Colloidal nickel(0)-carboxymethyl cellulose particles: A biopolymer-inorganic catalyst for hydrogenation of nitro-aromatics and carbonyl compounds

Article abstract of DOI:10.1016/j.catcom.2012.11.025

Colloidal solution of nickel(0) in carboxymethyl cellulose showed good catalytic efficiency in hydrogenation of aromatic nitro compounds, as well as aliphatic and aromatic ketones in aqueous medium yielding the respective aromatic amines and alcohols in excellent yield along with moderate to good reusability of the catalyst. The catalyst was isolated and characterized by powder XRD, EDX, SEM and TEM studies. The active phase of the catalyst consists of nickel nanoparticles entrapped in carboxymethyl cellulose (Col-Ni-CMC Nps). The ecofriendly synthesis was performed in water at room temperature by NaBH₄ reduction of nickel chloride in the presence of sodium carboxymethyl cellulose (CMC).

Full text of DOI:10.1016/j.catcom.2012.11.025

Catalysis Communications 32 (2013) 92–100
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Colloidal nickel(0)-carboxymethyl cellulose particles: A biopolymer-inorganic
catalyst for hydrogenation of nitro-aromatics and carbonyl compounds
a
a
a
b
c
Mohamed Anouar Harrad , Brahim Boualy , Larbi El Firdoussi , Ahmad Mehdi , Claudio Santi ,
d
e
a,
Stefano Giovagnoli , Morena Nocchetti , Mustapha Ait Ali ⁎
Equipe de Chimie de Coordination et Catalyse, Département de Chimie, Faculté des Sciences Semlalia, Université Cadi Ayyad, B.P. 2390, 40001 Marrakech, Morocco
Institut Charles Gerhardt Montpellier, UMR 5253, Chimie Moléculaire et Organisation du Solide, Université Montpellier. Place E. Bataillon, 34095 Montpellier Cedex 5, France
Dipartimento di Chimica e Tecnologia del Farmaco, Laboratorio di Catalisi e Green Chemistry Università di Perugia, Via Del Liceo 1, 06134 Perugia, Italy
University of Perugia, Chemistry and Drug Technology, Via Del Liceo 1, 06134 Perugia, Italy
Sezione di Chimica Inorganica, Dipartimento di Chimica Via Elce di Sotto 8 Perugia, Italy
a
b
c
d
e
a r t i c l e i n f o
a b s t r a c t
Article history:
Colloidal solution of nickel(0) in carboxymethyl cellulose showed good catalytic efficiency in hydrogena-
tion of aromatic nitro compounds, as well as aliphatic and aromatic ketones in aqueous medium yielding
the respective aromatic amines and alcohols in excellent yield along with moderate to good reusability of
the catalyst. The catalyst was isolated and characterized by powder XRD, EDX, SEM and TEM studies. The
active phase of the catalyst consists of nickel nanoparticles entrapped in carboxymethyl cellulose
Received 7 September 2012
Received in revised form 23 November 2012
Accepted 26 November 2012
Available online 3 December 2012
(
Col-Ni-CMC Nps). The ecofriendly synthesis was performed in water at room temperature by NaBH
4
reduc-
Keywords:
Biopolymer
tion of nickel chloride in the presence of sodium carboxymethyl cellulose (CMC).
Colloidal Ni-CMC Nps
Hydrogenation
Nitroaromatics
Carbonyl compounds
Reusability
© 2012 Elsevier B.V. All rights reserved.
1
. Introduction
availability and much reduced toxicity over synthesized polymers. In ad-
dition, similarly to some enzyme promoted reactions, the tridimensional
structure of the biopolymer could modulate the activity and the selectiv-
ity of the catalyst. These properties increase the interest for some natural
polymers as a new kind of polymeric ligands for transition metals.
In this paper, we report that nickel(0) can be entrapped in a biopoly-
mer matrix (carboxymethyl cellulose) starting from cheap precursors
Nickel nanoparticles, in catalytic applications, have recently gained
significance and they have been used for selective oxidative coupling
of thiols [1], reduction of ketones [2], aldehydes [3], olefins [4], and aro-
matic nitro compounds [5]. general problem of metal nanoparticles is
associated to their tendency to undergo agglomeration and oxidation, as-
sociate to a consequent enhancement of the particle size, and therefore,
reducing the catalytic activity [6]. Two general strategies have been
developed to stabilize metal nanoparticles: supporting the metal on suit-
able solid surfaces or by using suitable ligands. Other possibilities for the
production of new nickel based catalyst can be developed stabilizing nick-
el nanoparticles by encapsulation in a polymer to combine the unique cat-
alytic properties of nickel with the reaction shape-selectivity effects.
