Significant statement
The article opens the topic of utilization of supported ionic liquid membranes (SILMs) in gas separations. The ionic liquids seem to be good materials for gas membrane separation due to their low volatility and good gas solubility and diffusivity. They are also temperature stable and have very low chemical reactivity. Although the gas separation by supported ionic liquid membranes is widely studied topic, there is still no practical application. One of the reasons probably is that it is really hard to predict the gas transport properties of the supported ionic liquid membranes. Usually the solution diffusion model is applied on the gas transport through the supported ionic liquid membranes. It is possible to find some models to estimate solubility of gases in ionic liquids. The situation is worse with models suitable for prediction of diffusivity of gases in ionic liquids. However if both these problems were solved, the influence of the support on the transport properties also has to be taken into an account. Therefore permeabilities of two different supported ionic liquid membranes were measured and the results were compared with permeabilities calculated using two different models of the solubility of gases in ionic liquids, and one available model of diffusivity of gases in ionic liquids taking into an account also the porosity and the tortuosity of the membrane support. Besides that a model of mass transfer coefficient of mixed gases through the used supported ionic liquid membranes based on pure gas permeabilities was developed. It was found that it was not possible to predict the gas permeability through the supported ionic liquid membranes using available models of the solubility and diffusivity of the gases on the ionic liquid. A common approach to the porosity and the tortuosity of the supporting material without a great overestimation of these values or in the other words it was not possible to get reasonable agreements with experimental data. It was also found that pure gas permeabilities cannot be easily converted to mixed gas mass transfer coefficients. The Robeson plot was presented in the article, which showed that supported ionic liquid membranes are doing quite well in gas separation properties. Unfortunately there is a lack of possibilities how to predict gas transport properties of a specifically SILM knowing only the ionic liquid, the supporting material and the separated gas mixture, what was proven in this article. The supported ionic liquid membranes cannot be practically applied on gas separations until this problem is solved.
Journal Reference
Separation and Purification Technology, Volume 118, 2013, Pages 255–263.
Magda Kárászováa, Miroslav Simcika, Karel Friessb, Alena Randováb, Johannes C. Jansenc, Marek C. Ruzickaa, Zuzana Sedlákováa, Pavel Izaka, d,
a Institute of Chemical Process Fundamentals of the AS CR, Rozvojová 135, 165 02 Prague 6, Czech Republic.
b Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 160 00 Prague 6, Czech Republic.
c Institute on Membrane Technology, ITM–CNR, via P. Bucci, c/o University of Calabria, Cubo 17/C, 87036 Rende (CS), Italy.
d Research Institute of Inorganic Chemistry, Revoluční 1521, 400 01 Ústí nad Labem, Czech Republic.
ABSTRACT
Successful practical application of ionic liquid (IL) membranes requires good understanding of their basic transport properties and the role of the IL itself and its polymeric support. Within this work, two approaches to the calculation of mass transfer coefficients of gases in supported ionic liquid membranes were applied. The first one applies the models and data reported on diffusivity and solubility of gases in pure ionic liquids in the literature, in combination with porosity and tortuosity of the support. The second one is based on fitting of experimental data obtained from two ionic liquid membranes. The results of both approaches were compared and used to predict the properties of ionic liquid membranes. It was found that the model based on data of pure liquids overestimated the mass transfer coefficient significantly.
Go To Journal
Advances in Engineering Advances in Engineering features breaking research judged by Advances in Engineering advisory team to be of key importance in the Engineering field. Papers are selected from over 10,000 published each week from most peer reviewed journals.
