Catalytic oxidation of aryl alkyl sulfides using immobilized vanadyl ions within nanoreactors of Al-MCM-41

Article abstract of DOI:10.1016/S1872-2067(10)60114-3

VOSO₄ immobilized within nanoreactors of Al-MCM-41 (VO ²⁺/Al-MCM-41) was synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption, and chemical analysis techniques. The prepared VO²⁺/Al-MCM-41 successfully catalyzes the oxidation of aryl alkyl sulfides and up to 99 conversion and 90 selectivity for the corresponding sulfoxides were obtained with H₂O₂ as oxidant in acetonitrile at room temperature in 30 min.

Full text of DOI:10.1016/S1872-2067(10)60114-3

CHINESE JOURNAL OF CATALYSIS
Volume 31, Issue 10, 2010
Online English edition of the Chinese language journal
RESEARCH PAPER
Cite this article as: Chin J Catal, 2010, 31: 1217–1220.
Catalytic Oxidation of Aryl Alkyl Sulfides Using Immobilized
Vanadyl Ions within Nanoreactors of Al-MCM-41
Zamanifar ELHAM, Farzaneh FAEZEH*
Department of Chemistry, University of Alzahra, P.O.Box, 1993891176, Vanak, Tehran, Iran
Abstract: VOSO4 immobilized within nanoreactors of Al-MCM-41 (VO2+/Al-MCM-41) was synthesized and characterized by X-ray dif-
fraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption, and chemical analysis techniques. The prepared
VO2+/Al-MCM-41 successfully catalyzes the oxidation of aryl alkyl sulfides and up to 99% conversion and 90% selectivity for the corre-
sponding sulfoxides were obtained with H2O2 as oxidant in acetonitrile at room temperature in 30 min.
Key words: Al-MCM-4; vanadyl ion; hydrogen peroxide; sulfoxidation
Organic sulfoxides are useful synthetic intermediates for the
preparation of various chemically and biologically active
molecules [1,2]. The study of the oxidation of sulfides to sul-
foxides with different methodology is an interesting subject. In
general, sulfoxides are obtained by the partial oxidation of
sulfides with oxidants such as tert-butyl hydroperoxide or H2O2
[3]. These oxidants are relatively weak and need to be activated
by the addition of transition metal ions to produce reactive
peroxo species [2–4]. Therefore, many catalytic sulfoxidation
reactions have been carried out in the liquid phase in the
presence of soluble Ti, Mn, Cr, Re, W, or V complexes [2,5–8].
In recent years, the chemistry of vanadium complexes has
attracted considerable attention because of their potential ap-
plication as catalysts for the oxidation of various organic sul-
fides [2,9–10]. Easier and more environmentally benign proc-
esses can be obtained by heterogenizing the homogeneous
catalysts. Several supported metals such as vanadium com-
pounds on TiO2 [11], mesoporous silica [12], USY zeolites
[13,14], VOx/Al2O3 or VOx/SiO2 [15], and VO(acac)2 ex-
changed sulfonic acid resin have been used in sulfoxidation
reactions [16].
1.1 Immobilization of VOSO4 within Al-MCM-41
VOSO4 (0.2 g) in ethanol (10 ml) was added to Al-MCM-41
(1.0 g, synthesized as reported previously [17]) in ethanol (10
ml). The resultant mixture was refluxed for 8 h. The mixture
was then filtered and washed with hot ethanol. The percentage
of vanadium was determined to be 1.660% by ICP.
1.2 General procedure of oxidation of aryl alkyl sulfide
Typically, a mixture of 0.05 g of VO2+/Al-MCM-41 catalyst
and 20 mmol of substrate in 10 ml of acetonitrile was slowly
stirred in a round bottom flask. H2O2 (30% aqueous solution,
24 mmol) was then added to the reaction mixture after a few
minutes and further stirred at room temperature. The solid was
then filtered and washed with fresh solvent. The filtrate was
analyzed by GC and GC-MS.
1.3 Characterization of the catalyst
Fourier transform infrared spectroscopy (FT-IR) spectra
were recorded on a Bruker Tensor 27 FT-IR spectrometer.
Electronic spectra for the solid catalysts were recorded in Nujol
on a Perkin Elmer Lambada 35 UV-Vis spectrophotometer. The
products were analyzed by GC and GC-MS using an Agilent
6890 Series instrument with an FID detector, a HP-5, 5%
In this study, we attempted to use VO2+/Al-MCM-41 as a
stable catalyst for the sulfoxidation of aryl and alkyl sulfides.
1 Experimental
Received date: 26 March 2010.
*Corresponding author. Tel: +98-21-88258977; Fax: +98-21- 66455291; E-mail: faezeh_farzaneh@yahoo.com; farzaneh@alzahra.ac.ir
Foundation item: Supported by the Research Council of the University of Alzahra, Iran.
Copyright © 2010, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(10)60114-3

