Improvement of catalytic activity in selective oxidation of styrene with H2O2 over spinel Mg-Cu ferrite hollow spheres in water

Article abstract of DOI:10.1016/j.materresbull.2014.04.038

Uniform spinel Mg-Cu ferrite hollow spheres were prepared using carbon spheres as templates. For comparison, solid Mg-Cu ferrite nanocrystals were also prepared by sol-gel auto-combustion, hydrothermal and coprecipitation methods. All the samples were characterized by Fourier transform infrared spectrophotometry (FT-IR), X-ray diffractometry (XRD), transmission electron microscopy (TEM) and N₂ physisorption. The samples were found to be efficient catalysts for oxidation of styrene using hydrogen peroxide as oxidant. Especially, in the case of Mg_0.5Cu_0.5Fe₂O ₄ hollow spheres, obvious improvement on catalytic activity was observed, and 21.2% of styrene conversion and 75.2% of selectivity for benzaldehyde were obtained at 80 °C for 6 h reaction in water. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in six consecutive runs.

Full text of DOI:10.1016/j.materresbull.2014.04.038

Accepted Manuscript
Title: Improvement of catalytic activity in selective oxidation
of styrene with H2O2 over spinel Mg-Cu ferrite hollow
Spheres in water
Author: Jinhui Tong Xiaodong Cai Haiyan Wang Qianping
Zhang
PII:
S0025-5408(14)00223-2
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.materresbull.2014.04.038
MRB 7410
To appear in:
MRB
Received date:
Revised date:
Accepted date:
31-10-2013
11-4-2014
18-4-2014
Please cite this article as: Jinhui Tong, Xiaodong Cai, Haiyan Wang, Qianping
Zhang, Improvement of catalytic activity in selective oxidation of styrene with H2O2
over spinel Mg-Cu ferrite hollow Spheres in water, Materials Research Bulletin
http://dx.doi.org/10.1016/j.materresbull.2014.04.038
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Improvement of catalytic activity in selective oxidation of styrene with H2O2 over spinel Mg-Cu ferrite
hollow Spheres in water
Jinhui Tong 1,2* , Xiaodong Cai 1,2, Haiyan Wang 1,2, Qianping Zhang 1,2
1 Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education, Lanzhou 730070, P. R. China;
2 Key Laboratory of Gansu Polymer Materials, College of Chemistry and Chemical Engineering, Northwest Normal University,
Lanzhou 730070, P. R. China;
Corresponding author. Jinhui Tong, Tel. /Fax: +86-931-7970359, E-mail address: HUjinhuitong@126.comUH
Graphical abstract
Uniform spinel Mg-Cu ferrite hollow spheres were prepared using carbon spheres as templates. Solid spinel Mg0.5Cu0.5Fe2O4
ferrite nanocrystals were also prepared by sol-gel auto-combustion, hydrothermal and coprecipitation methods for comparison.
The samples were found to be efficient catalysts for oxidation of styrene using hydrogen peroxide as oxidant. Especially, in the
case of Mg0.5Cu0.5Fe2O4 hollow spheres, obvious improvement on catalytic activity was observed and 21.2 % of styrene
o
conversion and 75.2 % of selectivity for benzaldehyde were obtained at 80 C for 6 h reaction in water. The catalyst can be
magnetically separated easily for reuse and no obvious loss of activity was observed when reused in six consecutive runs.
Highlights


Uniform spinel ferrite hollow spheres were prepared by a simple method.
The catalyst has been proved much more efficient for styrene oxidation than the reported
analogues.


The catalyst can be easily separated by external magnetic field and has exhibited excellent
reusability.
The catalytic system is environmentally friendly.
