【作者】 蒋伟；

【导师】 李华明；

【作者基本信息】 江苏大学 ， 清洁能源与环境保护， 2014， 博士

【摘要】 生产超低硫含量的柴油是目前全世界炼油厂的一个主要任务。由于含硫化物燃烧后会转化为SOx,是环境污染的主要因素之一,因此得到了媒体和科学界的广泛关注。SOx不但会形成酸雨,而且会使汽车催化转换器中的催化剂中毒,降低转化性能,如此势必会增加尾气中CO和NOx的排放,进一步加大环境污染。在过去的几十年里,工业上常用的脱硫方式为加氢脱硫(HDS),该技术可以有效的脱除硫醇、硫醚和噻吩,但对于二苯并噻吩以及它们的烷基衍生物就显得较为困难。氧化脱硫技术可以从一个相反的方向提升燃油脱硫的效果,即将硫化物氧化去除。以氯代季铵盐和无水FeCl3原料合成了三种季铵型类Fenton催化剂Q+[FeCl4]-(Q+=(CH3)4N+,(C14H29)N+(CH3)3,运用红外光谱、紫外光谱、拉曼光谱、元素分析等手段对所合成催化剂的组成和结构进行了表征,同时将这些催化剂应用于模型油的脱硫中。通过考察氧化脱硫反应的时间、温度、萃取剂离子液体的种类、氧化剂和催化剂的用量对脱硫效率的影响,得到了脱硫的最佳条件。结果显示,以离子液体1-丁基-3-甲基咪唑四氟硼酸盐([C4mim]BF4)为溶剂和萃取剂,30wt%双双氧水为氧化剂,30℃下磁力搅拌1h,[(CH3)4N]FeCl4的催化活性最好,模型油中二苯并噻吩(DBT)的脱除率可达到97.0%,并且分批加入双氧水可以提高其利用率。反应结束后,离子液体和催化剂可以通过外加磁场的方法进行分离,然后用水洗即可再生,再生后的催化体系可以循环使用6次。但是该催化剂在憎水性离子液体中的脱硫活性较差,这就限制了类Fenton的应用范围。为了使类Fenton催化剂在憎水性离子液体中也具有较好的脱硫活性。以氯化胆碱和金属盐为原料合成了三种不同金属的类Fenton催化剂,并通过红外光谱、紫外光谱、拉曼光谱、质谱和元素分析对所合成的催化剂进行了表征。实验结果表明,以ChFeCl4为催化剂,温和条件下,在亲水性离子液体[C4mim]BF4中,DBT的脱除率可以达到94.9%,在憎水性离子液体1-辛基-3-甲基四氟硼酸盐([C8mim]BF4)中,DBT的脱除率可以达到97.2%。通过顺磁共振技术(ESR)可以检测出脱硫反应中ChFeCl4和H202所产生的活性氧物种。通过气相色谱质谱联用仪(GC-MS)分析,三种芳香硫化物,DBT、苯并噻吩(BT)、4,6-二甲基二苯并噻吩(4,6-DMDBT)的氧化产物均为其相应的砜类。反应结束后,包含离子液体和催化剂的催化体系可以循环利用5次,且油品的脱硫率没有明显的降低。合成了一类以哌啶盐为阳离子类Fenton催化剂,分别为[C2OHmpip]FeCl4,[C4mpip]FeCl4、[C8mpip]FeCl4和[C12mpip]FeCl4,通过红外光谱、拉曼光谱和质谱对它们的组成和结构进行了表征。实验以[C8mim]BF4为萃取剂,对比它们燃油中硫化物的催化氧化脱除活性可知,[C4mpip]FeCl4具有最高的催化活性,双氧水与硫的摩尔比为3.5,30℃下反应60min, DBT的脱除率即可达到97.1%。实验还考察了不同离子液体作为萃取剂对脱硫效果的影响,UV-vis光谱数据表明,含PF6-阴离子的离子液体由于与DBT的相互作用力较强,导致DBT的脱除率较低。此外,通过GC-MS分析研究了该氧化脱硫反应的过程。双氧水的是一种常用氧化剂,因其副产物仅有水而应用广泛,但高浓度的双氧水在运输过程中有爆炸的危险,而且在使用过程中对操作人员也具有潜在的危害。为了能够利用低浓度双氧水进行燃油中硫化物的氧化脱除,合成了一系列基于有机铁氰酸盐的类Fenton催化剂。实验结果表明,[C4mim]3Fe(CN)6为催化剂,[C4mim]BF4为萃取剂时,燃油的脱硫效果最好,而且研究还发现,低浓度的双氧水更有利于含硫化合物的氧化。当以30wt%双氧水为氧化剂时,模型油的脱除率为76.3%,而使用7.5wt%双氧水为氧化剂时,脱硫率为97.9%。ESR研究结果表明,02·-是氧化脱硫反应中的活性氧物种,GC-MS分析表明,含硫化合物可以被该活性氧物种氧化为相应的砜。经过动力学拟合发现,硫化物的氧化符合准一级动力学方程。合成了[C3H6COOHmim]Cl/xFeCl3(x=0.5,1,1.5,2)四种功能化磁性离子液体,将类Fenton催化剂的催化性能与离子液体的萃取性能集于一体。以吡啶和乙腈为红外探针,测定了它们的酸性,结果表明,[C3H6COOHmim]Cl/2FeCl3既具有Br(?)nsted酸性,也具有Lewis酸性。通过超导量子干涉仪测定了[C3H6COOHmim]Cl/2FeCl3的磁性性能。将该离子液体用于燃油中BT的萃取催化氧化脱除。结果表明,[C3H6COOHmim]Cl/2FeCl3具有最佳的萃取和催化氧化脱硫活性。值得注意的是,BT一直被认为是最顽固的硫化物在该体系中可以100%被脱除,而且反应时间仅需10min。反应结束后,通过外加磁场的方法可以将离子液体和油品进行有效的分离。更多还原

【Abstract】 Production of ultra-low-sulfur diesel has become a major task of refineries all over the world. The presence of sulfur compounds in diesel fuel has shown an adverse impact on the environment and hence it is getting ample attention from the media and scientific community. It is because sulfur-bearing compounds are converted to SOx during the combustion in car engines. This conversion not only results in acid rain, but also high contents of sulfur oxides in exhaust fumes lowers the efficiency of catalytic converters in cars. Sulfur oxides also poison catalysts in catalytic converters used for reducing CO and NOx emissions and this severely affects environment. The hydrodesulfurization (HDS) process has been used