Maxwell-Stefan diffusion coefficient estimation for ternary systems: an ideal ternary alcohol system.

Area of Science:

• Physical Chemistry
• Chemical Engineering
• Materials Science

Background:

• The Maxwell-Stefan model is widely used for diffusion modeling but requires estimated diffusion coefficients.
• The Darken model estimates these coefficients but is primarily defined for binary systems.
• Extensions to ternary systems exist, notably by Krishna and van Baten, and Liu et al.

Purpose of the Study:

• To evaluate and compare two proposed multicomponent forms of the Darken model for ternary diffusion.
• To assess the accuracy of these models using experimental self-diffusion data.
• To determine the suitability of the multicomponent Darken model for rapid mutual diffusion estimation.

Main Methods:

• Experimental measurement of self-diffusion coefficients in methanol/butan-1-ol/propan-1-ol mixtures using pulsed gradient stimulated echo nuclear magnetic resonance (PGSTE-NMR).
• Utilizing experimental self-diffusion coefficients as input for the Darken model.
• Comparing model predictions with experimental mutual diffusion coefficients.

Main Results:

• Liu's model demonstrated superior prediction accuracy compared to Krishna and van Baten's model for the ideal ternary alcohol system.
• Despite improvements, Liu's model achieved an accuracy of only 26% for mutual diffusion coefficients.
• The study validated the use of PGSTE-NMR for obtaining essential self-diffusion data.

Conclusions:

• The multicomponent Darken model, when combined with PGSTE-NMR derived self-diffusion coefficients, offers a practical approach for estimating mutual diffusion in complex mixtures.
• This method presents an attractive alternative to computationally intensive molecular dynamics (MD) simulations for rapid diffusion estimations.
• Further refinement of the multicomponent Darken model may be necessary to improve prediction accuracy.