Chemoselective hydrogenation of 4-nitrostyrene to 4-aminostyrene by highly efficient TiO2 supported Ni3Sn2 alloy catalyst

Article abstract of DOI:10.1246/bcsj.20180381

Ni₃Sn2 alloy catalysts supported on various metal oxides (TiO₂, Al₂O₃, ZrO₂, SnO₂, and CeO₂) were successfully prepared by simple hydrothermal method and then applied to the hydrogenation of 4-nitrostyrene under H₂ 3.0 MPa at 423 K. All the supported catalysts hydrogenated the nitro group more preferentially than the olefin group from the initial reaction stages, showing 100% chemoselectivities towards the desired 4-aminostyrene. This may be attributed to -interaction between the oxygen lone pairs in the nitro group and Sn atoms in Ni₃Sn₂ alloy. By prolonging the reaction times, the 4- aminostyrene yields increased and finally reached the maximum yields. Among the catalysts, Ni₃Sn₂/TiO₂ alloy catalyst showed the highest catalytic activity with remarkably high chemoselectivity towards 4-aminostyrene. The conversion and chemoselectivity were 100% and 79%, respectively, at a reaction time of only 2.5 h. From the physical and chemical characterization of the supported catalysts, it was clear that the catalytic activity was correlated with H₂ uptake. The application of the best catalyst for the hydrogenation of a wide variety of substituted nitroarenes resulted in the chemoselective formation of the corresponding aminoarenes.

Full text of DOI:10.1246/bcsj.20180381

Advance Publication Cover Page
Chemoselective hydrogenation of 4-nitrostyrene to 4-aminostyrene
by highly efficient TiO2 supported Ni3Sn2 alloy catalyst
Nobutaka Yamanaka, Takayoshi Hara, Nobuyuki Ichikuni, and Shogo Shimazu*
Advance Publication on the web February 1, 2019
doi:10.1246/bcsj.20180381
© 2019 The Chemical Society of Japan
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Chemoselective hydrogenation of 4-nitrostyrene to 4-aminostyrene
by highly efficient TiO2 supported Ni3Sn2 alloy catalyst
Nobutaka Yamanaka,1 Takayoshi Hara,1 Nobuyuki Ichikuni,1 and Shogo Shimazu*1
1Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University,
1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
E-mail: <shimazu@faculty.chiba-u.jp>
Shogo Shimazu
Shogo Shimazu received his PhD from Texas A&M University in 1983. After a research position at Sumitomo
Electric Industries, Ltd., he joined Chiba University as a research assistant and became a full professor in 2005.
His recent interests include interlayer catalysts, intermetallic catalysts, perovskite catalysts for organic synthesis,
catalytic utilization of biomass-derived compounds, and hybrid layer materials.
Abstract
Ni3Sn2 alloy catalysts supported on various metal oxides
transfer hydrogenation12,14. The other method is carried out by
the direct use of molecular H2, which is more favorable for the
chemoselective hydrogenation of nitroarenes to the
corresponding aminoarenes from environmental and industrial
viewpoints because it is less expensive and produces only water
(TiO2, Al2O3, ZrO2, SnO2, and CeO2) were successfully
prepared by simple hydrothermal method and then applied to
the hydrogenation of 4-nitrostyrene under H2 3.0 MPa at 423 K.
All the supported catalysts hydrogenated the nitro group more
preferentially than the olefin group from the initial reaction
stages, showing 100% chemoselectivities towards the desired
4-aminostyrene. This may be attributed to -interaction
between the oxygen lone pairs in the nitro group and Sn atoms
in Ni3Sn2 alloy. By prolonging the reaction times, the
4-aminostyrene yields increased and finally reached the
maximum yields. Among the catalysts, Ni3Sn2/TiO2 alloy
catalyst showed the highest catalytic activity with remarkably
high chemoselectivity towards 4-aminostyrene. The conversion
and chemoselectivity were 100% and 79%, respectively, at a
reaction time of only 2.5 h. From the physical and chemical
characterization of the supported catalysts, it was clear that the
catalytic activity was correlated with H2 uptake. The
application of the best catalyst for the hydrogenation of a wide
variety of substituted nitroarenes resulted in the chemoselective
formation of the corresponding aminoarenes.
as a byproduct13,15
.
