Pervaporation Membrane for Linear Alpha Olefin Separation Using Surface-Activated Silver Nanoparticles as Carriers for Facilitated Transport

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