Desulfurisation of oils using ionic liquids: selection of cationic and anionic components to enhance extraction efficiency

Abstract

Extraction of dibenzothiophene from dodecane using ionic liquids as the extracting phase has been investigated for a range of ionic liquids with varying cation classes (imidazolium, pyridinium, and pyrrolidinium) and a range of anion types using liquid–liquid partition studies and QSPR (quantitative structure–activity relationship) analysis. The partition ratio of dibenzothiophene to the ionic liquids showed a clear variation with cation class (dimethylpyridinium > methylpyridinium > pyridinium ≈ imidazolium ≈ pyrrolidinium), with much less significant variation with anion type. Polyaromatic quinolinium-based ionic liquids showed even greater extraction potential, but were compromised by higher melting points. For example, 1-butyl-6-methylquinolinium bis{(trifluoromethyl)sulfonyl}amide (mp 47 °C) extracted 90% of the available dibenzothiophene from dodecane at 60 °C.