A simple route to synthesize mesoporous ZSM-5 templated by ammonium-modified chitosan

Article abstract of DOI:10.1002/chem.201201614

Uniform mesoporous zeolite ZSM-5 crystals have been successfully fabricated through a simple hydrothermal synthetic method by utilizing ammonium-modified chitosan and tetrapropylammonium hydroxide (TPAOH) as the meso- and microscale template, respectively. It was revealed that mesopores with diameters of 5-20nm coexisted with microporous network within mesoporous ZSM-5 crystals. Ammonium-modified chitosan was demonstrated to serve as a mesoporogen, self-assembling with the zeolite precursor through strong static interactions. As expected, the prepared mesoporous ZSM-5 exhibited greatly enhanced catalytic activities compared with conventional ZSM-5 and Al-MCM-41 in reactions involving bulky molecules, such as the Claisen-Schmidt condensation of 2-hydroxyacetophenone with benzaldehyde and the esterification reaction of dodecanoic acid and 2-ethylhexanol. Mesoporous zeolite: Ammonium-modified chitosan served as a mesoporogen in the hydrothermal synthesis of mesoporous zeolite Socony Mobil (ZSM)-5, self-assembling with the zeolite precursor through strong static interactions (see figure; TPA=tetrapropylammonium, HTCC=N-(2-hydroxy)propyl-3-trimethylammonium chitosan chloride).

Full text of DOI:10.1002/chem.201201614

FULL PAPER
DOI: 10.1002/chem.201201614
A Simple Route to Synthesize Mesoporous ZSM-5 Templated by
Ammonium-Modified Chitosan**
Junjiang Jin,[a] Xingdi Zhang,[a] Yongsheng Li,*[a] Hua Li,[a] Wei Wu,[b] Yunlong Cui,[a]
Qian Chen,[a] Liang Li,[a] Jinlou Gu,[a] Wenru Zhao,[a] and Jianlin Shi*[b]
Abstract: Uniform mesoporous zeolite
ZSM-5 crystals have been successfully
fabricated through a simple hydrother-
mal synthetic method by utilizing am-
monium-modified chitosan and tetra-
propylammonium hydroxide (TPAOH)
as the meso- and microscale template,
respectively. It was revealed that meso-
pores with diameters of 5–20 nm coex-
isted with microporous network within
mesoporous ZSM-5 crystals. Ammoni-
um-modified chitosan was demonstrat-
ed to serve as a mesoporogen, self-as-
sembling with the zeolite precursor
through strong static interactions. As
expected, the prepared mesoporous
ZSM-5 exhibited greatly enhanced cat-
alytic activities compared with conven-
tional ZSM-5 and Al-MCM-41 in reac-
tions involving bulky molecules, such
as the Claisen–Schmidt condensation
of 2-hydroxyacetophenone with benzal-
dehyde and the esterification reaction
of dodecanoic acid and 2-ethylhexanol.
Keywords: ammonium · chitosan ·
heterogeneous
catalysis
·
self-assembly · zeolites
Introduction
and intricate channels, high thermal and hydrothermal sta-
bilities, and well-defined micropores with excellent shape-se-
lectivity in catalysis.[2] However, zeolite catalysts often suffer
from the slow diffusion of reactants and products in their
relatively small pore channels (<1.5 nm),[2a,b,3] especially for
bulky molecules. To overcome this drawback, various at-
tempts have been made, such as the synthesis of zeolite
nanocrystals,[4] ultra-large pore zeolites,[2a,b,5] supported zeo-
lite crystals,[6] and ordered mesoporous materials.[7]
In the past decade, hierarchically porous materials with
well-defined pore dimensions and architectures have gained
increasing attention due to the multiple benefits from the
combination of different pore-size systems within one unit.[1]
For instance, the presence of macro- and mesoporosity can
improve the mass transport, which is very important in the
processes involving bulky molecules, whereas the presence
of meso- and microporosity would provide a large surface
area for the high dispersion of active sites.[1a,b,d] Mesoporous
zeolites are one typical example of such hierarchical materi-
als.
