Temperature-controlled phase-transfer hydrothermal synthesis of MWW zeolites and their alkylation performances

Article abstract of DOI:10.1039/c5ra25503a

MWW zeolites have been synthesized with hexamethyleneimine/aniline as the structure-directing/ promoting agent. As structure-promoting agent, aniline contributes to the crystallization of MWW zeolites without being trapped within zeolites. Meanwhile the t

Full text of DOI:10.1039/c5ra25503a

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: E. Xing, Y. Shi, W.
Xie, F. Zhang, X. Mu and X. Shu, RSC Adv., 2016, DOI: 10.1039/C5RA25503A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Page 1 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
Temperature-controlled phase transfer hydrothermal synthesis of
MWW zeolites and their alkylation performances
Enhui Xing, Yanchun Shi, Wenhua Xie, Fengmei Zhang*,Xuhong Mu and Xingtian Shu.
State Key Laboratory of Catalytic Materials and Reaction Engineering, Research Institute of
Petroleum Processing, Sinopec, Beijing 100083, China
*
Corresponding author: Prof. Fengmei Zhang
Tel: +86 010ꢀ82368698
Eꢀmail: zhangfm.ripp@sinopec.com (F. M. Zhang)
1

RSC Advances
Page 2 of 35
View Article Online
DOI: 10.1039/C5RA25503A
Abstract:
MWW zeolites were synthesized with hexamethyleneimine/aniline as the structureꢀ
directing/promoting agent. As structureꢀpromoting agent, aniline contributes to the crystallization of
MWW zeolites without being trapped within zeolites. Meanwhile the temperatureꢀcontrolled phase
transfer hydrothermal synthesis of MWW zeolites could be achieved because the solubility of
aniline increases with the rise of temperature. For delaminated MCMꢀ56 with intermediate nature,
the conversion to MCMꢀ49 could be avoided even subject to much longer crystallization time.
Partially delaminated MWW monolayers of MCMꢀ56 possesses larger external surface area, pore
volumes, better accessibility of active centers, which resulted in higher ethylene conversion than
o
MCMꢀ22 and MCMꢀ49 in the liquidꢀphase alkylation of benzene with ethylene above 210 C.
Keywords: MCMꢀ22; MCMꢀ49; MCMꢀ56; temperatureꢀcontrolled phase transfer hydrothermal
synthesis; structureꢀpromoting agent; aniline
2

Page 3 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
1
. Introduction
As typical MWW (Framework Type Code assigned by International Zeolite Association)
1
ꢀ13
zeolites,
MCMꢀ22 and MCMꢀ49 are consisting of three pore systems: twoꢀdimensional,
sinusoidal, 10 memberedꢀring (MR) intralayer channels, 12 MR interlayer supercages with 10 MR
apertures and 12 MR cups on the external surface (half of 12 MR supercages). However MCMꢀ56
is considered as the first monoꢀlayered (delaminated) zeolite with MWW topology comprising
layers stacked disorderly without interlayer connectivity. Generally with more exposed 12 cups on
the external surface, MCMꢀ56 was not expected to contain supercages at least in its idealized form.
MCMꢀ56 could be viewed as delaminated zeolite obtained by direct synthesis and it is the only one
prepared with simple structureꢀdirecting agents (SDAs). The Xꢀray diffraction (XRD) patterns of
asꢀsynthesized MCMꢀ22, i.e., MCMꢀ22 precursor (MCMꢀ22P), shows one of feature peaks at 2θ
o
6
.6 , ascribed to interlayer [002] reflection, and the c parameter is 2.7 nm, which could be
envisioned as MCMꢀ22P with layers linked by hydrogen bonded silanol pairs between neighboring
1
3,14
surface in presence of SDAs.
Via calcination, MCMꢀ22P undergoes a significant structure
change and conversion to MCMꢀ22C with complete 3D structure as the evidence of [002] reflection
disappeared in corresponding XRD, like the case of asꢀsynthesized/calcined MCMꢀ49 (c parameter
13
2
.5 nm). As for MCMꢀ22C, the contraction of c parameter approximately 0.2 nm is attributed to
the condensation of the surface SiꢀOH groups and formation of TꢀOꢀT interlayer bridges via thermal
oxidative destroy of hydrogen bonded silanol pairs by HMI between two MWW layers. As the
intermediate of MCMꢀ49, a notable feature of asꢀsynthesized MCMꢀ56 comprises a collection of
monolayers, disordered/misaligned and unbound except for possible coincidental cross linking,
o
which is the continuous scattering in the 8 ~ 10 2θ range. As monolayer MWW zeolite, the c
6
,15
parameter of MCMꢀ56 is also 2.5 nm. Therefore, every individual material of MWW family
differs in the distance between the layers and the translation in the degree of regularity/irregularity
16ꢀ18
in organization of neighboring layers.
As MCMꢀ56 could be further transformed to MCMꢀ49
3

RSC Advances
Page 4 of 35
View Article Online
DOI: 10.1039/C5RA25503A
phase, two 12 MR cups on the neighboring MWW layer are transformed to one 12 MR supercage
via the formation of oxygenꢀbridge with 10 MR windows. Therefore, MCMꢀ56 has more 12 MR
cups with little 12 MR supercages in idealized conditions than MCMꢀ49 and MCMꢀ22C with
regular connection between individual layers via oxygenꢀbridge bonding. Individual MCMꢀ56 layer
is considered to be a partially delaminated zeolite comprising a disordered collection of MWW
monolayers and having a large portion of exposed external surface. According to published data, 12
MR cups are claimed to provide more useful architecture with unexpected performances especially
19ꢀ24
in the alkylation of aromatics.
In summary, hexamethyleneimine (HMI), piperidine, diethylꢀdimethylꢀammonium hydroxide,
N,N,Nꢀtrimethylꢀ1ꢀadamantanammoniumhydroxide,
1,4ꢀbis(Nꢀmethylpyrrolidinium)
butane,
N,N,N,N',N',N'ꢀhexamethylꢀ1,5ꢀpentaneꢀdiammonium,
N,N,N,N',N',N'ꢀhexamethylꢀ1,6ꢀhexaneꢀ
1
ꢀ10, 25ꢀ29
diammonium and others have been reported to be SDAs to form MWW zeolites,
however
for aluminosilicate MWW zeolites, HMI is the most efficient SDA, especially for MCMꢀ22, MCMꢀ
4
9 and MCMꢀ56 in similar conditions because of its effective structureꢀdirecting capability and low
2,4ꢀ13
cost.
In our recent publications, aniline (AN) was introduced as the structureꢀpromoting agent
(SPA) to couple with HMI as the SDA to achieve temperatureꢀcontrolled phase transfer
3
0ꢀ32
hydrothermal synthesis of MCMꢀ22/49 zeolites.
The improved solubility of aniline with
33
temperature in water was summarized by Stephen et al. Poor solubility of aniline at room
temperature leads to phase separation of organic phase and mother liquor before crystallization.
While after crystallization, poor solubility of aniline provides the simple method to recover HMI
o
and aniline by liquid separation. During crystallization (Temperature at 145 C, AN/SiO = 0.2,
2
2 2 2
HMI/SiO = 0.1, H O/SiO = 15), both HMI and aniline became completely soluble to favor the
o
30
formation of MWW zeolites above 110 C according to previous results. With aniline only, no
formation of MWW phase could be observed because of p–π conjugation which led to low electro
b
negativity and low alkalinity in water (pK = 4.78). However lack of aniline leads to insufficient
crystallization with HMI/SiO = 0.10. More interestingly, it seemed that aniline was not occluded
2
4

