Semi-batch operation is currently used in the pharmaceutical or fine chemical industry. Control of such an operation is difficult to ensure by conventional PID as operating conditions and operations change a lot even for the same apparatus. So it is very important in the fine chemical industry to maintain the flexible and multipurpose characters of batch reactors during their automation. This study deals with adaptive thermal control of different kinds of operation (heating, cooling, exothermic reactions carried out in a semi-batch jacketed pilot reactor. Experimental results show the robustness of the algorithm in respect to strong disturbances, its ability of tracking high nonlinear setpoint trajectories and its good control qualities during various chemical reactions.