Pt-NH2-Fe3O4 catalyst with excellent catalytic performance for hydrogenation of nitroarenes in aqueous medium

Article abstract of DOI:10.1080/15533174.2013.797450

Catalytic hydrogenation of aromatic nitro compounds was carried out in neat water with Pt nanoparticles deposited on surface amine-functionalized magnetite. The hydrophilic Pt-NH₂-Fe₃O₄ catalyst exhibited excellent activity as well as superior selectivity to the corresponding amines. 99.9% yield of p-chloroaniline (p-CAN) was obtained at 303 K under an H₂ atmosphere in aqueous media; the turnover frequency value reached 500 h^-1 in the absence of any additives or promoters. Furthermore, the novel nanocomposites can be readily isolated from the reaction system by a magnet and recycled at least six times without any loss in activity.

Full text of DOI:10.1080/15533174.2013.797450

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Pt–NH2–Fe3O4 Catalyst with Excellent Catalytic
Performance for Hydrogenation of Nitroarenes in
Aqueous Medium
Guangyin Fan a & Yinhu Wang a
a Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, School of
Chemistry and Chemical Industry , China West Normal University , Nanchong , P. R. China
Accepted author version posted online: 17 Dec 2013.Published online: 04 Mar 2014.
To cite this article: Guangyin Fan & Yinhu Wang (2014) Pt–NH2–Fe3O4 Catalyst with Excellent Catalytic Performance for
Hydrogenation of Nitroarenes in Aqueous Medium, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal
Chemistry, 44:7, 967-973, DOI: 10.1080/15533174.2013.797450
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 44:967–973, 2014
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.797450
Pt–NH2–Fe3O4 Catalyst with Excellent Catalytic
Performance for Hydrogenation of Nitroarenes in Aqueous
Medium
Guangyin Fan and Yinhu Wang
Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, School of Chemistry and
Chemical Industry, China West Normal University, Nanchong, P. R. China
significantly limits the selectivity to chloroanilines, and that the
formation of hydrogen chloride from this process is likely ad-
sorbed on the active sites causing deactivation of the catalyst
or corrosive to the reactor.[14] Therefore, great efforts have been
paid to overcome this problem, such as introducing special pro-
moters or inhibitors[13,16,30] and modifying the properties of the
catalysts. However, the use of inhibitors and modifiers brings
about impurities in the final product, and they must be elimi-
nated after processing for further applications. Thus, it is highly
desirable to develop simpler hydrogenation processes operat-
ing at mild conditions without hydrodechlorination. Recently, it
was reported that gold[31,32] and silver[33–35] deposited on SiO2
or ZrO2 could completely inhibit hydrodechlorination reaction
and had the excellent selectivity to chloroaniline in the liquid
hydrogenation of chloronitrobenzene, however, present reaction
systems suffered from relatively high temperature and pressure
(T > 373 K and P > 1.0 MPa H2).
In recent years, supported Pt catalysts have been found to be
among the most promising ones owing to their high selectivity
to the formation of the desired amines. Especially, Pt nanoparti-
cles based on special materials, including iron oxides[36–39] and
PICP[40] have revealed that Pt catalysts are also highly selective
for the hydrogenation of chloronitrobenzene under mild con-
dition. However, these Pt-based hydrogenation procedures are
subjected to some general insufficiencies, including the use of
hazardous organic solvents as the reaction media and form of a
non-negligible amount of the condensation by-product between
amines and alcohols (served as solvents).[32] Subsequent stud-
ies[41,42] revealed that the addition of adequate amount of water
into organic solvents (alcohols) could improve the activity and
selectivity of the catalysts, but it was hard to completely over-
come the condensation of by-products because of the present of
alcohols. Therefore, some researchers try to perform the hydro-
genation of nitro group in neat water. In such scenarios, water,
the most benign, abundant, and inexpensive solvent would lead
to a particularly green process in the view of green chemistry.
