Abstract
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.
Highlights
Sulfur oxides (SOx) resulting from the combustion of sulfur compounds in fuels have become an increasingly serious environmental problem worldwide as they are a major cause of acid rain and atmospheric pollution
The results indicated that the adsorptive process combined with ionic liquids (ILs) extraction could provide high efficiency and selectivity, which can be regarded as a promising energy efficient desulfurization strategy for production of low-sulfur gasoline
The optimization of experimental variables in the extraction of sulfur compounds from gasoline by ILs was carried out using a two-level fractional factorial design
Summary
Sulfur oxides (SOx) resulting from the combustion of sulfur compounds in fuels have become an increasingly serious environmental problem worldwide as they are a major cause of acid rain and atmospheric pollution. Deep HDS process will require a considerable increase in the consumption of energy and hydrogen, which can substantially improve the reactivity and selectivity of the catalyst, resulting in undesirable side reactions. Such side reactions can lead to a decrease in the octane number of gasoline (Nie et al 2006; Wang et al 2007). From both environmental and economic considerations, various alternative deep desulfurization processes have been extensively developed in
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