Zeolite nanocrystals expose more active sites than con-
ventional zeolite crystals due to their larger external surface
area. However, the difficulty to separate zeolite nanocrystals
from the slurry mixture remains a problem in liquid-phase
reactions.[3a] The successful synthesis of ultra-large pore zeo-
lites provides one route to solve the limitation of mass trans-
fer and catalytic conversion in which bulky molecules are in-
volved, but the high cost of employing specific organic tem-
plates and the relatively low stability hinder their wide ap-
plications in industry.[8] The challenge of supported zeolite
crystals is the demand of hydrothermally stable and alkali-
tolerable porous supports. In the past two decades, the suc-
cessful synthesis of ordered mesoporous materials opens a
new avenue to overcome this drawback of microporous zeo-
lites. Unfortunately, it is the amorphous nature of the meso-
porous wall that determines their low hydrothermal stability
and acidity compared with zeolite crystals.[2a,b] Therefore, it
is highly desirable to enhance the hydrothermal stability and
acidity of mesoporous aluminosilicates. Mesoporous zeolites,
which combine the advantages of microporous materials
with high activity and stability and of mesoporous materials
with large mesoporosity, are the most promising materials.
A wide variety of strategies have been developed to intro-
duce mesoporosity into zeolite crystals, such as the post-
treatment of zeolites by steaming, acid or base leaching,[9]
Crystalline zeolites are among the most important cata-
lysts in industry, which have been widely used in oil refining,
organic synthesis, and environmental fields due to their
large specific surface area, high adsorption capacity, uniform
[a] Dr. J. Jin, X. Zhang, Prof. Y. Li, Dr. H. Li, Y. Cui, Q. Chen,
Dr. L. Li, Dr. J. Gu, Dr. W. Zhao
Key Laboratory for Ultrafine Materials
of Ministry of Education
School of Materials Science and Engineering
East China University of Science and Technology
No. 130 Mei-long Road, Shanghai 200237 (P.R. China)
Fax : (+86)21-64250740
E-mail: ysli@ecust.edu.cn
[b] W. Wu, Prof. J. Shi
State Key Laboratory of
High Performance Ceramics and Superfine Microstructures
Shanghai Institute of Ceramics, Chinese Academy of Science
No. 1295 Ding-xi Road, Shanghai 200050 (P.R. China)
E-mail: jlshi@mail.sic.ac.cn
[**] ZSM=Zeolite socony mobil.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201201614.
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the assembly of zeolite nanocrystals without any secondary
porogen,[10] and the creation of mesopores by using nano-
structured carbons,[11] polymers,[12] surfactants[13] and inor-
ganic nanoparticles.[14] Recently, Ryoo and co-workers fabri-
cated truly ordered mesoporous mordenite framework in-
verted (MFI) by using linear gemini-type templates consist-
ing of several bridged ammonium cations terminated by
long alkyl chains.[13j] To avoid the phase-separation process
ployed to characterize the obtained products. Its catalytic
activity was verified in reactions involving bulky molecules,
the Claisen–Schmidt condensation of 2-hydroxyacetophe-
none with benzaldehyde and the esterification reaction of
lauric acid with 2-ethylhexanol, compared with those of con-
ventional ZSM-5 and Al-MCM-41.
between the mesoporogen and the crystalline wall,
a
Results and Discussion
number of attempts have been made, including using cation-
ic polymer or surfactant template,[12c,f,13a,b,k] silane-functional-
ized surfactant or polymer,[12b,13e] steam-assisted crystalliza-
tion,[11a,f,12g,13i] and dense mesoporogen/silica composite hy-
drothermal crystallization.[11b,c,12d] However, the above syn-
theses employed the elaborately built “hard” porogens in-
cluding carbon nanotubes, carbon particles and pre-
organized carbon scaffolds, or soft templates, such as spe-
cially designed dual-functional and environmental-unfriend-
ly surfactants, which involved either multi-step procedures
or less cost-effective templates in the synthesis. Therefore,
the simple synthesis of mesoporous zeolites by using more
conventional, environmentally friendly and cost-effective
templates is still a challenge.
