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

Abstract

The generation of superoxide (O2 •–) in ionic liquids (ILs) has been used to destroy hazardous materials. In this study, O2 •– was used for the oxidative desulfurization of benzothiophene (BT) and dibenzothiophene (DBT) in two ILs as reaction media. The O2 •– was released by dissolving potassium superoxide in 1-butyl-1-methylpyrrolidinium bis­(trifluoromethylsulfonyl)­imide [BMPyrr]­[TFSI] and n-methoxyethyl-n-methylmorpholinium bis­(trifluoromethylsulfonyl)­imide [MOEMMor]­[TFSI]. The highest conversion percentages for BT in [MOEMMor]­[TFSI] and [BMPyrr]­[TFSI] were 99.4 and 96.6%, respectively, and the highest conversion percentages for DBT in [MOEMMor]­[TFSI] and [BMPyrr]­[TFSI] were 98.3 and 94.3%, respectively. As the temperature was increased, the reaction of the O2 •– with BT and DBT was enhanced significantly. The BT was converted easier than DBT due to the nucleophilic characteristic of the O2 •– and the higher electron density of the sulfur atom in DBT than that in BT. In addition, the ILs had a clear effect on the oxidative desulfurization reaction, in which the O2 •– demonstrated a higher conversion percentage in [MOEMMor]­[TFSI] than in [BMPyrr]­[TFSI]. This was the result of the stability of the O2 •– in the ILs that were used in the study. In addition, the σ-potential obtained using the “Conductor-like Screening Model for Real Solvent” (COSMO-RS) indicated that [MOEMMor]+ was a superior hydrogen bond donor and had a stronger affinity for the hydrogen bond acceptor than [BMPyrr]+. The reaction mechanism was reported, and no toxic byproducts were detected. This is the first study in which O2 •– in ILs was used for the conversion of BT and DBT to nonhazardous compounds, and this technique can be used for other hazardous materials.

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.…”

Sono-oxidative desulfurization of fuels using heterogeneous and homogeneous catalysts: A comprehensive review

“…Many solid, liquid and gas oxidizers have been evaluated. Inorganic chemicals such as oxone [32] , sodium persulfate [33] , potassium superoxide [34] , potassium dichromate [35] , sodium percarbonate [36] , sodium perchlorate [37] , hydrogen peroxide [38] , sodium hypochlorite [39] , solid oxidizers such as cyclohexanone peroxide [40] and organic chemicals such as t-butylhydroperoxide [41] and cumene hydroperoxide [42] as liquid oxidizers are used. The most distinctive feature of cyclohexanone peroxide as solid organic oxidizers and cumene hydroperoxide and t-butylhydroperoxide as liquid organic oxidizers is that they can all dissolve in the organic phase or fuel, thereby directly oxidizing sulfur compounds [43] , [44] .…”

Liquid Polymer Eutectic Mixture for Integrated Extractive-Oxidative Desulfurization of Fuel Oil: An Optimization Study via Response Surface Methodology

“…Some of the non-conventional ways to remove sulfur are currently being tested including biodesulfurization (BDS) [3][4][5], adsorptive desulfurization (ADS) [6][7][8], extractive desulfurization (EDS) [9][10][11][12], and oxidative desulfurization (ODS) [13,14]. Compared to BDS and ADS, EDS could be operated at mild conditions with the use of suitable extractant to desulfurize fuel oil.…”