Chromatographic fractionation of a ternary mixture with an SMB cascade process: The effect of ion exchange resin cross-linkage on separation efficiency

In this study, the effect of cation exchange resin cross-linkage (4.8-8.0 wt% of DVB) on separation efficiency in fractionation of a ternary mixture with a two-step cascade simulated moving bed process was investigated experimentally and by simulations. The recovery of betaine and sucrose from sugar beet molasses containing sulfate salts was chosen as a case study. Betaine was recovered in the first step, and sucrose in the second step. Strong effect of cross-linkage on the separation efficiency in both steps was observed. In betaine recovery, the efficiency increased with increasing cross-linkage of the resin due to stronger ion and size exclusion. The increase of cross-linkage from 5.2 wt% to 8.0 wt% increased productivities of betaine and sucrose by 107% and 61%, respectively. Water consumption decreased simultaneously by 50% and 58%, respectively. No separation could be achieved with 4.8 wt% cross-linked resin. In sucrose recovery, the decrease in cross-linkage from 8.0 wt% to 5.2 wt% was found to increase sucrose productivity by 180% and decrease water consumption by 50%. Further decrease of cross-linkage resulted in decreased separation efficiency. The results clearly demonstrate that the proper choice of separation material cross-linkage not only significantly improves the separation efficiency in fractionation of molasses, but also in other relevant separation cases as well. In the case of ternary separations, it is beneficial to optimize the resin cross-linkage for each separation step.