Aminopropyl group-modified SBA-15 covalent attachment Mn(salen) complexes as catalysts for styrene epoxidation

Article abstract of DOI:10.1080/10426507.2014.979983

A series of aminopropyl group-modified ordered mesoporous silica materials impregnated with Mn(salen) were prepared using successive grafting procedures. The prepared composite catalysts were well characterized by inductively coupled plasma atomic emissio

Full text of DOI:10.1080/10426507.2014.979983

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Phosphorus, Sulfur, and Silicon and the Related
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Aminopropyl group-modified SBA-15 covalent
attachment Mn(salen) complexes as catalysts for
styrene epoxidation
a
ab
a
ab
ab
a
Lili Liu , Jianglei Hu , Jiaojiao He , Haojie Lu , Yong Xu & Fengwei Shi
a
School of Chemical Engineering, Changchun University of Technology, Changchun 130012, P.
R. China
b
Advanced Institute of Materials Science, Changchun University of Technology, Changchun
130012, P. R. China
Accepted author version posted online: 14 Nov 2014.
To cite this article: Lili Liu, Jianglei Hu, Jiaojiao He, Haojie Lu, Yong Xu & Fengwei Shi (2014): Aminopropyl group-modified
SBA-15 covalent attachment Mn(salen) complexes as catalysts for styrene epoxidation, Phosphorus, Sulfur, and Silicon and the
Related Elements, DOI: 10.1080/10426507.2014.979983
To link to this article: http://dx.doi.org/10.1080/10426507.2014.979983
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Aminopropyl group-modified SBA-15 covalent attachment Mn(salen) complexes as
catalysts for styrene epoxidation
a
a,b1
a
a,b
a,b
a*
Lili Liu , Jianglei Hu , Jiaojiao He , Haojie Lu , Yong Xu , Fengwei Shi
a
School of Chemical Engineering, Changchun University of Technology, Changchun 130012,
P. R. China
b
Advanced Institute of Materials Science, Changchun University of Technology, Changchun
1
30012, P. R. China
1
Corresponding author. Tel. or Fax: +86-431-85717353.
E-mail address: hujl863@163.com.
1
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Abstract
A series of aminopropyl group-modified ordered mesoporous silica materials impregnated
with Mn(salen) was prepared using successive grafting procedures. The prepared composite
catalysts were well-characterized by inductively coupled plasma atomic emission spectroscopy,
Fourier transform infrared, UV–vis diffuse reflectance spectroscopy, X-ray diffraction analysis,
and transmission electron microscopy in order to confirm the structure integrities of the
Mn(salen) units after the incorporation, to evidence the formation of the covalent bond between
the starting Mn(salen) units and the aminopropyl group-modified SBA-15 matrix in the
presence of NaOH by abstraction of a molecule HCl. These heterogeneous catalysts exhibited
comparable catalytic activity and selectivity to those of the homogeneous counterpart in the
epoxidation of styrene by using NaClO as the oxidant. In addition, the effects of key reaction
parameters, including the loadings of the neat Mn(salen), molar ratios of NaClO to styrene, and
PPNO amount on the reactivity and selectivity, were also studied. Finally, the reusability of the
prepared heterogeneous catalyst was evaluated.
O
O
N
Si
NH Mn
O
OCH3
O
N
OH
O
o
PPNO, 0 C
NaClO
NaCl
Key words SBA-15; Mn(salen) complex; Heterogeneous; Styrene; Epoxidation
2
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1
. Introduction
Epoxides are a significant class of industrial chemicals that have been widely used as chemical
intermediates in several fields, such as agriculture, industry and medical science, and catalytic
[1-3]
epoxidation of olefins is of great importance for the formation of epoxides . Metal(salen)
[4-6]
complexes have been reported as active catalysts for the epoxidation of olefins . Among all
kinds of the metal(salen) complexes, Mn(salen) complexes exhibit excellent performance
[7-10]
towards the target reactions
. However, the reactions generally proceed in homogeneous
systems, and presented the major problems in separation and recycling at the end of process.