Page 5 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
into MWW zeolites. According to above results, aniline is regard to be the SPA, which does
contribute to the formation of MWW zeolites, but not trapped within MWW zeolites, ie, there was
almost no consumption of aniline during the synthesis of MWW zeolites. To some extent, aniline as
the SPA could be regarded as the “catalyst” of the whole process. In all aniline acts as the phase
transfer medium, extractor of HMI and the SPA during the temperatureꢀcontrolled phase transfer
hydrothermal synthesis of MCMꢀ22 zeolite, which decreased HMI trapped within MWW zeolites
by about 1/3. (ref. 31) It seemed that the involvement of aniline could offer a facile method to
generate MWW zeolites with less economical and environmental impacts.
MCMꢀ22 synthesized through temperatureꢀcontrolled phase transfer hydrothermal synthesis,
was nearly identical concerning chemical composition and structure, and showed nearly identical
property with respect to porosity, SiO /Al O ratio, thermal behavior and similar catalytic ethylation
2
2
3
performance, compared with that made from reference synthesis with HMI as the only SDA. The
difference lies in the cut in the HMI usage by at least 2/3 and about 1/3 decrease in HMI trapped
3
0,31
within MCMꢀ22 zeolites.
In this paper, we expanded the concept of SPA and temperatureꢀ
controlled phase transfer hydrothermal synthesis to MCMꢀ49 and MCMꢀ56, all of which could be
synthesized in similar conditions with HMI as the SDA. Also, aluminosilicate MWW zeolites were
given to detailed research on their property, acidity and catalytic alkylation performance. As well
known, the crucial issue of delaminated MCMꢀ56 zeolite lies in its intermediate nature and
conversion to MCMꢀ49 if not quenched at the right time. Besides the advantages of temperatureꢀ
controlled phase transfer hydrothermal synthesis, other improvements in reproducibility and
stability of high quality MCMꢀ56 has always been desired. Therefore we anticipate that the
involvement of aniline could lead to the original and significant advance for similar systems to
obtain high quality MCMꢀ56, the only prepared MWW zeolite with simple SDAs for improvement
its alkylation performance.
2
. Experimental
2
.1 Synthesis of MWW zeolites and catalysts
5

RSC Advances
Page 6 of 35
View Article Online
DOI: 10.1039/C5RA25503A
All materials (solid silica gel, fumed SiO , NaAlO , NaOH, HMI, aniline and deionized water)
2
2
were used as purchased. The molar ratios of typical batch composition and hydrothermal synthesis
conditions were shown in Table 1. The hydrothermal synthesis was conducted in Teflonꢀlined
autoclaves (25 mL) with tumbling condition at 30 rpm and a stainlessꢀsteel vessel (2500 mL) with
stirring speed at 400 rpm. The synthesized samples were filtrated, washed with deionized water
o
o
until pH = 7, and dried at 100 C overnight. Synthesized samples were calcined at 550 C in
ambient air for 6 h in a muffle furnace to remove organics. Hꢀtype zeolites/catalysts were prepared
3
4ꢀ37
according to method described in our previous publications.
.2 Characterization of MWW zeolites
XRD patterns of samples were collected on a D/MAXꢀIII Xꢀray diffractometer (Rigaku
2
Corporation, Japan) with filtered Cu K α radiation at a tube current of 35 mA and a voltage of 35
kV. The scanning range of 2θ was 5~35°.The crystal morphology was measured on a FEI Quanta
scanning electron microscope (SEM). The elemental analyses of the solids were performed on an
Xꢀray fluorescence (XRF) spectrometer MagiX (Philips). Nitrogen adsorptionꢀdesorption isotherms
were recorded on a Micromeritics ASAP 2010 instrument. The samples were first outgassed under
vacuum at 363 K for 1 h and at 623 K for 15 h. The total surface area was obtained by application
of the BET equation using the relative pressure range of 0.05 ~ 0.16 in the nitrogen adsorption
2
isotherm as range of linearity (using a molecular crossꢀsectional area for N
2
of 0.162 nm ). The
micropore volume was calculated by the tꢀplot method. The external surface area was calculated by
the formula as Sexternal = SBET ꢀ Smicro
The acidity of Hꢀtype zeolites was measured by temperature programmed desorption (TPD)
and Fourier transform infrared spectrometer (FTIR), using ammonia (NH
trimethylꢀpyridine as probe molecules, respectively. NH ꢀTPD was carried out on an Autochem II
920 unit equipped with a thermal conductivity detector. For FTIR spectroscopy of adsorbed probe
3
) and pyridine/2,4,6ꢀ
3
2
molecules (pyridine and 2,4,6ꢀtrimethylꢀpyridine), all samples were pressed into selfꢀsupporting
wafers and measured in transmission mode in an FTS3O00 FTIR spectrometer by 64 scans with a
6

Page 7 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
ꢀ1
ꢀ3
resolution of 4 cm . Prior to the measurements, each sample was dehydrated under vacuum 10 Pa
o
o
at 350 C for1 h, and then cooled to 50 C for pyridine adsorption. The IR spectra of the samples
before pyridine/2,4,6ꢀtrimethylꢀpyridine adsorption were recorded at different temperatures (200
o
ꢀ3
and 350 C), and after adsorbing pyridine for 10 s, the samples were purged under vacuum 10 Pa
o
ꢀ1
to higher temperature at a heating rate of 10 C·min . Then the IR spectra of pyridine on samples
o
were recorded at different temperatures (200 and 350 C), while IR spectra of pyridine was
o
collected at 200 C. All the spectra given in this work were differential spectra. The number of
Brønsted and Lewis acid sites was calculated according to adsorbed pyridine IR peak area, and the
number of acid sites by 2,4,6ꢀtrimethylꢀpyridine was calculated based upon adsorbed 2,4,6ꢀ
o
trimethylꢀpyridine IR peak height at 200 C.
2
9
27
Si/ Al MAS NMR experiments were performed on a Bruker AVANCE III 500WB/600WB
spectrometer at a resonance frequency of 99.3/156.4 MHz using a 7/4 mm doubleꢀresonance MAS
probe with a recycle delay of 4/1 s respectively. The magicꢀangle spinning rate was 5/13 kHz in all
29
27
experiments, and a typical length of 1.8/0.4 ꢁs was adopted for Si/ Al resonance respectively.
29
27
3 3
The chemical shift of Si/ Al was referenced to tetramethylsilane (TMS)/1 M aqueous Al (NO )
1
3
respectively. C CP/MAS NMR experiments were performed on a Bruker AVANCE III 600WB
spectrometer at a resonance frequency of 150.9 MHz using a 4 mm doubleꢀresonance MAS probe at
1
3
a sample spinning rate of 7.5 kHz. The chemical shift of C was determined using a solid external
13
reference, hexamethylbenzene (HMB). C CP/MAS NMR spectra were recorded by using a recycle
13
delay of 5 s and a contact time of 2 ms. The liquid C NMR experiments were performed on a
Varian INOVA 500 spectrometer at a resonance frequency of 125.6 MHz using a 5 mm doubleꢀ
1
3
13
resonance probe. The chemical shift of C was referenced to tetramethylsilane. C NMR spectra
were recorded by smallꢀflip angle technique using a pulse length of 3.2 ms (π/6) and a recycle delay
of 4 s.
2
.3 Liquid-phase alkylation of benzene with ethylene
7

