Lamellar Ni/Al-SBA-15 fibers: Preparation, characterization, and applications as highly efficient catalysts for amine and imine syntheses

Article abstract of DOI:10.1039/c5ra14382a

A novel Ni/Al-SBA-15 fiber catalyst with a lamellar structure was prepared by the urea precipitation method and successfully utilized in the environmental-friendly reduction of nitro functionality. The applications of the catalyst in highly efficient one-pot amine and imine syntheses were developed; the physicochemical properties of the samples were evaluated with ICP-OES, N₂ adsorption, XRD, HRTEM, and EDX. This new catalyst highlights potent catalytic activities and a simple recycling process as an important environmentally-friendly feature.

Full text of DOI:10.1039/c5ra14382a

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Lamellar Ni/Al-SBA-15 fibers: preparation,
characterization, and applications as highly
Cite this: RSC Adv., 2015, 5, 74802
efficient catalysts for amine and imine syntheses
*
Ren Ren and Jiantai Ma
A novel Ni/Al-SBA-15 fiber catalyst with a lamellar structure was prepared by the urea precipitation method
and successfully utilized in the environmental-friendly reduction of nitro functionality. The applications of
the catalyst in highly efficient one-pot amine and imine syntheses were developed; the physicochemical
properties of the samples were evaluated with ICP-OES, N2 adsorption, XRD, HRTEM, and EDX. This new
Received 21st July 2015
Accepted 27th August 2015
DOI: 10.1039/c5ra14382a
catalyst highlights potent catalytic activities and
environmentally-friendly feature.
a simple recycling process as an important
www.rsc.org/advances
prepared by DP exhibit much smaller particle size and higher
catalytic activities.
Introduction
Despite the signicant advantages of the DP methods,
interestingly, up to now very few Ni/Al-SBA-15 catalysts prepared
by the DP method have been reported. In this paper, we
reported the utilization of the DP method for the development
of a special morphology Ni/Al-SBA-15 catalyst with high
dispersion, narrow particle distribution, and excellent thermal
stability. This catalyst combined the merits of Al-SBA-15 as
mesoporous acidic carrier and the advantages of nickel catalyst
by urea precipitation. To our best knowledge, our studies were
the rst application of this catalyst in one pot syntheses of
amines and imines. In addition, our catalytic system was highly
efficient and environmental-friendly, which made it further
promising industrial applications in future.
Al-SBA-15 mesoporous materials have been used as support
materials for Ni-based catalysts due to their excellent proper-
ties, including high surface areas, large pore volumes, suitable
acidity, ordered hexagonal pore arrays with pore diameters
between 2 and 30 nm, and high hydrothermal and thermal
stabilities. These unique features have made Al-SBA-15 mate-
rials of great industrial interest, particularly in moderate acid-
catalyzed reactions1–13 in the areas of petroleum processing
and ne chemicals production. As a result, the preparation and
application of AlSBA-15 materials have become very popular
research topics.
It is important to control the particle size and dispersion of
the metal particles, since these properties have shown great
inuence on the catalyst activity, selectivity, and lifetime.14–19
Two of the common methods to deposit active nickels are ion
exchange and impregnation. Ion exchange generates highly
dispersed catalysts but suffers from limited metal loads due to
the support exchange capacity restriction. In contrast, poorly
dispersed catalysts with high nickel loads are generally resulted
from the impregnation method, thanks to the weak metal-
support interaction. As a result, new synthetic methods with
both excellent nickel loads and dispersion have become crucial
for further catalyst development. To date, several attempts have
been reported,20–26 particularly the deposition–precipitation
method (DP).27–41 This method has been successfully applied in
the preparation of various nickel catalysts.42–48 Compared with
the products of the impregnation method, the catalysts
Experimental section
Preparation of Al-SBA-15
In a typical synthesis, 3 g P123 was dissolved in 70 mL water,
and then 45 mL 4 mol LÀ1 HCl solution was added and stirred
for 0.5 h at room temperature. Aer adding a calculated amount
of Al(NO3)3$9H2O and 6.45 g TEOS, the resulting solution was
ꢀ
stirred at 40 C for 20 h and then transferred into a polytetra-
ꢀ
uoroethylene bottle and aged at 100 C for 48 h. The product
was ltered, washed, dried at 373 K overnight, and then
calcined in air from room temperature to 823 K (1 K minÀ1, 6 h
at 823 K).
Preparation of Ni/Al-SBA-15 catalyst
The Ni/Al-SBA-15 catalyst was synthesized by the deposition–
precipitation method using Al-SBA-15 as the support and nickel
nitrate as the metallic precursor. 19.2 g Al-SBA-15 and 14.3 g
Ni(NO3)2$6H2O were dissolved in 300 mL water and stirred for
State Key Laboratory of Applied Organic Chemistry, Gansu Provincial Engineering
Laboratory for Chemical Catalysis, College of Chemistry and Chemical Engineering,
Lanzhou University, Lanzhou, 730000, PR China. E-mail: majiantai@lzu.edu.cn;
Fax: +86 931 8912577
74802 | RSC Adv., 2015, 5, 74802–74810
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
10 minutes, followed by addition of 9.8 g urea and stirred for 30 ordering in the P6mm space group. These results were consis-
min. Aer heated to 333 K and stirred for 2 h, the resulting tent with the data reported by Zhao49,50 for SBA-15. Although the
mixture was heated to 363 K over 5 h. The reaction product was intensity of characteristic peaks of Ni/Al-SBA-15 decreased
ltered, washed three times with deionized water, dried at 373 K slightly as compared with Al-SBA-15 zeolite, but the difference
overnight and then calcined in air from room temperature to of the position was not signicant. This indicated that the
823 K (1 K minÀ1, 6 h at 823 K).
hexagonal pore arrangement of the support was not obviously
destroyed during the deposition–precipitation of Ni. Addition-
ally, with the increase of the Ni load, the intensity of (100), (110)
and (200) diffraction peaks obviously decreased. Based on the
report of Park,51 this probably because the fact that along with
the increase of the Ni load, NiO number deposited in the
channel increased, which reduced the scattering intensity of
amorphous pore walls. It suggested that NiO nanoparticles were
mainly distributed in the channels of mesoporous molecular
sieves.
