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\begin{document}

\title{Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process
and Material Properties of Zeolite}



\author[1]{Tingting Qi}%
\author[2]{Jing Shi}%
\author[1]{Xishuo Wang}%
\author[1]{Kun Dong}%
\author[1]{Yong Luo}%
\author[2]{Jiawei  Teng}%
\author[1]{Guang-Wen Chu}%
\author[1]{Liangliang Zhang}%
\author[1]{Hai-Kui Zou}%
\author[1]{Baochang Sun}%
\affil[1]{Beijing University of Chemical Technology College of Chemical Engineering}%
\affil[2]{State Key Laboratory of Green Chemical Engineering and Industrial Catalysis, SINOPEC Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China}%


\vspace{-1em}



  
  \date{May 19, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Hierarchical (micro/mesopore) ZSM-5 zeolites were hydrothermally
synthesized with enhancing micromixing of the high viscosity reaction
system in a rotating packed bed (RPB). Herein, the effects of four
operating processes with different micromixing intensity on
nucleation/crystal growth process as well as properties of ZSM-5
zeolites were investigated. Results indicated that enhancing micromixing
by RPB in the zeolite synthesis could facilitate the formation of Al
sites and shorten the nucleation and crystallization period. ZSM-5
samples prepared by the RPB premix process exhibit hierarchical
structure, smaller average particle size, more uniform particle size
distributions, larger specific surface areas, higher catalytic stability
as well as more Br\selectlanguage{ngerman}ønsted and Lewis acid sites. While adopting the
prepared ZSM-5 zeolites with RPB premix for catalyzing C4-olefin
cracking reaction, the conversion of C4-olefin and yield of propylene
were higher than that obtained by traditional stirring tank reactor
premix.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Effects of Enhancing Micromixing onNucleation/Crystal Growth
Process and Material Properties of Zeolite}

Tingting Qi \textsuperscript{a,b}, Shi Jing \textsuperscript{c}, Xishuo
Wang \textsuperscript{a,b}, Kun Dong \textsuperscript{a,b}, Yong
Luo\textsuperscript{a}, Jiawei Teng \textsuperscript{c,}*,

Guang-Wen Chu \textsuperscript{a,b}, Liangliang Zhang
\textsuperscript{a}, Hai-Kui Zou \textsuperscript{a}, Baochang Sun
\textsuperscript{a,}*

\emph{\textsuperscript{a} Research Center of the Ministry of Education
for High Gravity Engineering and Technology,Beijing University of
Chemical Technology, Beijing 100029, PR China}

\emph{\textsuperscript{b} State Key Laboratory of Organic-Inorganic
Composites, Beijing University of Chemical Technology, Beijing, 100029,
PR China}

\emph{\textsuperscript{c} State Key Laboratory of Green Chemical
Engineering and Industrial Catalysis, SINOPEC Shanghai Research
Institute of Petrochemical Technology, Shanghai 201208, China}

* Corresponding author (Baochang Sun). E-mail: sunbc@mail.buct.edu.cn,
Tel: 010-64443134-803, Address: No 15 Bei San Huan Dong Road, Beijing,
100029, China

* Corresponding author (Jiawei Teng). E-mail: tengjw.sshy@sinopec.com,
Tel: 021-68467713, Address: No 1658 Pudong North Road, Shanghai, 201208,
China

\textbf{ABSTRACT}

Hierarchical (micro/mesopore) ZSM-5 zeolites were hydrothermally
synthesized with enhancing~micromixing of the high viscosity reaction
system~in a rotating packed bed (RPB). Herein, the effects of four
operating processes with different micromixing intensity~on
nucleation/crystal growth process as well as properties of ZSM-5
zeolites were investigated. Results indicated that enhancing
micromixing~by RPB in the zeolite synthesis could facilitate the
formation of Al sites and shorten the nucleation and crystallization
period. ZSM-5 samples prepared by the RPB premix process exhibit
hierarchical structure, smaller average particle size, more uniform
particle size distributions, larger specific surface areas, higher
catalytic stability as well as more Br\selectlanguage{ngerman}ønsted and Lewis acid sites. While
adopting the prepared ZSM-5 zeolites with RPB premix for catalyzing
C4-olefin cracking reaction, the conversion of C4-olefin and yield of
propylene were higher than that obtained by traditional stirring tank
reactor premix.

\textbf{KEYWORDS:} ZSM-5 zeolites, Rotating packed bed,
Nucleation/crystal growth mechanism, Al sites, C4-olefin cracking
reaction

\textbf{1 Introduction}

ZSM-5 zeolites with excellent catalytic performance have been widely
applied in the petrochemical industry as shape-selective catalysts
{[}1-4{]}, such as methanol-to-aromatics reaction {[}5{]},
methanol-to-olefins reaction {[}6{]}, fluid catalytic cracking reaction
{[}7{]}, deep desulfurization {[}8{]} and so on. While their
morphological, textural and acidic properties often affect catalytic
performance, it remains a research focus to control the physical and
chemical properties of zeolites.

