High performance membrane diffusion-enhanced

In summary, blending of Pebax 1657 with PEG300 resulted in membranes of higher CO2 permeability and selectivity due to enhanced CO2 diffusivity. However, a phase separation that occurred at high PEG300 contents led to a stagnancy of performance. The performance of Pebax membranes are compared with those obtained for the Pebax blend membranes on a CO2/N2 Robeson s plot [5,44] (Figure 13.9). 

When a complete separation of a solution takes place by a reverse osmosis membrane. only one component of the solution (usually the solvent) goes through the membrane and is enriched in the permeate. The other component (usually the solute), on the other hand, is left behind on the feed solution side of the membrane. Unless the solute diffuses back to the main body of the feed solu> tion quickly, the solute concentration in the vicinity of the membrane increases until a steady state is reached where the diffusion rate, enhanced by the high concentration near the membrane surface, counterbalances the rate of the solute accumulation near the membrane surface. This phenomenon is called concentration polarization and may occur even when the separation of the solute from the solvent is not perfect. It is known that the concentration polarization exerts an unfavorable effect on the performance of reverse osmosis membranes. For example, the experimentally observable solute separation defined later by Equation 5.46 is lowered, since the concentration in the permeate, c>i3, is governed not by the concentration of the solute in the main body of the feed solution, but... 

Su H, Jao T-C, Pasupathi S et al (2014) A novel dual catalyst layer structured gas diffusion electrode for enhanced performance of high temperature proton exchange membrane fuel cell. J Power Sources 246 63-67... 

Poly(substituted acetylene)s such as PTMSP and PMP, amorphous fluoro-polymers like Teflon AF and Hyflon AD, polymers with intrinsic microporosity, and thermally rearranged (TR) polymers are the candidate polymers for highly permeable glassy polymer membranes. The high free volume in glassy polymers contributes to enhanced diffusion and permeation of small gas molecules. The gas permeation performances of these highly permeable polymers even surpass upper bounds for CO2/N2, CO2/CH4 and H2/CO2 separations. 

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