Ternary diffusivities by model-based analysis of Raman spectroscopy measurements

Abstract:
Even though multicomponent mixtures are ubiquitous in mass transfer processes diffusion data in these systems is scarce. This is due to the fact that established diffusion measurements are laborious. In particular, several experiments are required to determine multicomponent diffusion coefficients at a single composition. In order to overcome these deficiencies a new diffusion experiment employing 1-D-Raman spectroscopy is presented. Concentrations of the individual species are resolved with high spatial and temporal resolution during the diffusion process. In this work, it is shown that this data allows determining the ternary Fick diffusion matrix from a single isothermal diffusion experiment. The experimental procedure is further optimized using model-based experimental design techniques. Thereby, precision of the diffusion measurements can be improved by an order of magnitude. The theoretical calculations are validated by experimental results for the system n-Propanol + 1-Chlorobutane + n-Heptane.

Keywords:
multicomponent diffusion, Raman spectroscopy, parameter estimation, experimental design, mass transfer

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