When one or more reducible groups (e.g., C=C, C≡C,
C=O, and C≡N) are present in one nitroarene molecule, it is
difficult to direct the chemoselectivity of transition metal
catalysts (Pt, Pd, Ru, and Ni) towards the nitro group because
the catalysts cannot discriminate between different functional
groups9,16-18. Compared with Pt, Pd, and Ru, Ni is more
available in industrial applications due to its low cost and high
earth abundance5,19-21. Therefore, our interest has recently been
devoted to transforming non-chemoselective catalyst into
chemoselective catalyst for the hydrogenation of the nitro
group, even in the presence of other reducible groups.
To date, the improvement of the chemoselectivity of Ni
towards the nitro group has been achieved by means of
preparative methodology, strong metal support interaction
(SMSI) effect, and alloying with a second metal2,16,21. In
particular, the last approach has been actively adopted because
the addition of second metals leads to the change of the
electron density and the dilution of the active metal. Despite the
numerous efforts to develop Ni-based alloy catalysts such as
Keywords: Supported Ni3Sn2 alloy catalyst,
Chemoselective hydrogenation, 4-Nitrostyrene
Ni-B22,23
,
Ni-P-B24, and Ni-Co-B25,26 for the selective
hydrogenation of 4-chloronitrobenzene to 4-chloroaniline, the
substrate scope of the catalysts has not been investigated with
other functionalized nitroarenes. Ni-Au alloy catalyst showed a
variety of substrate applicability, when expensive Au was used
as the second metal16. Furthermore, the complexity of their
catalyst preparations makes process scale-up difficult27.
Therefore, our objective is to develop a cost-effective, easily
prepared, and chemoselective Ni-based alloy catalyst for the
hydrogenation of a wide variety of substituted nitroarenes to
the corresponding aminoarenes.
The addition effects of electropositive Sn, Ir, and Cu on
sol-gel Pd/SiO2 catalysts has been investigated for the
hydrogenation of cinnamaldehyde28,29. Only in the case of Sn
as a second metal, the chemoselectivity towards saturated
aldehyde decreased, which could be explained by both
geometric and electronic effects by alloying Pd with Sn. The
DFT calculations for the hydrogenation of -unsaturated
aldehydes demonstrated that the addition of Sn to Pt formed
-interaction between the oxygen lone pair and Sn, leading to
an increase in the chemoselectivity towards the corresponding
-unsaturated alcohols30. Even for the chemoselective
1. Introduction
The chemoselective hydrogenation of nitroarenes is an
important chemical transformation to produce the
corresponding aminoarenes, which are useful intermediates
utilized in agrochemicals, pharmaceuticals, dyes, and
pigments1-6
. Conventional method requires the use of
stoichiometric reducing agents such as sodium hydrosulfite,
iron, tin, or zinc in ammonium hydroxides, silanes,
decaboranes, and formates1,7, which leads to a high E-factor
(defined as the weight ratio of byproducts to desired product)
and has a negative impact on the environment8-10. In this
context, the catalytic hydrogenation of nitroarenes to the
corresponding aminoarenes has attracted much more attention
as a fascinating alternative approach due to its highly efficient
and more environmentally benign11,12
.
