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To improve the safety and efficiency of the Se/CO/H2O redox process, five ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate, [bmin][BF4], 1-propyl-3-methylimidazolium tetrafluoroborate, [pmim][BF4], 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate, [bdmim][BF4], N-ethylimidazolium tetrafluoroborate, [eim][BF4], and 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [bmim][OTf]) were used as solvents instead of dimethyl formamide. The effect of the structure of anions and cations in ionic liquid, and water content on the Se reduction rate was investigated. In addition, the Se reduction pathway was also explored using UV-vis spectroscopy. The results show that the Se reduction rate is significantly increased by ∼1.4 times using [bmim][BF4], mainly by activating the water molecules. [ABSTRACT FROM AUTHOR]

Regenerable flue gas desulfurization (FGD) is highly attractive because of the transformation of sulfur dioxide (SO2) to high-value products. In this study, selenium-assisted SO2 reduction by carbon monoxide (CO) in the liquid phase [dimethylformamide (DMF) + water (H2O) mixture] is proposed and applied in the FGD process. This process realizes recycle of the elemental sulfur product under room temperature. Moreover, results show that both the selenium catalyst and DMF solvent have good stability and can be well recycled, implying that this process is economically feasible. Furthermore, the mechanism of selenium-assisted SO2 reduction by CO in DMF/H2O is investigated. Results show that the selenium catalyst dissolves in solution and forms Sen2- species, which are the active intermediates and promote formation of the sulfur product. [ABSTRACT FROM AUTHOR]