Mesoporogen-Free Synthesis of High-Silica Hierarchically Structured ZSM-5 Zeolites and their Superior Performance for the Methanol-to-Propylene Reaction

Article abstract of DOI:10.1002/ejic.201800926

A series of hierarchically structured ZSM-5 zeolites (ZSM-5 HSZs) with a Si/Al ratio of about 200 have been successfully synthesized in the absence of additional mesoporous agents. XRD, N₂ sorption isotherms, SEM, TEM and NH₃-TPD results showed that the obtained HSZs materials possess high crystallinity, interconnected micro/mesoporous structures and similar total acid amounts. Meanwhile, in the methanol-to-propylene (MTP) reaction, compared to the microporous counterpart, all synthesized ZSM-5 HSZs demonstrated superior performance benefitting from their hierarchical porous structures. Interestingly, ²⁷Al MAS NMR and Py-FTIR results confirmed the inter-transformation of framework and extra-framework Al species with the extension of materials crystallization duration and consequently the variation of materials surface acidity. As a result, the optimized catalyst achieved the highest initial propylene selectivity of 54.4 % and the longest catalyst lifetime (t₉₀) of 175 h under the weight hourly space velocity (WHSV) of 1.0 g g^–1 h^–1. Moreover, a new “in situ alkali etching-hydrothermal restoring“ mechanism has been proposed to elucidate the structural evolution of here reported high-silica ZSM-5 HSZs during the synthesis.

Full text of DOI:10.1002/ejic.201800926

A Journal of
Accepted Article
Title: Mesoporogen-free synthesis of high-silica hierarchically
structured ZSM-5 zeolites and their superior performance for
methanol-to-propylene reaction
Authors: Hangle Guo, Tongguang Ge, Jian Lv, Changlin Du, Jian
Zhou, Zhicheng Liu, and Zile Hua
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201800926
Link to VoR: http://dx.doi.org/10.1002/ejic.201800926

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
Mesoporogen-free synthesis of high-silica hierarchically
structured ZSM-5 zeolites and their superior performance for
methanol-to-propylene reaction
Hangle Guo,[a, b] Tongguang Ge, [a, b] Jian Lv, [a, b] Changlin Du, [a, b] Jian Zhou, *[c] Zhicheng Liu,[c] and
Zile Hua*[a]
Abstract: A series of hierarchically structured ZSM-5 zeolites (ZSM-
5 HSZs) with a Si/Al ratio of about 200 have been successfully
synthesized in the absence of additional mesoporous agents. XRD,
N2 sorption isotherms, SEM, TEM and NH3-TPD results showed that
the obtained HSZs materials possess high crystallinity,
interconnected micro/mesoporous structures and similar total acid
amounts. Meanwhile, in the methanol-to-propylene (MTP) reaction,
compared to the microporous counterpart, all synthesized ZSM-5
HSZs demonstrated superior performance benefitting from their
hierarchical porous structures. Interestingly, 27Al MAS NMR and Py-
FTIR results confirmed the inter-transformation of framework and
extra-framework Al species with the extension of materials
crystallization duration and consequently the variation of materials
surface acidity. As a result, the optimized catalyst achieved the
highest initial propylene selectivity of 54.4% and the longest catalyst
lifetime (t90) of 175 h under the weight hourly space velocity (WHSV)
of 1.0 g g-1 h-1. Moreover, a new “in situ alkali etching-hydrothermal
restoring” mechanism has been proposed to elucidate the structural
evolution of here reported high-silica ZSM-5 HSZs during the
synthesis.
commonly accepted, in which the relative propagation extent of
the aromatic-based cycle and the olefins-based one determines
the product distributions in the effluent. [2] When propylene is the
main target product, known as methanol-to-propylene (MTP)
reaction, ZSM-5 zeolites with MFI-type topology structure are
the most promising candidates due to their adjustable surface
acidity, high stability, 3D-connected and suitable microporous
[3]
system.
In recent years, aiming at the improvement of
selectivity of target propylene and catalyst lifetime in MTP
reaction, researches on the newly structured ZSM-5-based
catalyst have been attracting increasing concerns from both
industry and academia. [4]
The acid sites in ZSM-5 zeolites are the active centers for
MTP reaction, but also catalyze the undesired secondary
reactions, i.e. hydrogen transfer, cyclization and aromatization
reactions. [5] Especially for high-alumina ZSM-5, the high-density
acid sites would induce the serious secondary reactions, which
leads to the decrease of target propylene selectivity and the
rapid deactivation of catalysts. Therefore, high-silica ZSM-5 is
the preferred catalyst for MTP. For instance, Mei et al. found that
when the Si/Al ratio of ZSM-5 catalysts increased from ca. 10 to
110, the catalyst lifetime would be increased by more than 5
times and the propylene selectivity increased by about 10%. [3a]
On the other hand, elemental modification and/or post-synthesis
treatment are also adopted for the surface acidity adjustment of
ZSM-5 to suppress the possible side reactions. Hu et al. even
modified the acidity of ZSM-5 zeolites by boron incorporation.
The followed tests showed that, compared to unmodified ZSM-5
zeolites, the stability of boron incorporated ZSM-5 zeolites were
significantly improved. [3c] Yarulina et al. found that Ca2+-modified
ZSM-5 had a twofold increase of propylene selectivity and a nine
times longer catalyst lifetime in MTO reaction. Possible reasons
lie in the transformation of Brønsted acid sites (BAS) to Lewis
acid ones (LAS) and the decrease of acid strength resulting from
the calcium modification. [6]
Introduction
The catalytic conversion of methanol-to-olefins (MTO) over
acidic zeolites, as an alternative to the traditional petrochemical
route, not only alleviates the contradiction between the growing
demand of olefins and the limited petroleum reservoirs, but also
agrees with the concept of green and sustainable chemistry
strategy, because the process for methanol production is diverse
from coal, natural gas, renewable biomass, and even CO2. [1] Up
to now, although dispute still exists about the detailed course in
MTO reaction, a dual-cycle hydrocarbon pool mechanism is
Besides surface acidity, the textural property is another critical
parameter influencing the catalyst performance in MTP. For
conventional ZSM-5 zeolites, the sole presence of microporous
channels hinders the diffusion of reactants and products in them
and consequently increases the residence time of product
propylene, which increase the probability of side reactions even
with high-silica materials. More importantly, once a channel is
blocked by coke species, the nearby zones may become less
connected with the outside, which makes it difficult for the
[a]
Mr. Hangle Guo, Dr. Tongguang Ge, Dr. Jian Lv, Mr. Changlin Du,
Prof. Dr. Zile Hua
State Key Laboratory of High Performance Ceramics and Superfine
Microstructure
Shanghai Institute of Ceramics, Chinese Academy of Sciences
1295 Dingxi Road, Shanghai 200050, P.R. China
E-mail: huazl@mail.sic.ac.cn
Mr. Hangle Guo, Dr. Tongguang Ge, Dr. Jian Lv, Mr. Changlin Du
University of Chinese Academy of Sciences
No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, P.R.
