A tandem simulated moving bed (SMB) process, which consists of two four-zone SMB units (Ring I and Ring II) in series, has been developed previously for complete separation of a ternary bioproduct mixture. In all of previous studies on the optimization of such a tandem SMB process, the adsorbent particle sizes in Ring I and Ring II have been kept the same. To make a further improvement in the performance of a tandem SMB, one can adopt the strategy of making a difference between the adsorbent particle sizes of Ring I and Ring II, which was studied in this paper using the ternary paclitaxel-related mixture as an example separation system. The results showed that the proposed strategy led the adsorbent particle sizes in Ring I and Ring II to be selected in favor of reducing the product dilution of Ring I and reducing the pressure drop of Ring II, respectively. Such pattern of particle-size selection resulted in a marked improvement in the productivity of the tandem SMB of interest, which was confirmed for both the low-pressure and the high-pressure systems. Furthermore, such advantage of the proposed strategy became more pronounced as the selectivity related to the ternary separation was reduced. (C) 2011 Elsevier Ltd. All rights reserved.