Highly stable boron-modified hierarchical nanocrystalline ZSM-5 zeolite for the methanol to propylene reaction

Article abstract of DOI:10.1039/c4cy00376d

A highly stable MTP (methanol to propylene) catalyst, boron-modified hierarchical nanocrystalline ZSM-5 zeolite, has been constructed by a facile salt-aided seed-induced route. The cooperative effect of its hierarchical structure and modified acidity gives rise to a significantly stable activity (725 h) even at a high WHSV (weight hourly space velocity) of 4.0 h ^-1. the Partner Organisations 2014.

Full text of DOI:10.1039/c4cy00376d

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Highly stable boron-modified hierarchical
nanocrystalline ZSM-5 zeolite for the
methanol to propylene reaction†
Cite this: Catal. Sci. Technol., 2014,
4, 2891
Received 26th March 2014,
Accepted 9th June 2014
Zhijie Hu,‡ Hongbin Zhang,‡ Lei Wang, Hongxia Zhang, Yahong Zhang,
*
*
Hualong Xu, Wei Shen and Yi Tang
DOI: 10.1039/c4cy00376d
www.rsc.org/catalysis
A highly stable MTP (methanol to propylene) catalyst, boron-
modified hierarchical nanocrystalline ZSM-5 zeolite, has been
constructed by a facile salt-aided seed-induced route. The coop-
erative effect of its hierarchical structure and modified acidity
gives rise to a significantly stable activity (725 h) even at a high
nanosheet7 ZSM-5 with short inner diffusion paths have been
adopted in several catalytic reactions to reduce the catalyst
deactivation caused by pore blockage. Besides, the introduc-
tion of mesopores into the zeolite crystal during synthesis or
post-synthesis modification, for example by soft templating,8
hard templating,9 or alkaline treatment,10 can also slow down
the deactivation of the catalysts in MTP due to their
improved mass transfer properties and tolerance for a larger
amount of coke. The impact of various mesopore types as
well as hierarchical porosity in industrial catalysts has been
proven in the recent literature.11 Additionally, the modifica-
tion of acidity and addition of some active components have
also been developed with some promising results. For exam-
ple, phosphorus-modified ZSM-5 has been reported with
improved catalytic stability and propylene selectivity.12 On
the approach of boron isomorphous substitution, it is found
that the enhanced catalytic stability can be attributed to the
increase of weak acid sites.13 The introduction of gold nano-
particles into ZSM-5 can considerably stabilize the dehydro-
genation intermediates during the coking process to reinforce
the catalytic stability.14 By means of either pore structure
engineering or acidity modification, the lifetime of the
catalysts can be prolonged from dozens to hundreds of
hours at a weight hourly space velocity (WHSV) of around
WHSV (weight hourly space velocity) of 4.0 h−1
.
With the increasing demand for propylene and the decreasing
stores of petroleum in a post-oil society, the methanol to
propylene (MTP) process has drawn significant attention in
the chemical industry.1 Over the last two decades, much fun-
damental research has been conducted to develop effective
catalysts with high selectivity and long lifetimes for the MTP
process.2 Recent studies have demonstrated that ZSM-5 zeo-
lite with a high Si/Al molar ratio is one of the most promising
catalysts for the MTP reaction owing to its characteristic MFI
topology.3 However, ZSM-5 zeolite still suffers from rapid/
severe deactivation associated with carbon depositions dur-
ing the acid catalysed reaction process, which would result in
the covering of the active sites or the blocking of the micro-
pore channels of the catalyst, especially on the external
surface.4
In order to solve the problem of rapid/severe deactivation
and develop a highly stable catalyst for the MTP reaction,
abundant new strategies have been proposed. In terms of
pore structure design, hierarchical structured zeolite is an
ideal alternative because it possesses the advantages of both
mesoporous materials and zeolite crystals with highly-
improved mass transport properties.5 Nanocrystalline6 and
0.5–2.0 h−1 7–10,12–14
However, from a practical point of view,
.