Ammonium-modified chitosan, N-(2-hydroxy)propyl-3-tri-
methylammonium chitosan chloride (HTCC) was obtained
by the reaction of glycidyltrimethylammonium chloride
(GTMAC) and chitosan. The FTIR spectra of chitosan and
HTCC are presented in Figure S1 in the Supporting Infor-
mation. In spectrum a, the broad peak at 3400–3000 cmÀ1, as
À
À
well known, can be attributed to O H and N H stretching
vibrations, and the peak at 1600 cmÀ1 corresponds to NH2
deformation. In the spectrum b, a new peak positioned at
1485 cmÀ1 appears, which corresponds to the C H bending
À
of methyl groups of quaternary ammonium, indicating the
introduction of quaternary ammonium group on the HTCC
chains. Moreover, compared with the negligible change in
the characteristic peaks of primary alcohol and secondary
alcohol between 1110 and 1070 cmÀ1, the peak at 3400–
3000 cmÀ1 becomes sharper and the peak at 1600 cmÀ1 disap-
pears in the spectrum b, demonstrating that GTMAC
mainly reacted with NH2 groups in chitosan rather than with
the OH groups.[17] Due to the introduction of cationic am-
monium groups into the chitosan chains, the dissolubility of
HTCC is greatly improved, as shown in Figure S2 in the
Supporting Information, whose solution is transparent with-
out any precipitate.
Chitosan, or poly(b-ACTHNUTRGNEUNG(1-4)-2-amino-2-deoxy-d-glucose), is
the deacetylated natural product of chitin by simple alkali
treatment, which is an abundant, low-cost, highly environ-
mentally friendly and biocompatible biopolymer in the exo-
skeleton of crustaceans. The porogenic capability of chitosan
was verified in literature by using titania or silica as the inor-
ganic component in the composites.[15] Recently, amorphous
mesoporous silica–alumina was synthesized by means of the
formation of inorganic–organic composites with the addition
of chitosan biopolymer, and enhanced activity and accessi-
bility were observed in the chitosan-containing catalyst.[16]
Unfortunately, however, its indissolubility under basic condi-
tion, which is usually required in the crystallization of zeo-
lites, makes it difficult to synthesize mesoporous zeolites
using chitosan biopolymer as mesoporogens. To the best of
our knowledge, there are no reports on the synthesis of mes-
oporous zeolites using chitosan as mesoporogens directly to
date.
The success of using cationic polymers in such a synthesis
inspired us to functionalize the chitosan with ammonium for
improving its base-dissolubility and enhancing the interac-
tion between positively charged ammonium-modified chito-
san and the negatively charged inorganic precursor simulta-
neously. Moreover, the higher thermal stability of ammoni-
um-modified chitosan assures its high dispersion in the zeo-
lite synthesis systems without decomposition.[17]
Figure 1a shows the XRD patterns of mesoporous ZSM-5
(designated as MZ) and conventional ZSM-5. MZ exhibits
the characteristic peaks associated with the MFI zeolite
structure, the same as that of conventional ZSM-5. The
comparable intensity shows that the addition of HTCC did
not affect the crystallization significantly.