China
[b]
[c]
reactants to approach the active sites in reality and thus lead to
[7]
Dr. Jian Zhou, Dr. Zhicheng Liu
the catalyst gradual deactivation.
To enhance the mass
Sinopec Shanghai Research Institute of Petrochemical Technology
1658 Pudong North Road, Shanghai 201208, P.R. China
E-mail: zjcx1984@gmail.com
diffusion in the zeolite catalysts, hierarchically structured zeolites
(HSZs) have made great progress recently through top-down
process [8] or bottom-up synthesis. [4b, 9] Zhang et al. used a spent
zeolite catalyst as part of silica/alumina raw materials and the
attached coke species as the template to synthesize mesopore-
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
containing ZSM-5 zeolites. Interestingly, compared to the parent
zeolite, the catalytic lifetime of the refabricated ZSM-5 catalyst
crystallized materials. Because only highly crystallized zeolites
shows apparent catalytic activities in MTP, the following
characterizations are mainly focused on HSZs-5, HSZs-10 and
HSZs-48.
increased by two times and the propylene selectivity increased
[4b]
by
7%.
Kim
et
al.
designed
3-
[(trimethoxysilyl)propyl]hexadecyldimethylammonium
(TPHAC) organosilanes as the mesopore-directing surfactants
to synthesize mesoporous ZSM-5 zeolites. Catalytic results
chloride
N2 sorption isotherms of synthesized HSZs-t and conventional
ZSM-5(200) are shown in Figure 1b and Figure S1b, and their
textural properties are summarized in Table 1 and Table S1. As
expected, the isotherm of ZSM-5(200) exhibits the typical type I
profile with a sharp uptake in the range of P/P0 < 0.1 and a
plateau at 0.4 < P/P0 < 1.0, which belongs to the microporous
materials. The specific surface area (SBET) and the total pore
volume (Vtotal) of ZSM-5(200) are 367 m2 g−1 and 0.21 cm3 g−1,
respectively. In contrast, HSZs-5, HSZs-10 and HSZs-48 exhibit
the typical type IV isotherms with a hysteresis loop and an
uptake at high relative pressures (0.4 < P/P0 < 1.0). Moreover,
compared with microporous ZSM-5(200), HSZs materials (entry
1-3 in Table 1) shows larger specific surface areas and pore
volumes. The corresponding pore size distributions (PSDs) are
shown in Figure S2. Although the difference is small among
them, in the range of 2.0~10.0 nm the three synthesized HSZs
materials demonstrate a slightly higher PSDs compared to ZSM-
5(200). On the other hand, it is noted that the effect of
prolonging crystallization duration on HSZs textural properties is
insignificant, although HSZs-48 shows a slightly lower external
surface area. It is consistent with above XRD conclusion that
under the here synthesis conditions, high-silica HSZs could
achieve high crystallinity in a short crystallization duration. Both
of them proves that the successful synthesis of high-silica HSZs
has been realized in the absence of additional mesopore agents
through the DGC procedure.
showed that the resultant materials have the stronger resistance
[4a]
to deactivation than microporous zeolites.
Unfortunately,
template synthesis of HSZs is not a cost-effective and highly
efficient method and the post-synthesis elimination of templates
would emit a large amounts of greenhouse gases. From the
point of view of potential applications, synthesis of HSZs in the
absence of additional mesoporogens is desired. [10]
Very recently, based on the dry-gel crystallization (DGC)
conversion course, a mesoporogen-free method for synthesis of
ZSM-5 HSZs have been developed in our group. [11] Here, this
method have been extended for synthesis of high-silica ZSM-5
HSZs with a Si/Al ratio of as high as around 200 and their
potential applications in MTP reaction have been explored. As
expected, all synthesized HSZs catalysts showed the superior
performance in MTP reaction, which means high initial
propylene selectivity (52.0+%) and long catalyst lifetime (t90, 66+
h) under the WHSV of 1.0 g g-1 h-1. In contrast, the microporous
ZSM-5 counterpart showed an initial propylene selectivity of only
47.8% and a catalyst lifetime of as short as 13 h. More
interestingly, the inter-transformation between BAS and LAS
during DGC synthesis was reported with the extension of
crystallization duration. As a result, the optimized catalyst
achieved the highest initial propylene selectivity of 54.4% and
the longest catalyst lifetime of 175 h in MTP reaction. Moreover,
a new “in situ alkali etching-hydrothermal restoring” mechanism
has been proposed to demonstrate the structural evolution of
here reported high-silica ZSM-5 HSZs during DGC synthesis.
Results and Discussion
Physicochemical properties of synthesized HSZs-t and
ZSM-5(200)
XRD patterns of the synthesized HSZs-t (hierarchically
structured ZSM-5 zeolites synthesized by steam-assisted
crystallization, in which t refers to the crystallization duration (h))
and ZSM-5(200) (microporous zeolites with a Si/Al ratio of about
200) are shown in Figure 1a and Figure S1a, and the
corresponding RCs (relative crystallinity) are listed in Table 1
and Table S1. For sample HSZs-1 and HSZs-3, only weak
diffraction peaks are observed, indicating the amorphous nature
or incomplete crystallization of synthesized materials. When the
crystallization duration extended to 5 h, the resultant HSZs-5
exhibits the typical diffraction spectrum associated with MFI-type
topology zeolites and the calculated RC is ~92%, demonstrating
its high crystallinity. Further extension of the crystallization
duration, the similar diffraction patterns are obtained as that of
HSZs-5 and the RC change is unobvious, which imply that for
sample HSZs with Si/Al ratio of about 200, as short as 5 h is
enough for the complete conversion of amorphous precursors to
Figure 1. (a) XRD patterns and (b) N2 sorption isotherms of synthesized
HSZs-t and ZSM-5(200).
