Immobilized metalloporphyrins in mesoporous MCM-48 as efficient and selective heterogeneous catalysts for oxidation of cyclohexene

Article abstract of DOI:10.1007/s00706-012-0854-x

Three metalloporphyrins, Mn(III)TClPPCl, Fe(III)TClPPCl, and Co(II)TClPP (TClPP = 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin), were synthesized and immobilized in MCM-48 channels. The designed heterogeneous catalysts were characterized by XRD, ICP, UV-Vis, FT-IR, N₂ adsorption-desorption, and scanning electron microscopy. These investigations showed that successful encapsulation occurred and the framework of mesoporous MCM-48 was retained without any change after incorporation of the metalloporphyrins. The effect of the support on the resistance to pore blocking was studied by comparing MCM-48 with MCM-41. The catalytic activities of the newly synthesized catalysts were examined in the oxidation of cyclohexene with t-butyl hydroperoxide as oxidant. All results confirmed that the supported catalysts presented interesting advantages such as high selectivity to the allylic products and more resistance to pore blocking. The heterogeneous catalysts were reused for several times without significant loss of their catalytic activity.

Full text of DOI:10.1007/s00706-012-0854-x

Monatsh Chem (2013) 144:597–603
DOI 10.1007/s00706-012-0854-x
ORIGINAL PAPER
Immobilized metalloporphyrins in mesoporous MCM-48
as efficient and selective heterogeneous catalysts for oxidation
of cyclohexene
Nafiseh Rahmani Khalili
Mahboubeh Rabbani
•
Rahmatollah Rahimi
•
Received: 18 May 2012 / Accepted: 24 August 2012 / Published online: 26 September 2012
Ó Springer-Verlag 2012
Abstract Three metalloporphyrins, Mn(III)TClPPCl,
Fe(III)TClPPCl, and Co(II)TClPP (TClPP = 5,10,15,20-
tetrakis(4-chlorophenyl)porphyrin), were synthesized and
immobilized in MCM-48 channels. The designed hetero-
geneous catalysts were characterized by XRD, ICP,
easily recyclable catalyst [1–4]. Metalloporphyrins are able
to imitate the activity of cytochrome P-450 and to catalyze
selective oxidation processes with a diversity of oxygen
donors [5–8]. The allylic oxidation of olefins, especially
cyclohexene and its derivatives into a,b-unsaturated
ketones, is an important process because allylic ketones are
valuable intermediates for the synthesis of medicines and
pesticides [9–11]. However, metalloporphyrins as homo-
geneous catalysts have several problems, for instance their
oxidative self-destruction in the oxidizing media; further-
more, they are not able to be simply recovered for reuse at
the end of the reaction. One of the suggested ways to solve
these problems is to immobilize homogeneous catalysts on
a solid matrix. It is expected that some advantages like
promoting catalytic activity, stability, product selectivity,
and easy reusability will be achieved by immobilization
[12–18].
UV–Vis, FT-IR, N adsorption–desorption, and scanning
2
electron microscopy. These investigations showed that
successful encapsulation occurred and the framework of
mesoporous MCM-48 was retained without any change
after incorporation of the metalloporphyrins. The effect of
the support on the resistance to pore blocking was studied
by comparing MCM-48 with MCM-41. The catalytic
activities of the newly synthesized catalysts were examined
in the oxidation of cyclohexene with t-butyl hydroperoxide
as oxidant. All results confirmed that the supported catalysts
presented interesting advantages such as high selectivity to
the allylic products and more resistance to pore blocking.
The heterogeneous catalysts were reused for several times
without significant loss of their catalytic activity.
Since the invention of M41S researchers have given
considerable attention to them, because these materials
possess larger pores in contrast with microporous molec-
ular sieves, which allow faster diffusion and processing of
bulky molecules [19–22], so they have high potential use as
adsorbents, heterogeneous catalysts, catalytic supports, and
hosts for inclusion compounds [23, 24]. Most studies have
concentrated on investigating the properties of mesoporous
MCM-41 as supports for heterogenization of metallopor-
phyrins and other complexes [25–30]. In comparison with
MCM-41, which has a unidirectional pore system, MCM-
48 has more advantages, such as narrow pore size distri-
bution and its interwoven as well as branched, regular, and
cubic pore structure, that bring more favorable mass
transfer kinetics in catalytic and separation technologies.
