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Isobutane as a probe of the structure of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids

•The solubility of isobutane was determined in [CnC1Im][NTf2] (n=2, 4, 6, 8 and 10).•Iso-C4H10 solubility decreases with T and increases with n to reach x=0.1 (n=10, T=303K).•Isobutane is, on average, 1.6 times less soluble than n-butane in this family of ionic liquids.•Solubility increase with n is...

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Published in:The Journal of chemical thermodynamics 2015-10, Vol.89, p.98-103
Main Authors: Pison, Laure, Bernales, Varinia, Fuentealba, Patricio, Padua, Agilio A.H., Costa Gomes, Margarida F.
Format: Article
Language:English
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Summary:•The solubility of isobutane was determined in [CnC1Im][NTf2] (n=2, 4, 6, 8 and 10).•Iso-C4H10 solubility decreases with T and increases with n to reach x=0.1 (n=10, T=303K).•Isobutane is, on average, 1.6 times less soluble than n-butane in this family of ionic liquids.•Solubility increase with n is due to a more negative enthalpy of dissolution (n⩾6). An experimental study of the solubility and of the thermodynamic properties of solvation, between temperatures (303 and 343)K and at pressures close to atmospheric, of 2-methylpropane (isobutane) in several ionic liquids based on the bis(trifluoromethylsulfonyl)imide anion and on 1-alkyl-3-methylimidazolium cations, [CnC1Im][NTf2], with alkyl side-chains varying from two to ten carbon atoms is presented. The isobutane solubility increases with increasing size of the alkyl side-chain of the cation in the ionic liquid and decreases with increasing temperature (as typical of an exothermal dissolution process). The mole fraction solubility of isobutane varies from 0.904·10−2 in [C2C1Im][NTf2] at T=343K to 1.002·10−1 in [C10C1Im][NTf2] at T=303K. The values measured in this work are compared to the behaviour of n-butane in the same ionic liquids published in a previous study (Costa Gomes et al., 2012). Isobutane was found to be significantly less soluble than n-butane in all the ionic liquids. The differences found are interpreted in relation to the molecular structures obtained by molecular dynamics simulations for the solutions of n-butane and isobutane in the studied [CnC1Im][NTf2] ionic liquids.
ISSN:0021-9614
1096-3626
DOI:10.1016/j.jct.2015.04.026