Free volume as the basis of gas solubility and selectivity in imidazolium - based ionic liquids / Matthew S. Shannon in Industrial & engineering chemistry research, Vol. 51 N° 15 (Avril 2012)  

Free volume as the basis of gas solubility and selectivity in imidazolium - based ionic liquids [texte imprimé] / Matthew S. Shannon, Auteur ; Jason M. Tedstone, Auteur ; Scott P. O. Danielsen, Auteur . - 2012 . - pp. 5565-5576.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 51 N° 15 (Avril 2012) . - pp. 5565-5576

Mots-clés :	Ionic liquid Solubility Free volume
Résumé :	While molar volume-based models for gas solubility in ionic liquids (ILs) have been proposed, free volume within the IL can be shown to be the underlying property driving gas solubility and selectivity. Previously published observations as to the distinct differences in solubility trends for gases such as CH4 and N2 relative to CO2 in systematically varied ILs can be attributed to positive and negative effects arising from increasing free volume with increasing alkyl chain length. Through the use of COSMOtherm as a powerful and rapid tool to calculate free volumes in 165 existing and theoretical 1-n-alkyl-3- methylimidazolium ([Cnmim][X]) ILs, a previously unreported, yet speculated, critical underlying relationship between gas solubility in ILs is herein described These results build upon previous assertions that Regular Solution Theory is applicable to imidazolium-based ILs, which appeared to indicate that a global maximum had already been observed for CO2 solubility in imidazolium-based ILs. However, the findings of this computational study suggest that the perceived maximum in CO2 solubility might be exceeded through rational design of ILs. We observe that although Henry's constants in ILs are dependent on the inverse of molar volume and free volume, the volume-normalized solubility of CH4 and N2 are proportional to free volume, while CO2 is inversely proportional to the square root of free volume. Our free volume model is compared to experimental data for CO2/CH4 and CO2/N2 selectivity, and a nearly identical plot of selectivity relative to IL molar volume can be generated from the computational method alone. The overall implication is that large, highly delocalized anions paired with imidazolium cations that have minimally sized alkyl chains may hold the key to achieving greater CO2 solubility and selectivity in ILs.
ISSN :	0888-5885
En ligne :	http://cat.inist.fr/?aModele=afficheN&cpsidt=25815836