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.