| > 90 %Spectr. |
With sodium; 1,1,2,2-tetraphenylethylene In tetrahydrofuran at 20℃; for 14.5h; Inert atmosphere; regioselective reaction; |
4.3. Reductive desulfurization procedure
General procedure: Deep red suspensions of Na, Li or Na and Li metals in the presence of a catalytic amount of TPE (Na/TPE, Li/TPE or Na/Li/TPE; for the relative molar ratios, see Table 1) were prepared by vigorously stirring the freshly cut metal in dry THF (10 mL) during 1 h at rt. To this mixture, a solution of the appropriate dibenzothiophene, 1, (2 mmol) dissolved in dry THF (5 mL) was added dropwise within 30 min. The reaction mixture was vigorously stirred at rt during 14 h, after which time it was quenched by slow dropwise addition of H2O (15 mL). The organic solvent was evaporated in vacuo and the resulting mixture was extracted with Et2O or AcOEt (3×10 mL) and the organic phases were collected, washed with H2O (10 mL), brine (10 mL), and dried (Na2SO4). After evaporation of the solvent, the resulting mixtures were analyzed by GC/MS, and the reaction products 2a,26 2b,26 2c,27 2d28 and 2e29 were characterized by 1H, 13C NMR and IR spectroscopies, and by comparison with literature data. |
|
With dihydrogen peroxide; 3-butyl-1-methyl-1H-imidazol-3-ium hexafluorophosphate In octane; water at 70℃; for 0.166667h; |
2.8. Extractive and catalytic oxidative desulfurization processes (ECODS)
General procedure: The ECODS studies were performed using a model diesel containingthe most refractory sulfur-compounds present in real diesel,namely: 1-benzothiophene (1-BT), dibenzothiophene (DBT),4-methyldibenzothiophene (4-MDBT) and 4,6- dimethyldibenzothiophene(4,6-DMDBT). All the experiments were carried outunder air (atmospheric pressure) in a closed borosilicate 5 mL reactionvessel, equipped with a magnetic stirrer and immersed in athermostatically controlled liquid paraffin bath at 70 °C. The catalyticoxidative step was performed in the presence of a polarextraction solvent, immiscible with the model diesel phase withequal volume of model diesel and extraction solvent. The ionic liquid(IL), 1butyl3methylimidazolium hexafluorophosphate(BMIMPF6) and acetonitrile (MeCN) were used as extraction solvents.These solvents acted as extraction solvents of sulfur compoundsand also as an oxidative reaction medium. The oxidationof the sulfur compounds only occurred in the presence of a catalystand an oxidant, where H2O2 (aq. 30%) was used. [BPy]3[PMo12O40]and [BMIM]3[PMo12O40] dissolved in MeCN, but showed to beinsoluble in ionic liquid solvent. In all ECODS systems 3 lmol ofeach compound was used. The heterogeneous catalyst PMo12O40(at)PPy-MSN was also studied, using 120 mg that contains 3 lmol of[PMo12O40]3- active center. In a typical experiment, 0.75 mL ofmodel diesel (containing a total sulfur concentration of2350 ppm in n-octane) and 0.75 mL of [BMIM][PF6] were addedto the catalyst. An initial extraction of sulfur compounds frommodel diesel to the IL phase occurred by only stirring the bothimmiscible phase for 10 min at 70 °C. The catalytic step of the processis then initiated by the addition of H2O2 (75 lL, 0.64 mmol).The sulfur content in the model diesel phase was periodicallyquantified by GC analysis using tetradecane as standard. Usingthe heterogeneous catalyst, recycle experiments were performedby adding a new portions of model diesel, oxidant and [BMIM][PF6] extraction solvent, at the end of each ECODS cycle. The solidcatalyst was not washed between cycles. After three cycles, thesolid was isolated from the ECODS process, followed by washingand dry to be characterized after catalytic use. |
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