RSC Advances
Page 8 of 35
View Article Online
DOI: 10.1039/C5RA25503A
The liquidꢀphase alkylation of benzene with ethylene was carried out in a stainlessꢀsteel fixed
bed reactor. The catalyst (8 mL) was placed in the center of the reactor, and purged with nitrogen.
Benzene was pumped into reactor to fill the bed fully under reaction pressure, and then the
o
temperature was raised up to 200 C before ethylene was introduced. The alkylation conditions
ꢀ1
were as follows: pressure of 3.5 MPa, weight hourly space velocity (WHSV) of benzene of 3 h ,
o
and molar ratio of benzene/ethylene 12/1, 200 to 260 C of temperature. At each temperature the
reaction was given at least 15 h to reach a steady state condition before samples were collected for
analysis. The reaction products were analyzed by an Agilent 6890 gas chromatograph (GC)
equipped with a flame ionization detector and a capillary column. It is well known that the
alkylation of benzene with ethylene was a consecutive reaction, and the reaction products were
made up of EB, paraꢀdiethylbenzene (pꢀDEB), orthoꢀdiethylbenzene (oꢀDEB), metaꢀ
diethylbenzene (mꢀDEB), triethylbenzenes (TEB), other byꢀproducts (diphenylethane) in our work.
The ethylene conversion, EB selectivity, DEB selectivity and DEB selectivity distribution were
calculated based upon formulas as follows:
H = xEB/MEB + 2xDEB/MDEB + 3xTEB/MTEB + xdiphenylethane/Mdiphenylethane
;
xDEB = xpꢀDEB + xoꢀDEB + xmꢀDEB
;
M: molar mass (g/mol);
x: mass percentage concentration (wt.%) from GC analysis;
H: molar number percentage concentration (mol %) of ethyl;
(
(
(
(
1) Ethylene conversion (%): Cethylene = H/(H + xethylene/Methylene) × 100 %
2) EB selectivity (%): SEB = x /(x + xDEB + xTEB + xdiphenylethane) × 100 %
EB
EB
3) DEB selectivity (%): SDEB = xDEB/(xEB + xDEB + xTEB + xdiphenylethane) × 100 %
4) TEB selectivity(%): STEB = xTEB/(xEB + xDEB + xTEB + xdiphenylethane) × 100 %
3
. Results and discussion
3
.1 Synthesis of MWW zeolites
8

Page 9 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
MCMꢀ22 (Table 1 sample 4), MCMꢀ49 (Table 1 sample 5) and MCMꢀ56 (Table 1 sample 7
and 8) zeolites are characterized by XRD analysis (Fig. 1). MCMꢀ22P showed the typical [002]
diffraction peak at ca. 6.6° 2θ due to the layer stacking of the MWW sheets with HMI trapped into
14,22
zeolites by forming the hydrogen bonded silanol pairs between two MWW layers.
After
calcination HMI could be completely removed, which generated 3D MWW structure via interlayer
dehydroxylation and condensation. Another region between 26 and 29° could also distinguish
MCMꢀ22P from MCMꢀ49 and MCMꢀ22C. In this region, MCMꢀ22P possessed only one broad
peak centered at 26.22° with a smooth, sloping tail visible on the high 2θ side. For MCMꢀ49 and
MCMꢀ22C this feature was replaced by three sharp peaks, occurring in the approximate region 26.5
~
29.0°. As for asꢀsynthesized MCMꢀ56 (Table 1 sample 7 and 8), there was a relatively sharp peak
o
o
at 7.1 2θ companied by a typical broad band range in 8 ~ 10 2θ. However, there was slight
o
separation at 8 ~ 10 2θ for HꢀMCMꢀ56 and the intensity of other peaks became slightly stronger
indicative of partial ordering.
Generally even slight change in material sources or in synthetic conditions often led to mixture
of MCMꢀ22/49 or MCMꢀ56/49 especially when the synthesis were conducted with SiO
2 2 3
/Al O
feeding ratio between 25 and 30, the borderline of MCMꢀ22/49. Compared with our previous
30
work, it also happened that MCMꢀ22 (Table 1 sample 6) and MCMꢀ56 (Table 1 sample 7 and 8)
synthesized in the same feeding composition with fumed SiO as silica source, the only difference
2
lied in the autoclave (25 mL / 2.5 L) under tumbling/stirring condition at 30/400 rpm respectively,
so did for sample 3 (mixture of MCMꢀ22 and MCMꢀ49) and 5 (MCMꢀ49) with solid silica gel as
30
the silica source in Table 1. Based upon our previous results, as the SPA aniline favored the
formation of MCMꢀ49 due to lower content of HMI. Similarly, the results might disclose that the
hydrothermal synthesis conditions (silica source, reactor and mixing speed) influenced the crystal
2
phase of final product; the better mixing of raw materials (fumed SiO ) during hydrothermal
synthesis showed the tendency towards the formation of MCMꢀ56 with partially delaminated and a
disordered collection of MWW monolayers. MCMꢀ56 could be easily transformed into MCMꢀ49
9

RSC Advances
Page 10 of 35
View Article Online
DOI: 10.1039/C5RA25503A
with regular 3D MWW structure with longer heating time and be regarded as the intermediate of
8
MCMꢀ49 during the synthesis. However, there was no other competing phase during MCMꢀ56
synthesis even though the crystallization time from 72 to 168 h (Table 1 sample 8, and Fig. 1d) in
2 2
the HMI/AN system with high H O/SiO ratio without transformation to MCMꢀ49 phase, indicating
that this strategy would be exploited and modified to obtain high quality MCMꢀ56 with improved
stability. With aniline as the SPA, MCMꢀ56 could be obtained with HMI/SiO at 0.10, only 1/3 or
2
19ꢀ24
less than HMI usage in other’s research.
Above results might provide a facile and reproducible
method to generate stable MCMꢀ56 with less economical and environmental impacts due to the
properties of temperatureꢀcontrolled phase transfer hydrothermal synthesis.
It has been proven that there were three resonances centered at about 27, 49 and 57 ppm,
which was ascribed to C2/C3, C1 (intralayer) and C1 (interlayer) of HMI for asꢀmade MWW
1
3
13
zeolites synthesized in HMI only system. However, C CP/MAS NMR spectra of asꢀsynthesized
MCMꢀ22, MCMꢀ49 and MCMꢀ56 via temperatureꢀcontrolled phase transfer hydrothermal synthesis
clearly showed two resonances of organics trapped within MWW zeolites. The resonances centered
at about 27 ppm was ascribed to overlapped C2 and C3 resonances of HMI, and the other located at
3
0
4
9 ppm was related to C1 resonance of HMI (Fig. 2a). Similar to our previous results, remarkably
decreased C1 resonance at 57 ppm supported the promoting effect of aniline as the SPA during the
hydrothermal synthesis. However no resonances of aniline were detected on the asꢀsynthesized
MWW zeolites even with much longer characterization test, which drove us to consider aniline as
the “catalyst” in the temperatureꢀcontrolled phase transfer hydrothermal synthesis. In order to verify
13
this issue, asꢀsynthesized MWW zeolites were treated by HF for liquid C NMR test (Fig. 2b), the
results of which clearly proved that there was no aniline trapped within asꢀsynthesized MWW
zeolites. The promoting effects on the crystallization of aniline without being trapped within MWW
zeolites strongly support the role of SPA during the temperatureꢀcontrolled phase transfer
hydrothermal synthesis.
3
.2 Physiochemical property of H-MWW zeolites
10

