(375e) Molecular Simulations of Protic Ionic Liquids and Their Mixtures with Water

Protic ionic liquids are considered as a potential green solvent substitutes for volatile solvents. In this project, we have performed a systematic molecular simulation study of the alkylammonium nitrates (AANs) including ethylammonium nitrate, propylammonium nitrate and butylammonium nitrate to examine their application as hydrogen-bonded solvents that form three-dimensional networks similar to water. Replica exchange molecular dynamics (REMD) simulations were performed over the temperature range from 270K to 600K at atmospheric pressure of AAN mixtures with water. The temperature dependent excess chemical potentials of methane dissolved in pure AANs and AAN mixtures were determined by means of Widom test particle insertion. The solvation free energies were broken down into entropic and enthalpic contributions by fitting the solvation free energies to thermodynamic expansions to compare the solvation properties of nonpolar solutes in AANs to those in water. Densities of pure AANs over the simulate temperature range show good agreement with the experiment data. Besides REMD simulations of mixtures, the AANs and water mixtures with different mole fractions are simulated at 300K. The partial molar volumes and x-ray scattering structures of the AANs are also studied.