Hydrogen Production via Ammonia Decomposition: Kinetic Analysis

Ammonia (NH3) 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 rutheniumbased 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/Al2O3). 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 ratedetermining step provide the best predictions of NH3 conversion, effectively capturing the dependencies on temperature and feed molar fractions of reactants and products. This multifaceted approach integrates experimental data with proposed kinetic models, contributing to a better understanding of NH3 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.