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

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• 作者：Maan HayyanAbdulkader M. Alakrach ; Adeeb Hayyan ; Mohd Ali Hashim ; Hanee F. Hizaddin
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2017
• 出版时间：February 6, 2017
• 年：2017
• 卷：5
• 期：2
• 页码：1854-1863
• 全文大小：605K
• ISSN：2168-0485

文摘

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.