Multi-layer composite hollow fiber membranes derived from poly(ethylene glycol) (PEG) containing hybrid materials for CO₂/N₂ separation

With the aim to make newly developed materials to be more industrially relevant, multi-layer composite hollow fiber membranes were molecularly designed by surface coating ultrathin layers of a poly(ethylene glycol) (PEG) containing hybrid material onto the polyethersulfone (PES) porous substrate for CO₂/N₂ separation. The asymmetric PES hollow fiber substrate was prepared by a dry-jet wet spinning process. Multiple ultrathin layers of the PEG containing hybrid polymer were then coated onto the substrate by continuous coating equipment that can be readily scaled up for industrial applications. The effects of substrate characteristics, coating concentration, pre-wetting agent, number of coating and testing conditions on gas separation performance of composite membranes have been investigated and elucidated. Positron annihilation spectroscopy (PAS) was used to investigate the evolution of coating thickness. The ultimate thickness of the dense selective layer is approximately 150nm. The membrane fabricated from a 0.5wt% coating solution shows an impressive CO₂/N₂ selectivity of 50 with the CO₂ permeance of 30GPU at 25°C and 0.2MPa (2atm).