Highly efficient transfer hydrogenation of carbonyl compounds over supported nickel and palladium nanoparticles

Cite this paper: Vietnam J. Chem., 2021, 59(2), 192-197 Article 
DOI: 10.1002/vjch.202000142 
192 Wiley Online Library © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH 
Highly efficient transfer hydrogenation of carbonyl compounds over 
supported nickel and palladium nanoparticles 
Co Thanh Thien
*
, Nguyen Nhut Minh, Vo Ly Dinh Khang 
University of Science, Vietnam National University - Ho Chi Minh City, 
227 Nguyen Van Cu, District 5, Ho Chi Minh City 70000, Viet Nam 
Submitted August 24, 2020; Accepted November 14, 2020 
Abstract 
In this work, metal nanoparticles were successfully synthesized through the reduction of metal salts using reducing 
agents such as: ethylene glycol (EG) and sodium borohydride (NaBH4). These metal nanoparticles were impregnated 
into the supports M-X (M = Ni, Pd; X = Bent, C, Zeolite, and Al2O3) in high yield. The physio-chemical properties of 
these catalysts were characterized by various techniques such as UV-Vis spectroscopy, powder X-ray diffraction 
(PXRD), Transmission electron microscopy (TEM) and the specific surface area of M-X was evaluated by N2 
adsorption isotherm analysis at 77 K. All results corroborated the loading process. Literally, TEM images indicated that 
the palladium and nickel nanoparticles size are 6 and 13 nm, respectively. The efficiency of these catalysts was 
performed on the transfer hydrogenation of various carbonyl substrates in the presence of potassium hydroxide at 
atmosphere pressure. The results showed that both nickel and palladium supported X catalysts exhibited high activities 
over 99 % within 60 min in the presence of potassium hydroxide. 
Keywords. Nickel, palladium nanoparticles, nanocatalysts, hydrogenation, supported catalysts. 
1. INTRODUCTION 
Although hydrogenation has been mentioned since 
the late 19
th
 century,
[1,2]
 yet it is still attracting the 
attention of many scientists by its convenient and 
powerful method to access a variety of industrial 
applications from fine chemicals to pharmaceuticals 
synthesis.
[3,4]
 Usually, transfer hydrogenation was 
performed at high temperatures, and long reaction 
times, yet the low activity was observed. Recently, a 
numbers of reports have shown the hydrogenation 
with high efficiency, stability, and easy recovery 
when palladium catalyst was used.
[5–8]
 However, 
palladium is relatively high-cost metal compared 
with other noble metals. The industrial application 
of palladium catalysts will be limited due to their 
cost. Thus, palladium was significantly replaced by 
nickel which is now familiar catalyst in the 
hydrogenation of carbonyl compounds. For 
examples, Sebakhy et al. was dispersed nickel-
doped aegirine nanocatalysts for the selective 
hydrogenation of olefinic molecules at 140200 
o
C
[9]
. Whereas Francisco A. and coworkers carried 
out the transfer hydrogenation of acetophenone with 
excellent activity under nickel nanoparticles at 76 
o
C 
within 24h except the low selectivity was 
obtained.
[10]
 Hence, nickel-based catalysts with 
excellent activity and selectivity are still necessary. 
On the other hand, immobilization of the 
metallic nanoparticles on solid materials has 
received a great interest because of their use in 
industrial application. Although nanocatalysts serve 
as an excellent heterogeneous catalyst, they usually 
need an additional support to obtain thermal stability 
as well as improve the catalytic activity. Thus, 
varieties of materials such as zeolites, aluminum 
oxides, aluminosilicates, activated carbon, zinc 
oxides, etc. have been used as supports for 
nanocatalysts.
[11-13]
 Among these materials, 
bentonites, zeolites, activated carbon, and aluminum 
oxide are widely used as catalyst and support for 
quite a lot of reactions as well. 
