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CATTOD-9816; No. of Pages8
ARTICLE IN PRESS
S. Jiang et al. / Catalysis Today xxx (2015) xxx–xxx
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than that of other solid acid catalysts. Deng et al. [15] investigated
three kinds of MOF catalysts’ (Hpd@ZnPC-2, ZnPC-2, CoZnPC-2) cat-
alytic performance in Friedel–Crafts benzylation of toluene with
from literature [23]. Firstly, as-synthesized SiO @Fe O particles
2 3 4
were dispersed into the mixture solution of Al(NO ) ·9H O, 1,4-
3
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2
benzenedicarboxylic acid (H BDC) and deionized water under
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-chlorobenzyl bromide, showing a high selectivity (>90%) because
ultrasound for a certain time. Subsequently, the mixture was
placed in a 75 mL Teflon-lined steel autoclave and heated at
493 K for 72 h. After completion of reaction, the autoclave was
cooled down to room temperature and the formed brown powder
was separated by an external magnet and washed with dis-
tilled water (4 × 50 mL) until pH of filtrate was 7. The powder
obtained was dried for 12 h at 353 K in air. Then as-synthesized
samples were extracted by N,N-dimethylformamide (DMF) for
of its adaptable pore size. With the isoreticular frameworks of
Hpd@ZnPC-2 and CoZnPC-2, it was proved that the catalytic reac-
tion occurs inside the pores of ZnPC-2 and the catalytic active
sites are the Zn -SBUs. Calleja et al. [16] evaluated MOF-74 in
3
Friedel–Crafts acylation reaction of anisole with acetyl chloride.
The results showed that both the conversion of benzene methyl
and the selectivity of product p-MAP can reach a high rate, and
the catalysts also had good recycling performance and reusability.
Nguyen et al. [17] used IRMOF-8 to catalyze Friedel–Crafts acylation
reactions of toluene with benzoyl chloride, and the conversion of
toluene was about 95%. Phan et al. [18] used MOF-5 to catalyze the
Friedel–Crafts alkylation reaction of toluene with benzyl bromide,
and had obtained promising results. The metal organic frameworks,
we used in this work, MIL-53(Al) are three dimensional frameworks
by infinite chains of corner sharing Al (OH) octahedra, intercon-
nected by benzenedicarboxylate (BDC) units. The chemical formula
is given by Al(OH)(O C-C H -CO ). MIL-53(Al) drew much atten-
tion due to its simple structure and outstanding thermal stability
compared to other MOFs. The remarkable thermal stability up to
5
12 h to remove unreacted H BDC and washed by methanol for
2
three times. At last the powder was dried under vacuum for
2 h at 353 K. In these MIL-53(Al)@SiO @Fe O catalysts, the MIL-
2
3
4
53(Al) weight percentage content was determined by the amount
of Al(NO ) ·9H O as well as of 1,4-benzenedicarboxylic acid
3
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2
(H BDC).
2
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2.2. Characterization
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2
The X-ray diffraction (XRD) patterns were recorded using
a Rigaku D/MAX 2500 VB 2+/PC diffractometer with Cu K␣
irradiation(ꢀ = 1.5418 A˚ ) at 200 kV and 50 mA in the range of 2Â
◦
00 C makes MIL-53(Al) materials possible for industrial applica-
◦
◦
value between 5 and 70 . Transmission electron microscopy
TEM) observation was performed on a JEOL (JEM 2100) trans-
tion.
