Application Of Ionic Liquids To Refining Hydrocarbon Fuels

Polar aromatics or sulfur componds in hydrocarbon fuel influence its quality largely. As harmful substances, e.g. SOx and NOx produced during the combustion process not only affect the engine, but also pollute the enviroment. Hence, to control the aromatic and sulfur contents is a very important step in the refining process of hydrocarbon fuels. Liquid-liquid extraction is one of the effective methods to reduce the aromatic and sulfur components. Recently, ionic liquids (ILs) become to be new extractants, because of their specially physical and chemical properties, and environmental performance. The dearomatization and desulfurization of hydrocarbon fuels by using novel N-alkyl piperazinium-based ILs as extractants have been studied in this thesis.A series of novel ILs have been synthesized by direct neutralization of N-alkyl piperazine and organic acids. The synthesized ILs are characterized by elemental analyse, IR and1H NMR. The properties of ILs, melting point, thermal stability and solubility, are determined. As the problem of high viscosity of a ionic liquid could be resolved partly by means of adding organic solvents, the densities and viscosities for binary mixtures of the ionic liquid, N-ethyl piperazinium propionate, with n-alcohols (methanol, ethanol, n-propanol and n-butanol) were determined to provide fundamental data for ionic liquid extraction.Solid adsorption method and ionic liquid extraction method are used for the dearomatization. The dearomatization performance of activated carbon is higher than that of silica gel, and the surface-modified activated carbons show much higher adsorbability. The novelly synthesized piperazinium-based ILs are introduced to extraction dearomatization. Effects on the extraction efficiency of the temperature. the amounts of IL and cosolvent are investigated. The results indicate that the amounts of IL and cosolvent play very important roles in the extraction process and the efficiency is greatly influenced by the cation and anion structures in the N-alkyl piperazinium-based ILs. The ILs with aromatic or hydrophobic anions are found to have better extraction capability than the others. In order to investigate the effects of the decreased aromatic content on the thermal stability of a hydrocarbon fuel, the thermal-oxidation stability of the hydrocarbon fuel is investigated by a static test. The thermal-oxidation stability of the hydrocarbon fuel is analysed by the iodine colorimetry and ultraviolet-visible spectrometry (UV-vis). The results indicate that the decreased aromatic content is helpful to improve the thermal stability of a hydrocarbon fuel.The desulfurization capacity of five ILs, N-methyl piperazinium lactate (NMPL), N-ethyl piperazinium lactate (NEPL), N-methyl piperazinium boratofluorate,(NMPBF),1,1,3,3-tetramethylguanidium lactate (TMGL) and N-ethyl piperazinium propionate (NEPP), with thiophene, benzothiophene, dibenzothiophene and butanethiol as the model compounds are investigated. The sulfur content in a model oil was analysed by high performance liquid chromatography (HPLC) and a microcoulometry titrator. It is indicated that the desulfurization performance of NEPP is the best, followed by NEPL and TMGL. For a specific ionic liquid, the removal ability is shown for dibenzothiophene followed by benzothiophene and thiophene. It is also verified that multiple extraction can achieve higher efficiency of desulfurization and the ILs can be recycled without a significant decrease in activity.