Sandwich-like multilayer hollow fiber carbon membranes for gas separations

Abstract

Carbon molecular sieve (CMS) membranes with tunable and rigid pore structures are attractive for a broad spectrum of gas separations. The microstructure design of CMS membranes is one of the keys to developing advanced CMS membranes. Here, we present a sandwich-like multilayer CMS (SCMS) hollow fiber membrane, with inner and outer dense layers and an intermediate porous layer structure, which holds precise molecular sieving ability and good mechanical strength. Compared to symmetrical dense layer membranes, the SCMS hollow fiber membrane showed a ∼350 % increase in H₂ permeance and maintained a high H₂/CH₄ ideal selectivity of 398. Besides, the membranes exhibited pressure-resistance superiority, evidenced by H₂/CH₄ mixed gas tests under high-pressure conditions up to 40 bar. A dynamic durability test under a feed pressure of 30 bar demonstrated its good stability with a maintained H₂/CH₄ separation factor of ∼300. This work shows a path to design high-performance CMS membranes with a sandwich-like multilayer structure to maintain molecular sieving capability and pressure-resistance ability, which are ideal membrane materials for high-pressure-related light gas separations, such as H₂ (helium) extraction from natural gas and CO₂ removal from natural gas.