High Selectivity of Hydrogenation Reaction over Co0.15@C/PC Catalyst at Room Temperature

Article abstract of DOI:10.1021/acs.inorgchem.9b00385

In the field of catalysis, material scientists pay much attention to tuning the activity and chemoselectivity of metal nanoparticles. Herein, we design and successfully synthesize a series of Co NPs which show high performance on hydrogenation of nitroarenes with both activity and chemoselectivity. Co_0.15@C/PC preferentially activates the -C=O bond over -NO₂ in water with ammonia borane (AB); however, when the hydrogen source is changes to hydrazine hydrate (HH), the results are the opposite. The Co-based catalyst exhibits exceptionally high catalytic activity (with a TOF value of 10512 h^-1, which is approximately 100 times than the akin catalysts) and chemo-selectivity for the hydrogenation of nitro compounds under mild conditions. Additionally, the catalyst can be separated easily by a magnet and shows prominent stabilit, which means that it can be reused for at least 10 cycles.

Full text of DOI:10.1021/acs.inorgchem.9b00385

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
High Selectivity of Hydrogenation Reaction over Co0.15@C/PC
Catalyst at Room Temperature
Ruirui Yun,*,† Wanjiao Ma,† Suna Wang,‡ Weiguo Jia,† and Baishu Zheng§
†The Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science,
Anhui Normal University, Wuhu 214001, P. R. China
‡Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical
Engineering, Liaocheng University, Liaocheng 252059, P. R. China
§Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, School of Chemistry and Chemical
Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
S
* Supporting Information
ABSTRACT: In the field of catalysis, material scientists pay much attention
to tuning the activity and chemoselectivity of metal nanoparticles. Herein,
we design and successfully synthesize a series of Co NPs which show high
performance on hydrogenation of nitroarenes with both activity and
chemoselectivity. Co0.15@C/PC preferentially activates the −CO bond
over −NO2 in water with ammonia borane (AB); however, when the
hydrogen source is changes to hydrazine hydrate (HH), the results are the
opposite. The Co-based catalyst exhibits exceptionally high catalytic
activity (with a TOF value of 10512 h−1, which is approximately 100 times
than the akin catalysts) and chemo-selectivity for the hydrogenation of
nitro compounds under mild conditions. Additionally, the catalyst can be
separated easily by a magnet and shows prominent stabilit, which means
that it can be reused for at least 10 cycles.
1,22,23
kinds of hydrogenation, such as CC,19−21 −NO2
and
INTRODUCTION
■
CO24,25 bonds. But Co and Ni tend to aggregate at high
temperature, which causes the decrease of the specific surface
area and of the active site of the catalyst. Recently, many
studies have reported some ways to solve this crucial issue. Fu
and co-workers successfully loaded cobalt onto ZrLa0.2OX, for
which good dispersion and large specific surface area cause it
to have excellent catalytic performance.26 Beller’s group
reported a simple way to obtain an efficient hydrogen material
by applying a nitrogen-doped titania-supported Co cata-
lyst.27,28 These methods well solved the problem of dispersion,
and the catalytic performance was greatly improved. But the
only disadvantage is that they still use H2. Consequently, it is
very necessary to find a catalyst with simple synthesis, mild
catalytic conditions, and high hydrogenation selectivity. How-
ever, some of the shortcomings are also not negligible, such as
aggregation during the synthesis process, requirement of harsh
conditions, and poor selectivity in the process of catalytic
reaction. Therefore, it is important to design a synthetic way to
overcome the problem of aggregation while increasing specific
area and active sites to improve the reaction conditions and
enhance catalytic selectivity.29−31
Metal catalysts supported by a porous medium have been
extensively used in the chemical industry for many kinds of
reactions.1,2 In the field of heterogeneous catalysis, how to
obtain metal catalysts with high activity and chemo-selectivity
has attracted tremendous attention.3,4 In particular, selective
hydrogenation of aldehydes, ketones, and nitro compounds
plays a crucial role in the field of industry chemistry. The
selective reduction of functionalized nitroarene to amino com-
pounds is a significant process, mainly in agricultural chemistry,
pigment chemistry, and pharmacochemistry.5,6 To obtain high
performance catalysts with selectivity and high activity has
been the basic concept. Accordingly, numerous methods have
been used to construct high-efficiency catalysts, such as
heteroatom doping and multimetallic synergistic reactions.7−9
Recently, there have been many reports about selective cata-
lytic preparation of aldehydes, ketones, and nitro compounds
from alcohol and amine compounds in noble metal catalysts,
respectively, but the restricted reserves and high cost limited
their extensive application, so the sustainable use of resources,
especially with non-noble metal catalysts, have attracted the
attention of an increasing number of researchers.10,11 Non-
noble metals such as iron, cobalt, and nickel are not only
abundant on the earth, but also have superior properties in
terms of catalysis.12−14
On the basis of the above considerations, in this work, we
present a novel D-glucose-assisted pyrolysis strategy to
Co15,16 and Ni17,18 nano particles and single atom are
versatile catalysts in various catalytic reactions, including all
Received: February 12, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.9b00385
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Inorganic Chemistry
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Scheme 1. Synthesis Method of Con@C/PC Catalyst
Figure 1. (a) HTEM image and EDS-mapping of Co0.15@C/PC; (b) wide-range XPS spectrum; (c) XPS survey spectrum for Co0.15@C/PC with
two main broad peaks at 777.79 and 792.86 eV, assigned to Co 2p1/2 and Co 2p3/2, respectively.
