Separation of Ternary Mixtures by Continuous Countercurrent Chromatography

The conventional Simulated Moving Bed (SMB) process realizes the separation of a feed mixture into two fractions by exploiting a simulated countercurrent contact of the solid and the fluid phase, basing on difference between adsorption affinities of the components on the solid phase. A major focus of SMB technology is still in the area of binary separations, however, an increasing interest in the chromatographic separation and purification of target compounds out of a multicomponent mixture has been observed recently. A major drawback of conventional SMB chromatography is the inability to produce a pure product stream if the desired component is neither the strongest nor the weakest adsorbable one. Therefore, several concepts have been proposed to achieve this goal through various modifications of SMB systems. Comprehensive overview of currently studied approaches along with their advantages and disadvantages will be provided. Modifications exploiting single SMB units, such as application of different adsorbents or using the variation of working flow rates during the switching period will be described. Particularly emphasized will be those techniques already being commercially used for ternary separations or having greatest potential for industrial application, i.e. coupling two (or more) SMB cascades in different arrangements, integrating more than 4 zones into a single unit, as well as commercialized by Japan Organo Co. pseudo-SMB process. The performance of these modified SMB systems will be analyzed and compared