Abstract
Uniform spinel Mg-Cu ferrite hollow spheres were prepared using carbon spheres as templates. For comparison, solid Mg-Cu
ferrite nanocrystals were also prepared by sol-gel auto-combustion, hydrothermal and coprecipitation methods. All the samples
were characterized by Fourier transform infrared spectrophotometry (FT-IR), X-ray diffractometry (XRD), transmission electron
microscopy (TEM) and N2 physisorption. The samples were found to be efficient catalysts for oxidation of styrene using
hydrogen peroxide as oxidant. Especially, in the case of Mg0.5Cu0.5Fe2O4 hollow spheres, obvious improvement on catalytic
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activity was observed, and 21.2 % of styrene conversion and 75.2 % of selectivity for benzaldehyde were obtained at 80 oC for 6
h reaction in water. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed
when reused in six consecutive runs.
Key word: A. Magnetic materials; A. Oxides; B. Chemical synthesis; C. Electron diffraction; D. Catalytic properties
1. Introduction
Oxidation of styrene is of great interest due to the widely used products of benzaldehyde and styrene oxide.
Especially, benzaldehyde is a very valuable chemical that has widespread applications in perfumery, dyestuff and
agro chemical industries. It is the second most important aromatic molecule (after vanillin) used in the cosmetics
and flavor industries [1]. Many catalysts have been employed in styrene oxidation in recent years, such as Schiff
base and porphyrin complexes [2, 3]，zeolite-Y encapsulated V, Cu and Ni complexes [4-6], polymer anchored Cu
and Mn complexes [7], La, V, Cr, Mn and Ti modified molecular sieves [8-10] etc. Even so, continuous efforts
have been putting to develop more effective and environmentally benign catalysts which can be prepared simply
and recovered facilely.
Recently developed magnetically recyclable catalysts (MRCs) have proved to be a kind of promising catalysts
combining the advantages of high activity and easy recycling in heterogeneously catalytic processes [11-16]. In
particular, spinel ferrites have become more and more important in recent years due to both their unique properties
and broad range of applications in diverse areas such as magnetic recording and separation, ferrofluid, magnetic
resonance imaging (MRI), biomedicine, catalysts, gas sensors, high quality ceramics and superparamagnetic
materials [17-21]. A great advantage of using magnetic ferrite nanocrystals as catalysts in liquid phase reactions is
that the catalysts are not only thermally and chemically stable in the solution medium, but also easy to be separated
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by an external permanent magnet. Many examples for catalytic oxidation of styrene using spinel ferrites as
catalysts were reported, such as MgFe2O4 [22], SrFe2O4 [23], CaFe2O4 [24], nickel and zinc ferrites [25]. Ni-Gd
ferrites [26] and ferrites supported silver [27]. However, most of these reactions were carried out in organic
solvents with low efficiency. Moreover, due to the high superficial energy inherent to the nanoparticles and to the
magnetism of ferrites, these nanoparticles tend to coalesce and form large aggregates, which is a general
disadvantage for improving the catalytic activities.
It is well known that the properties and applications of ferrites commonly depend on their shapes, sizes and
structures [28]. Over the past decades, ferrites nano-materials with various morphologies including spheres, wires,
cubes, triangles, hollows and octahedrons have been successfully synthesized [29-34]. Among these, hollow
structures are of great interest due to their unique characteristics of low density, high surface-to-volume ratio, low
coefficient of thermal expansion and refractive index compared to their solid counterparts. These outstanding
properties render them promising for variety applications including lithium-ion batteries [35], anode materials [36]
catalysis [37] and drug/gene delivery [38]. Several catalytic systems based on hollow nano-materials have been
developed. Bai et al. [39] prepared Pd–Rh alloy hollow nanospheres immobilized on carbon nanotubes and tested
for electrocatalytic oxidation of formic acid. Song et al. [40] investigated the catalytic performance of silica
supported CuO for CO oxidation, and found that CuO supported on SiO2 hollow spheres exhibited much higher
catalytic activity than that supported on commercial SiO2. The authors referred that this may be attributed to the
fact that the unique hollow spherical texture should facilitate the formation of main active species and gas
diffusion in catalysts. Ravat et al [41]. synthesized palladium-supported boron-doped hollow carbon spheres as
highly efficient, recyclable catalysts for the solvent-free oxidation of alcohols.
The increasing demand for environment-conscious chemical processes has impelled many researchers to
investigate truly “green” technologies. In this view, hydrogen peroxide is an attractive oxidant as it is cheap, mild,
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and gives water as the only by-product [42]. In addition, compared with organic solvents, water should be the
cheapest and most environment-friendly medium.