Characterization of the catalyst
The Al and Ni content of the catalyst were determined by
inductively coupled plasma optical emission spectroscopy (ICP-
OES). Measurements were performed on a Spectro CIROS CCD
spectrometer. The X-ray diffraction (XRD) measurements were
carried out on a Bruker AXS-D8 Advance powder diffractometer,
using CuKaÀra1diation (40 kV, 30 mA), with a scanning speed of
0.0057ꢀ min in the range of 0.5ꢀ # 2q # 8ꢀ and 0.01ꢀ minÀ1 in
the range of 5ꢀ # 2q # 70ꢀ. Nitrogen sorption isotherms were
measured at À196 ꢀC on a Micromeritics Tristar 3000 system in
static measurement mode. The samples were outgassed at 150 ꢀC
for 3 h prior to the sorption measurements. The Brunauer–
Emmett–Teller (BET) equation was used to calculate the
specic surface area from the adsorption data obtained. The
pore volume and pore size distribution were calculated by the
Barrett–Joyner–Halenda (BJH) method on the adsorption
branch of the isotherm. The high resolution HRTEM images
were obtained on a FEITecnai G2 transmission electron
microscope operated at 200 kV (FEI company). Elemental
composition data were collected by energy dispersive X-ray
spectroscopy (EDS) performed on a Tecnai G2 microscope.
Large angle XRD patterns
The powder XRD patterns in the high angle region of 5ꢀ # 2q #
70ꢀ for the samples were shown in Fig. 2. For all samples, the
broad peak at 15ꢀ–30ꢀ was ascribed to amorphous silica.52,53 The
samples 12% Ni/Al-SBA-15 showed two marked diffraction
peaks in the 2q of 37.3ꢀ and 62.9ꢀ, which corresponded to nickel
oxide. The result was consistent with the related reports in
characterizations.54–58 On the other hand, the nickel oxide
diffraction peak was not present until 12 wt% Ni was added,
indicating that the Ni species were highly dispersed on the
catalysts.
N2 adsorption–desorption studies
General procedure for reduction of nitro containing
compounds and one-pot synthesis of imines
N2 adsorption/desorption isotherms and pore size distributions
were presented in Fig. 3 and 4. The isotherms allowed calcula-
tion of specic surface area, pore volume, pore size distribution
etc. Furthermore, the position and shape of hysteresis loop also
provided useful information about the shape and size of the
pores. The isotherms (Fig. 3) were typical type IV with an H1
hysteresis loop, which was a typical adsorption for mesoporous
materials with 2D-hexagonal structure, similar to mesoporous
siliceous SBA-15.59,60 The initial increase in adsorption capacity
at low relative pressure was due to monolayer adsorption on
mesopores. The upward deviation in the range of P/P0 0.4–0.9
The reactions were carried out in a 100 mL stainless steel
reactor equipped with a magnetic stirrer. In a typical reaction
procedure, 1.0 mmol nitro containing compound (or 1.0 mmol
nitro compound, 1.2 mmol aldehyde) and 15 mL ethanol were
mixed with 15 mg Ni/Al-SBA-15 catalyst (and co-catalyst). The Ni
load was about 12 wt%. Biphenyl was used as the internal
standard. The reactor was ushed three times with H2 at 0.5
MPa and adjusted to the desired pressure. The reacting mixture
was heated to the desired temperature with stirring. Aer
reaction was complete, the reactor was cooled by an ice-water
bath and then slowly depressurized. The catalyst product was
separated, the reaction conversion rate was analyzed by GC (P.E.
Autosystem XL), and the product was conrmed by GC-MS
(Agilent 6890N/5973N).
Results and discussion
Small angle XRD patterns
Powder X-ray diffraction (XRD) was employed to assess the
structural ordering. XRD small-angle spectra of Ni/Al-SBA-15
and Al-SBA-15 are shown in Fig. 1. Although the position of
the diffraction peaks slightly changed from sample to sample,
obviously all mesoporous materials exhibited three well-
resolved peaks related to (100), (110), and (200) planes. These
Fig. 1 Low angle XRD patterns of (a) Al-SBA-15, (b) 6% Ni/Al-SBA-15,
diffraction lines were associated with long-range 2D hexagonal (c) 12% Ni/Al-SBA-15.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 74802–74810 | 74803

View Article Online
RSC Advances
Paper
Fig. 4 Pore size distribution curves of (a) Al-SBA-15, (b) 6% Ni/Al-SBA-
15, (c) 12% Ni/Al-SBA-15.
Fig. 2 Large angle XRD patterns of (a) Al-SBA-15, (b) 6% Ni/Al-SBA-15,
(c) 12% Ni/Al-SBA-15.
Table 1 Textural properties of the samples
was associated with progressive lling of mesopores. As the
relative pressure increased all isotherms displayed a sharp
increase characteristic of capillary condensation inside uniform
mesopores, which were in agreement with the XRD results.
Hysteresis loop was parallel, indicating a narrow and uniformed
pore size distribution. Compared with Al-SBA-15, P/P0 of 12%
Ni/Al-SBA-15 shied to low values, because some Ni species
were deposited on the pore surface, resulting the pore size
reduction. With the increase of the Ni content, adsorption and
desorption hysteresis area decreased.
The textural properties of all samples were presented in
Table 1. With the nickel load increase, both the surface area and
pore volume of samples decreased relatively. Al-SBA-15 exhibi-
ted larger surface areas (505.1 m2gÀ1) and pore volume (0.95
cm3gÀ1) than those of 12% Ni/Al-SBA-15.
