Vapor Liquid Equilibria for Ionic Liquid/Ethanol/Water Systems and the Effect of Anion Hydrolysis

• Published in: Chemical engineering & technology Vol. 43; no. 11; pp. 2277 - 2285
• Main Authors: Faghihi, Erfaneh, Mokhtarani, Babak, Mortaheb, Hamid Reza, Heydar, Kourosh Tabar, Mirzaei, Mojtaba, Sharifi, Ali
• Format: Journal Article
• Language: English
• Published: Frankfurt Wiley Subscription Services, Inc 01.11.2020
• Subjects: Anions; Binary mixtures; Dehydration; Ethanol; Hydrolysis; Ionic liquids; Ions; NMR; NRTL model; Nuclear magnetic resonance; UNIFAC model; Vapor‐liquid equilibria
• ISSN: 0930-7516; 1521-4125
• DOI: 10.1002/ceat.202000114

The performance of two tetrafluoroborate‐based ionic liquids (ILs) as entrainers in the dehydration of water/ethanol azeotropic mixtures was evaluated. Isobaric vapor‐liquid equilibrium (VLE) data were measured for the systems ethanol/water/1‐butyl‐3‐methyl imidazolium tetrafluoroborate and ethanol/water /n‐butylpyridinium tetrafluoroborate including the azeotropic region. VLE data for the ethanol/water, ethanol/IL, and water/IL binary mixtures were obtained at 100 kPa. The hydrolysis of the tetrafluoroborate anion was studied for both types of ILs by 19F NMR analysis. The hydrolysis of the tetrafluoroborate anion does not have much effect on the ethanol/water VLE. The 19F NMR analysis indicated that hydrolysis occurred at high mole fractions of water. Separation of the ethanol/water azeotrope is important for the use of ethanol as a fuel. The use of ionic liquids [BPy][BF4] and [Bmim][BF4] as entrainers to break this azeotrope was studied by determining isobaric vapor‐liquid equilibrium data. [Bmim][BF4] shows better performance for separation of ethanol from water. The experimental data were predicted with the NRTL and UNIFAC models.