Design of simulated moving bed and Varicol processes for preparative separations with a low number of columns

Abstract

Simulated moving bed (SMB) chromatography has received significant attention in the last decade, particularly as regards the production of very valuable products, such as enantiomerically pure pharmaceutical compounds. Recent applications in the pharmaceutical industry use SMB systems containing a low total number chromatographic columns, usually four to eight. This paper deals with the modeling and simulation of SMB systems with only four, five and six columns. In particular, two modeling strategies, the equivalent true moving bed and the real SMB models, are compared for these units in terms of separation regions and system productivity. Also, the recently proposed Varicol process is analyzed and compared with the classical SMB operation, and the advantages of this new operation mode are shown for systems using a low number of columns. 

Continuous chromatographic processes with a small number of columns: Comparison of simulated moving bed with Varicol, PowerFeed, and ModiCon

“…In fact, there is a clear trend in applications to operate SMB with 5 or 6 columns, instead of 8, which was previously regarded as the minimum number of columns for SMB units. The second approach aims at improving the unit's separation efficiency either by optimizing the adsorptivity of the solutes in the different sections of the unit, such as in supercritical fluid SMB [Nicoud and Perrut, 1992;Mazzotti et al, 1997b;Di Giovanni et al, 2001;Denet et al, 2001], temperature gradient SMB [Migliorini et al, 2001] and solvent gradient SMB [Jensen et al, 2000;Antos and Seidel-Morgenstern, 2001;Abel et al, 2002;Houwing et al, 2003], or more recently by operating SMB under more complex dynamic conditions, as it is the case in the Varicol Zhang et al, 2002Zhang et al, , 2003aToumi et al, 2003;Pais and Rodrigues, 2003], PowerFeed [Kearney and Hieb, 1992;Kloppenburg and Gilles, 1999;Zang and Wankat, 2002a, b;Zhang et al, 2003bZhang et al, , 2004 and ModiCon [Schramn et al, 2002[Schramn et al, , 2003 processes. These new operation modes do not keep constant conditions during one switching period t * , as in a standard SMB, but allow for variation of the column configuration, the fluid flowrates, or the feed concentration, respectively.…”

Simulated Moving Bed and Related Techniques

“…However, we should not forget that recent applications in the pharmaceutical industry use SMB systems containing a low total number of columns, for instance, a total of five or six columns. In these cases, as it was shown recently [12], the real and more precise SMB model should be used. Also, the SMB model will always be useful in characterizing the dynamic cyclic behavior of the concentration profiles.…”

“…For this example, sections 1 and 4 always have one column; however, sections 2 and 3 have, respectively, 2 − θ * and 1 + θ * columns; that is, we are in the presence of a Varicol 1/2 − θ * /1 + θ * /1 configuration. As it was shown recently [12], the simulation of SMB units with a low number of chromatographic columns must use the real and more precise SMB model. Figure 7.14 clearly shows that the evaluation of the SMB units using a low number of chromatographic columns shall avoid the use of the ideal countercurrent TMB or equilibrium theory models, and a more realistic SMB model, which takes into account the periodic shift of the injection and collection points, is needed.…”

Chromatographic Separation of Verapamil Racemate Using a Varicol Continuous Multicolumn Process

“…tures (Ludemann-Hombourger et al, 2000;LudemannHombourger et al, 2002;Pais and Rodrigues, 2003;Gomes et al, 2010;Gomes and Rodrigues, 2012;Gong et al, 2014). Several theoretical and experimental results reported in the literature indicate that, due to the new degree of freedom, the Varicol process is a more favorable chromatographic technique than SMB, especially in terms of productivity and solvent consumption.…”