catalytic dehydrogenation of
propane to propylene has drawn intense attention due to
the growing demand for propylene. The present indus-
trial process using Cr O /Al O or Pt/Al O as catalysts
17
gomerization, cyclization, cracking and aromatization.
Further study shows that the stability can also be en-
hanced by the introduction of mesopores through
steaming, due to the promotion of desorption and diffu-
2
3
2
3
2
3
is not optimal because of the quick deactivation of the
1
,2
catalysts during the reaction. The oxidative dehydro-
genation of propane by oxygen has been proposed as an
alternative process. However, the over-oxidation of
propane to carbon dioxide can not be avoided during the
18
sion of the propylene.
Mesoporous ZSM-5 is a kind of zeolite containing
both wormhole-like mesopores as well as micropores of
MFI structure. It was synthesized by adding an amphi-
philic organosilane as surfactant during the formation of
3
,4
reaction, leading to low selectivity to propylene. Car-
bon dioxide is a mild oxidant for many oxidation reac-
tions. Previous researches show that carbon dioxide can
also promote dehydrogenation of propane to propylene
by the reversed water-gas shift reaction over some sup-
20
MFI units. This novel zeolite has been proved to ex-
hibit better activity and higher resistance to deactivation
as compared with conventional ZSM-5 in some reac-
tions due to its hierarchical structure, which improves
5
-9
ported Cr O , ZnO and Ga O catalysts. Since carbon
20-28
2
3
2
3
the mass transfer process during the reactions.
This
dioxide is one of the major greenhouse gases, the utili-
zation of carbon dioxide is attractive not only economi-
cally but also ecologically.
advantage may also play a part in dehydrogenation of
propane.
In this work, Ga O3 supported on mesoporous
2
It is well known that Ga-loaded ZSM-5 is a good
catalyst for aromatization of ethane and propane. The
process is regarded as a bifunctional mechanism. Gal-
lium oxide is responsible for catalyzing the dehydroge-
nation step while Bronsted acid sites for the oligomeri-
HZSM-5 with different Si/Al ratios were prepared.
Their catalytic performance in dehydrogenation of pro-
pane to propylene in the presence of CO was investi-
2
gated and compared with that of conventional ZSM-5
supported ones. The effects of Si/Al ratio, Ga O con-
1
0-15
2
3
zation step.
Our recent work shows that high Si/Al
tent, the introduction of mesopore and CO were also
2
ratio HZSM-5 supported Ga O is highly active and
2
3
studied.
stable in dehydrogenation of propane to propylene in the
*
E-mail: yhyue@fudan.edu.cn; Tel.: 0086-021-65642409; Fax: 0086-021-65641740.
Received June 10, 2010; revised September 1, 2010; accepted September 2, 2010.
Project supported by National Basic Research Program of China (No. 2006CB806103), the National Natural Science Foundation of China (Nos.
2
0633030, 20773027 and 20773028) and the Science & Technology Commission of Shanghai Municipality (No. 08DZ2270500).
†
Dedicated to the 60th Anniversary of Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
Chin. J. Chem. 2010, 28, 1559— 1564 © 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1559

Xie et al.
FULL PAPER
Experimental
raised from 120 to 600 ℃ at a rate of 10 ℃/min, and
the ammonia desorbed was collected in a liquid nitrogen
trap and detected by an on-line gas chromatograph (GC)
equipped with a TCD.
Thermal gravimetric analysis (TGA) was conducted
in flowing air on a Perkin Elmer TGA 7 to determine the
amount of coke deposited on the catalyst after reaction.