Zamanifar ELHAM et al. / Chinese Journal of Catalysis, 2010, 31: 1217–1220
phenylmethylsiloxane capillary, and an Agilent 5973 Network
system, a mass selective detector and a HP-5 MS 6989 Net-
work GC system. X-ray powder diffraction (XRD) data were
recorded on a Seifert XRD 3003 PTS diffractometer with Cu
Kα1 radiation (λ = 0.154 nm). Nitrogen adsorption studies were
performed at liquid nitrogen temperature using a Quanta
chrome Nova 2200, version 7.11 analyzer. Chemical analysis
of the samples was carried out using the ICP technique.
(1)
(2)
2 Results and discussion
1
2
3
4
5
6
7
2θ/(o )
Fig. 1. XRD patterns of calcined Al-MCM-41 (1) and VO2+/MCM-41
2.1 Characterization of the catalyst
(2).
Al-MCM-41 was prepared according to the procedure de-
scribed previously. Figure 1 shows the XRD pattern of calcined
Al-MCM-41. As shown, it has one strong and two weak peaks.
All three XRD reflections can be indexed on a hexagonal lat-
tice. The XRD of the calcined Al-MCM-41 is completely con-
sistent with that of the spectrum for Al-MCM-41 [17]. The
decrease in the VO2+/Al-MCM-41 XRD peak intensities and
the decrease in the d value from 3.878 to 3.803 nm is an indi-
cation of the Al-MCM-41 pore surface silanol groups reacting
with vanadyl ions (Fig. 1 and Table 1).
600
(a)
500
400
300
200
600
(b)
500
400
300
200
600
The N2 adsorption-desorption isotherms of Al-MCM-41,
VO2+/Al-MCM-41, and used VO2+/Al-MCM-41 are shown in
Fig. 2. The type IV isotherms [18] indicate that at low relative
pressures p/p0, adsorption take place as thin layers on the walls
(monolayer coverage). In addition, the height of the inflection
in the nitrogen adsorption isotherm plots for VO2+/
Al-MCM-41 is smaller than that of Al-MCM-41. This is at-
tributed to the reduction in pore volume from 1.074 0 to
0.973 5 cm3/g, which indicates a decrease in the surface area
(Table 1). This effect can be attributed to the inclusion of va-
nadyl ions in the Al-MCM-41 pores. A surface area and pore
volume of 1 095 m2/g and 0.514 8 cm3/g, respectively, were
obtained by N2 adsorption-desorption isotherms (Fig. 2(c)) and
reveals that the used catalyst is stable. The small decrease in
these parameters might be because of the adsorption of some
water and solvent molecules.
(c)
500
400
300
200
0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (p/p0)
Fig. 2. Nitrogen adsorption-desorption isotherms of Al-MCM-41 (a),
VO2+/Al-MCM-41 (b), and VO2+/Al-MCM-41 after the reaction (c).
The adsorption bands at 1 080–1 100 and 1 200–1 223 cm–1 are
because of the asymmetric stretching vibrations of Si-O-Si
bridges, and the band at 950–980 cm–1 arises from Si-O-Al
vibrations, V-O-Si symmetric vibrations [16,19] and V=O
stretching modes.
The FT-IR spectra of Al-MCM-41 and VO2+/Al-MCM-41
are shown in Table 2. The broad bands around 3 422 cm–1 are
attributed to surface silanols and adsorbed water molecules.
2.2 Catalytic activity studies
The oxidation of methyl phenyl sulfide as a representative
Table 1 Texture parameters of samples taken from XRD and nitrogen adsorption studies
Catalyst
XRD d value (nm)
3.878
Lattice parameter (nm) BET surface area (m2/g)
Pore volume (cm3/g) Average pore diameter (nm)
Al-MCM-41
VO-Al-MCM-41
4.478
4.391
1455
1202
1.0740
0.9735
1.972
1.950
3.803
Table 2 FT-IR band assignments corresponding to the wavenumbers obtained for Al-MCM-41 and immobilized vanadyl ions within the nanoreactors of
Al-MCM-41
Catalyst
υOH (Si-OH)/cm−1
υas(Si-O-Si)/cm−1
1080, 1223
υas(Si-O-Si)/(Si-O-V)/cm−1
υs(Si-OSi)/cm−1
Al-MCM-41
VO-Al-MCM-41
3422
3424
960
968
802
805
1091, 1223

