Highly Selective and Hydrocarbon-Resistant Polyimide Hollow Fiber Membranes for Helium Recovery from Natural Gas

The recovery of helium from natural gas using membranes has attracted substantial attention, while very limited polymers were spun into hollow fibers and evaluated for realistic helium recovery. This work demonstrates the successful preparation of asymmetric and highly helium-selective hollow fiber membranes for the enrichment of helium from natural gas. A novel, aromatic copolyimide was designed and fabricated into hollow fiber membranes (HFMs) via the dry-jet/wet-quench spinning approach. The as-prepared HFMs display a He permeance of 85 GPU and high He-related gas selectivities of 140, 204, 448, and 609 for He/N2, He/CH4, He/C2H6, and He/C3H8 gas pairs, respectively. Particularly, ternary and quaternary mixed-gas permeation results reveal excellent light and heavy hydrocarbon resistance due to the competition between plasticization and gas sorption. The HFMs also demonstrated superior low-temperature gas separation performance and outstanding membrane gas separation stability, rendering them attractive for helium recovery.