of deionized water and stirred 30 min by ultrasonic means. The
mixture solution was heated at 100 °C for 20 min to form a purple sol
and dried under vacuum 80 °C overnight to form a purple powder.
The obtained purple powder was placed in a pipe heater and heated
to 700 °C under Ar gas atmosphere for 1 h, with that naturally cooling
to ordinary temperature.
Characterization of Samples. Powder XRD pattern was carried
out with a Bruker D8 X-ray diffractometer with monochromatized
Cu Kα radiation (λ = 1.5418 Å). Transmission electron microscope
(TEM) and high-resolution TEM observations were acquired on
JEOL-2011 with an electron acceleration energy of 200 kV. The
content of Co in the catalysts was determined by an Optima 7300 DV
inductively coupled plasma atomic emission spectrometer (ICP-AES).
X-ray photoelectron spectroscopy (XPS) was performed on a ULVAC
construct Con@C nanoparticles which were highly dispersed
on porous carbon (PC). The as-synthesized Con@C/PC (n: rep-
resents the cobalt contents) can selectively catalyze liquid-phase
hydrogenation of aldehydes, ketones, and nitro compounds in
different hydrogen sources at normal pressure and temper-
ature. We demonstrate that the hydrogen source hydrazine
hydrate is preferred for selective hydrogenation of nitro com-
pounds while ammonia borane is preferred for aldehydes.
EXPERIMENTAL SECTION
■
Sample Preparation. For the synthesis of Con@C/PC, 0.4 g of
cobalt nitrate hexahydrate and 2 g of D-glucose were added into 10 mL
B
DOI: 10.1021/acs.inorgchem.9b00385
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Inorganic Chemistry
Article
characterized by gas chromatography with n-hexadecane as an
external standard. The identity of the products was further deter-
mined by gas chromatography−mass spectrometry (GC-MS) mea-
surements with n-dodecane as standard.
RESULTS AND DISCUSSION
■
In this research, different kinds of Con@C/PC catalysts were
fabricated just as Scheme 1 illustrates. For comparison, the
effect of catalytic performance was investigated by the amount
of Co, pyrolysis temperature, and pyrolysis times. X-ray
powder diffraction (XRD) patterns confirm the Con@C/PC
phase (PDF No. 15-0806). The peaks at 44.2°, 51.5°, and
75.8° can be designated to the (100), (200), and (220) lattice
planes of Co nanoparticle (Figure S1). High-resolution trans-
mission electron microscopy (HTEM) shows that Co NPs
were encapsulated in carbon and were well dispersed on the
porous carbon (Figure 1a). All the elements including C and
Co have homogeneous distribution, as demonstrated by the
energy-dispersive X-ray spectroscopy (EDX) element mapping
images (Figure 1a). The selected area electron diffraction
(SAED) suggested that all the clear diffraction rings matched
well with Co nanoparticles (inset of Figure 1a). The Co con-
tent in Con@C/PC catalyst is in the range of 3.80−20.00%
(determined by ICP-AES, Table S1), and it was studied with
different temperatures and pyrolysis times. The states of Co atom
of Con@C/PC were characterized by X-ray photoelectron
spectroscopy (XPS) (Figure 1, parts b and c). The peaks at
777.79 and 792.86 eV can be assigned to Co0. The Raman
spectrum was used to identify the change of graphitic carbon
(Figure S2). Notably, the band with intensity at ∼1336.3 is
attributed to defective sp3 hybridized carbon (D band) and
1594.9 cm−1 can be assigned to the crystallized graphitic sp2
Figure 2. Performance of hydrogenation of nitrobenzene with a series
of Co-based catalysts (catalytic reaction with hydrazine hydrate as
hydrogen resource under room temperature).
PHI Quantera microscope. The surface area of the samples was
estimated by the method of Brunauer−Emmett−Teller (BET), and
the pore size distribution was obtained from the DFT method in the
Micrometrics ASAP2020 software package based on the N2 sorption
at 77 K.
Catalytic Hydrogenation Activity Test. All hydrogenation
reactions were placed in a 25 mL bottle and a magnetic stirrer.