According to hydrogen source, there are two types of
catalytic hydrogenation11-13. One method is performed by the
extraction of hydrogen from hydrogen donors such as formic
acid, CO/H2O, HCOONH4, alcohols, NaBH4, hydrosilanes,
hydrazine, and ammonia borane, which is called catalytic

hydrogenation of 3-nitrosyrene to 3-aminostyrene, it has been
reported that the two O atoms adsorbed vertically on the top of
Sn atoms after the addition of Sn to Pt, based on the DFT
calculation results31. Based on the reported literatures, the
electropositive and inexpensive Sn has been added to Ni as
potential second metal in our previous work32. Ni-Sn alloy
catalysts were prepared easily by hydrothermal method and
then applied to the hydrogenation of 4-nitrostyrene as a model
reaction to evaluate their catalytic performance using molecular
H2 as the reducing agent. Under the optimized reaction
condition (H2 3.0 MPa and 423 K), Ni3Sn2 alloy catalyst
exclusively hydrogenated the nitro group rather than the olefin
group from the initial reaction stage, showing 100%
chemoselectivity towards the desired 4-aminostyrene. This
means that Ni3Sn2 alloy plays an important role in the
Ni:Sn molar ratio of 1.5 at room temperature. The metal oxide
was then added into the mixture as support and stirred for 1 h at
room temperature. The resulting solution was hydrothermally
treated at 423 K for 24 h, filtered, washed with distilled water,
and dried under vacuum at room temperature overnight. Finally,
the recovered powder was reduced under H2 atmosphere at 673
K for 1 h to obtain 10 wt% Ni3Sn2/MxOy alloy catalyst.
2.2. Catalyst characterization
Powder X-ray diffractograms (XRD) were recorded on a
MiniFlex 600 Rigaku incident X-ray diffractometer operated at
40 kV and 15 mA using CuKa radiation (= 0.15418 nm) and
identified by using Crystallography Open Database (COD)38.
The samples were scanned at a step width of 0.02° and a speed
of 5° min-1 over the range 20° ≤ 2 ≤ 80°. Before H2 uptake
measurement, the catalyst was heated at 473 K under vacuum
for 30 min and then treated at 673 K for 30 min under H2
atmosphere. The H2 uptake measurement was carried out twice
at 273 K to exclude the possibility of physical adsorption of H2
onto the catalyst. The chemically adsorped amount of H2 was
calculated by subtracting the physically adsorped amount
obtained in the latter measurement from the total adsorped
amount obtained in the former measurement. CO uptake
measurement was conducted similarly. Nitrogen adsorption and
desorption isotherms were measured at 77 K, the
liquid-nitrogen boiling temperature, using a Belsorp Max (BEL
Japan). The samples were degassed at 473 K for 2 h to remove
physisorbed gases prior to the measurements. The specific
chemoselective
hydrogenation
of
4-nitrostyrene
to
4-aminostyrene. The yield increased with reaction time and
finally reached a maximum of 87% with full conversion of
4-nitrostyrene at
a reaction time of 11 h, although
hydrogenation of the olefin group also occurred. These results
indicated that we could control the yield and chemoselectivity
towards the desired 4-aminostyrene by changing the reaction
time. A wide variety of substituted nitroarenes were smoothly
transformed into the corresponding aminoarenes by using this
catalyst, including other reducible groups such as -Cl, -COCH3,
and -COOCH3. However, such a relatively long reaction time
limits the practical application of this catalyst.
To address this issue, we endeavored to improve the
catalytic activity of Ni3Sn2 alloy. The addition of Lewis acid
FeCl3 enhanced the catalytic activity of Ni-W2C/mpg-C3N4 for
the synthesis of diverse functionalized aminoarenes from the
corresponding nitroarenes because it also interacted with the
substrate and intermediates to weaken the NO2, N=O, and N-O
bonds33. The presence of such an additive affected the product
purity and required a troublesome separation to be removed34.
