Towards Fast Measurement of Multicomponent Diffusion Coefficients in Ionic Liquids
Advancing the chemical engineering fundamentals
Thermodynamics: General (T2-1e)
Keywords: multicomponent diffusion, ionic liquids, Raman spectroscopy, parameter estimation, experimental design
While transport properties play an important role in chemical reaction processes and separation problems, data on multicomponent mixtures are rare today. For ionic liquids, mutual diffusion data are available only for one binary mixture (Heintz, J. Chem. Thermodynamics 37:525–535, 2005). Established diffusion measurement methods are laborious and time consuming. To investigate a multicomponent system, several measurements have to be carried out due to the fact that univariate measurement techniques such as interferometry are applied. These techniques are not capable of resolving all components in a multicomponent mixture.
To overcome these problems, the authors have presented a novel method based on 1D Raman spectroscopy (Bardow et al., AIChE J., 49:323-334, 2003; 52:4004-4015, 2006.). This measurement technique allows for the simultaneous detection of all concentrations at 400 positions in a vertical diffusion cell with high temporal resolution. The additional application of model based methods for the design of optimal experiments and for efficient data analysis further reduces the experimental effort. It was shown that the method is capable of identifying multi-component diffusion coefficients from a single experiment. The method has already been applied to several systems of up to four components (Bardow et al., ESAT, 2005).
The novel method has a high potential for the analysis of ionic liquids. Salt diffusion coefficients can be measured in the existing diffusion cell. The high information content of the 1D Raman data further allows the analysis of dissociation effects. First ionic liquid systems have already been investigated. In this work, the novel measurement technique is introduced and extensions to electrolyte systems are described. Finally, first results for diffusion in ionic liquids will be presented.
Presented Tuesday 18, 16:00 to 16:20, in session Thermodynamics: General (T2-1e).
