Molybdenum oxide supported on hydroxyapatite-encapsulated γ-Fe 2O3: A novel magnetically recyclable catalyst for olefin epoxidation

Article abstract of DOI:10.1016/S1872-2067(10)60226-4

Hydroxyapatite-encapsulated magnetic γ-Fe₂O₃ (HAP-γ-Fe₂O₃) was synthesized and used as catalyst support. Molybdenum oxide nanoparticles were supported on HAP-γ-Fe ₂O₃ by incipient wetness impregnation (MoO _x/HAP-γ-Fe₂O₃). High-resolution transmission electron microscopy characterization demonstrated the formation of γ-Fe₂O₃ nanocrystallites with a mean diameter of 1-3 nm within the HAP matrix. The molybdenum oxide dispersed on the surface of HAP-γ-Fe₂O₃ showed good catalytic activities for the epoxidation of various olefins with tert-butyl hydroperoxide as oxidant. The magnetism of MoO_x/HAP-γ-Fe₂O₃ provided a convenient route for the separation of the catalyst from the reaction mixture by a magnet. The catalyst was recycled at least five times without appreciable loss of catalytic activity.

Full text of DOI:10.1016/S1872-2067(10)60226-4

CHINESE JOURNAL OF CATALYSIS
Volume 32, Issue 7, 2011
Online English edition of the Chinese language journal
Cite this article as: Chin. J. Catal., 2011, 32: 1166–1172.
RESEARCH PAPER
Molybdenum Oxide Supported on Hydroxyapatite-
Encapsulated Ƣ-Fe2O3: A Novel Magnetically Recyclable
Catalyst for Olefin Epoxidation
YUAN Chengyuan1,2, ZHANG Yan1, CHEN Jing1,*
1State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences,
Lanzhou 730000, Gansu, China
2Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Abstract: Hydroxyapatite-encapsulated magnetic Ȗ-Fe2O3 (HAP-Ȗ-Fe2O3) was synthesized and used as catalyst support. Molybdenum
oxide nanoparticles were supported on HAP-Ȗ-Fe2O3 by incipient wetness impregnation (MoOx/HAP-Ȗ-Fe2O3). High-resolution transmis-
sion electron microscopy characterization demonstrated the formation of Ȗ-Fe2O3 nanocrystallites with a mean diameter of 1–3 nm within
the HAP matrix. The molybdenum oxide dispersed on the surface of HAP-Ȗ-Fe2O3 showed good catalytic activities for the epoxidation of
various olefins with tert-butyl hydroperoxide as oxidant. The magnetism of MoOx/HAP-Ȗ-Fe2O3 provided a convenient route for the
separation of the catalyst from the reaction mixture by a magnet. The catalyst was recycled at least five times without appreciable loss of
catalytic activity.
Key words: hydroxyapatite; epoxidation; tert-butyl hydroperoxide; supported molybdenum catalyst; magnetic separation
Olefin epoxidation is an important reaction because epox-
ides are very useful intermediates in the organic synthesis of
fine chemicals [1]. Molybdenum (VI) solid catalysts are widely
used for the epoxidation of olefins [2–8]. However, the cata-
lysts can only be recycled by tedious procedures using filtra-
tion and centrifugation, which inevitably leads to the loss of
catalyst in the separation processes. Recently, magnetic
nanoparticles of iron oxides have received growing attention
due to their unique properties and potential application in
various fields, such as magnetic resonance imaging (MRI)
contrast agents, magnetically assisted drug delivery, hyper-
thermia, magnetic separation of biomolecules, and isolation
and recycling of catalysts [9–12]. Magnetic separation is a
convenient method for separating magnetic solid catalysts for
recycling. However, bare nanoparticles of iron oxides tend to
aggregate into large clusters and lose their single-domain and
magnetic nanostructures. Therefore, a suitable passive material
such as a polymer, carbon, or silica has to be coated on the
surface of the iron oxide nanoparticles to prevent aggregation
and improve their chemical stability [13–15].
Hydroxyapatites (HAPs) with the molecular formula of
Ca10(PO4)6(OH)2 are of considerable interest for their structural
stability, ionic substitution, and adsorption capacity [16]. The
hexagonal apatite structure is composed of Ca2+ sites sur-
3–
rounded by tetrahedral PO4 units. OH– ions occupy columns
parallel to the hexagonal structure. HAP has these unique ad-
vantages as a catalyst support: (1) a high ion-exchange ability
and adsorption capacity, which are good for immobilizing
active species; (2) a nonporous structure to avoid the problem
of mass transfer limitation; and (3) weak acid-base properties
that reduce side reactions induced by the support itself.