In our previous work [43], Mg0.5Cu0.5Fe2O4 nanocrystal synthesized by sol-gel auto-combustion method was
proved to be highly active and easily recovered catalyst for the oxidation of styrene. In this paper, we prepared
spinel Mg0.5Cu0.5Fe2O4 ferrite hollow spheres using carbon spheres as templates. Solid spinel Mg0.5Cu0.5Fe2O4
ferrite nanocrystals were also prepared by sol-gel auto-combustion, hydrothermal and coprecipitation methods for
comparison. These materials were employed as catalysts for selective oxidation of styrene in water using hydrogen
peroxide as oxidant under mild reaction conditions. Key reaction parameters such as substrate/oxidant molar ratio,
reaction temperature, reaction time, amount of catalyst were optimized and the reusability of the catalyst was also
evaluated.
2. Experimental
2.1. Materials and equipments
All chemicals are of analytical grade and used without further purification. FT-IR spectra were measured on a
Nexus 870 FT-IR spectrophotometer. XRD patterns of the samples were collected using a PANalytical X’ Pert Pro
diffractometer with Cu Kα radiation. TEM micrographs were obtained using a Hitachi H-600 microscope. BET
surface area measurements were performed on a Micromeritics ASAP 2010 instrument at liquid nitrogen
temperature. The oxidation products were determined by an HP 6890/5973 GC/MS instrument and quantified by a
Shimadzu GC-2010 gas chromatograph.
2.2. Synthesis of the catalysts
2.2.1 Synthesis of carbon spheres
The carbon spheres were prepared via a hydrothermal method as described previously [44]. Typically, glucose
(10 g) was dissolved in water (80 mL) to form a clear solution. The solution was then sealed in a 100 mL
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teflon-lined autoclave and maintained at 180 oC for 12 h. The puce product was isolated by centrifugation and then
washed by water and ethanol several times in sequence. Finally, the product was oven-dried at 80 oC for 8 h.
2.2.2 Preparation of Mg0.5Cu0.5Fe2O4 ferrite hollow spheres
Figure 1 illustrates the main principle of generating Mg0.5Cu0.5Fe2O4 ferrite hollow spheres. Firstly, metal
ions were adsorbed from solution into carbon spheres surface layers. Next, carbon cores were removed by
calcination in air and the expected hollow spheres were obtained. The preparation procedures were described as
following: 0.4 g of as-prepared carbon spheres and stoichiometric amounts of Mg(NO3)2·6H2O，Cu(NO3)2·3H2O
and Fe(NO3)3·9H2O were dispersed in 30 mL distilled water and ultrasonicated for 25 minutes. Concentration of
metal cations in the resulted suspension is 0.1 mol·L-1. The suspension was aged for 12 h and then was
centrifugated to obtain the solid product. The product was then washed four times by water and dried copiously.
The dried sample was heated to 480 oC in air and maintained for one hour to give the final product. The
as-prepared sample is designated as MCFO-1.
2.2.3 Preparation of Mg0.5Cu0.5Fe2O4 ferrite nanocrystals
Solid Mg0.5Cu0.5Fe2O4 ferrite nano-powders were synthesized according to the reported sol-gel
auto-combustion route [45], hydrothermal [46] and coprecipitation [22] methods, and are designated as MCFO-2,
MCFO-3, MCFO-4 respectively.
2.3. Characterization of the samples
The XRD patterns of the as-synthesized samples confirm formation of crystalline spinel (Figure 2). The nine
peaks at 18.3, 30.2, 35.4, 38.1, 43.2, 53.1, 57.2, 62.7 and 74.1° can be ascribed to the reflection of (111), (220),
(311), (222), (400), (422), (511), (440) and (533) diffractions of MgFe2O4 (JCPDS NO. 88-1936) and CuFe2O4
(JCPDS NO. 77-0010) spinels. For samples MCFO-1 and MCFO-4, low intensity reflections ascribed to Fe2O3
were observed and this confirms existing of minor Fe2O3 in the two samples.
