| With more and more global environmental concerning, to produce super-low sulfur and emission-free fuels becomes the general development trend in clean fuels in the world today. Ionic liquids (ILs) have been used as a new"green"solvent, suitable for the deep desulfurization of fuels and showed great extractive capability in lab experiment. It is easy to operate, which needs no high temperature, no auxiliary equipment. What's more, it has little influence on oil and is innoxious to the environment. Besides, its extractive capability is very strong, especially extracts the baroque sulfide, such as thiophene etc. Oil extractive desulphurization with ionic liquid is hopeful to become a new promising green desulphurization technology.In this dissertation, 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4 ) was synthesized and the liquid-liquid equilibrium(LLE) of ionic liquid extracted model oil system and factors on which influence the desulfurating rate were studied in detail, and the rebirth of the extracted ionic liquid was also investigated primarily. Main conclusions are as follows:1. The synthesis of ionic liquid [Bmim]BF4 by two steps. It was then characterized and analyzed by IR, NMR, ICP, elementary analysis respectively. The FT-IR and NMR plates showed that the basic structure and functional group character were in accordance with ionic liquid [Bmim]BF4 which confirmed this substance is [Bmim]BF4 . Further analysis showed that [Bmim]BF4 had few impurities, which would have little influence on its latter use. Besides, [Bmim]BF4 contained traces of water because of its hydrophilicity.2. The solubility curve and density curve of 1-Butyl-3-methylimidazolium tetrafluoroborate extracting model oil system were measured according to the cloud point under 35℃, atmospheric pressure. The LLE data and partition ratio of thiophene were further calculated by turbidity-density method. Both Othmer-Tobias+Bancroft equations and Othmer-Tobias+solubility equations were used for correlation of the LLE data and showed good agreement with experimental data. However, Using Othmer-Tobias+solubility equations showed better correlation. The method could be used for correlation of liquid-liquid equilibrium for system with a low content.3. The different factors which influence the desulfur capability of the ionic liquid were investigated, including the time, oil-solvent ratio, temperature, the content of model oil, the times of extraction, the moisture content in the ionic liquid etc. It showed that the desulfurization degree increases with the temperature and oil-solvent ratio. Combined with the desulfurization effect and economic cost, it is optimal to choose temperature between 35℃~40℃, oil-solvent ratio under 1/3. The system needs a short time to get extractive equilibrium, about 40 min would be all right. The existence of olefin and aromatic hydrocarbon would decrease the partition ratio of thiophene to a certain degree. The moisture content has great influence on the desulfurization degree, thus it is necessary to reduce and avoid the moisture content from ionic liquid. The desulfurization rate would increase fast while the times of extraction increase. After 5 times of continuous extraction with the same model oil, the desulfurization rate increased from 16% to above 50%.4. The regeneration of extracted ionic liquid was realized by distillation under nitrogin. It showed that the maximum removal rate of thiophene rises with the temperature and time. The removal rate attained above 95% at 150℃, 300 min. The FT-IR plate showed that the basic structure and functional group character were in accordance with synthesized IL. Further more, there was no characteristic peak of thiophene, which proved that the ionic liquid had removed absolutely. Ionic liquid has good reusability. After 5 times of extraction-regeneration, the desulfurization rate of ionic liquid just fell down to 28.6301% from primarily 31.724%. |
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