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j.mcat.2018.07.022

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Molecular Catalysis 458 (2018) 9–18
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.elsevier.com/locate/mcat
Aerobic Baeyer-Villiger oxidation of ketones over mesoporous Mn-Ce and
Mn-Co composite oxides in the presence of benzaldehyde: The effect of
valence state
⁎
T
⁎
Gui Liua, Lei Suna, Wei Luoa, Yue Yanga, Junhua Liua, , Fang Wangb, , Curtis J. Guildc
a
College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China
College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, China
c
Department of Chemistry, University of Connecticut, Storrs, CT, 06269, USA
b
A R T I C LE I N FO
A B S T R A C T
Keywords:
Mn-Ce composite oxides
Mn0.33Co0.67Os composite oxide
Oxidation of ketones
Mn2+and Co3+inhibition
Mesoporous materials
Aerobic Baeyer-Villiger oxidation of ketones into corresponding esters were performed over mesoporous Mn-Ce
and Mn-Co composite oxides prepared by co-impregnation method and benzaldehyde was used as the sacrificing
agent. It was found that the best conversion and selectivity were obtained when the Mn/Ce mole ratio was 1:2
(denoted as Mn0.33Ce0.67Os) through investigating the effect of Mn/Ce mole ratio on the catalytic activity.
Interestingly, Mn0.33Co0.67Os (Mn/Co mole ratio was 1:2) catalyst had no catalytic activity for this reaction. Xray diffraction (XRD) results showed that MnOx was completely dissolved into the CeO2 lattice, and
Mn0.33Co0.67Os sample was existed in the form of spinel structure (Co, Mn) (Mn, Co)2O4 and obvious peaks of
Co3O4. Nitrogen adsorption-desorption measurements revealed that Mn0.67Ce0.33Os, Mn0.5Ce0.5Os,
Mn0.33Ce0.67Os and Mn0.33Co0.67Os materials possessed mesoporous structure. X-ray photoelectron spectroscopy
(XPS) analysis showed that the highest concentration of Ce3+ on the surface of Mn0.33Ce0.67Os catalyst, which
could create unsaturated chemical bonds, charge imbalance, and oxygen vacancies on the surface of samples, it
is beneficial to the oxidation reaction. Additionally, XPS data revealed that Mn0.33Ce0.67Os catalyst has great
potential in catalytic oxidation due to the large amount of active oxygen species on the surface. In addition,
manganese and cobalt species on the surface of Mn0.33Co0.67Os are almost present in the form of Mn2+ and Co3+,
it is known that Mn2+ can serve as a potent antioxidant and scavenge the activity of active oxygen species, while
Co3+ ions can prevent the formation of oxygen vacancies and inhibit the release of reactive oxygen species, thus
the presence of Mn2+ and Co3+ inhibited the catalytic activity of Mn0.33Co0.67Os catalyst. The diffuse reflectance
ultraviolet-visible spectroscopy (DR-UV-vis) and hydrogen temperature-programmed reduction (H2-TPR) results
are in accordance XPS data.
1. Introduction
Catalytic Baeyer-Villiger type oxidations of ketones to esters are
very attractive and valuable from an industrial viewpoint [1–5]. In
homogeneous and heterogeneous catalytic systems, several examples of
using aldehydes as sacrificial agents have been demonstrated
[2,3,6–10]. In industrial field, the heterogeneous catalytic systems are
more valuable than homogeneous catalytic systems since the repeatability and easy separation of heterogeneous catalysts. Using O2/aldehyde oxidation system instead of explosive peracetic acid is quite attractive for a variety of reasons [11]. Due to their advantages of easy
preparation, higher thermal stability, and higher metal utilization,
oxides/composite oxides used as catalysts had attracted extensive
⁎
attention of researchers [12–18]. Of these, Mn-Ce composite oxides
have been largely used as catalytic materials by our group and other
researchers, facilitating reactions including oxidation of hydrocarbons,
combustion of volatile organic compounds, and CO oxidation [19–21].
In addition, the oxygen storage capacity and the redox transformation
between Ce3+ and Ce4+ of ceria provide a basis for the formation of
oxygen vacancies [22,23]. The incorporation of manganese into CeO2
lattice can improve the thermal stability and redox properties through
the formation of an effective redox couple with Ce3+/Ce4+ [24].
Moreover, Mn-Ce composite oxides can achieve the mutual solubility
because of the similarity of structure between manganese and cerium
[25], thus the stronger synergistic interactions between MnOx and CeO2
make it possible to provide more active oxygen species [26]. These
Corresponding authors.
E-mail addresses: liujh2007@aliyun.com (J. Liu), wangfang2012@njtech.edu.cn (F. Wang).
https://doi.org/10.1016/j.mcat.2018.07.022
Received 22 May 2018; Received in revised form 13 July 2018; Accepted 22 July 2018
2468-8231/ © 2018 Elsevier B.V. All rights reserved.
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Inductively coupled plasma optical emission spectroscopy (ICP-OES)
analyses were carried out to measure the compositions of Mn, Ce and
Co for the introduced catalysts and the leaching of Mn and Ce species
during the process of cyclic experiments using a Varian ICP-OES 720ES
apparatus.
Scheme 1. Mn0.33Ce0.67Os catalyzed oxidation of ketones to esters.
2.3. Catalyst test
reasons illustrate why Mn-Ce composite oxides are very attractive in
various catalytic applications.
Currently, aerobic Baeyer-Villiger oxidations of ketones to esters
over Mn-Ce composite oxides are rarely reported. In this article, mesoporous Mn-Ce and Mn-Co composite oxides were used as catalysts
coupled with benzaldehyde as a sacrificial agent. Interestingly, Mn-Ce
composite oxides catalysts showed good catalytic activity for BaeyerVilliger oxidations, while Mn0.33Co0.67Os composite oxides catalysts
showed no catalytic activity for this reaction. To the best of our
knowledge, this is a novel and interesting finding. Herein we have investigated the effect of Mn/Ce mole ratio on the catalytic activity, and it
was found that the best conversions were obtained when the Mn/Ce
mole ratio was 1:2. The Mn0.33Ce0.67Os catalyst exhibited high catalytic
activity for the cyclic and aliphatic ketones, however, some catalysts
reported in previous literatures only showed good catalytic activity for
the cyclic ketones [1,27–30]. In addition, mesoporous structures can
expose more surface active oxygen species and accelerate mass transfer
[31]. This study provides a simple tactic to obtain mesoporous Mn-Ce
solid solution catalyst and make O2/aldehyde-based Baeyer-Villiger
oxidations at mild temperatures feasible (Scheme 1 ).
Aerobic Baeyer-Villiger type oxidations of ketones were carried out
in a 100 ml two necked round-bottom flask equipped with a condenser.
In a typical procedure, catalyst (9 mmol%), ketones (6 mmol), benzaldehyde (10 mmol) and solvent (10 ml) were placed into the roundbottom flask, successively. The oxygen was bubbled into the system,
and then the round-bottom flask was heated to the desired temperature
in the oil bath. Then, the reaction was carried out with stirring (stirring
rate: 800 r/min) for a certain time. The reactants and the products were
analyzed by a standardized gas chromatograph (GC 9560) with a SE-54
capillary column. For recycled studies, the used catalysts was removed
by centrifugation and washed with ethanol, followed by drying at 80 °C,
and then subjected to the aerobic Baeyer-Villiger type oxidations of
ketones under the same procedure.