Catalyst preparation
Mesoporous ZSM-5 with different Si/Al ratios were
2
0
prepared following the procedures in the literature. In
a typical procedure, 0.0209 g sodium aluminate, 1.1 g
tetrapropylammonium bromide (TPABr), and 0.8 g
NaOH were dissolved in 135 g H
.57 g tetraethylorthosilicate (TEOS) and 1.19 g [3-(tri-
methoxysilyl)propyl]octcyldimethylammonium chloride
TPOAC) was slowly dripped into this solution. After
2
O. Then a mixture of
Catalytic activity tests
8
The activities of the samples toward cumene crack-
ing were tested in a pulse microreactor. The catalyst
load for the tests was 20 mg, and the catalyst was pre-
heated at 350 ℃ for 2 h before reaction. Hydrogen
with a flow rate of 40 mL/min was used as the carrier
gas. The reactions were conducted at 250 ℃, and 1 µL
cumene was injected for each test. The products were
analyzed by an on-line GC equipped with a TCD.
Catalytic tests for propane dehydrogenation were
performed at 600 ℃ in a fixed-bed flow microreactor
at atmospheric pressure. The catalyst load was 200 mg,
and it was activated at 600 ℃ for 1 h in nitrogen flow
prior to the reaction. The gas reactant contained 2.5
vol% propane, 5 vol% carbon dioxide and balancing
nitrogen. For dehydrogenation of propane in the absence
(
stirring at room temperature for 2 h, the mixture gel was
transferred into a stainless steel autoclave lined with
Teflon and crystallized at 170 ℃ for 2 d. The products
were filtered and washed, then dried at 100 ℃, finally
calcinated at 550 ℃ for 6 h in air. These mesoporous
－
1
4 3
ZSM-5 were exchanged with 1 mol•L NH NO solu-
tion for three times and finally calcinated in air at 600
℃
for 3 h into the H-form. The attained mesoporous
solution using
an incipient wetness method. The impregnated samples
HZSM-5 were impregnated by Ga(NO
3
)
2
were dried at 100 ℃ and calcined at 600 ℃ for 6 h in
2 3
air. The obtained catalysts were denoted as Ga O /M-
HZSM-5(x), in which x represents the bulk molar ratio
of Si/Al. The content of Ga
wt%, unless otherwise noted.
Conventional HZSM-5 supported Ga
were prepared according to the procedures in another
2 3
O in all the catalysts was 5
2
of CO , the gas reactant contained 2.5 vol% propane
and balancing nitrogen. The total flow rate of the gas
reactant is 20 mL/min. The hydrocarbon reaction prod-
ucts were analyzed using an on-line GC equipped with a
2
3
O catalysts
1
8
2 3
literature and denoted as Ga O /HZSM-5(x).
6-m packed column of Porapak Q and a FID. The gas
products, including CO and CO , were analyzed on-line
by another GC equipped with a 2-m packed column of
carbon molecular sieve 601 and a TCD.
2
Catalyst characterization
X-ray diffraction (XRD) of the catalysts was carried
out on a Bruker D8-Advanced X-ray diffractometer us-
ing nickel-filtered Cu-Kα radiation at 40 kV and 40 mA.
The bulk Si/Al ratio of the mesoporous ZSM-5 was
measured by X-ray fluorescence spectrum (XRF) on
Bruker-AXS S4 Explorer.
Results and discussion
Catalyst preparation and characterization
The mesoporous HZSM-5 with different Si/Al ratios
were synthesized using TPOAC as a template. Their
XRD patterns were measured and shown in Figure 1.
Five diffraction peaks characteristic of MFI structure at
The N
ured on a Micromeritics ASAP2000 instrument at liquid
temperature. Specific surface areas of the samples
2
adsorption/desorption isotherms were meas-
N
2
were calculated from the adsorption isotherms by BET
method, and pore size distributions from the adsorption
isotherms by BJH method.
2
θ＝8.0°, 8.9°, 23.1°, 23.3° and 24.0° were observed on
the patterns of all the samples. The relative crystallinity
of MFI sample was determined by comparing the sum
of the intensities of its peaks at d＝3.851, 3.823, 3.798,
2
7
Al MAS NMR measurements were performed on a
Bruker DSX-300 spectrometer at a resonance frequency
of 78.2 MHz. Spectra were recorded at a spinning rate
of 12 kHz, a pulse length of 0.31 µs and a delay time of
3.732 and 3.711 nm with that of the reference sample.