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
Table 1. Textural properties, compositions and RCs of synthesized HSZs-t
and ZSM-5(200)
Entry
Sample
HSZs-5
SBET (m2/g)
491
Vtotal (cm3/g)
0.30
Si/AlICP
179
RC (%)
92
1
2
3
4
HSZs-10
HSZs-48
ZSM-5(200)
479
0.30
179
94
486
0.29
179
91
367
0.21
187
100
SEM and TEM images of synthesized HSZs and conventional
ZSM-5(200) are shown in Figure 2, Figure 3 and Figure S3.
Different from the irregular shape of amorphous gel precursors
(Figure S3), HSZs materials (Figure 2a-c) exhibit similar uniform
globular particles of 400~500 nm with rough and porous
Figure 3. TEM and HRTEM images of (a, d) HSZs-5, (b, e) HSZs-10 and (c, f)
HSZs-48. The insets in (d-f) are the corresponding electron diffraction patterns.
surfaces irrespective of the crystallization duration. As
a
comparison, the SEM image of ZSM-5(200) in Figure 2d reveals
the classical coffin-shape morphology with smooth surfaces. In
Figure 3, the TEM images of HSZs materials indicate that the
additional mesopores are present inside the zeolite particle. The
parallel lattice fringes throughout the entire particles in high
resolution TEM (HRTEM) image and the corresponding electron
diffraction (ED) pattern (inset) confirm the single-crystalline
nature of synthesized HSZs. In order to further clarify the
internal structure of synthesized HSZs, the SEM image of cross-
section polished HSZs-10 is shown in Figure 4. Disordered
mesoporous channels (e.g. the areas pointed by arrow) are
obvious, which provide large external surface areas and
mesopore volume.
Figure 4. SEM image of cross-section polished HSZs-10.
Figure 5. NH3-TPD profiles of synthesized HSZs-t and ZSM-5(200).
Figure 2. SEM images of (a) HSZs-5, (b) HSZs-10, (c) HSZs-48 and (d) ZSM-
5(200).
the NH3-TPD profiles of HSZs materials and ZSM-5(200) and
Table 2 summarizes the quantitative results. As expected, all
samples exhibit two desorption peaks at about 150 °C and
350 °C, respectively, in which the former is usually assigned to
the weak acid sites, while the latter is ascribed to the strong acid
sites and always considered as the active sites in MTP reactions.
The aluminum contents of all materials were determined by
ICP-OES and their Si/Al ratios were listed in Table 1. All
synthesized HSZs materials have similar Si/Al ratio of about 180
that is close to the designed Al content. Further, Figure 5 depicts
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
[12]
Specifically, the quantitative results indicate that all materials
possess the approximate strong acid amount of 32~42 μmol g-1.
Overall, high-silica ZSM-5 HSZs have been successfully
synthesized in the absence of additional mesoporogens. The
characterization results show that the synthesized HSZs have
high crystallinities, interconnected micro/mesoporous structures,
uniform particle size and approximate total acid amount.
Table 2. Acidic properties of synthesized HSZs-t and ZSM-5(200)
Sample
By NH3-TPD (μmol/g)
By Py-FTIR (μmol/g)
Weak
Strong
37
Total
BAS
17
15
18
-
LAS
B+L
19
20
20
-
HSZs-5
HSZs-10
47
38
42
80
84
72
2
5
2
-
34
HSZs-48
42
84
ZSM-5(200)
32
112
Catalytic performance of synthesized HSZs and ZSM-5(200)
in MTP
The catalytic results over synthesized HSZs materials and
ZSM-5(200) are shown in Figure 6 and methanol conversions
and product selectivities after
2 h time on stream are
summarized in Table S2. In general, at the initial stage of
reaction, for all catalysts, the methanol conversions are ~100%
(Figure 6a) and the selectivities to target propylene are larger
than 45.0% (Figure 6b), which reflects the high intrinsic activity
of MFI-type aluminosilicate zeolites in MTP. Afterwards,
suffering from the coke formation, all of them gradually
deactivate with time on stream. Nevertheless, their specific
performances are significantly different. For example, the
catalyst lifetimes of HSZs-5, HSZs-10, HSZs-48 and ZSM-5(200)
are about 136 h, 175 h, 66 h and 13 h, respectively, while their
initial propylene selectivities are 53.1%, 54.4%, 52.0% and
47.8%. To address these differences, the effect of catalyst pore
structures and acidic properties would be discussed separately
in the following section. For comparison, literature reports about
MTP performance over various ZSM-5-based catalysts,
especially mesostructured materials synthesized with or without
[3c, 4b, 4e, 13]
mesoporous agents, have been listed in Table S4.
Irrespective of detailed reaction conditions, here synthesized
HSZs-10 shows better results in most cases. Moreover,
considering the superiority of here reported mesoporogen-free
method for production of HSZs, its potential applications is
expectable.
Figure 6. (a) Methanol conversions and (b-d) product selectivities of the MTP
reactions over synthesized HSZs-t and ZSM-5(200). Reaction conditions:
WHSV = 1.0 g g−1 h−1, T = 460 °C, Ptotal = 1.0 atm.
Compared to microporous ZSM-5(200), the synthesized HSZs
materials exhibit better performances in the MTP reaction, that is,
longer catalyst lifetimes (Figure 6a, 66+ h vs 13 h), higher
selectivity to propylene (Figure 6b, 52.0+% vs 47.8%), and lower
selectivity to C1-C3 alkanes and C5+ compounds in the testing
period (Figure 6c&d). The latters are often referred to the
undesired by-products and/or coke precursors resulted from the
secondary reactions, i.e., hydrogen transfer, cyclization and
aromatization reactions, which lead to the decrease of target
[14]
propylene and deactivation of catalysts.
