Membranes - Introduction to Carbon Capture and Sequestration - page 330

Box 7.5.1 Membranes with facilitated transport
One of the experimental strategies to overcome the Robeson upper limit in polymer
materials is to use facilitated transport. We have seen that the idea of facilitated
transport is that the CO 2 in the gas mixture reacts with the membrane. Because of
the chemical reaction, we enhance the CO 2 solubility. If these reacted CO 2 mole-
cules have similar diffusion coeffi cients, our material will have a signifi cantly better
permeability and selectivity. We have seen that one of the reasons polymer materi-
als have this upper limit is that the CO 2 solubility varies only very little from one
material to another. This completely changes if CO 2 reacts.
(a) Scheme of functionalization of the polyaniline membrane fi rst photografted with
glycidyl methacrylate and 2-hydroxyethyl methacrylate and then reacted with diamines.
Figure reproduced with permission from Elsevier [7.15] .
( Continued )