Given the high value of the catalysts and the harm to the environment, the heterogenization of
Mn(salen) complexes has received widespread attention due to its inherent advantages of easy
[11-13]
separation, recycling, and better handling properties
. For this purpose, many strategies for
the heterogenization of the homogeneous catalysts include immobilizing metal(salen) complexes
[14]
on poly-meric organic materials such as resins, or polystyrene , then supported on inert porous
[15]
[10]
[16]
solid such as alumina , and silica or encapsulated in the pores of zeolite-Y . Among them,
there has been an enormous evolution in the strategies to heterogenize metal(salen) complexes
into/onto inorganic supports or inorganic-organic hybrid supports and organic polymers, in
which the host-guest interaction is either chemical or physical.
In the current work, we designed and prepared a series of catalytically active, selective, and
stable Mn(salen)-containing composite catalysts by immobilizing the Mn(salen) unit onto the
aminopropyl group-functionalized SBA-15 silica materials via the covalence of Mn centers in
3
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the Mn(salen) unit with nitrogen atoms of aminopropyl group-functionalized SBA-15 silica
materials in the presence of NaOH by abstraction of a molecule HCl.
The prepared composite catalysts were well-characterized by inductively coupled plasma
atomic emission spectroscopy (ICP-AES), Fourier transform infrared (FT-IR) spectroscopy, UV-
vis diffuse reflectance spectroscopy (UV-vis/DRS), low-angle X-ray diffraction (LXRD)
analysis, and transmission electron microscopy (TEM) in order to confirm the structure
integrities of the Mn(salen) unit after the incorporation, to evidence the formation of the covalent
bond between the starting Mn(salen) unit and the aminopropyl group-modified SBA-15 matrix.
The resulting heterogeneous catalysts possess highly well-defined mesoporous structure.
Meanwhile, the as-synthesized Mn(salen)-NH/SBA-15 materials showed efficient activity and
selectivity for the catalytic epoxidation of styrene (Scheme 1). The influences of key reaction
parameters, including the Mn(salen) loadings, axial ligand, molar ratios of NaClO to styrene, and
reaction time were also studied. Finally, the reusability of the catalysts was evaluated.
2
2
. Results and discussion
.1 Characterization techniques
Low angle XRD (LXRD) patterns were obtained on a D/max-2200 VPC diffractometer using
CuKa radiation. TEM images were obtained on a JEOL JEM-2010 transmission electron
microscope at an accelerating voltage of 200 kV. FT-IR spectra were recorded on a Nicolet
Magna 560 IR spectrophotometer. UV–Vis diffuse reflectance spectra (UV–Vis/DRS) were
−
1
recorded on a Cary 500 UV–Vis–NIR spectrophotometer with a frequency interval of 1 cm .
Loading of Mn(salen) was determined on a Leeman Prodigy Spec inductively coupled plasma
atomic emission spectrometer (ICP-AES).
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2
.2 Characterization of catalyst
.2.1 FI-IR
2
The FT-IR spectra of SBA-15, NH /SBA-15, Mn(salen) and Mn(salen)-NH/SBA-15(6.4)
2
-1
-
materials were presented in Figure 1. A pair of weak absorption peaks at 2985 cm and 2937 cm
1
was ascribed to the symmetric and asymmetric of the saturation of C–H, manifesting that the
[3]
modified aminopropyl groups successfully into silicon matrix surface (NH
2
/SBA-15) . From
Figure 1, it can be seen that the heterogeneous catalyst displayed the similar vibrational
-1
absorption bands as the starting Mn(salen) complex. Concretely, the band at 1540 cm and the
-1
peak at 542 cm , attributed to the characteristic absorption peak and the stretching vibrations of
the Mn–O bond of the complex can be observed in the heterogeneous catalyst Mn(salen)-
[17,18]
NH/SBA-15(6.4)
,demonstrating that the Mn(salen) complex was immobilized on the
support.
2
.2.2 UV-Vis/DRS
The characteristic UV-Vis/DRS spectra of homogeneous and heterogeneous Mn(salen)
materials were presented in Figure S 1 (Supplemental Materials). It revealed that the
characteristic absorption bands related to the starting Mn(salen) complexes were still found in
the heterogeneous Mn(salen)-NH/SBA-15(6.4) material. That was to say, the Mn(salen) complex
exhibited four absorption bands at 261 nm, 331 nm, 431 nm, and 518 nm, which were assigned
to –* transition of the phenyl ring on salen, n–* transition of azomethine C=N bond, charge-
[19,20]
transfer between the Mn and ligand, and d–d transition of Mn(III), respectively
.The result
implied that the primary structure of the starting Mn(salen) remained intact after the
immobilization.
