| According to the conventional hydrodesulfurization(HDS),some refractory sulfur compounds,such as benzothiophene(BT), dibenzothiophene(DBT) and their derivatives are difficult to be removed due to their steric hindrance.Currently,non-hydrodesulfurization desulfurization techniques have attracted lots of attentions.Oxidative desulfurization combined with extraction is considered as one of the most promising processes due to short reaction time and moderate conditions. The room temperature ionic liquids(RTILs) are considered as "green solvents",and environment-friendly solvents,which can avoid the environmental and safety concerns because of nonvolatile,nonflammable, and thermally stable.This thesis focuses on the researches of extraction-catalytic oxidation desulfurization system to challenge the deep desulfurization of fuels.ILs are used as extractants and solvents while 30%H2O2 is used as oxidant,and peroxopolyoxometalates are used as catalysts for deep desulfurization of fuels.By this desulfurization system BT,DBT and 4,6-DMDBT can be effectively catalytic oxidation.Based on the predecessors research,three peroxophosphomolybdates are prepared,such as[(C4H9)4N]3{PO4[MoO(O2)2]4},[C14H29N(CH3)3]3-{PO4[MoO(O2)2]4},[C16H33NC5H5]3{PO4[MoO(O2)2]4},and three peroxophosphotungstates are prepared,such as[(C4H9)4N]3{PO4-[WO(O2)2]4},[C14H29N(CH3)3]3{PO4[WO(O2)2]4},[C16H33N(CH3)3]3-{PO4[WO(O2)2]4},and they all have been characterized by elemental synthesis,chemistry titration,TG-DTA,TG-DTA,FT-IR and UV-Vis to determine the composition and structure;DBT as the substrate,we investigated the activities of four desulfurization systems containing "IL", "IL-H2O2","catalyst-H2O2" and "IL-catalyst-H2O2";To study the influence of various parameters such as different ILs,substrates,reaction time,reaction temperature,the amount of oxidizing agent,the times of the recycle of IL and so on.In ECODS system,the catalyst with short alkyl chain exhibited higher catalytic activity than that with long alkyl chain due to steric hindrance of long alkyl chain of the catalytic active species became an obstacle for the approach of the sulfur atom to the catalytic active species in IL;peroxophosphotungstates exhibited higher catalytic activity than peroxophosphomolybdates;[(C4H9)4N]3{PO4[WO(O2)2]4} exhibited higher catalytic activity than[(C4H9)4N]3{PO4[MoO(O2)2]4};when using [(C4H9)4N]3{PO4[WO(O2)2]4} as the catalyst,the sulfur removal could reach 98.1%for 3 h,when using[(C4H9)4N]3{PO4[MoO(O2)2]4} as the catalyst,the sulfur removal could reach 97.3%for 3 h.Moreover,the mechanism of the extraction-catalytic oxidation desulfurization(ECODS) system has been analyzed. By different experiment,the best reaction conditions were found, [n(H2O2)/n(DBT)/n(Catalyst)=200:100:1],reaction time was 70℃, reaction temperature was 3 h,the dosage of[bmim]BF4 was 1 mL. Morever,we found that the ECODS system could be recycled five times with slight decrease in activity. |
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