Since both HSZs
materials and ZSM-5(200) have the similar Si/Al ratios and
consequently the similar acid amounts, as shown in above ICP
(Table 1) and NH3-TPD results (Figure 5 and Table 2), it is
believed that the hierarchically micro/mesoporous system in the
HSZs, confirmed by their relatively large specific surface area
(entry 1-3 in Table 1) and interconnected micro/mesoporous
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
structures (Figure 4), is favorable for the enhancement of
materials catalytic performance. Additionally, we even
synthesized ZSM-5 HSZs with Si/Al ratio of about 400, denoted
as HSZs(400). For the same reason, although its acid amount is
much lower compared with that of ZSM-5(200), its catalyst
lifetime is about 102 h and the initial propylene selectivity is
54.1%, which are also superior to those of the latter (Table S2&3
and Figure S4).
catalysts follow the order of HSZs-10(7.50%) > HSZs-5(7.04%)
> HSZs-48(5.31%) > ZSM-5(200)(4.06%).
For the tested HSZs materials, although they have the similar
textural properties (entry 1-3 in Table 1) and the approximate
total acid amount (Figure 5 and Table 2), their difference on
MTP catalytic performance is also remarkable. In order to clarify
these differences, the analysis of 27Al MAS NMR and Py-FTIR
had been conducted. As shown in Figure 8a, HSZs-5 and HSZs-
48 exhibit a main peak centered at ca. 55 ppm, attributed to the
tetrahedrally coordinated framework Al species (FAL), while the
For HSZs catalysts, the auxiliary mesoporous structures
breaks the connectivity of the original microporous structures of
zeolites, which brings three kinds of benefits to the MTP reaction. resonances at ca. 0 ppm are very weak, which is usually
Firstly, the target propylene could diffuse from the acid sites in a
timely manner through the shortened diffusion length in
microporous channels, which inhibits the occurrence of
secondary reactions. As a result, HSZs catalysts get high
selectivity to propylene and low production of C1-C3 alkanes and
C5+ compounds, as shown in Figure 6b-d. Also, it offers a quick
path for the diffusion of bulky coke precursors out of micropore
system, e.g. aromatic species, which delays the accumulation of
coke precursors and decrease the coke formation rate in
catalysts. [4a, 4e, 15] To verify this hypothesis, the TG analysis of
spent catalysts were conducted, as shown in Figure 7.
assigned to the octahedrally coordinated extra-framework Al
species (EFAL). [17] These results demonstrate that almost all Al
atoms in HSZs-5 and HSZs-48 are isomorphous substituted for
Si atoms in Silicalite-1 frameworks. In contrast, HSZs-10 shows
a slight decrease in peak intensity at ca. 55 ppm and an
apparent peak appears at ca. 0 ppm indicating the formation of
EFAL. All these results imply that accompanying with the
extension of crystallization duration, a portion of FAL in pre-
formed HSZs materials (HSZs-5) would be removed from the
zeolite frameworks (HSZs-10) and then re-incorporated again
(HSZs-48).
Specifically, the spent microporous ZSM-5(200) exhibits
a
Figure 8b shows the Py-FTIR spectra of HSZs-5, HSZs-10
and HSZs-48, in which the bands at 1546 cm-1 and 1455 cm-1
are assigned to the pyridine chemisorbed at BAS and LAS,
weight loss of 4.06% between 300 °C and 800 °C. Considering
its lifetime of about 13 h, the corresponding average coke
formation rate is 3.1*10-3 h-1. In contrast, for HSZs-5, HSZs-10
and HSZs-48, these rates are 5.2*10-4 h-1, 4.3*10-4 h-1 and
8.0*10-4 h-1, respectively, which are decreased by 74~87% in
comparison with that of ZSM-5(200). Therefore, HSZs series
catalysts achieve long lifetime (Figure 6a). Secondly, due to the
small pore size, the available active sites for conventional
zeolites are often limited to the near pore-mouth area. The
accumulation of coke or coke precursors in this area leads to the
rapid deactivation of ZSM-5(200). However, for HSZs catalysts,
introduction of mesoporous structures provides more open
micropore mouth and more accessible active sites are thus
obtained. Consequently, under the identical MTP reaction
conditions, HSZs catalysts would demonstrate a long duration of
100% methanol conversion and the prolonged lifetime before
apparent deactivation appears. Lastly, large external surface
respectively, while the band at 1490 cm-1 corresponds to the
[5b. 6]
adsorption of pyridine on both the BAS and LAS.
The
calculated BAS and LAS amounts are summarized in Table 2.
The total amounts of BAS and LAS are almost the same among
area and pore volume with HSZs catalysts increase their coke
[3c, 16]
tolerance capacity.
When the methanol conversion
decreased to 90%, the total coke contents for four spent
Figure 8. (a) 27Al MAS NMR spectra and (b) Py-FTIR spectra after evacuation
at 200 °C of synthesized HSZs-t.
Figure 7. TG profiles of spent HSZs-t and ZSM-5(200).
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
HSZs-5, HSZs-10 and HSZs-48. However, as the crystallization
duration is extended, the concentration of BAS decreases first
and then restores, while the concentration of LAS increases first
and then declines, being consistent with the above 27Al MAS
NMR results. It is worth noting that a difference between the
quantitative results of NH3-TPD and Py-FTIR for synthesized
HSZs is observed, which may be due to their relatively low
acidic amount and the actual pyridine pre-desorption
temperature. Similar results could be found from the recent work
of Liang et al., in which the difference between the quantitative
results of NH3-TPD and Py-FTIR increases gradually with the
decrease of zeolite acidic amount. [12]
HSZs-48. Additionally, above 27Al MAS NMR and Py-FTIR
results demonstrate the (re)doping/demetallation course of
aluminum species into/from the zeolite frameworks during the
extended crystallization duration. Based on these results, here a
new “in situ alkali etching-hydrothermal restoring” mechanism is
proposed for synthesis of high-silica HSZs by DGC conversion,
as shown in Scheme 1.
The relatively low BAS concentration with sample HSZs-10
contributes to the inhibition of side reactions such as hydrogen
transfer for propylene, and may therefore suppress the
propagation of aromatic-based cycle. Moreover, a lower BAS
density may delay the further reactions of polymethylbenzenes
[18]
to form polycyclic aromatic compounds (i.e., coke precursor).