HAP-encapsulated magnetic nanocrystallites as the catalyst
support for olefin oxidation, alcohol oxidation, and dehaloge-
nation reactions have been reported [17–19].
In this paper, we report the fabrication of molybdenum oxide
nanoparticles dispersed on a hydroxyapatite shell that was
coated on magnetic iron oxides particles. This was a highly
active and magnetically recyclable catalyst for the epoxidation
of alkene with tert-butyl hydroperoxide (TBHP).
Received 21 February 2011. Accepted 18 March 2011.
*Corresponding author. Tel: +86-931-4968068; Email: chenj@lzb.ac.cn
This work was supported by the National Science Fund for Distinguished Young Scholars of China (20625308).
Copyright © 2011, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(10)60226-4

YUAN Chengyuan et al. / Chinese Journal of Catalysis, 2011, 32: 1166–1172
FeCl2
+
FeCl3
(NH4)6Mo7O24
Calcination
1) CaP
2)
NH4OH
Ȗ-Fe2O3
Fe O
Ȗ-Fe2O3
3
4
MoOx
HAP
HAP
HAP-Ȗ-Fe2O3
MoOx/HAP-Ȗ-Fe2O3
Scheme 1. Synthesis of MoOx/HAP-Ȗ-Fe2O3.
1 Experimental
resolution TEM (HRTEM) micrographs were obtained with a
JEM-2010 electron microscope. BET surface area measure-
ments were performed on a Micromeritics ASAP 2010 in-
strument at liquid nitrogen temperature. Magnetic properties
were characterized by a VSM by Lakeshore 7304. The mag-
netism of HAP-Ȗ-Fe2O3 was investigated using a supercon-
ducting quantum interface device magnetometer.
1.1 Catalyst preparation
The synthesis procedure is represented in Scheme 1.
HAP-encapsulated Ȗ-Fe2O3 (HAP-Ȗ-Fe2O3) was prepared ac-
cording to a previously reported method [18]. The detailed
procedure was as follows. FeCl2·4H2O (1.85 mmol) and
FeCl3·6H2O (3.7 mmol) were dissolved in deionized water (30
ml) under an Ar atmosphere at room temperature. The resulting
solution was added to a 25 wt% NH4OH solution (10 ml) under
vigorous mechanical stirring (300 r/min). A black precipitate of
Fe3O4 was produced. In order to get small and uniform Fe3O4
particles, the drop rate of NH4OH was controlled precisely by a
constant dropper. The drop time was 10 min. After 15 min, 100
ml of Ca(NO3)2·4H2O (33.7 mmol, 0.5 mol/L) and (NH4)2HPO4
(20 mmol, 3.0 mol/L) solutions with their pH adjusted to 11
were added dropwise to the precipitate over 30 min under
mechanical stirring. The resulting milky solution was heated to
90 oC. After 2 h, the mixture was cooled to room temperature
and aged overnight. The dark brown precipitate formed was
filtered, washed repeatedly with deionized water until the water
was neutral, and then air dried under vacuum at room tem-
perature. The synthesized sample was calcined at 300 oC for 3
h. The color of the powder changed from deep black to red-
dish-brown after calcination, indicating the transformation of
the magnetite (Fe3O4) cores to hematite (Fe2O3).
1.3 Catalytic tests
The activity of the MoOx/HAP-Ȗ-Fe2O3 catalyst was tested
with the epoxidation of olefin. In a typical experiment, a mix-
ture of substrate (5 mmol), TBHP (70 wt%, 5 mmol), and 25
mg of MoOx/HAP-Ȗ-Fe2O3 in 6 ml chloroform was introduced
into a 50 ml glass reactor with vigorous stirring. The reaction
was maintained for 8 h to get a high conversion. Qualitative
analysis was conducted with a HP 6890/5973 GCMS with
Chemstation and the NIST mass spectral database. Quantita-
tive analysis was conducted with an Agilent 6820 GC equipped
with an FID.
The reusability of the catalyst was tested as follows. After
the reaction, a bar magnet was used to keep the MoOx/HAP-
Ȗ-Fe2O3 catalyst on the side wall of the reactor while the reac-
tion solution was removed. The catalyst was washed repeatedly
with chloroform. Alkene, chloroform, and TBHP were then
added to start the next run.
