Transformation of methane to propylene: A two-step reaction route catalyzed by modified CeO2 nanocrystals and zeolites

Article abstract of DOI:10.1002/anie.201104071

Propylene from methane: The transformation of methane to propylene has been realized in a two-step route via CH₃Cl or CH₃Br. CeO ₂ serves as an efficient and stable catalyst for the oxidative chlorination and bromination of methane to CH₃Cl and CH ₃Br. In the second step, a modified zeolite is highly a selective and stable catalyst for the conversion of CH₃Cl or CH₃Br into propylene. Copyright

Full text of DOI:10.1002/anie.201104071

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Angewandte
Communications
DOI: 10.1002/anie.201104071
Propylene Synthesis
Transformation of Methane to Propylene: A Two-Step Reaction Route
Catalyzed by Modified CeO2 Nanocrystals and Zeolites**
Jieli He, Ting Xu, Zhihui Wang, Qinghong Zhang,* Weiping Deng, and Ye Wang*
The utilization of methane, which is the main constituent of
natural gas, coal-bed gas, shale gas, and the vast gas hydrate
resources, for the production of chemicals is one of the most
important research targets in catalysis. The current technol-
ogy for chemical utilization of methane involves high-temper-
ature steam reforming to produce syngas, and the subsequent
conversion of syngas to methanol, followed by methanol
transformation. However, steam reforming of methane is an
energy- and cost-intensive process. The direct transformation
of methane to valuable chemicals would be the most desirable
route, however, despite many efforts it remains difficult to
achieve.[1] The development of novel catalytic routes for the
transformation of methane is of high significance from both
practical and fundamental points of view.
Monohalogenomethanes (CH3Cl or CH3Br) could be
alternative platform molecules for the conversion of CH4 to
chemicals. Olah et al. reported the catalytic monohalogena-
tion of CH4 by Cl2 or Br2 over supported superacids or noble
metals, followed by hydrolysis of methyl halides to methanol
and dimethyl ether.[2] Zhou et al. disclosed the conversion of
CH4 or C2H6 to alkyl bromides by using Br2, and the
subsequent conversion to oxygenates through stoichiometric
reactions with metal oxides.[3] GRT, Inc. developed a technol-
ogy for the transformation of CH4 to various products,
particularly liquid hydrocarbon fuels, through the reaction
with Br2 via methyl bromides, and claimed that this is a cost-
effective route.[4] In these processes, the generated HCl, HBr,
or metal bromides must be oxidized to Cl2 or Br2 to complete
the catalytic cycle. HBr was demonstrated to be useful for the
oxidative bromination of CH4 in the presence of O2 instead of
Br2 over supported Ru or Rh catalysts,[5] but the high cost and
limited availability of noble metals may hinder the large-scale
application of this system. Zn-MCM-48-supported hydrated
dibromo(dioxo)molybdenum(VI), which might generate Br2
during reaction, catalyzed the oxidation of CH4 to methanol
and dimethyl ether, but the long-term stability of this system
was not confirmed.[6] SiO2-supported FePO4 was stable for the
oxidative bromination of CH4, which provided CH3Br with
a selectivity of approximately 50%.[7] Only a few studies have
been devoted to the oxidative chlorination of CH4 to CH3Cl,
although HCl is cheaper than HBr. Lercher and co-workers
found that LaCl3 was a superior catalyst for this reaction,
which provided CH3Cl with a selectivity of around 55% at
a CH4 conversion of 12% at 748 K.[8]
Herein, we present a novel catalytic route for the
conversion of CH4 to propylene via monohalogenomethane.
Propylene is one of the most important bulk chemicals, and
currently, it is mainly produced as a coproduct of ethylene
through the cracking of naphtha. However, the demand for
propylene is growing much faster than the demand for
ethylene.[9] The development of novel routes for the produc-
tion of propylene, for example, dehydrogenation of pro-
pane,[9] conversion of methanol to propylene,[10] and conver-
sion of ethylene to propylene,[11] has attracted much attention.
