NAMS 2002 Workshop - ICOM 2008

Gas Separation I – 2
Monday July 14, 10:15 AM-10:45 AM, Kaua’i
Tailor Made Polymeric Membrane Based on Segmented Block Copolymer
for CO2 Separation
A. Car (Speaker), University of Maribor, Faculty of Chemistry and Chemical Engineering,
Slovenia, anja.car@uni-mb.si
C. Stropnik, University of Maribor, Faculty of Chemistry and Chemical Engineering, Slovenia
W. Yave, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany
K. Peinemann, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH,
Germany
The use of polymers in applications that require control of gas transport is rapidly
growing. For many of them, it may be desirable to utilize heterogeneous polymer
blends or block copolymers in which one component provides desired
permeability characteristics, while the other improves material properties (e.g.,
modulus or impact strength). Heterogeneous block copolymers provide the
potential for creating new materials for applications with mechanical and
transport properties superior to those of the parent homopolymers. Morphological
features of microphase- separated block copolymers that can affect small
molecules transport, include the small size and narrow size distribution of
domains. Knowledge of the relationships between block copolymer morphology
and the diffusion and permeation processes is essential for successful
manufacturing and usage of heterogeneous polymers and their blends.
Poly(ethylene(oxide)-poly(butylene terephthalate) (PEO-PBT) multiblock
copolymers are found under the commercial name Polyactive®, and they are
considered as semicrystalline polymers [1] . In these copolymers, PEO block is the
permeable amorphous phase and PBT is the rigid crystalline phase, considered
as impermeable for gas transport [2, 3] .
This paper reports the design of a tailor made polymeric membrane by using
PEO-PBT multi- block copolymers. Their properties are controlled by the fraction
of PEO phase and its molecular weight, thus a structural manipulation in order to
obtain a material with desired transport properties is possible. From selected
PEO-PBT copolymers, blend membranes with PEG are tailored in order to
design membranes with high performance for CO2 separation. One focus of this
work was the development of a membrane material, which can effectively
separate CO2 and H2. This is an industrially important separation, e.g. for the
coal gasification process. Membranes with a preferred CO2-permeability are
especially attractive, because the hydrogen remains on the high-pressure side.
Blends of Polyactive® comprise 50 wt. % of PEG 200 were still mechanically
stable and showed a CO2/H2- solubility selectivity of 78. This was counteracted
by a CO2/H2-diffusivity selectivity of 0.17 (faster diffusion of hydrogen). The