Page 11 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
Fig. 3a and 3b show typical morphology of HꢀMCMꢀ22 and HꢀMCMꢀ49 with roseꢀlike shape
at about several ꢁm. However, HꢀMCMꢀ56 appeared as some overlapped plateꢀlike crystals of less
than 20 nm in thickness (Fig. 3c), which was totally different in the morphology of HꢀMCMꢀ22 and
HꢀMCMꢀ49. HꢀMCMꢀ56 with very thinness of plateꢀlike crystals aggregated at high stacking
disorder, is supposed to be a partially delaminated and disordered collection of MWW monolayers
with larger outer surface area exposing more 12 MR cups on the external surface and more acid
sites accessed by reactants/probe molecules.
2 2
The nitrogen (N ) isotherms of Hꢀtype zeolites are presented in Fig. 4. Obviously, the N
adsorption amounts of HꢀMCMꢀ56 were higher than HꢀMCMꢀ22 and HꢀMCMꢀ49, which was
related to the special morphology of stacking disorder for HꢀMCMꢀ56 layers’ accumulation. Hꢀ
MCMꢀ22, HꢀMCMꢀ49 and HꢀMCMꢀ56 were typical microporous zeolites, which was consistent
2
0,38
with the reported results.
However, the clear hysteresis for HꢀMCMꢀ56 was observed at high
relative pressures (p/p = 0.7 ~ 0.98), unlike the case of HꢀMCMꢀ22 and HꢀMCMꢀ49, which
0
disclosed that the presence of a larger mesoporosity of HꢀMCMꢀ56 originated from a disordered
collection of partially delaminated MWW monolayers.
Table 2 presents the BET analysis of Hꢀtype zeolites. As we anticipated that HꢀMCMꢀ56
2
ꢀ1
3
ꢀ1
showed much lower micro surface area (298 m ·g ) and micro volumes (0.14 cm ·g ) than Hꢀ
2
ꢀ1
MCMꢀ22 and HꢀMCMꢀ49, however HꢀMCMꢀ56 (145 m ·g ) showed almost as twice as the
2
ꢀ1
2
ꢀ1
external surface area as those of HꢀMCMꢀ22 (69 m ·g ) and HꢀMCMꢀ49 (75 m ·g ). The reason
lied in the preservation of 10 MR intralayer channels and more formation of 12 MR cups due to
partially delaminated and a disordered collection of MWW monolayers, which led to the formation
3
ꢀ1
2
of the clear hysteresis in the N isotherms and obviously enhanced total pore volumes (0.79 cm ·g )
3
ꢀ1
3
ꢀ1
compared to HꢀMCMꢀ22 (0.52 cm ·g ) and HꢀMCMꢀ56 (0.57 cm ·g ). As stated in the
introduction, 12 MR cup have been proven to be more beneficial for excellent performances
38ꢀ41
especially in the alkylation of aromatics.
It is expected that the larger external surface area
means more 12 MR cups for acid sites and active centers accessed by probe molecules/reactants,
11

RSC Advances
Page 12 of 35
View Article Online
DOI: 10.1039/C5RA25503A
which would be definitely beneficial for catalytic performances in the liquidꢀphase alkylation of
benzene with ethylene.
2
9
27
Si/ Al MAS NMR spectra of asꢀsynthesized and Hꢀtype zeolites are given in Fig. 5, which
2
9
27
shows the poorly separated resonances for MWW zeolites Si/ Al. Because of the same MWW
topology structure and the chemical shift of the framework Si & Al depending strongly on the
geometric environment of each Si & Al atom, there was no significant difference in the resonances
2
9
of Si(0Al)&Si(1Al) species from ꢀ100 to ꢀ119 ppm ( Si MAS NMR spectra) and from 49 to 61
2
7
13,38
ppm ( Al MAS NMR spectra) among three MWW zeolites.
ppm of HꢀMCMꢀ56 seemed slightly larger than those of MCMꢀ22 and MCMꢀ49. Regardless of
difference in feeding SiO /Al ratio, the final MWW zeolites had similar bulk SiO /Al ratio,
which indicating similar Al O content. Since increase in resonances at ꢀ100 ppm of HꢀMCMꢀ56
However the signal peak at ꢀ100
2
2
O
3
2
2 3
O
2
3
would be originated from SiꢀOH rather than (SiO)3Si(OHAl). MCMꢀ56 with partially delaminated
and a disordered collection of MWW monolayers led to more framework Si defects formation.
There was no resonances of the extraꢀframework Al for all asꢀsynthesized samples; after
calcinations, the framework Al became distinguishable due to slight differences in the connection of
MWW layers and the dealumination usually caused the formation of extraꢀframework Al at about 0
13,42ꢀ46
ppm as reported before.
3
.3 Acidity of H-type zeolites
2 2 3
Three Hꢀtype zeolites have slightly different SiO /Al O ratios at 25 (HꢀMCMꢀ22), 23 (Hꢀ
MCMꢀ49) and 24 (HꢀMCMꢀ56). Generally speaking, the acid sites determined by base probes are
influenced by the size of selected probes. In this section, base probes with different molecule sizes
3
were selected to detect the acid sites of three HꢀMWW zeolites. NH was selected because of little
diffusion restriction into MWW pore systems. Pyridine (kinetic diameter 0.58 nm) with identical
kinetic diameter as benzene (kinetic diameter 0.58 nm) was selected to reveal reactant selectivity.
As well known, the size of benzene is smaller than that of 2,4,6ꢀtrimethylꢀpyridine (kinetic diameter
0
.74 nm). Similarly, the size of transitional states in EB formation process, which could be imaged
12