However, only one successful example of the use of water as
reaction media was reported in the liquid hydrogenation of ni-
tro compound.[43] It was found that the Pt/GA (gum acacia)
Catalytic hydrogenation of aromatic nitro compounds was car-
ried out in neat water with Pt nanoparticles deposited on surface
amine-functionalized magnetite. The hydrophilic Pt–NH2–Fe3O4
catalyst exhibited excellent activity as well as superior selectivity to
the corresponding amines. 99.9% yield of p-chloroaniline (p-CAN)
was obtained at 303 K under an H2 atmosphere in aqueous media;
the turnover frequency value reached 500 h−1 in the absence of any
additives or promoters. Furthermore, the novel nanocomposites
can be readily isolated from the reaction system by a magnet and
recycled at least six times without any loss in activity.
Keywords amine, hydrogenation, nitroarene, platinum catalyst,
water
INTRODUCTION
Aromatic amines are considered as versatile compounds
and have been used in many commercial applications in the
chemistry of organic fine chemicals, such as the synthesis of
dyes, drugs, herbicides, and pesticides.[1] Many commonly used
routes are still based on stoichiometric reduction which pro-
duce large amounts of wastes such as acid effluents or metal
oxides residue.[2,3] The environmentally benign synthesis of
amines facilitated by catalytic hydrogenation is attracting in-
creasing attention in recent years, a variety of precious metals
such as Pd,[4–6] Pt,[7–20] Rh,[21] Ru[22–24], and non-noble metals
such as nickel[25–29] are investigated either in bulk or supported
forms for the catalytic reduction of aromatic nitro-compound
into the corresponding amine. However, one critical limitation
with the catalytic hydrogenation is that the co-occurrence of the
hydrodechlorination in chlorinated aromatic compounds, which
Received 8 March 2013; accepted 10 April 2013.
Address correspondence to Guangyin Fan, Chemical Synthesis
and Pollution Control Key Laboratory of Sichuan Province, School
of Chemistry and Chemical Industry, China West Normal University,
Nanchong 637009, P. R. China. E-mail: fanguangyin@cwnu.edu.cn
Color versions of one or more of the figures in the article can be
found online at www.tandfonline.com/lsrt.
967

968
G. FAN AND Y. WANG
catalyst could catalyze hydrogenation of nitroarenes to ary- on carbon-coated copper grid and dried at room temperature.
lamines in aqueous medium with a nitroarenes/catalyst molar The X-ray diffraction (XRD) patterns were obtained using a
ratio of 416 in time of 6–8 h, however, the activity and yield of modern multipurpose theta/theta powder X-ray diffraction sys-
chlorinated amine were not satisfied enough. In this sense, there tem, equipped with a fast linear detector. X-ray photoelectron
is a strong incentive to develop new simple, efficient, easily han- spectroscopy (XPS, Kratos XSAM800) spectra was obtained by
dled procedures that can allow the highly active and selective using Al Kα radiation (12 kV and 15 mA) as an excitation source
reduction of the nitro group in water under mild conditions.
(hv = 1486.6 eV) and Au (BE Au4f = 84.0 eV) and Ag (BE
In the present study, we prepared amine-functionalized Ag3d = 386.3 eV) as reference. All binding energy (BE) values
Fe3O4 stabilized Pt nanoparticles for the selective hydrogenation were referenced to C 1s peak of contaminant carbon at 284.6 eV.
of nitroarenes in aqueous medium. With a nitroarenes/catalyst Brunauer–Emmett–Teller (BET) surface areas were measured
molar ratio of 1500, the complete conversion was achieved at by nitrogen adsorption at 77.05 K on an ASAP-2020 adsorp-
303 K under an H2 atmosphere; the turnover frequency (TOF) tion apparatus. A Fourier transform infrared (FT-IR) spectrum
was reached about 500 h−1. To the best of our knowledge, this was recorded with a Nicolet 6700 (resolution 0.4 cm−1) infrared
excellent catalytic property for the hydrogenation of chloroni- spectrometer and samples were dispersed in potassium bromide
trobenzene over Pt-based catalysts under milder conditions has and compressed into pellets.