Therefore it is a more beneficial candidate for application;
moreover, its three-dimensional channels allow faster dif-
fusion and are more resistant to pore blocking [31–36].
Keywords Metalloporphyrins Á MCM-48 Á
Heterogeneous catalysts Á Cyclohexene oxidation
Introduction
From the point of view of green chemistry and chemical
industry, one of the challenging goals is the selective
catalytic oxidation of organic compounds using environ-
mentally friendly and cheap oxidants and a heterogeneous,
N. R. Khalili Á R. Rahimi (&) Á M. Rabbani
Department of Chemistry, Iran University of Science and
Technology, Narmak, 16846-13114 Tehran, Iran
e-mail: rahimi_rah@iust.ac.ir
123

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N. R. Khalili et al.
O
OH
M(TClPP)X-MCM48
+
+
O
CH CN, TBHP
3
Cyclohexene
Epoxycyclohexane
2-Cyclohexene-1-one
2-Cyclohexene-1-ol
M = Fe, Mn, Co
X = Cl, OAc
Scheme 1
However, despite these advantages less attention has been
paid to MCM-48. Up to now, only one relevant paper, by
Zhang and co-workers [37], has been reported on immo-
bilizing chiral ruthenium porphyrin [Ru(D -Por*)CO] in
4
modified MCM-48 as catalysts for asymmetric epoxidation
by 2,6-dichloropyridine N-oxide, so this encouraged us to
examine the application of MCM-48 as a catalyst support
in different conditions with other metalloporphyrins.
In the present work, Fe(III), Mn(III), and Co(II) com-
plexes of meso-tetrakis(4-chlorophenyl)porphyrin were
immobilized in mesoporous MCM-48 molecular sieves and
the catalytic activities of these heterogeneous materials
were then investigated in the oxidation of cyclohexene with
t-butyl hydroperoxide (TBHP) as oxidant (Scheme 1).
Results and discussion
Fig. 1 XRD patterns of MCM-48 (a), MnTClPP–MCM48 (b),
FeTClPP–MCM48 (c), and CoTClPP–MCM-48 (d)
Characterization of catalysts
After Soxhlet extractions of supported catalysts, a dark brown
and green powder was obtained, showing that the encapsula-
tion of metalloporphyrins into the MCM-48 was successful.
Low-angle X-ray diffraction (XRD) patterns of calcined
MCM-48 and encapsulated metalloporphyrins (MnTClPP–
MCM48, FeTClPP–MCM48, and CoTClPP–MCM48;
TClPP = 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin) are
given in Fig. 1. All samples show two distinct peaks, (211)
and (220), and several other peaks which can be indexed to
highly ordered three-dimensional cubic structures [40].
Powder diffraction patterns of encapsulated catalysts
(
Fig. 1b–d) show no peaks due to porphyrin and the two basal
peaks are still detectable. This indicates that the MCM-48
framework is still maintained when porphyrin is incorporated.
The observed slight decrease in the peak intensities confirms
loading of complexes into the support.
Fig. 2 FT-IR spectra of calcined MCM-48 (a), FeTClPP–MCM48
(b), MnTClPP–MCM48 (c), and CoTClPP–MCM-48 (d)
Figure 2 shows the FT-IR spectra of MnTClPP–MCM48,
FeTClPP–MCM48, CoTClPP–MCM48, and the pure sup-
attributed to the symmetric and asymmetric stretching
-
1
port. The broad band in the range of 3,700–3,000 cm can
be assigned to the stretching vibration mode of the Si–OH
vibrations for the tetrahedral SiO structure units. Also an
4
-
1
absorption band at around 960 cm
is due to Si–OH
-
1
group. Another band between 450 and 1,200 cm
is
stretching vibrations in the calcined state. In the supported
1
23

Immobilized metalloporphyrins in mesoporous MCM-48
599
2
Fig. 3 N adsorption of calcined MCM-48 and FeTClPP–MCM48
catalysts’ spectra, some new bands appearing between 1,200
-
1
and 1,600 cm corresponding to the phenyl C=C and pyr-
role C=N stretching modes also prove the presence of
metalloporphyrins inside the channels of MCM-48.
