Simple Rate Expression for Catalyzed Ammonia Decomposition for Fuel Cells

This paper examines NH₃ decomposition rates based on a literature-proven six-step elementary catalytic (Ni-BaZrO₃) mechanism valid for 1 × 10⁵ Pa pressure in a 650–950 K range. The rates are generated using a hypothetical continuous stirred tank catalytic reactor model running the literature mechanism. Excellent correlations are then obtained by fitting these rates to a simple overall kinetic expression based on an assumed slow step, with the remaining steps in fast pseudo-equilibria. The robust overall simple rate expression is then successfully demonstrated in various packed bed reactor applications. This expression facilitates engineering calculations without the need for a complex, detailed mechanism solver package. The methodology used in this work is independent of the choice of catalyst. It relies on the availability of a previously published and validated elementary reaction mechanism.