Chiral separation of amino-alcohols and amines by fractional reactive extraction

Description

Many naturally occurring substances possess chirality, which is the property that the molecule and its mirror image are not superimposable. Chirality plays an important role in biological systems. For instance, only one enantiomer (mirror isomer) of many pharmaceuticals is the active substance. The availability of optically pure substances is therefore of primary importance in the pharmaceutical and fine chemical industry. Chiral separation is an important, often cost-effective way to obtain these substances. Chiral separation may also be required as final purification step after a selective synthesis. The current industrial separation techniques each have major drawbacks. (Diastereomer) crystallisation is inflexible and involves solid-phase handling. Simulated moving bed (SMB) chromatography is more flexible, but it is very expensive because of the low volumetric productivity and the use of expensive chiral stationary phases (CSP's).In this thesis, fractional reactive extraction (FREX) is proposed and evaluated as alternativeindustrial separation technique. In FREX, an enantioselective extractant is applied as chiralselector. The process is versatile if the same extractant can be used with a good selectivity and capacity for a number of different substances from the same chemical class. Both enantiomers can be obtained at the desired purity by application of the fractional extraction scheme. Fractional reactive extraction combines in a liquid process flexibility with lower cost per chiral recognition site and high volumetric capacity. Despite its potential advantages over existing separation techniques, FREX is currently not applied on industrial scale because of a lack of versatile enantioselective extractants and a too low productivity. This thesis is therefore focused on identification of enantioselective extractants, improvement of productivity and technology development.