Isolation of target molecules from complex feed mixtures using isocratic and gradient simulated moving bed chromatography

To overcome the efficiency limitations of batch processing, different modes of continuous chromatographic separation have been developed, in particular the simulated moving bed chromatography (SMB) [1], which simulates countercurrent solid flow through cyclic changing of valve positions. The application of SMB for the separation of binary mixtures is relatively well developed [2], in contrast, the isolation of intermediary eluting compounds remains a challenging task [3]. This separation can be performed by splitting the feed solution into 3 fractions using an integrated 8-zone SMB unit acting as two coupled 4-zone SMB units [4, 5]. Due to the very broad spectrum of compounds that might be present in feed mixtures, it is common practice to employ gradients in the liquid phase composition to reduce processing times. This approach can be extended to SMB by varying the eluting strengths in the different zones. This makes the identification of operating regions more complex. The purpose of the present project is to identify the operating regions of isocratic and gradient assisted 8-zone SMB for linear adsorption isotherms. This SMB configuration can be simplified to a true moving bed (TMB) and analyzed using an equilibrium stage model, which, in the steady state, simplifies to a large system of linear equations. This system can be efficiently reduced with aid of a recursive resolution method [6] that allows for a fast scanning of optimal operating conditions. The sizes and positions of the separation regions are discussed for different types of gradients. [1] D.B. Broughton, Abstracts of Papers of the American Chemical Society, 187 (1984) 9-INDE. [2] M. Mazzotti, G. Storti, M. Morbidelli, Journal of Chromatography A, 769 (1997) 3-24. [3] H. Schmidt-Traub, A. Seidel-Morgenstern, Preparative Chromatography, Wiley, 2012. [4] A. Seidel-Morgenstern, L.C. Kessler, M. Kaspereit, Chemical Engineering & Technology, 31 (2008) 826-837. [5] J. Nowak, D. Antos, A. Seidel-Morgenstern, Journal of Chromatography A, 1253 (2012) 58-70. [6] D. Beltscheva, P. Hugo, A. Seidel-Morgenstern, Journal of Chromatography A, 989 (2003) 31-45