a catalyst with a longer lifetime even at a higher WHSV is
still desired, especially via a preparation method which
involves simple steps, a high reproducibility and few energy–
environment problems, for large-scale production and indus-
trial applications.11,15
Herein, a highly stable MTP catalyst is designed using the
combination of pore structure engineering and acidity modi-
fication. This boron-modified hierarchical nanocrystalline
ZSM-5 zeolite (denoted as B–N–Z5) catalyst displays inter-
crystal mesoporosity from oriented self-assembled nano-
crystallites and weak acidity from boron-modification. Based
on the novel “salt-aided seed-induced route” recently proposed
by our laboratory,16 the one-step synthesis of B–N–Z5 catalyst
Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and
Innovative Materials, Laboratory of Advanced Materials, and Collaborative
Innovation Center of Chemistry for Energy Materials, Fudan University,
Shanghai 200433, PR China. E-mail: yitang@fudan.edu.cn,
wshen@fudan.edu.cn; Fax: (+86) 21 65641740
† Electronic supplementary information (ESI) available: synthesis procedure,
characterization method, catalyst test, SEM and TEM images, 11B and 27Al MAS
NMR spectra, TG curves, catalytic performance on MTP, XRD patterns. See
DOI: 10.1039/c4cy00376d
‡ These authors contributed equally to this work.
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has the advantages of a fast crystallization process (within
4 h), high yield (>80%), low template consumption (TPABr/
SiO2 = 0.1) and no detectable extra-framework aluminum or
boron species. Notably, an ultra-long lifetime (about 725 h)
has been realized for this B–N–Z5 catalyst even at a high
WHSV of 4.0 h−1. Such an approach may bring new possibili-
ties for developing highly stable MTP reaction catalysts for
industrial applications.
H3 hysteresis loop. The steep increase at low relative pressure
(P/P0 < 0.2) illustrates the perfect microporous structure in
this sample while the special hysteresis loop appearing at
P/P0 = 0.1–0.4 is associated with the phenomenon of the
fluid-to-crystalline phase transition of adsorbed N2 on the
ZSM-5 zeolite with high Si/Al ratio.17 Moreover, B–N–Z5 has a
large hysteresis loop and enhanced adsorption at intermedi-
ate and high pressures (0.4 < P/P0 < 1) arising from nitrogen
adsorption on inter-crystallite mesopores formed by the
assembly of adjacent nano-crystallites, in agreement with the
TEM image in Fig. 1c. In addition, the B–N–Z5 particles pos-
sess a high mechanical stability, which is proved by the ultra-
sound experiment which was conducted for 180 min after
calcination (Fig. S1†).
The incorporation of B and its influence on the framework
Al in B–N–Z5 are characterized by 11B and 27Al magic-angle-
spinning nuclear magnetic resonance (MAS NMR) as shown
in Fig. 1f. In the 11B MAS NMR spectrum, an intensive and
highly symmetric peak is observed at a chemical shift of ca.
−3.9 ppm, which is a characteristic peak of tetrahedral B spe-
cies in the B-MFI framework.18 There are no peaks at ca. −2.0
or above 5.0 ppm, which correspond to the extra-framework
tetrahedral and the various trigonal B species respectively. In
the 27Al MAS NMR spectrum, there is only one peak at a
chemical shift of ca. 55 ppm, corresponding to the IV-coordinate
Al in the framework. No signal at ca. 0 ppm, assigned to
VI-coordinate extra-framework Al, is observed, indicating that
the Al species in this sample are all IV-coordinate framework
Al. Therefore, the B species are completely incorporated into
the B–N–Z5 zeolite framework and the existence of B does
not affect Al incorporation into the zeolite framework during
the “salt-aided seed-induced route”. The advantages of this
method for heteroatom incorporation could also be demon-
strated by comparison with the conventional hydrothermal
synthesis method reported in our previous work,13 where not
only extra-framework boron but also extra-framework alumi-
num species appeared (Fig. S2, ESI†).
A scanning electron microscopy (SEM) image is depicted
in Fig. 1a. It clearly shows that the B–N–Z5 sample exhibits a
uniformly globular morphology consisting of globules with a
diameter of about 500 nm and a very rough external surface.
The transmission electron microscopy (TEM) images in
Fig. 1b and c show that each of the uniform zeolite micro-
spheres is made up of abundant small nano-crystallite
domains with an average diameter of about 20–40 nm. The
in situ assembly of these nano-crystallites during the hydro-
thermal synthesis gives rise to abundant inter-crystallite
mesopores amongst these zeolite nano-crystallites. The high-
resolution TEM (HRTEM) image in Fig. 1d further proves that
these small nano-crystallites are highly crystalline and their
lattice fringes exhibit the same orientation which even
extends over the whole zeolite aggregates, and the inset
selected area electron diffraction (SAED) pattern presents a
clear single-crystal-like diffraction pattern of ZSM-5 zeolite.
