Spray-coating of nanoporous carbon membranes for air separation

Nanoporous carbons (NPC) can be fabricated in the form of supported thin films with minimal defects and remarkably high size selectivity of oxygen over nitrogen. Spray coating of porous stainless steel disks with a solution of poly(furfuryl) alcohol (PFA) in acetone was used to synthesize nanoporous carbon membranes in a reproducible manner, and is the first reported case of this technique being used for supported carbon membrane synthesis. The disks were dried and then pyrolyzed in an inert atmosphere to a final temperature of 600 degrees C. The resulting membranes were tested with binary oxygen/nitrogen mixtures. In experiments with a binary feed of oxygen and nitrogen, the membranes were found to have good oxygen over nitrogen selectivities (up to 4) and O-2 fluxes On the order of 10(-9) mol/m(2) sa. Attempts were made to modify membrane performance further by post-pyrolysis heating, additional coatings or by hydrocarbon pyrolysis. None of these post-treatments produced membranes superior to those derived directly from the initial spray coating and pyrolysis, (C) 1999 Elsevier Science B.V. All rights reserved.