The textural properties of the MCM-48 and encapsu-
lated catalysts were determined by a nitrogen adsorption
experiment at 77 K. The adsorption–desorption isotherms
of all samples show that the materials possess the typical
type IV adsorption isotherms, characteristic of mesoporous
solids (Fig. 3). The BET surface area and average pore size
2
-1
˚
and 26 A, respectively.
of MCM-48 are 1,323 m g
After incorporation of metalloporphyrins inside the pores
of MCM-48, decreases in the BET surface area and average
pore size were observed. For example, for FeTClPP–
Fig. 4 SEM images of MCM-48 (a) and MnTClPP–MCM48 (b)
2
-1
˚
MCM48 1,087 m g and 24.8 A were obtained. These
results show that greater amounts of metalloporphyrins
were immobilized inside the channels of the support.
Inductively coupled plasma (ICP) spectroscopy was
used to estimate the loadings of metalloporphyrins in these
heterogeneous catalysts. The results indicate that metallo-
porphyrin contents are as follows: 10.65 wt% in
MnTClPP–MCM48, 17.6 wt% in FeTClPP–MCM48, and
The presence of metalloporphyrins in the channels of
MCM-48 was also confirmed by solid-state UV–Vis
spectroscopy (Fig. 5a–d). In the UV–Vis spectrum of
MCM-48 (Fig. 5a), no absorption band is observed,
whereas after immobilization of metalloporphyrins in
MCM-48 channels, the Q and Soret bands appear. The
position of the Soret bands of Fe(III), Mn(III), and Co(II)
porphyrins dissolved in dichloromethane (non-supported)
and immobilized in MCM-48 (supported) are given in
Table 1.
1
3.48 wt% in CoTClPP–MCM48. Dramatically higher
loadings were obtained, because of the three-dimensional
pore structure of MCM-48 in comparison with the one-
dimensional MCM-41 [8, 16, 37, 41].
The supported catalysts, Mn(III), Fe(III), and Co(II)
(TClPP–MCM48), show Soret bands at 464, 412, and
428 nm, respectively, which are similar to those of the
corresponding non-supported metalloporphyrins; this
observation further indicates that no chemical changes
have occurred to the complexes during the anchoring
processes. However, the solid-state UV–Vis spectra of the
complexes show a red shift in Q and Soret bands in com-
parison with their non-supported counterparts, which can
The typical morphology of MCM-48 and MnTClPP–
MCM48 was investigated by scanning electron microscopy
(
SEM). As can be seen in Fig. 4, the MnTClPP–MCM48
sample shows that similar morphology and crystalline
structure to pure MCM-48. As a result, the solid support is
structurally unchanged and metalloporphyrins should be
diffused molecularly within the channels.
123

6
00
N. R. Khalili et al.
Table 2 Effect of porphyrin content on cyclohexene oxidation with
TBHP catalyzed by FeTClPP–MCM48
a
Porphyrin content /wt% Conversion /%
b
Entry Catalyst
1
2
3
4
FeTClPP–MCM48 0.2
FeTClPP–MCM48 5.8
11.7
32.0
48.3
80.2
FeTClPP–MCM48 10.2
FeTClPP–MCM48 17.6
3
Conditions: TBHP (15 mmol), cyclohexene (10 mmol), 5 cm ace-
tonitrile, 60 °C
a
Determined by ICP spectroscopy
b
Disappearance of cyclohexene using GC
increase in catalytic activity (Table 2). This is due to the
unique nature and properties of mesoporous MCM-48.
Effect of reaction time
Fig. 5 UV–Vis spectra of MCM-48 (a), MnTClPP–MCM48 (b),
FeTClPP–MCM48 (c), and CoTClPP–MCM48 (d)
The effect of reaction time on the oxidation of cyclohexene
in the presence of the FeTClPP–MCM48 catalyst was
studied. As can be seen in Fig. 6, the conversion of sub-
strate to products was optimal after 6 h. With increasing
reaction time up to 24 h, no significant change was
observed in the conversion of substrate or product selec-
tivity, and allylic oxidation products were the major
components.