In an attempt to improve the performance of zeolites, two routes have
been proposed: (1) Tailoring acid sites in zeolites {[}9{]}. Various
approaches have been developed to improve acid sites of zeolites
including dealumiumazation {[}10,11{]}, SiO\textsubscript{2}deposition
{[}12{]}, the load of superacid {[}13{]}, and so on. Dealuminization of
zeolites prompts the aluminum species in the lattice~to migrate out with
high-temperature treatment, resulting in a transformation from framework
aluminum to extra-framework aluminum. The formation of extra-framework
aluminum is beneficial to increasing~acid~amount~of Lewis acidity, and
consequently, enhancing the synergistic effect of Brønsted and Lewis
acidity {[}11{]}. The vapor deposition of SiO\textsubscript{2} could
facilitate the formation of framework aluminum in zeolites, resulting in
an increase of the Brønsted acidity {[}12{]}. The load of superacid
enhances both Brønsted acidity and Lewis acidity of zeolites {[}13{]}.
However, the secondary high-temperature and acid treatment in the above
processes often destroyed the pore structure and hydrothermal stability
of zeolites {[}14{]}. (2) Decreasing particle sizes and donating
mesopores or macropores to zeolites by adding templates in the reaction
system or enhancing micromixing during the hydrothermal synthesis
process {[}15{]}. Kim et al. {[}16{]} have prepared nanosized ZSM-5
zeolites with particle sizes in the range of 12-100 nm via
confined-space synthesis using colloid-imprinted carbons as templates.
Narayanan et al. {[}17{]} have synthesized microporous ZSM-5 zeolites
with an average size of 340 nm by using nonionic surfactants (Triton
X-100), and Dong et al. {[}18{]} have prepared large macropores (average
pore-diameter: 1.5 \selectlanguage{greek}μ\selectlanguage{english}m) zeolite monoliths by the transformation of
mesoporous silica spheres. On the other hand, enhancing micromixing in
the nucleation/crystal growth period was reported to be a useful method
for the fast synthesis of hierarchical zeolites {[}19{]}. During the
nucleation process of zeolites, the uniformity of various reaction
species affects the assembly of structural units, resulting in the
differences of the size, amount, and composition of the crystal nucleus.
According to the Ostwald ripening growth mechanism, a large crystal
nucleus will grow up based on the disappearance of the small crystal
nucleus. Thus, the morphological, textural, and acidic properties of the
final crystal are closely related to the uniformity of the initial
crystal nucleus.

In the traditional stirring tank reactor (STR), it's difficult to obtain
a homogeneous nucleation environment and uniformity of initial crystal
nucleus {[}20{]}, particularly in high viscosities and large
solution-volume systems {[}21, 22{]}. A rotating packed bed (RPB) as an
efficient process intensification device can provide a high-gravity
environment with considerable shear force, leading to the excellent
micromixing effect {[}23-26{]}. During the ZSM-5 synthesis process, RPB
can create reaction precursors with uniform concentration and
supersaturation, resulting in uniform nucleation and consequently the
acceleration of crystallization of zeolites {[}19{]}. Also, enhancing
micromixing to improve acid strength and acid quantity by controlling Al
contents during the nucleation/growth process of zeolite has not been
extensively studied {[}27{]}.

In this study, four operating processes, including RPB premix - dynamic
crystallization, RPB premix - static crystallization, STR premix -
dynamic crystallization, and STR premix - static crystallization, were
carried out to investigate the effects of enhancing micromixing in the
zeolite synthetic pathway on nucleation/crystal growth process and
material properties of ZSM-5 zeolites. The nucleation/crystal growth
mechanism of ZSM-5 zeolites was studied based on experimental data
characterized~by Fourier transform infrared (FTIR) spectrophotometry and
powder X-ray diffraction (XRD). And the catalytic cracking reaction of
C4 olefins was adopted for evaluating the catalytic performance of the
prepared ZSM-5 zeolites obtained by different operating processes.

\section*{2 Materials and methods}

{\label{materials-and-methods}}

\subsection*{2.1 Chemicals}

{\label{chemicals}}

Aluminum sulfate octadecahydrate
(Al\textsubscript{2}(SO\textsubscript{4})\textsubscript{3}.18H\textsubscript{2}O),
silica sol (40 wt\% aqueous solution) and sodium chloride (NaCl) were
purchased from Aladdin Co., Ltd. Tetrapropylammonium hydroxide (TPAOH,
25 wt\% aqueous solution) was purchased from Innochem Co., Ltd.
C4-olefin was provided from Shanghai Petrochemical Company.

\subsection*{2.2 Catalyst preparation}

{\label{catalyst-preparation}}

Four operating processes for the synthesis of ZSM-5 zeolites, including
RPB premix - static crystallization, RPB premix - dynamic
crystallization, STR premix - static crystallization, and STR premix -
dynamic crystallization, are schematically showed in Fig. 1.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Fig. 1.} Schematic diagram of four operating processes for
synthesizing ZSM-5 zeolites: a) RPB premix - static crystallization, b)
RPB premix - dynamic crystallization, c) STR premix - static
crystallization and d) STR premix - dynamic crystallization

To start a synthesis, a certain amount of chemicals (silica sol (40 wt\%
aqueous solution),
Al\textsubscript{2}(SO\textsubscript{4})\textsubscript{3}.18H\textsubscript{2}O,
TPAOH (25 wt\% aqueous solution), NaCl, H\textsubscript{2}O) were
measured following a molar ratio of 200SiO\textsubscript{2}:
Al\textsubscript{2}O\textsubscript{3}: 80TPAOH: 30NaCl:
4500H\textsubscript{2}O. Two sources, including (A) silica source
prepared by silica sol, and (B) aluminum source prepared by
Al\textsubscript{2}(SO\textsubscript{4})\textsubscript{3}.18H\textsubscript{2}O,
NaCl, water and TPAOH, were prepared respectively at room temperature
under vigorous stirring for 0.5 h to obtain a homogeneous solution. In
an RPB premixing process, the above two sources were pumped into RPB via
two flow meters, respectively. And then the initial gel was cycled by a
peristaltic pump for 30 min, operating with a circulation rate of 540
mL\selectlanguage{ngerman}·min\textsuperscript{-1} and a rotation speed of 1000 rpm. While in an
STR premixing process, the silica source was slowly added dropwise into
the aluminum source at a rotation speed of 1000 rpm for 1 h. The
as-obtained gel was then poured into 100 mL Teflon-lined autoclave for
traditional static crystallization and 500 mL STR for dynamic
crystallization, respectively. In the hydrothermal crystallization
process, static crystallization was carried out at 130 \selectlanguage{english} for 24 h, and
dynamic crystallization was at 130 \selectlanguage{english} for 16 h with a stirring speed of
1000 rpm in the STR. After these processes, as-obtained samples were
washed with deionized water and centrifuged at 6000 rpm for 5 min with
repeating four times, followed by drying at 110 degC for 12 h and
calcining at 550 degC for 3.5 h to remove the template. Finally, samples
were converted to proton form by refluxing twice in 1.0 M
NH\textsubscript{4}NO\textsubscript{3} (5.0 g solid per 200 mL solution)
for 4 h, followed by drying at 110 degC for 12 h and calcining at 550 degC
for 3.5 h. The resulting samples are denoted as ZSM-5 samples.