Sample
BET (m2 gÀ1
)
Vp (cm3 gÀ1
)
Dp (nm)
12% Ni/Al-SBA-15
6% Ni/Al-SBA-15
Al-SBA-15
327.1
389.4
505.1
0.89
0.86
0.95
10.82
8.76
7.77
images in the direction perpendicular to the pore axis of Ni/Al-
SBA-15 material. Al-SBA-15 exhibited uniformed mesoporous
channels with 2D-hexagonal symmetry (P6 mm). To our
surprise, Ni/Al-SBA-15 exhibited the beautiful lamellar brous
structures (or occulent structure). The particle exhibited
straight, parallel and uniformed channels with regular inter-
vals, conrming that the one-dimensional long-range ordering
of Al-SBA-15 was retained even aer the incorporation of Ni
species into the framework. The average pore diameter was 7.68
nm, which was similar to the results of N2 adsorption/
desorption isotherms.
Meanwhile, the average pore size increased with introduc-
tion of Ni on Al-SBA-15, from 7.77 to 10.82 nm (Fig. 4), which
suggested that large amount of areas damaged parts pore when
roasting.
Fig. 6 showed the TEM-EDX images of the 12% Ni/Al-SBA-15
catalyst. The composition of this sample was conrmed by the
EDX spectrum, which revealed that Ni, Al, O, and Si were
HRTEM analysis and EDX
It is well known that the excellent structural ordering of the
mesoporous materials can be directly observed by transmission
electron microscopy. Fig. 5 showed representative HRTEM
Fig. 3 Nitrogen adsorption/desorption isotherms of (a) Al-SBA-15, (b)
6% Ni/Al-SBA-15, (c) 12% Ni/Al-SBA-15.
Fig. 5 HRTEM of 12% Ni/Al-SBA-15.
74804 | RSC Adv., 2015, 5, 74802–74810
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
Table 2 Reduction of aliphatic and aromatic nitro compoundsa
Entry Substrate
Product
Con. (%) Yieldb (%)
1
2
100
100
>99
>99
3
4
100
100
>99
>99
5
6
100
100
>99
97
Fig. 6 EDX of 12% Ni/Al-SBA-15.
7
100
100
100
100
>99
95
8
predominant species. In addition, C and Cu elements were also
detected.
9
>99
80
10
Synthesis of amines with the novel Ni/Al-SBA-15 catalyst
Amines are important intermediates in the chemistry of phar-
maceuticals, dyes, pesticides and etc.61–87 Although different
reagents and conditions have been investigated for the reduc-
tion of aromatic nitro compounds, most of these reductions
have been associated with drawbacks such as harsh reaction
conditions, use of expensive catalysts, formation of undesirable
products, requirement of an excess amount of solvents, low
yields, and etc. Additionally, very little attention has been paid
to aliphatic nitro compounds as the substrates.88–90 For the
increasing environmental and economic concerns, it is now
necessary for chemists to develop environment-friendly reac-
tions for traditional chemical transformations. Therefore, we
tested our Ni/Al-SBA-15 catalyst in the reduction of nitro-
containing compounds for the preparation of various amines.
As shown in Table 2, aliphatic amines (entries 1–6) were
obtained in near quantitative yields in all cases, conrming that
under these conditions aliphatic nitro compounds and the
product amines were compatible with Ni/Al-SBA-15. To our
relief, chain length and steric effect did not have much impact
on the formation of amines. Excellent yields of the aliphatic
amine formations (entries 1–6) were obtained. In addition, the
catalyst exhibited excellent selectivity, nitro group was reduced
while the C]C double bond was stable under the reaction
conditions (entry 4). And dechlorination was minimal (entry 6)
in our case.
11
100
>99
a
Reaction conditions: 1.0 mmol nitro compounds, 15 mL ethanol, 15
b
mg 12% Ni/Al-SBA-15, 383 K, 2.5 MPa H2, 7.5 h. GC yields.
One pot synthesis of imines with the novel Ni/Al-SBA-15
catalyst
Imines, also known as the Schiff base, are important nitrogen
sources and key intermediates in different types of reactions
utilized in biological, pharmaceutical, and industrial chemical
synthesis.91–106 Traditional formation of imines from nitroarenes
requirestwoseparatestepsinwhichthenitroareneisrstreduced
to the aniline, then isolated and subsequently condensed with the
desired carbonyl-containing compound.107–122 As an alternative,
catalytic one pot systems for imine synthesis have been under
investigations. Several catalysts including Rh6(CO)16,113 PdCl2-
(PPh3)2/SnCl2/CO,114 Pd/C/H2,96 and Ru3(CO)12/CO115 have been
reported. However, severe drawbacks still remain and challenges
have not yet been effectively met. For example, these protocols
normally require noble metal catalysts, large excess amounts of
oxidants, elevated pressures, high temperatures, which made
them far from practical for large scale synthetic purposes. Thus,
the development of efficient, environmental-friendly, and atom-
economical syntheses of imines has become a very popular
research eld. Recently one pot synthesis was suggested as a
promising solution,116–122 but the synthesis of imines using amine
and alcohol as the feedstock in most cases. Masazumi Tamura
reported the direct synthesis of imines from alcohols and amines
over CeO2 at low temperatures,116 Zhi-Xiang Wang developed
selective imine formations from alcohols and amines catalyzed by
the ruthenium(II)-PNP pincer complex,117 Taylor described a
tandem oxidation-imine formation process from alcohols with
The reaction results of aromatic nitro compounds (entries 7–
11) were also shown in Table 2. We were delight to nd that our
catalyst reduced a wide variety of nitro compounds smoothly
and efficiently. Slight dechlorination was observed in entry 8.
