Polymer-supported ionic liquids: Synthesis, characterization and application in fuel desulfurization

Ionic liquids (ILs) were considered to be immobilized on solid supports to overcome the problems of the pure ILs in fuel desulfurization. Take Merrifield resin as solid support, four polymer-supported imidazole ionic liquids (PSILs) with different lengths of alkyl chain linkers were prepared by covalent binding and the structures were characterized by Fourier transform infrared (FTIR), elemental analysis, 13C solid state magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results suggested the series PSILs had been obtained. Then, the PSILs were investigated to remove thiophene (TS) or dibenzothiophene (DBT) from model gasoline (cyclohexane/TS or DBT) under certain conditions: (1) PSILs showed better sulfur removal ability than Merrifield resin, PS[unmim][BF4] showed the best percent sulfur removal which could up to ⩾30% due to the longest alkyl chain linker and the smallest particles. (2) The sulfur removal selectivity of DBT was better than TS for its higher density aromatic π-electrons. The Sips adsorption isotherms model fitted the adsorption experimental data of PS[unmim][BF4] for TS and DBT at 303.15 K best. Finally, the adsorption mechanism was discussed.