This study focused on the preparation of nickel 
and palladium nanoparticles supported on 
bentonites, zeolites, activated carbon, and aluminum 
oxide. The reason for including the synthesis of 
palladium catalyst in this report is that we would like 
to compare the activity to the nickel catalysts in the 
same manner. Catalytic activity was evaluated via 
the transfer hydrogenation of benzaldehyde and 
ketone. 
2. MATERIALS AND METHODS 
2.1. Materials 
Vietnam Journal of Chemistry Co Thanh Thien et al. 
 © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 193 
Unless otherwise noted, all experiments were carried 
out in air. Reagent grade nickel chloride hexahydrate 
(NiCl2.6H2O, 98 %), palladium (II) chloride (PdCl2, 
99 %), aluminum oxide (Al2O3, 99 %), ethylene 
glycol (EG, 99.5 %) and sodium borohydride 
(NaBH4, 98 %) were purchased from Merck. Binh 
Thuan bentonite (Bent) and activated carbon were 
purchased from the local suppliers. Isopropanol 
(IPA, 99 %) was purchased from CHEMSOL and 
used without further purification. 
2.2. Characterization 
The morphology of catalysts was examined by a 
scanning electron microscope (SEM, JEOL series 
JSM-7401F). Transmission electron microscopy 
(TEM) images were collected using FEI Tecnai G2 
F20. The X-ray diffraction (XRD) data of all 
samples were collected in a Bruker D8 powder X-
ray diffractometer with CuKα radiation running at 35 
kV/30 mA in the 2θ range 5o75o with a step size of 
0.2
o
/min. Nitrogen adsorption–desorption isotherms 
were collected at 77 K using Brunauer–Emmett–
Teller calculation (BET, AUTOSORB-1C 
Quantachrome). GC/MS analysis was measured by 
an Agilent 7890A (HP5 column 30 m 0.25 mm, 
FID detector). The element analysis was conducted 
by atomic emission spectroscopy (AES) on an ICP-
MS 7500 series (Agilent). All the catalytic 
experiments were carried out in a multireactor 
(Carousel 12+). 
2.3. Preparation 
The nickel and palladium nanoparticles were 
prepared in the same process as mentioned in the 
previous repor ... Both paladium and nickel 
nanoparticles were successfull anchored into 
supports X in high loading yield. 
As shown in figure 1 (a-d) the typical powder 
XRD patterns of supported nickel nanoparticles, in 
which the appearance of the characteristic peaks of 
metallic nickel at 2θ were at 44.55o and 51.78o 
which are previously reported by Li and 
coworkers.
[19]
 Likewise, figure 1 (e-h) described the 
XRD patterns of supported palladium nanoparticles 
which is corresponding to the 2q values of 40.01 and 
46.70
o
.
[20]
 However, the diffraction signals are rather 
weak, it could be explained that the concentration of 
metal particles in the catalytic samples was low. 
Besides, the XRD patterns of the supports as 
shown in the figure 1, the peaks of Zeolite and Al2O3 
located at the position of 2θ = 21.90°; 24.21°; 
27.43°; 30.25°; 33.21°; 34.53°; 36.17
o
; 45.50°; and 
Vietnam Journal of Chemistry Highly efficient transfer hydrogenation of... 
 © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 194 
25.90°; 35.43°; 38.04°; 43.61°; 52.92°; 57.77
o
; 
66.80
o
; 68.42
o
, respectively. Meanwhile, the 
activated carbon and Bent are amorphous lattice 
structure leading to the XRD patterns as noise at the 
baseline. 
Figure 2 illustrated the TEM images of metal 
nanoparticles as well as the average diameter of the 
catalysts. Namely, figure 2a showed TEM images 
scaled at 50 nm of the nickel nanoparticles, in which 
the average particles diameter are about 13 nm. 
Meanwhile, figure 2b described that the average 
particles size of palladium nanoparticles was 6 nm 
and well dispersed. On the other hand, as shown in 
figure 3, SEM images of both supported nickel and 
palladium nanoparticles, therein the characteristic 
surface of M-C and M-Zeolite were found to be 
smooth and rough (figure 3c, d, g, h), whereas, the 
surface of M-Al2O3 and M-Bent displays nearly 
smooth surface characteristic (figure 3a, b, e, f). 