3. Results and discussions
3.1. Catalyst activity
The oxidation of cyclopentanone was examined as a model reaction
for the aerobic Baeyer-Villiger oxidations of ketones to optimize the
reaction conditions (Table 1). The Mn0.33Ce0.67Os catalyst gave the
highest conversion among the eight catalysts in 1, 2-dichloroethane
solvent (Table 1, entries 1–8). Both MnOx and CeO2 (Table 1, entries
1–2) exhibited poor catalytic activity compared with Mn-Ce composite
oxides (except Mn0.67Ce0.33Os catalyst). Interestingly, both MnOx and
CoOx (Table 1, entries 1 and 3) showed a certain catalytic activity,
while Mn0.33Co0.67Os composite oxide has no catalytic activity (Table 1,
entry 8). A solvent study was carried out using different solvents including 1, 2-dichloroethane, toluence, acetonitrile, N, N-Dimethylflformamide, ethanol and ethyl acetate (Table 1, entries 9–13).
Among several solvents, 1, 2-dichloroethane emerged as the best solvent with 64% conversion, whereas ethyl acetate was the secondary
optimal solvent which gave 24% conversion, and other solvents such as
toluence, acetonitrile, N,N-dimethylformamide and ethanol all exhibited unfavorable effect in this reaction. Therefore, 1, 2-dichloroethane was selected as the best solvent as reported in the literatures [9,11]. Next, these reaction conditions were used into the
further tests. Moreover, several experiments were carried out to investigate the reaction mechanism as shown in Table 1, entries 14–16.
To further understand the catalytic activity of Mn0.33Ce0.67Os catalyst, the aerobic oxidation of various ketones over mesoporous
Mn0.33Ce0.67Os was carried out, and the results are shown in Table 2.
Cyclopentanone, cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone and 4-methylcyclohexanone were successfully oxidized to
corresponding esters with high conversion and selectivity (Table 2,
entries 1–5), and 2-methylcyclohexanone had the higher catalytic
performance than 3-methylcyclohexanone or 4-methylcyclohexanone.
This is due to the fact that the methyl group serves as an electrondonating group and has a nearest distance to the oxygen atoms inserted
in 2-methylcyclohexanone. Saturated aliphatic ketones are more difficult to catalyze than cyclic ketones, 10 h for 2-heptanone and 4-heptanone at 60 °C exhibited 30% conversion, 92% selectivity and 35%
conversion, 95% selectivity respectively (Table 2, entries 6 and 7).
While 4-methoxyacetophenone with electron-donating group exhibits
90% conversion and 100% selectivity under the same reaction conditions (Table 2, entry 8).
The reusability of heterogeneous catalysts is of great importance on
industrial applications. The Mn0.33Ce0.67Os catalyst was used five times
2. Experimental
2.1. Materials and methods
Mn (CH3COO)2·4H2O, Ce (NO3)3·6H2O, Co(NO3)2·6H2O and Na2CO3
were purchased from Aladdin Industrial Corporation. Block copolymer
surfactant Pluronic P-123 was purchased from Sigma-Aldrich
Corporation. Mn-Ce composite oxides with different Mn/Ce mole ratio
(Mn/Ce ranging from 2:1 to 1:4) were synthesized by a modified coimpregnation method [32,33]. In the present model system, mesoporous Mn-Ce composite oxides were synthesized by dissolving 4 g of p123 in 20 ml H2O along with a certain amount of Mn (CH3COO)2·4H2O
and Ce (NO3)3·6H2O with vigorous stirring. Na2CO3 solution (1 M) was
added to the above solution to pH of 10. The resulting slurry was stirred
at room temperature for 40 min. The precipitates were filtered, washed
with distilled water, dried at 80 °C overnight under vacuum and calcined at 500 °C for 5 h in air with a heating ramp of 1.5 °C /min. The
obtained materials labeled as MnxCe1-xOs (Where x refers to the Mn/
(Mn + Ce) atomic mole ratio). MnOx, CeO2 and Mn0.33Co0.67Os composite oxide were synthesized by the same procedure.
2.2. Catalyst characterization
The morphologies and lattice fringes of obtained materials were
examined by high-resolution transmission electron microscope
(HRTEM) (JEM-2100) and scanning electron microscopy (SEM) (JSM7600 F). The crystalline aspects of the catalysts were studied by powder
XRD (D/max 2500/PC). The specific BET (Brunauer-Emmett-Teller)
surface area and BJH (Barrett-Joyner-Halenda) pore size distributions
were examined by nitrogen adsorption-desorption measurements at liquid nitrogen temperature using an ASAP 2050 analyzer. Surface
composition was determined by XPS using a K-Alpha-surface Analysis
system with X-Ray Monochromatisation. DR-UV-vis measurements of
the samples were performed at room temperature on a Shimadzu UV3600 spectrometer. H2-TPR of catalysts was conducted on a
Micromeritics 2920 apparatus. Typically, 60 mg of catalysts were
loaded in a quartz tube reactor, then heated from room temperature to
800 °C at a rate of 10 °C /min in a H2-Ar (5:95) gas flow (50 cm3/min).
10
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Table 1
Optimization of reaction conditions for the aerobic Baeyer-Villiger type oxidation of cyclopentanone.a
Entry
Catalyst
Solvent
Conversion (%)b
Selectivity (%)b
1
2
3
MnOx
CeO2
CoOx
Mn0.67Ce0.33Os
Mn0.5Ce0.5Os
Mn0.33Ce0.67Os
Mn0.2Ce0.8Os
Mn0.33Co0.67Os
Mn0.33Ce0.67Os
Mn0.33Ce0.67Os
Mn0.33Ce0.67Os
Mn0.33Ce0.67Os
Mn0.33Ce0.67Os
Mn0.33Ce0.67Os
No catalyst
Mn0.33Ce0.67Os
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
Toluence
Acetonitrile
N,N-Dimethylformamide
Ethanol
Ethyl acetate
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
20
17
25
10
44
64
29
0
0
8.1
0
0
24
0
3.6
1
100
100
100
100
100
100
100
0
0
100
0
0
100
0
100
100
4
5
6
7
8
9
10
11
12
13
14c
15
16d
a
b
c
d
Reaction conditions: catalyst 9 mmol%, cyclopentanone 6 mmol, benzaldehyde 10 mmol, 1,2-dichloroethane 10 ml, O2 flow, 40 °C and 1 h.
Determined by GC.
Presence of radical inhibitor.
