(539g) Perfluorinated Membranes for Pervaporation Separation of Solvent Mixtures in Pharmaceutical Processing

The pharmaceutical industry manufactures large quantities of drug products while employing a variety of organic solvents with a wide range of chemical properties. Mixtures of these solvents are often created as byproducts of the manufacturing process, which may include methanol, ethyl acetate, tetrahydrofuran (THF), toluene, dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMAc) and water. Pervaporation of binary mixtures was carried out using a perfluoro-2,2-dimethyl-1,3-dioxole-tetrafluoroethylene copolymer membrane, known as CMS-3, over a range of compositions and temperatures of 30, 50, and 60°C. This membrane has a significantly high fractional free volume, 0.342, while possessing reliable thermal, mechanical and chemical resistance. The membrane has been found to typically favor solvents with smaller molecular dimensions. Separation of organic-organic systems yields limited results. The membrane is selective for methanol in methanol-toluene systems, giving an overall selectivity value of 4.5 and producing methanol flux of 1.1 g/m²-h. Consistent water-selective performance, comparable to that of zeolites for alcohol-water systems, was obtained when separating high boiling aprotic solvents from water. Using a 90 wt% DMF-10 wt% water feed, CMS-3 is able to achieve a separation factor of 10,766 at 60°C.