Continuous separation of glucose and fructose by simulated moving bed

Abstract

The continuous separation of glucose and fructose mixtures has been studied at 50$^\circ$C in a three section simulated moving bed cascade ( or semicontinuous chromatographic refiner ; SCCR ). The experiments were explored with two parts, one at low concentration (10 g/L of both sugars) and the other at high concentration (up to 500 g/L of both sugars). The equipment was made of twelve 1-cm-diameter 30-cm long stainless steel coumns packed with $Ca^{++}$ form of ion exchange resin, DOWEX 40W 12X 200-400, linked alternately top and bottom to form a closed loop. The mass transfer characteristics of both sugars were investigated with the practical model which included the liquid film, intraparticle, and axial dispersion resistance. Form the chromatographic responses, the influence of such parameters on the concentration profiles in the column could be investigated using the method of moments. The equilibrium constants of both sugars at low concentration were obtained from the first absolute moment of pulse test and the kinetic parameters could be obtained from the second central moment and the known equilibrium constant. Contribution of individual resistance on HETP was investigated. While the liquid film resistance was negligibly small, the intraparticle resistance was dominant. The intraparticle resistance of fructose was greater than that of glucose due to the formation of complex of fructose with $Ca^{++}$ ion in the resin. Although the degree of eddy diffusivity was unity in the ordinary liquid systems, this value was about ten fold in this system. Thus the axial dispersion resistance cannot be neglected. But this term is included in the overall effective rate coefficient so that the plug flow model can predict the chromatographic responses as close as the axially dispersed plug flow model. The distribution coefficients at high concentration were obtained by measuring the retention volume of the breakthrough curves. These values had the concentration dependen...