Page 13 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
as elongated benzene and therefore much smaller than 2,4,6ꢀtrimethylꢀpyridine, especially in
comparison to the opening in the 12 MP cups. Based upon other’s results, 2,4,6ꢀtrimethylꢀpyridine
was selected to determine the acid sites located in the 12 MR cups on the external surface of MWW
zeolites, which were postulated to be main active centers for liquidꢀphase alkylation of benzene
31,47ꢀ49
with ethylene.
Fig. 6 shows the NH ꢀTPD curves of Hꢀtype zeolites. As the case of HꢀMWW zeolites
3
o
o
exhibited two desorption peaks with the temperature range 200 ~ 250 C and 380 ~ 420 C, ascribed
to NH desorbed from weak and strong acid sites, respectively. The amounts of acid sites for Hꢀ
3
MCMꢀ22 and HꢀMCMꢀ56 zeolites were similar to each other, but for HꢀMCMꢀ49, there were
higher amounts of both weak and strong acid sites than HꢀMCMꢀ22 and HꢀMCMꢀ56. PyꢀFTIR
results of three HꢀMWW zeolites are presented in Table 3. The number of Lewis acid sites were
ꢀ1
ꢀ1
ꢀ1
2
88 µmol·g for HꢀMCMꢀ22, 213 µmol·g for HꢀMCMꢀ49, and 312 µmol·g for HꢀMCMꢀ56 at
o
ꢀ1
ꢀ1
ꢀ1
2
00 C, 119 µmol·g for HꢀMCMꢀ22, 182 µmol·g for HꢀMCMꢀ49, and 260 µmol·g for Hꢀ
o
ꢀ1
MCMꢀ56 at 350 C; The number of Br nsted acid sites were 178 µmol·g for HꢀMCMꢀ22, 352
Ø
ꢀ1
ꢀ1
o
ꢀ1
µmol·g for HꢀMCMꢀ49, and 167 µmol·g for HꢀMCMꢀ56 at 200 C, 152 µmol·g for HꢀMCMꢀ22,
ꢀ
1
ꢀ1
o
3
16 µmol·g for HꢀMCMꢀ49, and 134 µmol·g for HꢀMCMꢀ56 at 350 C. It is clearly seen that
there were more Lewis acid sites over HꢀMCMꢀ22 and HꢀMCMꢀ56, although the number of total
acid sites was similar to each other. However, HꢀMCMꢀ49 showed much more Br nsted acid sites
Ø
and less Lewis acid sites, which resulted in a much larger B/L ratio. The difference in acid sites
originated in their difference in structure.
Br nsted acid sites are usually regarded as active centers for the alkylation. More Brønsted
Ø
acid sites would be beneficial for the improvement of zeoliteꢀbased catalysts’ activity. However in
some cases, Lewis acid sites also contribute to catalytic performances either via synergistic effect
with Br
Ø
3
nsted acid sites or via direct conversion of reactants. In early time, AlCl has been proved
very active for the liquidꢀphase alkylation of benzene with ethylene. According to our previous
13

RSC Advances
Page 14 of 35
View Article Online
DOI: 10.1039/C5RA25503A
32,36,37
data,
we are anticipating that the HꢀMCMꢀ49 and HꢀMCMꢀ56 with more total amount of acid
sites would be positive to the alkylation performance.
Fig. 7 shows the FTꢀIR spectra of HꢀMCMꢀ22, HꢀMCMꢀ49, and HꢀMCMꢀ56 zeolites
before/after 2,4,6ꢀtrimethylꢀpyridine adsorption. There were similar bands for all three Hꢀtype
ꢀ1
zeolites: The bands ranging in 3740 ~ 3750 cm were assigned to terminal SiꢀOH groups on the
ꢀ1
surface of zeolites; the bands range in 3605 ~ 3665 cm were ascribed to acidic bridged hydroxyls,
which were located on the different inner pores (10 MR channels and 12 MR supercages via 10 MR
windows) of Hꢀtype zeolites. Clearly, there was no significant disappearance of bands at 3605 ~
ꢀ1
3
665 cm after 2,4,6ꢀtrimethylꢀpyridine adsorption, demonstrating that the acidic bridged hydroxyls
inside the pores (10 MR channels and 12 MR supercages via 10 MR windows) corresponding to the
ꢀ1
3
605 ~ 3665 cm bands could not be approached by 2,4,6ꢀtrimethylꢀpyridine due to its bulk
50
molecular sizes. According to other’s results, 2,4,6ꢀtrimethylꢀpyridine could only detect acid sites
47ꢀ49
residing in 12 MR cups on the external surface of MWW zeolites.
What’s more, Adsorbed
ꢀ1
species then led to two new obvious bands at 1650 and 1633 cm , assigned to 2,4,6ꢀtrimethylꢀ
pyridine adsorbed on Brønsted and Lewis acid sites on the external surface 12 MR cups,
5
0
respectively. The amount of 2,4,6ꢀtrimethylꢀpyridine was calculated by the height of adsorption
ꢀ1
ꢀ1
band (1633 cm ) to determine the accessibility of acid sites, 23.0 µmol·g for HꢀMCMꢀ22, 34.9
ꢀ1
ꢀ1
µmol·g for HꢀMCMꢀ49 and 39.5 µmol·g for HꢀMCMꢀ56. Also some reports have claimed that
active centers useful for EB synthesis were mainly located in 12 MR cups on the outer surface of
MWW zeolites, which do not restrict the diffusion of reactant/product toward/from the active
47ꢀ49
centers.
Therefore it is strongly emphasized that HꢀMCMꢀ56 with partially delaminated and a
disordered collection of MWW monolayers and larger external surface area represented more 12
MR cups and the better accessibility of active centers, which would contribute to the catalytic
performance.
3
.4 Alkylation performance over H-MWW catalysts
14

Page 15 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
As a typical consecutive reaction, liquidꢀphase alkylation of benzene with ethylene (scheme 1)
has been extensively studied on lab and industrial scale. Usually the ethylene conversion is almost
1
00 % to ensure that no ethylene enter transꢀalkylation reactor in industrial unit. If there was
unconverted ethylene, fast deactivation will happen on ethylation and transꢀalkylation catalysts.
Also with benzene/ethylene ratio at 12, which is similar to that of single ethylation stage with multiꢀ
ethylene feeding points, is enough to guarantee the solution of ethylene in the benzene. What’s
more, benzene/ethylene ratio at 12 indicates pseudo firstꢀorder reaction due to large excess of
benzene over ethylene. High conversion of ethylene led to dramatically decreased ethylene
concentration, which needs higher activity to convert ethylene at much lower concentration, ie
small vibration in ethylene conversion and EB selectivity could be obtained.
The HꢀMCMꢀ22 catalyst showed a stepwise increase of ethylene conversion from 89.8 % at
o
o
2
00 C to 96.6 % at 260 C in Fig. 8a, indicating that the diffusion limits may be one of the key
factors to the activity of HꢀMCMꢀ22. HꢀMCMꢀ49 exhibited higher ethylene conversion than Hꢀ
o
o
MCMꢀ22 from 96.7 % at 200 C to 99.2 % at 260 C. Ethylene conversion was not completely
o
achieved up to 100 % over HꢀMCMꢀ22 catalyst despite of the temperature at 260 C, so did Hꢀ
MCMꢀ49 with higher activity. The low alkylation activity over HꢀMCMꢀ22 and HꢀMCMꢀ49
catalysts might be related to its roseꢀlike shape, smaller external surface and poor accessibility of
active centers (less 12 MR cups exposed on the external surface) by 2,4,6ꢀtrimethylꢀpyridine. The
less the amount of 2,4,6ꢀtrimethylꢀpyridine adsorption, the lower ethylene conversion over Hꢀ
MCMꢀ22. For HꢀMCMꢀ22 and HꢀMCMꢀ49 with completed 3D structure, things became more
complicated due to three different pore systems. Although there were abundant active centers inside
the 10 MR channels, they seemed to contribute little to EB formation. Both benzene (kinetic
diameter 0.58 nm) and ethylene (kinetic diameter 0.39 nm) could penetrate the 10 MR channels,
however they contributed little to the formation of EB due to transitional state selectivity. As for 12
MR supercages with 10 MR windows, reactants could penetrate 12 MR supercages through 10 MR
windows, and 12 MR supercages were large enough to form the transitional state intermediate of
15