Table 1 Wavelength of the Soret band maxima of supported and
non-supported catalysts
Catalyst
Soret band/nm
Supported Non-supported in dichloromethane
MnTClPP–MCM48 464
FeTClPP–MCM48 412
CoTClPP–MCM48 428
462
408
426
Effect of catalyst amount and reaction temperature
Table 3 shows the influence of catalyst amount on the
cyclohexene oxidation reaction in the presence of the
supported iron porphyrin catalyst. When the catalyst
amount was increased, the conversion and the yield of
2-cyclohexene-1-one as the main product improved. The
best overall result was obtained with 0.02 g of catalyst
(entry 3). Furthermore, the temperature effect on the pro-
gress of oxidation was studied. It was found that the
oxidation reaction at room temperature was slow (entry 5)
and the conversion was increased with raising temperature
to 60 °C. Therefore, the yield of the reaction depends
considerably on temperature.
be attributed to the distortion of the porphyrin rings usually
observed when metalloporphyrins are immobilized on solid
supports [15, 42].
Catalytic activity
Effect of the support on resistance to pore blocking
The catalytic properties of heterogeneous catalysts in the
oxidation of cyclohexene by TBHP as oxygen transfer agent
were investigated. One of the problems of using MCM-41
as a support is that with increasing porphyrin loading the
catalytic activity decreases, because pore blocking and
limited diffusion of the reactants take place [8, 17, 43–45].
Since MCM-48 has three-dimensional channels, it is
expected to provide more favorable mass transfer kinetics,
better diffusion, and resistance to pore blocking. In order to
investigate this assertion, FeTClPP–MCM48 catalysts
containing 0.2, 5.8, 10.2, and 17.6 wt% of FeTClPP were
prepared. The results of cyclohexene oxidation with TBHP
in the presence of these heterogeneous catalysts with dif-
ferent amounts of Fe(III) porphyrins demonstrated that
increasing amounts of metalloporphyrin loading led to an
Oxidation of cyclohexene
The results of oxidation of cyclohexene using TBHP as
oxidant and acetonitrile as solvent in the presence of the
resultant catalysts are summarized in Table 4.
The blank experiment with pure support (MCM-48) did
not show any oxidation products. This obviously indicates
that metalloporphyrin complexes encapsulated in MCM-48
play the main role in the catalytic activity. All applied
catalysts displayed significant activity in cyclohexene
oxidation reactions. The data in Table 2 highlight the high
selectivity of the process: allylic oxidation is favored over
epoxidation and 2-cyclohexene-1-one appears as the main
1
23

Immobilized metalloporphyrins in mesoporous MCM-48
601
entirely immobilized in the internal pore wall surface of
MCM-48.
The cubic three-dimensional pore openings of MCM-48
provide easy access for the reactants into the active sites of
the metalloporphyrins in mesoporous channels. This
remarkably enhances the catalytic ability and selectivity of
the porphyrin complexes, because it increases the proba-
bility of interaction between reactants and catalytic active
sites; these properties imply that MCM-48 is a good solid
support. From a general point of view, the obtained results
are in agreement with those of Zhang et al. [37], i.e., the
cubic three-dimensional MCM-48 has more advantages as
a catalyst support than the one-dimensional MCM-41.
The dependence between the catalytic activity and the
nature of the central metal of porphyrin ligand is obvious.
Comparison of the catalytic activity of these heterogeneous
catalysts under similar conditions shows that FeTClPP–
MCM48 is better than both MnTClPP–MCM48 and CoT-
ClPP–MCM48 in the oxidation of cyclohexene. The
noticed trend of catalytic activity is FeTClPP–MCM
48 [ MnTClPP–MCM48 [ CoTClPP–MCM48.
Fig. 6 Changes of cyclohexene conversion with reaction time.
