Aromatic polyamide-derived carbon molecular sieve membranes for hydrogen separation

C. Zhang, G. Iyer, C.E. Ku
University of Maryland, College Park,
United States

Keywords: membrane separation, carbon molecular sieve, hydrogen separation


Hydrogen (H2) is a clean fuel and chemical feedstock. Ten million tons of H2 is produced in the U.S. by natural gas reforming every year with a hundred million tons of carbon dioxide (CO2) byproduct. Efficient H2/CO2 separation is thus crucial to produce purified H2 and capture the CO2 byproduct. Membrane separation is an energy-efficient alternative to pressure-swing adsorption for H2/CO2 separation. Carbon molecular sieve (CMS) membranes have a good balance of gas separation performance and scalability. The chemistry of polymer precursors is known to govern the pore structure and transport properties of CMS membranes. In this talk, we will present H2/CO2 separation in novel CMS membranes made by pyrolysis of an un-crosslinked aromatic polyamide (aramid) precursor. The excellent solution-processability of the aramid precursor allowed the fabrication of aramid hollow fiber membranes by solution spinning, which gave aramid-derived CMS hollow fiber membranes by pyrolysis at 925 °C. The aramid-derived CMS membranes showed the highest H2/CO2 ideal selectivity among all CMS membranes reported in literature, which was attributed to the membrane’s ultra-high H2/CO2 diffusion selectivity. The aramid-derived CMS membranes also demonstrated outstanding H2/CO2 separation factor with H2/CO2 mixture feeds at elevated permeation temperature. Finally, the aramid-derived CMS membrane will be compared with CMS membranes derived from polyamide-imides and polyimides to elucidate the effects of precursor hydrogen bonding on CMS membrane pore structure and transport properties.