Using nitrogen instead of oxygen.
content for Mn-Ce composite oxides, indicating the occurrence of lower
degree of crystallinity and smaller-sized crystallites with the increase of
Mn content. The lattice parameters and crystallite size calculated by
Scherrer Equation are shown in Table 5. Additionally a series of sharp
and intensive diffractions at 2θ = 19.0°, 31.2°, 36.9°, 44.6°, 59.4° and
65.2° for the pure CoOx (Fig. 1A (h)) could be indexed to cubic Co3O4
(PDF# 43-1003). However, a typical diffraction peak at 2θ = 36.4° for
Mn0.33Co0.67Os (Fig. 1A (g)) sample due to the formation of spinel
structure (Co, Mn) (Mn, Co)2O4 [35], the diffractions at 2θ = 31.2°,
44.6°, 59.4° and 65.2° corresponding to Co3O4 (PDF# 43-1003) are
visible. Thus, it can be seen from Fig. 1A (g) that spinel structure (Co,
Mn) (Mn, Co)2O4 and Co3O4 phase are coexistence in Mn0.33Co0.67Os
composite oxide.
The porous natures and BET surface areas were evaluated by nitrogen sorption measurements as shown in Fig. 2. The values of BET
surface areas and average pore diameter are summarized in Table 6.
The Mn0.67Ce0.33Os (a), Mn0.5Ce0.5Os (b), Mn0.33Ce0.67Os (c) and
Mn0.33Co0.67Os (e) materials possessed a type IV isotherms with H3-type
hysteresis loop, which is a typical characteristic of mesoporous structure [36] with BET surface areas are ranged in the interval of 2198 m2· g–1. The average pore diameter located in the range of 8–24 nm.
However, the Mn0.2Ce0.8Os (d) sample possessed a smaller surface area
of 38 m2 g−1 compared with other Mn-Ce composite oxides and its
mesoporous structure was not obvious as shown in Fig. 2B. In addition,
Mn0.33Co0.67Os material had the least surface area of 21 m2· g–1 comparing with all the Mn-Ce composite oxides.
The SEM and HRTEM characterizations were performed to study the
morphologies and crystalline structures of the samples. Fig. 3a–h shows
the HRTEM images of various materials. Obviously, Fig. 3a shows the
lattice spacing of MnOx is 0.27 nm, which can be ascribed to (222)
planes of Mn2O3 [34]. Moreover, only (111) and (220) planes assigned
to CeO2 [30,33] can be obtained in Mn-Ce composite oxides from
Fig. 3b–e. This further proves that MnOx has completely entered into
CeO2 lattice. Fig. 3f exhibits the HRTEM micrograph of CeO2 is mainly
enclosed by (111) planes through measuring the lattice spacing between the clear stripes [37]. Fig. 3g exhibits the HRTEM image of CoOx
sample, the lattice spacing between the fringes were measured to be
for the oxidation of cyclopentanone, without significant loss in catalytic
activity was found (Table 3). ICP analysis showed that the leaching
amount of Mn and Ce species after five cycles was negligible (lower
than the detection limit). XRD studies of fresh Mn0.33Ce0.67Os and recycled Mn0.33Ce0.67Os catalysts were performed (Supporting Information, Fig. S1). To our delight, XRD patterns indicate that the peak positions of fresh and recycled Mn0.33Ce0.67Os catalysts are same and the
peak intensity of recycled Mn0.33Ce0.67Os catalyst is slightly lower than
that of fresh one, which suggests that the composition tolerance of the
Mn0.33Ce0.67Os catalyst is very strong.
3.2. Catalyst characterization
The compositions of Mn and Ce for Mn0.67Ce0.33Os, Mn0.5Ce0.5Os,
Mn0.33Ce0.67Os, Mn0.2Ce0.8Os and Mn0.33Co0.67Os samples are listed in
Table 4. As observed by the Table 4, it is believed that the actual
compositions of the introduced catalysts are quite similar to that of we
expected.
Fig. 1shows the XRD patterns of MnOx, CeO2, CoOx, Mn-Ce and
Mn0.33Co0.67Os composite oxides. In the case of pure CeOx (Fig. 1A (e)),
the diffractions at 2θ = 28.5°, 33.1°, 47.5° and 56.3°clearly demonstrate
the presence of cubic fluorite structure of CeO2 (PDF# 34-0394). For
pure MnOx (Fig. 1A (f)), the sharp and intensive diffraction peaks at
2θ = 23.1°, 32.9°, 38.2°, 45.1°, 49.4°, 55.2° and 65.8° could be attributed to Mn2O3 (PDF# 41-1442). However, in Mn-Ce composite oxides
(Fig. 1A (a–d)), only broad diffractions assigned to CeO2 are obtained.
This indicates that MnOx is completely dissolved into the CeO2 lattice,
thus MnOx-CeO2 solid solution was formed between MnOx and CeO2
[34]. The diffraction patterns of CeO2 in Mn-Ce composite oxides
showed a clear shift to higher Bragg angles comparing with pure CeO2
(Fig. 1B). This is reasonable because the ionic radius of Mnx+ (Mn4+:
0.053 nm; Mn3+: 0.065 nm; Mn2+: 0.083 nm) are smaller in size than
that of Cex+ (Ce4+: 0.097 nm; Ce3+: 0.114 nm), and the lattice parameters of CeO2 would be decreased after the incorporation of smaller
Mnx+ cations, thus diffraction patterns of CeO2 in Mn-Ce composite
oxides are slightly shifted to higher values (Fig. 1B) [34]. In addition,
the diffraction peaks become wider and shorter with the increase of Mn
11
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Table 2
Aerobic Baeyer-Villiger oxidations of various ketones to esters using mesoporous Mn0.33Ce0.67Os catalyst.a
Time (h)
Conv. (%)b
Sel. (%)b
1
2
90
100
2
1
62
100
3
1
90
100
4
1
82
100
5
1
80
100
6c
10
30
92
7c
10
35
95
8c
10
90
100
Entry
a
b
c
Substrate
Product
Reaction conditions: Mn0.33Ce0.67Os catalyst 9 mmol%, substrate 6 mmol, benzaldehyde 10 mmol, 1,2-dichloroethane 10 ml, O2 flow, 40 °C and 1 h.
Determined by GC.
Reaction temperature is 60 °C.
Table 3
Recyclability of the mesoporous Mn0.33Ce0.67Os catalyst in catalytic oxidation
of cyclopentanone.a
Table 4
Quantitative component data of Mn-Ce composite oxides and Mn0.33Co0.67Os
sample obtained from ICP-OES.
Sample
Mn/ (Mn + Ce (Co)) (%)a
Ce (Co)/ (Mn + Ce (Co)) (%)a
Mn0.67Ce0.33Os
Mn0.5Ce0.5Os
Mn0.33Ce0.67Os
Mn0.2Ce0.8Os
Mn0.33Co0.67Os
0.669
0.492
0.329
0.195
0.321
0.331
0.508
0.671
0.805
0.679
a
Cycle
1 st
2nd
3rd
4th
5th
Yield (%)b
90
90
89
88
88
Atomic mole ratio.
Fig. 3i–p exhibits the typical SEM micrographs of MnOx, CeO2,
CoOx, Mn-Ce and Mn0.33Co0.67Os composite oxides. As can be seen from
these SEM images, the morphology of various materials is still different.