In addition, from the “in situ alkali etching-hydrothermal
restoring” mechanism proposed in this work (discussed in the
following part), the presence of alkaline “water pool” will lead to
the demetallization effect in the pre-formed zeolite particles, that
is, the acid sites on the external surface, i.e., non-selective acid
sites, may be effectively removed. As a result, the undesirable
consecutive reactions such as isomerization, alkylation and
Scheme 1. Illustration of steam-assisted crystallization process of HSZs-t. (a)
Steam-assisted crystallization system. (b) Transition state. (c) Hydrothermal
system.
In the first stage of Scheme 1a, e.g. for synthesis of HSZs-5,
the kinetically controlled nucleation-growth mechanism
oligomerization occur on the external surface acid sites are
[19]
dominates, similar to the preparation of HSZs with Si/Al ratio of
largely suppressed.
Interesting results could be found in a
[11a]
50.
Due to the low content of aluminum doping, the as-
recent publication by Gascon et al, in which a subtle interplay
between BAS and LAS sites is confirmed, from both
synthesized zeolite particles are highly crystallized in a short
time of 5 h and keeps at the dry state as the dry-gel precursors.
Importantly, nearly all Al atoms are tetrahedrally coordinated in
the zeolite framework. Meanwhile, the increased zeolite
crystallinity also leads to the enhancement of framework
hydrophobicity. [21] Therefore, when the crystallization duration is
further extended (Scheme 1b), e.g., in synthesis of HSZs-10, the
water affinity of zeolite internal/external surfaces becomes
weaker and consequently the microscopic and localized water
pools would gradually integrate with each other. As a result, the
as-synthesized materials is damp but no longer dry. Moreover,
because these integrated water pools are strongly alkaline, the
demetallation, i.e., desilication accompanying dealumination,
experimental and theoretical calculation results, to obtain an
[20]
optimally ZSM-5-based MTP catalysts.
Similar phenomena
occurred to here synthesized HSZs catalyst. Although the total
acid amounts almost kept constant for all HSZs materials,
sample HSZs-10 exhibits the best MTP catalytic performance,
i.e the highest initial propylene selectivity of 54.4%, the lowest
average coke formation rate of 4.3*10-4 h-1 and the longest
lifetime of 175 h.
Materials synthesis mechanism
In one of our primary reports about mesoporogen-free
synthesis of ZSM-5 HSZs with a Si/Al ratio of 50, a kinetically
controlled nucleation-growth mechanism has been proposed, in
which the dynamic balance between the microscopic and
would happen in the pre-formed zeolite particles, similar to the
[8c, 22]
[11a]
conventional post-alkaline etching
and in situ etching
localized water pools and the steam plays a key role.
course [23] for preparation of HSZs. Then, EFAL will appear in the
resultant materials, as shown in above 27Al MAS NMR and Py-
FTIR results. It should be noted that although the course of high-
silica HSZs is artificially divided into three stages, in practice, it
is impossible to definitely separate them from each other, and
they may occur simultaneously. Lastly, when the crystallization
duration is long enough (Scheme 1c), e.g., in the synthesis of
HSZs-48, the macroscopic “water pools” is apparent and the
Subsequently, a modified surface hydrophilicity/hydrophobicity-
regulation mechanism has been suggested to elucidate the
difference on the structural evolution of titanosilicate and
aluminosilicate zeolites. [21] However, in this study, when high-
silica ZSM-5 HSZs with a Si/Al ratio of about 200 have been
synthesized under the identical conditions, only sub-micron
particles with relatively lower mesopore volume, but neither
[21]
zeolite nanocrystals
nor HSZs with abundant mesoporous
structures, [11a] could be obtained, as shown in Figure 2&3 and
Table 1. Figure S5 are the typical digital photos of as-
synthesized HSZs materials. Apparently, with the extension of
crystallization duration, the resultant material has experienced a
transition from “dry powders” of sample HSZs-5 to “damp
powders” of sample HSZs-10, and to “precipitates” of sample
material crystallization conversion turns into
a
direct
hydrothermal system. Since the usage of alkaline source is fixed,
compared to the solution alkalinity of stage b, the relatively lower
alkalinity in stage c of direct hydrothermal system would weaken
the alkali etching effect and the EFAL would probably re-
incorporate into the defect sites of zeolite frameworks again, as
confirmed by above 27Al MAS NMR and Py-FTIR results.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
with the precursor gel. Then, the Teflon container was fitted into a
stainless steel autoclave and the autoclave was heated in a preheated
oven at 150 °C for a given period of time (t). The obtained products were
dried at 80 °C overnight and then calcined at 550 °C in static air for 6 h to
remove the organic components. To obtain the H-form zeolites, as-
synthesized HSZs materials were ion-exchanged with 1 M NH4Cl solution
three times at 80 °C for 4 h and then dried at 80 °C for 6 h. Finally, all the
NH4-form materials were calcined at 550 °C in static air for 6 h. The
resultant materials were denoted as HSZs-t, in which t refers to the
crystallization duration (h). In this work, the values of t were 1, 3, 5, 10
and 48, respectively.
Conclusions
A series of hierarchically structured ZSM-5 zeolite catalysts
(Si/Al~200) have been successfully synthesized by a facile and
eco-friendly mesoporogen-free steam-assisted crystallization
(SAC) strategy. XRD, N2 sorption isotherms, SEM and TEM
results show that the obtained HSZs materials exhibit similar
uniform globular particulate morphology (ca. 400~500 nm in
diameter)
with
high
crystallinity,
interconnected
micro/mesoporous structure and large specific surface area.
Importantly, all synthesized HSZs catalysts show excellent
catalytic performance in MTP reaction with the WHSV of 1.0 g g-
Characterization
1
h-1, i.e., high initial propylene selectivity (52.0+%) and long
The powder X-ray diffraction (XRD) patterns of samples were recorded
on a Rigaku Ultima IV X-ray diffractometer at 40 kV and 40 mA, using Cu
Kα radiation source, with a scanning rate of 5 o min-1 and an angular step
size of 0.02 o. The integrated peak areas of synthesized samples in the
catalyst lifetime (t90, 66+ h). As a comparison, the initial
propylene selectivity over microporous ZSM-5 counterpart is as
low as 47.8%, and the catalytic lifetime is only 13 h, mainly due
to the huge diffusion barrier caused by its sole microporous
system. More interestingly, it is found that with the extension of
the crystallization duration, Al dopants experienced a process of
isomorphous substitution of framework Si, dealumination from
crystallized zeolite frameworks and then re-doping into the
frameworks again, which led to the inter-transformation of
materials BAS and LAS and consequently the varied MTP
performance. Over the optimized sample HSZs-10, the highest
initial propylene selectivity of 54.4% and the longest catalyst
lifetime of 175 h are thus achieved. Accordingly, a new “in situ
alkali etching-hydrothermal restoring” mechanism has been
proposed to illustrate the microscopic and macroscopic
structural evolutions of here reported high-silica ZSM-5 HSZs
during DGC synthesis.
