Extraction of 2-phenylethanol (PEA) from aqueous phases using tetracyanoborate-based ionic liquids

Abstract

2-Phenylethanol (PEA) is an important alcohol involved in aroma and flavour of food, soft drinks, candy, ice cream, pudding, chewing gum and cookies. This study investigates the ability of three tetracyanoborate-based ionic liquids (ILs) for the extraction of PEA from aqueous phases. In this regard, experimental measurements of liquid-liquid equilibria (LLE) in the binary systems {IL (1)+PEA or water (2)} and ternary systems of {IL (1)+PEA (2)+water (3)} at temperature T=308.15K and ambient pressure were undertaken. The ILs investigated were 1-hexyl-3-methylimidazolium tetracyanoborate [HMIM][TCB], 1-decyl-3-methylimidazolium tetracyanoborate [DMIM][TCB], and 1-butyl-1-methylpyrrolidinium tetracyanoborate [BMPYR][TCB]. The suitability of the ILs for use as entrainers for the extraction of PEA from water has been evaluated in terms of the selectivity and solute distribution ratio. An immiscibility gap was observed in the binary systems of (IL+water). All ILs showed complete miscibility with PEA in the liquid phase at a temperature T=308.15K. The average selectivity of the extraction of PEA from water increases in the following order: [HMIM][TCB] (Sav=408)<[BMPYR][TCB] (Sav=509)<[DMIM][TCB] (Sav=577). The solute distribution ratio increases in the following order: [HMIM][TCB] (βav=178)<[DMIM][TCB] (βav=198)<[BMPYR][TCB] (βav=241). The best IL with the highest selectivity and acceptable distribution ratio is [DMIM][TCB]. The LLE data for the systems were correlated with the NRTL model. The model satisfactorily describes the solubility of the ternary systems with an average root mean square deviation of σx=0.005.