title: Effect of unsaturation on the absorption of ethane and ethylene in imidazolium-based ionic liquids.
abstract: The influence of the presence of imidazolium side chain unsaturation on the solubility of ethane and ethylene was studied in three ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide-saturated alkyl side-chain in the cation; 1-methyl-3-(buten-3-yl)imidazolium bis(trifluorosulfonyl)imide-double bond in the side-chain of the cation; and 1-methyl-3-benzylimidazolium bis(trifluorosulfonyl)imide-benzyl group in the side-chain of the cation. The solubility of both gases decreases when the side-chain of the cations is functionalized with an unsaturated group. This can be explained by a less favorable enthalpy of solvation. The difference of solubility between ethane and ethylene can be explained from a balance of enthalpic and entropic factors: for the ionic liquid with the saturated alkyl side-chain and the benzyl-substituted side-chain, it is the favorable entropy of solvation that explains the larger ethylene solubility, whereas in the case of the saturated side-chain, it is the more favorable enthalpy of solvation. Molecular simulation allowed the identification of the mechanisms of solvation and the preferential solvation sites for each gas in the different ionic liquids. Simulations have shown that the entropy of solvation is more favorable when the presence of the gas weakens the cation-anion interactions or when the gas can be solvated near different sites of the ionic liquid.
authors.affiliation: 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.
authors.forename: Leila
authors.initials: L
authors.lastname: Moura
authors.forename: Manas
authors.initials: M
authors.lastname: Mishra
authors.forename: Varinia
authors.initials: V
authors.lastname: Bernales
authors.forename: Patricio
authors.initials: P
authors.lastname: Fuentealba
authors.forename: Agilio A H
authors.initials: AA
authors.lastname: Padua
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Santini
authors.forename: Margarida F
authors.initials: MF
authors.lastname: Costa Gomes
mesh_terms: D004980:Ethane / Q000737:chemistry*; D005030:Ethylenes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D014783:Viscosity
chemical_list: D005030:Ethylenes; D007093:Imidazoles; D052578:Ionic Liquids; C036216:ethylene; D004980:Ethane