Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The diffusion coefficients of several ionic liquids based on the 1-alkyl-3-methylimidazolium cation, [CnC1Im], with chloride, tetrafluoroborate, and bis(trifluoromethanesulfonyl)imide, [Ntf2], anions were measured, using a Taylor dispersion technique, in three solvents (water, methanol, and acetonitrile) as a function of temperature between (283 and 333) K. The diffusion coefficients vary from 0.57 * 10-9 m2 * s-1 for 1-methyl-3- octylimidazolium bis(trifluoromethanesulfonyl)imide, [C8C1im][Ntf2], in water to 3.48 * 10-9 m2 * s-1 for 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C2C1im][Ntf2], in acetonitrile. In general, the diffusivities are lower for water, followed by methanol and acetonitrile, and decrease with an increase in the alkyl side chain of the imidazolium-based ionic liquids. These trends do not follow the Stokes-Einstein relation but can be explained by the solute-solvent interactions. The data were correlated using a modified Wilke-Chang equation in which a correction parameter was introduced. The correction parameter is independent of the temperature and is different for each solvent studied.