Our two-step route from CH4 to propylene can be expressed
by Equations (1) and (2). Both reactions are exothermic (see
the Supporting Information for details). The net reaction is
the oxidation of CH4 by O2 to propylene and H2O [Eq. (3)].
The development of efficient catalysts for the two reaction
steps is the key to this new route.
We have investigated the catalytic performances of
a variety of non-noble metal catalysts for the oxidative
chlorination and bromination of CH4. Among various metal
oxides, CeO2 is the most efficient catalyst for both reactions
(see Tables S1 and S2 in the Supporting Information). CeO2
was a particularly good catalyst for the oxidative chlorination
of CH4; a CH3Cl selectivity of 66% and a CH4 conversion of
12% were attained at 753 K. A higher temperature was
required to obtain a similar CH4 conversion by the oxidative
bromination of CH4; CH4 conversion and CH3Br selectivity
were 16% and 74%, respectively, with CeO2 at 833 K.
Besides CH3Cl and CH3Br, CH2Cl2 and CH2Br2 were also
formed in both reactions, but their selectivities were lower.
CHCl3 or CHBr3 and CCl4 or CBr4 were not formed. The
product distribution for the oxidative chlorination of CH4
over CeO2 is very different from that observed for the radical
[*] J. He,[+] T. Xu,[+] Z. Wang, Prof. Dr. Q. Zhang, Dr. W. Deng,
Prof. Dr. Y. Wang
State Key Laboratory of Physical Chemistry of Solid Surfaces and
National Engineering Laboratory for Green Chemical Productions of
Alcohols, Ethers, and Esters
College of Chemistry and Chemical Engineering
Xiamen University, Xiamen 361005 (China)
E-mail: zhangqh@xmu.edu.cn
wangye@xmu.edu.cn
[+] These authors contributed equally to this work.
[**] This work was supported by the National Basic Research Program of
China (2010CB732303) and the NSF of China (21033006, 20873110,
and 20923004).
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201104071.
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Table 1: Rates of methane conversion and product formation over CeO2
nanocrystals with different morphologies and nanoparticles.[a]
reaction of CH4/Cl2, the main products of which were CH2Cl2
and CHCl3.[2]
Recent studies have shown that the redox and catalytic
properties of CeO2 may be dependent on morphologies.[12]
Understanding the effect of morphologies or exposed crystal
planes of well-defined CeO2 nanocrystals may provide an
opportunity to unravel the nature of active structures, and is
helpful for the rational design of more efficient catalysts. We
have studied the effect of the morphology of CeO2 on its
catalytic behaviors in the oxidative chlorination and bromi-
nation of CH4. We synthesized CeO2 nanocrystals with the
same cubic fluorite phase but different morphologies (nano-
rod, nanocube, and nano-octahedron) by hydrolysis of
cerium(III) salts combined with a hydrothermal treat-
ment.[12b] Measurements by transmission electron microscopy
(TEM) and scanning electron microscopy (SEM) showed the
uniform morphology of our synthesized CeO2 nanocrystals
(Supporting Information, Figure S1). The sizes of the nano-
rods, nanocubes, and nano-octahedra were (9 Æ 4) ꢀ (60–
300) nm, 10–80 nm, and 100–200 nm, respectively. Their
specific surface areas measured by N2 adsorption at 77 K
were 99, 23, and 21 m2 gÀ1, respectively. High-resolution TEM
(HRTEM) images showed that the nanorods exposed the
{110} and {100} planes with fractions of 51% and 49%,
respectively, while the nanocubes and the nano-octahedra
exposed the {100} and {111} planes with nearly 100%,
respectively (Supporting Information, Figure S2). For com-
parison, CeO2 nanoparticles with a mean diameter of
approximately 9 nm and a surface area of 146 m2 gÀ1 were
also synthesized, and HRTEM images showed that the CeO2
nanoparticles mainly exposed {111} planes (Supporting Infor-
mation, Figure S3).