not been reported. The Pt–NH2–Fe3O4 catalyst could reuse six
Catalyst Recycles
times and conveniently separated from the reaction system by a
The catalyst was recycled as following procedures, at the
magnet.
end of one hydrogenation run, the catalyst was separated from
the reaction system by using a magnet, and the supernatant
EXPERIMENTAL
liquid was removed from the flask. The black solid catalyst
was thoroughly washed three times with ethanol to remove the
adsorbed species, and then fresh substrate and solvent were
added into for next runs. All liquid samples were analyzed by
gas chromatography (Agilent GC-7890) with an FID detector
and HP-5 supelco column (30 m × 0.25 mm, 0.25 μm film) and
nitrogen as a carrier gas.
Synthesis of Pt–NH2–Fe3O4
The Fe3O4–NH2 stabilized Pt nanoparticles (Pt–NH2–
Fe3O4) were synthesized as follows: 0.5 g of Fe3O4–NH2 and
50 mL ethanol were mixed into a 100 mL round bottom and
were under ultrasonication for 30 min using an ultrasonic clean-
ing bath. Then 1.0 mL of the aqueous H2PtCl6· 6H2O (32.1 mM)
solution was dropped into flask and maintained under ultrason-
ication for 2 h. Afterward, the flask was put into an ice–water
bath, an excessive NaBH4 solution was slowly added into the
above mixture within 15 min under vigorous stirring. After stir-
ring for 3 h, the black solid was collected with a magnet, washed
with deionized water for several times, and finally dried under
vacuum at room temperature overnight, The weight percentage
of Pt in the catalyst was determined by ICP analysis (1.3 wt%
Pt–NH2–Fe3O4).
RESULTS AND DISCUSSION
The synthesis of the Pt–NH2–Fe3O4 catalyst is described
in Scheme 1. Amine functionalized Fe3O4 nanoparticles were
synthesized by a one-pot solvethermal method at 473 K in a
reaction time of 6 h at the first step. Then, Pt ionic coordinated
with amine on the surface of the Fe3O4 and reduced with NaBH4
aqueous solution with vigorous stirring, at last, Pt–NH2–Fe3O4
catalyst was obtained with the help of a magnet. The amine
group on the surface of Fe3O4 acts as a stabilizer and plays an
important role in avoiding the leaching of Pt nanoparticles.
Figure 1 shows the XRD analysis patterns of Fe3O4–NH2
and Pt–NH2–Fe3O4. The XRD pattern of Fe3O4–NH2 shows
that the sharp and strong peaks are corresponding to the char-
acteristic peaks of magnetite nanoparticles, which indicates the
products are well crystallized[5] and are the exactly same results
as that reported by Li et al.[44] and Ma et al.[5] Furthermore,
compared with Fe3O4–NH2, an almost identical XRD pattern
was observed after immobilization of Pt on the magnetite (Fig-
ure 1b), indicating the crystalline structure and the average size
of the crystalline domain of the support were well maintained
in the Pt samples. No peaks toward metallic Pt were detected
owing to the fact that the Pt particle sizes were very small, in-
Pt–NH2–Fe3O4 for Hydrogenation
The reaction was carried out in a 25 mL round-bottom flask.
A typical procedure for the hydrogenation of nitroarenes is as
follows: the desired amounts of catalyst (5 mg), nitroarenes
(0.5 mmoL), and solvent (7.0 mL) were charged to the flask
equipped with a balloon. The reactor was vacuumized and
flushed with pure hydrogen. When the designated reaction tem-
perature was reached, the stirring rate was adjusted to 1500 rpm,
and reaction time was accounted. Many experimental data were
obtained by repeating the reaction two or three times and they
had the good repeatability.
