Separation of Organic Compounds by Gradient Simulated Moving Bed Chromatography

Abstract

A promising solution for the separation of organic compounds in pharmaceutical industry is the gradient simulated moving bed chromatography (SMB). The above mentioned process can be used for the production of high purity materials (isomers, optical isomers, biomolecules). We assumed isotherm, isochor equilibrium adsorption (competitive multicomponent Langmuir-adsorption equilibrium) in the mathematical model and neglected the effects of axial dispersion. In our present work we extended the mathematical model with solvent adsorption-desorption processes (acetone-dichloromethane eluent, steroid compounds, silicagel). The mathematical model was solved by finite differences numerical mathematical method using PC. The gradient SMB separations were carried out with a laboratory scale four column equipment in open loop system at 1:1:2:0 column configuration. The SMB equipment (L=25 cm, I.D.=1 cm) was planned and constructed for separation of a steroid mixture using YMC S-50 silica gel as adsorbent (specific surface=798.63 m g). The effect of switching time change (5.5 min, 9 min, 11.5 min, 22.5 min) on component separation was examined. During our measurements the amount of acetone in dichloromethane was 55 % v/v in the fresh eluent and pure dichloromethane in the feed. The process variables of the gradient SMB (product purity, yield, productivity, specific solvent consumption) are very favourable. Our conclusion is that the measured and the calculated data agree well and we have produced more than 99.9 %m/m purity and 90 % yield , productivity 1300-3000 g steroid kg adsorbent day at 0.1-0.3 m fresh eluent kg steroid eluent consumption.