\subsection*{2.3 Nucleation/crystal growth mechanism of zeolite ZSM-5
studies}

{\label{nucleationcrystal-growth-mechanism-of-zeolite-zsm-5-studies}}

During the premix and crystallization processes, small aliquots of the
reaction solution were taken in different time for analysis to explore
the effects of enhancing micromixing on the nucleation/crystal growth
process of ZSM-5 zeolites. The aliquot was washed with deionized water
and centrifuged at 6000 rpm for 5 min until the pH was below 9, followed
by drying at room temperature. After drying, the aliquots were analyzed
by FTIR and XRD to study the nucleation/crystal growth mechanism of
ZSM-5 zeolites. These measurements were repeated three times.

\subsection*{2.4 Characterization}

{\label{characterization}}

XRD patterns of the ZSM-5 zeolites and its reaction intermediates were
recorded on an XRD-6000 diffractometer (Shimadzu Inc.) using Cu\emph{K}
a radiation (40 kV, 40 mA), in the 2\selectlanguage{greek}\emph{θ} \selectlanguage{english}range from 5\selectlanguage{ngerman}° to 90°, with
a step size of 0.02° and a counting time of 10 s per step. The elemental
composition (Si/Al ratio) of the sample was determined by XRF
spectrometer (Rigaku). Morphology and particle size of ZSM-5 zeolites
were observed by scanning electron microscopy (SEM, Tescan). FTIR
spectroscopic analyses were carried out with pressing potassium bromide
troche (in a mass ratio of 1/100) on a Nicolet 6700 spectrometer
(Nicolet Instrument Co., USA) in the wavenumber range of
4000--400\selectlanguage{english} cm\selectlanguage{english}\textsuperscript{-1}. The textural properties of the sample
were characterized on a Quantachrome surface area analyzer. The pore
size distributions were calculated by Barrett-Joyner-Halenda method from
the desorption branch of the isotherm. The surface elemental composition
(Si/Al ratio) was tested using X-ray photoelectron spectroscopy (XPS;
Kratos AXIS SUPRA, Shimadzu) equipped with an Al \emph{K} \selectlanguage{greek}α \selectlanguage{english}excitation
source. NH\textsubscript{3} temperature-programmed desorption (TPD)
experiments were conducted on a chemisorption AutoChem II 2920 analyzer
with a thermal conductivity detector (TCD) for analyzing surface acid
properties. 100 mg of the sample was pretreated under Helium at 550\selectlanguage{ngerman}°C
for 1 h and then saturated with a flow mixed with 10\% ammonia and 90\%
He at 100 °C for 80 min. Afterward, the sample was kept in He flow for
30 min to remove physically adsorbed ammonia, followed by heating to 600
°C at a rate of 10 °C /min in He (30 mL/min). The amount of Brønsted and
Lewis acid of the sample was measured by Pyridine-adsorbed FT-IR spectra
using Nicolet Model 710 instrument. The sample was treated under vacuum
at 350 °C for 1 h and then cooled to 150 °C. After that, the sample was
maintained in the pyridine vapor at 150 °C for 2 h. Before analysis by
FTIR, the test system was evacuated for another 1 h to remove physically
adsorbed pyridine. The FT-IR spectra of the saturated sample were
recorded from 40 to 350 °C under vacuum for 1 h, respectively.

\subsection*{2.5 Catalytic test}

{\label{catalytic-test}}

The catalyzing C4-olefin cracking reaction was carried out to test the
catalytic activities of ZSM-5 samples in a stainless catalytic reactor.
C4-olefin was used as the reactant without further purification. The
cracking of the C4-olefin test was carried out in a continuous flow
fixed-bed system with a stainless steel tubular reactor (\selectlanguage{greek}Φ\selectlanguage{english}10 mm \selectlanguage{ngerman}× 530
mm) equipped with a laboratory-scale piston pump for C4-olefin input.
The reaction was conducted at 823 K under a total pressure of 0.1 MPa.
Before the experiments, the catalyst was in situ heated at a ramp rate
of 5 K min\selectlanguage{english}\textsuperscript{-1} to the reaction temperature in
N\textsubscript{2} flow (100 ml min\selectlanguage{english}\textsuperscript{-1}) and maintained
at this temperature for 2 h. The output products were analyzed online on
an HP 6890 gas chromatograph equipped with a flame ionization detector
(FID).

\section*{3. Results and discussion}

{\label{results-and-discussion}}

\subsection*{3.1 Nucleation/crystal growth mechanism of ZSM-5
zeolites}

{\label{nucleationcrystal-growth-mechanism-of-zsm-5-zeolites}}

The nucleation/crystal growth mechanism is significant for the
controllable synthesis of ZSM-5 zeolites. The characterization methods
with high sensitivity to the amorphous matrix and crystalline species
are necessary for the mechanism study {[}28{]}. FTIR spectroscopy is
often employed to observe the short-range order structures of crystals,
and IR vibrations of the structural units of zeolites are intense in the
nucleation process {[}29{]}. XRD analysis is usually used to study the
long-range order structures of crystals, which is beneficial to studying
the growth process of zeolites {[}30{]}. Fig. 2 displays the FTIR
spectra of solid aliquots drawn off the reaction mixture at t = 0.5 h
(after RPB premix) and t = 1.5-8.5 h (under dynamic crystallization at
130 \selectlanguage{english}).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Fig. 2.} FTIR spectra of the solid aliquots from a series of
experiments at different intervals.

