Hydrogen Bond Kinetics, Ionic Dynamics, and Voids in the Binary Mixtures of Protic Ionic Liquids with Alkanolamines

Abstract

Classical molecular dynamics simulations were used to investigate the structural and dynamical properties of the mixtures of ionic liquids (ILs) with the conjugate forms of the cation in a 1:1 molar ratio. The experimental studies suggested the combination of ethanolamines and ILs as novel absorbents for acidic gases such as CO2 and H2S, which provide the advantage of efficient absorption of gases at low pressures. However, the microscopic properties of the ionic mixtures are not studied. From our computational investigations, the densities of mixtures are reported and compared with the experimental results. The structural evolution of mixtures is reported by radial distribution functions, coordination numbers, void analysis, and spatial distribution functions. The mixtures’ dynamic properties were studied by analyzing the hydrogen bond, ion-pair, and ion-cage lifetimes of the system. Monoethanolammonium and triethanolammonium ILs show different types of spatial distribution functions. The cations have lesser effect on dynamics compared with anions. The charge on the anion greatly affects the dynamics of mixtures. The dianion mixtures show slower dynamics than the monoanionic mixtures. The hydrogen bonding between cations and anions is stronger than that between cations and neutral molecules due to strong coulombic attractive forces. The cations spend more time around the dianions as compared to monoanions. The distributions of voids show that the void sizes are smaller in triethanolamine-based mixtures. The sulfobenzoate-based mixtures show voids smaller than those of pyridine-3-carboxylate-based mixtures due to more available free space between the entities, which facilitates the overall dynamics.

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“…Based on the activation energy barrier of the rate-determining step, the optimal reaction route was obtained . Reddy et al . investigated the structural and kinetic properties of conjugated cationic liquid mixtures using MD simulations.…”

“…Based on the activation energy barrier of the rate-determining step, the optimal reaction route was obtained. 2 Reddy et al 23 investigated the structural and kinetic properties of conjugated cationic liquid mixtures using MD simulations. The structural evolution of the mixtures was represented by radial distribution function (RDF), coordination number, void analysis, and spatial distribution function (SDF).…”

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