Multi-scale Modeling of Structure, Dynamic and Thermodynamic Properties of Imidazolium-based Ionic Liquids: Ab initio DFT Calculations, Molecular Simulation and Equation of State Predictions

I G Economou,A A Vanin,J Ramos,E K Karakatsani,G.-E Logotheti

doi:10.2516/ogst:2008007

Abstract

Ionic liquids have received considerable attention by the chemical industry in recent years, mostly towards the development of environmentally benign processes. In this work, microscopic structure, dynamic and thermodynamic properties of imidazolium-based ionic liquids are calculated using theoretical models that cover a wide range of length and time scales, from ab initio density functional theory (DFT) calculations to atomistic molecular simulation and finally to a macroscopic equation of state based on perturbation theory. Different ionic liquids and polar solvents are examined and calculations are performed over a wide range of conditions. Model calculations are compared against literature experimental data. In all cases, the agreement between experiment and calculations/theory is very good. Thus, it is verified that carefully selected models can be used for reliable estimation of properties, even in the absence of experimental measurements.

Highlights

Over the last decade, ionic liquids (ILs) have received much attention for use as environmentally benign reaction and separation media [1,2,3,4]
ILs are molten salts with melting points close to room temperature. Their most remarkable property is that their vapor pressure is negligibly small, which means that ILs are non-volatile, non-flammable and odorless
It is expected that ILs may revolutionize the chemical process industry in the years to come

Summary

INTRODUCTION

Ionic liquids (ILs) have received much attention for use as environmentally benign reaction and separation media [1,2,3,4]. Early molecular simulation studies focused on the development of accurate quantum mechanics derived force-fields and their validation towards the prediction of structure and thermodynamic properties of ILs in melt [24,25,26]. Both all-atom and united-atom models were used. IG Economou et al / Multi-scale Modeling of Structure, Dynamic and Thermodynamic Properties of Imidazolium-based 285 Ionic Liquids: Ab initio DFT Calculations, Molecular Simulation and Equation of State Predictions. The agreement between calculations and experiments is, in general, very good

AB INITIO DFT CALCULATIONS

MOLECULAR SIMULATION DETAILS

Electrostatic Potential of Single Ions

Molecular Simulation