The result shows that all those materials have similar
degrees of crystallization except for the one with a Si/Al
ratio of 78, whose crystallinity is a bit higher than that
of the others. No peaks corresponding to gallium oxide
are observed on the XRD patterns of supported catalysts
0.5 s. All the samples were hydrated in a desiccator over
a saturated NaCl solution for 3 d prior to the measure-
ments.
The surface acidity was measured by tempera-
ture-programmed desorption of NH
(not shown here), indicating that gallium oxide is well
3 3
(NH -TPD) in a
dispersed on all the supports.
flow-type fixed-bed reactor at ambient pressure. A
The N adsorption/desorption isotherms of the cata-
2
1
00-mg sample was preheated at 550 ℃ for 2 h, and
lysts were measured. All are typical type IV isotherms
except for the one with a Si/Al ratio of 78, as shown in
Figure 2A, which shows that most catalysts have very
regular mesoporous channels after the gallium oxide
then cooled to 120 ℃ in flowing helium. At this tem-
perature, sufficient pulses of ammonia were injected
until adsorption saturation occurred, followed by purg-
ing with helium for 2 h. The temperature was then
1
560
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Chin. J. Chem. 2010, 28, 1559— 1564

2 3
Dehydrogenation of Propane to Propylene over Ga O Supported on HZSM-5
pore diameter of the catalysts were also summarized in
Table 1. The BET specific surface areas of mesoporous
HZSM-5 supported catalysts are in the range of 363 to
2
3
0
85 m /g, the pore volumes are in the range of 0.20 to
3
.27 cm /g, showing that the channels in the mesopor-
ous HZSM-5 supports are not blocked by supported
Ga
2
3
O .
2
7
Figure 3 depicts the Al MAS NMR spectra of the
samples. An intense line at δ 55 from 4-coordinate alu-
minum in the ZSM-5 framework and a very weak line at
δ 0 from extra-framework 6-coordinate aluminum were
observed in all the samples, indicating that the majority
of the Al species have been incorporated into the
framework of ZSM-5, which is exactly the same as that
in conventional ZSM-5.
Figure 1 XRD patterns of mesoporous HZSM-5 with different
Si/Al ratios: (a) M-HZSM-5(78), (b) M-HZSM-5(144), (c)
M-HZSM-5(173), (d) M-HZSM-5(240), (e) M-HZSM-5(307).
supporting. This was proved by the pore size distribu-
tions shown in Figure 2B.
The bulk Si/Al ratio of the HZSM-5 support measured
by XRF was presented in Table 1. The bulk Si/Al ratio is
generally much smaller than that of the initial gel, show-
ing that Al is probably much easier to be incorporated
into the framework than Si during the synthesis of
mesoporous ZSM-5 with high Si/Al ratio. The specific
surface area, pore volume and the most probable
2
7
Figure 3
different Si/Al ratios: (a) M-HZSM-5(78), (b) M-HZSM-5(144),
c) M-HZSM-5(173), (d) M-HZSM-5(240), (e) M-HZSM-5(307).
Al MAS NMR spectra of mesoporous HZSM-5 with
(
Acidity measurements
The acidity of the catalysts was measured by
NH
gether with that of Ga
There is a broad asymmetric NH
the TPD profiles of all Ga supported catalysts. The
3
-TPD and results were summarized in Table 2, to-
/HZSM-5(180) for comparison.
desorption peak on
2
O
3
3
2
O
3
acidity of the mesoporous ZSM-5 supported catalysts
decreases with increasing the Si/Al ratio of the support.
Not only the total amount of acid sites but also that of
medium to strong acid sites (expressed as the amount of
NH
3
desorbed within the temperature zone of 350—600
℃
) decrease sharply, quite similar to those of Ga O
catalysts supported on the conventional HZSM-5.
