Pervaporation Membrane for Linear Alpha Olefin Separation\nUsing Surface-Activated Silver Nanoparticles as Carriers for Facilitated\nTransport

Facilitated\ntransport membranes provide a low-cost means of separating\nhydrocarbon mixtures. However, the application of such membranes is\ncurrently limited to gas-phase mixtures. In this study, a pervaporation\nmembrane that can separate high concentrations of linear alpha olefins\n(e.g., 1-hexene and 1-octene) from liquid-phase hydrocarbon mixtures\nwas developed. The pervaporation membrane was fabricated by coating\na known olefin gas separation membrane material, poly­(vinylpyrrolidone),\nonto a microporous support. Silver nanoparticles (Ag NPs) were incorporated\ninto the polymer matrix and activated by the electron-accepting polarizer\n7,7,8,8-tetracyanoquinodimethane to induce a partial positive charge\non their surface. They acted as olefin carriers for facilitated transport,\nresulting in the extremely high pervaporative separation of a 1-hexene/<i>n</i>-hexane mixture over a long period. A 1-hexene concentration\nof more than 99% in the permeate was achieved at a feed concentration\nof 25%, resulting in a separation factor higher than 100 under stable\noperation for at least 100 h. Additionally, when the permeate pressure\nincreased to 500 mbar, the 1-hexene flux sharply increased because\nof facilitated transport by the carrier action of the surface-charged\nAg NPs, whereas the <i>n</i>-hexane flux remained nearly\nunchanged. These results demonstrate that facilitated transport membranes\nare highly effective in the pervaporative separation of liquid-phase\nmixtures and thus may provide a future direction for the development\nof high-performance membrane materials.