This article deals with the low-order output regulator designs for a commercial-scale packed-bed reactor. Under the static interpolation-based technique for data reconciliation mechanism, the optimum-based two-input control scheme by exploiting the secondary output information can almost attenuate measurable disturbances on the primary output. The steady-state approach not only reduces the critical hot spot and/or thermal runaway but it also dominates the desirable conversion rate in the exit. Moreover, the piece-wise iterative procedure connected with feasible programming evolution for control computation is proposed such that the flexible output regulator with the aid of the 'intelligent' algorithm can effectively improve the transient performance. Simulation results have shown that the non-distributed, piece-wise feedback control scheme turns out to be robust against unknown perturbations. (C) 2003 Elsevier Science Ltd. All rights reserved.