The transition from bulk to nanoscale has a great effect on the
physical and chemical properties of the particles, leading to
high catalytic activity11,35. Therefore, supported metal catalysts
can be expected to be promising candidate for hydrogenation
reactions such as nitroarenes to aminoarenes36. In our previous
work on the chemoselective hydrogenation of furfural to
furfuryl alcohol, the catalytic activity significantly increased by
supporting Ni3Sn2 alloy on TiO237. We wondered whether this
method could be applied for the hydrogenation of
4-nitrostyrene. In this work, Ni3Sn2 alloy catalysts supported on
several metal oxides (TiO2, Al2O3, ZrO2, SnO2, and CeO2) were
prepared by simple hydrothermal method. The physical and
chemical characterization revealed that H2 uptake was well
associated with the catalytic activity. Among them, TiO2
supported Ni3Sn2 alloy catalyst possessed the highest catalytic
activity, drastically shortening the reaction time to 2.5 h with
little loss of the chemoselectivity towards the desired
4-aminostyrene product. Thus, we developed a cost-effective,
easily prepared, and highly efficient catalyst for the
surface areas (SBET
Brunauer-Emmett-Teller (BET) equation. The average pore
volumes (Vm) were calculated from the adsorbed N2 volume at
)
were calculated using the
a
relative pressure of approximately 0.990 using the
Barrett-Joyner-Halenda (BJH) method based on the adsorption
data.
2.3. Catalytic reaction
Commercially available organic chemicals were of
analytical grade and used as purchased without further
purification. All the catalytic hydrogenations were conducted in
a high-pressure autoclave with a pressure gauge, a magnetic
stirrer, and an oil bath. Typically, 0.10 g catalysts, 0.10 mmol
nitroarenes (substrate/Ni molar ratio
= 1.4), 3.0 mmol
n-dodecane as an internal standard, and 5.0 mL 1,4-dioxane
solvent were placed into a glass reaction tube and stirred at
room temperature for a selected time. After the autoclave was
sealed, pure H2 gas was introduced to remove air from the
system and kept at 3.0 MPa, and then the reaction system was
heated to 423 K. After the reaction, the reaction mixture was
taken out of the reaction system and analyzed by gas
chromatography. The products were identified by gas
chromatography (GC-8A, Shimadzu, using a flame ionization
detector) equipped with a flexible quartz capillary column
coated with Silicon OV-17. The conversion and yields of the
products were calculated using an internal standard method.
chemoselective
hydrogenation
of
4-nitrostyrene
to
4-aminostyrene. Furthermore, the best catalyst was applicable
to the chemoselective hydrogenation of a wide variety of
substituted nitroarenes.
3. Results and Discussion
3.1. Catalyst characterization
The as-prepared catalysts were first characterized by
XRD, and the XRD patterns of each catalyst are shown in
Figures 1 and S1-5. Ni3Sn2/CeO2 alloy catalyst exhibited peaks
at 2 = 28.6˚, 33.1˚, 47.6˚, 56.5˚, 59.1˚, 69.5˚, 76.8˚, and 79.1˚,
which were attributed to those of cubic CeO2 (COD
00-434-3161) (Figures 1a and S1). Ni3Sn2/SnO2 alloy catalyst
showed peaks at 2 = 26.7˚, 34.0˚, 38.1˚, 39.1˚, 42.8˚, 52.0˚,
54.9˚, 58.0˚, 62.1˚, 64.9˚, 66.1˚, 71.4˚, and 78.8˚, which are due
to the presence of tetragonal cassiterite SnO2 (COD 00-100-006
2. Experimental
2.1. Catalyst preparation
Ni3Sn2 alloy catalysts supported on different metal oxides
(MxOy = TiO2, Al2O3, ZrO2, SnO2, and CeO2) were prepared by
hydrothermal method in accordance with the procedure
reported earlier37. A detailed preparatory procedure is provided
in the ESI. Briefly, Ni(II) and Sn(IV) precursors were mixed at

×0.5
(a)
(b)
(c)
(d)
(e)
20
30
40
50
60
70
80
2 / degree
Figure 1. XRD results of various supported Ni3Sn2 alloy catalysts. (a) Ni3Sn2/CeO2, (b) Ni3Sn2/SnO2, (c) Ni3Sn2/TiO2, (d)
Ni3Sn2/ZrO2, and (e) Ni3Sn2/Al2O3. The three dashed lines represent the characteristic Ni3Sn2 alloy peaks at 2 = 30.8˚, 42.5˚, and
44.2˚.
