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Green processing using ionic liquids and CO2

Nature volume 399, pages 28–29 (1999)Cite this article

Abstract

Many organic solvents evaporate into the atmosphere with detrimental effects on the environment and human health. But room-temperature ionic liquids, with low viscosity and no measurable vapour pressure1, can be used as environmentally benign media for a range of industrially important chemical processes2,3,4,5,6, despite uncertainties about thermal stability and sensitivity to oxygen and water. It is difficult to recover products, however, as extraction with water7 works only for hydrophilic products, distillation is not suitable for poorly volatile or thermally labile products, and liquid-liquid extraction using organic solvents results in cross-contamination. We find that non-volatile organic compounds can be extracted from ionic liquids using supercritical carbon dioxide, which is widely used to extract large organic compounds with minimal pollution8. Carbon dioxide dissolves in the liquid to facilitate extraction, but the ionic liquid does not dissolve in carbon dioxide, so pure product can be recovered.

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Figure 1: Phase diagram for the CO2-[BMIM][PF6] system.
Figure 2: Extraction of naphthalene from the naphthalene/[BMIM][PF6] mixture using CO2at 40 °C and 13.8 MPa.

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Authors and Affiliations

  1. Department of Chemical Engineering, University of Notre Dame, Notre Dame, 46556, Indiana, USA

    Lynnette A. Blanchard & Joan F. Brennecke

  2. Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, 15261, Pennsylvania, USA

    Dan Hancu & Eric J. Beckman

Authors
  1. Lynnette A. Blanchard
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  2. Dan Hancu
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  3. Eric J. Beckman
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  4. Joan F. Brennecke
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Blanchard, L., Hancu, D., Beckman, E. et al. Green processing using ionic liquids and CO2. Nature 399, 28–29 (1999). https://doi.org/10.1038/19887

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