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2
.2.3 Low-angle of XRD
LXRD patterns of SBA-15, NH /SBA-15, and Mn(salen)-NH/SBA-15(6.4) materials were
2
presented in Figure 2. The results showed that all of the materials exhibited three well-resolved
peaks at 0.95, 1.69, and 1.96 deg, which were respectively indexed as the (100), (110), and (200)
reflections of p6mm hexagonal symmetry. As for the three SBA-15 materials, their (100), (110),
and (200) reflections still existed, but the peak intensities decreased in the order SBA-15  NH -
2
SBA-15  Mn(salen)-NH/SBA-15(6.4). Compared with SBA-15 support values, decreased peak
intensities for the Mn(salen)-NH/SBA-15(6.4) sample could be explained in term of the presence
of high Mn(salen) unit and APS contents in the mesoporous Mn(salen)-NH/SBA-15(6.4)
channels, which could partially disturb the assembly of the mesophase.
2
.2.4 TEM
The ordered mesostructure of Mn(salen)-NH/SBA-15(6.4) material was further confirmed by
TEM observation; some representative results were shown in Figure 3. Despite the aminopropyl
groups functionalization of SBA-15 with the Mn(salen) units, the highly ordered mesostructure
of SBA-15 was maintained over extensive regions of observation. The observation indicated that
the prepared composite exhibited hexagonal lattice fringes with uniformly parallel cylindrical
pore channels, meaning that the material possessed a two-dimensionally ordered hexagonal
symmetry (p6mm) structure.
2
.3 Catalytic activity studies
The catalytic performance of the prepared catalyst was studied by the catalytic epoxidation of
styrene. In order to compare, that of the homogeneous Mn(salen) and silica support SBA-15
were tested under identical condition. The effect of various experiment parameters, including the
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loadings of the neat Mn(salen), the PPNO amount, and molar ratios of NaClO to styrene were
studied and the situations were stated as follows.
2
.3.1 Catalyst text
Before epoxidation reaction, the catalyst was activated at 373 K for 2 h. Catalytic epoxidation
of styrene was carried out in a sealed round-bottom flask (25 mL) for 24 h under vigorous
stirring at 273 K (Scheme 1). In a typical experiment, styrene (1.0 mmol), octane (internal
standard, 1.0 mmol), 4-PPNO (0.3 mmol), CH
2
Cl
2
(3 mL), aqueous NaClO solution (pH 11.3,
0
.55 M, 2.0 mmol), and the catalyst powder (containing Mn(salen) 0.018 mmol). Changes of the
concentrations of alkene and epoxide in the system were monitored quantitatively by a
multicolumn Agilent Technologies 6890N gas chromatograph with thermal conductivity (TCD)
and flame ionization (FID) detectors. The performance of the catalysts was evaluated by the
yield of epoxide (Yield%), the selectivity to epoxide (Selectivity%), and the conversion of
styrene (Conversion%). Herein, Yield% = (N
Y
/N
E
) × 100, where N
Y
and N are the number of
E
moles of the epoxides yielded and expected; Selectivity% = Yield% /Conversion% × 100.
2
.3.2 Effect of the different catalysts
The catalytic activity of a series of catalysts was compared and the results were described in the
Table 1. The blank experiment was tested at first. Blank experiment showed that the SBA-15
support alone was inactive towards the styrene epoxidation (entry 1 in Table 1). However,
significant conversion of styrene to styrene epoxide was found in the presence of homogeneous
Mn(salen) complexes as well as heterogeneous Mn(salen) materials (entries 2-5 in Table 1).
Moreover, in current catalytic system, styrene epoxide was the only product. The influence of
Mn(salen) complex loadings on the catalytic activity of Mn(salen)-NH/SBA-15 materials were
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evaluated by the representative catalyst. Increased Mn(salen) loading from 3.5% to 7.1%, the
yield of styrene epoxide increased from 47.2% to 89.2% for 24 h (entries 3-5 in Table 1). These
results show that the reactivity increased when the Mn(salen) loading was increased from 3.5 to
6
.4%; further increasing the Mn(salen) loading to 7.1% did not have any effect on the reactivity.
Hence, in the following catalytic tests, the most active catalyst, Mn(salen)-NH/SBA-15(6.4),
was selected to study the influence of key reaction parameters on the catalytic activity,
selectivity, recovery, and reuse of the immobilized Mn(salen) complexes.