Catalyst
Exposed
planes
Surface
area[b]
r(CH4)
r(CH3X)
[mmolmÀ2 hÀ1
]
[mmolmÀ2 hÀ1
]
[m2 gÀ1
]
A) Oxidative chlorination
Nanorod
{100} +
{110}
{100}
54
0.93
0.64
Nanocube
Nano-
octahedron
Nanoparticle {111}
B) Oxidative bromination
20
19
0.72
0.69
0.54
0.45
{111}
68
52
0.57
0.63
0.38
0.42
Nanorod
{100} +
{110}
{100}
Nanocube
Nano-
octahedron
18
10
0.62
0.54
0.47
0.38
{111}
Nanoparticle {111}
64
0.50
0.32
[a] Reaction conditions: A) T=753 K, CH4/HCl/O2/N2/He=4/2/1/1.5/
1.5, total flow rate=40 mLminÀ1; B) T=873 K, 40 wt% HBr aqueous
solution 4.0 mLhÀ1, CH4/O2/N2 =4/1/1 (flow rate=15 mLminÀ1).
[b] The specific surface areas listed here are those measured for the used
catalysts. X=Cl,Br.
amount of catalyst (Figure 1). Moreover, CH3Cl or CH3Br
selectivity depended on the morphology of CeO2. The
nanocubes, which exposed {100} planes, were the most
selective catalysts, while the nano-octahedra and nanoparti-
cles exposing mainly {111} planes were the least selective for
the CH3Cl or CH3Br formation.
We performed in situ Raman spectroscopic studies for
CeO2 catalysts under the reaction conditions. Only Raman
bands ascribed to CeO2 were observed, and no CeCl3 or
We confirmed that the morphologies of the CeO2 nano-
crystals were sustained after the oxidative chlorination and
bromination of CH4, although their sizes changed, particu-
larly the length of the nanorods and the size of the nano-
particles (Supporting Information, Figure S3C and Fig-
ure S4). We have compared the intrinsic rates of CH4
conversion (r(CH4)) and product formation (r(CH3Cl) or
r(CH3Br)), that is, the amounts of converted CH4 and formed
product at controlled CH4 conversions per surface area per
time unit, among the CeO2 catalysts with different morphol-
ogies (see Figure S5 in the Supporting Information for the
calculation of intrinsic rates). The CeO2 nanorods show the
highest r(CH4) and r(CH3Cl) for the oxidative chlorination of
CH4, followed by nanocubes, nano-octahedra, and nano-
particles (Table 1). For the oxidative bromination of CH4, the
nanorods and nanocubes possess similar r(CH4) and
r(CH3Br), which are higher than the nano-octahedra and
nanoparticles. These results suggest that in both reactions the
{100} and {110} planes of CeO2 are more active than the {111}
plane.
Figure 1. Selectivities of CH3Cl (A) and CH3Br (B) formations versus
CH4 conversions in the oxidative chlorination and bromination of CH4
over CeO2 nanocrystals with different morphologies and the modified
CeO2 nanocrystals. Reaction conditions: A) T=753 K, CH4/HCl/O2/
N2/He=4/2/1/1.5/1.5, total flow rate=40 mLminÀ1; B) T=873 K,
40 wt% HBr aqueous solution 4.0 mLhÀ1, CH4/O2/N2 =4/1/1 (flow
&
For the selective oxidation of CH4 to HCHO by O2 over
most heterogeneous catalysts, the HCHO selectivity
decreased sharply with increasing CH4 conversion, thus
leading to very limited HCHO yields (< 5%).[1b,c,h] For the
oxidative chlorination or bromination of CH4 over CeO2
nanocrystals, CH3Cl or CH3Br selectivities decreased only
modestly with increasing CH4 conversion by increasing the
rate=15 mLminÀ1). NiO–CeO2 cube, FeOx–CeO2 rod, cube,
*
*
~
^
& rod, octahedron, particle.
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CeOCl was formed under the reaction conditions (see
Figure S6 in the Supporting Information for the results of
CeO2 nanocubes). This suggests that CeO2 is the active phase.