The dinitro compound (entry 9) was also reduced with a high
conversion and yield, and this result is better than previous
work.64 A slightly lower yield (80%) was obtained in entry 10, in
part due to the harsh experiment conditions leading to the over-
reduction of the ketone.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 74802–74810 | 74805

View Article Online
RSC Advances
Paper
active manganese oxide,119 Jaiwook Park reported one-pot chemoselectivity towards functional groups, such as C]O and
synthesis of imines and secondary amines by Pd-catalyzed NO2 (no. 15).
coupling of benzyl alcohols and primary amines,120 Sitham-
In addition, effects of various common solvents were investi-
baram reported direct catalytic synthesis of imines from alcohols gated (Table 3). C2H5OH proved to be the best. Toluene, as a non-
using manganese octahedral molecular sieves.97
polar and aprotic solvent, gave 92.54% conversion and 94.56%
To the best of our knowledge, one-pot syntheses of imines selectivity. CH2Cl2 and CH3OH, also promoted this catalytic
directly from nitro compounds and aldehydes were rare.91,123 In reactionwithlessefficiency. H2Oledtoasubstantially lowyield. In
this paper, we reported an efficient and environment-friendly our experiments later on, only ethanol was chosen based on
one-pot synthetic route for imine formations using nitro requirements of “green chemistry”, since ethanol can easily be
compounds and aldehydes as the feedstock. The amine inter- generatedfromrenewablesourcesandavailableallovertheworld.
mediates were provided in situ by the Ni/Al-SBA-15 catalyzed
The one pot synthesis of imines with the Ni/Al-SBA-15 catalyst
reduction of the nitro-containing substrates, which without directly from nitro compounds and aldehydes was speculated to
work-up, were condensed with aldehydes to yield aminals. Upon have two major steps: reduction of nitro group to amine and
the subsequent dehydration, the desired imines were obtained subsequent condensation with aldehydes with the water removal
in excellent yields.
facilitated by the catalyst. Moreover, in order to further determine
the role of Al-SBA-15 in the imine formation, we screened the
reactionofbenzaldehydewithanilineinthepresenceandabsence
of Al-SBA-15 (RT, 0.1 Mpa, 1 h). Without Al-SBA-15 was used, the
desiredproductwas obtainedina 57%yieldwhile usingAl-SBA-15
improved the reaction yield to 97%. The results conrmed that
Al-SBA-15 was an effective co-catalyst in the imine formation.
Synthesis imines with different catalyst systems
The efficacy of Ni/Al-SBA-15 for nitrobenzene reduction–
condensation reactions was compared with a number of catalyst
systems (Table 3). The 12% Ni/Al-SBA-15 catalyst exhibited the
highest activity (no. 1–15). Other metal catalysts such as 7.5%
Ru/C, 10% Pd/C, and 10% RANEY® nickel were found to be
feeble under the same conditions (no. 7–15).
One-pot reduction–condensation reactions
When Pd/C was used (no. 11–14), no desired imine was The optimized conditions were then applied to more nitro
obtained (only benzyl alcohol, aniline, and N-benzylaniline were compounds and aldehydes to extend the scope of the method.
produced), which was basically consistent with the previous As shown in Table 4 (entries 12 and13), imine formations from
reports.91 Undertheconditions (no. 9and10), somedesiredimine aliphatic nitro compounds and benzaldehyde have been inves-
products were generated with a slightly low conversions and tigated. A wide range of nitro compounds were tested with the
selectivities. Al-SBA-15 was found to be a good co-catalyst, which Ni/Al-SBA-15 catalyst under the optimized conditions and
could serve as a Lewis acid in the imine formation (no. 9 and 10). almost all desired transformations were achieved with excellent
RANEY® nickel was pyrophoric and did not show any conversion and in satisfactory yields.
Table 3 Comparison of catalytic activities with different catalytic systemsa
No.
Catalyst
Co-catalyst
Solvent
Time (h)
Pres. (Mpa)
Temp. (K)
Con.b
Sel.c
1
2
3
4
5
6
7
8
12% Ni/Al-SBA-15
12% Ni/Al-SBA-15
12% Ni/Al-SBA-15
12% Ni/Al-SBA-15
12% Ni/Al-SBA-15
12% Ni/SBA-15
7.5% Ru/C
7.5% Ru/C
7.5% Ru/C
7.5% Ru/C
10% Pd/C
—
—
—
—
—
—
—
—
C2H5OH
CH3OH
CH2Cl2
Toluene
H2O
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
8
8
8
8
8
8
8
8
8
8
8
8
8
6
1
1.4
1.4
1.4
1.4
1.4
1.4
0.1
1.4
1.4
1.4
1.4
1.4
1.4
0.1
0.1
378
378
378
378
378
378
298
323
378
378
378
378
298
298
298
98.54
98.92
90.12
92.54
35.31
98.57
0
99.47
98.87
92.17
94.56
93.54
89.42
0
0
0
9
—
25.79
34.67
100
100
100
79.67
79.34
0
0
0
10
11
12
13
14
15
Al-SBA-15
Al-SBA-15
—
Al-SBA-15
—
10% Pd/C
10% Pd/C
10% Pd/C
10% RANEY® nickel
100
100
0.26
0.16
—
a
b
Reaction condition: 1.0 mmol nitrobenzene, 1.2 mmol benzaldehyde, 15 mL solvent,15 mg catalyst, 3 mg co-catalyst. Conversion of
nitrobenzene. c Selectivity to imine.
74806 | RSC Adv., 2015, 5, 74802–74810
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
As shown in Table 4 (entries 14–19), imine formations from
RSC Advances
aromatic nitro compounds and a variety of aldehydes have been
investigated too. A series of aromatic aldehydes were utilized
and all imines were obtained in excellent conversion and yields,
which demonstrated the method possessed excellent functional
group tolerance.
