Hierarchical porous carbon membranes for lean-helium extraction from high-pressure natural gas

Abstract

Given the scarcity of helium (He) resources, the application of scalable and energy-efficient membrane-mediated separation techniques for helium extraction holds substantial potential; however, few membrane materials have been reported for lean-helium extraction from natural gas feeds (<1000 ppm). Herein, we present a facile strategy for fabricating the carbon molecular sieve (CMS) hollow fiber membranes with a hierarchical porous structure by tailoring the phase inversion behaviors of blend polymeric precursors and engineering the pyrolysis protocol. The CMS membranes composed of highly homogenized and inconsecutive macropores and size-constrained ultramicropores in synergy exhibited superior separation performance in the separation of He/CH₄. For instance, CA-3-700 membranes showed a He/CH₄ ideal selectivity of 1427 and He permeability of 521 barrer. In addition, the membrane presented superior mixed gas separation performances under simulated helium-contained high-pressure natural gas at hundred ppm levels (400–1300 ppm), while demonstrating long-term continuous stability (from a quinary mixture of He/CH₄/N₂/C₂H₆/CO₂) over 120 h.