Concerning the nature of the structure sensitivity (different
catalytic behaviors of different exposed planes), theoretical
studies showed that the {111} plane of CeO2 has the lowest
surface energy, followed by the {110} and {100} planes.[13]
CeO2 nanoparticles, which mainly expose {111} planes, show
lower CO oxidation activity than CeO2 nanorods and nano-
cubes.[12] Our H2-TPR (temperature-programmed reduction)
studies showed that the reduction of Ce4+ to Ce3+ was easiest
for the nanorods, followed by the nanocubes, nano-octahedra,
and nanoparticles (Supporting Information, Figure S7). This
is in agreement with the CH4 conversion rates for CeO2
catalysts with different morphologies. We have proposed
a possible reaction mechanism for the oxidative chlorination
and bromination of CH4 over CeO2 catalysts (Supporting
Information, Figure S8). We suggest that the reduction of
Ce4+ to Ce3+ plays a key role in the activation of HCl or HBr
to form an active Cl or Br species for CH4 conversion, and the
reduced Ce3+ is reoxidized to Ce4+ by O2.
We have examined the effect of various additives on the
catalytic performances of CeO2 nanocrystals, and found that,
compared to single CeO2 nanorod or nanocube, the 15 wt%
FeOx–CeO2 nanorod and the 10 wt% NiOx–CeO2 nanocube
provided improved performances, especially selectivities;
CH3Cl and CH3Br selectivities of 74% and 82% were
attained at CH4 conversions of 23% and 22%, respectively
(Figure 1). Solid-solution phases were formed between FeOx
or NiO with CeO2 in the composites, and the heteroatoms in
CeO2 might promote the adsorption and activation of HCl or
HBr to form active Cl or Br species (Supporting Information,
Figure S8). The FeOx–CeO2 nanorod and NiOx–CeO2 nano-
cube catalysts were stable during the oxidative chlorination
and bromination of CH4. During these reactions, the selec-
tivities of CH3Cl and CH3Br stayed almost unchanged over
approximately 100 hours, and CH3Cl and CH3Br could be
sustained in more than 15% yields over these catalysts
(Figure 2).
Figure 2. Dependences of catalytic performances on time on stream
for the oxidative chlorination of CH4 over the 15 wt% FeOx–CeO2
nanorods (A) and the oxidative bromination of CH4 over the 10 wt%
NiO–CeO2 nanocubes (B). Reaction conditions: A) catalyst (0.50 g),
T=753 K, CH4/HCl/O2/N2/He=4/2/1/1.5/1.5, total flow rate=40
mLminÀ1; B) catalyst (1.0 g), T=873 K, 40 wt% HBr aqueous solution
4.0 mLhÀ1, CH4/O2/N2 =4/1/1 (flow rate=15 mLminÀ1). CH3X
&
~
*
*
^
selectivity, CH4 conversion, CH3X yield, COx selectivity, CH2X2
selectivity. X=Cl (A), X=Br (B).
the selectivities of the formation of C2–C4 alkanes and C2H4
decreased correspondingly. Besides the products listed in
Table 2, Cx hydrocarbons (x ꢀ 5), particularly aromatic com-
pounds, were also formed and the selectivity of their
formation decreased when the F/Si ratio was increased.
While an F/Si ratio that was too high was disadvantageous to
the conversion of CH3Br or CH3Cl, the decrease in the
activity was insignificant at proper F/Si ratios. The F-modified
Table 2: Effect of modification of H-ZSM-5 by NH4F for the conversions
of CH3Br and CH3Cl.[a]
For the second step, that is, the conversion of CH3Cl or
CH3Br to olefins, only few studies have been reported. A few
research groups showed that zeolite SAPO-34 could catalyze
the formation of lower olefins from CH3Cl and CH3Br, but
the selectivity of the formation of C2H4 was higher than that
of C3H6, which was on the level of 20–40%.[14–16] SAPO-34
underwent quick deactivation in a few hours in these
reactions. Li+-exchanged ZSM-5 could catalyze the CH3Cl
conversion, but the C3H6 selectivity was also low.[17] We first
compared the catalytic performances of several H-form
zeolites for the conversion of CH3Br, and found that H-
ZSM-5 exhibited a markedly higher CH3Br conversion and
F/Si
ratio
Conv.
