(A) study on ultrathin carbon molecular sieve hollow fiber for xylene isomers separation

Abstract

Thanks to its unique pore structure composed of micropores and ultramicropores, carbon molecular sieve (CMS) is an attractive material for membrane fabrication. In terms of large scale for membrane-based separation process, hollow fiber format may be a good option due to its high effective area in unit volume. However, when polymer hollow fiber precursor is pyrolyzed to produce CMS membrane, its morphology is vulnerable to be partially collapsed, resulting in thick selective layer and therefore low permeation flux. Instead, thin composite membrane where ultrathin selective CMS layer is coated on porous ceramic hollow fiber substrate can provide thin separation length. In this work, polymer precursor was selected with the perspective of diffusional selectivity of solution-diffusion mechanism. Next, polymer precursor was dip-coated onto a porous alumina hollow fiber and pyrolyzed to fabricate CMS-alumina composite hollow fiber membrane. Using the membrane, single molecule permeation of the xylene isomers data was reported with pressure gradient. Finally, xylene mixtures were differentiated via organic solvent reverse osmosis (OSRO) process. It is expected that organic liquid mixtures can be separated more efficiently than the conventional thermal process.