RSC Advances
Page 16 of 35
View Article Online
DOI: 10.1039/C5RA25503A
EB, but existing some diffusion restriction on reactants/products. It is proposed that poor diffusion
of reactants into 12 MR supercages through 10 MR windows was the key reason to the stepwise
increase of ethylene conversion over HꢀMCMꢀ22 and HꢀMCMꢀ49.
HꢀMCMꢀ56 represented higher ethylene conversion from 95.7 % to 99.9 % (the temperature
o
o
rise from 200 to 260 C) than those of HꢀMCMꢀ22 and HꢀMCMꢀ49 (except at 200 C). According
to the above characterized results for HꢀMCMꢀ56, partially delaminated and a disorderly packed
mono MWW layers could offer larger external surface areas, more acid sites and more opportunities
for reactants to access the active centers. As presented in Table 2, the external surface area and
2
ꢀ1
3
ꢀ1
volume of HꢀMCMꢀ56 was larger obviously, 145 m ·g and 0.79 cm ·g , which would offer more
active centers accessed by reactants with less diffusion restriction. Although there was varying
differences in the total acid sites for both HꢀMCMꢀ22, HꢀMCMꢀ49 and HꢀMCMꢀ56 by NH ꢀTPD
3
and PyꢀFTIR results, more acid sites accessed by 2,4,6ꢀtrimethylꢀpyridine were observed (39.5
ꢀ1
ꢀ1
ꢀ1
µmol·g ) than HꢀMCMꢀ22 (23.0 µmol·g ) and HꢀMCMꢀ49 (34.9 µmol·g ). All these factors
contributed to the alkylation performance for HꢀMCMꢀ56 catalyst. Additionally, there was also a
o
stepwise increase of ethylene conversion from 200 to 230 C, indicating that there was also
diffusion limits on ethylation of benzene but less restricted than that over HꢀMCMꢀ22 and HꢀMCMꢀ
4
9. On the other side, this result effectively supported that HꢀMCMꢀ56 without 12 MR supercages
through 10 MR windows in idealized conditions had more 12 MR cups on the external surface.
Similar to HꢀMCMꢀ22, no ethylation of benzene occurred in 10 MR channels of HꢀMCMꢀ56 due to
restriction of transitional state selectivity. Therefore the key of improving the ethylene conversion
lies in how to tailor the diffusion restriction of 12 MR supercages through 10 MR windows to form
more 12 MR cups exposed on the external surface of MWW zeolites, which led to a stepwise
increase of ethylene conversion. According to above results, synthesis of monoꢀlayered
(delaminated) MCMꢀ56 zeolite could increase the catalytic activity in liquidꢀphase alkylation of
benzene with ethylene over MWW catalysts.
16

Page 17 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
Low ethylene conversion over HꢀMCMꢀ22 usually has two potential meanings because of
consecutive reaction with intermediate product (EB) as the target product. One was that
o
o
corresponding EB selectivity was highest from 96.5 % at 200 C to 95.3 % at 260 C through the
calculation (Fig. 8b), the other meant less DEBs and TEBs produced over HꢀMCMꢀ22 in Fig. 8c
o
and 8d, especially no TEBs formation at temperature range from 200 to 220 C. Although improved
ethylene conversion was observed over HꢀMCMꢀ49, the EB selectivity decreased from 95.6 % at
o
o
2
00 C to 95.0 % at 260 C. For HꢀMCMꢀ56 with the best activity showed the lowest EB selectivity
o
o
from 95.1 % at 200 C to 94.1 % at 260 C and higher DEBs and TEBs formation than HꢀMCMꢀ22
and HꢀMCMꢀ49, evincing the higher activity and poorer EB selectivity over HꢀMCMꢀ56. As a
consecutive reaction of benzene with ethylene, generally improved ethylene conversion is
5
1,52
accompanied by decreased EB selectivity.
Therefore, it is carefully weighted and considered for
the tradeꢀoff between ethylene conversion and EB selectivity because of the intermediate EB as the
target product. In our future work, we will focus on tailoring the crystallinity and morphology of Hꢀ
MCMꢀ56 to improve the regular aggregation of MWW layers with partially delaminated and a
disorderly packed of mono MWW layers, which might be beneficial for the improvement of EB
selectivity. The most effective achievement for tailoring MWW zeolites would enhance the
ethylene conversion reaching up to 100 % without any loss of EB selectivity, or achieve the
enhancement of both the ethylene conversion and EB selectivity to break out the “seeꢀsaw” in the
consecutive reaction.
4
. Conclusion
MCMꢀ22, MCMꢀ49 and MCMꢀ56 were synthesized with HMI as the structureꢀdirecting agent
and aniline as the structureꢀpromoting agent. As structureꢀpromoting agent, aniline deceased
obviously the usage of HMI compared to conventional HMI route. Meanwhile it contributed to the
formation of MWW zeolites without being trapped within MWW zeolites. In other words, aniline
was useful during crystallization, however it was not consumed during the temperatureꢀcontrolled
phase transfer synthesis. With proper recycle techniques, the nonꢀconsumption of aniline could be
17

RSC Advances
Page 18 of 35
View Article Online
DOI: 10.1039/C5RA25503A
achieved. The key lies in the increasing solubility of aniline with temperature, which made process
featured by temperatureꢀcontrolled phase transfer hydrothermal synthesis. That is, most of HMI and
aniline could be recovered by phase separation after crystallization. As for MCMꢀ56, the first
monoꢀlayered (delaminated) zeolite obtained by direct synthesis, it remains the only one prepared
with simple templates. The problem of MCMꢀ56 synthesis lies in its intermediate nature and
conversion to MCMꢀ49 if not quenched at the right time. In this contribution, MCMꢀ56 with
partially delaminated and a disordered collection of MWW monolayers was synthesized in
HMI/AN, fumed SiO
phase in MCMꢀ56 synthesis process. The most important advance that the conversion from MCMꢀ
6 to MCMꢀ49 could be avoided even subject to much longer crystallization time. Hence we might
2 2 2
as silica source and high H O/SiO system. There was no other competing
5
provide a facile and reproducible method to generate MCMꢀ56 with less economical and
environmental impacts. Because of a partially delaminated and disordered collection of MWW
2
ꢀ1
monolayers, MCMꢀ56 showed larger external surface area (145 m ·g ) and pore volume (0.79
3
ꢀ1
cm ·g ), which would have less diffusion restriction of reactants to enhance its catalytic activity.
The acidity characterization results by different probe molecules indicate that MCMꢀ56 had better
accessibility of acid sites by 2,4,6ꢀtrimethylꢀpyridine, that is in accordance with the fact that Hꢀ
MCMꢀ56 possessed more 12 MR cups exposed on the external surface, resulting in higher ethylene
conversion in liquidꢀphase alkylation of benzene with ethylene.
References
1
2
3
. L. Puppe and J. Weisser, US 4,439,409, 1984.
. G. Bellussi, G. Perego, M. G. Clerici and A. Giusti, EP 293,032, 1988.
. S. I. Zones, D. I. Holtermann, R. A. Innes, T. A. Pecoraro, D. S. Santilli and J. N. Ziemer. US
4
,826,667, 1989.
4
5
. M. K. Rubin and P. Chu, US 4,954,325, 1990.
. J. M. Bennett, C. D. Chang, S. T. Lawton, M. E. Leonowicz, D. N. Lissy and M. K. Rubin, US
5
,236,575, 1993.
18