[%]
Selectivity[b] [%]
Yield of
C3H6 [%]
0[c]
CH4
C2À4
C2H4
C3H6
C4H8
A) CH3Br conversion
0
92
98
98
94
87
35
1.2
0.9
1.0
1.4
1.5
3.5
23
11
5.0
1.5
0.4
0
13
11
7.5
4.3
3.1
1.8
30
38
46
56
59
63
13
20
25
23
25
30
28
38
45
53
51
23
0.031
0.047
0.063
0.079
0.095
B) CH3Cl conversion
0
88
83
89
76
68
55
1.6
1.9
1.0
1.3
1.4
1.3
37
26
8.1
1.1
0.6
0.5
18
20
12
4.8
3.5
3.0
18
27
46
64
67
67
5.8
9.9
20
23
23
26
16
22
41
49
45
37
0.031
0.047
0.063
0.079
0.095
a
moderate C3H6 selectivity (Supporting Information,
Table S3).
We have succeeded in improving C3H6 selectivity by
treating H-ZSM-5 with an aqueous solution of NH4F followed
by calcination. By increasing the concentration of NH4F
(expressed as the molar ratio of F/Si) used for H-ZSM-5
treatment, C3H6 selectivity increased significantly for both
CH3Br and CH3Cl conversions (Table 2). At the same time,
[a] Reaction conditions: A) catalyst (0.10 g), T=673 K, P-
(CH3Br)=9.2 kPa, flow rate=11 mLminÀ1, time on stream=2 h;
B) catalyst (0.30 g), T=673 K, P(CH3Cl)=3.3 kPa, flow rate=15
mLminÀ1, time on stream=2 h. [b] The remaining products were Cx
hydrocarbons (xꢀ5). [c] C2–C4 alkanes.
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H-ZSM-5 with an F/Si ratio of 0.063 afforded the best C3H6-
formation activity in both CH3Br and CH3Cl conversions;
C3H6 selectivities of 56% and 64% were attained at CH3Br
and CH3Cl conversions of 94% and 76%, respectively. To the
best of our knowledge, these superior C3H6 formation
performances have to date never been achieved in the
conversions of halogenomethanes.
The rapid deactivation was a serious problem for zeolite-
catalyzed CH3Cl and CH3Br conversions.[14–17] Our results
revealed that H-ZSM-5 was also deactivated seriously in
CH3Cl conversion (Supporting Information, Figure S9). How-
ever, the modification by fluorine significantly improved the
stability of the catalyst. With the F-modified H-ZSM-5 (F/Si =
0.063), C3H6 selectivity kept almost unchanged, and CH3Cl
conversion decreased only slightly within 50 hours (Fig-
ure 3A). Moreover, the regeneration of the catalyst was
possible by a simple treatment in air at the reaction temper-
ature for two hours. The F-modified H-ZSM-5 was also stable
in the conversion of CH3Br to C3H6 (Figure 3B).
strong Brønsted acidity may suppress the hydrogen transfer
and the aromatization reactions,[19] and thus contribute to the
increase in C3H6 selectivity by inhibiting the formations of
lower alkanes and aromatic compounds (Table 2).
We found that, in addition to the micropores with sizes of
0.51–0.55 nm, which is typical for ZSM-5, new micropores
with sizes of 0.73–0.78 nm were generated after F modifica-
tion (Supporting Information, Figure S12). The generation of
the larger micropores was confirmed by the adsorption
studies with p-xylene and o-xylene (Supporting Information,
Table S4). This may be due to the F-induced desilication in
peculiar positions of ZSM-5.[20] We speculate that the
interaction of the FÀ anions with the nearby framework Si
may produce SiF4 gas, particularly at the calcination stage,
thus creating larger micropores (Supporting Information,
Figure S13).