Catalyst Characterization
Transmission electron microscopy (TEM) measurements dicating that the Pt particles are highly dispersed on the surface
were carried out on a JEOL model 2010 instrument operated of the amine functionalized Fe3O4.
at an accelerating voltage of 200 kV. The sample for TEM char-
The BET surface area, average pore diameter, and total
acterization was prepared by placing a drop of the dispersion pore volume of support and catalyst are listed in Table 1.

HYDROGENATION OF NITROARENES OVER Pt–NH2–Fe3O4
969
TABLE 1
BET surface area, average pore diameter and total pore volume
of support and catalyst
BET specific
Total pore
volume
surface area Average pore
Sample
(m2/g)
diameter (nm)
(cm3/g)
Fe3O4–NH2
Pt–NH2–Fe3O4
23.43
51.74
8.24
18.92
0.0483
0.2447
immobilized on the surface of the nanoparticles.[46] Further-
more, compared with Fe3O4–NH2, an almost identical FT-IR
pattern was observed after immobilization of Pt on the mag-
netite (Figure 3b), indicating that almost no change occurs after
immobilization of Pt on the magnetite nanoparticles surface.
XPS survey scan of the surface of the Pt–NH2–Fe3O4 parti-
cles showed the presence of oxygen, carbon, platinum, Pt4f, and
iron (Figure 4A). To ascertain the oxidation state of the Pt, high-
resolution narrow scan was carried out (Figure 4B). According
to the previous research, the Pt 4f7/2 and 4f5/2 peaks found at
BE = 71.4 and 74.4 eV, respectively, have been attributed to
metallic platinum which was well consistent with the binding
energy of Pt (0).[7] The second set of peaks for Pt 4f7/2 and Pt
4f5/2 observed at BE = 74.7 and 77.7 eV, respectively, occurring
at higher BE values can be attributed to Pt atoms with lower
charge density. However, under the reaction conditions most of
the unreduced catalyst also gets reduced and contribute to high
yields of the desired product.
The catalytic activity of Pt–NH2–Fe3O4 sample is measured
by using a model reaction of the catalytic reduction of p-
chloronitrobenzene (p-CNB) into p-CAN with hydrogen, which
has been demonstrated to be an effective way to evaluate the cat-
alytic capability of noble metal nanocatalysts.[4,23] Table 2 shows
the conversion and selectivity to p-CAN for p-CNB hydrogena-
tion at 303 K under an H2 atmosphere over Pt–NH2–Fe3O4 in
aqueous media. No conversion was discovered in the absence of
catalysts or in the presence of pure Fe3O4–NH2 under the same
reaction conditions, which clearly proved that platinum particles
SCH. 1. Schematic process for loading Pt particles onto the surface of amine-
functionalized magnetite composite. (1) Synthesis of Fe3O4–NH2. (2) Pt ionic
coordinates with Fe3O4–NH2. (3) Reduction and the form of loading Pt particles.
Characterization results showed that BET surface area, aver-
age pore diameter, and total pore volume of Pt–NH2–Fe3O4
catalyst were higher than those of support. These changes are
mainly due to dispersion property caused by the addition of Pt
particles. TEM experiments have been carried out to detect a
possible structure of the metallic Pt particles (Figure 2). These
images show that the Fe3O4 support has the average particle
size of about 15 nm. However, the identification of the small
Pt particles was unsuccessful, possibly due to the poor contrast
between Pt and Fe3O4 support.
The FT-IR spectra of Fe3O4–NH2 and Pt–NH2–Fe3O4 were
also investigated. Figure 3a shows the FT-IR spectrum of
Fe3O4–NH2. The peaks at 1055, 1629, 3426, and around
2846–2923 cm−1 correspond to C–N stretching, N–H defor-
mation and C–H stretching models of the alkyl chain,[45] indi-
cating that large amount of 1,6-hexanediamine molecules are
FIG. 2. Typical TEM images of Pt–NH2–Fe3O4 (A and B) at different mag-
nifications.