N2 adsorption-desorption isotherms and Barrett–Joyner–
Halenda (BJH) pore-size distribution of MZ and conven-
tional ZSM-5 are given in Figure 1b. Conventional ZSM-5
exhibits a representative type I (Langmuir) isotherm accord-
ing to the classification of IUPAC, which is characteristic of
microporous materials. In contrast, the isotherm of MZ
presents a notably mixture of type I and IV, with a larger
adsorption amount and a broad hysteresis loop at the rela-
tive pressure of 0.6–0.9, indicating the presence of meso-
porosity in MZ crystals. Accordingly, the BJH pore-size dis-
tribution of MZ derived from the desorption branch reveals
the presence of mesopores in sample MZ of 5–20 nm in di-
ameter (Figure 1b, inset), again confirming the presence of
mesoporosity. As summarized in Table 1, the specific surface
area (422 m2 gÀ1), external specific surface area (238 m2 gÀ1),
total pore volume (0.42 cm3 gÀ1), and external volume
(0.34 cm3 gÀ1) of MZ are larger than those of conventional
ZSM-5 due to the introduction of mesoporosity. Such in-
In this work, we first synthesized cationic N-(2-hydroxy)-
propyl-3-trimethylammonium chitosan chloride (HTCC) by
the reaction of glycidyltrimethylammonium chloride
(GTMAC) and chitosan, and investigated its potentiality as
the meso-template in the hydrothermal synthesis of mesopo-
rous ZSM-5 material. Various technologies including XRD,
N2 adsorption, SEM, TEM, NMR spectroscopy, TGA, and
temperature-programmed desorption (NH3-TPD) were em-
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Mesoporous ZSM-5 Crystals
FULL PAPER
Figure 2. a) and b) SEM images of MZ under different magnifications;
c) HR-TEM image of MZ; d) HR-TEM image from the area marked by
a white square in c); e) bright-field image of MZ and its corresponding
SAED pattern (inset); f) dark-field image taken on the same area with
e).
Figure 1. a) XRD pattern and b) N2 sorption isotherms and pore-size dis-
tribution curve (inset in b) of conventional ZSM-5 and MZ.
creases are believed to facilitate catalytic reactions involving
bulky molecules, despite a slight decrease in the zeolite crys-
tallinity.[12c]
of the particles, which is in agreement with the nitrogen
sorption results. In the HR-TEM images (Figure 2c and d),
some bright regions are clearly observed through the whole
particle, implying the presence of mesopores. Moreover, the
apparently continuous and well-crystallized lattice fringes of
the particle (Figure 2d) demonstrate the single-crystal
nature of MZ. To investigate its hierarchical structure more
thoroughly, the acquisition of projection images was also
performed with scanning transmission electron microscopy
(STEM), as shown in Figure 2e and f. The selected-area
electron diffraction (SAED) pattern (Figure 2e,
Scanning electron microscopy (SEM) and transmission
electron microscopy (TEM) observations provide detailed
insights into the morphology and structure of the samples.
Figure 2a and b clearly show that MZ particles exhibit ex-
tremely rough surfaces and are composed of uniform and
fluffy cylindrical-like particles, about 250ꢁ500 nm in size.
Mesopores estimated to be 5–20 nm within particles can be
clearly observed in Figure 2b, open at the external surface
inset) verifies that the particle is a single crystal. It
can be seen that some dark regions are dispersed
Table 1. Textural properties of the samples.[a]
Sample
SBET
[m2 gÀ1
Smicro
[m2 gÀ1
Sexternal Vtotal
[m2 gÀ1 [cm3 gÀ1
Vmicro
[cm3 gÀ1
Vexternal
[cm3 gÀ1
Mesopore
diameter
[nm]
over the bright contrast, as arrows point in Fig-
ure 2 f, displaying as a bright contrast in the bright-
field image inversely (Figure 2e). As this mode is
mass-thickness sensitive, it can be concluded that
mesoporous ZSM-5 was fabricated successfully, in
which mesopores co-existed with three-dimension-
al microporosity of zeolite framework.
The structural configuration and the local envi-
ronment of Si and Al atoms were investigated by
29Si and 27Al MAS NMR spectroscopy as shown in
Figure 3. It is found that MZ and conventional
G
]
R
]
G
]
U
]
G
]
R
]
MZ
422
184
287
238
108
0.42
0.19
0.08
0.11
0.34
0.08
5–20
–
Conventional 395
ZSM-5
Al-MCM-41 966
–
966
0.87
–
0.87
2.7
[a] BET surface area (SBET) is calculated from Brunauer–Emmett–Teller method; the
micropore surface area (Smicro), external specific surface area (Sexternal) and the micro-
pore volume (Vmicro) are calculated from t-plot method; the total pore volume (Vtotal
is evaluated at P/P0 =0.98; the external pore volume (Vexternal) is calculated according
to VtotalÀVmicro; the diameter of mesopore is estimated from BJH method using the de-
sorption branch of the isotherm curves.