This high-crystallinity hierarchical nanocrystalline structure
is also evidenced by the N2 sorption isotherm (Fig. 1e), in
which the B–N–Z5 sample shows a type IV isotherm with an
To more clearly investigate the effects of the hierarchical
structure and boron-modified acidity of B–N–Z5, a conven-
tional ZSM-5 (denoted as C–Z5, Fig. S3a in the ESI,† synthe-
sized according to ref. 13), a hierarchical nanocrystalline
ZSM-5 (denoted as N–Z5, Fig. S4 in the ESI,† synthesized
according to ref. 16a) and a B-modified conventional ZSM-5
(denoted as B–C–Z5, Fig. S3b and S5 in the ESI,† the best cat-
alyst with boron isomorphous substitution in ref. 13) are
adopted as reference samples. Some detailed information on
C–Z5, N–Z5 and B–C–Z5 is described in the ESI.† Their com-
positions and textural properties are summarized in Table 1.
Elemental analysis by inductively coupled plasma-atomic
emission spectrometry (ICP-AES) reveals that all these sam-
ples contain a similar Si/Al ratio of ca. 160. Also, B–C–Z5 and
B–N–Z5 have a similar boron content. Moreover, all of the
samples have a large specific surface area (SL, ca. 460 m2 g−1
)
and micropore volume (Vmicro, ca. 0.12 cm3 g−1). N–Z5 and
B–N–Z5 possess much larger mesopore volumes (Vmeso, ca.
0.19 cm3 g−1) and external surfaces (Sext, ca. 110 m2 g−1) than
Fig. 1 (a) SEM, (b, c) TEM, (d) HRTEM and SAED images (inset of d),
(e) N2 sorption isotherm, (f) 11B and 27Al MAS NMR spectra of B–N–Z5.
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Table 1 Compositions and textural properties of various samples
Sample
Si/Ala
B/Ala
SL (m2 g−1
)
Sextb (m2 g−1
)
Vmicrob (cm3 g−1
)
Vmesoc (cm3 g−1
)
C–Z5
N–Z5
B–C–Z5
B–N–Z5
156
152
160
162
0
0
0.58
0.62
435
489
452
460
52
122
67
0.12
0.11
0.12
0.11
0.07
0.19
0.07
0.18
109
a
b
c
Determined by ICP-AES. By the t-plot method. By the BJH method. SL: Langmuir surface area; Sext: external surface area; Vmicro: micropore
volume; Vmeso: mesopore volume.
C–Z5 and C–B–Z5 (ca. 0.07 cm3 g−1 and 60 m2 g−1) due to
their hierarchical nanocrystalline structure.
To better study the catalytic stability of the B–N–Z5 for
the MTP reaction, comparative tests were performed under
approximate industrial conditions (full methanol conversion)6–15
but with a more harsh WHSV (4.0 h−1, four times the WHSV
of around 1.0 h−1 commonly used in the literature6–10,12,14) to
accelerate the deactivation of the catalysts. The results show
that all the samples present a steady high methanol con-
version of nearly 100% (Fig. 3a) and similar olefin and
propylene selectivity (Fig. 3b and c). However, their activity
would rapidly decay once the methanol conversion begin to
decrease (Fig. 3a). The catalyst stability is estimated by using
the reaction time for complete methanol conversion at a cer-
tain WHSV according to ref. 6–15. The B–N–Z5 catalyst dis-
plays the longest lifetime of 725 h (Fig. 3a) compared with
C–Z5 (80 h), N–Z5 (120 h) and even B–C–Z5 (320 h). Referring
to the textural and acidic properties shown above, the high
stability of B–N–Z5 can be attributed to the cooperative effect
of its hierarchical structure and boron-modified acidity. In
detail, compared with C–Z5 (80 h), the tendency of slowing
down the deactivation of N–Z5 (120 h) is derived from its
hierarchical nanocrystalline structure, which can shorten the
micropore channels to improve the diffusion properties and
accommodate more coke deposits.6,7 The enhanced stability
of B–C–Z5 (320 h) can be attributed to the increase of weak
Brønsted acid sites due to the B-incorporation. The introduc-
tion of more weak acid sites is believed to speed up the
Fig. 2a depicts the powder X-ray diffraction (XRD) patterns
of the four ZSM-5 samples. The samples all present the char-
acteristic diffraction peaks for the typical structure of MFI
topology at 2θs of 7.0–9.0 and 23.0–25.0, and no impure or
amorphous phase was detected. However, the N–Z5 and B–N–Z5
samples present broader and weaker diffraction peaks, proba-
bly due to the submicron size of the N–Z5 and B–N–Z5 parti-
cles. The acidities of the samples were characterized by the
temperature-programmed desorption of ammonia (NH3-TPD).