2
.3.3 Effect of the axial ligand (PPNO)
The contribution of PPNO to the homo- or heterogeneous Mn(salen) complex-catalyzed styrene
epoxidation reaction is studied and the results are summarized in Table S 1 (Supplemental
Materials). It shows that PPNO applied in current catalytic system can obviously enhance the
[3]
catalytic activity of both of the homogeneous and heterogeneous Mn(salen) complexes . Under
the same conditions, increased PPNO amount from 0 to 0.3 mmol, the yield of styrene epoxide
increased from 2.8% to 88.9% (entries 3-6 in Table S 1 Supplemental Materials). But, further
increasing the PPNO amount to 0.6 mmol did not have any effect on the reactivity.
2
.3.4 Effect of molar ratio of NaClO to styrene
Epoxidation of styrene catalyzed by the Mn(salen)-NH/SBA-15(6.4) catalyst at the different
molar ratios of NaClO to styrene in the reaction system was studied; the result is shown in Figure
. It was found that the yield of styrene epoxide increased from 23.2 to 80.2 % as the molar ratio
4
of NaClO to styrene increased from 1:1 to 4:1. This suggested that a suitable excess of oxidant
could improve the catalytic activity and selectivity. However, the selectivity of styrene declined
to 81.6% rapidly when the molar ratio of NaClO to styrene was 4:1, which was responsible for
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the open-ring or bond-broken reaction of styrene epoxides in the presence of excessive NaClO
solution. Therefore, the molar ratio of NaClO to styrene should be controlled at 2:1, which was
the first and foremost condition of high conversion and selectivity.
2
.3.5 Effect of the reaction time
From the result displayed in Figure 5, one can see that the conversion of styrene as well as the
yield of epoxide increased rapidly at the beginning of the reaction. After the reaction proceeded
for 10 h, the reaction rate began to slow down. The reaction proceeded more slowly on further
increasing the reaction time. However, the selectivity to epoxide remained unchanged basically
throughout the entire reaction procedure. When the time was 24 h, the conversion and yield were
both up to 88.9%. Moreover, the selectivity kept at 100% during the whole reaction.
To confirm the absence of the active site (Mn(salen)) leaching into the reaction medium
during the catalytic course, we carried out the reaction at 273 K for 3 h, and then we removed the
catalyst by filtration. The catalyst-free reaction liquor was allowed to react further for 24 h;
however, no further conversion of styrene was detected, consistent with a stable heterogeneous
catalyst (Figure 5). Meanwhile, the catalyst-free reaction solutions were analyzed by ICP-AES
to estimate the drop of Mn(salen). As expected, Mn was hardly detected in the catalyst-free
reaction solution.
2
.3.6 The reusing of the heterogeneous Mn(salen) catalyst
Alkene epoxidation catalyzed by Mn(salen) complexes in the presence of strong oxidizing
reagents often suffered from deactivation due to the ligand degradation. Therefore, the catalytic
stability of heterogeneous Mn(salen) complexes was evaluated through three consecutive styrene
epoxidation cycles catalyzed by Mn(salen)-NH/SBA-15(6.4) material. After the first run, the
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used catalyst was recovered by filtration and then washed thoroughly with dichloromethane. The
results showed that the Mn(salen)-NH/SBA-15(6.4) catalyst retained most of its initial activity
(
Figure 6) after three consecutive styrene epoxidation cycles: the yield of styrene epoxide was
8.9%, 85.0%, and 79.6%, respectively, for the 1st, 2nd and 3rd run. The results indicated that
8
the prepared heterogeneous catalyst had excellent thermal stability. The decline of conversion
and yield may be the loss of catalyst during the washing and recycling process.
2
.3.7 Reaction mechanism consideration
Taking into account the product yielded (styrene epoxide) in the current catalytic system, the
reaction mechanism was proposed. In the first step, oxygen transferred from a donor (NaClO) to
III
Mn center of Mn (salen)-NH/SBA-15 occurred, leading to a higher valent
V
[21]
oxomanganese(salen)(V) active species, O=Mn (salen)-NH/SBA-15 . In the second step, the
V
oxygen atom of O=Mn (salen)-NH/SBA-15 species attacked nucleophilically on the carbon
atom with lower electron cloud density of C=C bond within the alkenes, leading to the formation
[22]
of radical intermediate . In the third step, the radical intermediate was directly collapsed and
formed the epoxide. Simultaneously, the catalyst restored its initial state due to the loss of an
oxygen atom.