)
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16551

Y. Li, J. Shi et al.
be attributed to the release of adsorbed water. The weight
losses of about 48.5 and 41.3% at 240–3408C and 340–
5708C correspond to the different thermal degradation steps
of HTCC.[18] At 5708C or above, HTCC decomposed com-
pletely. Conventional ZSM-5 zeolite shows a weight loss of
11.8% attributable to the loss of water and the decomposi-
tion of TPAOH (Figure S3b in the Supporting Information).
The as-synthesized MZ displays a weight loss of 17.5% at
8008C. The slight weight loss below 1508C is due to the re-
moval of absorbed water in MZ. The distinct weight loss of
1.9% within 240–3508C can be ascribed to the initial de-
composition of HTCC. However, the further decomposition
of HTCC between 340 and 5708C overlaps with that of
TPAOH, which is usually at 440–5108C.[12e] Therefore, it can
be estimated that the amount of polymer entrapped within
crystals is about 3.5%. It is noteworthy that the higher
weight loss in MZ than that in conventional ZSM-5 demon-
strates that more organics were entrapped in the as-synthe-
sized sample MZ, acting like a meso-template.
It is evident that the formation of MZ should be ascribed
to the introduction of cationic polymer HTCC. Thus, we
propose a Scheme for the synthesis of MZ under hydrother-
mal condition as shown in Scheme 1. Zeolite precursors
Figure 3. a) 29Si and b) 27Al MAS NMR spectra of MZ, conventional
ZSM-5 and Al-MCM-41.
ZSM-5 display similar 29Si MAS NMR spectra, both showing
one major peak at d=À113 ppm and a weak shoulder at d=
À105 ppm, which correspond to Si
(OSi)4 (Q4) and (AlO)1Si-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG(OSi)3, respectively. On the contrary, three peaks and one
shoulder with chemical shifts of d=À92, À100, À108, and
À105 ppm are observed in Al-MCM-41, which can be ascri-
bed to (HO)2Si
(Q4), and (AlO)1Si
ACTHNUGRTNE(NUG OSi)3, respectively. The remarkably
ACHTUNGTRENNUNG ACHTNUREGTNNUNG ACTHGUNTREN(UNNG OSi)4
(OSi)2 (Q2), (HO)Si(OSi)3 (Q3), Si
higher Q4/Q3 ratio of MZ indicates its higher condensation
level compared with that of amorphous Al-MCM-41. The
27Al MAS NMR spectra of both conventional ZSM-5 and
MZ exhibit a pronounced peak centered at around d=
55 ppm and a weak peak centered at around d=0 ppm that
can be attributed to aluminum species with tetrahedral and
octahedral coordination, respectively. This result demon-
strates that most Al atoms in MZ have been incorporated
into the framework dominantly as can be judged from its
weak peak at d=0 ppm. Correspondingly, it can be inferred
that MZ and conventional ZSM-5 possess similar acidic
properties with higher concentration of strong or medium
acid sites than that of Al-MCM-41.
Scheme 1. Proposed route for the synthesis of MZ by the self-assembly
between the zeolite precursor and HTCC under hydrothermal conditions.
