Carbon molecular sieving membranes for butane isomer separation

Membrane-based separations of hydrocarbon isomers are major challenges for the petrochemical industry. Herein, high quality carbon molecular sieving membranes (CMSMs) were prepared on gamma-alumina substrates from pyrolysis of P84 polymer membranes. Targeting at butane isomer separations, we tailored the slit-like ultramicropores of CMSMs at angstrom level by rational manipulations of the pyrolysis temperature. The crack-free CMSMs were obtained at 600 degrees C with the narrow and uniform ultramicropores centered at 6.0 a. A clear molecular size/shape discrimination was achieved successfully and remarkable n-butane permeance (384 GPU) and n-butane/iso-butane separation factor (74) was observed, which transcends the upper limit of well-intergrown crystalline zeolite membranes. Fine-tuning of the membrane thickness at sub-micron level, the n-butane permeance and n-butane/iso-butane separation factor were further optimized, which shows a great potential for petrochemical separation.