Fig. 3i shows the globe-shaped structure for MnOx. For Mn-Ce composite oxides, the spherical particles are evidently inserted into CeO2
lattice and the morphologies of the samples can be clearly defined from
Fig. 3j–m, and the distribution of Mn-Ce composite oxides particles is
more uniform than CeO2 lattice (Fig. 3n), which is in accordance with
previous literature [39]. In addition, the particle size of Mn-Ce
a
Reaction conditions: Mn0.33Ce0.67Os catalyst 9 mmol%, cyclopentanone
6 mmol, benzaldehyde 10 mmol, 1,2-dichloroethane 10 ml, O2 flow and 40 °C.
b
Determined by GC.
about 0.24 nm corresponding to (311) planes of Co3O4 [35]. Correspondingly, (311) and (111) planes are ascribed to (Co, Mn) (Mn,
Co)2O4 [35] and Co3O4 [38] respectively for Mn0.33Co0.67Os sample in
Fig. 3h. The above analysis is consistent with the XRD data.
12
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Fig. 1. (A) Wild angle XRD patterns of (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os, (d) Mn0.2Ce0.8Os, (e) CeO2, (f) MnOx, (g) Mn0.33Co0.67Os and (h) CoOx
catalysts; (B) enlarged-zone XRD patterns of catalysts (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os, (d) Mn0.2Ce0.8Os and (e) CeO2.
the Mn 2p3/2 state were split into two peaks at around 643.5 eV and
641.5 eV for Mn0.33Ce0.67Os and Mn0.2Ce0.8Os catalysts, suggesting the
coexistence of Mn4+ and Mn3+ species [42], but Mn4+ dominate the
surface. Besides a large number of Mn4+ and Mn3+, the Mn0.5Ce0.5Os
catalyst surface contains a small amount of Mn2+. For Mn0.33Co0.67Os
sample, Mn 2p3/2 state at 640.6 eV is ascribed to Mn2+ [41]. According
to previous literatures [43–45], Mn2+ is a potent antioxidant and can
scavenge the activity of active oxygen species. The relative atomic ratio
of Mn2+/ (Mn2++Mn3++Mn4+) (48%) on the surface of
Mn0.33Co0.67Os is one of the main reasons why Mn0.33Co0.67Os catalyst
had no activity in this aerobic Baeyer-Villiger oxidations. The concentration of Mn4+ at the surface of Mn0.67Ce0.33Os, Mn0.5Ce0.5Os,
Mn0.33Ce0.67Os, Mn0.2Ce0.8Os and Mn0.33Co0.67Os catalysts are ca. 16%,
68%, 86%, 84% and 16% respectively. According to previous reports
[19,46], highly reducible Mn4+ ions at the catalyst surface were responsible for catalytic oxidations.
Ce 3d XPS spectra analysis was carried out to characterize the oxidation state of Ce. Fig. 4B shows the Ce 3d XPS curves of Mn-Ce
composite oxides. Ce 3d XPS spectra were resolved into eight easily
distinguishable peaks. As shown in Fig. 4B, the marks of V and U indicate the spin-orbit coupling of Ce 3d3/2 and Ce 3d5/2, respectively. In
detail, the six peaks marked as V (ca. 918 eV), V’ (ca. 908 eV), V”’
(ca.900 eV), U (ca. 898 eV), U’ (ca. 889 eV) and U”’ (ca. 882.3 eV) are
assigned to the Ce4+ state, whereas the remaining two peaks denoted as
V” (ca. 903 eV) and U” (ca. 884.3 eV) are the characteristic peaks attributed to Ce3+ ions [36,47]. Thus, the peaks of V” and U” evidence
the coexistence of Ce4+ and Ce3+ in the Mn-Ce composite oxides. An
interesting observation noticed from Fig. 4B is that the surface atomic
concentrations of the Ce3+ for Mn0.33Ce0.67Os catalyst is considerably
higher compared with other three Mn-Ce composite oxides, indicating
the existence of strong synergistic interaction between MnOx and CeO2
Table 5
The crystallite size (D) and lattice parameter (a) values based on (111) crystal
plane of CeO2, Mn0.2Ce0.8Os, Mn0.33Ce0.67Os, Mn0.5Ce0.5Os and Mn0.67Ce0.33Os
samples.
Samples
CeO2
Mn0.2Ce0.8Os
Mn0.33Ce0.67Os
Mn0.5Ce0.5Os
Mn0.67Ce0.33Os
D/nm
a/ Å
7.37
5.450
4.90
5.301
4.52
5.289
4.73
5.291
3.39
5.283
composite oxides (Fig. 3j-m) is smaller than that of CeO2 (Fig. 3n),
which can be due to the doping of Mnx+ into CeO2 inhibits the growth
of CeO2 lattice [25,40]. Fig. 3 (o and g) shows the spherical structure
with an average diameter of around 20 nm for CoOx. However,
Mn0.33Co0.67Os sample has an irregular lamellar morphology with a
thickness of ca.100 nm and a length of about 300 nm.
In order to study the oxidation state of catalyst surface species, XPS
spectra of O 1 s, Mn 2p, Ce 3d and Co 2p core levels of Mn-Ce composite
oxides, Mn0.33Co0.67Os and CoOx sample were obtained and shown in
Fig. 4. Fig. 4A shows the Mn 2p XPS spectra of Mn-Ce composite oxides
and Mn0.33Co0.67Os. Interestingly, the peaks corresponding to Mn 2p1/2
and Mn 2p3/2 states of each catalysts are different, which exhibit at
652.8 eV and 641.2 eV, 655 eV and 643.4 eV, 655.2 eV and 643.7 eV,
655.2 eV and 643.4 eV, 652.7 eV and 640.6 eV for Mn0.67Ce0.33Os,
Mn0.5Ce0.5Os, Mn0.33Ce0.67Os, Mn0.2Ce0.8Os and Mn0.33Co0.67Os samples, respectively. It can be attributed to the different oxidation states of
Mn. In the case of Mn0.67Ce0.33Os, 641.2 eV for Mn 2p3/2 corresponds to
Mn2O3, which is consistent with previous literature [25]. Mn 2p3/2 peak
of Mn0.67Ce0.33Os sample is broad and asymmetrical, and can be fitted
into three peaks located at about 643.1 eV, 641.4 eV and 640 eV corresponding to Mn4+, Mn3+, and Mn2+ respectively [41]. In addition,
Fig. 2. (A) N2 adsorption-desorption curves and (B) pore size distributions of (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os, (d) Mn0.2Ce0.8Os and (e)
Mn0.33Co0.67Os catalysts.
13
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Table 6
The BET surface area (SBET) and average pore diameter (dpor) values of Mn0.67Ce0.33Os, Mn0.5Ce0.5Os, Mn0.33Ce0.67Os, Mn0.2Ce0.8Os and Mn0.33Co0.67Os samples.
Samples
2
SBET /m · g
dpor /nm
–1
Mn0.67Ce0.33Os
Mn0.5Ce0.5Os
Mn0.33Ce0.67Os
Mn0.2Ce0.8Os
Mn0.33Co0.67Os
55
17
98
8
75
11
38
4
21
24
most important in the process of catalytic oxidation among the three
oxygen species [21,38,50,51]. The atomic ratios of Osur for all the
samples were calculated by integrating the peak areas as shown in
Table 7. Mn0.33Ce0.67Os and Mn0.5Ce0.5Os catalysts own the most Osur
with 77% and 78% respectively, suggesting these two catalysts have
great potential in catalytic oxidation processes. However, a small
amount of Mn2+ played a certain inhibitory role in the oxidation reaction of the Mn0.5Ce0.5Os catalyst.