The aliquots prepared for 0.5-8.5 h show broad absorption bands in the
range of 400-1200 cm\textsuperscript{-1}, which are associated with
amorphous sodium aluminosilicate gels {[}31{]}. Structure sensitive
vibrations of aliquots with obvious change occurs near 530-560 and 710
cm\textsuperscript{-1}. The band at 530-560 cm\textsuperscript{-1} is
indicative for D5 ring units, which is typical of dominating secondary
structural units in the MFI-type structure {[}29,32,33{]}. This weak
broad band appears after the 0.5 h RPB premix process. After 1.5 h
dynamic hydrothermal treatment, this band becomes sharper with the
crystallization time prolonged, indicating the occurrence of the zeolite
nucleus {[}31, 34{]}. Moreover, the gradual redshift of this peak
position indicates that the SiO\textsubscript{4} tetrahedra in the D5
ring unit are substituted continuously by AlO\textsubscript{4}tetrahedra
{[}35,36{]}, which leads to the formation of Si-OH-Al, corresponding to
Br\selectlanguage{ngerman}ønsted acid sites {[}37{]}. The band at 710 cm\textsuperscript{-1} is
indicative for T-OH bending vibrations (T = Si/Al), which represents the
occurrence of hydrolysis reaction between Si\textsuperscript{4+} and
Al\textsuperscript{3+} {[}28{]} and the formation of TO\textsubscript{4}
tetrahedral assembled into zeolite skeleton {[}38{]}. This band has
occurred at 0.5 h, indicating the hydrolysis reaction has taken place in
the RPB premix process at room temperature. The gradual disappearance of
the 710 cm\textsuperscript{-1}peak is consistent with an increase in the
intensity of the 530-560 cm\textsuperscript{-1} band, suggesting that
the amount of framework atoms connected by oxygen bridges increases
constantly. This indicates the amorphous gels have transformed gradually
into zeolite crystals {[}39{]}.

\textbf{Fig. 3.} XRD patterns of solid aliquots obtained by (A) RPB and
(B) STR premix at different intervals.

Fig. 3A shows the XRD patterns of solid aliquots obtained by 30 min RPB
premix and dynamic crystallization at different intervals. X-ray
detection limit has no impact on the analysis result {[}28-30{]}. The
first crystalline phase with the crystallinity of 30\% was detected at
5.5 h, and the crystallinity is 50\% after 6.5 h, indicating that the
crystallization of the amorphous gel into long-range order zeolite
skeleton has occurred at 5.5 h of hydrothermal treatment.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

\textbf{Fig. 4.} FTIR spectra of the solid aliquots obtained by (A) RPB
and (B) STR premix at different intervals.

To investigate the effect of enhancing micromixing in the zeolite
synthetic pathway on the nucleation/crystal growth process, the gel was
pretreated by STR for 30 min as a comparison. As shown in Fig. 4, the D5
ring and T-OH structural units' band pretreated by RPB usually occurred
earlier than those by STR. This indicates the enhancement of micromixing
during the premix process accelerated the nucleation process of
zeolites. XRD results (Fig. 3) further confirm that the crystallization
process has been speeded up via RPB premix, accompanied by the growth of
the nucleus {[}29{]}. The reason is that the water phase (aluminum
source), containing a large amount of OH\textsuperscript{-} and
TPA\textsuperscript{+}, was mixed thoroughly with the gel phase (silica
source) by intensifying micromixing. The water phase provides a high pH
environment for the hydrolysis of aluminosilicate and abundant
structure-directing agents (TPA\textsuperscript{+}) for assembly of
structural units {[}40,41{]}. The better micromixing of two phases in
the RPB facilitates the faster polycondensation of structural units,
resulting in the acceleration of nucleation and crystal growth of
zeolites.

\subsection*{3.2 Characterization of the ZSM-5
samples}

{\label{characterization-of-the-zsm-5-samples}}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

\textbf{Fig. 5.} XRD patterns of four ZSM-5 samples obtained by
different operating processes.

Fig. 5 presents XRD patterns of ZSM-5 samples obtained by RPB premix -
static crystallization (ZSM-5-RS), RPB premix - dynamic crystallization
(ZSM-5-RD), STR premix - static crystallization (ZSM-5-SS) and STR
premix - dynamic crystallization (ZSM-5-SD). All the obtained samples
are assigned to highly crystallized ZSM-5 corresponding to the typical
MFI topology. Independently of micromixing intensity, the crystal form
and growth face of ZSM-5 samples have no obvious differences in the four
operating routes mentioned above, indicating the crystal form and growth
face main determined by reaction temperature rather than micromixing
effect.

The morphological properties of four ZSM-5 samples are shown in Fig. 6.
All ZSM-5 samples exhibited spherical morphologies but the particle size
distributions were not consistent. The ZSM-5 samples pretreated by RPB
premix displayed narrower particle size distributions and smaller
average particle sizes compared with those by STR premix, indicating
that the uniform distribution of structural units and
TPA\textsuperscript{+} could facilitate the increase of nucleation
sites. The number of structural units and TPA\textsuperscript{+} are
certain in the whole reaction system, the more crystal nucleus assembled
by structural units, the fewer remaining structural units for crystal
growth, resulting in the decrease of final particle sizes. Moreover,
under the same premixing process, dynamic crystallization results in
narrower particle size distributions of ZSM-5 samples with less
crystallization time because of the uniform growth of zeolites in a
relatively homogeneous crystallization environment. ZSM-5-RD showed the
narrowest size distribution ranging from 160 to 400 nm with an average
size of 290 nm.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image7/image7}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image8/image8}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image9/image9}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image10/image10}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image11/image11}

\end{center}
\end{figure}

\textbf{Fig. 6.} SEM images and particle size distributions of (a)
ZSM-5-RD, (b) ZSM-5-RS, (c) ZSM-5-SD, (d) ZSM-5-SS.

The textural properties of four ZSM-5 samples are summarized in Table 1.
The N\textsubscript{2} adsorption-desorption isotherms of ZSM-5 samples
obtained via RPB premix differ from those by STR (Fig. 7). Besides the
steep uptake below \emph{P/P} \textsubscript{0} = 0.02 in the isotherms
of all samples (indicating uniform microporous in ZSM-5 zeolites), there
is an H4 hysteresis loop of the ZSM-5 samples obtained via RPB premix
when \emph{P/P} \textsubscript{0} is 0.45, which indicates the presence
of slit-shaped mesoporous structures {[}42{]}. The textural properties
in Table 1 reveal that the surface areas and pore volumes of ZSM-5
samples obtained via RPB premix are higher than those via STR premix.
And the mesoporous characters are generated accompanied by the decrease
of microporous structures {[}43{]}.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image12/image12}

\end{center}
\end{figure}

\textbf{Fig. 7} N\textsubscript{2} adsorption and desorption isotherms
of four ZSM-5 samples obtained by different operating processes.