2) (Figures 1b and S2). In the XRD pattern of Ni3Sn2/TiO2
alloy catalyst, the peaks corresponding to tetragonal anatase
were observed at 2 = 25.3˚, 37.1˚, 37.9˚, 38.7˚, 48.1˚, 54.0˚,
55.2˚, 62.2˚, 62.8˚, 68.9˚, 70.4˚, 74.1˚, 75.1˚, and 76.1˚ (COD
00-153-0151) (Figures 1c and S3). There were two intensive
diffraction peaks at 2 = 28.4° and 31.5˚, which matched well
with those of ZrO2 of a monoclinic baddeleyite structure (COD
00-900-5833) (Figures 1d and S4). The XRD analysis of
Ni3Sn2/Al2O3 alloy catalyst revealed peaks at 2 = 39.5˚, 46.0˚,
and 66.9˚, which were assigned to cubic -Al2O3 (COD
00-101-0461) (Figures 1e and S5). In addition to the diffraction
patterns of the metal oxides used, the XRD results of all the
prepared catalysts presented three characteristic peaks
corresponding to the reflections of the (101), (102), and (110)
lattice planes of hexagonal Ni3Sn2 alloy at 2 = 30.8˚, 42.5˚,
and 44.2˚, respectively (COD 00-152-3548) (Figure 1). The
broad peaks indicate the very small particle sizes of the Ni3Sn2
alloy. More importantly, there were no peaks assignable to
metallic Ni and Sn or their oxides and hydroxides. This means
that all the observed peaks were attributed to those of Ni3Sn2
alloy and the used metal oxides. The physical and chemical
properties, such as the particle size of Ni3Sn2 alloy, H2 uptake,
CO uptake, BET surface area, and average pore volume, are
summarized in Table 1. The particle sizes of Ni3Sn2 alloy were
calculated by using Scherrer’s equation on the Ni3Sn2 (101)
peak at 2 = 30.8˚. Compared with the bulk Ni3Sn2 alloy
catalyst reported in our previous work (D = 27.3 nm)32, much
smaller particle sizes were obtained by supporting the alloy on
the metal oxides, which implies a high dispersion of the Ni3Sn2
alloy particles. This assumption was corroborated by H2 and
CO uptake measurements because almost all of the supported
catalysts showed higher adsorption values than the bulk
catalyst. Even in the BET measurements, the supported
catalysts gave better results than the bulk catalyst. The above
results demonstrate that supporting the Ni3Sn2 alloy on metal
oxides has a positive effect on the physical and chemical
properties. Here, the order of H2 uptake of the supported
catalysts was as follows: Ni3Sn2/TiO2 > Ni3Sn2/Al2O3 >>
Ni3Sn2/ZrO2 > Ni3Sn2/SnO2 > Ni3Sn2/CeO2. However, the
order was not correlated with the intrinsic properties of the
used metal oxides (e.g., acidic, amphoteric, basic, reducible,
and non-reducible).
Table 1. Physical and chemical properties of various supported
3.2. Hydrogenation of 4-nitrostyrene
Ni3Sn2 alloy catalysts
In our previous work, the bulk Ni3Sn2 alloy acted as an
effective catalyst for the chemoselective hydrogenation of
4-nitrostyrene to 4-aminostyrene, providing a remarkably high
chemoselectivity of 87% with full conversion at a reaction time
of 11 h32. This hydrogenation is the most challenging reaction
due to the presence of the easily reducible olefin group in the
b
d
e
Catalyst
Da
H2
COc
SBET
Vm
Ni3Sn2
27.3
12.8
13.3
17.8
12.6
17.1
4.0
16.6
8.9
4.8
3.8
1.4
10.7
5.4
7.4
4.4
17
20
189
38
12
8
4.0
4.6
43.4
8.7
2.8
1.9
Ni3Sn2/TiO2
Ni3Sn2/Al2O3
Ni3Sn2/ZrO2
Ni3Sn2/SnO2
Ni3Sn2/CeO2
same nitroarene molecule7,16,33,39
, and the hydrogenation
products are the desired 4-aminostyrene (2), undesired
4-ethylnitrobenzene (3), and over-hydrogenated 4-ethylaniline
(4) (Scheme 1). However, the catalytic activity was not enough
for industrial application, and it is highly desirable to develop
more active catalyst for the industrially important reaction
while maintaining similarly high chemoselectivity. In this work,
the hydrogenation of 4-nitrostyrene was employed as a model
reaction to investigate the catalytic performance of various
supported Ni3Sn2 alloy catalysts under a reaction temperature
of 423 K and H2 pressure of 3.0 MPa. The hydrogenation
results are summarized in Table 2.
