Supported ionic liquid membranes

Ionic liquids are salts with a melting point below 100 °C. They possess unique properties: while their vapour pressure is extremely low, their chemical and thermal stability is very high. The possibility to combine a large variety of anions and cations allows for designing liquids with tailor-made properties for various applications.

For instance ionic liquids are able to solve a large amount of carbon dioxide, while the solubility of other gases like nitrogen or carbon monoxide is low. Therefore ionic liquids can be used as absorbers or in supported liquid membranes to separate gases. Due to their low volatility there is no loss of the liquids as it is the case with amine scrubbers and the membranes will not dry out. The investigation of structure-property relationship is the base to understand the interaction and to come to tailor-made solutions.

Possible applications

  • Separation of the green house gas CO2 from coal-fired power station as an alternative to the amine scrubbing process
  • Cleaning of biogas
  • Membrane reactors

In the field of ionic liquids we are working both on the development of absorption processes for gases (Fig. 1) and the supported ionic liquid membrane (SILM, Fig. 2).In addition we are developing methods for the recycling of ionic liquids based on membrane processes.

Physisorption of CO2 in different Ionic Liquids at 60°C.
© Fraunhofer IGB
Fig. 1: Physisorption of CO2 in different Ionic Liquids at 60°C.
Supported ionic liquid membrane (SILM).
© Fraunhofer IGB
Fig. 2: Carrier-supported membrane based on ionic liquids (Supported ionic liquid membrane, SILM).


  • Blath, J., et al. (2011). "Gas solubilities in room temperature ionic liquids – Correlation between RTiL-molar mass and Henry's law constant." Chemical Engineering Journal 172(1): 167-176.
  • Blath, J., et al. (2012). "Chemisorption of carbon dioxide in imidazolium based ionic liquids with carboxylic anions." Chemical Engineering Journal 181–182: 152-158.