Air Separation Properties and Stabilities of Blend Membranes of Liquid Crystals with Ethyl Cellulose

Publisher Website
Google Scholar
Abstract
Air separation properties and stabilities of four blend membranes, 1–30-μ.m thick, prepared from ethyl cellulose (EC) with a small amount of nematic and cholesteric liquid crystals, such as p-heptyl-p'-cyanobiphenyl (7CB), p-pentylphenol-p'-methoxybenzoate (5PMB), benzoate-containing liquid crystal mixture (DYC), and cholesteryl oleyl carbonate (COC), were investigated by the variable volume method. To provide more significant information guiding membrane-based air separation, air was directly used as the test gas. The membranes showed both higher oxygen permeability, P O2 , and oxygen over nitrogen separation factor, P O2 /P N2 , in the temperature range of the liquid crystalline phase. Oxygen-enriched air (OEA) flux, Q OEA, and oxygen concentration. Y O2 increased simultaneously with increasing transmembrane pressure difference. Stability studies revealed that the efficiencies of concentrating oxygen using 1–7-μm thick DYC/EC (9/91) membranes laminated to porous polyethersulfone membranes were almost constant for a 120–510-hour operating time. The membrane possessed a Q OEA of 9.0 × 10−4 cm3(STP)/s.cm2 and YO2 of 40% at 30°C and 0.41 MPa for a single-stage process. The results suggest that the membranes could be used effectively in enriching oxygen from air.