Abstract

Flow Reactors with Polymeric Membranes for Catalytic Aerobic Partial Oxidation Chemistry in Pharmaceuticals and Specialty Chemicals

Thatcher Root, Professor, University of Wisconsin

Aerobic oxidation reactions have great potential for development of more environmentally benign processes for production of highly functionalized molecules. Catalytic systems using air or pure oxygen have high atom efficiency and avoid use of hazardous oxidants that produce undesired wastes, and they can be advantageously implemented in flow in membrane reactors to avoid formation of organic solvent-air mixtures that would create concern about safe operation. Studies using several types of inexpensive, commodity polymer tubing show that these relatively low-performance materials are suitable when configured for the reaction kinetics. These capabilities are explored with homogeneous Cu/TEMPO and heterogeneous Ru(OH)x/alumina catalyst systems for alcohol oxidation processes developed recently in our laboratories. Comparison of operation in batch, gas-liquid co-feed flow, and membrane configuration shows excellent scalability and performance. Use of gas-permeable membranes allows use of elevated oxygen pressures and even pure oxygen while also avoiding formation of flammable solvent-gas mixtures, thus allowing operation though an extended range of temperature and oxygen pressures. The membrane reactor is readily scaled up for use with substrate quantities of 10 g or more, and has been demonstrated with several extended runs.