Spatially Resolved Measurements in a Stagnation-Flow Reactor: Kinetics of Catalytic NH3 Decomposition

A stagnation-flow reactor was employed to investigate the decomposition of ammonia over a Ni/Al₂O₃ catalyst across a range of system pressures and ammonia mole fractions. The results indicate that the system pressure has a negligible impact on the light-off behavior and the concentration profiles of NH₃. A comparison of 1D modelling with 3D computational fluid dynamics (CFD) computations justifies the use of the simpler flow model. Good agreement between experiments and the 1D simulation is achieved for two different kinetic models from literature in the mainly diffusion-controlled regime. For lower temperatures, at which the process is kinetically controlled, the two mechanisms exhibit significant differences. The stagnation-flow reactor concept is shown to be a promising tool for understanding, developing, and validating the reaction kinetics of heterogeneous catalytic processes.