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Figure 3 shows the FT-IR spectra of the as-prepared samples. For all the samples, a strong band associated
with the Fe–O stretching vibration in ferrite around 580 cm−1 is presented. It confirms the presence of magnesium
ferrite or copper ferrite phase [47]. Two weak absorption bands around 3420 and 1630 cm−1 can be attributed to
stretching and bending vibrations of O–H in adsorbed water.
TEM images of the samples were shown in Figure 4. The as-prepared carbon spheres features uniform
spheres with diameters of 145 nm (Figure 4 a). The sample MCFO-1 consists of uniform hollow spheres with
about 65 nm diameters and 14 nm thick shells constructed by small nanoparticles. Most hollow spheres are intact
except for minor broken and connected ones (Figure 4b and c). The sample MCFO-2 features nanoparticles with
an irregular morphology and a broad particle size distribution ranging from 10-20 to 30-50 nm, with a high
percentage of small particles (25-30 nm). It is clear that the sample MCFO-2 have particle agglomeration forms
(Figure 4 d). The sample MCFO-3 shows particles with diameters about 14-50 nm, and most particles with
diameters about 21 nm (Figure 4 e). The morphology of the sample MCFO-4 exhibits a majority of irregular
particles with diameters about 25 nm and a minority of spherical analogues with diameters about 15 nm (Figure
4f).
Figure 5 presents the nitrogen adsorption-desorption isotherms and the corresponding pore size distribution
plots (insets) for the as-prepared samples. The isotherms of type IV with H3 hysteresis loops were obtained
according to the IUPAC classifications. This result indicates that all the samples have porous structure. The
amount adsorbed rises very steeply at high relative pressure (p/p0>0.8), which suggests the presence of large
mesopores or macropores [40]. The sample MCFO-1, hollow Mg0.5Cu0.5Fe2O4, has as high as 344.2 m2·g-1 of BET
specific surface area, which is much higher than those of 54.6, 51.8 and 54.3 m2·g-1 for the other three samples of
MCFO-2, MCFO-3 and MCFO-4 respectively (Table 1).
The BJH method was applied to the desorption isotherm to estimate the pore diameter. Except for MCFO-4
(Figure 5 d), the pore size distributions of the other three samples are very broad. As shown in the insets of Figure
5, there is one peak centered at 27.3 and 17.6 nm in MCFO-1 and MCFO-2 respectively (insets of Figure 5a, b).
Whereas, in the BJH pore size distribution of MCFO-3 (inset of Figure 5c), there are two peaks around 4.3 and
22.5 nm, respectively. This result indicates the structure of the sample is not so homogeneous, which is consistent
with the TEM result. The pore size distribution of MCFO-4 is relatively narrow, there is one peak around 12.4 nm
(inset of Figure 5d).
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2.4. Oxidation of styrene
The selective oxidation of styrene was carried out in a round bottom flask (25 mL) equipped with Teflon
coated magnetic stirrer and a reflux condenser. In a typical procedure, 3.0 mg of catalyst, 2.0 mL (17.4 mmol) of
styrene, 5.0 mL of water and 4.5 mL of hydrogen peroxide (30 %) were added successively into the flask. The
flask is then immersed in an oil bath at desired temperature for reaction. The products were identified by GC-MS
and quantified by GC. Hydrogen peroxide utilization efficiency is defined as molar ratio of H2O2 utilized to
produce benzaldehyde, phenylacetaldehyde and styrene oxide.