Co 2p XPS characterization was carried out on the CoOx and
Mn0.33Co0.67Os samples. The fine-scanned Co 2p3/2 XPS curve of CoOx
and Mn0.33Co0.67Os were illustrated in Fig. 4C. The peaks at around
780 eV and 796 eV are assigned to Co 2p3/2 and Co 2p1/2 states, respectively. The Co 2p curves were resolved into five peaks, in which the
signal located at binding energy (BE) = ca. 779.2 eV were ascribed to
surface Co3+ presence, and the peaks at BE = ca. 781.4 eV together
with satellite peaks centered at around 785.4 eV and 802.8 eV were
in Mn0.33Ce0.67Os catalyst. The specific surface atomic concentrations of
Ce3+ are about 8.5%, 21%, 36.3% and 15% for Mn0.67Ce0.33Os,
Mn0.5Ce0.5Os, Mn0.33Ce0.67Os and Mn0.2Ce0.8Os samples respectively.
The presence of Ce3+ ions can create unsaturated chemical bonds,
charge imbalance and oxygen vacancies on the surface of samples [47],
which can accelerate the release of active oxygen species during the
oxidation reaction [48].
The XPS curves of O 1s (Fig. 4D) for all the samples with the
shoulder peaks are very broad, possibly due to the overlapping of different oxygen species. All the curves were then fitted into three peaks,
the peaks at the binding energy of about 528, 530 and 532 eV are
corresponding to lattice oxygen atoms (Olatt, O2−), surface oxygen
species (Osur, O2−, O22−, or O−) and adsorbed hydroxyl, water or
carbonate species on the surface of the catalysts (Oads), respectively
[19,49]. It is well known in the literatures that surface oxygen species
(Osur) derived from defective sites with unsaturated structures are the
Fig. 3. HRTEM images of catalysts (a) MnOx, (b) Mn0.67Ce0.33Os, (c) Mn0.5Ce0.5Os, (d) Mn0.33Ce0.67Os, (e) Mn0.2Ce0.8Os, (f) CeO2, (g) CoOx and (h) Mn0.33Co0.67Os;
SEM micrographs of (i) MnOx, (j) Mn0.67Ce0.33Os, (k) Mn0.5Ce0.5Os, (l) Mn0.33Ce0.67Os, (m) Mn0.2Ce0.8Os, (n) CeO2, (o) CoOx and (p) Mn0.33Co0.67Os samples.
14
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Fig. 4. X-ray photoelectron spectra of (A) Mn 2p and (C) O 1 s of catalysts (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os, (d) Mn0.2Ce0.8Os and (e)
Mn0.33Co0.67Os; (B) Ce 3d of catalysts (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os and (d) Mn0.2Ce0.8Os; (D) Co 2p of (a) CoOx and (b) Mn0.33Co0.67Os
samples.
oxidation states and surface coordination environment. The DR-UV-vis
spectra of CeO2 is shown in Fig. 5A, four narrow bands in the range of
250–350 nm were obtained, which can be assigned to O-Ce charge
transfer transitions in CeO2 relate to surface Ce4+ with different coordination numbers [56]. The low-intensity bands centered at around
253 and 284 nm are ascribed to O2−→ Ce3+ charge-transfer [21,57] in
Fig. 5C, suggesting the coexistence of Ce3+ and Ce4+ on the surface of
Mn-Ce composite oxides and the atomic ration of Ce3+/Ce4+ for
Mn0.33Ce0.67Os is higher than that of other Mn-Ce composite oxides. In
addition, the obtained absorption peaks in the range of 250–350 nm
from Fig. 5B are considerably higher than that of pure CeO2 (Fig. 5A)
and the intensity of adsorption for Mn0.33Ce0.67Os (Fig. 5Bc) is the
strongest, which shows that lattice defects are formed in the process of
incorporation of manganese and most defects exist in the
Mn0.33Ce0.67Os lattice [58]. As can be seen from Fig. 5B, the continuous
absorption peaks between 400 and 500 nm are assigned to the characteristic absorption of Mn4+ [59]. The weak absorption band at about
585 nm for Mn0.67Ce0.33Os and Mn0.5Ce0.5Os samples is associated to
the 6A1→4T1 forbidden d-d transition of Mn2+ [60]. The last absorption
bands centered at around 730 nm could be assigned to Mn3+ [60].
Further, DR-UV-vis spectra of Mn0.33Co0.67Os and CoOx (Fig. 5D)
were used to testify the oxidation state of Co and Mn. The presence of
broad peak at 700–740 nm for CoOx is the typical feature of Co3O4
[61,62]. Additionally weak peaks at around 540 nm and 630 nm are
ascribed to the electronic ligand-field 4A2(F)→ 4T1(P) transition of
tetrahedrally coordinated Co2+, whereas the absorption peaks centered
at about 420 nm and 670 nm can be assigned to the octahedrally coordinated Co3+ [62,63]. However, the absorption peaks corresponding
to Co2+ of Co3O4 are slightly stronger than that of Mn0.33Co0.67Os and
the absorption peaks assigned to Co3+ are contrary to Co2+. Where the
absorption bands corresponding to Mnx+ in Mn0.33Co0.67Os are same
with Mn-Ce composite oxides and the absorption band assigned to
Table 7
XPS results of O 1 s for Mn-Ce composite oxides and Mn0.33Co0.67Os catalyst.
Samples
Mn0.67Ce0.33Os
Mn0.5Ce0.5Os
Mn0.33Ce0.67Os
Mn0.2Ce0.8Os
Mn0.33Co0.67Os
BE (eV)
Osur/ (Olatt + Osur + Oads) (%)
Olatt
Osur
Oads
528.7
528.7
528.4
528.8
528.7
530.7
530.5
530.7
530.6
530.2
532.2
532.7
533
532.5
532
35
78
77
68
70
assigned to surface Co2+ presence [52,53]. The Co2+/ (Co2++Co3+)
molar ratio on the surface of CoOx and Mn0.33Co0.67Os samples were
calculated by comparing the fitted curves area. It could be clearly obtained that the Co2+/ (Co2++Co3+) molar ratio are 53% and 10% for
CoOx and Mn0.33Co0.67Os respectively, indicating that the Co ions on
the surface of Mn0.33Co0.67Os almost present in the form of Co3+. According to previous literatures [38,54], Co3+ ions can prevent the
formation of oxygen vacancies. Oxygen vacancies are favorable to accelerate the adsorption and decomposition of oxygen molecules, which
can lead to the production of reactive oxygen species on the catalyst
surface [55]. Thus the presence of Mn2+ and Co3+ make the
Mn0.33Co0.67Os catalyst lose its catalytic activity in the aerobic BaeyerVilliger type oxidations. However, the atomic ratio of Co2+/Co3+ for
CoOx catalyst is considerably higher than that of Mn0.33Co0.67Os, which
plays a key role in the formation of oxygen vacancies on the surface of
CoOx catalyst [54]. Based on the above XPS analysis, we could find that
the Co2+ were oxidized by reducible Mn4+ and Mn3+ on the
Mn0.33Co0.67Os catalyst surface, and thus resulted in that the manganese and cobalt ions on the surface of Mn0.33Co0.67Os catalyst were
mainly in the form of Mn2+ and Co3+, respectively.
