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S. Rostamnia et al. / Journal of Molecular Liquids 207 (2015) 334–337
Fig. 8. Study of catalyst recyclability related to SBA-15/TFE in 10 runs.
Fig. 6. Optimizing the amount of SBA-15 in the model reaction.
not affected by this small distortion recyclability of the catalyst is still re-
inforced. SEM and TEM images of the catalyst indicate its mesostructure
and surface morphology which demonstrate the structure of SBA-15/
TFE (Fig. 3).
2.2. General procedure for the oxidation of sulfides to sulfoxides
In a round-bottomed flask (25 mL) equipped with a magnetic stirrer,
sulfide (1 mmol) was added to a reaction flask in the presence of
4 mmol H2O2 (30%) and 0.02 g SBA-15 in 3 mL TFE and stirred at
room temperature for an appropriate time (Table 1). After completion
of the reaction, TFE was separated from reaction mixture at 80 °C and
reused for the next reactions. Then, the product was extracted from re-
action mixture with chloroform and then the final product was obtained
by evaporating chloroform from sulfoxide (Fig. 4).
Fig. 7. Catalytic comparison of SBA-15 and TFE and their combined mode. Reaction
conditions: .0.02 g SBA-15 in columns 1 and 2, 3 mL TFE in columns 2 and 3, 1 mmol
methyl(phenyl)sulfide, and 4 mmol H2O2 (30%) at room temperature for 35 min.
3. Results and discussion
When TFE was confined into the pores of SBA-15, a remarkable
change happens in the FT-IR spectrum of SBA-15 away from related
bands of own TFE. According to this observation, a remarkable interac-
tion between TFE and SBA-15 is predictable (Fig. 1). Moreover, the con-
finement of TFE inside the pores of SBA-15 caused the removal of
adsorbed water in SBA-15. Adsorbed water on the surface of SBA-15
can deactivate the silanols on the surface of SBA-15 and reduce the
mass transfer to organic components [9]. On the other hand, TFE is in-
trinsically active and has unique nature among its corresponding non-
fluorinated alcohols. We compared methanol, ethanol, and TFE under
the similar conditions in the oxidation of sulfide. First, the oxidation of
phenyl methyl sulfide 1a to corresponding sulfoxide 2a and sulfone 3a
was selected as a model system (Fig. 5). Results presented in Fig. 4 verify
the potency of SBA-15/TFE in the selective oxidation reaction of sulfide
1a to sulfoxide 2a.
(120 g). Then, tetraethyl orthosilicate (TEOS, 9 g) was added to mixture,
which was stirred for 8 h at 40 °C. The resulting mixture was transferred
into a Teflon-lined stainless steel autoclave and kept at 100 °C for 20 h.
After cooling, to room temperature, the product was filtered, washed
with water and dried overnight at 70 °C in air. The sample was then
raised to a temperature of 500 °C in the rate of 2 °C/min to remove the
template by calcination method.
Analysis of FT-IR spectra revealed the related functionalities in SBA-
15. Accordingly, the bands from 807 to 1100 cm−1 are assigned to the
vibrations of (Si\\O\\Si) bond, and the band at about 960 cm−1 is
assigned of (Si\\OH) bond and the SiO\\H groups appeared by the
very broad IR absorption band in the 3100–3600 cm−1 region (Fig. 2).
Diffraction peaks at below 28 corresponding to the (100), (110), and
(200) are readily recognized from the XRD pattern of SBA-15 (Fig. 2).
The observed diffraction peaks agree with the 2D-hexagonal SBA-15.
The stability and integrity of the SBA-15/TFE under the reaction condi-
tions and after reuse were also investigated. The XRD patterns of both
the fresh and reused catalysts (Fig. 3a and b) indicate that just a small
change occurred for SBA-15 in its mesoscopic structure during the reac-
tion and the recycling stages. Fortunately, the progress of reaction that is
The amount of SBA-15 was also optimized for the model oxidation
reaction. Based on this study, the convenient and best amount of SBA-
15/TFE for this work was 0.02 mmol for each mmol of sulfide. Fig. 6
represents the results for six different amounts of SBA-15/TFE which
was performed under the similar conditions.
To find out the effect of combined SBA-15/TFE on the catalysis, both
of SBA-15 and TFE were studied separately and compared by its
Scheme 1. Chemoselectivity between benzylic and aromatic sulfide oxidation.