(142b) Chemically Crosslinked Polymer Nanocomposite Membranes for Hydrogen Separation

Gas separation technologies have witnessed a number of advances over the past decade as functionalized materials are being designed on the basis of evolving material design paradigms. Polymeric membranes, in particular, are undergoing a renaissance as a low-cost, energy-efficient, environmentally-friendly means of separating gases on the basis of both size and solubility. As nanostructured polymers continue to develop, many of the insights gained from these multifunctional materials can be exploited in the molecular-level design of selective membranes. Recent efforts have demonstrated that the incorporation of dispersed nanoparticles within a polymer matrix can alter the local free volume of polymeric membranes, as well as improve the affinity for one penetrant gas species over another. Moreover, chemical cross-linking of such membranes can further influence the available free volume of a polymer, selectively altering the diffusion of larger gas molecules. Some of our previous findings related to H2 purification from mixed CO2/H2 gas streams will be briefly reviewed. In the present work, we present a straightforward strategy for developing cross-linked H2-selective polymers containing palladium (Pd) nanoparticles grown in-situ. Previous work has shown that such cross-linking can greatly reduce the permeabilities of larger gases (e.g., CO2, O2 and N2) without hindering the permeabilities of smaller gases (e.g., He and H2), thereby increasing the ideal selectivity of H2 relative to larger gases, in some instances, above the Robeson trade-off line. Nanoparticles of Pd are integrated into the polymer membrane to not only reduce the free volume available for molecular transport, but also increase the solubility of H2. We will present chemical evidence for cross-linking of the polymers under investigation and microscopic evidence for the incorporation and distribution of Pd nanoparticles. Pure- and mixed-gas permeability and sorption data will be reported to illustrate the effects of chemical cross-linking and Pd nanoparticles on H2 permeability and H2/gas selectivity relative to other polymeric membranes.