Reaction conditions: TBHP (15 mmol), cyclohexene (10 mmol),
3
0
.63 mol% FeTClPP–MCM48, 5 cm acetonitrile, 60 °C
product. This is a remarkable and multifaceted substance
with various applications in the synthesis of a variety of
chemical products like pharmaceuticals and perfumes. The
selectivity pattern indicates that attack at the activated C–H
bond is more preferable than at the C=C bond under our
reaction conditions. Also, on the basis of reported literature
Catalyst recycling and leaching
The reuse and stability of these heterogeneous catalysts
were studied for several times. After finishing the oxidation
[
46], it shows that the metalloporphyrin species are almost
Table 3 Effect of catalyst amount and temperature on oxidation of cyclohexene in the presence of FeTClPP–MCM48
a
Conversion /%
b
Yield /%
Entry
Amount of catalyst/g
Time/h
Temperature/°C
1
2
3
4
5
0.05
0.01
0.02
0.05
0.02
6
6
6
6
6
60
60
60
60
25
35
29.2
47.0
72.0
72.2
28.1
61
80.2
82
32
3
Conditions: TBHP (15 mmol), cyclohexene (10 mmol), 5 cm acetonitrile
a
Disappearance of cyclohexene using GC
b
Yield of 2-cyclohexene-1-one obtained by GC
Table 4 Catalytic oxidation of cyclohexene by TBHP in the presence of supported metalloporphyrin catalysts
b
Cyclohexene conversion /% Epoxide selectivity/% Ketone selectivity/% Alcohol selectivity/% TON TOF /h
c
d
-1
Catalyst
a
Si–MCM48
–
–
–
–
–
–
MnTClPP–MCM48 65
FeTClPP–MCM48 80
CoTClPP–MCM48 54
11.4
3.9
9.3
85.2
95.0
88.4
3.4
1.1
2.3
144.6 24.1
114.2 19.0
105.0 17.5
Conditions: TBHP (15 mmol), cyclohexene (10 mmol), 0.38 mol% MnTClPP–MCM48, 0.63 mol% FeTClPP–MCM48, and 0.45 mol% CoT-
3
ClPP–MCM48, 5 cm acetonitrile, 6 h, 60 °C
a
b
c
d
3
Conditions: MCM-48 (0.02 g), TBHP (15 mmol), cyclohexene (10 mmol), 5 cm acetonitrile
Disappearance of cyclohexene using GC
Turnover number: mole of product per mole of catalyst
Turnover frequency: mole of product per mole of catalyst per hour
123

6
02
N. R. Khalili et al.
reaction, the catalysts were separated by filtration, washed
with acetonitrile followed by methanol, and dried at 80 °C
for 12 h before using in the subsequent run. The recycled
catalysts were used in fresh reaction mixture under the
same oxidation reaction conditions. The experiment
showed that all solid catalysts were reused for four times,
and no significant change was observed in catalytic activity
and pattern selectivity of products. The leaching of the
metal complexes from the solid support into the reaction
medium was also checked. The absence of any absorption
peaks associated with porphyrins in the UV–Vis spectra of
the reaction solution indicated that during the oxidation
reactions, leaching of metalloporphyrins does not take
place.
amount of NaOH and NaF was added into the mixture.
After another 60 min of vigorous stirring at 35 °C, 10.61 g
of CTAB was added to the mixture and the stirring con-
tinued at the same temperature for 60 min. The molar
composition of the final SiO /CTAB/NaOH/H O/NaF
2
2
mixture was 1.0:0.65:0.5:62:0.1. The resulting gel was
transferred into an autoclave and kept at 120 °C for 24 h.
The obtained MCM-48 product was filtered, washed with
distilled water, and dried at 100 °C. The as-synthesized
samples were calcined at 550 °C for 6 h [40].
Synthesis of supported catalysts
Supported metalloporphyrins were achieved by direct
encapsulation. To encapsulate the metalloporphyrins into
the channels of MCM-48, 1 g of mesopore was immersed
3
Conclusion
into 5 cm of dichloromethane and then added to a flask
containing 0.1 g of complexes (MnTClPP, FeTClPP, and
CoTClPP). Then, the system was vigorously stirred by
magnetic stirring for 48 h. Materials were filtered and
exhaustively washed in a Soxhlet system with dichloro-
methane and DMF for 24 h to remove any non-supported
metalloporphyrin. The final products were dried for 24 h at
80 °C.
In summary, we have prepared three novel heterogeneous
catalysts by direct encapsulation of Fe(III), Mn(III), and
Co(II) metalloporphyrins into the channels of mesoporous
MCM-48. The catalytic properties of these catalysts were
studied in the oxidation of cyclohexene with TBHP as
oxygen source. The unique characteristics of the support
have a significant effect on the catalytic efficiencies and
afford some advantages including more resistance to pore
blocking and high catalytic ability and selectivity to the
allylic oxidation products. We anticipate that MCM-48
would be more useful and applicable for porphyrin heter-
ogenization. These features imply that MCM-48 is an
applicable support. The immobilized catalysts can be
reused for four times.
