Application Research Of Ionic Liquids In Catalytic Oxidation Desulfurization Of Fuel Oil

In order to effectively control environmental pollution, most countries have made laws or regulations to restrict the sulfur content in fuel oil with a more rigorous standard. Among desulfurization techniques, chemical oxidation-ionic liquids (ILs) extraction desulfurization coupling technology, which has many advantages such as mild conditions, simple techniques, non-hydrogen, high desulfurization efficiency, shows promising as an approach for deep desulfurization. Applications of different ILs in catalytic oxidation desulfurization(CODS) were investigated with H₂O₂ as oxidant, thiophene/dibenzothiophene(DBT) in n-octane as model oil. The CODS mechanisms were speculated and kinetics equations were established.A new quaternary ammonium salt IL (C₄H₉)₄NBr·2C₆H₁₁NO, was prepared through hydrogen bonds under the condintion of solvent-free, one-step procedure using tetrabutylammonium bromide and caprolactam as raw material. The IL (C₄H₉)₄NBr·2C₆H₁₁NO were characterized by ¹H NMR, ¹³C NMR, MS and FT-IR. IL (C₄H₉)₄NBr·2C₆H₁₁NO, which has many advantages such as preparation with high atom economy, simple operation, easy access to raw materials, low cost, environmentally friendly, has good prospects for industrial application.The prepared IL (C₄H₉)₄NBr·2C₆H₁₁NO was employed as catalyst for ODS of thiophene in n-octane in the present of H₂O₂ and CH₃COOH. The effect of the amount of catalyst, H₂O₂ and CH₃COOH, reaction time and temperature were investigated in details. The result shows the kinetics of catalytic oxidation of thiophene is pseudo-first-order. The apparent rate constant (1.05×10^-3) in this system is higher near one order power than that of (C₄H₉)₄NBr system reported in literature; half-life (660 s) is shorter 1 time than reported value. (C₄H₉)₄NBr and C₆H₁₁NO of IL showed synergistic catalytic effect, thus the oxidation time was greatly short. The CODS was achieved 98.8% removal rate of thiophene in n-octane and 95.3 % of fluidized catalytic cracking (FCC) gasoline under optimal conditions after 30 min in the absence of other organic extractants.ODS of DBT in n-octane with H₂O₂/CH₃COOH using IL (C₄H₉)₄NBr·2C₆H₁₁NO as catalyst and extractant has been studied. We find that the influence to the desulfurization efficiency of DBT decreases in the order: Voil/VIL > molar ratio of O/S > oxidation temperature > oxidation time according to the R values of orthogonal experiments. Br?nsted acidic ILs [Hnmp]HSO₄ and [Hnmp]H₂PO₄, were prepared and characterized by 1H NMR and FT-IR. TGA-DTA test indicates that ILs have high thermal stability and wide range of liquid states. The acidity of ILs was investigated by IR spectroscopy probe method.ODS of DBT in n-octane with Br(?)nsted acidic ILs [Hnmp]H₂PO₄ as catalytic solvent and H₂O₂ as oxidant was optimized by orthogonal experiments. DBT in n-octane and actual diesel was removed 99.8% and 64.3% under the optimal conditions, respectively. The result shows the kinetics of ODS of DBT is pseudo-first-order with apparent rate constant of 1.13×10^-4s^-1 and activation energy of 58.53 kJ/mol, the kinetic equation is ln(C0/Ct) = 0.408t– 0.194. The ODS combined acidic ILs can be avoided the use of volatile organic acids and simplified operation of ODS.Dual acidic IL [Hnmp] ZnCl₃ was used in ODS of thiophene in n-octane The results show Lewis acid (anion ZnCl₃^-) formÏ€-complexation with delocalizedÏ€-bond of thiophene, Br?nsted acid (cation [Hnmp]⁺ ) of IL provide acidic medium of ODS. Thus complexation extraction of thiophene by [Hnmp]ZnCl₃ was high-performance to enhance the capacity of sulfur. Thiophene in IL phase was oxidized to sulfone by hydroxyl radicals with higher oxidation activity than H₂O₂, came from the decompose of H₂O₂ with [Hnmp]+. The ODS was achieved 99.8% removal rate thiophene in n-octane under optimal conditions in combined effect of anion and cation of [Hnmp] ZnCl₃.