Literally, in the case of Ni-C catalyst (figure 3c), the 
surface was covered by big spherical cubic blocks 
which could make the specific surface area of the 
catalyst better. 
5 10 15 20
F
re
q
u
e
n
c
y
Diameter (nm) 
 . (a) 
2 4 6 8 10
F
re
q
u
e
n
c
y
Diameter (nm) 
 (b) 
Figure 2: TEM images taken at 50 nm of (a) Ni nanoparticles; (b) Pd nanoparticles 
In contrast, the surface of Ni-Al2O3 (Figure 3a) 
contained many of slit-shapes between the pores. 
Likely, the small spherical shapes on the surface of 
Pd-Zeolite (figure 3h) were found out. It is revealed 
that the metal nanoparticles are well dispersed on the 
surface of the supports which have a nearly spherical 
morphology. More importantly, no metal 
aggregation formation was observed on the SEM 
images of catalysts. 
In addition, as shown in table 1, the 
microporosity of X supported metal nanoparticles 
was collected from BET measurement, in which the 
pore size distributions as well as the specific surface 
area of the prepared catalysts are corresponding to 
the SEM images. Furthermore, in all cases, the 
supported catalysts possessed the specific surface 
area lower than the parent supports. That could be 
explained that almost the metal nanoparticles were 
anchored into the pores of supports leading to the 
decrement of specific surface area of the catalysts. 
Vietnam Journal of Chemistry Co Thanh Thien et al. 
 © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 195 
Indeed, in the Table 2, the concentration of the metal 
particles distributed on the supports is quite low 
based on atomic emission spectroscopy (AES) 
analysis. Especially, in the case of palladium 
catalysts, only 0.91 % was obtained with bentonites. 
The catalytic activity of transfer hydrogenation 
of carbonyl compounds in the liquid phase was 
evaluated by addition of 2.0 mol% of M-X catalysts 
to the carbonyl substrates and hydrogen gas in the 
alkaline solution. 
Table 1: The characteristic surface of catalysts 
Catalysts SBET (m
2
.g
-1
) 
Bent C Zeolite Al2O3 
Blank 54.082 318.364 64.780 16.990 
Ni 23.103 128.007 56.408 8.902 
Pd 15.406 92.556 12.159 2.771 
(a) (b) (c) 
(d) (e) (f) 
(g) (h) 
Figure 3: SEM micrographs (a) Ni-Al2O3; (b) Ni-Bent; (c) Ni-C; (d) Ni-Zeolite; (e) Pd-Al2O3; (f) Pd-Bent; 
(g) Pd-C; (h) Pd-Zeolite 
Table 2: Concentration of metal nanoparticles in 
supports based on EDX and AES measurements 
Catalysts 
(%) 
Parent supports (X) 
Bent C Zeolite Al2O3 
Ni 6.96 7.78 6.55 4.68 
Pd 0.91 2.88 2.10 1.30 
The previous report indicated that the 
hydrogenation got the best activity in isopropanol at 
60 °C within 1 hour.
[21]
 Hence in this study, the 
transfer hydrogenation of carbonyl substrates was 
performed under similar conditions. It is noted that 
all the catalysts gave 100 % selectivity of benzyl 
alcohol, therefore it will not mention the selectivity 
in this report. Indeed, most of catalysts gave a high 
hydrogenate activity within 1h. Namely, M-Bent 
gave 93.0 and 95.0 % conversion in cases of Ni and 
Pd catalysts, respectively. 
Meanwhile, over 99 % conversion were obtained 
in both cases of M-C and M-Zeolite regardless of M 
is Ni or Pd. Even though, the parent supports gave 
Vietnam Journal of Chemistry Highly efficient transfer hydrogenation of... 
 © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 196 
moderate activity of up to 52 % in case of Zeolite. 
These could be explained in terms of the 
morphological surface of the catalysts as well as the 
concentration of the metal loaded on the supports as 
shown in Table 2. It is clear that the catalytic activity 
of hydrogenation exhibited an excellent conversion 
of carbonyl substrates in base solution. 
