Comparative Evaluation of [Imidazolium][Tf2N] and [Pyridinium][Tf2N] Ionic Liquids for the Liquid-liquid Extraction of Aromatics

The distribution ratios and separation factors for the four ternary systems heptane + toluene + [C(2)mim][Tf2N], or [C(4)mim][Tf2N], or [3-mC(2)py][Tf2N], or [3-mC(4)py][Tf2N] were determined at 313.2 K and atmospheric pressure. The four ionic liquids (ILs) show values of distribution ratio larger than those of sulfolane in the whole range of the toluene mole fractions in the heptane-rich phase. The pyridinium-based ILs clearly show the best values of toluene distribution ratio. However, there were really few differences between the separation factors of the pyridinium-based and imidazolium-based ILs with the same alkyl side chains in the cations. Just the use of the [3-mC(2)py][Tf2N] leads to higher values of separation factor in the whole range of compositions than those of sulfolane. Therefore, it was concluded that only the [3-mC(2)py][Tf2N] ionic liquid could reach better aromatic extraction results than sulfolane.