Catalytic oxidation reaction
Oxidation reactions were carried out under reflux condi-
tions at atmospheric pressure. At first, a mixture of
3
cyclohexene (10 mmol), 5 cm acetonitrile, and 0.02 g
heterogeneous catalyst was added to a flask containing a
magnetic stirrer bar. After 5 min, TBHP as oxidant
(15 mmol) was added. The reaction mixture was heated
under stirring at the desired temperature for 6 h. The cat-
alyst was then separated by filtration and the collected
products were detected by GC and GC–MS.
Experimental
All materials were of commercial reagent grade. Pyrrole, p-
chlorobenzaldehyde, propionic acid, methanol, dimethyl-
formamide (DMF), metal chlorides, tetraethylortho silicate
Characterization of the samples
(
TEOS), cetyltrimethylammonium bromide (CTAB),
X-ray diffraction patterns were recorded with a Philips
X’pert MPD using Co Ka radiation. FT-IR spectra were
recorded on a Shimadzu FTIR-8400 spectrophotometer.
Specific surface areas were determined from nitrogen
adsorption at 77 K on an ASAP 2010 apparatus. UV–Vis
diffuse reflectance spectroscopy was performed on a Shi-
madzu 2550 spectrometer. Scanning electron microscopy
images were recorded on a Philips XL30 microscope. The
amount of adsorbed metalloporphyrin in the mesoporous
MCM-48 was determined by means of ICP spectroscopy.
The oxidation products were analyzed with a gas chro-
matograph (Shimadzu) equipped with an HP-5 capillary
column. The reaction products were confirmed by GC–MS
(Perkin-Elmer).
sodium hydroxide (NaOH), sodium fluoride (NaF), dichlo-
romethane, cyclohexene, acetonitrile, and TBHP (70 %
aqueous solution) were purchased from Merck and Aldrich
chemical companies. 5,10,15,20-Tetrakis(4-chlorophenyl)por-
phyrin was synthesized in our laboratory, according to Adler’s
method [38]. The metallation procedure was carried out by the
method described previously [39].
Synthesis of MCM-48
The following procedure was used for preparing of MCM-
4
8: a mixture of 10 g TEOS and 50 g deionized water was
vigorously stirred at 35 °C for 40 min, then the required
1
23

Immobilized metalloporphyrins in mesoporous MCM-48
603
Acknowledgments We are grateful for the financial support from
The Research Council of Iran University Science and Technology
24. Farzaneh F, Poorkhosravani M, Ghandi M (2009) J Mol Catal A
Chem 308:108
(
IUST), Iran.
25. Yang XL, Dai WL, Gao R, Chen H, Li H, Cao Y, Fan K (2005) J
Mol Catal A Chem 241:205
2
2
2
2
6. Rahiman AK, Rajesh K, Bharathi KS, Sreedaran S, Narayanan V
2009) Inorg Chim Acta 362:1491
7. Nur H, Hamid H, Endud S, Hamdan H, Ramli Z (2006) Mater
Chem Phys 96:337
8. Serwicka EM, Poltowicz J, Bahranowski K, Olejniczak Z, Jones
W (2004) Appl Catal A Gen 275:9
9. Poltowicz J, Pamin K, Matachowski L, Serwicka EM, Mokaya R,
Xia Y, Olejniczak Z (2006) Catal Today 114:287
0. Li Z, Xia C-G, Zhang X-M (2002) J Mol Catal A Chem 185:47
1. Chang Z, Krishna RM, Xu J, Koodali R, Kevan L (2001) Phys
Chem Chem Phys 3:1699
(