Meanwhile, the total amounts of acid sites as well as
2 3
that of medium to strong acid sites on Ga
2 3
O /M-
HZSM-5 catalyst are much lower than that on Ga
2
O
3
catalyst supported on the conventional HZSM-5 with
similar Si/Al ratio. Since the Si/Al ratio of the support is
so high that the acid sites of the support itself is very
low, the above acidity difference comes from the dis-
persed gallium oxides, caused by the different interac-
tion between the gallium oxide and the supports after
the introduction of mesoporous channels. Similar results
Figure 2 N adsorption isotherms (A) and pore size distribution
2
(
B) of the catalysts: (a) Ga O /M-HZSM-5(78), (b)
2 3
Ga O /M-HZSM-5(144), (c) Ga O /M-HZSM-5(173), (d)
2
3
2
3
1
6,17
Ga O /M-HZSM-5(240), (e) Ga O /M-HZSM-5(307). The iso-
2
3
2
3
were observed before.
The catalytic activities of these supported gallium
therms (b), (c), (d) and (e) were vertically offset by 50, 100, 150
3
and 200 cm /g, respectively.
Chin. J. Chem. 2010, 28, 1559— 1564
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1561

Xie et al.
FULL PAPER
Table 1 Composition and textural properties of the catalysts prepared
Si/Al ratio
Surface area/
Pore volume/
(cm •g )
Mesopore volume/
Mesopore diameter/
Catalyst
－
－
－
1
2
1
3
1
3
a
b
(
m •g )
(cm •g )
nm
Gel Bulk
Ga
2
2
O
O
3
3
/M-HZSM-5(78)
/M-HZSM-5(144)
200
300
400
500
600
78
363
336
344
385
385
0.20
0.23
0.24
0.22
0.12
0.19
0.21
0.18
0.23
2.3
2.2
2.1
2.1
2.1
Ga
144
173
240
307
Ga O /M-HZSM-5(173)
2
3
Ga O /M-HZSM-5(240)
2
3
Ga
2
O
3
/M-HZSM-5(307)
0.27
a
b
Calculated from the amount of NaAlO
2
and TEOS added in the reactant gel. Determined by XRF.
oxide catalysts toward cumene cracking, a typical strong
acid catalyzed reaction, have been investigated. The
results are given in Table 2. The activity of these
mesoporous ZSM-5 supported catalysts decreases with
the increase of the Si/Al ratio, and is lower than that of
conventional HZSM-5 supported one with similar Si/Al
3
ratio, which is consistent with NH -TPD results.
3
Table 2 NH -TPD data and cumene cracking results of various
catalysts
3
Amount of desorbed NH /
Conversion
of cumene/
%
－
1
(mmol•g )
Catalyst
1
20—350 350—600
Total
℃
℃
Ga
2
O
3
/M-HZSM-5(78)
0.15
0.19
0.11
0.09
0.07
0.06
0.15
0.34
0.18
0.14
0.11
0.09
0.25
27.6
22.2
21.2
20.5
19.0
24.6
Ga
2
3
O /M-HZSM-5(144) 0.08
Ga O /M-HZSM-5(173) 0.05
2
3
Ga
2
O
3
/M-HZSM-5(240) 0.04
Ga O /M-HZSM-5(307) 0.03
2
3
Ga O /HZSM-5(180)
0.10
2
3
Catalytic activity
The dehydrogenation of propane in the presence of
Figure 4 Propane conversion (A) and propylene yield (B) on
the catalysts as
a
function of reaction time: (■)
CO
2
was carried out at 600 ℃ over various mesopor-
Ga O /M-HZSM-5(78), (●) Ga O /M-HZSM-5(144), (▲)
Ga O /M-HZSM-5(173), (▼) Ga O /M-HZSM-5(240), (◄)
2 3 2 3
2
3
2
3
ous HZSM-5 supported gallium oxide catalysts. The
variation of propane conversion versus time on stream
for these catalysts was illustrated in Figure 4A. The ini-
tial propane conversion decreases as the Si/Al ratio in-
creases, due to the decrease of the acid sites on the cata-
Ga O /M-HZSM-5(307).
