Solubility of n-butane and 2-methylpropane (isobutane) in 1-alkyl-3-methylimidazolium-based ionic liquids with linear and branched alkyl side-chains.
The solubility of n-butane and 2-methylpropane (isobutane) in three ionic liquids - 1-(2-methylpropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [(2mC3)C1im][Ntf2], 1-(3-methylbutyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [(3mC4)C1im][Ntf2] and 1-methyl-3-pentylimidazolium bis(trifluoromethylsulfonyl)imide [C5C1im][Ntf2] - has been measured at atmospheric pressure from 303 to 343 K. Isobutane is less soluble than n-butane in all the ionic liquids. Henry's constant values range from 13.8 × 10(5) Pa for n-butane in [C5C1im][Ntf2] at 303 K to 64.5 × 10(5) Pa for isobutane in [(2mC3)C1im][Ntf2] at 343 K. The difference in solubility between the two gases can be explained by a more negative enthalpy of solvation for n-butane. A structural analysis of the pure solvents and of the solutions of the gases, probed by molecular dynamics simulations, could explain the differences found in the systems: (i) the nonpolar domains of the ionic liquids accommodate better the long and more flexible n-butane solute; (ii) the small differences in solubility of each gas in the ionic liquids with the same number of carbon atoms in the alkyl side-chains are explained by the absence of large structural differences in the pure solvents. In all cases, the structural analysis of the four ionic liquids confirms that the studied gases can act as probes of the molecular structure of the ionic liquids, the simulations being always compatible with the experimental solubility data.
Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, UMR 6296 CNRS, équipe Thermodynamique et Interactions Moléculaires, ICCF-TIM, BP 80026, F-63171 Aubière, France. Margarida.c.gomes@univ-bpclermont.fr.
Laure
L
Pison
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, 1049 001 Lisboa, Portugal.
Karina
K
Shimizu
Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
George
G
Tamas
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, 1049 001 Lisboa, Portugal and Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2580 157 Oeiras, Portugal.
José Nuno Canongia
JN
Lopes
Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
Edward L
EL
Quitevis
Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, UMR 6296 CNRS, équipe Thermodynamique et Interactions Moléculaires, ICCF-TIM, BP 80026, F-63171 Aubière, France. Margarida.c.gomes@univ-bpclermont.fr.
Margarida F Costa
MF
Gomes