Optimization of a simulated-moving-bed process for continuous separation of racemic and meso-2,3-butanediol using an efficient optimization tool based on nonlinear standing-wave-design method

•Comprehensive optimization of SMB for 2,3-butanediol isomer separation was conducted.•The optimization tool based on nonlinear standing-wave-design was prepared and used.•The highest production rate occurred at the feed concentration and column length.•Where their effects on nonlinearity, loading amount, and pressure drop were balanced.•The best SMB conditions in favor of production rate and productivity were clarified. The feasibility of using a simulated-moving-bed (SMB) process for continuous-mode separation of biotechnologically produced 2,3-butanediol (BD) into racemic-BD and meso-BD has been verified recently. One of the important tasks for facilitating the industrial application of such a BD-isomer separation SMB is to make a substantial improvement in its production rate and/or productivity while meeting the requirements on BD-isomer purities and pressure drop. To address this issue, the comprehensive optimization for a BD-isomer separation SMB was attempted in this study. First, an efficient SMB optimization tool based on a Langmuir isotherm standing-wave-design method was prepared and then applied to comprehensively optimizing the operation and system parameters of the considered SMB. The results revealed that the production rate (Prate), under a given column length, could reach its maximum when feed concentration (Cfeed,BD) was selected at the one where the negative effect of nonlinearity increase on Prate could be balanced with the positive effect of Cfeed,BD increase on Prate. The Prate could be improved further by modulating column length (Lc) to be a little lager than the Lc leading to a maximum in feed flow rate (Qfeed), which was effective in increasing Cfeed,BD high enough to outweigh the resultant decrease of Qfeed. It was also found that the productivity (Prod) could be enhanced by adopting the Lc smaller than that for a maximum in Qfeed, which could allow a sufficiently large savings of adsorbent to outweigh the resultant decrease of Qfeed and Cfeed,BD. Finally, it was confirmed that the comprehensively optimized SMB in this study could lead to more than 17 times the Prate and Prod, compared to the previously reported BD-isomer separation SMB.