Extractive desulfurization of gasoline using imidazolium-based phosphoric ionic liquids

Sulfur partition coefficients for sulfur compounds 3- methylthiophene ( 3-MT), benzothiophene ( BT), and dibenzothiophene ( DBT) between phosphoric ionic liquids ( ILs), namely, N- methyl- N- methylimidazolium dimethyl phosphate ([MMIM][ DMP]), N-ethyl-N-methylimidazolium diethyl phosphate ([EMIM][ DEP]), and N-butyl-N-methylimidazolium dibutyl phosphate ( BMIM][ DBP]), and gasoline were determined experimentally at 298.15 K over a wide range of sulfur content and compared with other IL extractants. The solubility of sulfur ( as DBT, BT) in ILs aqueous solution at 298.15 K and varying water content was also measured. It was shown that the desulfurization ability of the ILs for each sulfur component ( DBT, BT, 3- MT) followed the order of [ BMIM][ DBP] > [ EMIM][ DEP]. [ MMIM][ DMP], and the sulfur removal selectivity for a specified IL followed the order of DBT > BT > 3- MT. The phosphoric ILs are insoluble in gasoline while the fuel solubility in ILs is noticeable and follows the order of [ BMIM][ DBP]. [ EMIM][ DEP] > [ MMIM][ DMP]. Considering the relatively high sulfur removal ability, low fuel dissolvability, and small influence on the gasoline treated, [ EMIM][ DEP] might be used as a promising solvent for the desulfurization of gasoline via an extractive desulfurization ( EDS) process. The sulfur components in the spent ILs could be conveniently separated via a water dilution process.