were prepared according to the previous work.[13k] After the
addition of HTCC solution into the zeolite precursors, self-
assembly between the zeolite precursors and cationic HTCC
molecules took place through strong static interactions,
forming the subnanocrystals/polymer composite. Then, hier-
archical zeolite crystals with penetrating HTCC were syn-
thesized during the hydrothermal treatment. Finally, meso-
porous ZSM-5 particles were obtained after the removal of
organic HTCC and TPAOH by calcination. It is noteworthy
that the process proposed here is different from those pro-
posed in the literature elsewhere, in which cationic polymer
Thermogravimetric analyses (TGA) were performed to
estimate the entrapment and amount of polymer HTCC
during the synthesis of MZ. As shown in Figure S3a in the
Supporting Information, HTCC shows three distinct steps in
the weight loss. Reduction of the sample below 1508C can
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Mesoporous ZSM-5 Crystals
FULL PAPER
Table 2. Catalytic properties of MZ and other aluminosilicate
materials.[a]
served as a flocculating agent to form stable, easily retrieva-
ble aggregates.[12f,19]
Reactions
MZ
Conventional
Al-MCM-41
ACHTUNGTRENNUNG
Figure 4 shows the temperature-programmed desorption
of ammonia (NH3-TPD) profiles of MZ, conventional ZSM-
5 and Al-MCM-41 with the same Si/Al ratio of 50. Appa-
rently, the profile of MZ is more alike to that of convention-
al ZSM-5, indicating their similar acidic features despite of
A
2-hydroxyacetophenone 22.8
+benzaldehyde
lauric acid
6.4
G
17.4
(67:33:0)
10.7
A
ACHTUNGTRENNUNG
+2-ethylhexanol
[a] Catalytic properties were compared on the basis of the same weight
of the catalysts (see the Experimental Section for details). All catalysts
had the same Si/Al ratio of 50. [b] The first data value represents the re-
actant conversion [%]. The numbers in parentheses indicate the percent-
age selectivity of flavanone/chalcone/others.
(22.8, 14.0%) than either amorphous Al-MCM-41 (17.4,
10.7%) or bulky ZSM-5 (6.4, 8.1%) in both reactions. Com-
pared with conventional ZSM-5, the higher activities of MZ
should be ascribed to the introduction of intracrystalline
mesopores, enhancing the efficient diffusion of reactant/
product molecules through the solid catalyst. It was reported
that the condensation reaction would occur at the external
surface Al species irrespective of their acidic strength.[22]
Thus, the higher activity of MZ (22.8%) than that of Al-
MCM-41 (17.4%) in the condensation reaction may be also
caused by the creation of relatively larger mesopores of
about 5–20 nm, which is much larger than that of Al-MCM-
41 (2.7 nm), taking the higher Alexternal/Alframework ratio for
Al-MCM-41 into account. It is well known that the esterifi-
cation reaction of such bulky molecules requires a catalyst
with strong acid sites. Thus, the better performance of MZ
than Al-MCM-41 in the esterification reaction of lauric acid
with 2-ethylhexanol perhaps can be attributed to the higher
concentration of medium and strong acid sites in MZ, as
shown in Figure 4.
Figure 4. NH3-TPD profiles of conventional ZSM-5, MZ and Al-MCM-
41.
its relatively lower amount of NH3 desorption. Moreover, it
is observed that the NH3 desorption temperature of sample
MZ (3808C) is much higher than that of Al-MCM-41
(3108C) and the amount of NH3 desorbed from MZ is sig-
nificantly higher than that of Al-MCM-41, revealing the
higher concentration/strength of acid sites in MZ.
Catalytic reactions involving large molecules, the Claisen–
Schmidt condensation of 2-hydroxyacetophenone with ben-
zaldehyde and the esterification reaction of lauric acid with
2-ethylhexanol (Scheme 2), were performed to verify the
catalytic activity of MZ. Flavonoids have been found a wide
range of applications, such as UV protection, flower colora-
tion, interspecies interactions and plant defense, and they
can also offer nutritional and medicinal values to humans.[20]
Batch esterification reactions catalyzed by solid acids pro-
vides an alternate route to the manufacture of the main
components of biodiesel.[21] Table 2 summarizes the catalytic
data. As expected, MZ shows higher catalytic activities
Conclusion
A hierarchically porous aluminosilicate with micro/mesopo-
rous structure, meosoprous ZSM-5, has been successfully
synthesized by a conventional hydrothermal method using
ammonium-modified chitosan and TPAOH as the meso-
and microscale template, respectively. Various characteriza-
tion technologies revealed that mesoporosity of about 5–
20 nm in diameter coexisted with micropore network within
uniform mesoporous ZSM-5 crystals. It was demonstrated
that the ammonium-modified chitosan served as a mesopor-
ogen, which can self-assemble with the zeolite precursor
through strong static interactions, forming mesoporous zeo-
lite ZSM-5. Due to the high specific surface area, external
specific surface area, total pore volume, external volume
and high concentration of medium and strong acid sites,
mesoporous ZSM-5 exhibited significantly enhanced catalyt-
ic activities compared with conventional ZSM-5 and Al-
MCM-41 in reactions involving bulky molecules. It is ex-
pected that this synthetic strategy can be applied to other
structured zeolites, such as Y, TS-1, Beta zeolites, and so on.
