Solubility of Thiophene and Dibenzothiophene in Anhydrous FeCl3- and ZnCl2‑Based Deep Eutectic Solvents

The solubilities of some common refractory-sulfur-containing compounds, namely thiophene and dibenzothiophene, were studied and measured in anhydrous FeCl3- and ZnCl2-based deep eutectic solvents (DES) at different temperatures under atmospheric pressure. The aim of this study is to explore the behavior of DESs toward solvation of sulfur-containing compounds so as to set a pace for the successful application of DESs into deep desulfurization of liquid fuels. The studied DESs were screened and prepared by the combination of anhydrous FeCl3 and ZnCl2 with different salts and hydrogen bond donors. High pressure liquid chromatography (HPLC) was employed for the quantitative measurements of solubilities of both thiophene and dibenzothiophene. It was found that FeCl3 based DESs exhibited higher solubilities (from 17 wt % to above 90 wt %) for dibenzothiophene as compared to the ZnCl2 based DESs (0.084–1.389 wt %). Moreover, FeCl3 based DESs exhibited complete miscibility with thiophene while ZnCl2 based DESs showed solubility values in the range of 1–10 wt % for thiophene. The experimental results obtained were further successfully modeled using the nonrandom two liquid (NRTL) model.