A mathematical model is used to simulate a bench-scale membrane reactor for the decomposition of ammonia over Ni/Al2O3 catalyst. Since the reaction is equilibrium limited the removal of the product hydrogen by the membrane derives the thermodynamic equilibrium. For further displacement of the thermodynamic equilibrium, auxiliary methanation reactions over Ni/Mg Al2O4 catalyst are used to remove part of hydrogen. The two catalysts are loaded together in different pattern configurations. The purpose of this study is to investigate the effect of catalyst patterns on ammonia decomposition. Optimal conditions are observed and explanations offered. An effective length criterion for the optimal conditions is presented. The results show that the pattern strategies have substantial improvement in the reactor performance in terms of high conversions, low temperatures and reduced mass of the catalyst used. The investigation, although is restricted to two catalyst layers, has uncovered a part of the rich characteristics of this system.