Mixed Matrix Membranes Based On PVDF-Co-HFP/RTIL Systems

Composite Membranes Based on PVDF-co-HFP/RTIL Systems

Matthew G. Cowan, William McDanel, Douglas L. Gin, Richard D. Noble

Recently, composite membranes comprised of poly(vinylidene fluoride-co-hexafluoro-propylene) (PVDF-co-HFP) and room-temperature ionic liquids (RTILs) have been reported in the literature [1-3]. These composite membranes are easily prepared, maintain good mechanical strength, and allow RTIL loadings of up to 80 wt%. In particular, the high loading of RTIL provides favorable gas transport and separation properties for a range of gas pairs. Having identified this system as a versatile platform for the preparation of composite membranes, we have focused on the incorporation of a third component to adapt the membrane properties to a specific gas separation task. Compatibility of the system with these additional components can be achieved by appropriate choice of the functionality included in the RTILs.

Facilitated transport agents (FTAs) are molecules or materials with functionality capable of reversibly binding gases of interest. In this way, they allow for faster transport of the desired gas into and out of the membrane, effectively increasing the permeability of that gas across the membrane. For the separation of carbon dioxide from nitrogen, we have investigated the low-molecular-weight, non-volatile tertiary amine DABCO and comparatively high-molecular-weight poly(amido amine) (PAMAM) dendrimers that contain both primary and secondary amines. Separately, stable, robust, metal complexes containing cobalt(II) and cobalt(III) have been also been incorporated and investigated in RTIL-based membranes in an effort to separate oxygen/nitrogen and olefin/paraffin gas pairs, respectively. Finally, the incorporation of microporous frameworks into RTIL-based composite membranes have been investigated as as a means of providing faster diffusion pathways for select gases based on pore size or surface functionality. We have investigated organic cages [4] for the separation of carbon dioxide and nitrogen and the zeolitic framework SAPO-34 for enhancement of ethene/ethane separation.

In this presentation, we describe methods for the preparation of these membranes and the effectiveness of the various composite membrane materials we have investigated to date.

1. Hong, S. U., Park, D., Ko, Y., Baek, I. Chem. Commun., 2009, 7227–7229.
2. Jansen, J. C., Friess, K., Clarizia, Schauer, J., Izák, P. Macromolecules 2011, 39–45.
3. Friess, K., Jansen, J. C., Bazzarelli, Izák, P., Jarmarová, V., Kačírková, M., Schauer, J. Clarizia, G. Bernardo, P. J. of Memb. Sci. 2012, 801–809.
4. Jin, Y., Voss, B. A., Noble, R. D., Zhang, W. Angew. Chem. Int. Ed. 2010, 6348–6351.