Gas Permeation Behavior of Pebax-1657 Nanocomposite Membrane Incorporated with Multiwalled Carbon Nanotubes

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• 作者：R. Surya Murali ; S. Sridhar ; T. Sankarshana ; Y. V. L. Ravikumar
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2010
• 出版时间：July 21, 2010
• 年：2010
• 卷：49
• 期：14
• 页码：6530-6538
• 全文大小：326K
• 年卷期：v.49,no.14(July 21, 2010)
• ISSN：1520-5045

文摘

Incorporation of multiwalled carbon nanotubes (MWNT) on the gas permeation properties of H₂, CO₂, O₂, and N₂ gases in poly(ether-block-amide) (Pebax-1657) membrane has been investigated. Pebax-1657 was dissolved in the ethanol−water mixture and cast on an ultraporous polyethersulfone substrate followed by complete solvent evaporation. Nanocomposite membranes were prepared by dispersion of MWNT in concentrations of 0−5% of polymer weight in the Pebax solutions with sonication for 2 h to ensure uniformity. Cross-linking was carried out in hexane medium using 2,4-toluylene diisocyanate (TDI). The permeabilities of pure gases were measured at room temperature, and the ideal selectivities were determined at pressures varying from 1−3 MPa using an indigenously built high-pressure gas separation manifold. For neat Pebax membrane, high permeabilities of 55.8 and 32.1 barrers were observed for CO₂ and H₂ gases, respectively, whereas that of N₂ was as low as 1.4 barrers. The selectivity of cross-linked 2% MWNT Pebax membrane was enhanced from 83.2 to 162 with increasing feed pressure (1−3 MPa) for the CO₂/N₂ gas pair, whereas the corresponding values for H₂/N₂ and O₂/N₂ systems were found to be in the range 82.5−90 and 7.1−6.8, respectively. The membranes were characterized by scanning electron microscopy (SEM) to study surface and cross-sectional morphologies. Fourier transform infrared (FT-IR), wide-angle X-ray diffraction (WAXD), and ion exchange capacity (IEC) studies were carried out to determine the effect of MWNT incorporation on intermolecular interactions, degree of crystallinity, and extent of cross-linking, respectively. Fractional free volume (FFV) calculations based on density measurements were conducted along with water sorption studies to explain permeation behavior. The use of modified block copolymer membranes provides a means for separation of CO₂ from N₂ in power plants, H₂ recycle from ammonia purge gas, O₂ enrichment from air for medical applications, and CO₂ removal from water-gas shift reaction to improve H₂ yield.