To isolate and purify valued added products in the pharmaceutical industry, for the production of fine chemicals and in biotechnology specific adsorption processes are attractive. Besides applying discontinuous operating modes, as elution and frontal chromatography in the last years the simulated moving bed (SMB) process has been commercialised successfully to solve efficiently several difficult separation problems.
The SMB principle was developed in the early 60th by Universal Oil Products. It consists essentially in using several fixed-beds connected in series. To mimic the attractive countercurrent between the fluid and solid phases a periodic shift of the inlet and outlet positions is applied. This principle was at first applied for large scale separations (e.g. the separation of xylene isomers or of fructose and glucose). Systematic theoretical studies started in the 80th. Criteria to design the process for nonlinear equilibria have been elaborated in the last years. Important advantages of the SMB process leading to a wide range of application are, besides its continuous character, the potential to enhance the productivity and to reduce the solvent consumption compared to conventional discontinuous processes. Currently the SMB technology is of particular interest in the field of performing difficult enantioseparations.
Due to its underlying nonlinearity and its periodic characters the optimisation and the design of SMB processes is still a challenge. There are several new modifications of the standard process under development rendering the process more flexible and powerful.