Halogen-free ionic liquids (ILs) like 1-n-butyl-3-methylimidazolium octylsulfate ([BMIM][OcSO_4]) or 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO_4]) are suitable extracting agents for the deep desulfurization of oil refinery streams by liquid-liquid-extraction. This concept can be considered as an interesting alternative or supplemental technology to conventional hydrotreating for deep desulfurization down to values of 10 ppm S or even lower. The results show excellent selective extraction properties of ILs, especially with regard to refractive S-species in middle distillates like diesel oil. Mild process conditions - ambient temperature and pressure as well as the fact that no hydrogen is needed - are major advantages in comparison to conventional hydrodesulfurization (HDS). The concept is probably even more attractive for FCC-gasoline desulfurization, as the new extractive method allows the removal of S-species without loss of octane number.
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