2
3
tions besides the dehydrogenation to produce more
by-products such as aromatics. Thus, 5% is an optimal
content in our present work, which is similar to the re-
2 3
lysts, quite similar to the results over Ga O /HZSM-5
1
6
catalysts. Meanwhile, the selectivity to propylene
increases with the increase of Si/Al ratio. Thus, the
initial propylene yield has the sequence of
sult of conventional HZSM-5 supported Ga
The effect of CO
The effect of CO
2 3
O .
2
Ga
Ga
Ga
2
2
2
O
O
O
3
3
3
/M-HZSM-5(240) ＞ Ga
2
O
3
/-HZSM-5(173) ≈
2
addition on the dehydrogenation
2 3
of propane over Ga O /M-HZSM-5(240) catalyst was
/M-HZSM-5(144) ＞ Ga
2
O
3
/M-HZSM-5(307) ≈
/M-HZSM-5(78) as displayed in Figure 4B.
also investigated, and the results were shown in Figure 5
and Table 4. The amount of coke determined by TG was
also contained. The promoting effect of carbon dioxide
on the reaction was observed. The initial propane con-
version increases from 48.6% to 57.5% by the introduc-
2 3 2 3
The effect of Ga O loading over Ga O /M-HZSM-
5
(240) was shown in Table 3. The activity of the cata-
lyst increases sharply when the content is raised from
% to 5%. However, only a little improvement can be
observed when the loading amount is increased from
% to 7%. In the same time, raising the Ga loading
3
2
tion of CO . Despite of the reduction in the propylene
5
2
O
3
selectivity, an improvement in the initial propylene yield
is also obtained. This enhancement can be attributed to
the reverse water gas shift reaction, which accelerates
also has a negative effect on the propylene selectivity,
since too many active sites would enhance the side reac-
1
562
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Chin. J. Chem. 2010, 28, 1559— 1564

2 3
Dehydrogenation of Propane to Propylene over Ga O Supported on HZSM-5
Table 3 Reaction data over Ga
2
O
3
2 3
/M-HZSM-5(240) with different Ga O loadings
a
Loading/
wt%
Selectivity /%
a
a
Conversion /%
Yield of C H /%
3 6
CH
4
C
2
H
4
C
2
H
6
C
3
H
6
Aromatics
36.4 (32.8)
47.9 (44.8)
48.1 (48.2)
3
5
7
46.8 (43.2)
57.5 (53.0)
62.0 (56.6)
3.8 (3.4)
2.7 (2.4)
3.1 (2.4)
14.3 (15.0)
9.0 (9.8)
0.7 (0.5)
0.2 (0.2)
0.4 (0.4)
44.7 (48.3)
40.2 (42.7)
38.0 (39.6)
20.9 (20.9)
23.1 (22.6)
23.6 (22.4)
10.3 (9.5)
a
The values outside and inside the parenthesis are the data obtained at 1 and 10 h, respectively.
reaction by better transport of the reactant or product
molecules due to its hierarchical structure.
Figure 5 Propane conversion (A) and propylene yield (B) of
Ga O /M-HZSM-5(240) (○) in the presence of CO , and (■) in
2
3
2
2
the absence of CO .
Figure 6 Propane conversion (A) and propylene yield (B) of (■)
Ga O /M-HZSM-5(173) and (○) Ga O /HZSM-5(180) as a func-
tion of reaction time.
the formation of the dehydrogenation products by
2
3
2
3
9
,16
transforming H
It can also be seen that the stability of the catalysts is
improved after the addition of CO . The initial activity
of Ga /M-HZSM-5(240) catalyst dropped about
2.4% within 30 h in the absence of CO , but when CO
2
with CO
2
into CO and H
2
O.
2
However, the propylene selectivity on the mesopor-
ous catalyst is relatively lower. Thus, no significant im-
provement in propylene yield was obtained after the
introduction of the mesopores. Meanwhile, more aro-
matics were obtained on the mesoporous catalyst, indi-
cating that the existence of mesoporous channel pro-
moted the possibility of forming bulky products via side
reactions such as oligomerization, cyclization and aro-
matization. GC-MS measurements show that the main
component of the aromatic products is benzene, toluene
and xylene, usually over 90%, which is also valuable in
the chemical industry, as well as propylene.
