Deep Desulfurization of Fuels Using Imidazole Anion-Based Ionic Liquids

An extractive desulfurization method was developed with 1,8-diazabicyclo[5.4.0]undec-7-ene Im ([DBU][Im]) and 1,1,3,3-tetramethylguanidine Im ([TMG][Im]) as extractants. Effects of extraction time, ionic liquid (IL):model fuel mass ratio, ILs species, initial concentration of sulfur, and temperature on removal efficiency of sulfur compound were investigated. The removal efficiencies of dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene with [DBU][Im]/[TMG][Im] as extractants were 79.2%/69.4%, 68.4%/57.7%, and 61.2%/54.4%, respectively. The interaction between [DBU] Im] and sulfur compounds could be enhanced by extra heterocyclic aromatic ring in DBU cation and imidazolium ring in Im anion. Both extraction processes with these two ILs as extractants were fast (extraction equilibrium prepared ILs was studied, and the multistage cross-current extraction characterization methods of nuclear magnetic resonance hydrogen spectrum and Fourier transform infrared spectroscopy and the calculation methods of optimized geometry and interaction energy between sulfur compounds and extractants by Gaussian 09 software were used for the study of extraction mechanism. Furthermore, the oxidative extractive method was used for deep desulfurization of model fuel and real diesel fuel.