3. Results and discussion
3.1.Catalysis tests
The performances of the as-prepared samples on oxidation of styrene were evaluated in water using
hydroperoxide as oxidant. The blank reaction was also carried out under the same conditions for comparison. The
results were presented in Table 1. It can be seen that the catalysts can efficiently catalyze oxidation of styrene and
benzaldehyde was found to be the major product in all cases while almost no reaction took place in the absence of
catalyst (entry 5). As expected, the hollow spheres have shown the most prominent catalytic performance and the
highest conversion of 21.2% for styrene was obtained. Considering the differences in structures of the samples, it
is reasonable to believe that higher BET surface area and lower mass transfer resistance in inner surface is
responsible for higher activity of the hollow spheres. On the contrary, the formation of large agglomerates in the
case of solid Mg0.5Cu0.5Fe2O4 ferrite nanoparticles induces a reduction in BET surface area and an increase in mass
transfer resistance, which may account for its lower catalytic activities in relation to the hollow spheres. As a result,
the catalysts MCFO-2, MCFO-3 and MCFO-4 exhibited very close BET surface areas and thus obtained nearly
the same conversions (entry 2-4). For all the catalysts, more than 75 % of selectivity for the main product
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benzaldehyde has been obtained. In order to optimize the reaction conditions, the sample MCFO-1 was chosen as
catalyst to investigate the influences of styrene/H2O2, reaction temperature, reaction time and catalyst amount on
oxidation of styrene. The recyclable performance of the catalyst was also investigated.
3.2. Influence of solvent
Effects of various solvents including ethanol, acetonitrile, acetone and water on the oxidation of styrene were
investigated and the results were listed in Table 2. The styrene conversions obtained in different solvents are in the
order of CH3CN>CH3COCH3>C2H5OH>H2O. It is clear that aprotic solvents, especially acetonitrile, are more
favorable than protic ones for the conversion of styrene. The results are consistent with those reported by Guin and
Ma [22, 25]. The highest selectivity of 75.2 % for benzaldehyde was obtained in water although only 21.2 % of
styrene conversion was obtained. The catalyst MCFO-1 is more efficient than reported Mg0.4Fe2.6O4 and
Ni0.5Zn0.5Fe2O4 ferrite catalysts (entry 5 and 6), and much higher TON value was obtained under more
environmentally friendly reaction conditions. Moreover, taking into account it is the cheapest and most
environmentally friendly solvent, water was used as solvent in the following investigations.
3.3. Influence of styrene/H2O2 molar ratio
The reaction was carried out in the presence of different styrene/H2O2 molar ratios were investigated and the
results were listed in Table 3. It can be seen clearly that styrene conversion increased with increase of H2O2
concentration. As a result, when H2O2 concentration increased from 2:1 to 2:5, styrene conversion increased from
7.5 to 21.2 % while the hydrogen peroxide utilization efficiency decreased from 46.7 to 26.6 %. In respect of the
selectivity for benzaldehyde, with increase of H2O2 concentration, it increased firstly but then dropped, and the
highest value of 81.1 % was obtained with 2:3 molar ratio of styrene to H2O2. Considering both conversion of
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styrene and selectivity for benzaldehyde, 2:5 was selected as the optimum molar ratio of styrene to H2O2.
3.4 Effect of reaction temperature
Effect of temperature on the oxidation of styrene was investigated in the range of 50 to 90 °C (Table 4). It can
be found that high temperature is favorable for styrene conversion. As a result, when temperature was improved
from 50 to 90 °C, styrene conversion increased from 4.4 to 23.6 %. As for products distribution, with increase of
temperature, selectivity for benzaldehyde increased at first but then decreased slightly, the highest value of 75.2 %
was obtained at 80 °C. The selectivities for phenylacetaldehyde and styrene oxide showed a tendency of decrease
with the increase of temperature while total selectivity for other deeply oxidized by-products increased slightly.
3.5 Effect of reaction time
The time dependence of the oxidation of styrene was investigated at 80 oC in the range of 3-8 h (Table 5). It
was found that styrene conversion increased rapidly from 10.4 to 21.2 % with prolongation of reaction time from 3
to 6 h. Only marginal increment was observed, however, when reaction time was further prolonged from 6 to 8 h.
As for the products distribution, the selectivity for benzaldehyde hardly changed in the first 6 h and then dropped
to 70.1 % when reaction time was prolonged to 8 h. The selectivities for phenylacetaldehyde and styrene oxide
exhibited a tendency of decline while that for other deeply oxidized by-products showed an opposite direction with
prolongation of the reaction time. In pursuit of higher selectivity for main product benzaldehyde, 6 h was
considered as optimum reaction time.