The DR-UV-vis study has been used to investigate the various
15
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Fig. 5. DR-UV-vis spectra of (A) pure CeO2, (B) catalysts (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os and (d) Mn0.2Ce0.8Os; (C) enlarged-zone DR-UV-vis
spectra of (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c) Mn0.33Ce0.67Os and (d) Mn0.2Ce0.8Os samples; (D) catalysts (a) Co3O4 and (b) Mn0.33Co0.67Os.
Mn3+ overlaps with the typical absorption band of Co3O4. The DR-UVvis results are almost consistent with the XPS data.
Fig. 6 shows the H2-TPR profiles of Mn-Ce composite oxides and
Mn0.33Co0.67Os composite oxide in the temperature range 50–800 °C.
Obviously, Mn-Ce composite oxides exhibited one reduction region at
low temperature and Mn0.33Co0.67Os sample showed two reduction
regions at low temperature and high temperature respectively. In the
case of Mn0.33Co0.67Os catalyst, the reduction signal at low temperature
(350 °C) is attributed to the active oxygen species on the catalyst surface and the reduction region at high temperature (447 °C) is assigned
to reduction process of the spinel structure [64], which is in accordance
with XRD data. An interesting observation obtained from Fig. 6 is that
the reduction peak starts at 220 °C, which is the lowest among other
Mn-Ce composite oxides, in other words, the formation energy of
oxygen vacancy for Mn0.33Co0.67Os catalyst is the lowest comparing
with other Mn-Ce composite oxides [65]. In addition, the concentration
of active oxygen species for Mn0.33Co0.67Os catalyst is considerably
higher than Mn-Ce composite oxides, which can be easily obtained from
Fig. 6. However, Mn0.33Co0.67Os catalyst has no catalytic activity in the
aerobic oxidation of ketones, which further indicates that a large
number of Co3+ can prevent the formation of oxygen vacancies, and
thus inhibit the release of active oxygen species. Further, in the
Mn0.67Ce0.33Os composite oxide, the reduction signal shows two peaks
at 338 and 384 °C with the area ratio of about 1:2, it is the typical twostep reduction characteristic of Mn2O3 [66]. For Mn0.5Ce0.5Os,
Mn0.33Ce0.67Os and Mn0.2Ce0.8Os catalysts, the first reduction peaks in
the range of 306–328 °C are attributed to the reduction of MnO2 to
Mn3O4 [64] and the higher reduction temperatures in the range of
352–380 °C are ascribed to the reduction of Mn3O4 to MnO [66]. Besides, the reduction temperature of Mn0.33Ce0.67Os and Mn0.2Ce0.8Os
catalysts are also lower than those of Mn0.5Ce0.5Os and Mn0.67Ce0.33Os
samples, but the H2 consumption of Mn0.2Ce0.8Os (19 cm3/g) is considerably lower than that of Mn0.33Ce0.67Os (34 cm3/g), suggesting the
amount of active oxygen species for Mn0.2Ce0.8Os is lower than that of
Mn0.33Ce0.67Os catalyst. These data as described above are consistent
Fig. 6. H2-TPR profiles of catalysts (a) Mn0.67Ce0.33Os, (b) Mn0.5Ce0.5Os, (c)
Mn0.33Ce0.67Os, (d) Mn0.2Ce0.8Os and (e) Mn0.33Co0.67Os.
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Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
Scheme 2. Mechanism of the O2/aldehyde-based Baeyer–Villiger oxidations of ketones to esters catalyzed by mesoporous Mn0.33Ce0.67Os catalyst.
also can be supported by the observation that the oxidation reaction
almost did not occur when the reaction was carried out using nitrogen
instead of oxygen (Table 1, entry 16).
The peroxybenzoic acid species was then generated by the reaction
between the peroxybenzoic radical and benzaldehyde [70], which is the
real oxidant in the aerobic Baeyer-Villiger oxidations. An easy nucleophilic attack of peroxybenzoic acid species at the activated carbonyl
bond with the formation of a Criegee adduct, followed by a rearrangement, making reconstruction of carbonyl group with the departure of a molecular of benzoic acid to form corresponding esters,
which is similar to the previous reports [73,74].
with the XPS results.
3.3. Mechanism investigation
According to the above experimental results and previous findings,
we hereby propose a possible reaction mechanism for the O2/aldehydebased Baeyer-Villiger type oxidations of ketones to esters with mesoporous Mn0.33Ce0.67Os catalyst (Scheme 2 ). Because the Baeyer-Villiger
oxidation reaction is greatly affected by the acidic environment [67],
many literatures believe that the reaction starts from the process of
oxidation of benzaldehyde to peroxybenzoic acid [1,68,69]. Several
experiments were conducted to deeply understand the mechanistic
details of this Baeyer-Villiger oxidation reaction. The oxidation reaction
was completely inhibited in the presence of 2, 6-di-tert-butyl-4-methylphenol (a radical inhibitor) (Table 1, entry 14). That is to say the
Baeyer-Villiger oxidation reaction involved a radical pathway. The
formation of peroxybenzoic radical species originated from benzaldehyde through transferring an electron to the Mn or Ce centers [70], and
then combined Osur or molecular oxygen (the former was supported by
the observation that the reaction rate was greatly diminished in the
absence of catalyst (Table 1, entry 15) and the latter is similar to a
previous literature [11]). The transferred electrons caused the reduction of active Mn or Ce centers on the surface of catalyst (Mn4+ →
Mn3+ or Ce4+ → Ce3+), which can lead to the facile release of active
oxygen species from the surface of catalyst [71] and thereby accelerate
the formation of peroxybenzoic radical species. Interestingly, the oxidation reaction did not completely stop without catalyst, this is due to
the carbonyl radical could be formed in the presence of benzaldehyde
and O2 [72], then another molecular of O2 was inserted into the carbonyl radical to produce the peroxybenzoic radical species [11]. The
oxygen molecules supplied from the external environment play two
crucial roles in this catalytic process: (1) replenish the lost active
oxygen species on the catalyst surface accompanied by the reoxidation
of Mn or Ce centers (Mn3+ → Mn4+ or Ce3+ → Ce4+), and (2) are used
directly into the manufacture of peroxybenzoic radical species. This
4. Conclusions
In summary, we have synthesized a series of mesoporous Mn-Ce and
Mn0.33Co0.67Os composite oxides through a simple, effective co-impregnation strategy. Then these materials were used into the aerobic
Baeyer-Villiger oxidations, which have achieved favorable yields. When
the Mn/Ce mole ratio was 1:2 (Mn0.33Ce0.67Os), best catalytic activity
was obtained among Mn-Ce composite oxides, but Mn0.33Co0.67Os
sample showed no catalytic activity for this reaction. According to the
XPS and DR-UV-vis analysis, the manganese and cobalt species on the
surface of Mn0.33Co0.67Os catalyst are mainly in the form of Mn2+ and
Co3+, which can provide a powerful evidence that Mn2+ could be used
as an antioxidant and Co3+ ions can prevent the formation of oxygen
vacancies, and thus inhibit the release of reactive oxygen species from
the catalyst surface, it was rarely reported in the literature. This is the
main reason why Mn0.33Co0.67Os sample had no activity in aerobic
Baeyer-Villiger oxidations. In addition, XRD, XPS, SEM, TEM, DR-UVvis and H2-TPR studies have shown several unique characteristics of
Mn0.33Ce0.67Os catalyst: (1) A high proportion (77%) surface active
oxygen species promotes the formation of peroxybenzoic radical species; (2) the incorporation of 33 mol% Mn into CeO2 lattice forms a
