High-performance carbon molecular sieve membranes for hydrogen purification and pervaporation dehydration of organic solvents

Ultrathin (approximate to 200 nm) and defect-free carbon molecular sieve (CMS) membranes were successfully fabricated on the inner surface of hierarchically structured porous supports (-Al2O3 layer coated -Al2O3 tubes) via pyrolysis of a polyimide precursor at 700 degrees C. The chemical structure of the carbonized samples was examined in detail by means of Raman spectroscopy and X-ray photoelectron spectroscopy. From these studies, it was found that the carbonized samples consist of graphitic carbon layers containing sp(3)-type defects. The synthesized CMS membranes showed an unprecedentedly high H-2 permeance of up to 1.1 x 10(-6) mol m(-2) s(-1) Pa-1 and ideal separation factors of 24, 130 and 228 for H-2/CO2, H-2/N-2 and H-2/CH4, respectively at 200 degrees C. Furthermore, outstanding separation factors of 791 and 1946 with a water flux of about 0.5 kg m(-2) h(-1) were obtained at 70 degrees C for the pervaporation of 10 wt% water-containing binary mixtures of methanol and ethanol, respectively. These results unambiguously show that the carbon membranes developed in this work possess the potential for high-temperature hydrogen purification and dewatering of organic solvents.