\textbf{Table 1.} Textural properties of four ZSM-5 samples obtained by
different operating processes.\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
sample & \emph{S}\textsubscript{BET}/m\textsuperscript{2}
g\textsuperscript{-1} & \emph{V}\textsubscript{t}/cm\textsuperscript{3}
g\textsuperscript{-1} &
\emph{V}\textsubscript{mic}/cm\textsuperscript{3}
g\textsuperscript{-1}\tabularnewline
\midrule
\endhead
ZSM-5-RD & 520.9 & 0.26 & 0.13\tabularnewline
ZSM-5-RS & 517.3 & 0.25 & 0.15\tabularnewline
ZSM-5-SD & 463.3 & 0.23 & 0.21\tabularnewline
ZSM-5-SS & 461.2 & 0.23 & 0.22\tabularnewline
\bottomrule
\end{longtable}

Fig. 8 shows the pore size distribution curves calculated by
Barrett-Joyner-Halenda (BJH) method. The hierarchical structure of the
ZSM-5 samples obtained via RPB premix can be observed. Furthermore, the
average pore size of ZSM5-RD is larger than that of ZSM5-RS, and an
increase of cumulative pore volume in the diameter range of 4.5-8.0 nm
is presented for the former sample. In contrast, ZSM5-SS and ZSM5-SD
exhibit fewer mesopores than ZSM5-RS and ZSM5-RD, indicating that the
textural properties of ZSM-5 samples are greatly affected by the
micromixing intensity in the nucleation process.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image13/image13}

\end{center}
\end{figure}

\textbf{Fig. 8.} BJH pore size distributions of four ZSM-5 samples
obtained by different operating processes.

Surface- and bulk- chemical compositions of ZSM-5 were measured by XPS
and XRF respectively, which are displayed in Table 2. Both on surfaces
and in bulk phases, the Si/Al ratios of ZSM-5 samples obtained via RPB
premix are much lower than those via STR premix, which indicates that
the concentration of Al sites is correlated with the micromixing
intensity in the zeolite nucleation period. The significant increase in
the Al content of ZSM-RS/RD indicates that enhancing micromixing by RPB
premix plays a quite important role in the formation of Al sites in the
zeolite in the growth process. Besides, the Al contents on surfaces of
ZSM-5 samples are higher than those in bulk phases, which is correspond
with the zeolite SAPO-34 reported by Xing et al. {[}44{]}. Moreover,
with the same premixing process, the products prepared by dynamic
crystallization could impel more Al into the bulk of zeolite ZSM-5
compared with those obtained by static crystallization, which indicates
that intensifying micromixing by dynamic crystallization improves the
driving force of substitution reaction of Al.

\textbf{Table 2.} Chemical composition of ZSM-5 samples analyzed by XRF
and XPS.\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
Sample & (Si/Al)\textsubscript{gel} & (Si/Al)\textsubscript{XRF} &
(Si/Al)\textsubscript{XPS}\tabularnewline
\midrule
\endhead
ZSM-5-RS & 200 & 142 & 138\tabularnewline
ZSM-5-RD & 200 & 138 & 134\tabularnewline
ZSM-5-SS & 200 & 178 & 167\tabularnewline
ZSM-5-SD & 200 & 167 & 164\tabularnewline
\bottomrule
\end{longtable}

The ZSM-5 samples prepared by different synthesis routes have different
acid properties. The surface acid properties of four ZSM-5 samples were
investigated by NH\textsubscript{3}-TPD and pyridine FT-IR experiments.
As shown in Fig. 9, all ZSM-5 samples have two
NH\textsubscript{3}desorption peaks at 186-189  and 387-405 , which
correspond to weak acid sites and strong surface acid sites,
respectively {[}44{]}. The acid amount and acid strength of samples are
reflected by peak area and peak position of the TPD profile,
respectively {[}45{]}. As shown in Table 3, acid amount and strong
surface acid strength of ZSM5-RS and ZSM5-RD increase significantly
compared with ZSM5-SS and ZSM5-SD. Moreover, the desorption temperature
of ammonia from the strong acid sites shifted to higher temperatures as
inducing RPB in the premix process, which indicates the increase of Al
content in extra-framework positions {[}34{]}. In comparison with
ZSM5-SS, the acid amount and acid strength of ZSM5-SD have a slight
growth. A possible reason is that the enhancement of micromixing in the
STR affects the acid properties of zeolites in the crystallization
process.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image14/image14}

\end{center}
\end{figure}

\textbf{Fig. 9.} NH\textsubscript{3}-TPD profiles of four ZSM-5 samples
obtained by different operating processes.

\textbf{Table 3.} Quantification of acid sites according to
NH\textsubscript{3}-TPD profiles.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
sample & peak 1 & peak 1 & peak 2 & peak 2\tabularnewline
\midrule
\endhead
& amount\emph{\textsuperscript{a}} & temp (\selectlanguage{ngerman}°C) & amount & temp
(\selectlanguage{ngerman}°C)\tabularnewline
ZSM-5-RD & 0.33 & 190 & 0.46 & 404\tabularnewline
ZSM-5-RS & 0.33 & 187 & 0.41 & 402\tabularnewline
ZSM-5-SD & 0.31 & 185 & 0.38 & 392\tabularnewline
ZSM-5-SS & 0.28 & 185 & 0.36 & 390\tabularnewline
\bottomrule
\end{longtable}

\emph{\textsuperscript{a}}The unit of the acid amount is mmol
g\textsuperscript{-1}.

The pyridine FT-IR results are shown in Fig. 10, both Br\selectlanguage{ngerman}ønsted (B) and
Lewis (L) acid sites are present on all ZSM-5 samples' surface,
corresponding to the stretching bands at around 1540 and 1450
cm\selectlanguage{english}\textsuperscript{-1}, respectively {[}9,46,47{]}. The peaks near 1490
cm \selectlanguage{english}\textsuperscript{-1} can be attributed to the pyridine species
interacting with B and L acid sites {[}48{]}. The ZSM-5 samples prepared
via enhancing micromixing no matter in the premixing or crystallization
process exhibit a larger amount of B and L acid sites at 200 \selectlanguage{english} (Table
4). For all ZSM-5 samples, compared to B acid sites, the amount of L
acid sites decreases obviously with the increasing temperature (Table
S1), indicating that the strength of L acid sites is weaker than B acid
sites {[}48{]}.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image15/image15}

\end{center}
\end{figure}

\textbf{Fig. 10.} FT-IR spectra after the adsorption of pyridine
followed with desorption of ZSM-5 samples obtained by different
operating processes.