Polymer-supported transition metal catalysts have attracted considerable
attention over the past two decades. There are many excellent reviews [7]
and monographs [8] concerning the advances and achievements in this
field. In most of these works, synthetic polymers were employed as li-
gands for metals and just few examples have been reported on the appli-
cation of natural polymers, such as chitosan, cellulose and starch [9]. It is
well known that natural polymers have the advantages of cheapness, easy
4
(Scheme 1) using a simple experimental protocol, and NaBH as a reduc-
ing agent. The resulting selective and active hydrogenation catalyst, of
aromatic nitro compounds and aliphatic as well as aromatic ketones
in aqueous medium, can replace Raney nickel and other common het-
erogeneous catalysts such as Pt and Pd, reducing the costs and the
toxic waste production with respect to catalyst that are usually
employed in excess. Our method is also expected to result in the follow-
ing advantages: (a) sodium carboxymethyl cellulose acts as a biode-
gradable polymer; (b) water can be used as a solvent; (c) and the
catalyst can be easily reused for several times.
2. Experimental
2.1. Preparation of Col-Ni-CMC Nps catalyst
Col-Ni-CMC Nps catalyst was synthesized following our previously
⁎
Corresponding author. Tel.: +212 524 434649; fax: +212 524 437408.
E-mail addresses: aitali@uca.ma, m_aitali@hotmail.com (M. Ait Ali).
reported procedure with a slight modification [10]. Sodium borohydride
1566-7367/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.catcom.2012.11.025

M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
93
CH COONa
2
O
O
O
+
NiCl2
HO
OH
CMCNa
NaBH4
NH2
NO2
or
R
R
or
O
Ni(0)
CMC
OH
R'
R
R'
R
H2 / H O (H O / MeOH or EtOH)
2
2
H2 (1-40 bars)
Room temperature
Scheme 1. Catalytic hydrogenation.
(
2
25 mg) was added to aqueous solution of CMC surfactant (25 mg, in
5 mL H O). The obtained solution was quickly added under vigorous
magnetic stirring to NiCl ·6H O (250 mg, 1.05 mmol) dissolved in
O (25 mL). The initial green solution darkened rapidly indicating
2.3. General procedure for hydrogenation under atmospheric hydrogen
pressure
2
2
2
H
2
A 25 mL round bottom flask, charged with 8 mL of freshly pre-
the metal reduction and the formation of nickel(0) nanoparticles. In
order to characterize the active phase of catalyst, we have isolated the
resulting Ni nanoparticles by filtration of the obtained black suspension.
The residue was washed several times with water, ethanol and acetone.
Finally, the product was dried in air at 100 °C for 24 h.
pared aqueous colloidal suspension of Ni-CMC catalyst (from 40 mg
of NiCl ·6H O), was connected with a gas burette (500 mL) and a
2 2
flask to balance the pressure. The flask was closed by a septum, and
the system was filled with hydrogen. The nitroarene compound
([substrate]/[metal]=100) in 2 mL of MeOH, was injected through
the septum and the mixture was stirred at room temperature. The re-
action was monitored by the volume of gas consumed and by gas
chromatography. At the end of the reaction, the residue was extracted
with diethyl ether (3×25 mL). The organic layer was dried over
2
.2. Characterization
TEM observations were carried out at 100 kV (JEOL 1200 EXII).
2 4
Na SO and the solvent was removed under reduced pressure. Pure
Samples were prepared by embedding the hybrid material in AGAR
00 resin, followed by ultramicrotomy techniques and deposition
on copper grids. Size of Ni crystallites was estimated by operating
0 random counts by image analysis and the mean diameter was
product was obtained by column chromatography over silica gel
using hexane/ethyl acetate as eluent.
1
5
2.4. General procedure for hydrogenation under hydrogen pressure
measured by the Feret's method [11].
X-ray diffraction (XRD) measurements were also carried out and
XRD diagrams were collected in the θ–θ mode using a Philips X'Pert
MPD diffractometer using Cu Ka radiation (λ=1.54178 Å) at room
temperature (25 °C); 2θ=4–80. The samples were dried under vacu-
um and kept under an argon atmosphere. Particle size of Ni crystal-
lites was calculated by using the Debye–Scherrer's equation.