For the formation of lower olefins from both CH3OH and
CH3Cl the “hydrocarbon pool” mechanism has been pro-
posed, in which the lower olefins are believed to be generated
via methylbenzene intermediates.[10b,21] We have character-
ized the hydrocarbon intermediates with our catalysts by
a method reported previously,[22] and observed various
methylbenzenes over H-ZSM-5 and F-modified H-ZSM-5
(Supporting Information, Table S5). It is of significance that
the distribution of methylbenzenes is different over the two
catalysts, and the modification by F increased the fraction of
tetra-, penta-, and hexa-benzenes, which are proposed mainly
for C3H6 formation.[22] The generated larger micropores in the
F-modified H-ZSM-5 may account for this change in the
distribution of the intermediates in the hydrocarbon pool on
catalyst surfaces. Based on these results, we have proposed
reaction mechanisms for the conversions of CH3Cl or CH3Br
over H-ZSM-5 and F-modified H-ZSM-5 catalysts (Support-
ing Information, Figure S14).
In conclusion, we have developed novel and efficient
catalysts for a new two-step route for the production of
propylene from methane via CH3Cl or CH3Br. CeO2 is an
efficient and stable catalyst for the oxidative chlorination and
bromination of methane to CH3Cl and CH3Br. The catalytic
properties of CeO2 are dependent on its morphology or the
exposed crystalline planes. The modification of CeO2 nano-
crystals by FeOx or NiO could enhance the selectivity of
CH3Cl or CH3Br formation. For the second step, an F-
modified H-ZSM-5 is highly selective and stable for the
conversions of both CH3Cl and CH3Br into propylene.
It is noteworthy that Periana et al.[23] once developed an
efficient two-step conversion of methane to methanol via
methyl bisulfate by using oleum as an oxidant. However, this
system suffers from the difficulties in the separations of
product and catalyst from the oleum medium and in the
recovery and reoxidation of the produced SO2. In contrast,
the product can be easily separated from our heterogeneous
catalytic system. Although HCl and HBr are not particularly
environmentally friendly, the easy separation and recycling of
HCl or HBr in our case could avoid their net release. The
overall efficiencies for HCl and HBr were estimated to be 65–
70% and 90–93%, respectively, without considering the uses
of CH2Cl2 and CH2Br2 formed in the first step (see Supporting
Information for details). Future studies are needed to further
Figure 3. Catalytic performances of F-modified H-ZSM-5 versus time
on stream for the conversions of CH3Cl (A) and CH3Br (B). Reaction
conditions: A) catalyst (0.30 g), T=673 K, P(CH3Cl)=3.3 kPa, flow
rate=15 mLminÀ1; B) catalyst (0.10 g), T=673 K, P(CH3Br)=9.2 kPa,
flow rate=11 mLminÀ1
yield. X=Cl (A), X=Br (B)
.
CH3X conversion, & C3H6 selectivity, C3H6
*
*
We have characterized the F-modified H-ZSM-5 to gain
insights into the nature of F modification. Powder X-ray
diffraction (XRD) measurements showed that the modifica-
tion did not significantly change the crystalline structure of
ZSM-5 (Supporting Information, Figure S10). However, the
acidity and porous structure of ZSM-5 underwent significant
changes after modification. The concentration of the acid
sites, particularly the strong Brønsted acid sites, was dramat-
ically decreased after F modification (Supporting Informa-
tion, Figure S11). The same phenomenon was also observed
previously and was proposed to contribute to the inhibition of
catalyst deactivation in the dehydro-aromatization of CH4 to
benzene.[18] The weakened acidity may also be beneficial to
catalyst stability in our case. Moreover, the decrease in the
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[4] http://www.grt-inc.com/go/technology/grt-technology/.
[5] a) K. X. Wang, H. F. Xu, W. S. Li, X. P. Zhou, J. Mol. Catal. A
2005, 225, 65 – 69; b) Z. Liu, L. Huang, W. S. Li, F. Yang, C. T.
Au, X. P. Zhou, J. Mol. Catal. A 2007, 273, 14 – 20.
improve the selectivity of target products and to elucidate the
detailed reaction mechanism for each step.
[6] F. Li, G. Yuan, Angew. Chem. 2006, 118, 6691 – 6694; Angew.
Chem. Int. Ed. 2006, 45, 6541 – 6544.
[7] R. Lin, Y. Ding, L. Gong, W. Dong, J. Wang, T. Zhang, J. Catal.