3.6
3.2
aThe crystallite size of Ni3Sn2 alloy derived from the XRD
peak of Ni3Sn2 (101) at 2θ = 30.8° using Scherrer's equation
(nm).
bH2 uptake after correction for physical and chemical
adsorption at 273 K (μmol g-1).
cCO uptake after correction for physical and chemical
adsorption at 273 K (μmol g-1).
dBET specific surface areas determined by N2 physisorption at
77 K (m2 g-1).
ePore volume (cm3 g-1).

show that a high chemoselectivity towards the corresponding
substituted aminoarenes was obtained at full conversion,
regardless of the electron-donating or electron-withdrawing
ability of the functional groups. As shown in entries 1 and 2 of
Table 3, the position of the olefin group did not have an impact
on the chemoselectivity towards the nitro group. Nitrobenzene
was hydrogenated to aniline completely (entry 3). It is well
known that the formation of aniline is unavoidable as a
byproduct for the hydrogenation of 4-chloronitrobenzene due to
the simultaneous dehalogenation of the C-Cl bond and
hydrogenation of the nitro group7,19,40. When the best catalyst
was employed, the corresponding 4-chloroaniline was formed
quantitatively without the occurrence of any secondary reaction
(entry 4). It is also fascinating to note that the hydrogenation of
4’-nitroacetophenone and methyl 4-nitrobenzoate proceeded
with high tolerance for other reducible groups, such as -COCH3
and -COOCH3, to afford the corresponding aminoarenes with
excellent chemoselectivities of 87% and 90%, respectively
(entries 5 and 6). The obtained results illustrate the great
potential of Ni3Sn2/TiO2 alloy catalyst for the chemoselective
hydrogenation of various substituted nitroarenes.
Scheme 1. Hydrogenation pathway of 4-nitrostyrene.
Table 2. Hydrogenation of 4-nitrostyrene by various supported
Ni3Sn2 alloy catalystsa
Time Conv.
Yield / %
2 3 4
Sel.b
/ %
Entry Catalyst
/ h
/ %
1c
2
3
4
5
6
Ni3Sn2
11
100
100
100
100
100
83
87 0 13
79 0 16
75 0 13
67 0 21
78 0 15
67 0 12
87
79
75
67
78
81
Ni3Sn2/TiO2
Ni3Sn2/Al2O3
Ni3Sn2/ZrO2
Ni3Sn2/SnO2
2.5
4.5
4.5
10
Ni3Sn2/CeO2 19.5
aReaction conditions: 4-nitrostyrene/Ni molar ratio = 1.4;
1,4-dioxane, 5.0 mL; n-dodecane, 0.30 mmol; H2, 3.0 MPa;
temperature, 423 K. The conversion and yields were
determined by GC using an internal standard technique. The
yield numbers 2, 3, and 4 represent the desired 4-aminostyrene,
undesired 4-ethylnitrobenzene, and over-hydrogenated
Table 3. Hydrogenation of various substituted nitroarenes by
Ni3Sn2/TiO2 alloy catalysta
4-ethylaniline,
respectively.
bThe
selectivity
for
4-aminostyrene. cOur previous work32.
