Sorption and pervaporation properties of crosslinked membranes of poly(ethylene oxide imide) segmented copolymer to aromaticonaromatic hydrocarbon mixtures

摘要

Poly(ethylene oxide imide) segmented copolymer (PEO-PI) membranes were crosslinked by the chemical reaction between ethylene glycol diglycidyl ether and benzylalcohol groups of diamine moieties in polyimide segments at high temperatures. Sorption and diffusion of penetrants took place in poly(ethylone oxide) segment microdomains. Sorption and desorption behavior of pure vapors such as benzene (Bz), cyclohexane (Cx) and n-hexane (Hx) was classified as the Fickian diffusion. Sorption isotherms of binary liquid mixtures could be represented by the Flory-Rehner model, but the model overpredicted the sorption amounts of Cx and Hx, leading to small predictions of sorption selectivity alpha(S) for Bz/Cx and Bz/Hx systems. UNIFAC-FV model fairly well predicted the sorption amounts of aromatic hydrocarbons, but significantly overestimated those of nonaromatic ones, leading to toes small predictions of alpha(S). Pervaporation (PV) behavior of PEG-PI membranes was governed by sorption behavior followed by membrane swelling. Diffusion coefficient weakly depended on the minimum cross section of a penetrant. The diffusivity selectivity ct, hardly depended on the feed composition and was about 1.4 and 0.75 for Bz/Cx and Bz/Hx, respectively. PV selectivity alpha(PV) was larger for Bz/Hx than for Bz/Cx because of larger or,. PEG-PI membranes displayed high specific permeation flux Ql and reasonably high alpha(PV) for aromatic/ nonaromatic hydrocarbons; for example, Ql = 60 Kg mu m/(m(2) h) and alpha(PV) = 8 for a feed mixture containing Bz, Tol, Hx, n-Ot and i-Ot of 20 wt % at 353 K. (C) 2000 John Wiley & Sons, Inc. [References: 33]