According to figure 4, it indicated that both M-C 
and M-Zeolite catalysts gave the best activity in the 
transfer hydrogenation of benzaldehyde. Thus, the 
influence of functional group as well as their 
position on the benzaldehyde was performed based 
on M-Zeolite catalysts. Besides, table 3 illustrated 
that regardless of the position of functional group, 
metha- or para-substitute, the transfer hydrogenation 
exhibited the excellent efficiency. Except the 
secondary carbonyl substrate, as shown in entry 5, 
even the reaction was carried out at 90 
o
C within 3 h, 
the activity was till low, namely, only 72.7 % 
conversion was obtained in the case of Pd-Zeolite as 
catalyst. In reality, C. Neelakandeswari and 
coworkers carried out the hydrogenation of 
benzophenone at 90 
o
C within 3 hrs, 71.4 % 
conversion was observed over nickel nanoparticles 
supported on aluminosilicate.
[22]
 However, in the 
previous study published elsewhere,
[21]
 99 % 
conversion of p-chlorobenzaldehyde was obtained in 
the presence of 15 %Pd-C as catalyst (entry 2). It 
could be explained in terms of the concentration of 
palladium in the catalytic samples as well as the 
supported carbon which is carbon Vulcan with 
nanoparticles size (50 nm) leading to the better 
conversion compared to our Pd-Zeolite catalyst 
(94.7 %). In general, it could be confirmed that the 
activity of nickel catalysts increased significant 
based on the concentration of the metal on the 
supports. Simultaneously, it could replace the 
palladium catalyst in the furture of catalytic transfer 
hydrogenation. 
52.1
44.5
52.8 51.9
93.0
99.6 99.4
95.495.0
99.9 99.6
97.3
Bent C Zeolit Al2O3 --
40
60
80
100
C
o
n
v
e
rs
io
n
 (
%
)
 Blank
 Ni
 Pd
Figure 4: The activity of transfer hydrogenation of 
benzaldehyde over M-X catalysts 
Table 3: Conversion of transfer hydrogenation of the carbonyl substrates over catalysts 
Entry 
Substrates 
Products
*
Conversion (%) 
Ni-
Zeolite 
Pd-
Zeolite 
1 CHO
CH2OH
99.4 99.6 
2 CHOCl
CH2OHCl
90.1 94.7 
3 
CHO
O2N
CH2OH
O2N
86.9 92.1 
4 CHOH3CO
CH2OHH3CO
89.5 90.8 
5
**
 H3CO
O
CH3 
H3CO
OH
CH3 
75.8 72.7 
*
The absolute selectivity of alcohol products were observed in all cases. 
**
Reaction was carried out at 90 
o
C within 3 h. 
4. CONCLUSIONS 
In summary, the catalysts M-X (M = Ni, Pd; X = 
Bent, C, Zeolite, Al2O3) were successfully 
synthesized. All the physio-chemical 
characterization of the catalysts was defined in 
detail. In which TEM image and XRD illustrated 
that metal particles size was around 6 and 13 nm in 
Vietnam Journal of Chemistry Co Thanh Thien et al. 
 © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 197 
the case of Pd and Ni, respectively. These 
incorporated as M
0
 inside X. Furthermore, the 
catalytic test indicated that almost the supported 
nanocatalysts exhibited high catalytic activities in 
the hydrogenation of benzaldehyde, especially with 
Ni-Zeolite catalyst, the productivity conversion 
acquired 99.4 % within 60 min at 60 
o
C as well as 
75.8 % conversion was observed in the transfer 
hydrogenation of ketone substrate. 
Acknowledgments. The authors would like to thank 
Vietnam National University-Ho Chi Minh City for 
financial support under grant number C2019-18-13. 
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Corresponding author: Co Thanh Thien 
Department of Physical Chemistry 
University of Science, VNU Ho Chi Minh City, 227 Nguyen Van Cu, District 5 
Ho Chi Minh City 70000, Vietnam; E-mail: ctthien@hcmus.edu.vn.