3
. Experimental
3
.1 Materials
4
-phenylpyridine N-oxide, and Pluronic P123 (MW=5800) was purchased from sigma-aldrich
(
(
Shanghai), 3-aminopropyl-triethoxysilane (98.0%) was purchased from Aladdin Chemistry Co.
Shanghai). Styrene (99.0%) and Tetraethyl orthosilicate (TEOS, 98.0%) were purchased from
Tianjin Fuchen Chemical Reagent Factory (China). All other chemicals were analytical grade
1
0
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and were purchased from Beijing Fine Chemical Co. (China) and used without further
purification.
3
3
.2 Catalyst preparation
.2.1 Synthesis Mn(salen) complex
Homogeneous Mn(salen) complex was synthesized following the procedures illustrated in
[23,24]
Scheme 2a. Preparation of Mn(salen) complexe was carried out by the literature methods
.
3
.2.2 Preparation of silica support SBA-15
Highly ordered mesoporous SBA-15 was synthesized using a modified procedure based on the
[25]
literature method . In a typical synthesis, P123 (1.0 g) was dissolved in distilled water (15 mL)
-1
to which aqueous HCl solution (2 mol·L , 30 mL) was added under stirring at 308 K for 3 h, and
then TEOS (4.0 g) was added into the above solution under stirring at 308 K for 20 h. The
resulting mixture was aged under static hydrothermal conditions at 353 K for 24 h. The separated
white product powder was washed with distilled water for three times, and then it was dried for
4
8 h at 373 K. Surfactant template P123 was removed from the product by extracting with
ethanol in the presence of HCl (2 M). After being dried at 373 K for 24 h, the final product was
formed and denoted as SBA-15.
3
.2.3 Preparation of amine-functionalized SBA-15 (NH
-Aminopropyl-trimethoxysilane (APS, 1 mL) was dispersed into a suspension including
ethanol (50 mL) and SBA-15 (1 g). The mixture was stirred vigorously at room temperature for
4 h, and then the product was recovered by centrifugation after washing with ethanol and
2
/SBA-15)
3
2
[26,27]
diethyl ether, respectively
. The final product was formed and denoted as NH -SBA-15. The
2
preparation procedure was shown in Scheme 2b.
1
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3
.2.4 Preparation of heterogeneous Mn(salen) catalysts
The preparation procedure was shown in Scheme 2. The mixture of Mn(salen) (0.2-0.5 g) and
modified support (NH /SBA-15, 0.5 g) were added to THF (25 mL) for 24 h in the presence of
2
[28]
NaOH (0.6-1.6 mmol) at room temperature .The resulting solid product was filtrated, washed
thoroughly with THF then ethanol for three times, and the separated brown powder was dried in
vacuum at 353 K. The final product was denoted as Mn(salen)-NH/SBA-15-x (where x presents
Mn(salen) loading amount (wt.%) in the product, which was determined by a Leeman Plasma
Spec (I) ICP-AES.).
4
. Conclusions
A series of ordered mesoporous Mn(salen)-NH/SBA-15 composite catalysts for epoxidation of
styrene was developed. The structures of the starting Mn(salen) unit was maintained in the
composite catalysts, and the interaction between the Mn(salen) unit and the aminopropyl group-
functionalized SBA-15 material is the Mn-N covalent bond in the presence of NaOH. Under
identical reaction conditions, this heterogeneous catalyst showed comparable catalytic activity
and selectivity to the corresponding homogeneous counterpart towards the epoxidation of styrene
into epoxide using NaClO as oxidant. Meanwhile, factors including the loadings of the
Mn(salen), molar ratios of NaClO to styrene, PPNO amount, and reaction time also had obvious
influences on the reactivity and selectivity. Importantly, the prepared Mn(salen) complexes can
be reused at least three times without obvious loss of activity.
Acknowledgments
This work was supported by the Natural Science Fund Council of China (21203013).
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References
[
1] Kamata, K.; Yonehara, K.; Sumida, Y.; Yamaguchi, K.; Hikichi, S.; Mizuno, N. Science.
003, 300, 964-966.
