Diffusion coefficients of ternary mixtures of water, glucose, and dilute ethanol, methanol, or acetone by the Taylor dispersion method

The Taylor dispersion technique is used to determine the diffusion coefficients of the ternary systems glucose + water + dilute methanol, ethanol, or acetone at 25 °C and up to a glucose mole fraction of 0.065. The dispersion of the injected solutes is recorded by a differential refractometer and an ultraviolet-visible detector. The diffusion coefficients are calculated directly by fitting the theoretical dispersion equations to about six experimental curves simultaneously. The precision of the diffusion coefficients is dependent on the relative detector sensitivities of the components. The determination of the main-diffusion coefficients is more precise than of the cross-diffusion coefficient (±2% vs ±5-10%)

Molecular dynamics simulation of the Maxwell-Stefan diffusion coefficients in Lennard-Jones liquid mixtures

Maxwell-Stefan (MS) diffusion coefficients in multicomponent liquids have been determined by the equilibrium molecular dynamics calculation of the appropriate Green-Kubo equation. Simulations were performed for systems of 300 LJ particles at various compositions. The unary system was divided into three components by attaching a colour label to the particles, which plays no role in the dynamics. The binary system argon + krypton was divided into three species by attaching a colour label to the particles of argon. The ternary system consisted of argon, krypton and neon. The results of the calculation of the MS diffusion coefficients in the unary and binary systems agreed well with the literature values. The MS diffusion coefficients of the unary system did not differ significantly from the self-diffusion coefficient. The MS diffusion coefficients of the ternary system behaved as expected from other physical properties

Molecular dynamics simulation of self-diffusion and Maxwell-Stefan diffusion coefficients in liquid mixtures of methanol and water

Self-diffusion coefficients and Maxwell-Stefan diffusion coefficients in liquids have been determined by the equilibrium molecular dynamics calculation of the appropriate Green-Kubo equation. Simulations of water, methanol and mixtures of water and methanol have been carried out to calculate the diffusion coefficients at 300 K. In order to study the influence of the force field on the calculated self-diffusion coefficients of the pure liquids, two different force fields for each component have been used. The Van Leeuwen/Smit force field calculated the self-diffusion of methanol accurately. The SPC/E force field gave the best, but moderate, results for water. In mixtures of water and methanol the self-diffusion coefficients of both components were more accurate at high mole fractions of methanol. This can be explained by the better performance of the methanol force field. The Maxwell-Stefan diffusion coefficients in the mixtures of methanol and water agreed fairly well with the experimental values. More accurate results can be obtained by using optimised parameters in the water force field, and by enlarging the integration time and the duration of the simulation runs