The MoOx/HAP-Ȗ-Fe2O3 catalyst was prepared by incipient
wetness impregnation. The required amount of (NH4)6Mo7O24·
4H2O was dissolved in distilled water. HAP-Ȗ-Fe2O3 (1.0 g)
was added into the stirred solution at 80 oC, and the water was
completely evaporated. The MoOx/HAP-Ȗ-Fe2O3 catalyst was
obtained after the solid material was calcined at 550 oC for 3 h
in air.
2 Results and discussion
2.1 Characterization results
2.1.1 Textural, chemical, and physical properties
Figure 1 shows the nitrogen adsorption-desorption isotherms
of the samples. All samples showed a Type IV isotherm with a
Type H2 hysteresis loop, indicating the presence of
well-developed mesoporosity in all the samples.
1.2 Catalyst characterization
X-ray diffraction (XRD) was carried out on a PANalytical
X’pert Pro diffractometer. X-ray photoelectron spectroscopy
(XPS) was performed on a VG ESCALAB 210 spectrometer.
All binding energies were calibrated using the C 2p peak at
285.0 eV. Transmission electron microscopy (TEM) images
were obtained on a Hitachi H-600 electron microscope. High-
Table 1 summarizes the physicochemical parameters of the
catalysts. As compared with HAP-Ȗ-Fe2O3, the BET surface
area and specific pore volume of MoOx/HAP-Ȗ-Fe2O3 were
obviously smaller while the pore diameter was increased. This
was because molybdenum oxide particles have blocked some
of the pores when they were deposited, which suggested that

YUAN Chengyuan et al. / Chinese Journal of Catalysis, 2011, 32: 1166–1172
MoO3
(1)
(2)
Spent 20 wt% MoOx/HAP-J-Fe2O3
30 wt% MoOx/HAP-J-Fe2O3
20 wt% MoOx/HAP-J-Fe2O3
(3)
(4)
(5)
10 wt% MoOx/HAP-J-Fe2O3
0.0
0.2
0.4
0.6
0.8
1.0
5 wt% MoOx/HAP-J-Fe2O3
HAP-J-Fe2O3
Relative pressure (p/p0)
Fig. 1. N2 adsorption-desorption isotherms of HAP-Ȗ-Fe2O3 (1), 5 wt%
MoOx/HAP-Ȗ-Fe2O3 (2), 10 wt% MoOx/HAP-Ȗ-Fe2O3 (3), 20 wt%
MoOx/HAP-Ȗ-Fe2O3 (4), and 30 wt% MoOx/HAP-Ȗ-Fe2O3 (5).
HAP
Table 1 Textural parameters of the catalyst samples
10
20
30
40
50
60
2T/(o )
BET surface Pore volume Pore diameter
Sample
area (m2/g)
(cm3/g)
0.43
(nm)
14.3
26.2
28.7
29.9
34.3
Fig. 2. XRD patterns of HAP, HAP-Ȗ-Fe2O3, MoOx/HAP-Ȗ-Fe2O3, and
HAP-Ȗ-Fe2O3
119
59
48
40
16
MoO3.
5 wt% MoOx/HAP-Ȗ-Fe2O3
10 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
30 wt% MoOx/HAP-Ȗ-Fe2O3
0.39
noting that two new diffraction peaks at 2ș = 18.5o and 28.7o
appeared with all the MoOx/HAP-Ȗ-Fe2O3 catalysts, which
were not seen with HAP-Ȗ-Fe2O3 and MoO3. The appearance of
these two new peaks indicated that molybdenum oxide phases
that were different from MoO3 were formed on the surface of
the MoOx/HAP-Ȗ-Fe2O3 catalysts. As compared with the fresh
catalyst, there was no change in the characteristic diffraction
peaks of the spent MoOx/HAP-Ȗ-Fe2O3 catalyst after six recy-
cles, indicating the high stability of the catalyst.
0.36
0.29
0.14
molybdenum oxide can be easily fixed on the surface of
HAP-Ȗ-Fe2O3 by conventional incipient wetness impregnation.
It should be noted that the changes in BET surface area, spe-
cific pore volume, and pore diameter increased abruptly when
the Mo loading exceeded 20 wt%, which was attributed to the
agglomeration of molybdenum oxide.
