Facile Route for Fuel Desulfurization Using Generated Superoxide Ion in Ionic Liquids

Abstract

In this study, a novel desulfurization method was conducted using the superoxide ion (O 2 •−) generated chemically in four ionic liquids (ILs): 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, N-methoxyethyl-N-methylmorpholinium bis(trifluoromethylsulfonyl)imide, 1-(2-methoxyethyl)-1-methylpiperidinium tris(pentafluoroethyl)trifluorophosphate, and 4-(2-methoxyethyl)-4-methylmorpholinium tris(pentafluoroethyl)trifluorophosphate. Remarkably, it was found that O 2•− can convert the sulfur compounds (i.e., thiophene and 2-methylthiophene) dissolved in these ILs. The products of the conversion were identified as H 2 O, CO 2 , and SO 3 . The conversion percentage ranged from 35 to 99% for thiophene and 20 to 96% for 2-methylthiophene. In addition, a mechanism was proposed for this conversion. Furthermore, the effect of temperature on this reaction was studied and the solubility of sulfur compounds in these ILs was determined. The ILs did not only behave as media for the generation of O 2 •−, but they also possessed catalytic activity to accelerate the reaction rate between O 2•− and substrates.

Superoxide Ion as Oxidative Desulfurizing Agent for Aromatic Sulfur Compounds in Ionic Liquid Media

“…These results indicated that the conversion of BT was easier than that of DBT, and this difference was attributed to two factors, i.e., the electron density around the sulfur atom and the steric hindrance. This is in agreement with a recent study conducted on the conversion of thiophene and 2-methylthiophene using O 2 •– . The electron densities around the sulfur atoms in BT and DBT were calculated by Otsuki et al (2000) as 5.739 and 5.758, respectively .…”

Investigating the Long-Term Stability and Kinetics of Superoxide Ion in Dimethyl Sulfoxide Containing Ionic Liquids and the Application of Thiophene Destruction

“…Remarkably, it was found that O2 − destroyed close to 90% of the thiophene in [EDMPAmm][TFSI] at ambient conditions. This result was in good agreement with the findings of recent studies (Chan et al, 2008;Hayyan et al, 2015b;Hayyan et al, 2016b). Chan et al (2008) zation process.…”

“…Hence, they have been used to desulfurize fuels by various methods, including extraction (Ferreira et al, 2014;Lu et al, 2014) and oxidative desulfurization (Jiang et al, 2014;Lü et al, 2014). Recently, our group reported the possibility of using O2 − generated in ILs to destroy chlorinated hydrocarbons and sulfur compounds (Hayyan et al, 2012f;Hayyan et al, 2012e;Hayyan et al, 2015b;Hayyan et al, 2016b;AlNashef et al, 2013). Therefore, it also was worthwhile to explore using O2 − to destroy sulfur compounds in one of the studied ILs.…”

Physicochemical properties of piperidinium, ammonium, pyrrolidinium and morpholinium cations based ionic liquids paired with bis(trifluoromethylsulfonyl)imide anion

“…Furthermore ILs are highly tunable and can be designed with a specific task in mind, hence the term 'designer solvents' that is sometimes used to describe them [7]. For this reason ILs have been explored for a wide range of applications including catalysis [8,9], electrochemistry [10,11], fuel cells [12] and separation processes [13].…”