2θ range of 22.5-25 degrees were compared with that of commercial
[16a]
ZSM-5(200) zeolite for obtaining the relative crystallinity (RC).
N2
adsorption-desorption experiments were performed on a Micromeritics
Tristar 3000 porosimeter at 77 K. The Brunauer-Emmett-Teller (BET)
method was used to calculate the specific surface area (SBET) and the
adsorbed nitrogen volume at about P/P0 of 0.990 was used to determine
the total volume (Vtotal). In addition, the t-plot method was used to
calculate the micropore surface area (Smicro) and the micropore volume
(Vmicro). The external surface area (Sext) and mesopore volume (Vmeso
)
were obtained by the total data minus the corresponding micropore data.
The field-emission scanning electron microscopy (FE-SEM) images were
obtained on a HITACHI SU8220 and FEI-Magellan 400L under an
operating voltage of 1 kV. In order to observe the interior of zeolite
particles, the synthesized materials and graphite were mixed and then
processed with argon ions on an E-3500 ion milling system to conduct
the cross-section polish. Transmission electron microscopy (TEM)
images were obtained on a JEM-2100F electron microscope. The
aluminum content of samples were determined on the Agilent
Technologies 725 inductively coupled plasma optical emission
spectrometry (ICP-OES). The solid-state 27Al Magic Angle Spinning
Nuclear Magnetic Resonance (MAS NMR) spectra were recorded on a
Varian VNMRS 400WB spectrometer. The ammonia temperature-
programmed-desorption (NH3-TPD) of samples were analyzed on a
Micromeritics AutoChem II 2920 instrument equipped with a thermal
conductivity detector (TCD). The materials (ca. 200 mg) were pretreated
in an He flow (30 mL min-1) at 600 °C for 2 h at a heating rate of 10 °C
min-1 to remove adsorbed impurities, then cooled down to 100 °C, and
saturated adsorption with NH3 for 1 h. Then, the He flow (30 mL min-1)
was used to remove the physical adsorbed ammonia at 100 °C for 1 h.
Subsequently, the NH3-TPD profiles were recorded from 100 °C to
500 °C at a heating rate of 10 °C min-1. Fourier transform infrared spectra
of adsorbed pyridine (Py-FTIR) were recorded on a Perkin-Elmer Frontier
FTIR instrument. The materials were ground and pressed into self-
supporting wafers, which were activated at 500 °C for 2 h in vacuum and
then cooled down to room temperature. Subsequently, the spectra of
zeolite frameworks were recorded. Next, the materials were saturated
with pyridine vapor for 0.5 h and then evacuated at 200 °C for 0.5 h. After
cooling to room temperature, the spectra were recorded in 1350-1750
cm-1 range. According to the previous literature, the extinction coefficients
used for quantification are 1.67 and 2.22, respectively. Assuming that an
acid site can adsorb a pyridine molecule, the concentrations of Brønsted
acid sites (BAS) and Lewis acid sites (LAS) can be calculated by Eq. (1)
and (2), respectively,
Experimental Section
Reagents
Tetraethyl orthosilicate (TEOS) and methanol ( ≥ 99.5 wt%) were
purchased from Shanghai Lingfeng Chemical Co., Ltd (China). Aluminum
isopropoxide (Al(iPrO)3) was obtained from Aladdin Reagent Co., Ltd
(China). Tetrapropylammonium hydroxide (TPAOH, 25 wt%) was
purchased from Yixing Dahua Chemical Co., Ltd (China). Ammonium
chloride (NH4Cl) was obtained from Sinopharm Chemical Reagent Co.,
Ltd (China). All reactants were used as received without further
purification.
Materials preparation
High-silica ZSM-5 HSZs with Si/Al ratio of 200 were prepared
[11]
according to the previous reports.
In a typical process, 10.42 g of
TEOS and 0.051 g of Al(iPrO)3 were mixed at room temperature for 0.5 h.
Then, 18.00 g of deionized water was added and stirring was continued
for another 0.5 h. Subsequently, 4.067 g of TPAOH (25 wt% aqueous
solution) was added dropwise into the mixture. The molar ratio of the
resultant sol was 1.0 SiO2: 0.0025 Al2O3: 0.1 TPAOH: 23.38 H2O. The
mixture was stirred at 40 °C in water bath to get the transparent
precursor gel which was dried at the same temperature for the next 48 h.
The aged precursor gel was crushed and then transferred into an Al2O3
crucible and put into an 80 mL Teflon container. 0.7 g of deionized water
was added into the bottom of the Teflon container avoiding contacting
(1)
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
(2)
14770–14771; e) M. Bjørgen, S. Svelle, F. Joensen, J. Nerlov, S.
Kolboe, F. Bonino, L. Palumbo, S. Bordiga, U. Olsbye, J. Catal. 2007,
249, 195–207.
where IA(B) and IA(L) correspond to the integrated absorbance of BAS
and LAS band (cm-1), respectively, R corresponds to the radius of
catalyst disk (cm) and W corresponds to the weight of disk (mg).
Thermogravimetric analysis (TGA) of used catalysts were carried out on
a Netzsch STA 494 C Jupiter TG/DSC instrument. The weight loss of
deactivated catalysts between 300 °C and 800 °C were taken as the total
coke content. Correspondingly, the catalyst average coke formation rate
was calculated by dividing the total coke content by the catalyst lifetime
(t90).
[3]
[4]
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, Z. Gao, J. Catal. 2008, 258, 243–249; b) C. D.