2
O
3
2
2
2
was introduced, only 16.5% was dropped within the
same period. This improvement can be attributed to the
suppression of coke formation (Table 4) coming from
9
,16
two aspects:
elimination of coke by the Boudouard
reaction and promotion of desorption of propylene from
the catalyst surface.
The effect of mesoporosity
Figure 6 illustrated the difference of the catalytic
behavior between the mesoporous ZSM-5 supported
gallium oxide and conventional ZSM-5 supported one.
The details were listed in Table 4. It can be seen that the
The stability of the catalyst is also improved by the
introduction of the mesopores. Thus, the steady propyl-
ene yield of Ga O /M-HZSM-5(173) is a bit higher than
2
3
conversion of propane over Ga
2
O
3
/M-HZSM-5(173) is
2 3
that over Ga O /HZSM-5(180). TG results show that
less coke is formed on the mesoporous catalyst (see Ta-
ble 4), which may also have something to do with the
higher than Ga /HZSM-5(180) despite there is less
2
O
3
acid sites on the former one. This indicates that the in-
troduction of the mesoporous channel can promote the
Chin. J. Chem. 2010, 28, 1559— 1564
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Xie et al.
FULL PAPER
Table 4 Reaction data and coke amount over various catalysts in the presence or absence of CO
2
a
Selectivity /%
Coke/
wt%
a
a
Catalyst
Conversion /%
3 6
Yield of C H /%
CH
4
C
2
H
4
C
2
H
6
C
3
H
6
Aromatics
b
c
b
Ga
Ga
Ga
2
2
2
2
O
O
O
O
3
3
3
3
/M-HZSM-5(240)
/M-HZSM-5(240)
/M-HZSM-5(173)
57.5 (48.0)
48.6 (37.7)
59.2 (52.8)
48.9 (37.5)
3.0 (2.2) 10.1 (8.7) 0.2 (0.1) 40.2 (45.2) 46.5 (43.7)
2.9 (2.5) 9.8 (10.1) 0.2 (0.2) 45.2 (53.3) 41.9 (33.9)
3.2 (3.5) 10.8 (14.5) 0.8 (0.5) 38.1 (41.3) 47.2 (40.2)
23.1 (21.7)
22.0 (20.1)
22.6 (21.8)
0.82
0.92
0.97
1.27
b
Ga
/HZSM-5(180)
3.1 (2.7) 10.2 (10.8) 0.2 (0.2) 45.1 (53.5) 41.5 (32.8)
22.0 (20.1)
a
b
c
The values outside and inside the parenthesis are the data obtained at 1 and 30 h, respectively; in the presence of CO
of CO2.
2
;
in the absence
better transport of the product molecules via mesopor-
ous channels, besides the fact that there is less acid sites
on Ga O /M-HZSM-5(173).
2 3
7
8
Liu, L.; Li, H.; Zhang, Y. Catal. Commun. 2007, 8, 565.
Ren, Y.; Zhang, F.; Hua, W.; Yue, Y.; Gao, Z. Catal. Today
2009, 148, 316.
9
0
1
Zheng, B.; Hua, W.; Yue, Y.; Gao, Z. J. Catal. 2006, 239,
4
70.
Guisnet, M.; Gnep, N. S.; Alario, F. Appl. Catal. A: Gen.
992, 89, 1.
Conclusion
1
1
Dehydrogenation of propane in the presence of CO
was investigated over a series of Ga O catalysts sup-
2 3
2
1
Himei, H.; Yamadaya, M.; Kubo, M.; Vetrivel, R.; Bro-
clawik, E.; Miyamoto, A. J. Phys. Chem. 1995, 99, 12461.
Guisnet, M.; Gnep, N. S. Catal. Today 1996, 31, 275.
