Extraction of butan-1-ol from aqueous solution using ionic liquids: An effect of cation revealed by experiments and thermodynamic models

Abstract

Abstract Production of bio-butanol from biomass by fermentation in an aqueous phase needs new solutions and entrainers for the separation of product. Ionic liquids (ILs) are attractive significant attention as novel, low pressure solvents alternative to conventional organic solvents for biphasic solvent extraction. Ternary liquid-liquid equilibrium data are presented for mixtures of {ionic liquid (1) + butan-1-ol (2) + water (3)} at T = 298.15 K and ambient pressure to analyze the performance of the IL in the extraction of butan-1-ol from aqueous phase. The bis{(trifluoromethyl)sulfonyl}amide-based ILs have been studied: octyltriethylammonium bis{(trifluoromethyl)sulfonyl}amide, [N8,2,2,2][NTf2], methyltrioctylammonium bis{(trifluoromethyl)sulfonyl}amide, [N8,8,8,1][NTf2], 1-dodecyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [DoMIM][NTf2] and 1-hexyloxymethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [C6H13OCH2MIM][NTf2]. The results are discussed in terms of the selectivity and the solute distribution ratio of separation for the related systems. The IL with three octyl alkyl chains, [N8,8,8,1][NTf2] at the ammonium-based cation shows higher selectivity and the same distribution ratio in comparison to the other ILs in this process. Additionally, the viscosity of [N8,2,2,2][NTf2], and density and viscosity of the best IL, [N8,8,8,1][NTf2] were measured for the collection of physico-chemical properties of the ILs used in this work. The non-random two liquid NRTL model was used successfully to correlate the experimental tie-lines. The prediction of ternary compositions was shown with good precision using COSMO RS for the ILs used in this work and for data from literature. The data and calculations presented here indicate the possible use of the model COSMO RS for the prediction of ternary LLE and of the use of [N8,8,8,1][NTf2], as a good solvent for the separation of butan-1-ol from water using solvent extraction.