Fig. 2b displays the typical profile of s zeolite with two
desorption peaks, in which the peak at the low temperature
of around 150 °C (peak I) is assigned to the weak acid sites
while that at the high temperature of around 330 °C (peak II)
is attributed to the strong acid sites. In detail, the amount of
strong acid sites in these four samples are close to each
other, in good agreement with their similar Si/Al ratio; while
the amount weak acid sites for B–C–Z5 and B–N–Z5 increase
with B incorporation into the ZSM-5 framework.13 Besides,
peak I of B–C–Z5 and B–N–Z5 displays an interesting shift to
lower temperature probably due to the weaker acidity of
B–OH–Si;13 while peak II of N–Z5 and B–N–Z5 has moved to a
higher temperature probably due to the seed-induced synthe-
sis method and the resulting special structure.16a This modi-
fied acidity due to B incorporation is expected to result in
improved catalytic performance in the MTP reaction.
Fig. 3 Conversion of methanol (a), selectivity of total olefin (b) and
propylene (c) over zeolites C–Z5 (black), N–Z5 (dark cyan), B–C–Z5
(blue) and B–N–Z5 (red). Reaction conditions: WHSV = 4.0 h−1, T = 733 K,
n(CH3OH) : n(H2O) = 1 : 3, Ptotal = 1 atm.
Fig. 2 (a) XRD patterns and (b) NH3-TPD profiles of C–Z5, N–Z5, B–C–Z5
and B–N–Z5.
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reactions involved in olefin production and suppress the
tendency for competitive polycyclic aromatization of the
multi-methyl benzene intermediate to coke precursors.13,18,19
Combining both advantages, the B–N–Z5 catalyst successfully
realizes the cooperative effect of hierarchical structure and
boron-modified acidity, so that it demonstrates a high stabil-
ity for 725 h at a high WHSV of 4 h−1, much longer than the
simple sum of those of N–Z5 with only a hierarchical nano-
crystalline structure (120 h) and B–C–Z5 with only boron
modified acidity (320 h). Fig. S6† further shows the coke
deposition on the deactivated catalysts measured by thermo-
gravimetric (TG) analysis. It is found that the amount of coke
is in the order B–N–Z5 > B–C–Z5 > N–Z5 ≫ C–Z5, although
the former has the highest stability. It indicates that B–N–Z5
has a strong capability for coke tolerance due to the co-effect
of the hierarchical porosity and unique acid distribution with
enriched weak acid sites, which ensures the long-term main-
tenance of the catalytic activity until more coke is finally
formed.
N–Z5. The catalytic performance of B/N–Z5 was also evaluated
at a WHSV of 10 h−1 (Fig. S7†). B/N–Z5 exhibits a much
shorter lifetime of only 9 h (methanol conversion above 80%)
and lower olefin (<60%) and propylene (34%) selectivity com-
pared with B–N–Z5. Meanwhile, according to the XRD pat-
terns (Fig. S8†) of B/N–Z5 before and after the reaction, the
appearance of alpha quartz was observed after only 12 h of
the reaction, probably due to its lower stability in steam.
However, the patterns of B–N–Z5 show almost no alteration.
These results imply that the tetrahedral boron incorporated
in the zeolite framework is important for catalyst stability.
The 11B and 27Al MAS NMR of B–N–Z5 after reaction were
further employed to characterize the stability of the B and
Al sites towards hydrolysis under the testing conditions.
According to the results in Fig. S9,† most of the B and Al spe-
cies are still IV-coordinate species in the framework although
some defects or extra-framework B and Al species are observed.
Therefore, after regeneration, the catalytic activity can still be
maintained to some extent (Fig. 4) under the harsh reaction
conditions of WHSV = 10 h−1.
The catalytic performance of B–N–Z5 has further been
evaluated at an even higher space velocity and with lower
water content in the feed after several cycles of catalyst regen- Conclusions
eration to deepen the understanding of the properties of
In summary, boron-modified hierarchical nanocrystalline
B-modified hierarchical catalysts. As shown in Fig. 4, when
the WHSV is increased to 10 h−1, the B–N–Z5 still exhibits
excellent performance with high methanol conversion (above
80%) after ca. 60 h with 65% olefin and 43% propylene selec-
tivity. After regenerating the catalyst in air (40 mL min−1) at
843 K for 8 h, B–N–Z5 still displays relatively high methanol
conversion (above 75%) after ca. 40 h at a WHSV of 10 h−1. In
order to further study the catalyst stability, a third cycle was
been carried out on the second regenerated catalyst at a
WHSV of 10 h−1 and n(CH3OH) : n(H2O) = 1 : 1. Interestingly,
B–N–Z5 shows high stability with high methanol conversion
(above 80%) after 55 h with a lower water ratio in the feed.
