Ionic liquids (ILs) are defined as salts with a melting point below the boiling point of water. ILs are attractive due to their peculiar properties, such as their negligible vapor pressure. Interesting is the combination of ILs with carbon dioxide, because ILs are not soluble in CO₂, whereas CO₂ is very soluble in ILs. Supercritical fluids are defined as a fluid with a temperature above the critical temperature. Supercritical CO₂ (scCO₂) is inexpensive, nontoxic, nonpolluting, and easily removable hence it is widely used as a cleaning, separation agent, or as a solvent. By changing the pressure and the temperature of the scCO₂, it is possible to tune the solvent power and to adjust it to the requirements of a specific application. Using both IL and scCO₂ in the same system offers broad possibilities for new chemical processes.

To fully understand these systems, many physical and chemical properties need to be acquired. Using in situ infrared and Raman spectroscopy, we can quantify both concentration and molecular interaction of binary systems [1] and ternary systems (ILs – water- CO₂). [2]

We also produced and used metallic nanoparticles in ILs for catalytic purposes. ILs are able to stabilise metal nanoparticles by forming a layer around them and those particles can be use in various catalytic reactions. In situ spectroscopy is then used to follow the kinetics of acetophenone hydrogenation and the subsequent kinetic of the extraction of the products using scCO₂. [3-4]

[1] Supercritical CO₂ / ionic liquid systems: What can we extract from infrared and Raman spectra? J.-M. Andanson, F. Jutz and A. Baiker, J. Phys. Chem. B 2009, 113(30) 10249–10254

[2] Investigation of Binary and Ternary Systems of Ionic Liquids with Water and/or Supercritical CO₂ by In Situ Attenuated Total Reflection Infrared Spectroscopy, J.-M. Andanson, F. Jutz and A. Baiker, J. Phys. Chem. B, in press DOI:10.1021/jp911403s

[3] A green pathway for hydrogenations on ionic liquid stabilized nanoparticles, F. Jutz, J.-M. Andanson and A. Baiker, J. Catal., 2009, 268(2) 356-366

[4] in situ monitoring of a complex catalytic reaction network at high pressure by attenuated total reflection Fourier transform infrared spectroscopy, J.-M. Andanson, F. Jutz and A. Baiker, Applied spectroscopy, in press