Interestingly, while electronic effects from the substituents
on both nitroarenes and aromatic aldehydes had little inuence
on the overall reaction yields, steric hinderance around the
nitro group seemed to play an important role in the imine
formations (entries 17–19), with the decreasing of steric effect,
the yields increased.
Proposed reaction mechanism
Fig. 7 (a) Hysteresis curves; (b) magnetic separation.
Imine synthesis proceeded via two mechanistically distinct reac-
tionstepspromotedbyasingleNicatalyst(Ni/Al-SBA-15). Possible
mechanistic studies of the reaction were also illustrated in Catalyst regeneration and stability
Scheme1. Therst stepwas the reduction ofthe nitro compounds
The Ni/Al-SBA-15 catalyst displayed superparamagnetic
behavior and no remanence at room temperature in Fig. 7a.
These indicated our Ni/Al-SBA-15 catalyst can be easily
recovered and reused. In Fig. 7b, the Ni/Al-SBA-15 catalyst
showed strong magnetism, as a result, it can simply be sepa-
rated from reaction mixture in a relatively low magnetic eld
with a small laboratory magnet and recovered quantitatively by
simple ltration. Regeneration of the catalyst was achieved by
rinsing with ethanol. More interestingly, aer magnetic
recovery, the catalyst can be dispersed ready for further use.
to the corresponding amines. The second step involved a nucle-
ophilic attack on the aldehyde carbonyl group by the in situ
generated amines. Ni/Al-SBA-15 provides Lewis acidic sites for
hydrogen in order to facilitate the catalytic imine formation.
Imine synthesis is generally a facile reaction due to the good
electrophilic properties of carbonyls and nucleophilic proper-
ties of the amine groups; however, for imines which are difficult
to synthesize due to the decrease in electrophilicity/
nucleophilicity of the carbonyl/amine groups a catalyst such
as Ni/Al-SBA-15 is required.
Table 4 One-pot reduction–condensation reactions of aliphatic and aromatic nitro compoundsa
Entry
Substrate
By-substrate
Product
Con. (%)
Yieldb (%)
12
13
100
100
99
99
14
15
99
98
99
100
16
17
18
100
95
73
84
89
96
19
98
91
a
Reaction conditions: 1.0 mmol nitro compounds, 1.2 mmol aldehydes, 15 mL ethanol, 15 mg Ni/Al-SBA-15, 378 K, 1.4 MPa H2, 8 h. b GC yields.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 74802–74810 | 74807

View Article Online
RSC Advances
Paper
Table 5 Ni/Al-SBA-15 catalyst recycling experimentsa
Notes and references
1 W. Hu, Q. Luo, Y. Su, L. Chen, Y. Yue, C. Ye and F. Deng,
Microporous Mesoporous Mater., 2006, 92, 22–30.
2 A. J. J. Koekkoek, J. A. Rob van Veen, P. B. Gerrtisen,
P. Giltay, P. C. M. M. Magusin and E. J. M. Hensen,
Microporous Mesoporous Mater., 2012, 151, 34–43.
3 G. M. Kumaran, S. Garg, K. Soni, M. Kumar,
J. K. G. D. Sharma, K. S. R. Rao and G. M. Dhar,
Microporous Mesoporous Mater., 2008, 114, 103–109.
4 R. V. Grieken, J. M. Escola, J. Moreno and R. Rodriguez,
Appl. Catal., A, 2006, 305, 176–188.
Cycle no.
1st
98
2nd
98
3rd
97
4th
95
Yieldb (%)
a
Reaction condition: 1.0 mmol nitrobenzene, 1.2 mmol benzaldehyde,
15 mL ethanol, 15 mg Ni/Al-SBA-15, 378 K, 1.4 MPa H2, 8 h. b GC yields.
5 H. Wang, Y. Liu and T. J. Pinnavaia, J. Phys. Chem. B, 2006,
110, 4524–4526.
6 K. S. Triantafyllidis, A. A. Lappas, I. A. Vasalos, H. Wang,
Y. Liu and T. J. Pinnavaia, Catal. Today, 2006, 112, 33–36.
7 S. Zeng, J. Blanchard, M. Breysse, Y. Shi, X. Shu, H. Nie and
D. Li, Microporous Mesoporous Mater., 2005, 85, 297–304.
8 C. Nie, L. Huang, D. Zhao and Q. Li, Catal. Lett., 2001, 71,
117–125.
9 T. Sano, T. Nijmi, T. Miyazaki, S. Tsubaki, Y. Oumi and
T. Uozumi, Catal. Lett., 2001, 71, 105–110.
10 Y. Xia and R. Mokaya, J. Mater. Chem., 2004, 14, 3427–3435.
11 J. M. Rosenholm, T. Czuryszkiewicz, F. Kleitz,
J. B. Rosenholm and M. Linden, Langmuir, 2007, 23,
4315–4323.
12 D. G. Poduval, J. A. R. van Veen, M. S. Rigutto and
E. J. M. Hensen, Chem. Commun., 2010, 46, 3466–3468.
13 E. J. M. Hensen, D. G. Poduval, D. A. J. M. Ligthart,
J. A. R. van Veen and M. S. Rigutto, J. Phys. Chem. C, 2010,
114, 8363–8374.
Scheme 1 The proposed mechanism for the one pot imine synthesis.
Nickel leaching of the catalyst was also studied. The Ni
loading of the regenerated catalyst (aer four cycles) was about
11.6 wt% (slightly lower than the fresh catalyst) and no obvious
leaching of the catalyst occurred under our reaction conditions.
For practical applications of heterogeneous systems, the
lifetime of the catalyst and its reusability are two important
concerns. To clarify this issue, we established a series of
experiments using the recycled Ni/Al-SBA-15 catalyst. To our
satisfaction, the results demonstrated only slight decrease in
the reaction yield (Table 5) aer four recycles. In addition, the
ease of catalyst reuse provided our catalyst signicant advan-
tages over commercial RANEY® nickel catalysts.