Scheme 2. Claisen–Schmidt condensation of 2-hydroxyacetophenone with
benzaldehyde (top); esterification reaction of lauric acid with 2-ethylhex-
anol (bottom).
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Y. Li, J. Shi et al.
Experimental Section
Acknowledgements
This work was financially supported by the National Basic Research Pro-
gram of China (973 Program, 2012CB933602); Program for New Century
Excellent Talents in University (NCET-10-0379); Scientific Innovation
Project of Shanghai Municipal Education Commission (Grant No.
11ZZ53); The National Natural Science Foundation of China (Grant
Nos. 51172070, 51132009), The Fundamental Research Funds for the
Central Universities (Grant No. WD1114002 and WK1013001).
Synthesis of HTCC: The ammonium-modified chitosan, N-(2-hydroxy)-
propyl-3-trimethyl ammonium chitosan chloride (HTCC) was synthesized
according to a method described elsewhere.[17] Chitosan with a molecular
weight of 100000 gmolÀ1 was used here.
Synthesis of mesoporous ZSM-5: In a typical synthesis, AlACTHUNRGTNEUNG(iPro)3 (0.31 g,
1.50 mol) and TEOS (15.62 g, 0.075 mol) were mixed with deionized
water (25.92 g), forming an oil-in-water emulsion at room temperature.
After stirring for 2 h, TPAOH (25% aqueous, 21.96 g, 0.027 mol) was
added into the resultant emulsion dropwise, which became a clear solu-
tion after stirring at 408C for 2–3 h. Then, the temperature was raised to
1008C and maintained for 2 days. The molar ratio in the precursor was
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AlACHTUNGTRENNUNG(iPro)3/TPAOH/TEOS/H2O=1:18:50:1570, and the entire reaction was
carried out in a closed Schott Duran bottle.
After cooling the precursor solution to room temperature, the suspension
was mixed with an aqueous solution of HTCC and stirred for 2 h at
808C. At last, the obtained earth yellow mixture was charged into
Teflon-lined steel autoclaves for hydrothermal treatment at 1508C for
18 h. The final products were filtered, washed with deionized water,
dried overnight at 1008C and calcined at 6508C for 10 h. The obtained
sample was designated as MZ. For comparison, conventional ZSM-5 and
Al-MCM-41 with Si/Al=50 were also synthesized according to the litera-
ture procedures.[13e,23] All the samples were converted into the H-form by
ion exchanges with 1m NH4NO3 solution at 808C for three times and sub-
sequent calcination in air at 5508C for 5 h.
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Characterization: Fourier transform infrared spectroscopy (FTIR) meas-
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XRD patterns were collected on Bruker D8 Focus diffractometer with a
graphite-monochromatized CuKa radiation (l=0.15405 nm), typically run
at a voltage of 40 kV and current of 40 mA. The N2 adsorption isotherms
were measured using Quantachrome NOVA 4200e. The specific surface
area and pore size distribution were calculated by using the Brunauer–
Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) method, re-
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under the atmosphere of air at a heating rate of 108CminÀ1 using a
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1008C for 1 h. Then the temperature was raised from 100 to 5508C with
a heating rate of 18CminÀ1 and the desorbed NH3 was detected by gas
chromatography. The ratios of Si/Al in different samples were deter-
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Received: May 8, 2012
Revised: September 19, 2012
Published online: November 5, 2012
Chem. Eur. J. 2012, 18, 16549 – 16555
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
16555