A Novel Approach for the Preparation of Tetrathionate Ionic Liquids and Study of Their Sulfur Dissolution Properties

TL;DR

Researchers developed a new method to make tetrathionate ionic liquids that dissolve sulfur efficiently and safely, offering advantages over traditional solvents.

Contribution

A novel synthetic method for tetrathionate ionic liquids is introduced, overcoming limitations of traditional approaches.

Findings

The new method produces tetrathionate ionic liquids in high purity and yield.

Tetrathionate ionic liquids effectively dissolve sulfur and could be used in gas extraction plants.

Mixing ionic liquids with organic solvents showed cooperative or salting-out effects.

Abstract

A series of sulfur dissolving tetrathionate ionic liquids (ILs), featuring imidazolium and pyridinium cationic heads, have been prepared and characterized along with their chloride IL precursors. A novel synthetic approach for the preparation of the proposed tetrathionate ILs has been introduced and successfully tested in the current work, yielding the desired compounds in quantitative yield and high purity, offering a significant advancement over the traditional Volynskii–Smolyaninov reaction. The presented method addresses key challenges of the traditional approach, solving the issues deriving from the influence of the IL cation on the reaction outcome and the unpredictability of the formed polythionate species. The solubility of elemental sulfur in the considered tetrathionate ILs has been investigated at various temperatures, providing good preliminary evidence of the suitability of these ILs as convenient and effective sulfur solubilizing media readily available on the field in “sour” gas extraction plants. Furthermore, the use of ILs instead of traditional organic solvents in operative conditions represents a noteworthy safety improvement due to their lower flammability and volatility. Finally, interesting results were obtained studying binary mixtures of organic solvents and ILs, with cooperative effects or salting-out effects being observed in relation to the type of solvent used.

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