The contents of nickel in the catalyst were determined by a Varian
The stainless steel autoclave was charged with the previously pre-
pared aqueous suspension of Col-Ni-CMC Nps (8 mL, from 40 mg
of NiCl ·6H O and 10 mL, from 50 mg of NiCl ·6H O) for ketone hy-
drogenation. The appropriate nitro-aromatic ([substrate]/[metal]=
100) in 2 mL of MeOH, was added into the autoclave and dihydrogen
was admitted to the system at constant pressure (10 to 40 bars). The
mixture was stirred until the reaction was finished. Samples for gas
chromatographic analysis were removed from time to time. The resi-
due was extracted with diethyl ether (3×25 mL). The organic layer
2
2
2
2
7
00-Es series inductively coupled plasma atomic emission spectrom-
eter (ICP-AES). Samples were extracted in HNO 1 M solution and a
–50 mg/mL Ni standard range was employed for calibration.
The NMR spectra were recorded on a Bruker spectrometer
300 MHz Avance) in a mixture of CDCl . Chemical shifts are reported
3
5
2 4
was dried over Na SO and the solvent was removed under reduced
pressure Pure products were obtained by column chromatography
over silica gel using hexane/ethyl acetate as eluent.
(
3
as δ values (ppm) relative to TMS as a standard and the coupling con-
stants J values are given in Hz. All the spectroscopic data of the reac-
tion products were compared with those reported in the literature
and/or commercially available.
3. Results and discussion
The catalytically active Ni-CMC particles were formed by
supporting the obtained Ni(0) colloids prepared on sodium CMC.
The preparation of the aqueous suspension in catalytic reaction con-
ditions was optimized by establishing the amount of CMC able to
support Ni colloids without provoking large aggregates. Specifically,
the hydrogenation of nitrobenzene into aniline in standard condi-
tions (20 °C, 1 bar H , [substrate]/[Rh]=100) was studied with dif-
2
ferent concentrations (C g/L) of CMC (0.25, 0.5, 1.0, 1.5). A polymer
concentration of 0.5 g/L was sufficient to maintain stable Ni colloids.
The reaction mixtures were analyzed on a Trace GC Thermo
Finnigan chromatograph equipped with FID detector. GC parameters
for capillary column BP (25 m×0.25 mm, SGE): injector 250 °C; de-
−
1
tector 250 °C; oven 70 °C for 5 min then 3 °C min
until 250 °C for
−
1
3
0 min; column pressure 20 kPa, column flow 6.3 mL min ; linear
velocity 53.1 cm s ; and total flow 138 mL min−1. Column chro-
matography was performed on silica gel (30–60 μm). All solvents
were distilled and dried before using.
−1

94
M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
On the contrary, concentrations b0.5 g/L led to precipitation after ca-
talysis, whereas CMC concentrations >0.5 g/L decreased consider-
ably the yield of aniline. Therefore, 0.5 g/L was established as the
CMC concentration for the stable and reproducible synthesis of Ni
nanoparticles and their use in the hydrogenation of nitrobenzenes,
aliphatic and aromatic ketones under aqueous conditions.
Since CMC could form complexes with divalent metal ions due to their
high number of coordinating functional groups (hydroxyl groups) [9], it
was likely that the majority of the nickel ions were closely associated
with the CMC molecules. Therefore nucleation and initial crystal growth
of Ni(0) may preferentially occur on CMC. In addition, CMC presented in-
teresting dynamic supramolecular associations facilitated by inter- and
intra-molecular hydrogen bonding, which could act as templates for
nanoparticle growth [8]. They aggregated to pseudo-spherical Ni-CMC
nanoparticles in a further step.
Table 1
XRD signals and the diameter of diffraction of the Ni crystallites calculated by Debye–
Scherrer's equation.
Sample Ni (w/w%)a (hkl) 2θ (°)
FWHM (°) Ni particle diameter (nm)b
Ni-CMC 95%
111
200
44.520 0.106
88.3
76.5
83.6
77.2
80.4
51.872 0.126
76.400 0.132
92.953 0.163
98.455 0.165
2
3
2
20
11
22
a
Measured by ICP-AES.
b
From Bragg reflections of cubic phase of Ni by Debye–Scherrer's equation:
standard profile
λ=incident ray wavelength: 1.54050 Å; δ=FWHM in radians; θ=diffraction angle).
D=0.9×λ/(δ×cosθ) corrected considering the width of LaB
(
6
In order to characterize the active phase of catalyst, the resulting
Ni-CMC particles were recovered by filtration of the active aqueous
suspension. The residue was washed several times with water, etha-
nol and acetone. Finally, the product was dried in air at 100 °C for
The nickel crystallite size was calculated from the full-width at half max-
imum (FWHM) of the Bragg reflections using the Debye–Scherrer's
equation corrected for the instrumental line width broadening
(Table 1). The calculated particle diameter resulted between 75
and 90 nm. After four cycles of nitrobenzene hydrogenation, XRD
pattern of the isolated catalyst (Fig. 1B), shows two broad peaks at
2θ=43.5° and 62.8°, indexing (200) and (220) crystalline planes re-
spectively, were assigned to NiO oxide (JCPDS, file no. 78-0643) and
no diffraction peaks of metallic Ni were observed, indicating that
metallic Ni has been converted to NiO.
