Issue Date: July 16, 2007
Separations Boost Microchemistry
Microfluidic reactor systems permit efficient and safe continuous syntheses for small-scale screening, optimization, and production purposes. But microscale operations have been limited to one-step reactions or to a sequence of reactions not requiring purification of intermediates or products. MIT's Hemantkumar R. Sahoo, Jason G. Kralj, and Klavs F. Jensen now have remedied that situation by stringing together three reaction modules into a single production line that incorporates modules for liquid-liquid and gas-liquid phase separation of reaction intermediates (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200701434). To test the system, the researchers chose to make carbamates, which are important building blocks for pesticides and other chemicals. Their synthesis includes separating an organic azide intermediate from an aqueous reaction stream by using a thin porous fluoropolymer membrane that denies the aqueous phase but allows the azide to pass. The azide subsequently is converted into an isocyanate intermediate, which is separated from the N2 gas by-product by a membrane that allows the liquid phase containing the isocyanate to pass while blocking N2.
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