Vapor–liquid equilibrium for tetrahydrofuran + methanol + tetrafluoroborate-based ionic liquids at 101.3 kPa

•VLE data for THF + methanol + tetrafluoroborate-based ionic liquids measured at 101.3 kPa.•[EMIM][BF4] totally eliminates the azeotropic point when its mole fraction is up to 0.20.•The ILs have a great salting-out effect, which enhances the relative volatility of THF.•The effect of alkyl chain length of ILs on the VLE for THF and methanol are compared.•The NRTL model has a good correlation with the experimental VLE data.

The vapor–liquid equilibrium (VLE) data for the ternary systems of tetrahydrofuran (THF) (1) + methanol (2) + 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) (3) and THF (1) + methanol (2) + 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) (3) are measured at 101.3 kPa with a modified Othmer still. The ionic liquids (ILs) give rise to the relative volatility of THF to methanol. [EMIM][BF4] has a stronger effect on the enhancement of the relative volatility than [BMIM][BF4]. [EMIM][BF4] even eliminates the azeotropic point when its mole fraction is up to 0.20, whereas [BMIM][BF4] pulls down the azeotropic point. The effect of two ILs on the VLE for THF + methanol system is discussed. The NRTL model proposed by Renon and Prausnitz reproduces the experimental values well.

Graphical abstractPotential entrainers for the separation of THF and methanol in extractive distillation.Figure optionsDownload full-size imageDownload as PowerPoint slide