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The resulting nanoparticles were separated by magnetism and
washed with distilled water three times.
perimental results, SZTF showed an excellent catalytic activity
and it increased the surface area of SO42ꢀ/ZrO2 by up to 15%.
The increase not only promoted the generation of NO2+, but
also provided more opportunities for the metal ion to interact
with aromatic compounds. In particular, Fe3O4 did not only im-
prove the catalytic effect but also endowed the solid acid with
magnetic properties with which an easy separation process
was achieved. Also, by using the nitration of chlorobenzene as
an example, theoretical research on the geometric parameters,
the electron clouds, and electron spin density was carried out
to investigate the interaction between transition metals and
chlorobenzene. As shown in the theoretical results, most
changes of the electron spin density in the benzene ring
matched well with the selectivity obtained from experiments.
Based on these studies, some key factors were found to have
a great effect on the selectivity of nitration products. By pre-
dicting these factors with quantum calculations, it would be
very easy and convenient to screen catalysts containing differ-
ent metals for nitration before complicated chemical experi-
ments.
Preparation of nanosized SZTF(1:1): ZrOCl2 (3.22 g, 0.01 mol) was
dissolved in distilled water (50 mL) to prepare a solution of 6%
concentration. TiCl4 (1.89 g, 0.01 mol) was diluted with distilled
water until no smoke appeared or was added dropwise into dis-
tilled water (50 mL). Nanosized Fe3O4 (0.1 g) was added to distilled
water (20 mL) and was treated with ultrasonic waves for 1 h to
form a stable suspension. Then these three solutions were mixed
and stirred vigorously. Aqueous ammonia solution was added
dropwise to the mixture to make the pH 9.0–10.0. The whole mix-
ture was aged for 24 h and then separated by magnetism. The
solid was washed with distilled water until no Clꢀ could be detect-
ed. This solid was then dried at 1108C for 24 h and was ground if
there was bulky grain in it. Then the solid was impregnated with
(NH4)2SO4 (0.5 molLꢀ1) for 2 h, and was separated and dried at
110 8C for 24 h. Finally, this solid was calcinated at 5508C for 3 h
under vacuum conditions. If it was calcined under air with electric
muffle furnace, this solid must be covered with a thick layer of
quartz sand. It was red after being calcinated in the electric muffle
furnace, but no obvious loss of catalytic activity and magnetism
was seen by experiment.
Preparations of other solid acids were similar to SZTF(1:1) and the
detailed operations are given in the Supporting Information
Experimental Section
All chemicals were purchased from Sinopharm Chemical Reagent
Co. Ltd. and were used without further purification. Their composi-
tions were confirmed by using GC or LC analysis (comparison with
an authentic sample). GC analysis was performed on an Agilent
GC-6820 instrument equipped with a 30 mꢂ0.32 mmꢂ0.5 mm HP-
Innowax capillary column and a flame ionization detector. LC anal-
ysis was performed on a Shimadzu LC-20 instrument equipped
with a SPA-20 UV-detector, and a mixture of methanol and water
was used as the mobile phase. XRD data were collected with CuKa
radiation on a Bruker D8 ADVANCE instrument scanning from 20
to 808. FTIR spectra were recorded on a Bruker Vietor22 spectrom-
eter. SEM images were recorded on a JEOLJSM-6380LV instrument.
BET surface areas were recorded on a Quantachrome NOVA1000 in-
strument with the N2 adsorption method. XRF was recorded on
a ARL-9800 instrument (Switzerland ARL Corp.).
Synthesis and characterization
General procedure: In a typical reaction protocol, CCl4 (3 mL),
(Ac)2O (1 mL), chlorobenzene (1 mL), and a certain amount of cata-
lyst were stirred in a three-necked round-bottomed flask. Then
HNO3 (1 mL, 95%) was added in the mixture dropwise to ensure
there was a slight change in temperature. Afterwards, this solution
was heated to the predefined temperature and stirring was contin-
ued for 1.5 h. When this reaction finished, the organic phase was
separated and was then washed once with 10mol% sodium bicar-
bonate solution (50 mL) and twice with distilled water (50 mL) to
make the pHꢁ7.0. After it was dried over magnesium sulfate, the
organic phase was analyzed to confirm the composition based on
GC or LC analysis (comparison with an authentic sample).
Geometric parameters were simulated by Gaussian 03 based on
the UAM1 method; the convergence criteria were set as 10–6. By
varying the position of the transition metal and chlorobenzene,
the convergence was realized with the model we used. Based on
the model, we changed the distance between the transition metal
and chlorobenzene and evaluated their energies. A stable point
with the lowest energy was the optimized structure. Charge distri-
bution and electron spin density (ESD) were then calculated for
these structures. The detailed geometric parameters can be found
in the Supporting Information.
Acknowledgements
We thank the NSAF and NSFC (no. 11076017) of China and the
Scientific Innovation Program of Jiangsu Province (no. CXZZ11_
0264) for support of this research. We also thank Prof. Chun Xu
Lv for his expertise in theoretical studies and for supplying some
materials on quantum chemistry.
Keywords: aromatic nitration · density functional calculations ·
regioselectivity · superacidic systems · transition metals
Catalysts preparation
[1] a) G. A. Olah, R. Malhotra, S. C. Narang, Nitration Methods and Mecha-
nism, VCH, New York, 1989; b) K. Sehofield, Aromatic Nitration, Cam-
bridge University Press, Cambridge (United Kingdom), 1980.
175, 209–213; b) F. J. Waller, A. G. M. Barrett, D. C. Braddock, D. Rampra-
Preparation of nanosized Fe3O4: The nanoparticles were prepared
according to published procedures[18] with some modifications. In
a typical run, FeCl2·4H2O (1.99 g, 10.0 mmol) and FeCl3 (3.25 g,
20.0 mmol) were dissolved in 10 and 20 mL of water, respectively.
The two iron salt solutions were combined and dropped into 0.6m
aqueous ammonia solution (200 mL) in 20 min with vigorous stir-
ring. The pH of the reaction mixture was kept in the range of 10 to
11 with the addition of concentrated aqueous ammonia solution.
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ChemPlusChem 2013, 78, 310 – 317 316