The distillation and volatility of ionic liquids

Martyn J. Earle, José M. S. S. Esperança, Manuela A. Gilea, José N. Canongia Lopes, Luís P. N. Rebelo, Joseph W. Magee, Kenneth R. Seddon, Jason A. Widegren

Research output: Contribution to journalArticlepeer-review

1733 Citations (Scopus)


It is widely believed that a defining characteristic of ionic liquids (or low-temperature molten salts) is that they exert no measurable vapour pressure, and hence cannot be distilled1,2. Here we demonstrate that this is unfounded, and that many ionic liquids can be distilled at low pressure without decomposition. Ionic liquids represent matter solely composed of ions, and so are perceived as non-volatile substances. During the last decade, interest in the field of ionic liquids has burgeoned3, producing a wealth of intellectual and technological challenges and opportunities for the production of new chemical and extractive processes4-6, fuel cells and batteries7, and new composite materials8,9. Much of this potential is underpinned by their presumed involatility. This characteristic, however, can severely restrict the attainability of high purity levels for ionic liquids (when they contain poorly volatile components) in recycling schemes, as well as excluding their use in gas-phase processes. We anticipate that our demonstration that some selected families of commonly used aprotic ionic liquids can be distilled at 200-300°C and low pressure, with concomitant recovery of significant amounts of pure substance, will permit these currently excluded applications to be realized.

Original languageEnglish
Pages (from-to)831-834
Number of pages4
Issue number7078
Publication statusPublished - 16 Feb 2006


  • Ionic liquids
  • Binary mixtures
  • Pure ionic


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