Study On Separation Of Natural Tocopherols By Simulated Moving Bed Chromatography

In the paper, α-tocopherol was firstly separated from mixed tocopherols by a conventional four-zone closed-loop simulated moving bed. Then, a modified feeding mode was sugested to improve the separation process. In the modified feeding mode, the outlet stream from zone Ⅱ is collected at regular intervals.The concentration of the solution is increased by dissolving raw materials and then fed to zone Ⅲ as the feed stream during the next collection interval. Lastly, mixed tocopherols were purified using the column chromatography and a four-zone open-loop SMB. and the purity of mixed tocopherols was increased from10%to80%.In separation of a-tocopherol from mixed tocopherols, eight columns(10mm×100mm) packed with ODS silica gel(10μm) were adopted, the mobile phase was methanol, and the raw material was mixed tocopherols with a purity of90%. When the feed concentration was lOg/L, and the switch interval was5minutes, the suitable flow rates of zones Ⅰ to Ⅳ were5.8,3.5,4,5, and0.8mL/min, respectively.. Under the conditions, the purity and the recovery of a-tocopherol were90.67%and98.98%. When the feed concentration was50.12g/L and the switch interval was5minutes, the suitable flow rates of zones Ⅰ to Ⅳ were6.0,3.8.4.3and1.0mL/min. Under the conditions, the purity of α-tocopherol was98.91%, and the recovery was98.59%.Under the same operating conditions, the purity and recovery of α-tocopherol given by the modified feeding mode were91.51%and97.2%, close the purity and recovery given by the traditional feeding mode of SMB. However, in comparison with the traditional feeding mode, the modified feeding mode increased the productivity by53.49%, and decreased the solvent consumption by34.59%, mainly due to the modified feeding mode of SMB can avoid the raw liquid be diluted.In the purification of mixed tocopherols, the raw materials were pretreated to remove the impurities that are very difficult to be desorbed by a column packed with silica gel. The content of tocopherols was increased from10%to14.67%accordingly. Then the content was further improved to81.3%using a four-zone open-loop SMB consisting of eight columns (10mm× 100mm) packed with silica gel. Three elutents with different compositions flew into zones0, Ⅰ and Ⅱ to desorbent strong component, tocophernols and weak components, respectively. The suitable flow rates of zones0to Ⅲ were3.0,2.8,3.6and4.2mL/min.The switch interval was5minutes.