Ultra‐thin skin carbon hollow fiber membranes for sustainable molecular separations

Abstract

A transformative platform is reported to derive ultra-thin carbon molecular sieve (CMS) hollow fiber membranes from dual-layer precursor hollow fibers with independently tuned skin layer and substrate properties. These ultra-thin CMS hollow fiber membranes show attractive CO 2 /CH 4 separation factors and excellent CO 2 permeances up to~1,400% higher than state-of-the-art asymmetric CMS hollow fiber membranes. They provide a unique combination of permeance and selectivity competitive with zeolite membranes, but with much higher membrane packing density and potentially much lower costs.carbon molecular sieve membranes, hollow fiber membranes, molecular separations, natural gas purification, ultra-thin membranes

Hydrocarbon separations by glassy polymer membranes

“…[63] Notably, composite hollow fiber membranes formed by dry-jet/ wet-quench spinning ( Figure 23) are highly attractive for hydrocarbon separations. [201] They have high membrane packing density (m 2 membrane/m 3 module), and thus can provide potentially attractive hydrocarbon productivity for membranes with moderate or even low hydrocarbon permeances. Defect-free polyimide hollow fiber membranes [166,202] with relatively thick ($2 μm) skin layers were reported with propylene/propane and nbutane/iso-butane selectivities consistent with intrinsic values measured from dense films.…”

“…With carefully controlled membrane F I G U R E 2 3 Scanning electron microscope images (a,b) and formation (c) of composite Matrimid ® /Matrimid ® polymer hollow fiber membranes. [201] Adapted from ref. [201] with permission from Wiley fabrication conditions, defect-free ultrathin membranes can sometimes be successfully made in labs.…”

“…[201] Adapted from ref. [201] with permission from Wiley fabrication conditions, defect-free ultrathin membranes can sometimes be successfully made in labs. However, complete avoidance of defects is challenging, if possible at all, in ultrathin membranes manufactured at large scale.…”

“…Scanning electron microscope images (a,b) and formation (c) of composite Matrimid ® /Matrimid ® polymer hollow fiber membranes. [ 201 ] Adapted from ref. [201] with permission from Wiley…”

“…Forming defect‐free membranes becomes increasingly challenging as the separation layer thickness reduces to submicrometer levels, in which defects are more likely to give nonselective diffusion pathways. [ 201 ] . Molecular transport in these defects follows the Knudsen diffusion mechanism, which can dramatically reduce membrane selectivities below the intrinsic values measured in thicker films.…”