The feasibility of using simulated moving bed technology (SMB) for chiral separation on cellulose triacetate is demonstrated on the preparative scale: 1 kg of a chiral epoxide has been separated. On comparing SMB technology w i t h conventional liquid chromatography it turns out that the main advantage of SMB lies in the signhcant reduction of mobile phase consumption. The process design for SMB is made theoretically and the predictions are c o h e d by our pilot study. o 1993 Wiley-Liss, Inc.KEY WORDS: simulated moving bed technology, chiral separation, cellulose triacetate, preparative scale liquid chromatography, racemic epoxide raphy. Using cellulose triacetate (CTA) as the stationary phase and methanol as eluent, baseline separation of the enantiomers can be achieved in a reasonable time. To overcome the problem of solvent recovery when scaling up into the kilogram range, simulated moving bed (SMB) technology offers an attractive alternative to conventional liquid chromatography (LC).The original SMB process was patented by UOP in the early 1960~,'-~ and has since been used in the petroleum industry, mainly for p-xylene production and in the sugar industry for fructose purification. In these applications, the separations are relatively easy-with selectivity factors of about 2 or higher-and therefore large particle size sorbents (500-1000 pm) and concomitantly low chromatographic efficiencies have proved adequate. However, in the fine chemical or pharmaceutical industries, production rates are lower (the ton range) and the separations are more demanding, and some the solid phase and the eluent which move in opposite directions. Feed, containing components A and B, is injected in the middle of the column. Provided that the affinities of A and B for the solid are different (B being more retained than A), appropriate choice of the solid and liquid flow rates will split the feed into two fractions. The less retained component (A) goes up in the direction of the fluid, and is collected in the raffinate stream, whereas B moves in the drection of the solid, and is collected in the extract stream. Countercurrent systems are attractive because they are usually more efficient than batch processes.
Simulated Moving Bed ChromatographyThe simulated moving bed pilot plant (Licosep plant at Separex, Champigneulles, France) can deal w i t h systems having from 4 to 24 columns. In order to separate our epoxide enantiomers, 10 and 12 column configurations were investigated.
Packing of Columns for SMB UnitThe COlumnS were superformance columns (Merck) of 2.6 cm i.d. and 11 cm length, packed with 25-40 pm cellulose effort has yet to be made to extend SMB technokgy to these applications. Enantioseparations have recently been performed by SMB on a small scale, involving ligand exchange with large particle size sorbents7 or adsorption on small, high efficiency phases.The aim of this work is to study the applicability of SMB technology for separation of the above mentioned oxide on a CTA sorbent, and to ep-SMB with an opti-