Zamanifar ELHAM et al. / Chinese Journal of Catalysis, 2010, 31: 1217–1220
Table 4 Oxidation of aryl alkyl sulfides with H2O2 in the presence of
Table 3 Effect of time on the oxidation of phenyl methyl sulfide in
acetonitrile in the presence of VO2+/Al-MCM-41
VO2+/Al-MCM-41
S
O
S
O
Sulfoxide
selectivity
(%)
Sulfone
selectivity
(%)
H2O2
Conversion
(%)
CH3
S
CH3
TONa
+
VO2+/Al-MCM-41
Substrate
CH3
O
Time
(min)
10
Conversion
Sulfoxide
Sulfone
Entry
(%)
58
75
87
66
87
14
selectivity (%)
selectivity (%)
S
87
4
85
84
15
16
—
34
1088
1025
50
1
48
56
85
80
84
59
52
45
15
20
16
41
2
20
3
4a
30
S
30
84b
98
100
66
5
6b
60
S
30
S
Reaction conditions: catalyst 0.05 g, substrate 20 mmol, H2O2 24 mmol,
room temperature. aCatalyst 0.10 g. bA blank reaction.
1225
S
S
S
S
≈99
95c
20d
10e
90
90
10
10
—
—
1238
—
substrate with 30% aqueous H2O2 was carried out using
VO2+/Al-MCM-41 as a catalyst. To obtain the optimum reac-
tion time, the oxidation reactions were carried out over dif-
ferent times. The results are presented in Table 3. As seen in
Table 3, about 87% of the methyl phenyl sulfide was converted
into sulfoxide and sulfone with 85% and 15% selectivities,
respectively, during 30 min of reaction time.
100
100
—
—
Reaction conditions: catalyst 0.05 g, substrate 20 mmol, H2O2 24 mmol,
solvent acetonitrile 10 ml, room temperature, 30 min.
aTON is the mmol of product to mmol of vanadium present in the cata-
lysts. bUnder reflux conditions for 3 h. cUsed catalyst. dIn the presence of
Al-MCM-41 catalyst. eNo catalyst was used.
Furthermore, the use of about 0.05 g catalyst was shown to
give a substrate conversion of 85%. A further increase in the
amount of catalyst by 0.10 g led to a decrease in conversion to
66%. Increasing the amount of catalyst to beyond the optimum
amount increases the available catalyst surface area and thus
creates a suitable medium for the adsorption of guest molecules
(either substrates or products). This in turn may result in a
decrease in the total conversion.
not show any activity when it was subjected to another 30 min
reaction with fresh oxidant and substrate. An ICP determina-
tion of the vanadium catalyst found 1.660% and 1.559% before
and after the reaction, respectively. The vanadium content of
the filtrate solution was found to be below the ICP detection
limit. These results clearly demonstrate the heterogeneous
nature of the sulfoxidation reaction.
A blank reaction under similar conditions with methyl
phenyl sulfide resulted in a 14% conversion with 59% and 41%
selectivity for the sulfoxide and sulfone, respectively. Thus,
running the oxidation reaction in the presence of
VO2+/Al-MCM-41 as a catalyst not only enhances the methyl
phenyl sulfide conversion but also improves its selectivity
toward the formation of sulfoxides.
We propose a mechanism based on the chemistry of per-
oxovanadium as reported previously [10]. The peroxo species
is obtained in situ by the interaction of the catalyst with hy-
drogen peroxide. A subsequent transfer of electrophilic oxygen
from the peroxometal species to the nucleophilic sulfide leads
to the formation of sulfoxide with the eventual regeneration of
the catalyst [20].
We then examined a range of sulfides having various R
groups that were either aromatic or aliphatic and were attached
to the sulfur atom under oxidation conditions. The results are
listed in Table 4. Table 4 reveals that dimethylsulfide with 99%
conversion and diphenyl sulfide with 4% conversion show the
most and the least oxidation reactivity, respectively, at room
temperature but the conversion of diphenyl sulfide increased to
98% under reflux conditions.
The recyclability of VO2+/Al-MCM-41 as a catalyst was
investigated for the dimethylsulfide reaction in a typical ex-
periment where the reaction mixture was filtered and the
catalytic reaction was repeated under similar conditions after
activating the catalyst by washing with acetonitile and drying
at 100 °C. No appreciable loss in catalytic activity was ob-
served and this suggests that the active species is still present in
the Al-MCM-41 nanopores. On the other hand, the filtrate did
Compared with the reported procedures [14,15,21], the use
of VO2+ without using any ligand plus the heterogeneous na-
ture of the catalysis system free of metal ion leaching is the
novelty of our method. The diversity of the sulfide used in this
work and dimethyl sulfide in particular for the synthesis of
dimethyl sulfoxide (DMSO) is of particular importance in this
research.
3 Conclusions
We found that VO2+/Al-MCM-41 promotes the sulfoxida-
tion of methyl phenyl, dimethyl, tollyl methyl, and diphenyl
sulfides towards sulfides and sulfones with ecofriendly oxi-
dants under mild conditions. The reactivity of sulfides toward