for the past several years to eliminate sulfur compounds for industrial purposes. It is efficient for the removal of thiols, sulfides and thiophenes, but less effective in removing the refractory sulfur compounds such as dibenzothiophene and their alkyl derivatives. Sulfur removal by oxidative process aims to promote a reaction in the opposite direction to HDS, i.e. by forming oxidized sulfur species.Three quaternary ammonium Fenton-like materials Q[FeCl4][Q=(CH3)4N, C14H29N(CH3)3, and C18H37N(CH3)3] were synthesized and characterized by IR, UV-vis, Raman spectrum and elemental analysis. Then, they were used as effective catalysts in oxidative desulfurization combining ionic liquids (ILs) extraction and H2O2oxidation. The reaction conditions were optimized by investigating reaction temperature, time, the type of ILs, the amount of H2O2and catalysts in detail. The removal of dibenzothiophene (DBT) in model oil could get up to97.0%at30℃for1h. In addition, the utilization rate of H2O2could be improved by adding it in batches. The catalytic system, consisting of IL and catalysts, could be easily separated by applying an external magnetic field and regenerated by washing with water, which could be recycled for six times with a slight decrease in desulfurization efficiencies. However, the desulfurization efficiency of this catalyst was poor in hydrophobic IL.In order to further enlarge the application field of Fenton-like catalysts, various choline Fenton-like catalysts prepared by choline chloride (ChCl) and metal salts (FeCl3, ZnCl2, SnCl2) were characterized by FT-IR, UV-vis, Raman, ESI-MS and elemental analysis. High desulfurization efficiency of dibenzothiophene (DBT) could be obtained not only in hydrophilic ionic liquid (IL)[C4mim]BF4(94.9%) but also in hydrophobic IL [C8mim]BF4(97.2%) by using ChFeCl4as a catalyst under mild conditions. ESR measurements could give the evidence that the active oxygen species generated by ChFeCl4and H2O2in IL were involved in the catalytic oxidation of DBT. The aromatic sulfur compounds, benzothiophene (BT), DBT, and4,6-dimethyldibenzothiophene (4,6-DMDBT), could be oxidized to the corresponding sulfones, which were detected by GC-MS. Moreover, the catalytic system containing IL and catalyst could be easily separated from oil and could be recycled at least five times without a significant decrease on removal of DBT.A new family of dialkylpiperidinium tetrachloroferrate catalysts, such as [C2OHmpip]FeCl4,[C4mpipJFeCl4,[Csmpip]FeCl4, and [C12mpip]FeCl4, were synthesized and characterized by FT-IR, Raman, and ESI-MS spectra. Their catalytic activities for removal of dibenzothiophene (DBT) in extraction and catalytic oxidative desulfurization system (ECODS) were evaluated under different reaction conditions. Results indicated that the97.1%removal of DBT was obtained with [C4mpip]FeCl4as catalyst in ionic liquid [C8mim]BF4at30℃in60min. The optimal H2O2/sulfur molar ratio was only3.5:1, which suggested that the catalyst was one of the most efficient catalysts reported so far. UV-vis spectra provided an evidence that the lower desulfurization reactivity in PF6--containing ionic liquids was attributed to the strong interaction between ionic liquid and DBT. Through the gas chromatography-mass spectrometer (GC-MS) analysis, dibenzothoiphene sulfone was proved to be the only product of oxidation of DBT. Furthermore, the process of ECODS system was confirmed by GC-MS.Though H2O2is one of the best candidates as an oxidant, high concentration of H2O2is potentially explosive issue during transportation and may do harm to human health. In order to obtain deep-desulfurization fuel with low concentration Of H2O2, a series of organic hexacyanoferrates were synthesized and employed as catalysts in ionic liquids (ILs) for catalytic oxidation of dibenzothiophene (DBT) and benzothiophene (BT) and4,6-dimethyldibenzothiophene (4,6-DMDBT). High activity was achieved by using1-butyl-3-methylimidazolium hexacyanoferrate ([C4mim]3Fe(CN)6) as catalyst and1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim]BF4) as extractant in the presence of H2O2under mild conditions. It was interesting to find that the concentration of H2O2had a significant influence on desulfurization efficiency. The sulfur removal was76.3%with30wt%H2O2as oxidant while it could reach97.9%with7.5wt%H2O2. Electron spin-resonance (ESR) spectroscopy measurements gave the evidence that the active oxygen species O2·-was generated in the catalytic oxidative desulfurization process and gas chromatography-mass spectrometer (GC-MS) analysis indicated that the sulfur compounds were oxidized to the corresponding sulfones. The kinetic investigations showed that oxidation of sulfur compounds presented a pseudo first-order kinetic.Magnetic ionic liquids (MILs)1-n-butyric acid-3-methylimidazolium chloride/xFeCl3(x=0.5,1,1.5,2)([C3H6COOHmim]Cl/xFeCl3) were synthesized and characterized. In desulfurization peocess, the IL acted not only as catalyst but also extractant. The acidities of these MILs were characterized by using pyridine and acetonitrile as IR spectroscopy probes. It found that [C3H6COOHmim]Cl/2FeCl3was both Bransted and Lewis acidic. The magnetic susceptibilities of [C3H6COOHmim]Cl/2FeCl3were measured using a Quantum Design superconducting quantum interference device (SQUID). The MIL [C3H6COOHmim]Cl/2FeCl3was found to be highly active for extraction and catalytic oxidative desulfurization of model oil under mild conditions. Of note, the removal of benzothiophene (BT), which has been regarded as a refractory aromatic sulfur compound, could be achieved up to100%in10min. After reaction, the MIL and model oil could be easily separated by applying an external magnetic field due to its paramagnetic property.更多还原