2
4 h.
The XRD pattern of the Ni-CMC is shown in Fig. 1A, the Miller in-
dices are specified above the corresponding peaks.
The XRD reflections in the 40–120° 2θ interval have been assigned to
the (111), (200), (220), (311) and (222) crystalline planes of the typical
cubic phase of metallic nickel (PDF#87-712). No impurity diffraction
peak was detected, indicating that phase pure metal nickel with good
crystallinity was prepared under the present experimental conditions.
As expected, Ni is present at levels >95% w/w in Ni-CMC
(Table 1). However, as shown in Fig. 2, upon reaction extensive loss
of Ni occurred with just around 42% Ni remaining in the polymer
matrix.
However, Ni is still present in large amounts as shown by EDX anal-
ysis (Fig. 3) and still capable of reacting. In fact, EDX on various regions
of Ni-CMC before hydrogenation confirmed the presence of Ni, with en-
ergy bands centered on 7.5 and 8.3 keV (K lines) and 0.8 keV (L lines)
(Fig. 3E). The analysis indicates a predominance of Ni over carbon and
oxygen species, which come mainly from the polymer (Fig. 3, B–D).
High levels of Ni were observed even after 4 cycles of hydrogenation, al-
though ICP-AES has already shown a >50% w/w loss. The reduced pres-
ence of Ni is evident looking at the lower intensity of the signals in the
EDX spectrum (Fig. 3E).
The loss in Ni could be explained by looking at the morphology of
the samples before and after hydrogenation. As shown in Fig. 4A, the
lower magnification SEM image indicates that the obtained Ni-CMC is
characterized by rosebud-like polymeric particles of about 4–5 μm. A
detailed side view on the individual Ni-CMC particle can be observed
from the higher magnification image, which clearly shows that the
Ni-CMC flowers with spherical symmetry are composed of many
interconnected wide nanosheets. These nanosized structures are well
Fig. 2. ICP-AES analysis of Ni-CMC before and after four cycles of hydrogenation
Fig. 1. XRD patterns of prepared Ni-CMC (A) and after four hydrogenation cycles (B).
reaction.

M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
95
Fig. 3. EDX analysis of Ni-CMC before (left column) and after (right column) four cycles of the hydrogenation reaction. Panels B–D depict in the order C, O and Ni. Panel E displays
the corresponding EDX spectra.
evident on the surface of the polymer particle and were estimated hav-
ing a mean Feret's diameter of 77.5± 13.5 nm. These values are quite in
agreement with those calculated by the Debye–Scherrer's equation and
the resulting distribution is shown in Fig. 5.
The same sample observed after four hydrogenation cycles showed
a drastic change in morphology with complete loss in structure of the
polymer support (Fig. 4B). Also we observed pseudo-spherical particles
on the surface, which can be assigned to Ni. However, as evident from

96
M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
Fig. 4. SEM images recorded at increasing magnification of Ni-CMC before (A) and after (B) four cycles of the hydrogenation reaction.
Fig. 1B, Ni seems to have lost crystallinity with complete disappearance
of the characteristic XRD signals in Fig. 1A.
Such observations suggest a deep change of the system upon reac-
tion, which may be the result of the drastic conditions needed to carry
on the reaction.
The TEM image in Fig. 6 shows that Ni-CMC nanoparticles exhibited
a spherical morphology. It was observed that the Ni nanoparticles were
encapsulated into CMC. The black spheres represent Ni-CMC clusters
and the black spots representing Ni nanoparticles dispersed on the
support.
Before hydrogenation (Fig. 6A), a high concentration of Ni parti-
cles relatively dispersed on the support was observed. However,
TEM morphology of the catalyst after four cycles of hydrogenation
These results indicate that fragmentation occurred to the Ni crys-
tallites observed initially during the reaction and the extensive loss
measured may be due to the leakage of Ni from the matrix that con-
temporarily underwent possible chemical degradation. This may
also partly explain the loss of crystallinity of the system. The hypoth-
esis about CMC degradation lays on a possible oxidation linked to the
high content of oxygen of the CMC polymer. In fact, in Fig. 3E, beyond
Ni reduction, the EDX spectra show an increase in the intensity of the
oxygen signal at 0.5 keV, which may be correlated with the presence
of a large amount of oxidized species confirmed by XRD analysis
(Fig. 1B), which shows an oxidized phase of Ni (NiO) with no diffrac-
tion peaks of metallic Ni.