2010, 272, 65 – 73.
Experimental Section
CeO2 nanocrystals with different morphologies as well as CeO2
nanoparticles with a large surface area were synthesized by hydrolysis
of Ce(NO3)3 in alkaline medium, followed by hydrothermal treat-
ment.[12b] The morphologies were controlled by varying the alkaline
media, Ce(NO3)3 concentrations, and the hydrothermal conditions.
The FeOx–CeO2 nanorods and NiOx–CeO2 nanocubes were prepared
by adding Fe(NO3)3 and NiCl2 into aqueous solutions of Ce(NO3)3,
followed by hydrolysis and hydrothermal treatment procedures used
for syntheses of CeO2 nanorods and nanocubes, respectively. H-ZSM-
5 (Si/Al = 100) was used for CH3Cl and CH3Br conversions. The F-
modified H-ZSM-5 was prepared by treating the H-ZSM-5 with
aqueous solutions of NH4F in different concentrations. After drying at
343 K, the samples were calcined at 873 K for 6 h. XRD, N2 or Ar
physisorption, SEM, TEM, NH3-TPD (temperature-programmed
desorption), H2-TPR, and in situ Raman spectroscopy were used for
catalyst characterizations. Catalytic reactions were performed on
fixed-bed flow reactors operated under atmospheric pressure. The
products were analyzed by gas chromatography. The conversion and
selectivity for each reaction were calculated on a carbon basis. See the
Supporting Information for the experimental details.
[8] a) E. Peringer, S. G. Podkolzin, M. E. Jones, R. Olindo, J. A.
Lercher, Top. Catal. 2006, 38, 211 – 220; b) S. G. Podkolzin, E. E.
Stangland, M. E. Jones, E. Peringer, J. A. Lercher, J. Am. Chem.
Soc. 2007, 129, 2569 – 2576; c) E. Peringer, M. Salzinger, M.
Hutt, A. L. Lemonidou, J. A. Lercher, Top. Catal. 2009, 52,
1220 – 1231.
[9] A. H. Tullo, Chem. Eng. News 2003, 81(50), 15 – 16.
[10] a) M. Stçcker, Microporous Mesoporous Mater. 1999, 29, 3 – 48;
b) J. F. Haw, W. Song, D. M. Marcus, J. B. Nicholas, Acc. Chem.
Res. 2003, 36, 317 – 326.
[11] a) H. Oikawa, Y. Shibata, K. Inazu, Y. Murai, S. Hyodo, G.
Kobayashi, T. Baba, Appl. Catal. A 2006, 312, 181 – 185; b) M.
Iwamoto, Y. Kousugi, J. Phys. Chem. C 2007, 111, 13 – 15; c) M.
Taoufik, E. L. Roux, J. Thivolle-Cazat, J. M. Basset, Angew.
Chem. 2007, 119, 7340 – 7343; Angew. Chem. Int. Ed. 2007, 46,
7202 – 7205; d) B. Lin, Q. Zhang, Y. Wang, Ind. Eng. Chem. Res.
2009, 48, 10788 – 10795.
[12] a) K. Zhou, X. Wang, X. Sun, Q. Peng, Y. Li, J. Catal. 2005, 229,
206 – 212; b) H. X. Mai, L. D. Sun, Y. W. Zhang, R. Si, W. Feng,
H. P. Zhang, H. C. Liu, C. H. Yan, J. Phys. Chem. C 2005, 109,
24380 – 24385; c) N. Ta, M. Zhang, J. Li, H. Li, Y. Li, W. Shen,
Catal. Today 2009, 148, 179 – 183.
Received: June 14, 2011
Revised: January 2, 2012
Published online: January 24, 2012
[13] M. Nolan, S. Grigoleit, D. C. Sayle, S. C. Parker, G. W. Watson,
Surf. Sci. 2005, 576, 217 – 229.
Keywords: cerium oxide · heterogeneous catalysis · methane ·
propylene · zeolites
.
[14] Y. Wei, D. Zhang, Z. Liu, B. L. Su, J. Catal. 2006, 238, 46 – 57.
