Extractive desulfurization of fuel using N-butylpyridinium-based ionic liquids

Abstract

Sulfur compounds in fuels have become one of the sources of serious environmental problems. The extractive desulfurization using ionic liquids (ILs) has attracted great attention in recent years. In this work, the pyridinium-based ionic liquids (ILs) N-butylpyridinium thiocyanate ([C₄Py][SCN]), N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([C₄Py][NTf₂]), and N-butylpyridinium dicyanamide ([C₄Py][N(CN)₂]) were used as extractants for desulfurization of model fuels. The results demonstrate that the structure of the anion influences the extractive performance of ILs, following the order of [NTf₂] < [SCN] < [N(CN)₂], which was proved by the electrostatic interaction between ions and DBT through molecular dynamics simulations (MD). In addition, the selectivity of sulfur compounds by the extraction process followed the order of dibenzothiophene (DBT) > benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). Moreover, the [C₄Py][N(CN)₂] can be recycled at least 4 times with little decrease in the desulfurization activity.