Fick Diffusion Coefficients in Binary Liquid Mixtures Containing Alkanes, Aromatics, Alcohols, or Acetone by Using Dynamic Light Scattering

This work reports Fick diffusion coefficients D11 and thermal diffusivities a in binary liquid mixtures containing cyclohexane, n-decane, n-heptane, toluene, isobutylbenzene, 1-methylnaphthalene, methanol, ethanol, or acetone. The mixtures are investigated by dynamic light scattering at temperatures T = 298, 348, and 423 K close to saturation conditions. Besides equimolar composition, toluene-based binary mixtures with methanol, ethanol, or cyclohexane are investigated at toluene mole fractions between 0.1 and 0.9. The average relative expanded experimental uncertainties (k = 2) for D11 and a are 5.3 and 8.3%. For the studied systems, the influence of molecular characteristics on the diffusivities as a function of T and composition is discussed. While D11 clearly depends on the molecular structure of the mixture components, i.e., alkane chain length, aliphatic or aromatic rings, or hydroxyl and carbonyl functional groups, such relationships were not resolvable for a within the experimental uncertainties. For mixtures containing the polar species methanol, ethanol, or acetone, an influence of hydrogen bonding on D11 was found. In general, the identified structure–property relationships agree with those reported in the literature for similar systems. Furthermore, a comparison of the present D11 and a data with corresponding literature data is performed.