Nonaqueous System of Iron-Based Ionic Liquid and DMF for the Oxidation of Hydrogen Sulfide and Regeneration by Electrolysis

Abstract

To improve the hydrogen sulfide removal efficiency with the application of an iron-based imidazolium chloride ionic liquid (Fe(III)-IL) as desulfurizer, Fe(II) and N,N-dimethylformamide (DMF) are introduced to Fe(III)-IL to construct a new nonaqueous desulfurization system (Fe(III/II)-IL/DMF). Following desulfurization, the system can be regenerated using the controlled-potential electrolysis method. The addition of Fe(II) in Fe(III)-IL is beneficial for the hydrogen sulfide removal and the electrochemical regeneration of the desulfurizer. The addition of DMF in Fe(III/II)-IL does not change the structure of Fe(III/II)-IL but clearly decreases the acidity, increases the electrolytic current, and decreases the stability of the Fe-Cl bond in Fe(III/II)-IL. Fe(III/II)-IL/DMF can remove hydrogen sulfide and can be regenerated through an electrochemical method more efficiently than can Fe(III/II)-IL. After six cycles, the desulfurization efficiency remains higher than 98%, and the average conversion rate of Fe(II) is essentially unchanged. No sulfur peroxidation occurs, and the system remains stable. Therefore, this new nonaqueous system has considerable potential for removing H2S in pollution control applications.

Experimental investigations on the regeneration of desulfurized 1‐butyl‐3‐methylimidazolium tetrachloroferrate [Bmim][FeCl4] and 1‐butyl‐3‐methylimidazolium thiocyanate [Bmim][SCN] ionic liquids: A raman spectroscopic study

“…The attachment or solubility of the DBT molecules into the co‐solvent hexane can be identified by observing the new peak in the Raman spectra (Figure ) within the range of 1,600 cm. The results are in good agreement with the reported studies …”

Metal-Based Ionic Liquids in Oxidative Desulfurization: A Critical Review

“…However, Lee et al stated that [Bmim]­FeCl 4 was partially soluble in water at room temperature, due to the hydrogen bonding interactions between FeCl 4 – and water molecules and the hydrophilic imidazolium ring. Moreover, the solvent effect will greatly decrease the stability of Fe–Cl bonds in FeCl 4 – anions, which may lead to the decomposition of FeCl 4 – anions, owing to the relatively weak interaction of Fe–Cl bonds (2.225 Å) compared to Fe–N bonds (2.065 Å) . By regulating the ligand species, the novel metal complex ILs containing more stable iron complex ions such as biomimetic [(Porp)­Fe­(III)] + that can activate oxygen and basic [Fe­(EDTA)] − have been prepared. − Unlike metal chloride ILs and POM-ILs, the metal complex ions can be incorporated in cations and/or anions in the metal complex ILs with different ligands, which results in various types of metal complex ILs with particular properties (Tables S1–S3).…”

“…Nonaqueous wet oxidation desulfurization process and desulfurization mechanism: (a) Nonaqueous wet oxidation desulfurization process in Fe-IL and the Fe-IL regenerated by air. (b) ODS mechanism of H 2 S removal in Fe­(III/II)-IL/DMF system …”

Screening of Metal Chloride Anion-based Ionic Liquids for Direct Conversion of Hydrogen Sulfide by COSMO-RS

“…Many studies have reported the potential use and candidacies of conventional room temperature ILs (RTILs) for H 2 S conversion experimentally [10,11]. However, it is found out that the solubility and capacity of H 2 S in these ILs are still low at low pressure and thus, unable to perform their tasks efficiently [12][13][14][15][16]. Therefore, a new kind of ILs, Task Specific ILs (TSILs) such as metal chloride anion based ILs has been proposed in this research for conversion of H 2 S [17,18].…”