Zamanifar ELHAM et al. / Chinese Journal of Catalysis, 2010, 31: 1217–1220
78: 319
sulfoxidation increases by increasing the electron donating
10 Smith T S, Pecoraro V L. Inorg Chem, 2002, 41: 6754
11 Kantam M L, Neelima B, Reddy C V, Chaudhuri M K, Dehury S
K. Catal Lett, 2004, 95: 19
ability of the organic sulfide groups. The sulfoxidation of tol-
lylmethyl and dimethyl sulfide occurred with 98% and 99%
conversion, respectively, and the absence of leaching during
the course of these reactions is of fundamental importance and
should be emphasized.
12 Trukhan N N, Derevyankin A Y, Shmakov A N, Paukshtis E A,
Kholdeeva OA, Romannikov V N. Microporous Mesoporous
Mater, 2001, 44-45: 603
13 Fuerte A, Iglesias M, Sanchez F, Corma A. J Mol Catal A, 2004,
211: 227
References
14 Maurya M R, Chandrakar A K, Chand S. J Mol Catal A, 2007,
278: 12
1
2
Carreno M C. Chem Rev, 1995, 95: 1717
Kaczorowska K, Kolarska Z, Mitka K, Kowalski P. Tetrahedron,
2005, 61: 8315
15 Moussa N, Fraile J M, Ghorbel A, Mayoral J A. J Mol Catal A,
2006, 255: 62
3
Adam W, Malisch W, Roschmann K J, SahaMoller C R, Schenk
W A. J Organomet Chem, 2002, 661: 3
16 Prasanth K L, Maheswaran H. J Mol Catal A, 2007, 268: 45
17 Zanjanchi M A. Asgari S. Solid State Ionics, 2004, 171: 277
18 Lynch J. Physico-Chemical Analysis of Industrial Catalysts.
Paris: Technip, 2001. 7
4
5
6
7
Punniya Murthy T, Rout L. Coord Chem Rev, 2008, 252: 134
Mancka M, Plass W. Inorg Chem Commun, 2007, 10: 677
Maurya M R. Coord Chem Rev, 2003, 237: 163
Ligtenbarg A G J, Hage R, Feringa B L. Coord Chem Rev, 2003,
237: 89
19 Shylesh S, Singh A P. Microporous Mesoporous Mater, 2006, 94:
127
20 Butler A, Clague M J, Meister G E. Chem Rev, 1994, 94: 625
21 Maurya M R, Chandrakar A K, Chand S. J Mol Catal A, 2007,
263: 227
8
9
Bolm C. Coord Chem Rev, 2003, 237: 245
Anisimov A V, Fedorova E V, Lesnugin A Z, Senyavin V M,
Aslanov L A, Rybakov V B, Tarakanova R V. Catal Today, 2003,