High performance dual-layer hollow fiber membrane of sulfonated polyphenylsulfone/Polybenzimidazole for hydrogen purification

This study provides a novel method for the fabrication and microstructural manipulation of high-performance dual-layer hollow fiber membranes for H-2/CO2 separation at elevated temperatures. For the first time, hollow fibers consisting of an outer-selective layer made from polybenzimidazole (PBI) and sulfonated polyphenylsulfone (sPPSU) blends and an inner-support layer made of polysulfone were prepared. sPPSU was chosen because it performed as an ionic-crosslinker towards PBI and it had a higher permeability than PBI. The as-spun hollow fibers were chemically cross-linked by alpha,alpha'-dibromo-p-xylene (DBX) and then heat treated to enhance their gas separation performance for H-2/CO2 separation. Experiments revealed that sPPSU interacted with PBI at the molecular level and increased the interchain space within PBI, leading to an increment in H-2 permeance. The covalent crosslinking reaction between PBI and DBX resulted in the outer-selective sPPSU/PBI layer with a smaller free volume but a greater H-2/CO2 selectivity. The dual-layer hollow fiber membrane cross-linked by 3% DBX and annealed at 120 degrees C (i.e., HSP-10-3%DBX-120) has a H-2 permeance of 16.7 GPU and an H-2/CO2 selectivity of 9.7 at 90 degrees C and 14 atm. The fabrication of dual-layer hollow fibers may open up a new approach to produce useful membranes for hydrogen purification and CO2 capture at elevated temperatures.