FIG. 1. XRD patterns of (a) Fe3O4–NH2 and (b) Pt–NH2–Fe3O4 catalysts.

970
G. FAN AND Y. WANG
TABLE 2
Hydrogenation of p-CNB over Pt–NH2–Fe3O4 catalyst in
different solventsa
Sel. (%)
Solvent
Conv. (%) p-CAN AN p-CNSB Others
H2Ob
—
—
>99.9
>99.9
>99.9
>99.9
87.3
93.4
78.3
96.2
—
—
0.0
0.0
0.0
0.0
12.2
5.1
15.8
1.4
—
n.df
n.d
n.d
n.d
0.3
0.3
5.9
2.4
H2O
61.2
93.3
100
0.0
0.0
0.0
0.0
0.2
1.2
0.0
0.0
H2Oc
H2Od
H2Oe
100
FIG. 3. FT-IR spectra of (a) Fe3O4–NH2 and (b) Pt–NH2–Fe3O4.
Methanol
n-Propanol
1,4-Dioxane
Hexane
44.7
61.1
25.7
29.6
were the indispensable component in the hydrogenation p-CNB
to the corresponding amines. The data showed that the conver-
sion of p-CNB reached 100% with the reaction time increased
from 1 to 3 h. Moreover, the high selectivity (>99.9%) for
p-CAN maintained even at 100% p-CNB conversion, and this
phenomenon most probably attributed to the intermediates pro-
duced in the reaction process being further hydrogenated to the
desired product p-CAN and the undesired hydrodechlorination
reaction of p-CNB molecule was inhibited during the reaction.
In addition, a complete conversion was detected within 25 min
when the reaction was performed under the hydrogen pressure
of 1 MPa H2 (the reaction was carried out in a 60 mL Parr
stainless-steel reactor). It also could be seen that the selectivity
to p-CAN maintained when the reaction was conducted at 1 MPa
H2. These data show that the undesired hydrodechlorination can
be avoided over the Pt–NH2–Fe3O4 catalyst even at higher H2
pressure, indicating that Pt–NH2–Fe3O4 was an excellent cata-
lyst for selective hydrogenation of p-CNB to p-chloroaniline in
aqueous media.
Table 2 also presents the activities and selectivities for p-CNB
hydrogenation at 303 K and an H2 balloon over Pt–NH2–Fe3O4
in a range of organic solvents. Special attention was made to dis-
tinguish the by-products in the reduction of p-CNB in different
solvents (with GC-MS). Aniline (AN), p-chloronitrosobenzene
(p-CNSB), and the condensation product between amines and
alcohols were detected as the by-products in the investigated
solvents. When methanol and n-propanol were used as the sol-
vents, the catalyst Pt–NH2–Fe3O4 could catalyze the p-CNB
to p-CAN with conversions of 44.7% and 61.1%, and the
Notes. aReaction conditions: p-chloronitrobenzene (0.5 mmol),
5 mg Pt (1.3 wt%)–NH2–Fe3O4 catalyst in different solvents (7 mL)
at temperature of 303 K with an H2 balloon in 1 h.
b5 mg pure Fe3O4–NH2.
cReaction time: 2 h.
dReaction time: 3 h.
eReaction time: 25 min; P = 1 MPa.
fNot detected.
selectivities to p-CAN could reach 87.3% and 93.4%, respec-
tively. As for the by-products, small amount of AN (ca. 0.2%
and 1.2%) and condensation product (both are 0.3%) as well
as large amount of the intermediate p-CNSB (ca. 12.2% and
5.1%) were detected. However, the use of other organic sol-
vents such as 1,4-dioxane and hexane resulted in low conver-
sion of p-CNB (below 30%) under identical reaction conditions.
Although the hydrodechlorination product of AN could be com-
pletely inhibited, increased unknown by-products was detected.
