Simulated moving bed (SMB) chromatography is attracting more and more attention
since it is a powerful technique for complex separation tasks. Nowadays, more than
60% of preparative SMB units are installed in the pharmaceutical and in the food in-
dustry [SDI, Preparative and Process Liquid Chromatography: The Future of Process
Separations, International Strategic Directions, Los Angeles, USA, 2002. http://www.
strategicdirections.com]. Chromatography is the method of choice in these ¯elds, be-
cause often pharmaceuticals and ¯ne-chemicals have physico-chemical properties which
di®er little from those of the by-products, and they may be thermally instable. In these
cases, standard separation techniques as distillation and extraction are not applicable.
The noteworthiness of preparative chromatography, particulary SMB process, as a sep-
aration and puri¯cation process in the above mentioned industries has been increasing,
due to its °exibility, energy e±ciency and higher product purity performance.
Consequently, a new SMB paradigm is requested by the large number of potential small-
scale applications of the SMB technology, which exploits the °exibility and versatility of
the technology. In this new SMB paradigm, a number of possibilities for improving SMB
performance through variation of parameters during a switching interval, are pushing the
trend toward the use of units with smaller number of columns because less stationary
phase is used and the setup is more economical. This is especially important for the phar-
maceutical industry, where SMBs are seen as multipurpose units that can be applied to
di®erent separations in all stages of the drug-development cycle.
In order to reduce the experimental e®ort and accordingly the coast associated with the
development of separation processes, simulation models are intensively used. One impor-
tant aspect in this context refers to the determination of the adsorption isotherms in
SMB chromatography, where separations are usually carried out under strongly nonlinear
conditions in order to achieve higher productivities. The accurate determination of the
competitive adsorption equilibrium of the enantiomeric species is thus of fundamental
importance to allow computer-assisted optimization or process scale-up.
Two major SMB operating problems are apparent at production scale: the assessment
of product quality and the maintenance of long-term stable and controlled operation.
Constraints regarding product purity, dictated by pharmaceutical and food regulatory
organizations, have drastically increased the demand for product quality control. The
strict imposed regulations are increasing the need for developing optically pure drugs.(...
