Phase behaviour of the ternary solvent system alcohol, iso-octane, water: a theoretical COSMO-RS study for liquid-liquid extraction purposes and catalyst re-using applications
We discuss the liquid-liquid equilibrium phase diagrams of the ternary system alcohol, iso-octane, and water. This solvent system is a promising candidate for liquid-liquid extraction purposes and the implementation of successful catalyst re-using applications. Phase diagrams with ethanol, methanol, and n-propanol as alcohol component have been evaluated using the COSMO-RS theory. Special emphasis is given to the question how polarity and amount of the alcohols influence the separation properties. We find in agreement with experiments that separation (and therefore a later on incorporated extraction of catalyst) is improved by substituting methanol for ethanol. The system with methanol as alcohol component is most favoured in process development because it forms an open miscibility gap. In contrast, using n-propanol leads to higher amounts of alcohol and water in the oil phase.
Up to date, 70 percent of all registered active pharmaceutical ingredients (APIs) are chiral molecules (1). Chiral catalysts provide superior selectivity and activity for the synthesis of numerous chiral compounds, but one of the biggest encounters producers face is the loss of the expensive catalysts due to decomposition of the active catalysts or to a tremendous loss of activity throughout the work-up process (2). The successful re-using of unmodified catalysts for industrial requirements has so far been thwarted and only a handful of re-using processes for chiral unmodified homogeneous catalysts are known (3). Recently, we have developed and reported a novel re-using method for the asymmetric step of the synthesis of Ramelteon, an active agent for the treatment of sleeping disorders (4). Using an aqueous liquid-liquid solvent system allowed a gentle and more sustainable separation of the Ru-BINAP catalyst from the product mixture. The application of aqueous biphasic catalysis is a very elegant method for re-using homogeneous catalysts and the Ruhrchemie/Rhône-Poulenc process for the Rhodium catalysed hydroformylation (5) has already prov ...