Chang, C. T. Chu, R. F. Socha, J. Catal. 1984, 86, 289–296; c) Z. J. Hu,
H. B. Zhang, L. Wang, H. X. Zhang, Y. H. Zhang, H. L. Xu, W. Shen, Y.
Tang, Catal. Sci. Technol. 2014, 4, 2891–2895.
[24]
.a) J. Kim, M. Choi, R. Ryoo, J. Catal. 2010, 269, 219–228; b) Q. Zhang,
S. Hu, L. L. Zhang, Z. J. Wu, Y. J. Gong, T. Dou, Green Chem. 2014,
16, 77–81; c) L. Q. Meng, B. Mezari, M. G. Goesten, E. J. M. Hensen,
Chem. Mater. 2017, 29, 4091–4096; d) J. Ding, P. J. Chen, S. Y. Fan, Z.
Q. Zhang, L. P. Han, G. F. Zhao, Y. Liu, Y. Lu, ACS Sustainable Chem.
Eng. 2017, 5, 1840–1853; e) T. L. Cui, L. B. Lv, W. B. Zhang, X. H. Li, J.
S. Chen, Catal. Sci. Technol. 2016, 6, 5262–5266.
Catalytic tests
The MTP reactions were performed in a quartz tubular fixed-bed
reactor (i.d., 8 mm) at atmospheric pressure and a K-type thermocouple
was placed near the catalyst bed for the detection and control of the
reaction temperature. Prior to reaction, 0.2 g of sieved catalyst particles
(40-60 mesh) were loaded between two quartz wool plugs and activated
at 550 °C in the nitrogen flow of 50 ml min-1 for 2 h. Then, the catalyst
bed temperature was decreased to 460 °C for MTP reaction. A high
performance liquid chromatography (HPLC) pump was used to feed
methanol into the reactor system with the weight hourly space velocity
(WHSV) of 1.0 g g-1 h-1 and the nitrogen flow was maintained at 50 ml
min-1. The product effluent was analyzed by an online gas
chromatograph of GC/2010 plus (Shimadzu, HP-PLOT/Q capillary
column) with a flame ionization detector (FID). The transfer line between
the reactor and the gas chromatograph was maintained at 250 °C to
avoid the possible condensation of organic moieties. Dimethyl ether
(DME) was treated as an unconverted reactant, so the methanol
[5]
[6]
a) J. S. Martínez-Espín, K. D. Wispelaere, T. V. W. Janssens, S. Svelle,
K. P. Lillerud, P. Beato, V. V. Speybroeck, U. Olsbye, ACS Catal. 2017,
7, 5773–5780; b) S. Müller, Y. Liu, F. M. Kirchberger, M. Tonigold, M.
SanchezSanchez, J. A. Lercher, J. Am. Chem. Soc. 2016, 138, 15994–
16003.
.I. Yarulina, S. Bailleul, A. Pustovarenko, J. R. Martinez, K. D.
Wispelaere, J. Hajek, B. M. Weckhuysen, K. Houben, M. Baldus, V. V.
Speybroeck, F. Kapteijn, J. Gascon, ChemCatChem 2016, 8, 3057–
3063.
[7]
[8]
D. L. Cai, Y. H. Ma, Y. L. Hou, Y. Cui, Z. Jia, C. X. Zhang, Y. Wang, F.
Wei, Catal. Sci. Technol. 2017, 7, 2440–2444.
a) M. Milina, S. Mitchell, P. Crivelli, D. Cooke, J. Pꢀrez-Ramírez, Nat.
Commun. 2014, 5, 3922–3931; b) J. C. Groen, W. D. Zhu, S. Brouwer,
S. J. Huynink, F. Kapteijn, J. A. Moulijn, J. Pꢀrez-Ramírez, J. Am.
Chem. Soc. 2007, 129, 355–360; c) D. Verboekend, J. Pꢀrez-Ramírez,
Chem. Eur. J. 2011, 17, 1137–1147.
conversion (XMeOH
)
and product selectivity (SCxHy
)
were calculated
[9]
a) C. J. H. Jacobsen, C. Madsen, J. Houzvicka, I. Schmidt, A. Carlsson,
J. Am. Chem. Soc. 2000, 122, 7116–7117; b) Y. S. Tao, H. Kanoh, K.
Kaneko, J. Am. Chem. Soc. 2003, 125, 6044–6045; c) M. Choi, H. S.
Cho, R. Srivastava, C. Venkatesan, D. H. Choi, R. Ryoo, Nat. Mater.
2006, 5, 718–723.
according to Eq. (3) and (4), respectively,
(3)
[10] a) M. E. Davis, Chem. Mater. 2013, 26, 239–245; b) X. Meng, F. S.
Xiao, Chem. Rev. 2013, 114, 1521–1543.
(4)
[11] a) T. G. Ge, Z. L. Hua, X. Y. He, J. Lv, H. R. Chen, L. X. Zhang, H. L.
Yao, Z. W. Liu, C. C. Lin, J. L. Shi, Chem. Eur. J. 2016, 22, 7895–7905;
b) X. Y. He, T. G. Ge, Z. L. Hua, J. Zhou, J. Lv, J. L. Zhou, Z. C. Liu, J.
L. Shi, ACS Appl. Mater. Interfaces 2016, 8, 7118–7124.
where N is the number of moles and x is the number of carbon atoms,
superscript i and o refer to the components at the inlet and outlet of
reactor, respectively.
[12] T. Y. Liang, J. L. Chen, Z. F. Qin, J. F. Li, P. F. Wang, S. Wang, G. F.
Wang, M. Dong, W. B. Fan, J. G. Wang, ACS Catal. 2016, 6, 7311–
7325.
[13] a) C. S. Zhang, Q. M. Wu, C. Lei, S. X. Pan, C. Q. Bian, L. Wang, X. J.
Meng, F. S. Xiao, Ind. Eng. Chem. Res. 2017, 56, 1450–1460; b) C.
Sun, J. M. Du, J. Liu, Y. S. Yang, N. Ren, W. Shen, H. L. Xu, Y. Tang,
Chem. Commun. 2010, 46, 2671–2673; c) J. Ahmadpour, M.
