The practical application of robust control design to deal with the problem of thermal excursions of a catalytic hydrodealkylation reactor is addressed. The reactor system is a distributed parameter system, and it consists of a set of five nonlinear partial differential equations. Satisfactory control of this system requires that the control scheme be robust; that is, it must remain stable and perform well in the presence of external disturbances and plant modeling inaccuracies. One approach to solve this design problem is to use the LQG/LTR (linear quadratic Gaussian/loop transfer recovery) method, in which the LTR method is a systematic procedure performed to guarantee the robustness of the LQG controller. The utility of the LQG/LTR approach for designing multivariable controllers to achieve specific performance objectives is examined. The flow velocity of the reactant gas and the volumetric flow-rate of the quench gas are chosen as the manipulated variables. Simulation results obtained with the proposed method exhibit satisfactory capability in attenuating the transient temperature peaks, thus preventing deactivation of catalyst solid, initiation of undesired side reactions, and structural damage to the reactor.