Molecular versus ionic liquids: Development of a thermodynamic framework for predicting vaporization thermodynamics

Abstract

Ionic liquids based on the pyridinium and quinolinium cations show good result in desulfurization of fuels. The knowledge of their vaporisation thermodynamics is of practical importance. The standard molar enthalpies of vaporization of pyridinium based ionic liquids were derived from the vapor pressure temperature dependences measured by the quartz-crystal microbalance method. We have collected available primary experimental results on vapour pressures, and enthalpies of phase transitions (solid-solid, crystal-gas, and liquid-gas) of analogous molecular species – substituted pyridines and quinolines. These data were evaluated using the structure-property correlations. The consistent sets of evaluated thermodynamic data on the molecular and ionic liquids were used to develop the “centerpiece” based group-additivity method for predicting enthalpies of vaporization of molecular and ionic compounds. The general transferability of the contributions to the enthalpy of vaporization from the molecular liquids to the ionic liquid has been established.