An efficient optimization tool is developed based on the standing-wave design for simulated moving bed (SMB) systems with nonlinear isotherms and significant mass-transfer effects. A maximum operating pressure is considered in the optimization. Both system parameters (particle size, column length, column diameter, total number of columns, column configuration, and feed concentration) and operating parameters (zone flow rates and switching time) are optimized to achieve the maximum productivity or the minimum separation cost. Under a pressure limit, medium particle size (10-40 mu m), short columns (5-15 cm), and a longer zone 11 give higher productivity and lower separation cost. Nonlinear effects resulting from high feed concentration can decrease productivity and increase separation cost. High-pressure SMB systems (5.2 MPa) can have higher productivity, but low- and medium-pressure SMB systems (1.0 and 2.4 MPa, respectively) are more economical.