| Membranes provide environmentally benign methods to separate mixtures of organic compounds, often selectively and efficiently. Facilitated transport membranes contain a carrier which reacts reversibly and selectively with a solute to increase its flux across the membrane.; Nafion is a perfluorosulfonate ionomer membrane that can be exchanged with cations. Silver ions reversibly bind with double bonds of unsaturated compounds, and are effective carriers to separate saturated and unsaturated compounds. Transport experiments were performed using Ag+ -exchanged Nafion membranes to determine structure effects on transport properties. For acyclic dienes, the largest separation factors with respect to 1-hexene were observed for compounds with more spacing between double bonds (43 for 1,5-hexadiene; 2.4 for 1,3-hexadiene). Larger separation factors were observed for compounds with external versus internal double bonds (56 for 1,5-hexadiene; 1.8 for 1,3-hexadiene, both with respect to 2,4-hexadiene). The trend in spacing between double bonds was opposite for cyclic dienes, with the separation factor of 1,3-cyclohexadiene versus cyclohexene 10 times that of 1,4-cyclohexadiene. A second type of perfluorosulfonate ionomer membrane was exchanged with Ag(I). This material contained more ion-exchange sites, and absorbed more water than Nafion (∼63% versus ∼20%). It exhibited 30--60% greater fluxes and up to 12% larger diene/monoene separation factors than Nafion.; Composite membrane materials for the separation of ketones, alcohols, and thiophenes from hydrocarbons were prepared and characterized. Identifying carriers for these solutes was a challenging problem. Initial studies involved molecular complexation using NMR, but most observable interactions had low equilibrium constants. A novel strategy to identify carriers was developed, which utilizes gas chromatography retention data from the literature to identify promising stationary phases. Polymers with similar functional groups were incorporated into Anopore supports to make composite membranes, which were analyzed for productivity and selectivity in transport experiments. PVA, SSA, and nylon composite membranes provided good separation of ketones and alcohols from hydrocarbons, with cyclohexanone/cyclohexane and cyclohexanol/cyclohexane separation factors of: ∼54 and ∼40; 230 and 170; 37--99 and 28--72, respectively. PS286 composite membranes separated ketones from alcohols, with separation factors up to 4.6. All membranes were analyzed using IR spectroscopy and scanning electron microscopy. |
