The main goal of this research is modeling and real time optimization of an industrial steam methane reformer considering catalyst deactivation. In the first step, the reformer is heterogeneously modeled based on the mass and energy balance equations considering a detailed kinetic model. To prove the accuracy of developed model, the simulation results are compared with the available plant data at steady state condition. In the second step, based on the mechanism of catalyst deactivation, a first order decay model is proposed and the parameters of the model are calculated to minimize the absolute difference between calculated methane conversion and plant data. In the third step, an optimal control problem is formulated to maintain hydrogen production capacity at the desired level. Based on the formulated optimization problem, optimal dynamic trajectories of feed temperature and steam to methane ratio are calculated considering two strategies. Then, the performance of developed optimization procedure is proved considering furnace temperature and feed concentration as disturbance. The simulation results show that operating at the proposed optimal condition increases hydrogen production about 11.6%. In addition, the process emission performance defined as hydrogen to carbon dioxide ratio in the product is 6.72 and 7.03 at the conventional and optimized conditions, respectively. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.