To shed some light on the role of boron, a B/N–Z5 catalyst
was prepared by impregnating a similar amount of boron on
ZSM-5 zeolite (B–N–Z5) could be facilely prepared by a salt-
aided seed-induced method, which provides a possibility for
large-scale production due to the easy synthesis, fast crystalli-
zation and low usage of organic templates. The systematic
and thorough characterization demonstrates that the typical
B–N–Z5 catalyst not only has a rough external surface, abun-
dant intercrystal mesopores and a high crystallinity, but also
possesses an increasing amount of weak acid sites arising
from the framework incorporation of boron. This B–N–Z5
catalyst has a very long lifetime of 725 h even at a high WHSV
of 4.0 h−1 for the MTP reaction, which could be attributed to
the unique cooperative effect of the hierarchical nanocrystal-
line structure and boron-modified acidity in this sample. The
results shown here indicate the necessity of the combination
of pore structure design and acidity modification for the
highly stable MTP catalyst.
Acknowledgements
This work was supported by National Key Basic Research
Program of China (2013CB934101), and Science and Technology
Commission of Shanghai Municipality (11JC1400400).
Notes and references
1 (a) U. Olsbye, S. Svelle, M. Bjorgen, P. Beato,
T. V. W. Janssens, F. Joensen, S. Bordiga and K. P. Lillerud,
Angew. Chem., Int. Ed., 2012, 51, 5810–5831; (b) M. Stocker,
Microporous Mesoporous Mater., 1999, 29, 3–48; (c)
D. Lesthaeghe, A. Horre, M. Waroquier, G. B. Marin and
V. Van Speybroeck, Chem. – Eur. J., 2009, 15, 10803–10808;
(d) U. Olsbye, M. Bjorgen, S. Svelle, K. P. Lillerud and
S. Kolboe, Catal. Today, 2005, 106, 108–111; (e) Z. M. Cui,
Fig.
4 Conversion of methanol, selectivity of total olefin and
propylene over zeolite B–N–Z5. Reaction conditions: WHSV = 10 h−1
,
)
T = 733 K, Ptotal = 1 atm. Regeneration conditions: in air (40 mL min−1
at 843 K for 8 hours.
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Q. Liu, W. G. Song and L. J. Wan, Angew. Chem., Int. Ed.,
2006, 45, 6512–6515; ( f ) W. Wang, Y. J. Jiang and
M. Hunger, Catal. Today, 2006, 113, 102–114; (g) W. Wang,
A. Buchholz, M. Seiler and M. Hunger, J. Am. Chem. Soc.,
2003, 125, 15260–15267.
10 (a) C. S. Mei, P. Y. Wen, Z. C. Liu, H. X. Liu, Y. D. Wang,
W. M. Yang, Z. K. Xie, W. M. Hua and Z. Gao, J. Catal.,
2008, 258, 243–249; (b) P. N. R. Vennestrom, M. Grill,
M. Kustova, K. Egeblad, L. F. Lundegaard, F. Joensen,
C. H. Christensen and P. Beato, Catal. Today, 2011, 168, 71–79.
11 (a) M. Milina, S. Mitchell, P. Crivelli, D. Cooke and
J. Pérez-Ramírez, Nat. Commun., 2014, 3922, DOI: 10.1038/
ncomms4922; (b) S. Mitchell, N. L. Michels, K. Kunze and
J. Perez-Ramirez, Nat. Chem., 2012, 4, 825–831.
12 J. Liu, C. X. Zhang, Z. H. Shen, W. M. Hua, Y. Tang,
W. Shen, Y. H. Yue and H. L. Xu, Catal. Commun., 2009, 10,
1506–1509.
13 Y. S. Yang, C. Sun, J. M. Du, Y. H. Yue, W. M. Hua,
C. L. Zhang, W. Shen and H. L. Xu, Catal. Commun.,
2012, 24, 44–47.
14 C. Sun, Y. S. Yang, J. M. Du, F. Qin, Z. P. Liu, W. Shen,
H. L. Xu and Y. Tang, Chem. Commun., 2012, 48, 5787–5789.
15 R. Chal, C. Gerardin, M. Bulut and S. van Donk,
ChemCatChem, 2011, 3, 67–81.
