Temperature Gradient Operation of a Simulated Moving Bed Unit

Abstract

The simulated moving bed (SMB) technology has shown great potential for fine chemical separations, particularly for the resolution of the enantiomers of chiral compounds. Further improvements of separation performance are expected when each section of the unit is optimized independently by applying a gradient of temperature, pressure, or solvent composition along the unit. The aim of this work is to extend the design criteria for nonlinear SMBs to the case where a temperature gradient mode is adopted. It is shown how beneficial this can be in terms of productivity and solvent consumption. Finally, the temperature transient in the columns is studied. It is shown that temperature changes in the column of the unit yield a constraint on the maximum fluid velocity. This is analogous to the constraints due to column efficiency and packing stability requirements. The results show that the temperature gradient operation of an SMB unit is feasible and may have significant advantages over the traditional isothermal mode.

Analysis of a nonisothermal simulated moving‐bed reactor

“…In general, energy balance equations should be included in the model and solved together with the mass balance equations. Following the suggestion by Migliorini et al 20 spatial temperature gradient within a chromatographic column was neglected in this theoretical study for simplicity. In addition, the column temperature was assumed to change exponentially after a switch…”

“…More recently, studies have been carried out to improve SMB performance by adjusting adsorption behaviors in each operating zone according to its function. It has been shown that a gradient of adsorption strength ascending from zone I to zone IV, which can be realized by establishing a gradient of temperature 20,21 or eluent composition, 22,23 can significantly enhance the productivity of SMB processes.…”

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.…”

Positioning of salt gradients in ion‐exchange SMB

“…the separation of amino acids Ruthven and Ching, 1989 and Ž . enantiomeric amino-acid derivatives Migliorini et al, 2001 , Ž pressure gradients in supercritical fluid SMB Mazzotti et al, . 1997 , and gradients in solvent strength in reversed-phase Ž .…”