☆ 4.5 Article

Surface tensions of ionic liquids: Non-regular trend along the number of cyano groups

FLUID PHASE EQUILIBRIA (2016)

Journal

FLUID PHASE EQUILIBRIA

Volume 409, Issue -, Pages 458-465

Publisher

ELSEVIER

DOI: 10.1016/j.fluid.2015.10.044

Keywords

Surface tension; Ionic liquids; Imidazolium-based; Cyano-based Surface entropy; Surface enthalpy; Critical temperature; COSMO-RS

Funding

national funds through FCT/MEC [FCT UID /CTM /50011/2013]
FEDER
FCT [SFRH/BD/88369/2012, SFRH/BPD/82264/2011]
European Research Council under European Union / ERC [337753]
Fundação para a Ciência e a Tecnologia [SFRH/BD/88369/2012] Funding Source: FCT
European Research Council (ERC) [337753] Funding Source: European Research Council (ERC)

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Abstract

Ionic liquids (ILs) with cyano-functionalized anions are a set of fluids that are still poorly characterized despite their remarkably low viscosities and potential applications. Aiming at providing a comprehensive study on the influence of the number of -CN groups through the surface tension and surface organization of ILs, the surface tensions of imidazolium-based ILs with cyano-functionalized anions were determined at atmospheric pressure and in the (298.15-343.15) K temperature range. The ILs investigated are based on 1-alkyl-3-methylimidazolium cations (alkyl = ethyl, butyl and hexyl) combined with the [SCN](-), [N(CN)(2)](-), [C(CN)(3)](-) and [B(CN)(4)](-) anions. Although the well-known trend regarding the surface tension decrease with the increase of the size of the aliphatic moiety at the cation was observed, the order obtained for the anions is more intricate. For a common cation and at a given temperature, the surface tension decreases according to: [N(CN)(2)](-) > [SCN](-) > [C(CN)(3)](-) > [B(CN)(4)](-). Therefore, the surface tension of this homologous series does not decrease with the increase of the number of -CN groups at the anion as has been previously shown by studies performed with a more limited matrix of ILs. A maximum in the surface tension and critical temperature was observed for [N(CN)2]-based ILs. Furthermore, a minimum in the surface entropy, indicative of a highly structured surface, was found for the same class of ILs. All these evidences seem to be a result of stronger hydrogen-bonding interactions occurring in [N(CN)(2)]-based ILs, when compared with the remaining CN-based counterparts, and as sustained by cation-anion interaction energies derived from the Conductor Like Screening Model for Real Solvents (COSMO-RS). (C) 2015 Elsevier B.V. All rights reserved.

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Oil acidity reduction by extraction with imidazolium ionic liquids: Experimental, COSMO description and reutilization study

Baudilio Coto, Inmaculada Suarez, Maria Jose Tenorio, Sandra Nieto, Nieves Alvarez, Jose Luis Pena

Summary: In this study, reduction of crude oil acidity through the use of ionic liquids (ILs) was investigated, showing up to 50% reduction in TAN under certain conditions. However, challenges such as increased IL acidity and decreased extraction efficiency were observed, impacting the feasibility of IL reuse. Modeling with COSMO-RS provided insights into IL characterization and the effects of temperature on TAN reduction.

SEPARATION AND PURIFICATION TECHNOLOGY (2021)