| In the last decade,much attention has been paid to the deep desulfurization of fuel oils due to more stringent environmental regulations, which require to produce and use the environment friendly low-sulfur content fuel product. At present, diesel oil plays a more and more important role in the various kinds of fuel. But compare to gasoline, diesel oil has a high rate of sulfur compound. The sulfur compound is existed mainly as benzothiophene, dibenzothiophene and their ramification. These kinds of sulfur compounds are not easy to remove by adding hydrogenation. That's why diesel oil has a high rate of sulfur compound. So many states have been studying the new desulfurization technology for diesel oil. Oxidation desulfurization of non-hydrodesulfurization become a hot spot of research.In this paper, a novel oxidation-extraction desulfurization of sulfur-containing compounds in amphiphilic phase-transfer catalytic oxidative system was studied. The oxidation of sulfur-containing compounds present in model light oil and two kinds of FCC diesel oil with 3440 Sμg/g and 1442 Sμg/g was conducted in catalytic oxidative system composed of diesel oil, 30 wt% hydrogen peroxide, and an amphiphilic catalyst [(C16H33)N+(CH3)3]3[PW12O40]? under mild conditions, then the oxidation products of sulfur-containing compounds were extracted by polar solvent after oxidizing diesel.In this system of oxidation desulfurization for model light oil, the results indicate that the catalyst synthesized by cetyltrimethylammonium bromide and phosphortungstic acid displays better catalytic activity for model sulfur -containing compounds (Th,BT,DBT) than the one synthesized by dodecyltrimethylammonium bromide and phosphortungstic acid. The catalytic oxidation reactivity of sulfurl-containing compounds was found to be in the following order:DBT> BT >Th. Under the oxidation reaction condition with the amount of amphiphilic catalyst 0.24% wt, the amount of hydrogen peroxide [H2O2]/[S]=3.5 (molar ratio), reaction temperature 50℃,reaction time 30min, the stirring rate 1000rpm,the sulfur removal efficiency of DBT was 99.8% after extracted by NMP (solvent /oil =1:1,by volume) for one time at ambient temperature.The results on catalytic-oxidation/extraction desulfurization of the high sulfur contenting FCC diesel oil indicated that: [(C16H33)N+(CH3)3]3[PW12O40] displayed the higher catalytic activity compared to [N+(C4H7)4]3[PW12O40], the sulfur removal efficiency of H-oil was higher 20%. Oxidative activity of water-soluble hydrogen peroxide for the sulfur compounds in H- oil was better than that of oil-soluble tert-butyl hydroperoxide in amphiphilic catalytic oxidative system, the sulfur removal efficiency of. H-oil oxidized by which was better 11% than the latter. The orthogonal experiment of catalytic oxidative method was adopted to remove the sulfur compounds in H- oil by using hydrogen peroxide as oxidant, self-synthsized amphiphilic phase transfer catalyst as catalyst, and NMP as extraction agent respectively. Based on the table of orthogonal experiment, the sequence of the factors of the catalytic oxidation reaction showed that, the influence order to the sulfur removal efficiency is reaction temperature, the mass percent content of catalyst, the reaction time, the molar ratio of hydrogen peroxide and S. The sulfur removal efficiency increases as the hydrogen peroxide solution amount enhances, and then reduce a little; Extension of reaction time was advantageous to sulfur removal efficiency, when the sulfur removal efficiency reached to the highest, increasing the reaction time was not propitious to increase it; Enhancement of the oxidized temperature was advantageous to reaction activity; The sulfur removal efficiency increased along with the catalyst amount used enhanced. Extracting agent was remarkable to the H-Oil desulfurization effect, the sulfur removal efficiency decreased in the order: NMP>DMF> methyl cyanide >methyl alcohol, but the yield of the oil decreased in the order: methyl cyanide> NMP>DMF= methyl alcohol; The sulfur content of H-Oil can be increased as extracted by DMSO, and ethanol can dissolve into H-Oil.The removal performance of sulfur-containing compounds in L-Oil was evaluated. The [(C16H33)N+(CH3)3]3[PW12O40] performed stronger catalytic activity on the desulfurization than [N+(C4H7)4]3 [PW12O40]?, formic acid and acetic acid. The amphiphilic catalytic oxidative system displayed the better catalytic oxidative activity, and the sulfur removal efficiency increased as following the formic acid adding, but the acetic acid can not improve the oxidative ability of this system. The sulfur removal efficiency increased as the hydrogen peroxide solution amount enhances, and reached to the highest when [H2O2]/[S] is 5. Extension of reaction time was advantageous to sulfur removal efficiency, the color of L-Oil become darker as increasing reaction time; Enhancement of the oxidized temperature was advantageous to reaction activity, the sulfur removal efficiency reduced a little when the oxidized temperature was over 70℃; The sulfur removal efficiency increased along with the catalyst amount used enhances; The stirring rate was at 1000rpm, the sulfur removal efficiency was 93.8%, the biggest. On the contrary, the catalytic activity of amphiphilic catalyst was reduced, and the stability of emulsion was too best to demulsify, when the equivalent weight of span60 and amphiphilic catalyst as the surfactant was added into the catalytic oxidation system. The recycled amphiphilic catalyst demonstrated the same as high catalytic activity as the fresh amphiphilic catalyst, its FT-IR analysis result indicated that this catalyst the structure does not change around the catalyzed oxidation.Its catalyic oxidation conditions were as follows : reaction temperature 60℃, reaction time 90min, the amount of hydrogen peroxide [H2O2]/[S]=5(molar ratio),the amount of amphiphilic catalyst 0.232% wt, the stirring rate 1000rpm, the result of extraction indicated that: Extracting agent was remarkable to the L-Oil desulfurization effect, the sulfur removal efficiency decreased in the order: NMP>DMF>γ-butyrolactone>acetonitrile>acetonitrile/water azeotropic mixture>diethylene glycol> methyl alcohol, but the yield of the oil decreased in the order: diethylene glycol> acetonitrile/water azeotropic mixture > acetonitrile >γ-butyrolactone= methylalcohol> NMP>DMF. The water can improved the yield of L-Oil in the extraction system. The amount of water in extractant increased, the yield of L-Oil increased, but the sulfur removal efficiency reduced. The sulfur removal efficiency increased along with the extracting agent amount used enhanced, by contrary the yield reduced. The sulfur removal efficiency increased, and the yield reduced following the increasing the extract times. The change of extracting agent amount and the extract times were unable simultaneously to guarantee the high sulfur removal efficiency and yield. The best extraction condition of NMP was: the volume ratio of NMP is 90%, extraction time 5min, room temperature, hold for 15min, the volume ratio of agent to of oil is 1:4, extracted for four time, the sulfur removal efficiency and yield of L-Oil were 84.1%,90%, respectively. The best extraction condition ofγ-butyrolactone was: extraction time 5min, room temperature, hold for 15min, the volume ratio of agent to oil is 1:2, extracted for one time, the sulfur removal efficiency and yield of L-Oil were 82.2%, 86% , respectively. The used extractants were distilled to recycle at atmospheric pressure. The sulfur removal efficiency were ruduced 4.5% and 3.7%, respectively after extracted by the recycled NMP andγ-butyrolactone, but the yields of L-Oil were enhanced compared to the fresh extractants.The GC-FPD chormatograph and IR Spectrogram of L-Oil after oxidation-extraction showed that the sulfur-containing compounds in L-Oil were oxidized to their corresponding sulfones, and then were extracted to remove by polar solvent in the amphiphilic catalytic oxidative system.
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