Molecular Simulation of Mixtures Containing Imidazolium- and Pyridinium-fJased Ionic Liquidsand 1-Butanol

摘要

A molecular simulation study of mixtures containing 1-butanol and various imidazolium and pyridinium-based ionic liquids that form liquid-liquid equilibrium is reported. Solutions of 1-butanol and l-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), l-n-butyl-3-methylimidazolium bis(trifluoro-methane-sulfonyl) imide ([bmim][Tf2N]), l-n-butyl-3-methyl-pyridinium tetrafluoroborate ([bmpy][BF4]), and 1-n-butyl-3-methylpyridinium bis(trifluoromethane-sulfonyl) imide ([bmpy][Tf2N]) are examined using isothermal-isobar ic molecular dynamics simulations, Quantities computed include molar volumes, self-diffusivities, radial distribution functions, local composition functions, and interaction energies, The simulations help explain recent experimental results in which [bmpy][BF4] was found to have a lower upper critical solution temperature (UCST) with 1-butanol than [bmim][BF4]. This is due to weaker cation/anion association in the [bmpy] mixture, which in turn allows stronger alcohol/anion and alcohol/cation association in this system relative to [bmim][BF4j. The simulations also help explain why [bmim][Tf2N] has a lower UCST with 1-butanol than [bmpy][Tf2N]. This behavior is attributed to weak cation/anion association in both systems and a stronger alcohol/cation interaction with the [bmim] cation relative to the [bmpy] cation.