Mn0.33Ce0.67Os solid solution very well, thus could have the stronger
synergistic interaction of MnOx and CeO2 that can reduce the formation
17
Molecular Catalysis 458 (2018) 9–18
G. Liu et al.
energy of oxygen vacancies; (3) the atomic concentrations of the Ce3+
on the surface of Mn0.33Ce0.67Os catalyst is considerably higher
(36.3%), that is very favorable for the formation of oxygen vacancies on
the surface of catalyst. These three unique characteristics provide the
possibility that the aerobic Baeyer-Villiger oxidation could be carried
out at mild conditions. That is to say, the highest concentrations of
Ce3+ and active oxygen species on the surface of Mn0.33Ce0.67Os catalyst play the positive role in oxidation reaction, Mn2+ and Co3+ species
inhibit the catalytic activity of Mn0.33Co0.67Os catalyst in aerobic
Baeyer-Villiger oxidation reaction. Besides, we have proposed a possible reaction mechanism for the O2/aldehyde-based Baeyer-Villiger
oxidations of ketones to esters over Mn0.33Ce0.67Os catalyst.
[25] M. Machida, M. Uto, D. Kurogi, T. Kijima, Chem. Mater. 12 (2000) 3158–3164.
[26] G. Liu, J. Liu, W. Li, C. Liu, F. Wang, J. He, C. Guild, J. Jin, D. Kriz, S.L. Suib, Appl.
Catal. A Gen. 535 (2017) 77–84.
[27] K. Kaneda, S. Ueno, T. Imanaka, J. Chem. Soc. Chem. Commun. 7 (1994) 797–798.
[28] R. Kumar, P.P. Das, A.S. Al-Fatesh, A.H. Fakeeha, J.K. Pandey, B. Chowdhury, Catal.
Commun. 74 (2016) 80–84.
[29] A. Corma, M.T. Navarro, M. Renz, J. Catal. 219 (2003) 242–246.
[30] J. Olszówka, R. Karcz, B. Napruszewska, E. Bielańska, R. Dula, M. Krzan,
M. Nattich-Rak, R.P. Socha, A. Klimek, K. Bahranowski, E.M. Serwicka, Appl. Catal.
A Gen. 509 (2016) 52–65.
[31] Y. Wan, H. Yang, D. Zhao, Acc. Chem. Rev. 39 (2006) 423–432.
[32] Y. Liao, M. Fu, L. Chen, J. Wu, B. Huang, D. Ye, Catal. Today 216 (2013) 220–228.
[33] M. Abecassis-Wolfovich, M.V. Landau, A. Brenner, M. Herskowitz, J. Catal. 247
(2007) 201–213.
[34] Z. Wang, G. Shen, J. Li, H. Liu, Q. Wang, Y. Chen, Appl. Catal. B: Environ. 138
(2013) 253–259.
[35] W. Tang, X. Wu, S. Li, W. Li, Y. Chen, Catal. Commun. 56 (2014) 134–138.
[36] Y. Yu, L. Zhong, J. Ding, W. Cai, Q. Zhong, RSC Adv. 5 (2015) 23193–23201.
[37] D. Gao, Y. Zhang, Z. Zhou, F. Cai, X. Zhao, W. Huang, Y. Li, J. Zhu, P. Liu, F. Yang,
G. Wang, X. Bao, J. Am. Chem. Soc. 139 (2017) 5652–5655.
[38] Y. Liu, H. Dai, J. Deng, S. Xie, H. Yang, W. Tan, W. Han, Y. Jiang, G. Guo, J. Catal.
309 (2014) 408–418.
[39] H. Li, X. Tang, H. Yi, L. Yu, J. Rare Earth 28 (2010) 64–68.
[40] G.S. Qi, R.T. Yang, J. Phys. Chem. B 108 (2004) 15738–15747.
[41] P. Sudarsanam, B. Hillary, M.H. Amin, S.B.A. Hamid, S.K. Bhargava, Appl. Catal. B:
Environ. 185 (2016) 213–224.
[42] B. Dutta, S. Biswas, V. Sharma, N.O. Savage, S.P. Alpay, S.L. Suib, Angew. Chem.
128 (2016) 2211–2215.
[43] X. Yin, X. Zhang, Q. Lin, Y. Feng, Yu W, Q. Zhang, Arkivoc 9 (2004) 66–78.
[44] G. Bilaspuri, A.K. Bansal, Archiv fur Tierzucht 51 (2008) 149–158.
[45] S. Giuffrida, G. De Guidi, P. Miano, S. Sortino, G. Condorelli, L.L. Costanzo, J. Inorg.
Biochem. 63 (1996) 253–263.
[46] M. Fu, J. Lin, W. Zhu, J. Wu, L. Chen, B. Huang, D. Ye, J. Rare Earths 32 (2014)
153–158.
[47] S. Yang, W. Zhu, Z. Jiang, Z. Chen, J. Wang, Appl. Surf. Sci. 252 (2006) 8499–8505.
[48] L. Chen, J. Li, M. Ge, J. Phys. Chem. C 113 (2009) 21177–21184.
[49] X. Gao, Y. Jiang, Y. Zhong, Z. Luo, K. Cen, J. Hazard. Mater. 174 (2010) 734–739.
[50] W. Tan, G. Guo, J. Deng, S. Xie, H. Yang, W. Tan, W. Han, Y. Jiang, G. Guo, Ind.
Eng. Chem. Res. 53 (2014) 18452–18461.
[51] H. Li, C. Wu, Y. Li, J. Zhang, Environ. Sci. Technol. 45 (2011) 7394–7400.
[52] L.F. Liotta, G. Di Carlo, G. Pantaleo, A.M. Venezia, G. Deganello, Appl. Catal. B 66
(2006) 217–227.
[53] J. Zhu, K. Kailasam, A. Fischer, A. Thomas, ACS Catal. 1 (2011) 342–347.
[54] L. Xu, Q. Jiang, Z. Xiao, X. Li, J. Huo, S. Wang, L. Dai, Angew. Chem. 128 (2016)
5363–5367.
[55] M.M. Schubert, S. Hackenberg, A.C.V. Veen, M. Muhler, V. Plzak, R.J. Behm, J.
Catal. 197 (2001) 113–122.
[56] A. Bensalem, F. Bozon-Verduraz, M. Delamar, G. Bugli, Appl. Catal. A Gen. 121
(1995) 81–93.
