Computational and experimental study of the interactions between ionic liquids and volatile organic compounds

Abstract

Computational chemistry calculations were performed to investigate the interactions of ionic liquids with different classes of volatile organic compounds (VOCs), including alcohols, aldehydes, ketones, alkanes, alkenes, alkynes and aromatic compounds. At least one VOC was studied to represent each class. Initially, 1-butyl-3-methylimindazolium chloride (abbreviated as C(4)mimCl) was used as the test ionic liquid compound. Calculated interaction lengths between atoms in the ionic liquid and the VOC tested as well as thermodynamic data suggest that C(4)mimCl preferentially interacts with alcohols as compared to other classes of volatile organic compounds. The interactions of methanol with different kinds of ionic liquids, specifically 1-butyl-3-methylimidazolium bromine (C(4)mimBr) and 1-butyl-3-methylimidazolium tetrafluoroborate (C(4)mimBF(4)) were also studied. In comparing C(4)mimCl, C(4)mimBr, and C(4)mimBF(4), the computational results suggest that C(4)mimCl is more likely to interact with methanol. Laboratory experiments were performed to provide further evidence for the interaction between C(4)mimCl and different classes of VOCs. Fourier transform infrared spectroscopy was used to probe the ionic liquid surface before and after exposure to the VOCs that were tested. New spectral features were detected after exposure of C(4)mimCl to various alcohols. The new features are characteristic of the alcohols tested. No new IR features were detected after exposure of the C(4)mimCl to the aldehyde, ketone, alkane, alkene, alkyne or aromatic compounds studied. In addition, after exposing the C(4)mimCl to a multi-component mixture of various classes of compounds (including an alcohol), the only new peaks that were detected were characteristic of the alcohol that was tested. These experimental results demonstrated that C(4)mimCl is selective to alcohols, even in complex mixtures. The findings in this work provide information for future gas-phase alcohol sensor design.

Hydrogen-bonding interactions between [BMIM][BF4] and acetonitrile

“…13,14 Furthermore, the properties, such as polarity, hydrophobicity, and electrochemical behavior of ILs can be adjusted over a much wider range by the addition of various molecular solvents. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] A great body of experimental and theoretical investigations has revealed the important roles of hydrogen-bonding interactions in pure ILs and in the mixtures of ILs and cosolvent. 18−40 Among various interactions, undoubtedly, electrostatic interaction is the most important one.…”

COSMO‐RS based ionic liquid screening for the separation of acetonitrile and ethanol azeotropic mixture

“…The efficiency of ILs depends upon the non‐covalent interactions between ILs and the solvents, and this result has been verified in the literature . For the study of intermolecular interactions, Keinan et al .…”

“…[27][28][29] The efficiency of ILs depends upon the non-covalent interactions between ILs and the solvents, and this result has been verified in the literature. [30][31][32][33][34][35] For the study of intermolecular interactions, Keinan et al 36 presented the reduced density gradient method based on properties of the electron density, which complements the conventional quantum-chemical theories of bonding, such as the atom in molecules (AIM) 37 and electron localization function (ELF). 38,39 This method can simultaneously analyze and provides an intuitive visualization of intermolecular non-covalent interaction types, particularly for weaker dispersion interaction.…”

Extractive distillation with the mixture of ionic liquid and solid inorganic salt as entrainers

“…To obtain the binding energy between water (or ethanol) and the entrainers, all optimized geometries were obtained by using the Gaussian 03 software package 50 at the M05-2X/ 6-31111G(d,p) level with the keyword "int 5 ultrafine," which has been previously used for studying the interactions between ILs and polar organic molecules. 51,52 The M05-2X functional is one of the newest DFT methods and is assumed to correctly reproduce weak interactions. 53 To obtain the most favorable clusters (composed of IL ions, KAc, water, and ethanol), harmonic frequency analysis calculations were performed to verify the optimized geometries to obtain the lowest energy points (no imaginary frequency) rather than local minima.…”