2.1.3 XPS
2.1.2 XRD
XPS binding energies and intensities of the surface elements
provide information on the chemical states and relative quan-
tities of the surface compounds. Figure 3 shows the Mo 3d
spectra of the MoOx/HAP-Ȗ-Fe2O3 catalysts as a function of
molybdenum content. Assignment of the Mo on the supports
was possible using the spectra of pure MoO3 as reference. The
Mo binding energies in MoO3 (Eb(Mo 3d5/2) = 233.1 eV, Eb(Mo
3d3/2) = 236.2 eV) were similar to that of the MoOx/HAP-
Ȗ-Fe2O3 catalysts. As compared with pure MoO3, the Mo
binding energies of all the MoOx/HAP-Ȗ-Fe2O3 catalysts with
different Mo loadings were shifted to lower binding energies,
indicating that there was electron transfer from the support to
the Mo species on the surface of the catalysts. This result also
confirmed that there existed chemical interactions between Mo
and the HAP-Ȗ-Fe2O3 support, which was consistent with the
XRD result. The energy of the Mo 3d5/2 signal from the MoOx/
The powder XRD patterns of HAP, HAP-Ȗ-Fe2O3,
Mo/HAP-Ȗ-Fe2O3, and MoO3 samples are shown in Fig. 2.
Seven well-resolved diffraction peaks of pure HAP (2ș = 25.9o,
31.8o, 32.9o, 34.1o, 39.8o, 46.7o, and 49.5o) were clearly ob-
served with HAP-Ȗ-Fe2O3 and all the MoOx/HAP-Ȗ-Fe2O3
catalysts, confirming the formation of the HAP phase. The
diffraction peaks of HAP-Ȗ-Fe2O3 were weak, which was
probably due to the small size of the particles [18]. As com-
pared with pure Ȗ-Fe2O3 [20,21], HAP-Ȗ-Fe2O3 exhibited clear
diffraction peaks at 2ș = 30.2o, 35.7o, and 43.6o, which were
assigned to the (220), (311), and (400) reflections of Ȗ-Fe2O3,
respectively. Other iron oxide phases such as Į-Fe2O3 (2ș =
24.1o, 33.1o, 35.6o, 40.8o, 54.1o, and 63.9o) were not detected.
The diffraction line of MoO3 was absent in the diffractograms
of the catalysts with Mo content lower than 30 wt%. It is worth

YUAN Chengyuan et al. / Chinese Journal of Catalysis, 2011, 32: 1166–1172
Ȗ-Fe2O3 nanocrystallites were uniformly distributed within the
host HAP matrix with diameters of 1ꢀ3 nm, which were
smaller than those in the results reported by Mori et al. [18].
The micrograph of 20 wt% MoOx/HAP-Ȗ-Fe2O3 is shown in
Fig. 4(b). Dark amorphous nano-particles of molybdenum
oxide with a size distribution of 20ꢀ50 nm existed on the sur-
face of HAP, which was consistent with the XRD result. The
diffraction pattern (the inset in Fig. 4(a)) exhibited atomic
lattice fringes corresponding to the (220), (311), and (400)
planes of Ȗ-Fe2O3, which was in good agreement with those
obtained from XRD described earlier [23].
30 wt% MoOx/HAP-J-Fe2O3
20 wt% MoOx/HAP-J-Fe2O3
10 wt% MoOx/HAP-J-Fe2O3
5 wt% MoOx/HAP-J-Fe2O3
MoO3
2.1.5 Magnetic hysteresis loop
Mo 3d5/2
Mo 3d3/2
224 226 228 230 232 234 236 238 240
Binding energy (eV)
Figure 5 shows the magnetic hysteresis loop of HAP-
Ȗ-Fe2O3. As shown in Fig. 5, the isothermal magnetization
curve of HAP-Ȗ-Fe2O3 displayed a rapid increase with in-
creasing applied magnetic field, with a saturation magnetiza-
tion (Ms) value of 7 emu/g. Taken into consideration the
Ȗ-Fe2O3 content in the sample (12 wt%), the Ms value of 58
emu/g for Ȗ-Fe2O3 encapsulated in the mesoporous tita-
nium-silica shell was smaller than the theoretical Ms value of
76 emu/g for bulk Ȗ-Fe2O3 [24], which can be explained by the
size effect degradation of the magnetic properties of iron oxide
nanocrystallites [25].
