Preparation and characterization of multilayer thin-film composite hollow fiber membranes for helium extraction from its mixtures

The unique and distinctive physico-chemical properties of helium make it an irreplaceable resource in a wide range of applications, including cryogenics. Commercially-produced helium is extracted from natural gas. For the use of a membrane to be viable for the helium extraction and enrichment process, the membrane-based process must be economically competitive against other conventional technologies, and therefore, developments in membrane and optimized process design are crucial. This work demonstrates the successful fabrication of a highly helium-selective multilayer thin-film composite hollow fiber membrane for the enrichment of helium from natural gas. An aromatic polyamide selective layer was formed on top of a mesoporous polyacrylonitrile support by interfacial polymerization, followed by a caulking process to plug defects on the polyamide layer. The permeation and separation properties of the multilayer thin-film composite hollow fiber membrane were characterized using pure and quaternary mixed gases. The effects of feed pressure (up to 300 psig) and stage-cut (1.5-20%) on helium purity and CH4 loss were systematically investigated.