NAMS 2002 Workshop - ICOM 2008

Pervaporation and Vapor Permeation II – 3
Thursday July 17, 3:30 PM-4:00 PM, Moloka’i
Ion-containing Polyimide Membranes: A Way of Overcoming the Trade-off
Permeability in Pervaporation ?
A. Jonquieres (Speaker), Nancy Universite, France - Anne.Jonquieres@ensic.inpl-nancy.fr
M. Awkal, Nancy Universite, France
R. Clement, Nancy Universite, France
P. Lochon, Nancy Universite, France
Two international patents [1,2] and also recent results [3] have shown that
polymeric membranes containing cationic groups are highly efficient for the
removal of protic species (e.g. alcohols) from organic mixtures by pervaporation,
with an important potential application for the purification of ethyl-tert-butyl ether
(ETBE). By appropriate fiscal privileges for the past ten years, the European
Union has been strongly inciting the large production of this alkyl ether from
agricultural ethanol. Thanks to its specific advantages and its much better
biodegradability than methyl-tert- butyl ether (MTBE), ETBE is currently
considered as one of the most promising bio-fuels [4,5]. Nevertheless, its
industrial synthesis process leads to an azeotropic mixture containing 20 wt % of
ethanol which has to be removed for ETBE purification. If the former polymer
membranes were well performing for this separation, the rather poor control of
their chemical structure did not allow any detailed analysis about the influence of
the cationic sites on their permeability.
Taking advantage of our former experience on polyimide copolymers for this
separation [6], we recently developed the synthesis and characterization of 3
families of new ion-containing polyimide copolymers, with a control of the number
of their cationic ammonium groups, the length of their alkyl side chain and the
type of their counter- ions [7,8]. In this new communication, the membranes
features of the 3 copolymer families will be discussed in terms of structureproperty
relationships on the basis of sorption and pervaporation results obtained
for the separation of the azeotropic mixture EtOH/ETBE. In particular, it will be
shown how simply changing the chemical structure of the cationic groups
enabled to increase sharply permeability with a very low impact on selectivity,
therefore overcoming the usual trade- off permeability/selectivity.
[1] H. Steinhauser, H. Brüschke, European Patent 0674940 B1 (1995).
[2] H. Steinhauser, H. Brüschke, US Patent 5,700,374 (1997).
[3] S. Touchal, D. Roizard, L. Perrin, Journal of Applied Polymer Science, Vol. 99 (2006) 3622.