AbstractOptimal control of concurrent nonlinear tubular reactors for complex reaction system is studied. The jacket side temperature is allowed to vary along the reactor length and with time. The optimal control possesses feedforward component only, and the nonlinear gain may be precomputed. For a Denbigh type of reaction system, if the heat generation is negligible, the control temperature is insensitive to feed concentration variations. With heat generation effect present, the optimal control is time dependent, and the nonlinear feedforward gain is obtained. The gain may be approximated by a linear function to construct a simple linear feedforward control loop which contains a synchronized time delay.