Gonzales, N. O.; Chakraborty, A. K.; Bell, A. T. Top. Catal.
ported on the mesoporous HZSM-5 with different Si/Al
ratios. Their catalytic behavior has been compared with
that on conventional HZSM-5 supported one. The initial
activity of mesoporous HZSM-5 supported catalysts
decreases with increasing the Si/Al ratio of the support,
while the selectivity to propylene improves. The intro-
duction of the mesoporous channels can promote the
transport of the reactant and product molecules, leading
to an enhancement in activity and stability of the cata-
lysts. However, the selectivity to propylene decreases,
since the existence of mesopores is more suitable for
producing bulky products such as aromatics. Benzene,
toluene and xylene are the main by-products, which are
also valuable in chemical industry. The promoting effect
1
1
2
3
1
999, 9, 207.
Frash, M. V.; van Santen, R. A. J. Phys. Chem. A 2000, 104,
468.
1
4
5
2
1
Kazansky, V. B.; Subbotina, I. R.; Rane, N.; van Santen, R.
A.; Hensen, E. J. M. Phys. Chem. Chem. Phys. 2005, 7,
3
088.
16
17
18
19
20
Xu, B.; Zheng, B.; Hua, W.; Yue, Y.; Gao, Z. Stud. Surf. Sci.
Catal. 2007, 170, 1072.
Xu, B.; Li, T.; Zheng, B.; Hua, W.; Yue, Y.; Gao, Z. Catal.
Lett. 2007, 119, 283.
Ren, Y.; Hua, W.; Yue, Y.; Gao, Z. Chem. J. Chin. Univ.
of CO
over these mesoporous catalysts by transforming H
with CO into CO and H O through the reverse wa-
ter-gas shift reaction. The catalytic stability is also en-
hanced by the addition of CO to the feed gas due to the
2
on the dehydrogenation reaction is observed
2
009, 30, 1162 (in Chinese).
2
Ren, Y.; Hua, W.; Yue, Y.; Gao, Z. React. Kinetics Catal.
Lett. 2008, 95, 113.
Choi, M.; Cho, H. S.; Srivastava, R.; Venkatesan, C.; Choi,
D.; Ryoo, R. Nature Materials 2006, 5, 718.
Sun, Y. Y.; Prins, R. Appl. Catal. A 2008, 336, 11.
Sun, Y. Y.; Prins, R. Angew. Chem. Int. Ed. 2008, 47, 8478.
2
2
2
suppression of coke formation.
2
2
1
2
References
23 Kim, J.; Choi, M.; Ryoo, R. J. Catal. 2010, 269, 219.
24
25
26
27
28
Wang, Y.; Ma, L. R.; Zhu, N.; Chen, F. Q.; Zhan, X. L. Prog.
Chem. 2009, 21, 1722.
Jin, M. J.; Taher, A.; Kang, H. J.; Choi, M.; Ryoo, R. Green
Chem. 2009, 11, 309.
Zhao, Z. L.; Liu, Y. M.; Wu, H. H.; Li, X. H.; He, M. Y.; Wu,
P. Microporous Mesoporous Mater. 2009, 123, 324.
Srivastava, R.; Iwasa, N.; Fujita, S.; Arai, M. Chem. Eur. J.
1
2
3
4
Barias, O. A.; Holmen, A.; Blekkan, E. A. J. Catal. 1996,
58, 1.
Gascon, J.; Tellez, C.; Herguido, J.; Menendez, M. Appl.
Catal. A: Gen. 2003, 248, 105.
Sugiyama, S.; Hashimoto, T.; Tanabe, Y.; Shigemoto, N.;
Hayashi, H. J. Mol. Catal. A: Chem. 2005, 227, 255.
Creaser, D. C.; Andersson, B.; Hudgins, R. R.; Silveston, P.
L. Cana. J. Chem. Eng. 2000, 78, 182.
1
2
008, 14, 9507.
Perez-Ramirez, J.; Christensen, C. H.; Egeblad, K.;
5
6
Takahara, I.; Saito, M. Chem. Lett. 1996, 973.
Michorczyk, P.; Ogonowski, J. Appl. Catal. A: Gen. 2003,
Christensen, C. H.; Groen, J. C. Chem. Soc. Rev. 2008, 37,
2
530.
2
51, 425.
(
E1006101 Sun, H.)
1
564
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