Amazingly, p-CNB possesses very little solubility in neat wa-
ter, but a comparable p-CNB conversion of 61.2% was obtained
with the highest selectivity (>99.9%) for p-CAN during the
reaction process. The results indicate that the catalytic activity
for the p-CNB hydrogenation is closely related with the solvent
polarity.
We also compared the activity and selectivity of
Pt–NH2–Fe3O4 with those of Pt deposited on Al2O3, TiO2,
AC, MCM-41, MWCNTs, and Fe3O4 in aqueous medium. The
results in Table 3 indicated that both the Pt–NH2–Fe3O4 and
Pt/MWCNTs showed the highest activity for the hydrogenation
of p-CNB to p-CAN, but the catalyst Pt–NH2–Fe3O4 exhib-
ited higher selectivity (>99.9%) than the catalyst Pt/MWCNTs
(93.6%). In addition, the poor activity of 30.7% was obtained
by the catalyst Pt/MCM-41 and the lowest selectivity of 23.6%
toward p-CAN was detected by the catalyst Pt/Al2O3 as a re-
sult of the severe side reaction of hydrodechlorination under
identical reaction. These data show that the choice of the solid
support has a significant influence on the catalytic activity and
selectivity.
FIG. 4. (A) The wide survey XPS spectrum and (B) Pt
Pt–NH2–Fe3O4 catalyst.
peaks of
4f

HYDROGENATION OF NITROARENES OVER Pt–NH2–Fe3O4
971
TABLE 3
Comparative study of different supported platinum catalysts
for hydrogenation of aromatic nitro compoundsa
Sel. (%)
Catalyst
Conv. (%) p-CAN p-CNSB AN Others
Pt/Al2O3
Pt/TiO2
99.0
95.5
30.7
82.3
100
23.6
96.1
97.7
98.9
>99.9
93.6
0
0
0
0
0
0
0
76.4
3.4
0.9
1.1
0.0
6.4
0.0
n.d
n.d
1.4
n.d
n.d
n.d
n.d
Pt/MCM-41
Pt/AC
Pt–NH2–Fe3O4
Pt/MWCNTs
Pt–Fe3O4
100
81.1
>99.9
Note. aReaction conditions: p-chloronitrobenzene (0.5 mmol), 5 mg
of catalyst in 7 mL water at temperature of 303 K with an H2 balloon
in 3 h.
FIG. 5. Recycling of Pt–NH2–Fe3O4 for the hydrogenation of p-CNB.
Compared with the reported Pt-based catalytic systems,
which are highly selective to hydrogenation of haloaromatic of the aromatic nitro compounds to the corresponding amines
nitro compounds, the catalytic performance of this catalytic with a substrates/catalyst ratio of 1500. The reduction of p-
system composed of Pt–NH2–Fe3O4 and the solvent of water CNB and nitrobenzene could be accomplished within 3 h and
is the best one. Such as Zhang et al.[36] obtained 100% yield of 3.5 h, respectively. Other aromatic nitro-compound required a
p-CAN over Pt–Fe3O4 catalyst at 333 K and 1 atm hydrogen reaction time of 4 h for the complete hydrogenation, which is
pressure, however, the TOF was only 19 h−1. Sreedhar et al.[43] probably due to the relatively large steric hindrance or the low
only obtained 88% yield with a TOF of 52 h−1 with catalyst solubility of the reactants in water. Especially, nearly complete
Pt/GA at room temperature under atmospheric pressure in wa- yield (>99.9%) of p-CAN was observed when the catalyst was
ter. In the present work, more than 99.9% yield of p-CAN was reused six times. Moreover, no hydrodechlorination product was
observed at 303 K and a hydrogen balloon pressure in aqueous detected in each runs as shown in Figure 5. The high dispersed
media; the TOF value reached 500 h−1 with p-CNB/catalyst mo- and stable immobilized active Pt species by the amine groups
lar ratio of 1500 in the absence of any additives or promoters. on the surface of the catalyst was responsible for the excellent
The comparison the activity and selectivity with those reported reusability. The magnetic property of the catalyst facilitated the
under similar conditions was summarized in Table 4.