Fig. 3. XPS spectra of the Mo 3d region for different MoOx/HAP-
Ȗ-Fe2O3 catalysts and MoO3.
HAP-Ȗ-Fe2O3 catalyst was 232.5 eV, which agreed with that of
MoO42ꢀ reported previously [22]. Therefore, the main Mo peak
of this catalyst was explained by the presence of a mixture of
MoO3 and MoO42ꢀ . In addition, as seen from Fig. 3, the XPS
signal intensity of Mo 3d increased with Mo content.
2.1.4 HRTEM
2.2 Catalytic test
Figure 4 shows the HRTEM images. Figure 4(a) showed a
clear image that Ȗ-Fe2O3 was coated with a layer HAP. The
The catalytic activities of the various catalysts for the ep-
oxidation of cyclohexene under different reaction conditions
are shown in Table 2. In the absence of a catalyst (entry 1),
cyclohexene gave only 27.1% conversion and no epoxide was
found. Since the carrier of HAP-Ȗ-Fe2O3 gave a similar result to
that with no catalyst, the carrier was not active (entry 2).
MoOx/HAP-Ȗ-Fe2O3 gave very high conversion and epoxide
selectivity, which indicated that molybdenum oxide was the
active component and confirmed the existence of molybdenum
oxide on the surface of MoOx/HAP-Ȗ-Fe2O3. The catalytic
performances over various molybdenum-containing catalysts
(220)
(400)
(311)
(a)
Ȗ-Fe2O3
8
6
4
2
0
(b)
-12000 -8000 -4000
0
4000 8000 12000
-2
-4
-6
-8
100 nm
Field (Oe)
Fig. 5. Magnetic hysteresis loop of HAP-Ȗ-Fe2O3.
Fig. 4. HRTEM images of HAP-Ȗ-Fe2O3 (a) and 20 wt% MoOx/HAP-
Ȗ-Fe2O3 (b).

YUAN Chengyuan et al. / Chinese Journal of Catalysis, 2011, 32: 1166–1172
Table 2 Epoxidation of cyclohexene under various reaction conditions
Entry
Catalyst
Solvent
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
C6H14
Temperature (oC)
Conversion (%)
27.1
Epoxide selectivity (%)
1
2
blank
70
70
70
70
70
70
70
70
70
30
50
—
HAP-Ȗ-Fe2O3
33.9
—
3
5 wt%MoOx/HAP-Ȗ-Fe2O3
10 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
30 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
20 wt% MoOx/HAP-Ȗ-Fe2O3
46.1
51.8
89.0
98.7
95.6
43.4
—
4
68.9
5
90.8
6
93.4
7
25.7
8
CH3CN
CH3OH
CHCl3
CHCl3
no reaction
no reaction
10.3
9
—
10
11
11.2
83.7
59.4
Reaction conditions: cyclohexene 5 mmol, TBHP 5 mmol, catalyst 25 mg, solvent 6 ml, 8 h. Conversion and selectivity for olefins were determined by GC
using an internal standard (decane) technique
with different molybdenum content were tested (entries 3–6).
When the molybdenum content increased from 5 wt% to 20
wt%, the cyclohexene conversion and epoxide selectivity in-
creased gradually. However, when the molybdenum content
was > 20 wt%, the epoxide selectivity decreased, which was
probably due to the increase of side reactions caused by the
agglomeration of molybdenum oxide. 20 wt% MoOx/HAP-
Ȗ-Fe2O3 showed 90.8% cyclohexene conversion and 98.7%
epoxide selectivity, which were higher than those reported
previously for this reaction using Mo-based catalysts [2–6].
Taking into account the cyclohexene conversion as well as the
epoxide selectivity, 20 wt% MoOx/HAP-Ȗ-Fe2O3 was the best
for the epoxidation of cyclohexene.
contents in it were negligible (Mo < 5 ȝg/L, Fe < 3 ȝg/L).
To extend the scope of the catalyst, the MoOx/HAP-Ȗ-Fe2O3
catalyst was applied for the oxidation of a wide range of cyclic
and linear alkenes with TBHP under the optimized conditions.
