The cross-flow chromatographic separation of carbohydrate mixtures

Abstract

Reviews are given of the theoretical aspects of chromatography and of continuous chromatographic techniques. A pilot-scale rotating annular chromatograph has been constructed consisting of two concentric cylinders which form an annulus 1.4m in length and 12mm wide. The annular space is filled with ion-exchange resin. The upper and lower surfaces of the annulus are enclosed by stainless steel flanges. The entire bed is rotated slowly at speeds of up to four revolutions per hour. Feed solutions are introduced via a Stationary inlet distributor into a layer of glass beads at the upper surface of the column packing. Deionised water as eluent is also introduced to the upper surface of the packing. Each component in the feed mixture has a different retention time within the resin. The rate of travel of each solute combined with the rotation of the annulus causes each component to exit the annulus at a different position. Products pass through the lower stainless steel flange and into a stationary collector beneath the annulus. Several carbohydrate mixtures have been separated with varying degrees of success. Glucose has been separated from its isomer fructose in synthetic solutions and in inverted beet molasses. Mixtures of glucose, fructose and sucrose have also been resolved quite successfully. These separations were carried out on Purolite PCR 833 ion exchange resins in the Ca2+ form. Sucrose has been separated from betaine and other non-sugars in ordinary beet molasses using Duolite C211/2558 ion exchange resin in the Na+ form. A total throughput of 309 hl sugar solids has been shown to be readily achievable to give 300g h™' glucose (4.8% w/v concentration, 90% purity) and 240g h"! fructose (2.6% w/v concentration, 90% purity). This corresponds to a specific throughput of 56.8 Kg sugar solids m3 resin h-1. A computer simulation program has been developed which can be used to predict quite accurately the peak positions and peak bandwidths of solutes leaving the annulus, product purities, yields and throughputs.