Study on the selective separation of methanol and methyl ethyl ketone from the azeotropic system using ionic liquids and their separation mechanism

In this work, two ionic liquids (ILs) 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([DMIM][NTf2]) and tributylmethylammonium bis(trifluoromethanesulfonyl)imide ([N-4441][NTf2]) were synthesized and used to separate the methanol (MeOH) and methyl ethyl ketone (MEK) azeotropic system. The VLE data of the binary system (MeOH + MEK) and the ternary system (MeOH + MEK + IL) were measured at 101.3 kPa. The binary VLE data were tested by Wisniak's L-W method and van Ness method, the ternary VLE data were tested by van Ness method, and it was found all the binary and ternary VLE data were thermodynamically consistent. The NRTL and UNIFAC-Lei activity coefficient models were used to fit the experimental data and it was found that both models could be applied to the system, but the NRTL model was more suitable. Through the analysis of the experimental data, it was found that both ILs could increase the relative volatility of MeOH to MEK, the effect became obvious with the increase of the IL content, and the azeotropic phenomenon could be eliminated as the content of ILs achieved a certain value. The ability of the two ILs to break azeotrope was in the order of [DMIM][NTf2] > [N-4441] [NTf2]. The minimum mole fraction of [DMIM][NTf2] and [N-4441][NTf2] breaking the azeotrope of MeOH and MEK is 0.035 and 0.039, respectively, which is lower than that of the reported best ionic liquid. Finally, the separation mechanism was explored through excess enthalpy analysis, sigma-profile analysis, and atomic charge calculation to promote the understanding of the process. (C) 2021 Published by Elsevier B.V.

Automated summary

In this study, two ionic liquids were synthesized and used to separate the azeotropic system of methanol and methyl ethyl ketone. Experimental data showed that the ionic liquids were able to increase the relative volatility of methanol to methyl ethyl ketone and successfully break the azeotropic phenomenon.