(
Fig. 6B) showed agglomerated particles with the presence of smaller
3.1. Evaluation of the catalytic activity of Ni-CMC
single particles. Even by TEM, the physical change of the matrix is
well visible due to probable decomposition during the reaction.
A deeper analysis of the TEM images allowed to estimate the mean
Feret's diameter calculated over a population of 50 random counts
Aromatic amines are important starting materials and intermediates
in the synthesis of a variety of pharmaceutical products, agricultural
chemicals, dyestuff and polymers [12]. Their preparation using catalytic
reduction of aromatic nitro compounds has been object of a number of
studies [13–15]. Among them, metal/hydride complexes [16], homoge-
neous and heterogeneous catalytic transfer hydrogenations [17,18]
have been reported. Good results were observed with nickel catalysts
[18–22] in direct hydrogenation reactions, described as an alternative
green process for the preparation of p-aminophenol and its derivatives
[23].
(
Fig. 7).
Ni-CMC nanoparticle distribution is shown in Fig. 7A. The average
diameter was 89.5± 36.3 nm very well correlated to that obtained by
using the highest XDR signal in Fig. 1A of 88.3 nm. The population
clearly resulted not completely homogeneous with the presence of
large clusters above 100 nm. The analysis performed on the reacted
sample instead highlighted the presence of smaller particles and an
average diameter of 29.8± 20.9 nm (Fig. 6B).
To evaluate the catalytic performance of the Col-Ni-CMC Nps, we
have studied the hydrogenation of a number of functionalized nitro-
benzenes to the corresponding anilines.
The reaction conditions (pressure and solvent) were preliminarily
optimized using nitrobenzene 1a as model substrate and the results
are summarized in Table 2. In fact, under atmospheric pressure, we
have observed that the hydrogenation of 1a takes 48 h to carry out
with moderate conversion (63% of 2a) (Table 2, entry 1). A combina-
tion of water and alcohol as solvent has a good effect on the activity of
the catalyst. The best results were obtained using a mixture of water/
isopropanol or water/methanol (Table 2, entries 4 and 5 respective-
ly). Higher hydrogen pressure showed a favorable effect and reduces
the reaction time considerably (Table 2, entries 6–8). In all the cases,
the hydrogenation of nitrobenzene afforded aniline 2a as the only
product (Table 2).
With the optimized conditions on hand, Ni-CMC Nps catalyzed
hydrogenation of functionalized nitrobenzenes 1b–i were investi-
gated obtaining the corresponding aromatic amines 2b–i in good
to excellent yields (79–98%). As shown in Table 3, all the reactions
were completed within 8–36 h at room temperature under 40 bars
Fig. 5. The estimated Feret's distribution of Ni-CMC particle diameters obtained by SEM
image analysis of 60 random samples.

M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
97
Fig. 6. TEM images of Ni-CMC before (A) and after (B) 4 cycles of the hydrogenation reaction. Bars are all 100 nm wide except in the first panel that is 500 nm.
hydrogen pressure. This investigation showed that the catalytic
activity is strongly dependent on the nature of the functional
fourth runs albeit the yields were still reasonably good. At any rate, no
byproducts arose in these experiments. In order to understand the
cause of the decline in activity, we subjected the catalyst (isolated by
filtration) after fourth runs to ICP-AES analysis (Fig. 4). The analysis con-
firms that the catalyst was subjected to leaching during the hydrogena-
tion. Only 42% of Ni was retained in the catalyst. In addition, the XRD
spectrum shows two broad peaks corresponding to the nickel oxide
(NiO) resulting from oxidation of metallic nickel in the reaction medi-
um. However, the satisfactory yields of hydrogenation after the third
and fourth runs could be explained by the involvement of NiO as cata-
lyst in hydrogenation. In fact Farhadi et al. [24] have prepared and
used NiO nanoparticles as efficient and selective heterogeneous catalyst
for the reduction of nitroarenes into their corresponding amines.
