A High-Flux Polyimide As a Contender for CO2 Recovery From Flue Gas

A high-flux polyimide as a contender for CO₂ recovery from flue gas

R. P. Lively^a, M. E. Dose^b, L. Xu^b, J.R. Johnson^b, K. Zhang^b, J. T. Vaughn^b, M. E. Lydon^c, J. A. Thompson^b, J. S. Lee^b, L. Liu^b, Z. Hu^b, M. J. Realff^b, W. J. Koros^b

^aAlgenol Biofuels, 28100 Bonita Grande Drive, Bonita Springs, FL 34315, USA

^bSchool of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Dr, Atlanta, GA 30332-0100, USA

^cSchool of Chemistry, Georgia Institute of Technology, 901 Atlantic Dr, Atlanta, GA 30332-0400, USA

Abstract

Using a top-down, process-guided approach, a new 6FDA-based polyimide—6FDA-DAM:DABA (4:1)—has been synthesized and subsequently spun as hollow fiber membranes for CO₂ recovery from post-combustion flue gas streams. Dense film studies on 6FDA-DAM:DABA (4:1) reveal a CO₂ permeability of 224±0.5 Barrers at 40°C and a CO₂ feed pressure of 10 psia.  The dense films exhibit a CO₂/N₂ selectivity of 20.4 at 40°C, which permits their use in a two-step counter-flow/sweep membrane process.  Dry-jet, wet-quench, non-solvent-induced phase inversion spinning was used to create defect-free hollow fibers.  Defect-free skin layers, approximately 350 nm thick, were obtained. The fibers had a pure CO₂ permeance of 520±9 GPU at 35°C and an ideal CO₂/N₂ selectivity of 23.5.  Temperature-dependent sorption, diffusion and permeation properties as well as glass transition and decomposition temperatures for the dense films and the hollow fiber membranes are also presented.  Moreover, mixed gas permeation, wet gas permeation and scanning electron microscopy (SEM) analysis are also presented for the fibers.  Finally, to increase CO₂ flux, we incorporated microporous ZIF-8 fillers into 6FDA-DAM:DABA(4:1) dense films.  ZIF-8 is a suitable choice for this purpose, as it is highly hydrophobic, easily adheres to the polymer, has high CO₂ permeabilities, and moderate CO₂/N₂ selectivities.  Our 6FDA-DAM:DABA(4:1)/ZIF-8 dense film composites had a CO₂ permeability of 553±2 Barrers and a CO₂/N₂ selectivity of 19.3 at 35°C.  Water vapor isotherms, XRD, DSC, SEM and HRTEM data are also presented for these composites.