[15] S. Svelle, S. Aravinthan, M. Bjørgen, K. P. Lillerud, S. Kolboe,
I. M. Dahl, U. Olsbye, J. Catal. 2006, 241, 243 – 254.
[16] A. Zhang, S. Sun, Z. J. A. Koman, N. Osterwalder, S. Gadewar, P.
Stoimenov, D. J. Auerbach, G. D. Stucky, E. W. McFarland, Phys.
Chem. Chem. Phys. 2011, 13, 2550 – 2555.
[17] D. Jaumain, B. L. Su, J. Mol. Catal. A 2003, 197, 263 – 273.
[18] Y. Li, L. Liu, X. Huang, X. Liu, W. Shen, Y. Xu, X. Bao, Catal.
Commun. 2007, 8, 1567 – 1572.
[1] a) D. Wolf, Angew. Chem. 1998, 110, 3545 – 3547; Angew. Chem.
Int. Ed. 1998, 37, 3351 – 3353; b) K. Tabata, Y. Teng, T. Take-
moto, E. Suzuki, M. A. BaÇares, M. A. PeÇa, J. L. G. Fierro,
Catal. Rev. 2002, 44, 1 – 58; c) A. Arena, A. Parmalina, Acc.
Chem. Res. 2003, 36, 867 – 875; d) Y. Xu, X. Bao, L. Lin, J. Catal.
2003, 216, 386 – 395; e) R. Palkovits, M. Antonietti, P. Kuhn, A.
Thomas, F. Schꢁth, Angew. Chem. 2009, 121, 7042 – 7045; Angew.
Chem. Int. Ed. 2009, 48, 6909 – 6912; f) B. Frank, J. Zhang, R.
Blume, R. Schçgl, D. S. Su, Angew. Chem. 2009, 121, 7046 – 7051;
Angew. Chem. Int. Ed. 2009, 48, 6913 – 6917; g) C. Copꢂret,
Chem. Rev. 2010, 110, 656 – 680; h) Q. Zhang, W. Deng, Y. Wang,
Chem. Commun. 2011, 47, 9275 – 9292; i) H. Schwarz, Angew.
Chem. 2011, 123, 10276 – 10297; Angew. Chem. Int. Ed. 2011, 50,
10096 – 10115.
[2] G. A. Olah, B. Gupta, M. Farina, J. D. Felberg, W. M. Ip, A.
Husain, R. Karpeles, K. Lammertsma, A. K. Melhotra, N. J.
Trivedi, J. Am. Chem. Soc. 1985, 107, 7097 – 7105.
[3] X. P. Zhou, A. Yilmaz, G. A. Yilmaz, I. M. Lorkovic, L. E.
Laverman, M. Weiss, J. H. Sherman, E. W. McFarland, G. D.
Stucky, P. C. Ford, Chem. Commun. 2003, 2294 – 2295.
[19] M. A. Sanchez-Castillo, R. J. Madon, J. A. Dumesic, J. Phys.
Chem. B 2005, 109, 2164 – 2175.
ˇ ˇ
[20] a) E. Aubert, F. Porcher, M. Souhassou, V. Petrꢃcek, C. Lecomte,
J. Phys. Chem. B 2002, 106, 1110 – 1117; b) M. P. Attfield,
C. R. A. Catlow, A. A. Sokol, Chem. Mater. 2001, 13, 4708 –
4713.
[21] Y. Wei, D. Zhang, F. Chang, Q. Xia, B. L. Su, Z. Liu, Chem.
Commun. 2009, 5999 – 6001.
[22] M. Bjørgen, F. Joensen, K. P. Lillerud, U. Olsbye, S. Svelle, Catal.
Today 2009, 142, 90 – 97.
[23] a) R. A. Periana, D. J. Taube, E. R. Evitt, D. G. Loffer, P. R.
Wentrcek, T. Masuda, Science 1993, 259, 340 – 343; b) R. A.
Periana, D. J. Taube, S. Gamble, H. Taube, T. Satoh, H. Fujii,
Science 1998, 280, 560 – 564.
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