\textbf{Table 4.} Quantification of acid sites according to the FT-IR
experiments.\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
sample & B\emph{\textsuperscript{a}}(\selectlanguage{greek}µ\selectlanguage{english}mol g\textsuperscript{-1}) &
L\emph{\textsuperscript{b}}(\selectlanguage{greek}µ\selectlanguage{english}mol g\textsuperscript{-1})\tabularnewline
\midrule
\endhead
ZSM-5-RD & 24.52 & 169.11\tabularnewline
ZSM-5-RS & 19.52 & 136.97\tabularnewline
ZSM-5-SD & 16.29 & 114.60\tabularnewline
ZSM-5-SS & 9.71 & 71.75\tabularnewline
\bottomrule
\end{longtable}

\emph{\textsuperscript{a}} Br\selectlanguage{ngerman}ønsted and \emph{\textsuperscript{b}} Lewis
acid amount at 200 \selectlanguage{english}.

\subsection*{3.3 Catalytic performance}

{\label{catalytic-performance}}

The cracking reaction of C4-olefin (OCC) to propylene in industries is
an important application of ZSM-5 zeolites, and the conversion of
C4-olefin and yield of propylene mostly depend on zeolites' acidity,
pore structure and catalytic stability {[}49{]}. In this study, we
investigated the catalytic performance of four ZSM-5 samples for the OCC
reaction. The conversion of C4-olefin and yield of propylene obtained
under the catalysis of different ZSM-5 samples are shown in Fig. 11. At
first, the C4-olefin's conversion and yield of propylene under the
catalysis by the four ZSM-5 samples had no obvious difference. However,
the conversions of C4-olefin catalyzed by the ZSM-5-SD and ZSM-5-SS
decreased faster than those by ZSM-5-RD and ZSM-5-RS after 16 h. And the
conversions of C4-olefin by the ZSM-5-RD, ZSM-5-RS, ZSM-5-SD, and
ZSM-5-SS were 65\% 62\%, 53\% and 53\% at 44 h, respectively. Besides,
the yield of propylene catalyzed by ZSM-5-RD and ZSM-5-RS were higher
markedly than those catalyzed by ZSM-5-SD and ZSM-5-SS after 30 h. This
indicates that ZSM-5 samples prepared by RPB premix possess more active
sites with weak Lewis acidity and medium-strong Bronsted acidity, less
transfer limitation in micropore, and more excellent catalytic stability
than those by STR premix.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image16/image16}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image17/image17}

\end{center}
\end{figure}

\textbf{Fig. 11.} (a) C4-olefin conversion and (b) propylene yield of
four ZSM-5 samples.

\section*{Conclusions}

{\label{conclusions}}

In conclusion, this work presented a novel route for the synthesis of
ZSM-5 zeolites by using RPB for enhancing micromixing of high viscosity
reaction system in the premix process. The as-prepared ZSM-5 zeolites by
RPB premix exhibited hierarchical structure, smaller average particle
size, more uniform particle size distributions, larger specific surface
areas, more Br\selectlanguage{ngerman}ønsted and Lewis acid sites, and higher catalytic
stability compared with those prepared by STR premix. Moreover,
enhancing micromixing by RPB could facilitate the formation of Al sites
and shorten the crystallization time. Also, the mechanisms of the
nucleation/crystal growth process of zeolites under different
micromixing intensity were studied. While adopting the prepared zeolites
for catalyzing C4-olefin cracking reaction, zeolites prepared via RPB
premix exhibited the remarkably higher conversion of C4-olefin and yield
of propylene. Generally, the RPB premix synthetic routes speeded up the
crystallization rate of zeolites and improved zeolites' catalytic
performance with the advantages of convenient processing,
cost-effectiveness, easy industrial scale-up.

