Solubility of ionic liquids in 2-phenylethanol (PEA) and water

• Phase equilibria in binary systems of (IL + 2-phenylethanol, or water) were measured.
• Piperidinium-, N-hexylquinolinium-, N-hexylisoquinolinium and imidazolide-based ILs were used.
• The piperidinium-based ILs and [BMIM][TDI] showed complete miscibility with 2-phenylethanol.
• [HMPIP][NTf2] and [BMIM][TDI] is proposed as entrainer for the separation processes of 2-phenylethanol from water.

New experimental (solid + liquid) phase equilibrium (SLE) data for eight binary systems are reported. The systems are composed of the ILs: 1-ethyl-1-methylpiperidinium bis(trifluroromethylsulfonyl)imide, [EMPIP][NTf2], 1-propyl-1-methylpiperidinium bis(trifluroromethylsulfonyl)imide, [PMPIP][NTf2], 1-butyl-1-methylpiperidinium bis(trifluroromethylsulfonyl)imide, [BMPIP][NTf2], 1-hexyl-1-methylpiperidinium bis(trifluroromethylsulfonyl)imide, [HMPIP][NTf2], N-hexylquinolinium bis(trifluroromethylsulfonyl)imide, [HQuin][NTf2], N-hexylisoquinolinium bis(trifluroromethylsulfonyl)imide, [HiQuin][NTf2], [CCNMIM][TDI] and 1-butyl-3-methylimidazolium 4,5-dicyano-2(-trifluoromethyl)-imidazolide, [BMIM][TDI] with 2-phenylethanol (PEA). The synthesis of a new IL is presented for 1-(cyanomethyl)-3-methylimidazolium 4,5-dicyano-2-(trifluoromethyl)-imidazolide, [CCNMIM][TDI]. A differential scanning calorimetry (DSC) was used to determine the melting point and the enthalpy of melting of [CCNMIM][TDI]. The majority of the systems containing piperidinium-based ILs and [BMIM][TDI] showed complete miscibility with PEA. Simple eutectic mixture behaviour was found for the latest ILs. The solubility of the ILs decreases in the order [HQuin][NTf2] > [HiQuin][NTf2] > [EMPIP][NTf2] > [CCNMIM][TDI]. The correlation of the liquidus curves was undertaken with the NRTL excess Gibbs energy equation. The model correlates the solubility of the three systems (without [EMPIP][NTf2]) with an average root mean square deviation, σT = 0.67 K. To the best of our knowledge this is the very first paper where the SLE of PEA have been measured for systems with ILs. The solubility of six ILs in water were also measured. The solubility of the chosen ILs in water reveals SLE and/or (liquid + liquid) phase equilibrium (LLE) in these binary systems. The results of solubility of ILs in PEA and water can be used to design future alternative processes of the extraction of PEA, or separation from fermentation broth that involves these mixtures.

Figure optionsDownload as PowerPoint slide