Regardless of the support type used, all the supported
Ni3Sn2 alloy catalysts hydrogenated the nitro group more
preferentially than the olefin group from the initial reaction
stages as shown in Figures S6-10, which led to
chemoselectivities of 100% towards the desired 4-aminostyrene
without the formation of the undesired 4-ethylnitrobenzene
byproduct. This is possibly because the oxygen lone pairs in the
nitro group formed -interaction with partially cationic Sn
species (Sn+) formed in the surface of in Ni3Sn2 alloy30. Thus,
Ni3Sn2 alloy was found to be crucial for the chemoselective
hydrogenation of 4-nitrostyrene to 4-aminostyrene. By
prolonging the reaction times, the 4-aminostyrene yields
increased and finally reached the maximum yields. In other
words, we could control the yield and chemoselectivity towards
the desired 4-aminostyrene by changing the reaction time.
Unfortunately, the supported catalysts showed slightly lower
chemoselectivities than the bulk catalyst. This could be
explained easily by the fact that supporting Ni3Sn2 alloy on the
metal oxides accelerated the reaction rate of the chemoselective
hydrogenation of 4-nitrostyrene to 4-aminostyrene, which was
then hydrogenated 4-ethylaniline when 4-nitrostyrene was
consumed. Among the supported catalysts, Ni3Sn2/TiO2 alloy
catalyst showed the highest catalytic activity with a remarkably
high chemoselectivity towards 4-aminostyrene. The conversion
and chemoselectivity were 100% and 79% at a reaction time of
aReaction conditions: Ni3Sn2/TiO2 alloy catalyst, 0.10 g;
substrates, 0.10 mmol; 1,4-dioxane, 5.0 mL; n-dodecane, 0.30
mmol; H2, 3.0 MPa; temperature, 423 K. The conversion and
selectivity were determined by GC using an internal standard
technique.
4. Conclusion
Ni3Sn2 alloy catalysts supported on a range of metal
oxides (TiO2, Al2O3, ZrO2, SnO2, and CeO2) were successfully
prepared by simple hydrothermal method. The XRD patterns
possessed the broad characteristic peaks of Ni3Sn2 alloy. For
the hydrogenation of 4-nitrostyrene, the dispersed Ni3Sn2 alloy
particles resulted in both the preferential hydrogenation of the
nitro group rather than the olefin group and high catalytic
activity. The activity of the supported catalysts strongly
depended on the H2 uptake. Among them, Ni3Sn2/TiO2 alloy
catalyst had an attractive catalytic performance with
a
remarkably high chemoselectivity of 79% towards the desired
4-aminostyrene with full conversion at such a short reaction
time of 2.5 h, which provides a low-cost, easily prepared, and
highly efficient catalyst for industrial application. In this work,
we could improve the intrinsically low activity of Ni3Sn2 alloy
by supporting it on TiO2 with little loss of its high
chemoselectivity towards the nitro group. The best catalyst also
exhibited good chemoselective hydrogenation of the nitro
group in the presence of the other reactive groups.
only 2.5
h
(Table 2). The physical and chemical
characterization elucidated that the catalytic activity of the
supported catalyst was associated with H2 uptake and is in the
order of Ni3Sn2/TiO2 > Ni3Sn2/Al2O3 >> Ni3Sn2/ZrO2
>
Ni3Sn2/SnO2 > Ni3Sn2/CeO2. Therefore, it could be concluded
that the amount of H2 dissociated on Ni(0) was an important
factor in obtaining such a high hydrogenation activity.
3.3. Substrate scope
Finally, the substrate scope of the best catalyst,
Ni3Sn2/TiO2 alloy, was investigated for the hydrogenation of a
wide variety of substituted nitroarenes. The results in Table 3
Acknowledgement
This work was financially supported by JSPS KAKENHI
Grant Number 15K06565 and JSPS Bilateral Joint Research

Project (2014-2017) and Frontier Science Program of Graduate
School of Science and Engineering, Chiba University.
E. Sulman, D. Y. Murzin, L. Kiwi-Minsker, Ind. Eng.
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35. A. S. Sharma, H. Kaur, D. Shah, RSC Adv. 2016, 6, 28688.
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Wang, Green Chem. 2016, 18, 2435.
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