Taghizadeh, J. Nat. Gas. Sci. Eng. 2015, 23, 184–194; d) B. Li, Z. J. Hu,
B. Kong, J. X. Wang, W. Li, Z. K. Sun, X. F. Qian, Y. S. Yang, W. Shen,
H. L. Xu, D. Y. Zhao, Chem. Sci. 2014, 5, 1565–1573.
Acknowledgements
This work was supported by National Natural Science
Foundation of China (U1510107, 21776297, 21403303) and
Shanghai Rising-Star Program (18QB1404500).
[14] a) S. Svelle, U. Olsbye, F. Joensen, M. Bjørgen, J. Phys. Chem. C
2007, 111, 17981–17984; b) M. Rostamizadeh, F. Yaripour, Fuel 2016,
181, 537–546.
Keywords: Zeolites • Mesoporous materials • Microporous
materials • Acidity • Propylene selectivity
[15] M. Milina, S. Mitchell, D. Cooke, P. Crivelli, J. Pérez-Ramírez, Angew.
Chem., Int. Ed. 2015, 54, 1591–1594.
[1]
a) C. J. Pereira, Science 1999, 285, 670–671; b) Y. Traa, Chem.
Commun. 2010, 46, 2175–2187; c) H. M. T. Galvis, K. P. de Jong, ACS
Catal. 2013, 3, 2130–2149; d) U. Olsbye, S. Svelle, K. P. Lillerud, Z. H.
Wei, Y. Y. Chen, J. F. Li, J. G. Wang, W. B. Fan, Chem. Soc. Rev.
2015, 44, 7155–7176.
[16] a) J. Ding, M. Wang, L. M. Peng, N. H. Xue, Y. M. Wang, M. Y. He,
Appl. Catal., A 2015, 503, 147–155; b) H. B. Zhang, Z. J. Hu, L. Huang,
H. X. Zhang, K. S. Song, L. Wang, Z. P. Shi, J. X. Ma, Y. Zhuang, W.
Shen, Y. H. Zhang, H. L. Xu, Y. Tang, ACS Catal. 2015, 5, 2548–2558.
[17] C. Y. Dai, A. F. Zhang, M. Liu, L. Gu, X. W. Guo, C. S. Song, ACS
Nano 2016, 10, 7401–7408.
[2]
a) I. M. Dahl, S. Kolboe, Catal. Lett. 1993, 20, 329–336; b) I. M. Dahl, S.
Kolboe, J. Catal. 1994, 149, 458–464; c) I. M. Dahl, S. Kolboe, J. Catal.
1996, 161, 304–309; d) S. Svelle, F. Joensen, J. Nerlov, U. Olsbye, K.-
P. Lillerud, S. Kolboe, M. Bjørgen, J. Am. Chem. Soc. 2006, 128,
[18] a) S. L. Zhang, Y. J. Gong, L. L. Zhang, Y. S. Liu, T. Dou, J. Xu, F.
Deng, Fuel Process. Technol. 2015, 129, 130–138; b) S. M. T. Almutairi,
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
B. Mezari, E. A. Pidko, P. C. M. M. Magusin, E. J. M. Hensen, J. Catal.
2013, 307, 194–203; c) W. L. Dai, G. Cao, L. Yang, G. J. Wu, M.
Dyballa, M. Hunger, N. J. Guan, L. D. Li, Catal. Sci. Technol. 2017, 7,
607–618; d) Y. Kim, J. C. Kim, C. Jo, T. W. Kim, C. U. Kim, S. Y. Jeong,
H. J. Chae, Micro. Meso. Mater. 2016, 222, 1–8.
Martínez-Espín, M. Morten, S. Mitchell, J. Pꢀrez-Ramírez, U. Olsbye,
B.M. Weckhuysen, V. Van Speybroeck, F. Kapteijn, J. Gascon, Nature
Chem. 2018, 10, 804-812.
[21] T. G. Ge, Z. L. Hua, J. Lv, J. L. Zhou, H. L. Guo, J. Zhou, J. L. Shi,
CrystEngComm 2017, 19, 1370–1376.
[19] a) S. Inagaki, K. Sato, S. Hayashi, J. Tatami, Y. Kubota, T. Wakihara,
ACS Appl. Mater. Interfaces 2015, 7, 4488–4493; b) P. Losch, M. Boltz,
C. Bernardon, B. Louis, A. Palčić, V. Valtchev, Appl. Catal., A 2016,
509, 30–37.
[22] D. Verboekend, S. Mitchell, M. Milina, J. C. Groen, J. Pꢀrez-Ramírez, J.
Phys. Chem. C 2011, 115, 14193–14203.
[23] T. G. Ge, Z. L. Hua, X. Y. He, Y. Zhu, W. C. Ren, L. S. Chen, L. X.
Zhang, H. R. Chen, C. C. Lin, H. L. Yao, J. L. Shi, Chin. J. Catal. 2015,
36, 866–873.
[20] I. Yarulina, K. De Wispelaere, S. Bailleul, J. Goetze, M. Radersma, E.
Abou-Hamad, I. Vollmer, M. Goesten, B. Mezari, E.J.M. Hensen, J.S.
[24] C. A. Emeis, J. Catal. 1993, 141, 347–354.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800926
European Journal of Inorganic Chemistry
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
A facile and eco-friendly
Mesoporous Materials*
mesoporogen-free steam-assisted
crystallization strategy has been
developed for the synthesis of
hierarchically structured ZSM-5
zeolites with superior MTP catalytic
performance, and a new “in situ alkali
etching-hydrothermal restoring”
mechanism is discussed.
Hangle Guo, Tongguang Ge, Jian Lv,
Changlin Du, Jian Zhou,* Zhicheng Liu,
Zile Hua*
Page No. – Page No.
Mesoporogen-free synthesis of high-
silica hierarchically structured ZSM-5
zeolites and their superior
performance for methanol-to-
propylene reaction
*one or two words that highlight the emphasis of the paper or the field of the study
Layout 2:
FULL PAPER
Key Topic*
Author(s), Corresponding Author(s)*
((Insert TOC Graphic here; max. width: 11.5 cm; max. height: 2.5 cm; NOTE: the
final letter height should not be less than 2 mm.))
Page No. – Page No.
Title
Text for Table of Contents
*one or two words that highlight the emphasis of the paper or the field of the study
This article is protected by copyright. All rights reserved.