Fluid phase behaviour of ionic liquid-based systems of interest for green processes: Measurements and modelling

Fluid phase behaviour of ionic liquid-based systems of interest for green processes: Measurements and modelling

Kühne, E.

Witkamp, G.J. (promotor)
Peters, C.J. (promotor)

Mechanical Maritime and Materials Engineering

2008-06-04

In the last decades a large number of applications with ionic liquids (IL) have emerged, and since the discovery that carbon dioxide can tune the miscibility of IL+organic mixtures, special attention has been drawn to the use of IL and CO2 as combined solvents for synthesis and extractions. To evaluate the applicability of the miscibility switch in different systems, this thesis presents the investigation of phase diagrams of ternary systems based on the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (bmim[BF4]), carbon dioxide and different organic solutes. Four reactions of interest of the pharmaceutical and fine chemical industry, among them three hydrogenations, were selected as model reactions to provide the organic solutes used in phase behaviour measurements. Experiments were carried out in the Cailletet apparatus with CO2 composition varying from 10 mol% up to 70 mol%. For measurements performed with CO2 compositions up to 50 mol% and under the experimental conditions of this work, mostly liquid-vapour phase boundaries were found. For CO2 compositions above 50 mol%, the complexity of the phase diagrams increased significantly and not only liquid-vapour but also liquid-liquid phase transitions were found, as well as a very narrow three-phase region L1L2V was detected. The effect of CO2 composition in the location and extension of the homogeneous liquid phase has been also investigated. Additionally to experimental data collection, the potential of using the Group Contribution Equation of State for modelling the phase diagrams obtained in this work has been studied. Very good agreement has been found for L+V->L as well as L1+L2->L phase transitions. According to the results presented in this thesis, the GC-EOS can be considered suitable for prediction of phase equilibria in ternary systems based on an ionic liquid and carbon dioxide.

ionic liquid
carbon dioxide
phase behaviour
phase diagram

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978-90-9023156-3

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doctoral thesis

(c) 2008 E. Kühne