3.6 The effect of catalyst amount
Table 6 shows the results of styrene oxidation with different amount of the catalyst. As can be seen, styrene
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conversion increased from 13.2 to 21.2% when the amount of catalyst increased from 2.0 to 3.0 mg. When amount
of the catalyst further increased from 3.0 to 7.0 mg, however, styrene conversion decreased to 14.7 % possibly due
to adsorption or chemisorptions of two reactants on separate catalyst particles, thereby reducing the chance to
interact. Similar observations were noted by Sharma, S and Pardeshi, S.K. [7, 23]. When the catalyst amount
increased from 2.0 to 7.0 mg, the selectivity for benzaldehyde increased from 74.3 to 79.4 % while that for
phenylacetaldehyde along with styrene oxide changed slightly. Based on above results, 3.0 mg is considered as
optimum catalyst amount.
3.7 Reuse of the catalyst.
After the reaction, the catalyst was magnetically fixed at the side wall of the reactor (Figure 6), the reaction
mixture was decanted, the reactor was recharged with fresh substrate and then subjected to the second run under
the same conditions. The results of six runs were shown in Figure 6. The selectivity for benzaldehyde changed
slightly after six runs, however, the conversion of styrene decreased from 20.8 to 16.6 %. The decrease in the
activity could be mainly attributed to unavoidable loss of the catalyst during the process of collection. The results
confirm that the hollow spinel nanocrystalline has good stability and recyclable applicability for the oxidation of
styrene under our experimental conditions.
4. Conclusions
Spinel Mg0.5Cu0.5Fe2O4 hollow spheres and solid nanocrystals were prepared by various methods. The
samples are efficient catalysts for oxidation of styrene using hydroperoxide as oxidant and water as green media
to produce major product of benzaldehyde. Especially, unique hollow structure endows the sample of spinel
Mg0.5Cu0.5Fe2O4 ferrite much higher BET surface area and catalytic activity than the solid ones prepared by the
sol-gel auto-combustion route, hydrothermal and coprecipitation methods. The hollow spheres can be
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magnetically separated easily and exhibited excellent reusability. When it was reused six times, only slight loss
of the activity was observed and the products distribution was practically unchanged. As another example, this
work further confirms that hollow structure is promising for improving catalytic activities of the catalysts.
Acknowledgements
The authors are grateful to the National Natural Science Foundation of China (51302222, 21174114)，
Gansu Provincial Natural Science Foundation (1308RJYA017) and Program for Changjiang Scholars and
Innovative Research Team in University (IRT1177) for financial support.
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Page 13 of 20

Figure 1. Schematic illustration of the formation of spinel Mg-Cu ferrite hollow nanospheres. (A) Carbon spheres (B) Ferrite
hollow spheres.
Figure 2. The XRD patterns of the samples
Figure 3. The FT-IR spectra of the samples
Figure 4. The TEM images of a) carbon spheres; b,c) MCFO-1; d) MCFO-2; e) MCFO-3; f) MCFO-4.
Figure 5. The nitrogen adsorption–desorption isotherms for the samples: a) MCFO-1; b) MCFO-2; c) MCFO-3; d) MCFO-4.
Insets show the corresponding BJH pore size distribution curves based on desorption branch.
Figure 6. Reuse of the catalyst. Reaction conditions: styrene 17.4 mmol; MCFO-1 3mg; H2O 5.0 mL; temperature 80 oC;
reaction time 6 h; molar ratio of styrene:H2O2 2:5.
Table
Table 1. Oxidation of styrene with different catalysts a.
Total
Selectivity (%) b
pore
Conversion
(%)
BET surface
area (m2·g-1)
Entry
Catalyst
TON c
Others
CH
3.5
volume
BzA
PhAA
SO
(cm³/g)
0.43
0.16
0.17
0.16
—
PPO
8.2
6.5
7.8
6.1
—
HDPO
1.9
1
2
3
4
5
344.2
54.6
51.8
54.3
—
21.2
13.4
15.5
14.2
—
271
171
198
182
—
75.2
78.1
76.5
79.6
—
4.7
4.8
4.5
4.0
—
6.5
6.1
6.1
5.8
—
MCFO-1
MCFO-2
MCFO-3
MCFO-4
Blank
2.2
2.3
3.5
1.6
1.6
2.9
—
—
a Reaction conditions: styrene 17.4 mmol, catalyst 3.0 mg, H2O 5.0 mL, molar ratio of styrene:H2O2 2:5, reaction temperature 80
b
oC, reaction time 6 h.
