Simulated Moving Bed SMB Chromatography

In summary, the four sections have to fidfill the following tasks  

Unfortunately an efficient, dispersion-free movement of a stationary phase, which in most cases consists of porous particles in the micrometer range, is technically not possible. Therefore, other technical solutions had to be developed. The breakthrough was achieved with SMB systems, which were developed by Universal Oil Products (UOP) for the petrochemical industry in the 1960s (Broughton and Gerhold, 1961). Here the stationary phase is packed into single, discrete columns, which are connected to each other in a circle. 

The SMB concept is, in general, realized for pharmaceutical and fine chemical separation purposes in two different ways. In the first alternative, one central rotating valve, as introduced in Section 5.2.3, is used to distribute and collect all inlet and outlet streams. The second design concept switches the ports by means of two-way valves between all columns. While the first approach corresponds to a less complex set-up, the advantage of the second is that higher pressures can be realized and the switching of the individual ports can be handled very flexibly, allowing for implementations like the VariCol process (Section 5.2.5). 

In addition to three- and four-section SMBs, a system with five or more sections can be used if a third fraction is required, see section 5.2.7. These allow for a third product stream in addition to the extract and raffinate. For very strongly retained components a second solid regeneration section can be implemented by introducing a second desorbent stream with higher solvent strength. 

The technology of SMB chromatography has been widely used in the petrochemical (xylene isomer separation) and food industries (glucose-fructose separation) in a multiton scale. Since the 1990s, with the advent of stable chiral stationary 

---

On that basis, crystallization is often used in combination with other enantiose-lective techniques, such as enantioselective synthesis, enzymatic kinetic resolution or simulated moving bed (SMB) chromatography [10, 11]. In general, when referring to crystallization techniques, the aim is to obtain an enantiomeric enrichment in the crystallized solid. However, the possibility of producing an enrichment in the mother liquors [12, 13], even if this is not a general phenomenon [14], must be taken into account. 

The polysaccharide-based CSPs have already been utilized for the preparative separation of pharmaceutical compounds by simulated moving bed (SMB) chromatography, which is a powerful method for the separation of a two-component... 

Advances in preparative enantioseparation by simulated moving bed (SMB) chromatography have occurred in the last 10 years. SMB was invented in the 1960s and was used by the petrochemical and sugar industries. Now with the improvements in stationary phases and hardware it is an option for the large-scale preparation of enantiomerically pure material. The majority of the latest published data are using either amylose- or cellulose-based phases because of their selectivity. There are now examples in the literature of the commercial separation on the multi-ton scale.8... 

The first column based separations performed in a true industrial setting can be better demonstrated by the purification of petroleum on Fuller s earth in the 1920s. The 1950s marked the development of simulated moving bed (SMB) chromatography for the separation of sucrose and fructose in the sugar industry. However, these separations are limited low to medium pressure... 

Continuous simulated moving-bed (SMB) chromatography technique (reviewed by Francotte [423]) may be the method of choice for production scale. 

Devant, R. Jonas, R. Schulte, M. Keil, A. Charton, E, Enantiomer Separation of a Novel Ca-Sensitizing Drug by Simulated Moving Bed (SMB) Chromatography. /, prakt. Chem. 1997,... 

As mentioned before, the complete parallel interconnection of the columns is similar to annular chromatography. The second border case is to connect all beds in series. With an appropriate choice of inlet and outlet streams as well as internal flow rates, this set-up is better known as Simulated Moving Bed (SMB) chromatography. 

Strube, J. Simulation und Optimierung konti-nuierlicher Simulated-Moving-Bed (SMB)-Chromatographie-Prozesse, Dissertation, Uni-versitat Dortmund, 1996. 

The most discernible recent trends in preparative chiral resolution have been the increasing use of supercritical fluid chromatography (SFC) and simulated moving bed (SMB) chromatography, and the fact that Daicel through its US and European Chiral Technologies subsidiaries have offered these as a custom service has played a role in this. 

In simulated moving bed (SMB) chromatography, not only the liquid but also the resin is (simulated to be) in motion . This countercurrent contact allows the continuous fractionation of a feed in two product fractions. The countercurrent operation assures a high driving force towards mass transfer. In the SMB, it is enough when the products exist in the pure form only at the product outlet ports. AU these processes lead to a very efficient use of resin. As a result of the low dilution of products, the consumption of eluent can be reduced compared to fixed bed chromatography. 

An interesting realization of continuous chromatography is simulated moving-bed (SMB) chromatography. Here, a serial connection of several chromatographic columns leads to a continuous simulated countercurrent process. In order to further explain the attribute simulated , first the idea of the true moving bed (TMB) is shown. 

---