\section*{References}

{\label{references}}

\begin{enumerate}
\tightlist
\item
  Ai S, Zheng MY, Jiang Y, Yang XF, Li XS, Pang JF, Sebastian J, Li WZ,
  Wang AQ, Wang XD, Zhang T. Selective removal of 1,2-propanediol and
  1,2-butanediol from bio-ethylene glycol by catalytic reaction. AIChE
  Journal. 2017; 63: 4032-4042.
\item
  Tian YJ, Liu H, Wang L, Zhang XW, Liu GZ. Controllable fabrication and
  catalytic performance of nanosheet HZSM-5 films by vertical secondary
  growth. AIChE Journal. 2018; 64: 1923-1927.
\item
  Corma A. From microporous to mesoporous molecular sieve materials and
  their use in catalysis. Chemical Reviews. 1997; 97: 2373-2420.
\item
  Quan YH, Li SY, Wang S, Li ZK, Dong M, Qin ZF, Chen G, Wei ZH, Fan WB,
  Wang JG. Synthesis of chainlike ZSM\selectlanguage{english}-5 zeolites: determination of
  synthesis parameters, mechanism of chainlike morphology formation, and
  their performance in selective adsorption of xylene isomers. ACS
  Applied Materials \& Interfaces. 2017; 9: 14899-14910.
\item
  Gao P, Xu GD, Wang C, Wang Q, Zhao YX, Zhang YH, Feng ND, Zhao XL, Li
  JL, Deng F. A mechanistic study of methanol-to-aromatics reaction over
  Ga-modified ZSM-5 zeolites: understanding the dehydrogenation process.
  ACS Catalysis. 2018; 8: 9809-9820.
\item
  Liang TY, Chen JL, Qin ZF, Li JF, Wang PF, Wang S, Wang GF, Dong M,
  Fan WB, Wang JG. Conversion of methanol to olefins over H\selectlanguage{english}-ZSM\selectlanguage{english}-5
  zeolite: reaction pathway is related to the framework aluminum siting.
  ACS Catalysis. 2016; 6: 7311-7325.
\item
  Martinez C, Corma A. Inorganic molecular sieves: Preparation,
  modification and industrial application in catalytic processes.
  Coordination Chemistry Reviews. 2011; 255: 1558-1580.
\item
  Subhan F, Aslam S, Yan ZF, Liu Z, Etim UJ, Wadood A, Ullah R.
  Confinement of mesopores within ZSM-5 and functionalization with Ni
  NPs for deep desulfurization. Chemical Engineering Journal. 2018; 354:
  706-715.
\item
  Jang HG, Min HK, Lee JK, Hong SB, Seo G. SAPO-34 and ZSM-5
  nanocrystals' size effects on their catalysis of methanol-to-olefin
  reactions. Applied Catalysis A: General. 2012; 437-438: 120-130.
\item
  Zholobenko VL, Kustov LM, Kazansky VB, Loeffler E, Lohser U, Peuker
  Ch, Oehlmann G. On the possible nature of sites responsible for the
  enhancement of cracking activity of HZSM-5 zeolites dealuminated under
  mild steaming conditions. Zeolite. 1990; 10: 304-306.
\item
  Hong Y, Gruver V, Fripiat JJ. Pentane Conversion on Dealuminated H-Y
  and HZSM-5. Journal of Catalysis. 1996; 161: 766-775.
\item
  Niwa M, Katada N, Murakami Y. Generation of acid sites by
  SiO\textsubscript{2} deposition on groups IVB metal oxides. Journal of
  Catalysis. 1992; 134: 340-348.
\item
  Ghosh AK, Kydd RA. Acidity and activity of fluorinated mordenites.
  Journal of Catalysis. 1987; 103: 399-406.
\item
  Zhao TT, Li FW, Yu HC, Ding SL, Li ZX, Huang XY, Li X, Wei XH, Wang
  ZL, Lin HF. Synthesis of mesoporous ZSM-5 zeolites and catalytic
  cracking of ethanol and oleic acid into light olefins. Applied
  Catalysis A: General. 2019; 575: 101-110..
\item
  Xu DD, Abdelrahman O, Ahn SH, Guefrachi Y, Kuznetsov A, Ren LM, Hwang
  SJ, Khaleel M, Hassan SA, Liu DX, Hong SB, Dauenhauer P. Tsapatsis M.
  A quantitative study of the structure--activity relationship in
  hierarchical zeolites using liquid-phase reactions. AIChE Journal.
  2018; 65: 1067-1075.
\item
  Kim S, Shah J, Pinnavaia T. Colloid-imprinted carbons as templates for
  the nanocasting synthesis of mesoporous ZSM-5 zeolite. Chemistry of
  Materials. 2003; 15: 1664-1668.
\item
  Narayanan S, Vijaya JJ, Sivasanker S, Kennedy LJ, Jesudoss SK.
  Structural, morphological and catalytic investigations on hierarchical
  zeolite ZSM-5 hexagonal cubes by surfactant assisted hydrothermal
  method. Powder Technology. 2015; 274: 338-348.
\item
  Dong A, Wang Y, Tang Y, Zhang Y, Ren N, Gao Z. Mechanically stable
  zeolite monoliths with three\selectlanguage{english}-dimensional ordered macropores by the
  transformation of mesoporous silica spheres. Advanced Materials. 2002;
  14: 1506-1510.
\item
  Xu R, Pang W, Yu J, Huo Q, Chen J. Chemistry of Zeolite and Related
  Porous Materials. Singapore: Wiley-VCH., 2007.
\item
  Askari S, Alipour SM, Halladj R, Hossein DAFM. Effects of ultrasound
  on the synthesis of zeolites: a review. Journal of Porous Materials.
  2013; 20: 285-302.
\item
  Yin X, Sun Q, Wang D, Routh AF, Le Y, Wang JX, Chen JF.
  High-gravity-assisted synthesis of aqueous nanodispersions of organic
  fluorescent dyes for counterfeit labeling. AIChE Journal. 2019; 65.
\item
  Sun Q, Chen B, Wu X, Wang M. Zhang C, Zheng XF, Wang JX, Chen JF.
  Preparation of transparent suspension of lamellar magnesium hydroxide
  nanocrystals using a high-gravity reactive precipitation combined with
  surface modification. Industrial \& Engineering Chemistry Research.
  2015; 54: 666-671.
\item
  Zheng XH, Chu GW, Kong DJ, Luo Y, Zhang JP, Zou HK, Zhang LL, Chen JF.
  Mass transfer intensification in a rotating packed bed with
  surface-modified nickel foam packing. Chemical Engineering Journal.
  2016; 285: 236-242.
\item
  Chen JF, Wang YH, Guo F, Wang XM, Zheng C. Synthesis of nanoparticles
  with novel technology: high-gravity reactive precipitation. Industrial
  \& Engineering Chemistry Research. 2000; 39: 948-954.
\item
  Guo K, Zhang ZZ, Luo HJ, Dang JX, Qian Z. An innovative approach of
  the effective mass transfer area in the rotating packed bed.
  Industrial \& Engineering Chemistry Research. 2014; 53: 4052-4058.
\item
  Rao DP, Bhowal A, Goswami PS. Process intensification inrotating
  packed beds (HIGEE): anappraisal. Industrial \& Engineering Chemistry