2
[
[
2] Palucki, M.; McCormick, G. J.; Jacobsen, E. N. Tetrahedron Lett., 1995, 36, 5457-5460.
3] Hu, J. L.; Wu, Q. Y.; Li, W.; Ma, L.; Su, F.; Guo, Y. H.; Qiu, Y. Q. ChemSusChem. 2011, 4,
1
813-1822.
4] Cheung, K. C.; Wong, W. L.; Ma, D. L.; Lai, T. S.; Wong, K. Y. Coord. Chem. Rev. 2007,
51, 2367-2385.
5] Zhang, W.; Loebach, J. L.; Wilson, S. R.; Jacobsen, E. N. J. Am. Chem. Soc. 1990, 112,
801-2803.
[
[
2
2
[
[
6] Parida, K. M.; Sahoo, M.; Singha, S. J. Catal. 2010, 276, 161-169.
7] Aerts, S.; Weyten, H.; Buekenhoudt, A.; Gevers, L. E. M.; Vankelecom, I. F. J.; Jacobs, P. A.
Chem. Comm. 2004, 710-711.
[
[
[
8] Bigi, F.; Moroni, L.; Maggi, R.; Sartori, G. Chem. Commun. 2002, 716-717.
9] Zhang, H.D.; Li, C. Tetrahedron. 2006, 62, 6640–6649.
10] Hatefi, M.; Moghadam, M.; Sheikhshoaei, I.; Mirkhani, V.; Tangestaninejad, S.;
Mohammadpoor-Baltork, I.; Kargar, H. Appl. Catal. A: 2009, 370, 66-71.
11] Dell'Anna, M. M.; Gallo, V.; Mastrorilli, P.; Romanazzi, G. J. Molecules. 2010, 15, 3311-
[
3
318.
[
[
[
12] Sellner, H.; Karjalainen, J. K.; Seebach, D. Chem. Eur. J. 2001, 7, 2873-2887.
13] Bhattacharjee, S.; Anderson, J. A. Chem. Commun. 2004, 554-555.
14] Maurya, M. R.; Kumar, A. J. Mol. Catal. A: Chem. 2006, 250, 190-198.
1
3
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[
[
[
[
15] Salavati-Niasari, M.; Amiri, A. Appl. Catal. A: Gen. 2005, 290, 46-53.
16] Varkey, S. P.; Ratnasamy, C.; Ratnasamy, P. J. Mol. Catal. A: Chem. 1998, 135, 295-306.
17] Yang, H. Q.; Zhang, L.; Wang, P.; Yang, Q. H.; Li, C. Green Chem. 2009, 11, 257-264.
18] Choudary, B. M.; Ramani, T.; Maheswaran, H.; Prashant, L.; Ranganath, K. V. S.; Vijay
Kumar, K. Adv. Synth. Catal. 2006, 348, 493-498.
[
[
[
19] Zhang, H. D.; Zhang, Y. M.; Li, C. J. Catal. 2006, 238, 369-381.
20] Crawford, S. M. Spectrochim. Acta, 1963, 19, 255-270.
21] Campbell, K. A.; Lashley, M. R.; Wyatt, J. K.; Nantz, M. H.; Britt, R. D. J. Am. Chem. Soc.
2
001, 123, 5710-5719.
22] Linde, C.; Åkermark, B.; Norrby, P. O.; Svensson, M. J. Am. Chem. Soc. 1999, 121, 5083-
084.
[
5
[
[
23] Zhang, W.; Jacobsen, E.N. J. Org. Chem. 1991, 56, 2296-2298.
24] Amarasekara, A. S.; McNeal, I.; Murillo, J.; Green, D.; Jennings, A. Catal. Comm. 2008, 9,
2
437-2440.
25] Zhao, D. Y.; Huo, Q. S.; Feng, J. L; Chmelka, B. F.; Stucky, G. D. J. Am. Chem. Soc. 1998,
20, 6024-6036.
[
1
[
[
[
26] Utting, K. A.; Macquarrie, D. J. New J. Chem. 2000, 24, 591-596.
27] Hu, J. L.; Li, K. X.; Li, W.; Ma, F. Y.; Guo, Y. H. Appl. Catal. A: Gen. 2009, 364, 211-220.
28] Gong, B. W.; Fu, X. K.; Chen, J. X.; Li, Y. D.; Zou, X. C.; Tu, X. B.; Ding, P. P.; Ma, L. P.
