Effective removal of nitrogen compounds from model diesel fuel by easy-to-prepare ionic liquids

The removal of nitrogen compounds by liquid-liquid extraction using ionic liquids (ILs) as extraction solvents has been limited by the lack of easy-to-prepare, low cost and highly efficient ILs. To overcome this limitation, the present work synthesized protic ILs (PILs) via acid-base reaction and investigated their extraction ability for nitrogen compounds (quinoline, indole and carbazole) from model fuel ( n -dodecane). Experimental results suggested that the PIL, triethylammonium p -toluenesulfonate (TEA-TSA), exhibited higher extraction ability for indole and carbazole as compared to the 1-butyl-3-methylimidazolium ([C 4 mim] + ) based ILs due to the stronger π-π interaction between TEA-TSA and nitrogen compounds. Among a number of ILs, TEA-TSA containing a slight excess of p -toluenesulfonic acid (2%, molar percent) was particularly promising as extractant because of its excellent extraction performance for the basic and neutral nitrogen compounds. Furthermore, the suggested PIL could be easily regenerated and reused via a back extraction process. The results showed that extractive denitrogenation using PILs as extractants was a potential technique to produce clean fuel considering their stronger extraction ability, lower-cost and easy-to-prepare characteristics.