As shown in Table 3, all of the olefins were converted into the
magnetic
separation
Various solvents were examined to find the appropriate
conditions for the reaction (entries 5, 7–9). The performance of
this catalyst was significantly solvent dependent, with CHCl3
giving the best result.
reuse
O
The temperature dependence of cyclohexene epoxidation
was also investigated (entries 5, 10, and 11). Cyclohexene
conversion and epoxide selectivity strongly depended on the
reaction temperature, which was consistent with the results in a
previous report [26]. When the reaction was performed at 30
oC, the conversion of cyclohexene and selectivity for epoxide
were very low. As the temperature increased, both the conver-
sion of cyclohexene and selectivity for epoxide increased. A
cyclohexene conversion of 90.8% and epoxide selectivity of
98.7% were obtained at 70 oC.
Fig. 6. Magnetic separation and recycling of the MoOx/HAP-Ȗ-Fe2O3
catalyst.
100
98
96
94
92
90
88
86
84
82
80
Conversion
Selectivity
The present catalyst afforded a simple way for separating the
catalyst from the reaction mixture due to the heterogeneous
nature and magnetic properties of the catalyst. This is shown in
Fig. 6. The catalyst was easily recoverable by using an external
permanent magnet.
We also investigated the recycling of the catalyst. It was
successfully recycled and reused six times in the epoxidation of
cyclohexene with no significant loss of activity, as shown in
Fig. 7. As can be seen, the conversion of cyclohexene and
selectivity to epoxide were almost unchanged after six reaction
cycles. ICP analysis of the filtrate confirmed that the metal
1
2
3
4
5
6
Reaction cycle
Fig. 7. Reuse of the 20 wt% MoOx/HAP-Ȗ-Fe2O3 catalyst. Reaction
conditions: cyclohexene 5 mmol, TBHP 5 mmol, catalyst 25 mg, CHCH3
6 ml, 70 oC, 8 h.

YUAN Chengyuan et al. / Chinese Journal of Catalysis, 2011, 32: 1166–1172
Table 3 Epoxidation of olefins catalyzed by the 20 wt% MoOx/HAP-
Ȗ-Fe2O3 catalyst
Substrate
2
3
Juwiler D, Neumann R. Catal Lett, 2001, 72: 241
Teixeira S, Dallmann K, Schuchardt U, Buffon R. J Mol Catal A,
2002, 182-183: 167
Product
O
X/% S/%
4
5
Jia M, Thiel W R. Chem Commun, 2002: 2392
Nunes C D, Pillinger M, Valente A A, Rocha J, Lopes A D, Gon-
calves I S. Eur J Inorg Chem, 2003, 21: 3870
Shokouhimehr M, Piao Y Z, Kim J Y, Jang Y J, Hyeon T W.
Angew Chem, Int Ed, 2007, 46: 7039
72.8 97.2
98.4 100
O
O
6
7
8
9
79.2 86.4
91.5 94.2
Lü Zh R, Guo Q L, Yin Y Q, Jin D S. Chin J Catal, 1992, 13:
198
O
Wang L, Ma T, Sheng W, Guo X F, Ding W P, Chen Y. Chin J
Catal, 2009, 30: 711
53.8 100
48.7 100
O
Morent S, Vasseur S, Grasset F, Duguet E. J Mater Chem, 2004,
14: 2161
O
Reaction conditions: olefin 5 mmol, TBHP 5 mmol, catalyst 25 mg,
CHCH3 6 ml, 70 oC, 8 h. Conversion and selectivity for olefins were
determined by GC using an internal standard (decane) technique.
10 Astruc D, Lu F, Aranzaes J R. Angew Chem, Int Ed, 2005, 44:
7852
11 Melero J A, van Grieken R, Morales G. Chem Rev, 2006, 106:
3790
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3 Conclusions
We have developed a new magnetically recyclable and effi-
cient nanocomposite catalyst for the epoxidation of olefins
using molybdenum oxide nanoparticles supported on hy-
droxyapatite-encapsulated Ȗ-Fe2O3 nanocrystallites. This
catalyst showed several attractive features for practical appli-
cations. First, Ȗ-Fe2O3 nanocrystallites were dispersed within
the HAP matrix. Second, the magnetic core was protected by
hydroxyapatite, which makes its use under harsh reaction
conditions possible. Third, the magnetic core allowed the easy
recovery and recycling of the catalyst with no significant loss
of catalytic activity. This magnetic nanocomposite catalyst
should find applications in many other industrially important
catalytic processes.
19 Hara T, Kaneta T, Mori K, Mitsudome T, Mizugaki T, Ebitani K,
Kaneda K. Green Chem, 2007, 9: 1246
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