Separation of methyl ethyl ketone - methanol azeotrope by ionic liquids: Thermodynamic and molecular mechanism

In this work, three ionic liquids (ILs) based on acetate, namely tetraethylammonium acetate ([N-2222][Ac]), 1-hexyl-2,3-dimethylimidazolium acetate ([HMMIM][Ac]), and tributylmethylammonium acetate ([N-4441][Ac]) were selected to separate the methyl ethyl ketone - methanol azeotrope. The vapor-liquid equilibrium (VLE) data of the binary system (methyl ethyl ketone + methanol) and the ternary systems (methyl ethyl ketone + methanol + IL) were measured at 101.3 kPa. It was found that all the experimental data were thermodynamically consistent and the three ionic liquids could effectively eliminate the azeotropic phenomenon at a specific concentration. The separation ability of the three ionic liquids is [N-2222][Ac] > [HMMIM][Ac] > [N-4441][Ac]. The NRTL model was used to correlate the VLE data and was found to have an excellent quality of fit. Moreover, the quantum chemical calculations, COSMO-RS model, and FT-IR analysis were used synergistically to provide microscopic insights into the separation mechanism of ionic liquids.

Automated summary

In this study, three acetate-based ionic liquids (ILs) were used to separate the azeotrope of methyl ethyl ketone and methanol. Experimental results showed that all three ILs could effectively eliminate the azeotropic phenomenon at a specific concentration. The NRTL model was used to correlate the vapor-liquid equilibrium (VLE) data and provided a good fit. In addition, quantum chemical calculations, COSMO-RS model, and FT-IR analysis were applied to gain microscopic insights into the separation mechanism of ILs.