Page 19 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
6
7
8
9
. A. S. Fung, S. T. Lawton and W. J. Roth, US 5,362,697, 1994.
. C.TꢀW. Chu, C. T. Kresge, W. J. Roth, K. G. Simmons, and J. C. Vartuli, US 5,292,698, 1994.
. M. J. D. Cabañas, M. A. C. Fernandez, C. C. Martires and A. C. Canos, US 6,077,498, 2000.
. P. J. V. D. Brink, A. C. Camos, E. J. Creyghton, V. F. Segui and V. M. Soria, US 6,855,855,
2
005.
1
0. L. M. Rohde, G. J. Lewis, M. A. Miller, J. G. Moscoso, J. L. Gisselquist, R. L. Patton, S. T.
Wilson and D. Y. Jan, US 6,756,030 B1, 2004.
1
1
1
1. W. J. Roth, Stud. Surf. Sci. Catal., 2005, 158, 19ꢀ26.
2. M. E. Leonowicz, J. A. Lawton, S. L. Lawton and M. K. Rubin, Science, 1994, 264, 1910ꢀ1913.
3. S. L. Lawton, A. S. Fung, G. J. Kennedy, L. B. Alemany, C. D. Chang, G. H. Hatzikos, D. N.
Lissy, M. K. Rubin, H. C. Timken, S. Steuernagel and D. E. Woessner, J. Phys. Chem., 1996,
1
00, 3788ꢀ3798.
4. W. J. Roth, J. Čejka, R. Millini, E. Montanari, B. Gil and M. Kubu. Chem. Mater., 2015, 27,
620ꢀ4629.
1
1
4
rd
5. W. J. Roth. Introduction to Zeolite Science and Practiceꢀ3 Revised Edition, Chapter 7, 2007.
Published by Elsevier B.V.
1
1
1
1
6. W. J. Roth, P. Nachtigall, R. E. Morris and J. Cejka, Chem. Rev., 2014, 114, 4807ꢀ4837.
7. W. J. Roth and J. Cejka, Catal. Sci. Technol., 2011, 1, 43ꢀ53.
8. W. J. Roth and D. L. Doreset, Micropor.Mesopor. Mat., 2011, 142, 32ꢀ36.
9. B. Gil, W. J. Roth, W. Makowski, B. Marszalek, D. Majda, Z. Olejniczak and P. Michorczyk,
catal. today, 2015, 243, 39ꢀ45.
2
2
0. B. Gil, W. Makowski, B. Marszalek, W. J. Roth, M. Kubu, J. Cejka and Z. Olejniczak, Dalton.
Trans., 2014, 43, 10501ꢀ10511.
1. W. Makowski, K. Mlekodaj, B. Gil, W. J. Roth, B. Marszalek, M. Kubu, P. Hudec, A.
Smieskova and M. Hornacek, Dalton. Trans., 2014, 43, 10574ꢀ10584.
19

RSC Advances
Page 20 of 35
View Article Online
DOI: 10.1039/C5RA25503A
2
2. M. Polozij, H. V. Thang, M. Rubes, P. Eliasova, J. Cejka and P. Nachtigall, Dalton. Trans.,
014, 43, 10443ꢀ10450.
2
2
2
2
2
2
3. G. G. Juttu and R. F. Lobo, Micropor.Mesopor. Mat., 2000, 40, 9ꢀ23.
4. W. J. Roth, P. Chlubna, M. Kubu and D. Vitvarova, Catal. today, 2013, 204, 8ꢀ14.
5. J. Shin and S. B. Hong. Micropor. Mesopor. Mat., 2009, 124, 227ꢀ231.
6. W. J. Roth, D. L. Dorset and G. J. Kennedy. Micropor. Mesopor. Mat., 2011, 142, 168ꢀ177.
7. H. Y. Luo, V. K. Michaelis, S. Hodges, R. G. Griffin and Y. RománꢀLeshkov. Chem. Sci., 2015,
6
, 6320ꢀ6324.
2
2
3
3
3
3
3
3
3
8. M. Kubů, W. J. Roth, H. F. Greer, W. Z. Zhou, R. E. Morris, J. Přech and J. Čejka. Chem. Eur.
J., 2013, 19, 13937ꢀ13945.
9. S. Goergen, E. Fayad, S. Laforge, P. Magnoux, L. Rouleau and J. Patarin. J. Porous. Mater.,
2
011, 18, 639ꢀ650.
0. E. H. Xing, X. Z. Gao, W. H. Xie, F. M. Zhang, X. H. Mu and X. T. Shu, RSC Adv., 2014, 4,
4893ꢀ24899.
1. E. H. Xing, Y. C. Shi, W. H. Xie, F. M. Zhang, X. H. Mu and X. T. Shu, RSC Adv., 2015, 5,
514ꢀ8522.
2
8
2. Y. C. Shi, E. H. Xing, W. H. Xie, F. M. Zhang, X. H. Mu and X. T. Shu, Micropor. Mesopor.
Mat., 2015, 215, 8ꢀ19.
3. H. Stephen and T. Stephen. Solubilities of inorganic and organic compounds, Macmillan, New
York, vol. 1, 1963.
4. Y. C. Shi, E. H. Xing, W. H. Xie, F. M. Zhang, X. H. Mu and X. T. Shu, RSC Adv., 2015, 5,
1
3420ꢀ13429
5. E. H. Xing, Y. C. Shi, A. G. Zheng, J. Zhang, X. Z. Gao, D. Y. Liu, M. D. Xin, W. H. Xie, F. M.
Zhang, X. H. Mu and X. T. Shu, Ind. Eng. Chem. Rec., 2015, 54, 3223ꢀ3135.
6. Y. C. Shi, E. H. Xing, W. H. Xie, F. M. Zhang, X. H. Mu and X. T. Shu, Appl. Catal. A: Gen.,
2
015, 497, 135ꢀ144.
20