´
14 P. Castellazzi, G. Groppi, P. Forzatti, A. Baylet, P. Marecot
and D. L. Duprez, Catal. Today, 2010, 155, 18–26.
15 A. M. Banerjee, M. R. Pai, R. Tewari, N. Raje, A. K. Tripathi,
S. R. Bharadwaj and D. Das, Appl. Catal., B, 2015, 162, 327–
337.
16 R. M. M. Abbaslou, J. Soltan and A. K. Dalai, Appl. Catal., A,
2010, 379, 129–134.
17 R. M. Rioux, H. S. J. D. Hoefelmeyer, P. Yang and
G. A. Somorjai, J. Phys. Chem. B, 2005, 109, 2192–2202.
18 I. O. Costilla, M. D. Sanchez and C. E. Gigola, Appl. Catal., A,
2014, 478, 38–44.
19 M. P. Casalettoa, A. Longo, A. M. Venezia, A. Martorana and
A. Prestianni, Appl. Catal., A, 2006, 302, 309–316.
20 Z. Wu, S. Ge, M. Zhang, W. Li and K. Tao, J. Colloid Interface
Sci., 2009, 330, 359–366.
21 X. Hao, Y. Zhang, J. Wang, W. Zhou, C. Zhang and S. Liu,
Microporous Mesoporous Mater., 2006, 88, 38–47.
22 Y. Kuang, Y. Cui, Y. Zhang, Y. Yu, X. Zhang and J. Chen,
Chem.–Eur. J., 2012, 18, 1522–1527.
23 M. Rana, Y. Liu, W. Chu, Z. Liu and A. Borgna, Catal.
Commun., 2012, 27, 69–72.
Conclusions
In this work, a novel and potent Ni/Al-SBA-15 catalyst was
prepared and successfully applied in the environment-friendly
reduction of nitro-containing compounds and the synthesis of
imines by the one-pot reduction–condensation sequence. In
addition, the catalyst was able to maintain high catalytic reac-
tivity aer multiple recycles and can easily be isolated and
regenerated. These interesting features suggested that our
catalyst had good prospects for further industrial applications
and large-scale green production of imines and amines.
24 K. Song, H. Zhang, Y. Zhang, Y. Tang and K. Tang, J. Catal.,
2013, 299, 119–128.
Acknowledgements
This research was supported by the Fundamental Research
Funds for the Central Universities (grant no. lzujbky-2013-234
and 861605).
25 R. Baran, I. I. Kaminska, A. Srebowata and S. Dzwigaj,
Microporous Mesoporous Mater., 2013, 169, 120–127.
74808 | RSC Adv., 2015, 5, 74802–74810
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
26 F. Menegazzo, M. Signoretto, G. Frison, F. Pinna,
G. Strukul, M. Manzoli and F. Boccuzzi, J. Catal., 2012,
290, 143–150.
27 S. Chytil, W. R. Glomm and E. A. Blekkan, Catal. Today,
2009, 147, 217–223.
53 H. Liu, H. Wang, J. Shen, Y. Sun and Z. Liu, Appl. Catal., A,
2008, 337, 138–147.
54 D. J. Lensveld, G. MesuJ and A. J. Dillen, Microporous
Mesoporous Mater., 2001, 44–45, 401–407.
55 M. A. Gondal, T. A. Saleh and Q. A. Drmosh, Appl. Surf. Sci.,
2012, 258, 6982–6986.
´
28 E. Rıo, G. Blanco, S. Collins, M. L. Haro, X. Chen,
J. J. Delgado, J. J. Calvino and S. Bernal, Top. Catal., 2011,
54, 931–940.
56 K. V. R. Chary, P. V. R. Rao and V. V. Rao, Catal. Commun.,
2008, 9, 886–893.
29 A. J. Binder, Z. Qiao, G. M. Veith and S. Dai, Catal. Lett.,
2013, 143, 1339–1345.
57 S. Ren, P. Zhang, H. Shui, Z. Lei, Z. Wang and S. Kang,
Catal. Commun., 2010, 12, 132–136.
30 E. Rio and M. L. Haro, Chem. Commun., 2013, 49, 6722–
6724.
58 A. Albarazi, M. E. Galvez and P. D. Costa, Catal. Commun.,
2015, 59, 108–112.
31 S. S. R. Putluru, L. Schill, S. Mossin, A. D. Jensen and
R. Fehrmann, Catal. Lett., 2014, 144, 1170–1177.
32 A. Sandoval, C. Louis and R. Zanella, Appl. Catal., B, 2013,
140–141, 363–377.
59 Z. Luan, M. Hartmann and D. Zhao, Chem. Mater., 1999, 11,
1621–1627.
60 Z. Luan, E. M. Maes and P. A. W. van der Heide, Chem.
Mater., 1999, 11, 3680–3686.
33 S. S. R. Putluru, L. Schill, A. D. Jensen, B. Siret, F. Tabaries
and R. Fehrmann, Appl. Catal., B, 2015, 165, 628–635.
34 H. Xu, W. Chu, J. Luo and M. Liu, Catal. Commun., 2010, 11,
812–815.
35 P. Miquel, P. Granger, N. Jagtap, S. Umbarkar, M. Dongare
and C. Dujardin, J. Mol. Catal. A: Chem., 2010, 322, 90–97.
36 S. Ajaikumar, J. Ahlkvist, W. Larsson, A. Shchukarev,
A. R. Leino, K. Kordas and J. P. Mikkola, Appl. Catal., A,
2011, 392, 11–18.
61 S. Enthaler, Catal. Lett., 2011, 141, 55–61.
62 D. He, H. Shi, Y. Wu and B. Xu, Green Chem., 2007, 9, 849–
851.
