a
3 4
Table 3 Solvent-free hydrogenation of o-CNB, m-CNB and o-BNB over the Pt/Fe O catalyst
Selectivity (mol%)
Haloaniline
b
Substrate
Reaction time (min)
Reaction rate
Conversion of substrate (%)
AN
Others
o-CNB
m-CNB
o-BNB
75
80
85
2.2
2.1
2.0
100
100
100
99.3
99.5
99.1
0.6
0.4
0.9
Trace
Trace
Trace
a
b
(Pt: 1.0 wt%); substrate, 0.62 mol; temperature, 333 K; hydrogen pressure, 2.0 MPa. Average
Reaction condition: catalyst, 1.2 g Pt/Fe
O
3 4
À1 À1
hydrogenation rate of substrate (molsubstrate molPt
s ).
the catalyst was separated from the reaction products by an
applied magnetic field, washed with methanol and reused in
the next cycle. The catalytic properties of the recycled cata-
lysts, with a turnover number (TON) of 10 000 for each run,
are list in Table 2, which indicate the good stability of the
present catalyst under the reaction conditions. Metal species
dissolved in the products of the first test were measured by
inductively coupled plasma atomic emission spectrometry
J. M. Zheng, J. Colloid Interface Sci., 1999, 214, 231; B. Coq,
A. Tijani and F. Figueras, J. Mol. Catal., 1991, 68, 331;
V. Pandarus, R. Ciriminna, F. Beland and M. Pagliaro, Adv.
Synth. Catal., 2011, 353, 1306.
S. R. Boothroyd and M. A. Kerr, Tetrahedron Lett., 1995,
36, 2411; G. Wienhofer, I. Sorribes, A. Boddien, F. Westerhaus,
K. Junge, H. Junge, R. Llusar and M. Beller, J. Am. Chem. Soc.,
011, 133, 12875; M. Pietrowski, Green Chem., 2011, 13, 1633.
J. R. Kosak, in Catalysis in Organic Syntheses, ed. W. H. Jones,
Academic Press, New York, 1980, pp. 107–117.
B. J. Zuo, Y. Wang, Q. L. Wang, J. L. Zhang, N. Z. Wu,
L. D. Peng, L. L. Gui, X. D. Wang, R. M. Wang and D. P. Yu,
J. Catal., 2004, 222, 493.
´
´
3
¨
2
4
5
(ICP-AES, see ESIw). In the oil phase of the products, the
concentration of platinum was less than the detection limit of
1
4 ppb, whilst that of iron was 0.83 ppm. The aqueous phase
À1
6
7
8
´
M. Pietrowski, M. Zielinski and M. Wojciechowska, Catal. Lett.,
2009, 128, 31.
of the products contained 0.95 ppm of platinum and 1.0 mg ml
of iron. We believe that the corrosion of Fe
G. Y. Fan, L. Zhang, H. Y. Fu, M. L. Yuan, R. X. Li, H. Chen
and X. J. Li, Catal. Commun., 2010, 11, 451.
Y. Y. Chen, C. Wang, H. Y. Liu, J. S. Qiu and X. H. Bao, Chem.
Commun., 2005, 5298; Y. Y. Chen, J. S. Qiu, X. K. Wang and
J. H. Xiu, J. Catal., 2006, 242, 227.
3
O
4
in the catalyst,
due to the formation of a small amount of HCl, is responsible
for the metal leaching.
In order to investigate the universal significance of Pt/Fe O
3
4
9
J. L. Zhang, Y. Wang, H. Ji, Y. G. Wei, N. Z. Wu, B. J. Zuo and
Q. L. Wang, J. Catal., 2005, 229, 114; X. D. Wang, M. H. Liang,
H. Q. Liu and Y. Wang, J. Mol. Catal. A: Chem., 2007, 273, 160;
M. H. Liang, X. D. Wang, H. Q. Liu, H. C. Liu and Y. Wang,
J. Catal., 2008, 255, 335.
0 D. Q. Xu, Z. Y. Hu, W. W. Li, S. P. Luo and Z. Y. Xu, J. Mol.
Catal. A: Chem., 2005, 235, 137; C. X. Xiao, H. Z. Wang,
X. D. Mu and Y. Kou, J. Catal., 2007, 250, 25; S. Ichikawa,
M. Tada, Y. Iwasawa and T. Ikariya, Chem. Commun., 2005, 924;
C. Y. Xi, H. Y. Cheng, J. M. Hao, S. X. Cai and F. Y. Zhao,
J. Mol. Catal. A: Chem., 2008, 282, 80; X. C. Meng, H. Y. Cheng,
S. Fujita, Y. F. Hao, Y. J. Shang, Y. C. Yu, S. X. Cai, F. Y. Zhao
and M. Arai, J. Catal., 2010, 269, 131.
