Disclosed are systems, servers and methods for improving temperature profile control in a reactor with at least three fixed beds, exothermic reactions and interstage cooling. A model of the temperature differential across the first bed is developed and its error is used to infer unmeasured feed composition disturbances, which are used in the control of the downstream fixed beds for faster response to unmeasured feed composition changes and improved control of the temperature profile throughout the reactor. The first bed model error is then used as an input into an overall model that predicts reactor temperature profiles, which provides advanced notice of reactions in downstream beds, and enables efficient adjustment and compensation to a feed composition change. A Model Predictive Control (MPC) algorithm is applied to adjust the bed intercooling and first bed feed temperature so that the reactor temperature profile can be more precisely controlled.