(619a) Nanoscale Interfacial Design Concept Towards High Flux CO2 Separation Maintaining High Selectivity and Longevity

Nanoscale Interfacial Design Concept Towards High Flux CO₂ Separation Maintaining High Selectivity and Longevity

Lakshmi S. Kocherlakota, Tiep Pham, and René M. Overney^*

Contemporary environmental and energy production areas are driving current research for pursuing green and sustainable technologies for an economically viable and energy efficient solutions. Membrane based separation technology offers a less energy intensive and environmentally friendly alternative for gas purification processes. Particularly novel organic-inorganic nanocomposite membranes have been shown to push the gas permeability and selectivity capabilities of polymeric membrane materials into the attractive regions based on commercial separation requirements. One of the most notable permeation materials in regards of its high permeation values of up to several thousand Barrer, and its reverse-selectivity towards the lighter component in H₂/CO₂ and N₂/CO₂  is poly(l-trimethylsilyl-1-propyne) (PTMSP), a high free volume glassy polymer. Problematic in nanocomposites are particle dispersion and environmental health concerns due to the small particle size. These two shortcomings are resolved potentially by switching to “inverse composites”, in which the polymer matrix is replaced by a porous membrane that provides the interfacial/dimensional constraints, while the polymer itself is injected into the pores. Porous membranes also provide mechanical and temporal stability. In this paper, we discuss how beneficial interfacial constraints, concerning both permeation and selectivity in PTMSP (found in ultrathin film membranes¹), can be imposed controllably in macroscopic inverse composites, thereby maintaining the enhanced transport properties of thin films, and provide relative improved longevity. PTMSP embedded nanoporous anodic aluminum oxide (AAO)   hybrid membranes reveal gas permeabilities for helium, nitrogen and CO₂ that exceeded 5 to7 times the values of pristine bulk PMTSP. Most notably, the gas selectivities of CO₂/He and CO₂/N₂ could also be enhanced by ~40%, and physical aging caused by free-volume collapse, could be reduced 20- fold compared to ultrathin film systems due to pore wall stabilization.  Our current studies on polyethylene oxide (PEO) based polymeric materials which are being extensively studied for CO₂ separation  are also revealing improved separation capabilities in AAO-confined hybrid polymeric structures. We found that AAO-confined PEO exhibits CO₂/He separation of ~10, which represents a 40% enhanced selectivity over the bulk membranes.

1.            Kocherlakota LS, Knorr DB, Foster L, and Overney RM. Polymer 2012;53(12):2394-2401.