E. Rafiee, F. Mirnezami / Journal of Molecular Liquids xxx (2014) xxx–xxx
5
Scheme 2. PhPyBs-PW-catalyzed ECOD of model oil in the presence of H2O2.
260 compared with the other solvents. In order to optimize the reaction con-
261 ditions, dibenzyl sulfide (as a solid sulfide) was selected as model sub-
262 strate. The corresponding sulfoxide could be obtained in excellent
263 yield in the presence of 80 mg of PhPyBs-PW as catalyst and 2:1 H2O2:
264 sulfide ratio with trace over-oxidation product (Table 1, entries 8–11).
sulfoxidation reactions. As can be seen, PhPyBs-PW catalyst shows con- 296
siderable activity with unique thermoregulated phase-separable behav- 297
ior in comparison with the others.
298
4. Conclusion
299
265
In order to generalize the scope of the reaction, a series of structur-
266 ally diverse sulfides (aryl, benzylic, linear and heterocyclic sulfides)
267 was subjected to oxidation under the optimized reaction conditions in
268 the presence of PhPyBs-PW as the best catalyst (Table 2). The sulfoxides
269 were obtained in short reaction times and in excellent yields. Since, this
270 oxidation reaction was generally considered to proceed via an electro-
271 philic addition reaction of oxygen atoms, the sulfides with higher elec-
272 tron density on the sulfur atom should react easily [46].
We report successful preparations of POM-IL salts by combining 300
sulfonate functionalized cations with Keggin-structured POM. A new 301
approach to the oxidation of sulfur-containing compounds was devel- 302
oped using the prepared POM-IL salts as catalyst. Various kinds of sul- 303
fides were successfully oxidized to their corresponding sulfoxides in a 304
relatively good time. Also, the extractive and catalytic oxidation desul- 305
furization of a synthetic mixture of model oil composed of sulfur- 306
containing compounds and n-hexane was carried out with H2O2 as an 307
oxidizing agent using these POM-IL salts as catalyst. It was found that 308
PhPyBs-PW acted as homogeneous catalyst at the reaction temperature, 309
and upon the cooling down of the reacted mixture, it resumed the solid 310
state that can be easily recovered and reused. This procedure offers sev- 311
eral major advantages: (1) the use of a chemically stabile catalyst; 312
(2) highly efficient for the selective oxidation of structurally diverse sul- 313
fides in good to high yields; and (3) the avoidance of the usage of any 314
273
The regenerability and reusability of a catalyst system are very im-
274 portant for a catalytic reaction. Activity of the reused catalyst was inves-
275 tigated through the oxidation reaction of dibenzyl sulfide in the
276 presence of PhPySu-PW as catalyst (Fig. 3). Recovery of the catalyst
277 was very convenient. After each run, the reaction mixture was cooled;
278 catalyst appeared at the bottom of the reactor as solid and could be re-
279 covered by decantation (or filtration). There was no significant decrease
280 in yield after five subsequent reactions. After five cycles, the catalyst was
281 weighed, a loss of 20 wt.% of the catalyst (compared with the amount of
282 the catalyst at the first run) was found. These results indicate that the
283 catalyst shows no significant change in its activity and only a trace de-
284 clining in the yield.
addictive.
315
Acknowledgments
316
285
Based on the above results, the catalytic system was used to ECOD of
The authors thank the Razi University Research Council for the sup- 3Q147
286 model oil containing DBT (500 ppm), MPS (250 ppm) and thiophene
287 (250 ppm) in 5 mL of n-hexane with the total sulfur concentration of
288 1000 ppm (Scheme 2). The sulfur in model oil was reduced from
289 1000 ppm to 10 ppm (90%). In order to investigate the desulfurization
290 efficiency of the catalyst, the catalytic system was used to ECOD of
291 model oil with low concentration of DBT (100 ppm level) in n-hexane.
292 The sulfur level was lowered from 100 ppm to 25 ppm after ECOD
293 process.
port of this work.
318
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t3:2
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Comparison of the reaction data with other reported methods.
t3:3
Substrate
Catalyst
Reaction conditions
Yield (%)
PhPyBs-PW
H2O2, H2O, r.t., 2 min
95
t3:4
t3:5
CinH3PMo12O40 H2O2/urea, EtOH, r.t., 2 h
PyH3PMo11VO40 H2O2, CH3CN, r.t., 3 h
95
[47]
[48]
100
t3:6
t3:7
t3:8
t3:9
(2009) 1955–1960.
341
342
343
344
345
346
PhPyBs-PW
H2O2, H2O/EtOH, 60 °C, 10 min
98
97
94
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CinH3PMo12O40 H2O2/urea, EtOH, r.t., 2 h
PyH3PMo11VO40 H2O2, CH3CN, r.t., 30 min
[47]
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