[57] D. Hari Prasad, S.Y. Park, H.I. Ji, H.R. Kim, J.W. Son, B.K. Kim, H.W. Lee, J.H. Lee,
J. Phys. Chem. C 116 (2012) 3467–3476.
[58] G.R. Rao, H.R. Sahu, J. Chem. Sci. 113 (2001) 651–658.
[59] J.B. Macstre, E.F. López, J.M. Gallardo-Amores, R.R. Casero, V.S. Escribano,
E.P. Bernal, Int. J. Inorg. Mater. 3 (2001) 889–899.
[60] F. Milella, J.M. Gallardo-Amores, M. Baldi, G. Busca, J. Mater. Chem. 8 (1998)
2525–2531.
[61] G.A.H. Mekhemer, H.M.M. Abd-Allah, S.A.A. Mansour, Colloids Surf. A 160 (1999)
251–259.
[62] M. Herrero, P. Benito, F.M. Labajos, V. Rives, J. Solid State Chem. 180 (2007)
873–884.
[63] A.P. Katsoulidis, D.E. Petrakis, G.S. Armatas, P.N. Trikalitis, P.J. Pomonis,
Microporous Mesoporous Mater. 92 (2006) 71–80.
[64] M.H. Castaño, R. Molina, S. Moreno, Appl. Catal. A Gen. 492 (2015) 48–59.
[65] W. Cen, Y. Liu, Z. Wu, H. Wang, X. Weng, Phys. Chem. Chem. Phys. 14 (2012)
5769–5777.
[66] X.F. Tang, J.L. Chen, Y.G. Li, Y. Li, Y.D. Xu, W.J. Shen, Chem. Eng. J. 118 (2006)
119–125.
[67] F. Grein, A.C. Chen, D. Edwards, C.M. Crudden, J. Org. Chem. 71 (2006) 861–872.
[68] S. Chen, X. Zhou, H. Ji, Catal. Today 264 (2016) 191–197.
[69] A. Sinhamahapatra, A. Sinha, S.K.Pahari.N. Sutradhar, H.C. Bajaj, A.B. Panda,
Catal. Sci. Technol. 2 (2012) 2375–2382.
[70] R. Raja, G. Sankar, J.M. Thomas, Chem. Commun. 9 (1999) 829–830.
[71] V.D. Makwana, Y.-C. Son, A.R. Howell, S.L. Suib, J. Catal. 210 (2002) 46–52.
[72] C.F. Hendriks, H.C.A. Vanbeek, P.M. Heertjes, Ind. Eng. Chem. Prod. Res. Dev. 16
(1977) 270–275.
[73] R. Criegee, Eur. J. Org. Chem. 560 (1948) 127–135.
[74] B.J. Yachnin, T. Sprules, M.B. McEvoy, P.C.K. Lau, A.M. Berghuis, J. Am. Chem.
Soc. 134 (2012) 7788–7795.
Acknowledgements
This work is financially supported by the National Natural Science
Foundation of China (21703101, 21303085), the Natural Science
Foundation of Jiangsu Province (BK20130901, BK20130930), the
Program to Cultivate Outstanding Young Key Teachers of Nanjing
Normal University (Qinglan Project), Postgraduate Research & Practice
Innovation Program of Jiangsu Province (KYCX17-1087) and the
Priority Academic Program Development of Jiangsu Higher Education
Institutions.
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.mcat.2018.07.022.
References
[1] S. Rahman, N. Enjamuri, R. Gomes, A. Bhaumik, D. Sen, J.K. Pandey, S. Mazumdar,
B. Chowdhury, Appl. Catal. A Gen. 505 (2015) 515–523.
[2] E.Y. Jeong, M.B. Ansari, S.E. Park, ACS Catal. 1 (2011) 855–863.
[3] R. Raja, J.M. Thomas, G. Sankar, Chem. Commun. 30 (1999) 525–526.
[4] M. Renz, B. Meunier, Eur. J. Org. Chem. 4 (1999) 737–750.
[5] Y. Imada, H. Iida, S. Murahashi, T. Naota, Angew. Chem. Int. Ed. 44 (2005)
1704–1706.
[6] S. Murahashi, Y. Oda, T. Naota, Tetrahedron Lett. 33 (1992) 7557–7560.
[7] R. Giannandrea, P. Mastrorilli, C.F. Nobile, G.P. Suranna, J. Mol. Catal. 94 (1994)
27–36.
[8] S. Ueno, K. Ebitani, A. Ookubo, K. Kaneda, Appl. Surf. Sci. 121 (1997) 366–371.
[9] T. Kawabata, Y. Ohishi, S. Itsuki, N. Fujisaki, T. Shishido, K. Takaki, Q. Zhang,
Y. Wang, K. Takehira, J. Mol. Catal. A Chem. 236 (2005) 99–106.
[10] H. Subramanian, E.G. Nettleton, S. Budhi, R.T. Koodali, J. Mol. Catal. A Chem. 330
(2010) 66–72.
[11] Y. Nabae, H. Rokubuichi, M. Mikuni, Y. Kuang, T. Hayakawa, M. Kakimoto, ACS
Catal. 3 (2013) 230–236.
[12] O. D’alessandro, H.J. Thomas, J.E. Sambeth, React. Kinet. Mech. Catal. 107 (2012)
295–309.
[13] M.F.M. Zwinkels, S.G. Jaras, P.G. Menon, T.A. Griffin, Catal. Rev. 35 (1993)
319–358.
[14] W. Zhan, Y. Guo, Y. Wang, X. Liu, Y. Guo, Y. Wang, Z. Zhang, G. Lu, J. Phys. Chem.
B 111 (2007) 12103–12110.
[15] D. Wang, D. Astruc, Chem. Rev. 144 (2014) 6949–6985.
[16] M. Shokouhimehr, K.Y. Shin, J.S. Lee, M.J. Hackett, S.W. Jun, M.H. Oh, J. Jang,
T. Hyeon, J. Mater. Chem. A 2 (2014) 7593–7599.
[17] M. Shokouhimehr, Catalysts 5 (2015) 534–560.
[18] M. Shokouhimehr, M.S. Asl, B. Mazinani, Res. Chem. Intermed. 44 (2018)
1617–1626.
[19] P. Zhang, H. Lu, Y. Zhou, L. Zhang, Z. Wu, S. Yang, H. Shi, Q. Zhu, Y. Chen, S. Dai,
Nat. Commun. 6 (2015) 1–10.
[20] D. Delimaris, T. Ioannides, Appl. Catal. B: Environ. 84 (2008) 303–312.
[21] P. Venkataswamy, K.N. Rao, D. Jampaiah, B.M. Reddy, Appl. Catal. B: Environ. 162
(2015) 122–132.
[22] K.A. Michalow-Mauke, Y. Lu, K. Kowalski, T. Graule, M. Nachtegaal, O. Kröcher,
D. Ferri, ACS Catal. 5 (2015) 5657–5672.
[23] P. Fornasiero, G.R. Rao, J. Kašpar, F. L’Erario, M. Graziani, J. Catal. 175 (1998)
269–279.
[24] X. Liu, J. Lu, K. Qian, W. Huang, M. Luo, J. Rare Earths 27 (2009) 418–424.
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