Green processing using ionic liquids and CO 2

• Published in: Nature (London) Vol. 399; no. 6731; pp. 28 - 29
• Main Authors: Blanchard, Lynnette A, Hancu, Dan, Beckman, Eric J, Brennecke, Joan F
• Format: Journal Article
• Language: English
• Published: 06.05.1999
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/19887

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 pressure, can be used as environmentally benign media for a range of industrially important chemical processes, despite uncertainties about thermal stability and sensitivity to oxygen and water. It is difficult to recover products, however, as extraction with water 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 pollution. 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.