Ternary diffusivities by model‐based analysis of Raman spectroscopy measurements

Abstract

in Wiley InterScience (www.interscience.wiley.com).Even though multicomponent mixtures are ubiquitous in mass transfer processes, mutual diffusion data in these systems are 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 diffusion experiment employing one-dimensional 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 these data allow determining the ternary Fick diffusion matrix from a single isothermal diffusion experiment. The experimental procedure is further optimized using model-based experimental design techniques, where general design guidelines for diffusion experiments are derived. 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 þ 1-chlorobutane þ n-heptane.

On the interpretation of ternary diffusion measurements in low-molecular weight fluids by dynamic light scattering

“…Thus, it seems that the use of conventional diffusion experiments such as Taylor dispersion and Gouy/Rayleigh interferometry [39] cannot be avoided for determination of the full diffusion matrix. Recent advantages in the use of spectroscopic measurement techniques hold the promise to provide easier access to multicomponent diffusion data [40][41][42]. These may then be complemented by DLS data near critical regions for which DLS measurements are invaluable.…”

Cross-diffusion and pattern formation in reaction–diffusion systems

“…The eluted peak, sometimes called the Taylor peak, is monitored by a suitable detector such as a flow-through spectrophotometer, refractive index detector (RID) or Raman spectrometer. 93,94 The diffusion coefficients are calculated from the parameters of the Gaussian functions that fit the eluted peak. A typical peak is shown in Fig.…”

Direct determination of the concentration dependence of diffusivities using combined model-based Raman and NMR experiments

“…Methods of optimum experimental design have shown [11][12][13] that it is advantageous to perform experiments in restricted diffusion, i.e. the diffusion front should reach the wall during the experiment.…”

“…A detailed description of the experimental setup was given by the authors in [11,12,14,23]. Here, the principle is briefly summarized.…”

“…For the determination of diffusion coefficients, a new efficient diffusion measurement technique has been developed recently [11,12]. It is based on 1D-Raman spectroscopy allowing for the determination of multi-component concentration profiles in a vertical diffusion cell.…”