References
1
2
3
4
5
6
. Arends IWCE, Sheldon RA (2001) Appl Catal A Gen 12:175
. Sheldon RA, Dakka J (1994) Catal Today 19:215
. Centi G, Misono M (1998) Catal Today 41:287
. Dusi M, Mallat T, Baiker A (2000) Catal Rev 42:213
. Meunier B (1992) Chem Rev 92:1411
3
3
. Farzaneh F, Taghavi J, Malakooti R, Ghandi M (2006) J Mol
Catal A Chem 244:252
7
8
9
. KalilurRahiman A, Rajesh K, ShanmugaBharathi K, Sreedaran S,
Narayanan V (2006) Appl Catal A Gen 314:216
. Poltowicz J, Serwicka EM, Bastardo-Gonzalez E, Jones W,
Mokaya R (2001) Appl Catal A Gen 218:211
3
3
2. Russo PA, Carrott MMLR, Carrott PJM (2007) Colloid Surf A
3
10:9
3. Xia Y, Mokaya R (2004) Microporous Mesoporous Matter
4:179
7
. Smith AB, Konopelski JP (1984) J Org Chem 49:4094
3
3
4. Xu J, Luan Z, Hartmann M, Kevan L (1999) Chem Mat 11:2928
5. Huang L, Huang Q, Xiao H, Eic M (2008) Microporous Meso-
porous Matter 114:121
6. Schumacher K, Hohenesche CF, Unger KK, Ulrich R, Chesne
AD, Wiesner U, Spiess HW (1999) Adv Mat 11:1194
7. Zhang JL, Liu YL, Che CM (2002) Chem Commun 23:2906
8. Adler AD, Longo FR, Finarelli JD, Goldmacher J, Assour J,
Korsakoff L (1967) J Org Chem 32:476
9. Adler AD, Longo FR, Kampas F, Kim J (1970) J Inorg Nucl
Chem 32:2443
0. Shao Y, Wang L, Zhang J, Anpo M (2005) Microporous Meso-
porous Mater 86:314
1
1
1
1
0. Sakthivel A, Dapurkar SE, Selvam P (2003) Appl Catal A Gen
46:283
1. Yin C, Yang Z, Li B, Zhang F, Wang J, Ou E (2009) Catal Lett
31:440
2. Moreira MSM, Martins PR, Curi RB, Nascimento OR, Iamamoto
Y (2005) J Mol Catal A Chem 233:73
3. KalilurRahiman A, ShanmugaBharathi K, Sreedaran S, Naraya-
nan V (2009) Catal Lett 127:175
4. Mansuy D (1990) Pure Appl Chem 62:741
5. Doro FG, Smith JRL, Ferreira AG, Assis MD (2000) J Mol Catal
A Chem 164:97
6. Liu CJ, Yu WY, Li SG, Che CM (1998) J Org Chem 63:7364
7. Nenoff TM, Showalter MC, Salaz KA (1997) J Mol Catal A
Chem 121:123
8. Benedito FL, Nakagaki S, Saczk AA, Peralta-Zamora PG, Costa
CMM (2003) Appl Catal A Gen 250:1
9. Kresge CT, Leonowicz ME, Roth WJ, Vartuli JC, Beck JS (1992)
Nature 359:710
0. Beck JS, Vartuli JC, Roth WJ, Leonowicz ME, Kresge CT,
Schmitt KD, Chu CTW, Olson DH, Sheppard EW, McCullen SB
2
3
1
3
3
3
4
4
4
4
1
1
1
1
1. Costa AA, Ghesti GF, de Macedo JL, Braga VS, Santos MM,
Dias JA, Dias SCL (2008) J Mol Catal A Chem 282:149
2. Fu B, Yu HC, Huang JW, Zhao P, Ji LN (2008) Transit Met
Chem 33:803
1
1
2
3. Liu C-J, Li S-G, Pang W-Q, Che C-M (1997) Chem Commun
1
:65
4
4
4. Zhang L, Sun T, Ying J (1999) Chem Commun 12:1103
5. Schunemann V, Trautwein AX, Rietjens IMCM, Boersma MG,
Veeger C, Mandon D, Weiss R, Bahl K, Colapietro C, Piech M
(1992) J Am Chem Soc 114:10834
(
1999) Inorg Chem 38:4901
2
2
1. Corma A (1997) Chem Rev 97:2373
2. Linssen T, Cassiers K, Cool P, Vansant EF (2003) Adv Colloid
Interface 103:121
4
6. Serwicka EM, Mokaya R, Poltowicz J, Jones W (2002) Chem
Phys Chem 3:892
2
3. Branton PJ, Hall PG, Sing KSW (1993) J Chem Soc Chem
Commun 16:1257
123