The combination of magnetism to the usual routes of catalyst
(
mission emission microscope operated at a 200 kV accelerating
voltage. Scanning electron microscope (SEM) images of sam-
ples were obtained from a Zeiss SUPRA55 instrument operated
design has always been an important method for the prepara-
tion and the study of the performance of the catalysts. With
the use of additional external magnet, superparamagnetism cat-
alysts in the solid–liquid phase reaction can be easily separated
from the liquid system, which greatly simplifies the operation
and avoids the loss of the catalysts. Ji et al. [19] had success-
at
a 20 kV accelerating voltage. Fourier transform infrared
spectroscopy (FT-IR) was carried out on a Bruker Tensor-27
Fourier transform infrared spectroscope using KBr pellet sam-
ples. The N2 adsorption–desorption measurement of the samples
was detected on an ASAP 2020 M automatic specific surface
fully synthesized supported magnetic Cu/Fe O @SiO catalysts,
3
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2
which can effectively convert the low concentration formalde-
hyde into hydrogen at room temperature. It was observed that
after recycling for 8 times, the catalytic activity of the catalyst
has not obviously decreased. Li et al. [20] prepared a novel mag-
netic Cu-BTC@SiO @Fe O catalyst and applied into Pechmann
area and aperture analyzer. The samples were pretreated at
◦
1
50 C for 5 h under vacuum and surface area was calcu-
lated by the BET equation, while pore size distribution was
obtained using the BJH method. Magnetic properties of the
samples were measured using vibration sample magnetometer
2
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reaction, and the conversion of 1-naphthol could reach ∼96% and
(VSM; Lake Shore Model 7400) under magnetic fields up to
the selectivity of the production could reach ∼98% under reac-
2
0 kOe.
◦
tion conditions of 130 C for 24 h. After reaction, the catalyst
can be easily separated from the reaction mixture by an exter-
nal magnet. The recovery catalyst can be reused for five times
and the conversion of 1-naphthol can be kept over 90% for each
time.
2.3. Catalytic activity evaluations
Friedel–Crafts acylation reaction of 2-methylindole with ben-
zoyl chloride was carried out in a flask reactor with a condenser. A
certain amount of 2-methylindole, benzoyl chloride, n-dodecane,
dichloromethane and the catalysts (the content of the catalyst was
In this work, MIL-53(Al)@SiO @Fe O catalyst was synthe-
2
3
4
sized by encapsulating of MIL-53(Al) on the surface of magnetic
SiO @Fe O particles in situ method for the first time. Then the
2
3
4
structure and properties of the catalysts were characterized by
XRD, TEM, SEM, FT-IR, N2 adsorption/desorption and VSM mea-
surement techniques. The catalytic activity, magnetic recycling and
reusability of the catalysts for the Friedel–Crafts acylation reac-
tion of 2-methylindole with benzoyl chloride were evaluated under
different reaction conditions.
used in reference to the molar ratio of 2-methylindole, n1:ncatalyst)
were added in the flask with magnetic stirring. After reaction, the
catalysts were separated from the solvent by an external magnet.
The above layer of liquid was detected through GC (Beijing Beifen-
Ruili Analytical Instrument (Group) Co. Ltd, SP-2100, HJ.PONA,
50 m × 0.20 mm × 0.50 m). The conversion of 2-methylindole (X),
the selectivity (S ) and the yield (Y ) of 3-acetylindole, the selec-
3
3
tivity (S ) and the yield (Y ) of N-acetylindole were all calculated
4
4
2
. Experiment
with n-dodecane as an internal standard. After pouring the liquid
from the flask, the solid catalyst was washed with dichloromethane
and separated by an external magnet. Then the fresh reagents were
added to the flask reactor and used for the next run. In order to
study the effect of different indole derivatives on the Friedel–Crafts
acylation reaction, different substrates (indole with different sub-
stituent groups, such as, H, CH3, 5-OCH3, 6-NO2) were used
reaction.
2.1. Catalysts preparation
The magnetic SiO @Fe O particles were synthesized accord-
2
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4
ing to a literature procedure [21,22]. Fe O4 was synthesized by a
solvothermal method, and the SiO2 shell, which can protect the
Fe O against eroding of the solvent in the reaction process, was
coated by the hydrolysis of tetraethoxysilane (TEOS). The synthe-
sis procedure of MIL-53(Al)@SiO @Fe O was slightly modified
3
3
4
2
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Please cite this article in press as: S. Jiang, et al., Preparation of magnetically recyclable MIL-53(Al)@SiO @Fe O catalysts and their
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