Journal of Chemical and Engineering Data, Vol.65, No.3, 1068-1082, 2020
Diffusivities of Binary Mixtures Consisting of Carbon Dioxide, Methane, and Propane by Dynamic Light Scattering
In the present contribution, diffusivities of binary mixtures of propane (C3H8), carbon dioxide (CO2), and methane (CH4) were investigated between T = (293 and 353) K, p = (0.5 and 12) MPa, and mole fractions x = (0.0833 and 0.917) by dynamic light scattering ( DLS). Which diffusivities are accessible by DLS depends on the location of the thermodynamic state points studied relative to the phase envelopes of the mixtures, the mixture density, and the derivatives of the refractive index with respect to temperature and concentration. A simultaneous determination of thermal and mutual diffusivity was possible in the liquid phases and at some higher-density states in the supercritical phase. For the gaseous and most of the supercritical state points, only a thermal, mutual, or effective diffusivity could be obtained and was identified with the help of Rayleigh ratios and temperature-, pressure-, and concentration-dependent trends. The reported diffusivities clearly improve the data situation for the mixtures studied above atmospheric pressure. The average expanded uncertainty (k = 2) for all presented mutual diffusivities is 5.8%. For the thermal diffusivity, these uncertainties are 22% and 3.0% for the cases where it was determined simultaneously with the mutual diffusivity or alone.