Abstract
Journal of Membrane Science 2018, 567, 261-271
Nanotube-reinforced Facilitated Transport Membrane for CO2/N2 Separation with Vacuum Operation
Y. Han, D. Wu, and W.S.W. Ho
A novel facilitated transport membrane was synthesized in a composite membrane configuration with a 170-nm selective layer coated on a polyethersulfone nanoporous substrate. In the selective layer, poly(N-vinylformamide-co-vinylamine) with amino groups covalently bound to the polymer backbone聽was used as the fixed-site carrier and an aminoacid salt, synthesized by deprotonating sarcosine with 2-(1-piperazinyl)ethylamine, was blended as the mobile carrier. The membrane demonstrated a CO2聽permeance of 975 GPU聽(1 GPU聽= 10-6聽cm3聽(STP)?cm-2聽s-1聽cmHg-1) and a CO2/N2聽selectivity >?140 at 57?掳C with 1?atm feed and permeate pressures. The membrane performance聽was also characterized with a vacuum pulled on the permeate side聽to simulate actual separation process conditions. However, the rubbery selective layer of the synthesized membrane sank into the nanoporous substrate, resulting in a drastically reduced CO2聽permeance. To address this issue, multi-walled carbon nanotubes聽(MWNTs) wrapped by a copolymer聽poly(1-vinylpyrrolidone-co-vinyl acetate) were dispersed in the selective layer as reinforcement nanofillers. The gas permeation聽measurements showed that the incorporation of MWNTs strengthened the polymer matrix聽and the selective layer penetration was refrained by a 3?wt% MWNT loading. The presence of MWNTs also mitigated the polymer compaction if the feed gas was compressed.