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Aziridine-Functionalized Mesoporous Silica Membranes on Polymeric Hollow Fibers: Synthesis and Single-Component CO2 and N2 Permeation Properties

Kim, Hyung-Ju, Chaikittisilp, Watcharop, Jang, Kwang-Suk, Didas, Stephanie A., Johnson, Justin R., Koros, William J., Nair, Sankar, Jones, Christopher W.
Industrial & Engineering Chemistry Research 2015 v.54 no.16 pp. 4407-4413
adsorption, carbon dioxide, crosslinking, diffusivity, engineering, ethyleneimine, nitrogen, polymers, porous media, silica
The synthesis of aziridine-functionalized mesoporous silica membranes on polymeric hollow fibers is described, and their single-component CO₂ and N₂ permeation properties are investigated under both dry and humid conditions to elucidate the unusual permeation mechanisms observed in these membranes. Hollow fiber-supported mesoporous silica membranes are amine-functionalized with aziridine to yield hyperbranched aminopolymers within the membrane pores. The effects of the hyperbranched polymers in the mesopores on gas transport properties are investigated by single-component gas permeation measurements. The hyperbranched aminosilica membrane shows counterintuitive N₂-selective (over CO₂) permeation during operation under dry conditions. Further characterization of the permeation behavior reveals the effects of strong adsorption of CO₂ under dry permeation conditions, leading to reduced CO₂ diffusivity because of CO₂-induced amine cross-linking in the mesopores. On the other hand, the hyperbranched aminosilica membrane shows CO₂-selective properties under humid conditions. Water molecules cause a lower degree of amine cross-linking and thus allow facilitated transport of CO₂. This first study of hollow fiber-supported hyperbranched aminosilica membranes indicates that they can be tuned to have N₂- or CO₂-selective permeation properties under the conditions employed.