BzA=Benzaldehyde, PhAA=Phenylacetaldehyde, SO=Styrene oxide, PPO=1-phenylpropan-ol,
CH=chalcone, HDPO=2-hydroxy-1,3-diphenylpropan-1-one. c TON=moles of substrate converted per mol of catalyst.
Table 2. The effect of styrene oxidation with different solvents a.
Selectivity (%) b
Entry
Solvent
Water
Conversion (%) TON c
Others
BzA PhAA
SO
6.5
PPO CH HDPO
1
21.2
271
75.2
4.7
8.2
3.5
1.9
14
Page 14 of 20

2
3
4
5
6
Acetonitrile
Acetone
55.6
45.5
36.4
40.6
30.7
711
582
465
4
63.8
68.9
62.1
66.7
52.1
1.7
7.0
5.8
3.9
13.9
9.5
11.9 4.9
9.2 1.2
12.2 6.0
3.6
4.1
3.3
Ethanol
10.6
5.9
Acetoned
Acetonee
—
7
—
a Reaction conditions: styrene 17.4 mmol; MCFO-1 3.0 mg; solvent 5.0 mL; molar ratio of styrene:H2O2 2:5; temperature 80 oC;
reaction time 6 h. b BzA=Benzaldehyde, PhAA=Phenylacetaldehyde, SO= Styrene oxide, PPO=1-phenylpropan-ol, CH=chalcone,
HDPO=2-hydroxy-1,3-diphenylpropan-1-one. c TON=moles of substrate converted per mol of catalyst. d Results from Ref.[22].
e
Reaction conditions: styrene 10 mmol, acetone 10 mL, Mg0.4Fe2.6O4 100 mg, molar ratio of styrene:H2O2 1:1, 50 oC, 24 h.
Results from Ref. [25]. Reaction conditions: styrene 10 mmol, acetone 10 mL, Ni0.5Zn0.5Fe2O4 100 mg, molar ratio of
styrene:H2O2 1:1, 60 oC, 12 h, N2 atmosphere.
Table 3. The effect of styrene oxidation with different styrene/H2O2 molar ratioa.
Selectivity (%) b
Entry Styrene:H2O2 Conversion (%) TON c
Others
H2O2 efficiency(%) d
BzA PhAA SO
PPO CH HDPO
1
2
3
4
5
2:1
1:1
2:3
1:2
2:5
7.5
96
73.6
75.1
81.1
77.8
75.2
5.5
5.6
4.1
5.2
4.7
9.8
7.5
5.5
6.2
6.5
6.3
6.9
5.4
6.1
8.2
2.4
3.1
2.6
2.5
3.5
2.4
1.9
1.1
1.5
1.9
46.7
38.8
30.2
24.9
26.6
12.3
13.4
15.4
21.2
157
171
197
271
a
Reaction conditions: styrene 17.4 mmol; MCFO-1 3.0 mg; H2O 5.0 mL; temperature 80 oC; reaction time 6 h.b
BzA=Benzaldehyde,
PhAA=Phenylacetaldehyde,
SO=Styrene
oxide,
PPO=1-phenylpropan-ol,
CH=chalcone,
c
d
HDPO=2-hydroxy-1,3-diphenylpropan-1-one. TON=moles of substrate converted per mol of catalyst. Hydrogen peroxide
utilization efficiency, defined as molar ratio of H2O2 utilized to produce benzaldehyde, phenylacetaldehyde and styrene oxide.
Table 4. The effect of styrene oxidation under different reaction temperature a.