  Research. 2004; 43: 1150-1162.
\item
  Biligetu T, Wang Y, Nishitoba T, Otomo R, Park S, Mochizuki H, Kondo
  JN, Tatsumi T, Yokoi T. Al distribution and catalytic performance of
  ZSM-5 zeolites synthesized with various alcohols. Journal of
  Catalysis. 2017; 353: 1-10.
\item
  Itani L, Liu Y, Zhang WP, Bozhilov KN, Delmotte L, Valtchev V.
  Investigation of the physicochemical changes preceding zeolite
  nucleation in a sodium-rich aluminosilicate gel. Journal of the
  American Chemical Society. 2009; 131: 10127--10139.
\item
  Kosanovi\selectlanguage{polish}ć \selectlanguage{english}C, Bosnar S, Suboti\selectlanguage{polish}ć \selectlanguage{english}B, Svetlicic V, Radi\selectlanguage{polish}ć \selectlanguage{english}TM, Dra\selectlanguage{polish}ž\selectlanguage{english}i\selectlanguage{polish}ć \selectlanguage{english}G,
  Havancs\selectlanguage{ngerman}ák K. Study of the microstructure of amorphous aluminosilicate
  gel before and after its hydrothermal treatment. Microporous and
  Mesoporous Materials. 2008; 110: 177--185.
\item
  Valtchev VP, Bozhilov KN. Transmission electron microscopy study of
  the formation of FAU-type zeolite at room temperature. The Journal of
  Physical Chemistry B. 2004; 108: 15587-15598.
\item
  Yang SY, Navrotsky A, Phillips BL. An in situ calorimetric study of
  the synthesis of FAU zeolite. Microporous and Mesoporous Materials.
  2001; 46: 137-151.
\item
  Bauer F, Geidel E, Peuker Ch, Pilz W. Vibrational spectra
  of\textsuperscript{18}O-exchanged NaZSM-5 and HZSM-5. Zeolite. 1996;
  17: 278-282.
\item
  Mintova S, Olson NH, Valtchev V, Bein T. Mechanism of zeolite A
  nanocrystal growth from colloids at room temperature. Science. 1999;
  283: 958-960.
\item
  Aiello R, Crea F, Nastro A, Suboti\selectlanguage{polish}ć \selectlanguage{english}B, Testa F. Influence of cations
  on the physicochemical and structural properties of aluminosilicate
  gel precursors. Part 1. Chemical and thermal properties. Zeolite.
  1991; 11: 767-775.
\item
  Shirazi L, Jamshidi E, Ghasemi MR. The effect of Si/Al ratio of ZSM-5
  zeolite on its morphology, acidity and crystal size. Crystal Research
  and Technology. 2008; 43: 1300-1306.
\item
  Fu DL, Schmidt J, Ristanovi\selectlanguage{polish}ć \selectlanguage{english}Z, Chowdhury AD, Meirer F, Weckhuysen BM.
  Highly oriented growth of catalytically active zeolite ZSM-5 films
  with a broad range of Si/Al ratios. Angewandte Chemie International
  Edition. 2017; 129: 11369 --11373.
\item
  Malfait WJ, Xue XY. The nature of hydroxyl groups in aluminosilicate
  glasses: Quantifying Si--OH and Al--OH abundances along the
  SiO\textsubscript{2}--NaAlSiO\textsubscript{4} join
  by\textsuperscript{1}H, \textsuperscript{27}Al--\textsuperscript{1}H
  and\textsuperscript{29}Si--\textsuperscript{1}H NMR spectroscopy.
  Geochimica et Cosmochimica Acta. 2010; 74: 719-737.
\item
  Dib E, Mineva T, Veron E, Sarou-Kanian V, Fayon F, Alonso B. ZSM-5
  zeolite: complete al bond connectivity and implications on structure
  formation from solid-state NMR and quantum chemistry calculations. The
  Journal of Physical Chemistry Letters. 2018; 9: 19-24.
\item
  Valtchev VP, Bozhilov KN. Evidences for zeolite nucleation at the
  solid-liquid interface of gel cavities. Journal of the American
  Chemical Society. 2005; 127: 16171-16177.
\item
  Wang YX, Song JJ, Baxter NC, Kuo GT, Wang SN. Synthesis of
  hierarchical ZSM-5 zeolites by solid-state crystallization and their
  catalytic properties. Journal of Catalysis. 2017; 349: 53-65.
\item
  Wang YQ, Wu QM, Meng XJ, Xiao FS. Insights into the
  organotemplate-free synthesis of zeolite catalysts. Engineering, 2017;
  3: 567-574.
\item
  Liu BY, Xie KH, Oh SC, Sun DL, Fang YX, Xi HX. Direct synthesis of
  hierarchical USY zeolite for retardation of catalyst deactivation.
  Chemical Engineering Science. 2016; 153: 374-381.
\item
  Yang ZX, Xia YD, Mokaya R. Zeolite ZSM-5 with unique supermicropores
  synthesized using mesoporous carbon as a template. Advanced Materials.
  2004; 16: 727-732.
\item
  Xing AH, Yuan DL, Tian DY, Sun Q. Controlling acidity and external
  surface morphology of SAPO-34 and its improved performance for
  methanol to olefins reaction. Microporous and Mesoporous Materials.
  2019; 288: 109562.
\item
  Rodr\selectlanguage{ngerman}íguez-González L, Hermes F, Bertmer M, Rodríguez-Castellón E,
  Jiménez-López A, Simon U. The acid properties of H-ZSM-5 as studied by
  NH\textsubscript{3}-TPD and \textsuperscript{27}Al-MAS-NMR
  spectroscopy. Applied Catalysis A: General. 2007; 328: 174-182.
\item
  Na K, Alayoglu S, Ye R, Somorjai GA. Effect of acidic properties of
  mesoporous zeolites supporting Pt nanoparticles on hydrogenative
  conversion of methylcyclopentane. Journal of the American Chemical
  Society. 2014; 136: 17207-17212.
\item
  Wang N, Hou YL, Sun WJ, Cai DL, Chen ZH, Liu LM, Ge BH, Hu L, Qian WZ,
  Wei F. Modulation of b-axis thickness within MFI zeolite: Correlation
  with variation of product diffusion and coke distribution in the
  methanol-to-hydrocarbons conversion. Applied Catalysis B:
  Environmental. 2019; 243: 721-733.
\item
  Lou Y, Ma J, Hu WD, Dai QG, Wang L, Zhan WC, Guo YL, Cao XM, Guo Y, Hu
  P, Lu GZ. Low-temperature methane combustion over Pd/H-ZSM-5: active
  Pd sites with specific electronic properties modulated by acidic sites
  of H\selectlanguage{english}-ZSM\selectlanguage{english}-5. ACS Catalysis. 2016; 6: 8127\selectlanguage{english}-8139.
\item
  Shi J, Zhao GL, Teng JW, Wang YD, Xie ZK. Morphology control of ZSM-5
  zeolites and their application in Cracking reaction of C4 olefin.
  Inorganic Chemistry Frontiers. 2018; 5: 2734-2738.
\end{enumerate}

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