separation and redispersion of the nanoparticles after comple-
The catalytic hydrogenation of a variety of aromatic nitro tion of each run.
compounds over Pt–NH2–Fe3O4 catalyst was carried out in
Although it was difficult to give the exact reaction mechanism
aqueous media at 303 K under a hydrogen balloon pressure of the present Pt–NH2–Fe3O4 system catalyzed hydrogena-
of H2 and the results are shown in Table 5. The results indicated tion of nitro aromatics, some useful information was achieved
that the catalyst Pt–NH2–Fe3O4 could afford a rapid conversion through analysis of the reaction results. The results indicate that
TABLE 4
Comparison of previous study of different supported platinum catalysts for hydrogenation of o- and p-CNB in similar conditions
Catalyst
Substrate
Conditions
Conv. (Yield) (%)
Sel. (%)
TOF (h−1
)
Ref.
[43]
[40]
[47]
[47]
[47]
[36]
[11]
[36]
GA-Pt
Pt-PICP
Pt/Al2O3
Pt/ZrO2
Pt/TiO2
Pt/Fe3O4
Pt–Fe3O4–Fe3+
Pt/Fe2O3
Pt–NH2–Fe3O4
p-CNB
p-CNB
p-CNB
p-CNB
p-CNB
o-CNB
o-CNB
o-CNB
p-CNB
r.t., 1 atm H2, H2O
r.t., 1 atm H2, THF
(88)
(96)
99.0
99.4
99.5
100
100
100
100
—
—
80.9
90.4
92.8
52
200
266
432
2304
19
21
805
500
303 K, 1 atm H2, ethanol
303 K, 1 atm H2, ethanol
303 K, 1 atm H2, ethanol
333 K, 1 atm H2, methanol
303 K, 1 atm H2, methanol
333 K, 1 atm H2, methanol
303 K, 1 atm H2, H2O
(>99.9)
(83.4)
(>99.9)
>99.9
This work

972
G. FAN AND Y. WANG
TABLE 5
of hydrodechlorination activity and the absence of condensa-
tion reaction between amines and alcohols are responsible for
complete selectivity to the corresponding amine.
Hydrogenation of different substrates over Pt–NH2–Fe3O4
catalyst
Entry Nitro-aromatic
1
Product
Time (h) Yield (%)
CONCLUSIONS
3.5
3
97.6
>99.9
98.7
In summarization, the hydrophilic Pt–NH2–Fe3O4 catalyst
was prepared by deposited Pt particles onto the surface of the
amine-functionalized magnetite nanoparticles through liquid-
phase reductive process. The Pt–NH2–Fe3O4 showed high ef-
ficiency for the clean reduction of a variety of aromatic nitro
compounds at 303 K under an H2 atmosphere in water. The un-
precedented high activity and selectivity achieved for the clean
synthesis of amine via aqueous Pt-catalyzed hydrogenation is
preliminarily attributed to a significant beneficial effect of water
as a solvent. The side reaction of hydrodechlorination and the
condensation could be entirely eliminated in the presence of wa-
ter. In addition, the Pt–NH2–Fe3O4 catalyst was quite stable and
could be reused several times without significant deactivation.
Therefore, the results provide a kind of more robust and eco-
friendly catalytical system for the development of a sustainable
catalytic route for the production of aromatic amines.
2
3
4
4
5
6
4
4
4
>99.9
97.0
>99.6
7
8
9
4
4
4
99.9
95.1
93
FUNDING
This work was financially supported by the National Natural
Science Foundation of China (21207109), Scientific Research
Fund of Sichuan Provincial Education Department (11ZA034),
and the Opening Project of Key Laboratory of Green Catalysis
of Sichuan Institutes of High Education (No. LZJ1205).
Note. Reaction conditions: 0.5 mmol of substrates, 5 mg of catalyst
in 7 mL water at temperature of 303 K with an H2 balloon.
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