for the solvent-free selective hydrogenation of halonitrobenzenes,
the catalytic properties for the solvent-free hydrogenation of
m-CNB and o-bromonitrobenzene (o-BNB) over Pt/Fe
3
O
4
were
for
evaluated. Table 3 lists the catalytic properties over Pt/Fe
3
O
4
1
the solvent-free selective hydrogenation of m-CNB, o-CNB and
o-BNB at 333 K which is about 15 K higher than the melting
point of m-CNB and o-BNB. Under such conditions, the
selectivity to m-CAN, o-CAN and o-bromoaniline (o-BAN)
reached 99.5%, 99.3%, and 99.1%, respectively.
In conclusion, the prepared Pt/Fe O catalyst is a robust
4
3
1
1 F. Ca
Catal., A, 2008, 334, 199; F. Ca
and M. A. Keane, Catal. Commun., 2008, 9, 475; F. Ca
Lizana, S. Gomez-Quero and M. A. Keane, ChemSusChem, 2008,
1, 215; F. Cardenas-Lizana, S. Gomez-Quero, A. Hugon,
L. Delannoy, C. Louis and M. A. Keane, J. Catal., 2009,
62, 235; F. Cardenas-Lizana, Z. M. de Pedro, S. Gomez-Quero
and M. A. Keane, J. Mol. Catal. A: Chem., 2010, 326, 48.
´
rdenas-Lizana, S. Go
´
mez-Quero and M. A. Keane, Appl.
rdenas-Lizana, S. Gomez-Quero
rdenas-
catalyst for the selective hydrogenation of liquid o-CNB to
o-CAN in the absence of solvent. The yields of o-CAN reached
´
´
´
9
9.4% and the hydrodechlorination of o-CAN over this
´
catalyst was completely suppressed at complete conversion
´
´
of o-CNB. m-CAN and o-BAN were synthesized with yields of
2
´
´
9
9.5% and 99.1%, respectively, by the hydrogenation of
melted m-CNB and o-BNB, implying the universal significance
of Pt/Fe for the solvent-free selective hydrogenation of
12 J. Li, X. Y. Shi, Y. Y. Bi, J. F. Wei and Z. G. Chen, ACS Catal.,
2011, 1, 657.
3 Z. Y. Sun, H. Y. Zhang, G. M. An, G. Y. Yang and Z. M. Liu,
J. Mater. Chem., 2010, 20, 1947.
4 Y. Wang, J. W. Ren, K. Deng, L. L. Gui and Y. Q. Tang, Chem.
Mater., 2000, 12, 1622; B. L. He, Y. X. Chen, H. F. Liu and Y. Liu,
J. Nanosci. Nanotechnol., 2005, 5, 266; Y. Wang and X. D. Wang,
in Metal Nanoclusters in Catalysis and Materials Science: the Issue
of Size Control, ed. B. Corain, G. Schmid and N. Toshima,
Elsevier, Amsterdam, 2008, ch. 19, pp. 332.
3 4
O
1
halonitrobenzenes to corresponding haloanilines. The highly
efficient synthesis and separation processes of aromatic halo-
amines based on the present catalytic system are promising for
industrial application in an environment-friendly manner.
The authors express their thanks for the joint support from
the NSFC (project nos.: 20973003, 50821061, 21073002,
1
2
1133001), the NKBRSF (2011CB808702), and from the
15 L. S. Zhong, J. S. Hu, H. P. Liang, A. M. Cao, W. G. Song and
L. J. Wan, Adv. Mater., 2006, 18, 2426.
Chinese Ministry of Science and Technology.
1
1
6 Magnetite, Joint Committee on Powder Diffraction Standards
9-0629.
1
7 G. Vitulli, E. Pitzalis, A. Verrazzani, P. Pertici, P. Salvadori and
G. Martra, Mater. Sci. Forum, 1997, 235–238, 929; G. Vitulli,
A. Verrazzani, E. Pitzalis, P. Salvadori, G. Capannelli and
G. Martra, Catal. Lett., 1997, 44, 205; P. N. Rylander, Catalytic
Hydrogenation in Organic Syntheses, Academic Press, New York,
1979, ch. 11, pp. 186–187.
Notes and references
1
V. Kratky, M. Kralik, M. Mecarova, M. Stolcova, L. Zalibera and
M. Hronec, Appl. Catal., A, 2002, 235, 225.
X. D. Wang, M. H. Liang, J. L. Zhang and Y. Wang, Curr. Org.
Chem., 2007, 11, 299; M. H. Liu, W. Y. Yu, H. F. Liu and
2
3
126 Chem. Commun., 2012, 48, 3124–3126
This journal is c The Royal Society of Chemistry 2012