16 (a) H. B. Zhang, Y. C. Ma, K. S. Song, Y. H. Zhang and
Y. Tang, J. Catal., 2013, 302, 115–125; (b) H. B. Zhang,
K. S. Song, L. Wang, H. X. Zhang, Y. H. Zhang and Y. Tang,
ChemCatChem, 2013, 5, 2874–2878.
2 (a) Q. Zhu, J. N. Kondo, T. Tatsumi, S. Inagaki, R. Ohnuma,
Y. Kubota, Y. Shimodaira, H. Kobayashi and K. Domen,
J. Phys. Chem. C, 2007, 111, 5409–5415; (b) A. T. Aguayo,
A. G. Gayubo, R. Vivanco, M. Olazar and J. Bilbao, Appl.
Catal., A, 2005, 283, 197–207; (c) B. P. C. Hereijgers,
F. Bleken, M. H. Nilsen, S. Svelle, K. P. Lillerud, M. Bjorgen,
B. M. Weckhuysen and U. Olsbye, J. Catal., 2009, 264, 77–87;
(d) M. Bjorgen, S. Svelle, F. Joensen, J. Nerlov, S. Kolboe,
F. Bonino, L. Palumbo, S. Bordiga and U. Olsbye, J. Catal.,
2007, 249, 195–207; (e) S. Ilias and A. Bhan, ACS Catal.,
2013, 3, 18–31.
3 (a) J. F. Haw, W. G. Song, D. M. Marcus and J. B. Nicholas,
Acc. Chem. Res., 2003, 36, 317–326; (b) J. Z. Li, Y. X. Wei,
G. Y. Liu, Y. Qi, P. Tian, B. Li, Y. L. He and Z. M. Liu, Catal.
Today, 2011, 171, 221–228; (c) A. G. Gayubo, A. T. Aguayo,
M. Olazar, R. Vivanco and J. Bilbao, Chem. Eng. Sci.,
2003, 58, 5239–5249.
4 H. Schulz, Catal. Today, 2010, 154, 183–194.
5 (a) L. H. Chen, X. Y. Li, J. C. Rooke, Y. H. Zhang, X. Y. Yang,
Y. Tang, F. S. Xiao and B. L. Su, J. Mater. Chem., 2012, 22,
17381–17403; (b) J. Perez-Ramirez, C. H. Christensen,
K. Egeblad, C. H. Christensen and J. C. Groen, Chem. Soc.
Rev., 2008, 37, 2530–2542.
6 M. Firoozi, M. Baghalha and M. Asadi, Catal. Commun.,
2009, 10, 1582–1585.
7 (a) M. Choi, K. Na, J. Kim, Y. Sakamoto, O. Terasaki and
R. Ryoo, Nature, 2009, 461, 246–249; (b) S. Hu, J. Shan,
Q. Zhang, Y. Wang, Y. S. Liu, Y. J. Gong, Z. J. Wu and
T. Dou, Appl. Catal., A, 2012, 445, 215–220.
17 J. C. Groen, L. A. A. Peffer and J. Pérez-Ramírez, Microporous
Mesoporous Mater., 2003, 60, 1–17.
18 R. Millini, G. Perego and G. Bellussi, Top. Catal., 1999, 9,
13–34.
19 (a) Q. J. Zhu, J. N. Kondo, T. Yokoi, T. Setoyama,
M. Yamaguchi, T. Takewaki, K. Domen and T. Tatsumi,
Phys. Chem. Chem. Phys., 2011, 13, 14598–14605; (b)
Q. J. Zhu, J. N. Kondo, T. Setoyama, M. Yamaguchi,
K. Domen and T. Tatsumi, Chem. Commun.,
2008, 5164–5166; (c) E. Unneberg and S. Kolboe, Appl. Catal., A,
1995, 124, 345–354; (d) M. Guisnet, L. Costa and
F. R. Ribeiro, J. Mol. Catal. A: Chem., 2009, 305, 69–83; (e)
D. Mores, J. Kornatowski, U. Olsbye and B. M. Weckhuysen,
Chem. – Eur. J., 2011, 17, 2874–2884.
8 J. Kim, M. Choi and R. Ryoo, J. Catal., 2010, 269, 219–228.
9 C. Sun, J. M. Du, J. Liu, Y. S. Yang, N. Ren, W. Shen,
H. L. Xu and Y. Tang, Chem. Commun., 2010, 46, 2671–2673.
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