| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 106 === Carbon molecular sieve membranes (CMSM) materials are attractive alternatives to overcome the limit in the permeability-selectivity trade off of polymer membrane, because of their internal surface areas and bimodal pore size distribution. The geometry of carbon membrane and its installment are important to ensure high efficiency of a membrane in a separation process.
In this study, the asymmetric carbon hollow fiber membrane (CHFM) was prepared by one-step vacuum-assisted dip-coating and pyrolysis procedure and investigated for H2/CO2, H2/C2H6, H2/C3H8 separations. In order to increase the mechanical strength of the CHFM, the porous alumina hollow fiber with ID/OD= 2mm/4mm was used as a supporting material. Polyethyleneimine, and N-methyl-2-pyrrolidone were selected as the membrane precursor and casting solutions. The effects of (1) membrane preparation parameters, (2) fiber packing densities, (3) fiber packing arrangement, and (4) gas flow configuration (inside-out or outside-in) on the gas separation performance were also investigated.
The results indicated that the CHFM preparation parameters, including immersion vacuum times, concentration of casting solution, coating number, and the vacuum time after withdrawing were all have influences on the membrane thickness and gas permeability/selectivity. Decreasing the concentration of casting dope and coating times was the most effective approach to increasing the H2 permeability while maintaining the H2/CO2 selectivity. Further, as the fiber packing density increased from 5.54% to 38.78% with hexagonal packing configuration, the H2 permeability was increased from 419.97 Barrer to 826.18 Barrer without losing gas selectivity. The as-prepared CHFM exhibited the best gas permeability of H2 at 826.18 Barrer and gas selectivity of H2/CO2, H2/C2H6 and H2/C3H8 are 2.79, 4.65, and 5.34, respectively. While the gas inlet mode is inside-out or outside-in, there is no significantly difference on the gas separation performance. The successful preparation and modularization of CHFM is encouraging and industrially relevant for many gas separation application, such as H2 energy production from CO2, C2H6, and C3H8.
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