An improved standing-wave design method is developed for nonlinear simulated moving bed (SMB) systems with significant mass-transfer effects and an operating pressure limit. The design method was verified with rate model simulations and then tested for enantioseparation of phenylpropanolamine. High purity (>99%) and high yield (>99%) were achieved experimentally using a SMB with a pressure limit of 350 psi. The verified design method was used to find the optimal column length that gives the maximum throughput per bed volume. For a given particle size and a pressure limit, the optimal column length falls on the boundary between the masstransfer-limiting region and the pressure-limiting region. If a characteristic dispersion velocity is more than 0.2% of an interstitial velocity, mass-transfer effects must be considered in the design in order to guarantee 99% purity and yield.

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in Wiley InterScience (www.interscience.wiley.com).Multiobjective optimization of simulated moving bed systems for chiral separations is studied by incorporating standing wave design into the nondominated sorting genetic algorithm with jumping genes. It allows simultaneous optimization of seven system and five operating parameters to show the trade-off between productivity, desorbent requirement (DR), and yield. If pressure limit, product purity, and yield are fixed, higher productivity can be obtained at a cost of higher DR. If yield is not fixed, it can be sacrificed to achieve higher productivity or vice versa. Short zones and high feed concentration favor high productivity, whereas long zones favor high yield and low DR. At fixed product purity and yield, increasing the pressure limit allows the use of smaller particles to increase productivity and to decrease DR. The performance of low-pressure simulated moving bed can be improved significantly by using shorter columns and smaller particles than those in conventional systems.

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