J. Catal. 2009, 262, 9-17.
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SBA-15
NH /SBA-15
2
2937
2
985
Mn(salen)
5
36
1540
Mn(salen)-NH/SBA-15(6.4)
5
42
1540
4000
3000
2000
1000
-1
Wavenumber ( cm )
Figure 1 FT-IR spectra of SBA-15, NH /SBA-15, Mn(salen) and Mn(salen)-NH/SBA-15(6.4)
2
materials.
1
5
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(
100)
(110)
(200)
SBA-15
NH /SBA-15
2
Mn(salen)-NH/SBA-15(6.4)
2
1
3
2
Theta (deg)
Figure 2 LXRD patterns of SBA-15, NH /SBA-15 and Mn(salen)-NH/SBA-15(6.4) materials.
2
a
b
)
Figure 3 Transmission electron micrographs of Mn(salen)-NH/SBA-15(6.4) material
1
6
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Conversion
Yield
Selectivity
1
00
75
50
25
0
1
: 1
2 : 1
4 : 1
The molar ratio of NaClO to styrene
Figure 4 The effect of molar ratio of NaClO to Styrene on the catalytic activity and selectivity of
Mn(salen)-NH/SBA-15 materials towards styrene epoxidation. Free Mn(salen) complex 0.018
mmol, CH
2
Cl 3 mL, styrene 1.0 mmol, PPNO 0.3 mmol, n-octane 1.0 mmol, 273 K, 24 h.
2
1
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100
80
60
40
20
0
Selectivity
Yield
Catalyst free
0
5
10
15
20
25
Time (h)
Figure 5 Time courses of epoxidation of styrene with NaClO to produce epoxide in the presence
of Mn(salen)-NH/SBA-15(6.4) material. Free Mn(salen) complex 0.018 mmol, CH
2
Cl
2
3 mL,
styrene 1.0 mmol, NaClO 2.0 mmol, PPNO 0.3 mmol, n-octane 1.0 mmol, 273 K, 24 h.
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Conversion
Yield
Selectivity
100
7
5
0
5
0
5
2
1
st
2nd
3rd
Repeating Time
Figure 6 Recyclability of the Mn(salen)-NH/SBA-15(6.4) material towards the styrene
epoxidation reaction. Free Mn(salen) complex 0.018 mmol, CH
2
Cl
2
3 mL, styrene 1.0 mmol,
NaClO 2.0 mmol, PPNO 0.3 mmol, n-octane 1.0 mmol, 273 K, 24 h.
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O
Si
O
O
N
NH Mn
OCH3
O
N
OH
O
o
PPNO, 0 C
NaClO
NaCl
Scheme 1 Reaction of oxidation of styrene to produce styrene epoxide with NaClO catalyzed by
Mn(salen)-NH/SBA-15 materials.
N
O
N
O
CHO
OH
N
N
Mn(OAc) 4H O
2
2
Mn
Cl
(a)
H2N
NH2
OH HO
LiCl
Mn(salen)
O
O
N
EtO
EtO Si
EtO
O
OH
OH
Si
NH2
Mn(salen)
NH Mn
Si
O
(b)
NH2
O
OEt
O
N
OEt
NaOH
OH
OH
OH
SBA-15
APS
NH /SBA-15
Mn(salen)-NH/SBA-15
2
Scheme 2 Pathway of the prepared of heterogeneous catalyst Mn(salen)-NH/SBA-15.
2
0
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Table 1 Effect of various catalysts on the catalytic activity and selectivity of Mn(salen)-
NH/SBA-15 materials towards styrene epoxidation.
Entry
Catalyst
Conversion (%)
Yield (%) Selectivity (%)
1
2
3
4
5
SBA-15



Mn(salen)
94.6
47.2
88.9
89.2
94.6
47.2
88.9
89.2
100
100
100
100
Mn(salen)-NH/SBA-15(3.5)
Mn(salen)-NH/SBA-15(6.4)
Mn(salen)-NH/SBA-15(7.1)
Free Mn(salen) complex 0.018 mmol, CH
2
Cl 3 mL, styrene 1.0 mmol, NaClO 2.0 mmol, PPNO
2
0
.3 mmol, n-octane 1.0 mmol, 273 K, 24 h.
2
1
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