Efficient desulfurization of gasoline fuel using ionic liquid extraction as a complementary process to adsorptive desulfurization

摘要

The extractive desulfurization of a model gasoline containing several alkyl thiols and aromatic thiophenic compounds was investigated using two imidazolium-based ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrachloroaluminate, and 1-octyl-3-methylimidazolium tetrafluoroborate, as extractants. A fractional factorial design of experiments was employed to evaluate the effects and possible interactions of several process variables. Analysis of variance tests indicated that the number of extraction steps and the IL/gasoline volume ratio were of statistically highly significant, but none of the interactions were significant. The results showed that the desulfurization efficiency of the model gasoline by the ILs could reach 95.2?% under the optimal conditions. The optimized conditions were applied to study the extraction of thiophenic compounds in model gasoline and several real gasoline samples; the following order was observed in their separation: benzothiophene?>?thiophene?>?3-methylthiophene?>?2-methylthiophene, with 96.1?% removal efficiency for benzothiophene. The IL extraction was successfully applied as a complementary process to the adsorptive desulfurization with activated Raney nickel and acetonitrile solvent. The results indicated that the adsorptive process combined with IL extraction could provide high efficiency and selectivity, which can be regarded as a promising energy efficient desulfurization strategy for production of low-sulfur gasoline.