We continued our investigation in the aim to uncover another
significant catalytic activity of Ni-CMC Nps for ecofriendly hydrogenation
of ketones in aqueous media. Catalytic hydrogenation of aromatic
ketones to afford benzyl alcohols represents a useful strategy in the prep-
aration of fine chemicals and drugs [25]. Selective hydrogenation of ke-
tones can be achieved with homogeneous catalyst. For example a
cetophenone can be selectively converted into 1-phenylethanol using a
number of procedures recently summarized in some publications [26,27].
group. Particularly, a kinetic decrease with CO
2
Me (3-nitrobenzoic
acid methyl ester), OH (3-nitrophenol and 2-nitrophenol), NH
2
(
4-nitrophenylamine and 2-nitrophenylamine) (Table 3, entries
1
1, 13, 14 and 15 respectively) was observed. The best result was
obtained with 1-methyl-4-nitrobenzene 1b affording 2b in 8 h and
8% of yield. The proposed catalyst proved to be efficient in terms
9
of chemoselectivity through the reduction of nitro group even in
the presence of other functionality.
All the yields are referred to the amount of isolated products after
purification and the structures were confirmed by comparison of the
spectroscopic data with those reported in literature [18–22].
We also studied the possibility of reutilization of the Col-Ni-CMC Nps
using nitrobenzene as a substrate. For each cycle, the Col-Ni-CMC Nps
were decanted and the supernatant was removed, followed by the addi-
tion of more substrate. In the same conditions (S/C=100, solvent:
H
2
O/MeOH (8/2), PH
iline obtained from hydrogenation of nitrobenzene after 12 h, were
9%, 83%, 76% and 66%, for first run, second run, third run and fourth
run respectively. A decrease in activity was observed for the third and
2
: 40 bars, room temperature), the yields of an-
9
Fig. 7. Distribution profiles of Ni particles in the (A) initial Ni-CMC system and (B) after four cycles of hydrogenation reaction. Size was estimated from TEM analysis upon a pop-
ulation of 50 randomly taken counts.

98
M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
Table 2
Table 3
Hydrogenation of nitrobenzene 1a catalyzed by Col-Ni-CMC Nps: influence of the sol-
vent and hydrogen pressure.
Scope of reaction: hydrogenation of functionalized nitrobenzenes catalyzed by Col-Ni-CMC
Nps.
Entry
1
Product
Time (h)
Yield (%)a
9
8
98
Conversiona
%
10
12
32
12
36
24
36
24
96
88
82
79
93
94
95
Entry
Solvent
H
2
pressure (bar)
Time (h)
1
2
3
4
5
6
7
8
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
O
1
1
1
1
1
10
20
40
48
48
48
48
48
32
18
12
63
10
66
78
80
91
99
100
O/CHCl
O/THF
3
O/iPrOH
O/MeOH
O/MeOH
O/MeOH
O/MeOH
11
Conditions: S/C=100, 0.5 g/L CMC, solvent (8/2): 10 mL, room temperature.
12
a
The conversions were determined by GC.
A number of reducing agents are nowadays available: nickel Raney
28], Ni-MCM-41 [29], Cu/Ru complexes [30], and HCOONa/ΔPressure
31].
The use of toxic solvents, long reaction times associated to a large
production of wastes and low yields represents the major drawback
of all these methodologies.
In contrast heterogeneous catalysts can provide useful strategies
and are usually characterized by high catalyst turnover and recycla-
bility and, consequently, ecofriendly process.
A number of studies have been reported for the hydrogenation of
acetophenone using heterogeneous Pt, Pd, Rh, and Ru based cata-
lysts. These reactions can be carried out under liquid- or gas-phase
conditions [32–35] and present easy work up, short reaction times
and good yields.
13
[
[
14
1
1
5
6
A number of aryl and alkyl ketones were hydrogenated using
Ni-CMC as catalyst. All the reactions were done in water, at room
temperature and under hydrogen pressure (40 bars). The results,
summarized in Table 4, underline the high performance of the catalyst.
All the yields are referred to the amount of the isolated products (4a–j)
after purification. Starting from acetophenone and similar derivatives
Conditions: S/C=100, 0.5 g/L CMC, solvent: H O/MeOH (8/2): 10 mL, PH : 40 bars,
room temperature. All the spectroscopic data of the reaction products were compared
2
2
with those reported in the literature and commercially available [18–22].
a
Isolated yield.
(3a, 3c–e), the reaction resulted to be quantitative in 24 h and there is
no appreciable influence on the steric hindrance on the carbon atom
adjacent to the carbonyl group. Longer reaction time is required in the
presence of slightly electron-donating substituents (3b, 36 h) as well
as a methoxy group in ortho position (3f, 72 h) or a chlorine in para
position (3g, 72 h).
Good yields and shorter reaction time were observed in the case
of the aliphatic ketone (3i). With ketolactone derivatives (3j), the
reduction occurred chemio-selectively on the keto group. Interest-
ingly also benzophenone (3h) can be efficiently reduced to the cor-
responding alcohol and no side product derived by over-reduction
was observed.