Selectivity (%) b
Entry Temperature (°C) Conversion (%) TON c
Others
BzA PhAA
SO
PPO CH HDPO
1
50
4.4
56
64.8
8.7
13.7
6.9
4.7
1.2
15
Page 15 of 20

2
3
4
5
60
70
80
90
6.2
79
66.7
72.3
75.2
72.7
7.9
7.6
4.7
4.3
11.7
9.4
6.5
6.4
6.8
7.6
8.2
8.9
4.5
1.3
3.5
5.0
2.3
1.6
1.9
2.6
14.2
21.2
23.6
181
271
301
a Reaction conditions: styrene 17.4 mmol; MCFO-1 3.0 mg; H2O 5.0 mL; reaction time 6 h. molar ratio of styrene:H2O2 2:5.
b BzA=Benzaldehyde, PhAA=Phenylacetaldehyde, SO= Styrene oxide, PPO=1-phenylpropan-ol, CH=chalcone,
HDPO=2-hydroxy-1,3-diphenylpropan-1-one. c TON=moles of substrate converted per mol of catalyst.
Table 5. The effect of styrene oxidation with different reaction time a.
Selectivity (%) b
Entry time (h) Conversion (%) TON c
Others
BzA PhAA SO
PPO CH HDPO
1
2
3
4
5
6
3
4
5
6
7
8
10.4
14.8
17.2
21.2
22.4
23.1
133
189
219
271
286
293
75.3
75.1
75.7
75.2
74.2
70.1
5.5
5.0
5.1
4.7
4.0
4.5
8.2
6.4
6.5
6.5
5.7
6.3
7.3
6.9
8.3
8.2
8.7
9.3
2.0
3.9
3.2
3.5
5.3
6.6
1.7
2.7
1.2
1.9
2.1
3.1
a Reaction conditions: styrene 17.4 mmol; MCFO-1 3.0 mg; H2O 5.0 mL; temperature 80 oC ; molar ratio of styrene:H2O2 2:5.
b BzA=Benzaldehyde, PhAA=Phenylacetaldehyde, SO=Styrene oxide, PPO=1-phenylpropan-ol, CH=chalcone,
HDPO=2-hydroxy-1,3-diphenylpropan-1-one. c TON=moles of substrate converted per mol of catalyst.
Table 6. The effect of styrene oxidation with different catalyst amountsa.
16
Page 16 of 20

Selectivity (%) b
Entry Catalyst amount (mg) Conversion (%) TON c
Others
PPO CH HDPO
BzA PhAA SO
1
2
3
4
2.0
3.0
5.0
7.0
13.2
21.2
18.9
14.7
253
271
145
80
74.3
75.2
77.5
79.4
5.3
4.7
2.8
4.9
6.5
6.5
5.7
6.1
7.8
8.2
8.0
6.6
3.7
3.5
3.4
1.8
2.3
1.9
2.4
1.1
a Reaction conditions: styrene 17.4 mmol; H2O 5.0 mL; temperature 80 oC; reaction time 6 h; molar ratio of styrene:H2O2 2:5.
b BzA=Benzaldehyde, PhAA=Phenylacetaldehyde, SO= Styrene oxide, PPO=1-phenylpropan-ol, CH=chalcone,
HDPO=2-hydroxy-1,3-diphenylpropan-1-one. c TON=moles of substrate converted per mol of catalyst.
Figure
Figure 1
O
OH
OH
O
O
HO
OH
OH
+
Mg2+,Cu2
HO
Calcined
O
OH
OH
O
HO
Fe3+
O
O
OH
HO
OH
HO
O
Carbon nanospheres
Cu-Mg ferrites hollow nanospheres
Figure 2
Fe2O3
*
*
*
MCFO-1
MCFO-2
MCFO-3
*
MCFO-4
20
40
60
80
2 (degree)
17
Page 17 of 20

Figure 3
MCFO-1
MCFO-2
MCFO-2
MCFO-4
580cm-1
4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber(cm )
Figure 4
18
Page 18 of 20

Figure 5
Figure 6
120
100
80
60
40
20
0
Conversion
Selectivity of BzA
Selectivity of PhAA
Selectivity of SO
1
2
3
4
5
6
Reaction runs
19
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20
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