Solubility of Species in Ionic Liquids

The solubility of a reactant in an ionic liquid affects the performance of the ionic liquid as a catalyst and that of a catalyst dispersed in an ionic liquid. However, there are only a few reports about the solubilities of species in ionic liquid media. The solubility values of typical molecules of interest, as described below, are based on a limited number of reports. 

Oxygen. The solubility of O2 in [BMIM]PF6 is very low, 0.2mmol/L, much lower than that of O2 in CH3CN (9.1 mmol/L) (83). 

Carbon Monoxide. The solubility of CO in ionic liquids is crucial for car-bonylation reactions. However, quantitative measurements are not yet available. In 

Carbon Dioxide and Lower Alkanes. Carbon dioxide has a remarkably high solubility in ionic liquids (22). For example, about 0.5 mol fraction of CO2 was present in [BMIMJPFg at 40°C and 50 bar, although the total volume increased by only 10% as a result of the CO2 addition. 

Brennecke et al. (22) compared the Henry s law constants of several gases in [BMIMJPFe with those in toluene and methanol. The results (Fig. 9) show that CO2 has a much higher solubility in the ionic liquid than in the organic solvent. 

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