Perfluoropolymer Membrane Behaves Like a Zeolite Membrane In Dehydration of Aprotic Solvents

Dehydration of aprotic solvents, frequently needed in pharmaceutical processing, can be implemented easily by vacuum- based pervaporation employing a novel perfluoropolymer-based membrane: perfluoro-2, 2-dimethyl-1, 1, 3-dioxole copolymerized with tetrafluoroethylene (PDD-TFE). Possessing one of the highest fractional free volumes, this polymer is resistant to most solvents including dimethyl formamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMAc). Excellent pervaporation selectivities for water over these aprotic solvents were obtained for mixtures containing 10, 5 and 1 wt% water in the temperature range of 25 -70^oC. The selectivities varied between 1000 and 12,000 depending on the water content, temperature and the solvent species. Such highly selective water removal in pervaporation has been achieved earlier in dehydration of ethanol by NaA zeolite membranes which however achieve an order of magnitude lower selectivity in for example, DMF-water system.