Poly(vinyl pyrrolidone-co-vinyl acetate)–cellulose acetate blends as novel pervaporation membranes for ethanol–ethyl tertio-butyl ether separation

✍ Scribed by Quang-Trong Nguyen; Irwan Noezar; Robert Clément; Christian Streicher; Helmut Brueschke

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 271 KB
• Volume: 8
• Category: Article
• ISSN: 1042-7147
• DOI: 10.1002/(sici)1099-1581(199708)8:8<477::aid-pat653>3.0.co;2-0

✦ Synopsis

The design of high-performance pervaporation membranes for the selective removal of ethanol from ethyl t-butyl ether (ETBE) was performed by using the polymer blending method. Binary blends of cellulose acetate or cellulose triacetate with a specific copolymer, poly(vinyl pyrrolidone-co-vinyl acetate), were studied by pycnometry, differential scanning calorimetry, infrared spectroscopy, solvent-mixture sorption and pervaporation.The sorption extent and especially the permeability of the blend membranes to the ethanol-ETBE azeotropic mixture increases greatly with the copolymer content with quasiconstant and high selectivity. This behavior is attributed to the specific interactions of amide C = O groups (a strong Lewis-base) in the copolymer with ethanol. The resulting high-performance membranes were stable at low temperatures but showed some performance alteration, at temperatures exceeding 80°C, because of copolymer extraction by the solvent mixture. The different behaviors of the same membrane at high and low temperatures were explained in terms of copolymer chain reptation, which was possible in the rubbery state but not in the glassy state. A crosslinking of the two polymers via urethane bonds led to perfectly stable high-performance membranes for the target application.