Study on extraction of thiophene from model gasoline with bronsted acidic ionic liquids

Bronsted acidic ionic liquids (ILs), N-methylimidazole hydrogen sulfate ([HMIm]HSO4) and N-methylpyrrolidone hydrogen sulfate ([HNMP]HSO4), are synthesized and employed as extractants to extract thiophene from model gasoline (thiophene dissolved in n-octane). The effect of extraction temperature, extraction time and volume ratio of ILs to model gasoline on desulfurization rates is investigated. Then, the optimal desulfurization conditions are obtained: the ratio of ILs to model gasoline is 1:1, extraction temperature is 50 degrees C for [HMIm]HSO4 and 60 degrees C for [HNMP]HSO4, extraction time is 60 min. Meanwhile, the desulfurization rate of [HNMP]HSO4 for model gasoline is 62.8%, which is higher than that of [HMIm]HSO4 (55.5%) under optimal conditions. The reason is discussed on the basis of the interaction energy between thiophene and ILs at the B3LYP/6-311 ++ G(d,p) level. Furthermore, the total desulfurization rate of [HNMP]HSO4 and [HMIm]HSO4 reaches 96.4% and 94.4%, respectively, by multistage extraction. Finally, the used ILs can be reused by vacuum drying, and their desulfurization rates are not significantly decreased after recycling 7 times in single-stage desulfurization.