True moving bed chromatography: Solid-liquid multi-stage counter-current extraction

An apparatus for solid-liquid multi-stage dual-flow counter-current extraction was created for performance of true moving bed chromatography. Using the 12-vessel apparatus, continuous adsorptive separation of methyl- and propyl-4-hydroxybenzoate was accomplished using octadecyl-silica gel as the solid phase, and a mixture of water-1-propanol (8:2) as the liquid phase. From a 1:1 mixture of methyl and propyl esters, methyl ester was extracted into the liquid phase at a purity of 98.83% and propyl ester was recovered from the solid phase by desorption with the same liquid phase to 95.89% purity. Copyright (C) 1999 Elsevier Science B.V.