The catalyst was recovered for successive hydrogenations of
acetophenone showing an appreciable catalytic activity (Table 5).
The yields of corresponding alcohol after 24 h were still reasonably
good after fourth run despite a leaching of the catalyst. These results
showed that the catalyst can be reused for four cycles.
diameter of 89.5± 36.3 nm. As a stabilizing agent of nanoparticles,
CMC played a very important role on the preparation of Ni-CMC
composite.
Col-Ni-CMC nanoparticles proved to be efficient catalyst for the
hydrogenation of functionalized nitrobenzenes and ketones to anilines
and alcohols respectively. The reaction was conducted in aqueous
medium at room temperature under pressure of H (1 to 40 bars).
2
The Ni Nps capped by sodium carboxy-methyl cellulose are stable
during the hydrogenation process. The catalytic activity increased
2
with increasing pressure of H . Moreover, the Col-Ni-CMC Nps could
be re-used at least four times, maintaining relatively good activity. In
the current state of this study, however, we note problem of loss of ac-
tivity after several cycles caused by leaching of the catalyst.
4
. Conclusion
Appendix A. Supplementary data
In conclusion, nickel nanoparticles stabilized with sodium
carboxy-methyl cellulose (Ni-CMC) were prepared with average
Supplementary data to this article can be found online at http://
dx.doi.org/10.1016/j.catcom.2012.11.025.

M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
Table 4 (continued)
99
Table 4
Hydrogenation of acetophenone derivatives and aliphatic ketones catalyzed by
Col-Ni-CMC Nps.
Yielda
%
Entry
Substrate
Product
Time (h)
12
26
99
2 2
Conditions: S/C=100, 0.5 g/L CMC, solvent: H O, 10 mL, PH : 40 bars, room tempera-
ture. All the spectroscopic data of the reaction products were compared with those
reported in the literature and commercially available [27].
Entry
Substrate
Product
Time (h)
24
Yielda
98
%
a
Isolated yield.
17
Table 5
Hydrogenation of 3a catalyzed by Col-Ni-CMC Nps: catalyst recyclability.
Entry
Run
Yield %
2
28
7
1
2
3
4
98
98
92
81
1
1
8
9
36
24
94
96
2
3
9
0
Conditions: S/C=100, 0.5 g/L CMC, solvent:
temperature, time: 24 h.
H
2
O, 10 mL, PH
2
:
40 bars, room
References
[
1] A. Saxena, A. Kumar, S. Mozumdar, Journal of Molecular Catalysis A: Chemical 269
2007) 35–40.
(
20
24
99
[
2] a) M. Kidwai, N.K. Mishra, V. Bansal, A. Kumar, S. Mozumdar, Catalysis Commu-
nications 9 (2008) 612–617;
b) F. Alonso, P. Riente, J.A. Sirvent, M. Yus, Applied Catalysis A: General 378
(2010) 42–45;
c) F. Alonso, P. Riente, M. Yus, Tetrahedron 64 (2008) 1847–1852;
d) G. Bai, F. Li, X. Fan, Y. Wang, M. Qiu, Z. Ma, L. Niu, Catalysis Communications 17
(
2012) 126–130.
3] M. Kidwai, V. Bansal, A. Saxena, R. Shankar, S. Mozumdar, Tetrahedron Letters 47
2006) 4161–4165.
4] a) K. Dhakshinamoorthy, K. Pitchumani, Tetrahedron Letters 49 (2008)
818–1823;
2
2
1
2
24
72
99
92
[
[
(
1
b) F. Alonso, P. Riente, M. Yus, Tetrahedron 65 (2009) 10637–10643;
c) H. Zhao, H. Song, L. Chou, Inorganic Chemistry Communications 15 (2012)
2
61–265;
d) Y. Tang, D. Yang, F. Qin, J. Hu, C. Wang, H. Xu, Journal of Solid State Chemistry
8 (2009) 2279–2284.
5] a) A. Wang, H. Yin, H. Lu, J. Xue, M. Ren, T. Jiang, Catalysis Communications 10
2009) 2060–2064;
1
[
(
b) N. Mahata, A.F. Cunha, J.J.M. O'rfao, J.L. Figueiredo, Applied Catalysis A: Gener-
al 351 (2008) 204–209.
[
[
6] a) M.C. Daniel, D. Astruc, Chemical Reviews 104 (2004) 293–346;
b) A. Wolf, F. Schuth, Applied Catalysis A: General 226 (2002) 1–13.
