Dual-layer hollow carbon fiber membranes for gas separation consisting of carbon and mixed matrix layers

Hollow carbon fiber membranes for gas separation have been successfully fabricated for the first time by a special type of precursor. This precursor is dual-layer hollow fiber composed of a polysulfone-beta zeolite (PSF-beta) mixed matrix outer layer and a Matrimid inner layer. Pure gas permeation measurements show that the resultant hollow carbon fiber has O₂/N₂ and CO₂/CH₄ selectivities of 9.3 and 150, respectively; this performance is much better than that of the hollow carbon fiber derived from single-layer Matrimid hollow fiber. Mixed gas measurements show the CO₂/CH₄ selectivity of 128. After pyrolysis, the PSF-beta layer in the dual-layer precursor evolves into a continuous structure of closely packed zeolite particles embedded in the PSF carbon residue. TGA spectra suggest that the possible reason for the above observation is that the PSF-beta outer layer and Matrimid inner layer has significantly changed each other's pyrolysis dynamics and thermal degradation process.