63 R. J. J. Rahaim and R. E. J. Maleczka, Org. Lett., 2005, 7,
5087–5090.
64 Y. Chen, J. Qiu, X. Wang and J. Xiu, J. Catal., 2006, 242, 227–
230.
65 P. L. Gkizis, M. Stratakis and I. N. Lykakis, Catal. Commun.,
2013, 36, 48–51.
37 S. Chytil, W. R. Glomm, I. Kvande, T. Zhao, J. C. Walmsley,
E. A. Blekkan, Top. Catal., 2007, 45(1–4), 93–99.
38 X. Lu, G. Zhao and Y. Lu, Catal. Sci. Technol., 2013, 3, 2906–
2909.
66 Z. Zhao, H. Yang, Y. Li and X. Guo, Green Chem., 2014, 16,
1274–1281.
¨
¨
67 H. Goksua, H. Can, K. Sendil, M. S. Gultekina and
¨
O. Metina, Appl. Catal., A, 2014, 488, 176–182.
39 S. S. R. Putluru, L. Schill, D. Gardini, S. Mossin,
J. B. Wagner, A. D. Jensen and R. Fehrmann, J. Mater. Sci.,
2014, 49, 2705–2713.
68 F. Zamani and S. Kianpour, Catal. Commun., 2014, 45, 1–6.
69 U. Sharma, P. Kumar, N. Kumar, V. Kumar and B. Singh,
Adv. Synth. Catal., 2010, 352, 1834–1840.
40 F. Zhong, Y. Xiao, X. Weng, K. Wei, G. Cai, Y. Zheng and
Q. Zheng, Catal. Lett., 2009, 133, 125–133.
70 R. G. de Noronha, C. C. Romao and A. C. Fernandes, J. Org.
Chem., 2009, 74, 6960–6964.
41 K. Qian, J. Fang, W. Huang, B. He, Z. Jiang, Y. Ma and
S. Wei, J. Mol. Catal. A: Chem., 2010, 320, 97–105.
42 M. K. van der Lee, A. Jos van Dillen, J. H. Bitter and K. P. de
Jong, J. Am. Chem. Soc., 2005, 127, 13573–13582.
71 X. Lou, L. He, Y. Qian, Y. Liu, Y. Cao and K. Fan, Adv. Synth.
Catal., 2011, 353, 281–286.
72 A. Saha and B. Ranu, J. Org. Chem., 2008, 73, 6867–6870.
73 D. Cantillo, M. M. Moghaddam and C. O. Kappe, J. Org.
Chem., 2013, 78, 4530–4542.
74 M. L. Kantam, R. Chakravarti, U. Pal, B. Sreedhar and
S. Bhargava, Adv. Synth. Catal., 2008, 350, 822–827.
75 S. Farhadi and F. Siadatnasab, J. Mol. Catal. A: Chem., 2011,
339, 108–116.
76 U. Sharma, P. K. Verma, N. Kumar, V. Kumar, M. Bala and
B. Singh, Chem.–Eur. J., 2011, 17, 5903–5907.
´
´
43 R. Gomez-Reynoso, J. Ramırez, R. Nares, R. Luna and
F. Murrieta, Catal. Today, 2005, 107–108, 926–932.
44 P. Burattin, M. Che and C. Louis, J. Phys. Chem. B, 2000, 104,
10482.
45 R. Nares, J. Ramirez, A. Gutierrez, C. Louis and T. Klimova,
J. Phys. Chem. B, 2002, 106, 13287–13293.
46 R. Nares, Ph.D. Thesis, Unam, Mexico, 2003.
47 R. Nares, J. Ramirez, A. G. Alejandre and R. Cuevas, Ind.
Eng. Chem. Res., 2009, 48, 1154–1162.
77 P. Veerakumar, M. Velayudham, K. L. Lu and S. Rajagopal,
Appl. Catal., A, 2012, 439–440, 197–205.
48 J. Cao, Z. Yan, Q. Deng, Z. Yuan, Y. Wang, G. Sun, X. Wang,
B. Hari and Z. Zhang, Catal. Sci. Technol., 2014, 4, 361–368.
49 D. Zhao, J. Feng, Q. Huo, N. Melosh, G. H. Fredrickson,
B. F. Chmelka and G. D. Stucky, Science, 1998, 279, 548–552.
50 D. Zhao, Q. Huo and J. Feng, J. Am. Chem. Soc., 1998, 120,
6024–6036.
78 H. Wang, J. Yan, W. Chang and Z. Zhang, Catal. Commun.,
2009, 10, 989–994.
79 H. Min, S. Lee, M. Park, J. Hwang, H. Jung and S. Lee, J.
Organomet. Chem., 2014, 755, 7–11.
80 I. Pogorelic, M. F. Litvic, S. Merkas, G. Ljubic, I. Cepanec
and M. Litvi, J. Mol. Catal. A: Chem., 2007, 274, 202–207.
´
51 Y. Park, T. Kang and P. Kim, J. Colloid Interface Sci., 2006,
295, 464–471.
81 M. Baron, E. Metay, M. Lemairea and F. Popowycz, Green
Chem., 2013, 15, 1006–1015.
52 N. A. Dhas, A. Zaban and A. Gedanken, Chem. Mater., 1999,
11, 806–813.
82 D. Shah and H. Kaur, J. Mol. Catal. A: Chem., 2014, 381, 70–
76.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 74802–74810 | 74809

View Article Online
RSC Advances
Paper
83 R. K. Rai, A. Mahata, S. Mukhopadhyay, S. Gupta, P. Li, 104 S. Guizzetti and M. Benaglia, Eur. J. Org. Chem., 2010, 5529–
K. T. Nguyen, Y. Zhao, B. Pathak and S. K. Singh, Inorg.
Chem., 2014, 53, 2904–2909.