7] a) Y. Chauvin, C. Commereuc, F. Dawans, Progress in Polymer Science (1977)
2
2
3
4
72
48
98
85
9
5–226;
b) F. Cicardelli, G. Sbraca, C. Carlini, Journal of Molecular Catalysis 14 (1982)
–10;
c) T. Liming, H. Meiyu, J. Yingyan, Chinese Journal of Polymer Science 14 (1996)
99–204.
8] F.R. Hartley, in: Supported Metal Complexes, Reidel, Boston, 1985, pp. 170–174.
1
1
[
[9] A. Taubert, G. Wegner, Journal of Materials Chemistry 12 (2002) 805–807.
10] M. Anouar Harrad, P. Valerga, M.C. Puerta, I. Houssini, M. Ait Ali, L. El Firdoussi,
A. Karim, Molecules 16 (2011) 367–372.
[
[
[
[
11] W.H. Walton, Nature 162 (1948) 329–330.
12] K. Young-Soo, Q.X. Li, Chemosphere 54 (2004) 255–263.
13] R.C. Larock, in: Comprehensive Organic Transformations—A Guide to Functional
Groups Preparations, VCH publishers. Inc., New York, 1989, pp. 1–412.
14] Y. Ping, Z. Wei, D. Yukou, W. Xiaomei, Journal of Molecular Catalysis A: 260
[
(2006) 4–10.
[
[
15] S. Amit, R. Brindaban, The Journal of Organic Chemistry 73 (2008) 6867–6870.
16] J.F. Quinn, C.E. Bryant, K.C. Golden, B.T. Gregg, Tetrahedron Letters 51 (2010)
1
2
94
25
771–786.
[
[
17] B. Baruwati, V. Polshettiwar, S.R. Varm, Tetrahedron Letters 50 (2009) 1215–1218.
18] H. Wena, K. Yao, Y. Zhang, Z. Zhou, A. Kirschning, Catalysis Communications 10
(2009) 1207–1212.
[
19] M. Watanabe, H. Yamashita, X. Chen, J. Yamanaka, M. Kotobuki, H. Suzuki, H.
Uchida, Applied Catalysis B: Environmental 71 (2007) 237–245.
(continued on next page)

100
M.A. Harrad et al. / Catalysis Communications 32 (2013) 92–100
[
20] J.K. Roozbeh, A.N. Amir, B. Farzaneh, Catalysis Communications 12 (2011)
[29] S.K. Mohapatra, S.U. Sonavane, R.V. Jayaram, P. Selvam, Organic Letters 4 (2002)
4297–4300.
955–960.
[
[
21] Y. Du, H. Chen, R. Chen, N. Xu, Applied Catalysis A: General 277 (2004) 259–264.
22] N. Mahata, A.F. Cunha, J.L. Figueiredo, Applied Catalysis A: General 351 (2008)
[30] T. Ohkuma, H. Ooka, S. Hashiguchi, T. Ikaria, R. Noyori, Journal of the American
Chemical Society 117 (1995) 2675–2676.
2
04–209.
[31] L. Bangell, C.R. Strauss, Chemical Communications 9 (1999) 287–288.
[32] K. Yoshida, C.G. Arellano, R. Luque, P.L. Gai, Applied Catalysis A: General 379
(2010) 38–44.
[
[
[
23] H. Lu, H. Yin, Y. Liu, T. Jiang, L. Yu, Catalysis Communications 10 (2008) 313–316.
24] S. Farhadi, M. Kazem, F. Siadatnasa, Polyhedron 30 (2011) 606–613.
25] C.J.A. Daley, S.H. Bergens, Journal of the American Chemical Society 124 (2002)
[33] N.M. Bertero, C.R. Apesteguia, A. Marchi, Journal of Applied Catalysis A: General
349 (2008) 100–109.
3680–3691.
[
[
[
26] H.-U. Blaser, C. Malan, B. Pugin, F. Spindler, H. Steiner, M. Studer, Advanced Syn-
thesis and Catalysis 345 (2003) 103–151.
27] M. Ait Ali, S. Allaoud, A. Karim, C. Meliet, A. Mortreux, Tetrahedron: Asymmetry
[34] C.S. Chen, H.W. Chen, W.H. Cheng, Applied Catalysis A: General 248 (2003)
117–128.
[35] G.F. Santori, A.G. Moglioni, V. Vetere, I.G.Y. Moltrasio, M.L. Casella, O.A. Ferretti,
Applied Catalysis A: General 269 (2004) 215–223.
1
1 (2000) 1367–1374.
28] H. Adkins, H.R. Billika, Journal of the American Chemical Society 709 (1948)
95–698.
6