One-column chromatograph with recycle analogous to a four-zone simulated moving bed

A one-column chromatograph with recycle analogous to a four-zone simulated moving bed (SMB), called "the analogue", was developed for binary separations. The analogue has one chromatography column connected to a number of tanks equal to the number of steps in the SMB cycle. For example, the analogue to a four-zone SMB with two columns per zone would have eight tanks. The analogue's simple design gives it great flexibility. The analogues and corresponding SMBs were simulated using Aspen Chromatography (v 11.1) for the separation of dextran T6-fructose and dextran T6-raffinose mixtures, which are linear systems, and for the separation of binaphthol enantiomers, which is a nonlinear system. Because of mixing in the tanks, lower purities were obtained with the analogue than with the SMB at equal productivities And desorbent to feed, D/F, values. Therefore, dividing the tanks into several smaller tanks increased the product purities. By increasing D/F from 1.0 to 2.6 (for one column per zone) or to 2.3 (for two columns per zone), the analogue achieved the same purities as the SMB. These increases in D/F are significantly less than the increased amounts of desorbent and adsorbent required for a chromatograph without recycle to obtain the same purity as an SMB.