Hydrogen production via ammonia decomposition: Kinetic analysis
S. R. M. Coelho, José Matos, Cláudio Rocha, M.A. Soria, Luı́s M. Madeira
Abstract
Ammonia (NH 3 ) has emerged as a promising hydrogen carrier due to its high hydrogen content, favourable storage and transport properties, and carbon-free utilisation. Its ability to be stored as a liquid under relatively mild conditions and its compatibility with existing industrial infrastructure make it an efficient and scalable solution for hydrogen distribution. This study conducts a detailed investigation into the kinetics of ammonia decomposition over ruthenium-based catalysts, which are known for their high catalytic activity for ammonia cracking. Experimental data across a wide range of operating conditions are used to validate the proposed models with a promising catalyst (0.5 wt.% Ru/Al 2 O 3 ). The study employs kinetic models based on different theoretical frameworks, such as the Langmuir isotherm, the Temkin-Pyzhev approach, and the microkinetic model, focusing on evaluating various rate-determining steps. A comparison of these models shows that those that consider nitrogen desorption a rate-determining step provide the best predictions of NH 3 conversion, effectively capturing the dependencies on temperature and feed molar fractions of reactants and products. This multi-faceted approach integrates experimental data with proposed kinetic models, contributing to a better understanding of NH 3 decomposition through parameter optimisation. The findings provide valuable insights for modelling catalytic reactors, optimising conditions and enhancing catalyst performance for efficient hydrogen production from ammonia.