Page 21 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
3
7. Y. C. Shi, E. H. Xing, W. H. Xie, F. M. Zhang, X. H. Mu and X. T. Shu, Micropor. Mesopor.
Mat., 2016, 220, 7ꢀ15.
38. S. H. Cha, J. Lee, J. Shin and S. B. Hong. Top. Catal., 2015, 58, 537ꢀ544.
39. J. D. Kushnerick, D. O. Marler, J. P. Mcwilliams and C. M. Smith, US 4,992,606, 1991.
40. A. Corma, V. Martı′nezꢀSoria and E. Schnoeveld, J. Catal., 2000, 192, 163–173.
41. J. Shi, Y. D. Yang, W. M. Yang, Y. Tang and Z. K. Xie, Chem. Soc. Rev., 2015,
DOI:10.1039/c5cs00626k
4
2. A. L. S. Marques, J. L. F. Monteiro and H. O. Pastore, Micropor. Mesopor. Mater., 1999, 32,
1
31ꢀ145.
4
3. D. Vuono, L. Pasqua, F. Testa, R. Aiello, A. Fonseca, T.I. Koranyi and J.B. Nagy. Micropor.
Mesopor. Mater., 2006, 97, 78ꢀ87.
44. G. J. Kennedy, S. L. Lawton and M. K. Rubin, J. Am. Chem. Soc., 1994, 116, 11000ꢀ11003.
45. G. J. Kennedy and S. L. Lawton, Microporous Mater., 1997, 9, 209ꢀ212.
46. M. J. Cheng, D. L. Tan, X. M. Liu, X. W. Han, X. H. Bao and L. W. Lin, Micropor. Mesopor.
Mater., 2001, 42, 307ꢀ316.
4
7. J. Cheng, T. Degnan, J. Beck, Y. Huang, M. Kalyanaraman, J. Kowalski, C. Loehr and D.
Mazzone, Stud. Surf. Sci. Catal., 1999, 121, 53ꢀ60.
4
8. H. Du and D. H. Olson. J. Phys. Chem. B., 2001, 106, 395ꢀ400.
9. P. Ayrault, J. Datka, S. Laforge, D. Martin and M. Guisnet, J. Phys. Chem. B., 2014, 108,
4
1
3755ꢀ13763.
5
5
5
0. F. ThibaultꢀStarzyk, A. Vimont and J. Gilson. Catal. Today, 2001, 70, 227ꢀ241.
1. J. G. van de Vusse, Chem. Eng. Sci., 1966, 21, 1239ꢀ1252.
2. L. D. Schemidt, The Engineering of Chemical Reactions. New York, Oxford University Press,
1
998, pp 157ꢀ168.
21

RSC Advances
Page 22 of 35
View Article Online
DOI: 10.1039/C5RA25503A
Figure captions:
Fig. 1 XRD patterns of MCM-22 (a, 72 h), MCM-49 (b, 72 h), MCM-56 (c, 72 h) and MCM-56 (d,
68 h) zeolites before and after calcination
1
1
3
13
Fig. 2 C CP/MAS NMR spectra of as-synthesized MWW zeolites (a) and liquid C NMR
spectra of as-synthesized MWW zeolites collapsed by HF (b)
Fig. 3 SEM image of H-MCM-22 (a), H-MCM-49 (b), and H-MCM-56 (c) zeolites
Fig. 4 Nitrogen isotherms of H-MCM-22, H-MCM-49, and H-MCM-56 zeolites
2
9
27
Fig. 5 Si/ Al MAS NMR spectra of as-synthesized samples and H-type zeolites
Fig. 6 NH -TPD curves of H-MCM-22, H-MCM-49, and H-MCM-56 zeolites
3
Fig. 7 2,4,6-trimethylpyridine spectra of H-type zeolites (a: H-MCM-22; b: H-MCM-49; c:
H-MCM-56)
Fig. 8 Ethylene conversion (%, a), EB selectivity (%, b), DEB selectivity (%, c) and TEB
selectivity (%, d) over H-type catalysts (Liquid-phase alkylation conditions: 8 mL catalysts, T =
o
o
-1
-1
2
00 C to 260 C, p = 3.5 MPa, benzene WHSV = 3.0 h , benzene/ethylene molar ratio = 12.0)
Scheme 1 reaction scheme of liquid-phase alkylation of benzene with ethylene
Table 1 Synthesis conditions of MWW zeolites
Table 2 Textural properties of H-type zeolites
Table 3 Acid properties of H-type zeolites
2
2

Page 23 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
b
a
H-MCM-22
H-MCM-49
as-synthesized
MCM-22
as-synthesized
MCM-49
5
10
15
20
25
30
35
5
10
15
20
25
30
35
o
o
2
Theta ( )
2 Theta ( )
d
c
Calcined MCM-56
168 h)
H-MCM-56
(
as-synthesized
MCM-56 (168 h)
as-synthesized
MCM-56
5
10
15
20
25
30
35
5
10
15
20
25
30
35
o
o
2
Theta ( )
2
Theta ( )
Fig. 1 XRD patterns of MCM-22 (a, 72 h), MCM-49 (b, 72 h), MCM-56 (c, 72 h) and MCM-56 (d,
68 h) zeolites before and after calcination
1
2
3

RSC Advances
Page 24 of 35
View Article Online
DOI: 10.1039/C5RA25503A
a
as-synthesized MCM-56
as-synthesized MCM-49
as-synthesized MCM-22 C2C3
C1
C1
200
150
100
50
0
-50
-100
Chemical shift (ppm)
C3
b
as-synthesized MCM-56
as-synthesized MCM-49
as-synthesized MCM-22
C2
C1
120
100
80
60
40
20
0
Chemical shift (ppm)
13
13
Fig. 2 C CP/MAS NMR spectra of as-synthesized MWW zeolites (a) and liquid C NMR
spectra of as-synthesized MWW zeolites collapsed by HF (b)
2
4

Page 25 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
aꢀHꢀMCMꢀ22
bꢀHꢀMCMꢀ49
cꢀHꢀMCMꢀ56
Fig. 3 SEM image of H-MCM-22 (a), H-MCM-49 (b), and H-MCM-56 (c) zeolites
2
5

RSC Advances
Page 26 of 35
View Article Online
DOI: 10.1039/C5RA25503A
500
400
300
200
100
0
H-MCM-56
H-MCM-49
H-MCM-22
0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (p/p0)
Fig. 4 Nitrogen isotherms of H-MCM-22, H-MCM-49, and H-MCM-56 zeolites
2
6

Page 27 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
29
29
Si MAS NMR
as-synthesized MCM-56
as-synthesized MCM-49
as-synthesized MCM-22
Si MAS NMR
H-MCM-56
H-MCM-49
H-MCM-22
-90
-100
-110
-120
-130
-140
-90
-100
-110
-120
-130
-140
Chemical shift (ppm)
Chemical shift (ppm)
27
27
Al MAS NMR
as-synthesized MCM-56
as-synthesized MCM-49
as synthesized MCM-22
Al MAS NMR
H-MCM-56
H-MCM-49
H-MCM-22
80
60
40
20
0
-20
80
60
40
20
0
-20
Chemical shift (ppm)
Chemical shift (ppm)
29
27
Fig. 5 Si/ Al MAS NMR spectra of as-synthesized samples and H-type zeolites
2
7

RSC Advances
Page 28 of 35
View Article Online
DOI: 10.1039/C5RA25503A
H-MCM-56
H-MCM-49
H-MCM-22
100
200
300
400
500
600
o
Temperature ( C)
Fig. 6 NH -TPD curves of H-MCM-22, H-MCM-49, and H-MCM-56 zeolites
3
2
8

Page 29 of 35
RSC Advances
View Article Online
DOI: 10.1039/C5RA25503A
a
Hydroxyl (-OH)
,4,6-trimethylpyridine
2
0.2 abs.u
3800 3600 3400 3200 3000 1700
1600
1500
1400
ꢀ1
Wavenumber (cm )
b
0.2 abs.u
Hydroxyl (-OH)
,4,6-trimethylpyridine
2
3800 3600 3400 3200 3000
1700
1600
1500
1400
ꢀ1
Wavenumber (cm )
c
Hydroxyl (-OH)
,4,6-tromethylpyridine
0.2 abs.u
2
3800 3600 3400 3200 3000
1700
1600
1500
1400
ꢀ
1
Wavenumber (cm )
Fig. 7 2,4,6-trimethylpyridine spectra of H-type zeolites (a: H-MCM-22; b: H-MCM-49; c:
H-MCM-56)
2
9