84 R. J. Kalbasi, A. A. Nourbakhsh and F. Babaknezhad, Catal.
Commun., 2011, 12, 955–960.
5541.
105 A. Grirrane, A. Corma and H. Garcia, J. Catal., 2009, 264,
138–144.
106 V. Macho, M. Kralik, J. Hudec and J. Cingelova, J. Mol.
´
85 U. Sharma, N. Kumar, P. K. Verma, V. Kumar and B. Singh,
Green Chem., 2012, 14, 2289–2293.
Catal. A: Chem., 2004, 209, 69–73.
107 K. Tanaka and R. Shiraishi, Green Chem., 2000, 2, 272–273.
86 A. Corma, P. Concepcion and P. Serna, Angew. Chem., Int. 108 K. P. Guzen, A. S. Guarezemini, A. T. G. Orfao, R. Cella,
Ed., 2007, 46, 7266–7269.
87 C. G. Morales-Guio, I. Yuranov and L. Kiwi-Minsker, Top.
Catal., 2014, 57, 1526–1532.
88 A. Akita, M. Inbia, H. Uchida and A. Ohta, Synthesis, 1977,
792–794.
89 H. N. Borah, D. Prajapati, J. S. Sandhu and A. C. Ghosh,
Tetrahedron Lett., 1994, 35, 3167–3170.
90 D. C. Gowda, B. Mahesh and S. Gowda, Indian J. Chem., Sect.
B: Org. Chem. Incl. Med. Chem., 2001, 40, 75–77.
91 A. L. Korich and T. S. Hughes, Synlett, 2007, 2602–2604.
92 K. P. Guzen, A. S. Guarzemini, A. T. G. Orfao, R. Cella,
C. M. P. Pereira and H. A. Stefani, Tetrahedron Lett., 2007,
48, 1845–1847.
C. M. P. Pereira and H. A. Stefani, Tetrahedron Lett., 2007,
48, 1845–1848.
109 A. K. Chakraborti, S. Bhagat and S. Rudrawar, Tetrahedron
Lett., 2004, 45, 7641–7644.
110 H. Naeimi, F. Salimi and K. Rabiei, J. Mol. Catal. A: Chem.,
2006, 260, 100–104.
111 C. K. Z. Andrade, S. C. S. Takada, L. M. Alves,
J. P. Rodrigues, P. A. Z. Suarez, R. F. Brandao and
V. C. D. Soares, Synlett, 2004, 12, 2135–2138.
112 M. Gopalakrishnan, P. Sureshkumar, V. Kanagarajan,
J. Thanusu and R. Govindaraju, J. Chem. Res., 2005, 5,
299–303.
113 A. F. M. Iqbal, J. Org. Chem., 1972, 37, 2791–2795.
93 L. L. Santos, P. Serna and A. Corma, Chem.–Eur. J., 2009, 15, 114 M. Akazome, T. Kondo and Y. Watanabe, J. Org. Chem.,
8196–8203.
1994, 59, 3375–3380.
94 H. Choi and M. P. Doyle, Chem. Commun., 2007, 745–747.
95 S. Kegnæs, J. Mielby, U. V. Mentzel, C. H. Christensen and
A. Riisager, Green Chem., 2010, 12, 1437–1441.
96 M. G. Banwell, D. W. Lupton, X. Ma, J. Renner and
M. O. Sydnes, Org. Lett., 2004, 6, 2741–2744.
97 S. Sithambaram, R. Kumar, Y. Son and S. L. Suib, J. Catal.,
2008, 253, 269–277.
98 A. Zanardi, J. A. Mata and E. Peris, Chem.–Eur. J., 2010, 16,
10502–10506.
99 H. A. Ho, K. Manna and A. D. Sadow, Angew. Chem., Int. Ed.,
2012, 51, 8607–8610.
115 M. Akazome, T. Kondo and Y. Watanabe, J. Org. Chem.,
1993, 58, 310–312.
116 M. Tamura and K. Tomishige, Angew. Chem., Int. Ed., 2015,
54, 864–867.
117 H. Li, X. Wang, M. Wen and Z. Wang, Eur. J. Inorg. Chem.,
2012, 5011–5020.
118 H. Tian, X. Yu, Q. Li, J. Wang and Q. Xu, Adv. Synth. Catal.,
2012, 354, 2671–2677.
119 L. Blackburn and R. J. K. Taylor, Org. Lett., 2001, 3, 1637–
1639.
120 M. S. Kwon, S. Kim, S. Park, W. Bosco, R. K. Chidrala and
J. Park, J. Org. Chem., 2009, 74, 2877–2879.
121 W. Cui, H. Zhu, M. Jia, W. Ao, Y. Zhang and B. Zhaorigetu,
React. Kinet., Mech. Catal., 2013, 109, 551–562.
100 S. Murahashi, Y. Okano, H. Sato, T. Nakae and N. Komiya,
Synlett, 2007, 11, 1675–1678.
101 A. Simion, C. Simion, T. Kanda, S. Nagashima, Y. Mitoma,
T. Yamada, K. Mimura and M. Tashiro, J. Chem. Soc., Perkin 122 H. Sun, F. Su, J. Ni, Y. Cao, H. He and K. Fan, Angew. Chem.,
Trans. 1, 2001, 2071–2078. Int. Ed., 2009, 48, 4390–4393.
102 N. E. Borisova, M. D. Reshetova and Y. A. Ustynyuk, Chem. 123 Y. Xiang, Q. Meng, X. Li and J. Wang, Chem. Commun.,
Rev., 2007, 107, 46–79.
2010, 46, 5918–5920.
103 J. Barluenga, F. Aznar and C. Valdes, Angew. Chem., Int. Ed.,
2004, 43, 343–345.
74810 | RSC Adv., 2015, 5, 74802–74810
This journal is © The Royal Society of Chemistry 2015