(481e) Phase Equilibria of Mixtures Containing Alternative Solvents for Green Chemistry

Solvent selection is very important in the design and development of the reaction or separation and purification processes. Previously, conventional organic solvents were used for these solvents. However, these organic solvents are generally volatile organic compounds (VOCs), and they have environmental drawbacks such as being environmentally polluting [1]. Therefore, it is very important to find alternative environmentally friendly solvents that allow an effective reaction or separation.

Our group has studied ionic liquids (ILs) and fluorous solvents as green solvents for alternative solvents of VOCs. ILs have unique properties, such as high polarity, negligible vapor pressure, and conductive properties. ILs have been considered as entrainers for the extractive distillation or the liquid-liquid extraction [2,3]. On the other hand, fluorous solvents such as perfluoroalkane and perfluoropoly-ether have attracted a great deal of interest, because of their use in fluorous phase organic synthesis, in particular in fluorous catalysis (fluorous biphasic chemistry) [4]. When fluorous solvents are used instead of VOCs, the products can be easily separated in the biphasic system. The fluorous solvents can also be easily recycled. Therefore, the fluorous solvents can be used as a recyclable alternative to organic reaction solvents. A reliable knowledge of the phase equilibria containing IL or fluorous solvent is important for the design and development of the separation and purification processes. This paper reports our experimental results of phase equilibria of mixgtures containing green alternative solvents.

Firstly, we focused on liquidâ??liquid extraction as a separation method for essential oils. We investigated limonene and linalool as the citrus essential oil, and 1-alkyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide ([C_nMIM]⁺[TFSI]^-) (n = 4 and 6) and 1-butyl-3-methyl-imidazolium acetate ([BMIM]⁺[Ac]^-) as IL. The liquid-liquid equilibrium (LLE) data of the binary mixtures [C_nMIM]⁺[TFSI]^- + linalool, and ternary mixture limonene + linalool+ [BMIM]⁺[Ac]^-were determined by cloud point method.

Next, we investigated Galden^® HT-135 (1,1,2,3,3,3-hexafluorooxidized polymd), a polyether-type perfluorinated solvent, as a fluorous solvent with high boiling point. The boiling point of Galden^® HT-135 is 408 K [1,5], and therefore, its volatility is lower than perfluorohexane (boiling point: 329.75 K [6]). In addition, Galden^® HT-135 is cheaper than perfluorohexane. So, Galden^® HT-135 has been used as a reaction solvent for organic synthesis by some groups [5,7,8]. The LLE of binary mixtures Galden HT-135^®with selected alkanes and alcohols were measured up to the upper critical solution temperature (UCST). The experimental LLE behavior was compered to peviously reported those of binary mixtures perfluoroalkane + alkane [9, 10].

References

[1] F. M. Kerton, Alternative Solvents for Green Chemistry, RSC Publishing, Cambridge, UK, 2009.

[2] K. N, Marsh, J. A, Boxall, R. Lichtenthaler, Fluid Phase Equilib. 219 (2004) 93-98.

[3] M. Krummen, P. Wasserscheid, J. Gmehling, J. Chem. Eng. Data 47 (2002) 1411-1417.

[4] I. T. Horváth, J. Rábai, Science 266 (1994) 72-75.

[5] I. Ryu, H. Matsubara, H. Nakamura, D.P. Curran, Chem. Rec. 8 (2008) 351â??363.

[6] B. E. Poling, J. M. Prausnitz, J. P. Oâ??Connell, The Properties of Gases and Liquids, 5th ed., McGraw-Hill, New York, 2001.

[7] H. Matsubara, M. Tsukida, S. Yasuda, I. Ryu, J. Fluorine Chem. 129 (2008) 951â??954.

[8] X. Hao, A. Yoshida, J. Nishikido, Tetrahedron Lett. 46 (2005) 2697â??2700.

[9] H. Matsuda, A. Kitabatake, M. Kosuge, K. Kurihara, K. Tochigi, K. Ochi, Fluid Phase Equilib. 297 (2010) 187â??191.

[10] H. Matsuda, Y. Hirota, K. Kurihara, K. Tochigi, K. Ochi, Fluid Phase Equilib. 357 (2013) 71â??75.