In the reaction, 0.5 mmol of reactant and 10 mg of catalyst and HH or
AB were mixed in 5 mL of water and alcohol (1:4). The reaction was
carried at normal pressure and room temperature. The products were
a
Table 1. Reduction of Various Nitroarenes by Co0.15@C/PC
a
Analyzed by GC-MS spectrum with n-dodecane as standard; rt = room temperature.
C
DOI: 10.1021/acs.inorgchem.9b00385
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a
Table 2. Hydrogenation of Different Aldehydes by Co0.15@C/PC
a
Note: AB is ammonia borane. R represented as alkyl or unsaturated chain hydrocarbon. NPT is normal pressure and temperature.
carbon (G band), respectively. The ID/IG relative ratio of 0.84
also confirms defection of the carbon, which is good to favor
rapid mass transfer and can offer adequate active site exposure
for catalysis. Just as Figure S3, S4, and S5 show, the catalyst
shows rich mesoporous pores. The N2 sorption isotherm of the
Co0.15@C/PC sample showed a typical IV isotherm, which
revealed a mesoporous characteristic. The calculated total
pore volume and the BET surface area of Co0.15@C/PC were
0.19 cm3/g and 373 m2/g (Figure S6), respectively.
The catalytic performance of Con@C/PC was evaluated via
the hydrogenation of nitro compounds by hydrazine hydrate as
hydrogen resource. The products of such a reaction can be
simply analyzed by GC−MS. As shown in Figure 2, catalytic
reduction of nitrobenzene was chosen as a benchmark sub-
strate. It is notable that the nitrobenzene is quickly converted
to aniline within 20 min. The results show that the Co con-
tents strikingly boosted the efficiency during the catalytic
reaction. One of the series catalysts, Co0@C/PC, does not give
the target results. However, the catalyst Co0.03@C/PC shows
about 12% conversion which is much higher than that of Co0@
C/PC under the same reaction conditions. Furthermore, the
conversion is increased when the contents of Co are increased;
significantly, Co0.15@C/PC achieves the maximum perform-
ance. The catalyst exhibits exceptionally high catalytic activity
(10512 h−1 which is about 100 times higher than that for
similar kinds of catalysts, Table S2). The results illustrate that
well-dispersed mesoscale porosity was constructed in the syn-
size of Co NPs and the dispersity are more important for the
catalytic performance.32−35
In consideration of the fact that the catalyst Co0.15@C/PC
shows admirable catalytic performance, the hydrogenation of
different kinds of nitroarenes are implemented. We can see
from Table 1 that the catalyst enabled the hydrogenation of
multifarious substituted nitro compounds, obtaining the
corresponding anilines with perfect conversions and chemo-
selectivity. More importantly, the halogenated nitrobenzene
gave high content of the target products without dehalogena-
tion. It is worth mentioning that the catalyst expresses high
chemo-selectivity in the hydrogenation of functional nitro-
arenes, such as ester, carboxyl, carbonyl, and cyano, giving the
corresponding anilines in about 99% conversion without any
byproducts. These outstanding results highlight the chemo-
selectivity of the Co-based catalyst, showing its eminent virtue
compared to that of precious metal-based catalysts. More
interestingly, the catalyst can perform hydrogenation for a
variety of aldehydes selectively when the hydrogen resource
changes to ammonia borane at room temperature (Table 2).
The stability of catalyst is a vital benchmark to evaluate the
performance of catalyst, which is crucial for practical produc-
tions. We can see from Figure 3 that, to demonstrate the stability
and reusability of Co0.15@C/PC, cyclic experiments for the
reduction of nitrobenzene were carried out. The catalyst
Co.015@C/PC keeps its phase after being reused 11 times
(Figure S7, Supporting Information). Interestingly, the catalyst
can be simply recovered by a magnet due to its stronger mag-
netic ability.
thesis procedure of the catalysts, and the pores made Co0.15
@
C/PC fit for mass transfer of the substrate; besides this, the
D
DOI: 10.1021/acs.inorgchem.9b00385
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Inorganic Chemistry
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In conclusion, a novel and efficient strategy has been designed
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.inorgchem.9b00385.
■
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AUTHOR INFORMATION
Corresponding Author
*E-mail: ruirui58@ahnu.edu.cn (R.Y.).
ORCID
Ruirui Yun: 0000-0002-5598-5076
Weiguo Jia: 0000-0001-7976-7543
Notes
■
The authors declare no competing financial interest.
́
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́
ACKNOWLEDGMENTS
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́
Our work was funded by the National Natural Science Foun-
dation of China (No. 21401004 and 21571092), the Natural
Science Foundation of Anhui Province (No. 1508085QB36),
and the National Creative Plan of Students (201810370443).
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