Multiscale modeling of a low‐temperature <scp> NH ₃ </scp> decomposition reactor for precious metal reduction and temperature control

Abstract Ammonia is a carbon‐free energy carrier with 17.6 wt% hydrogen content. The design of an efficient and compact ammonia decomposition reactor based on low‐temperature catalysts is the key to realizing industrial hydrogen production from ammonia. In this work, a multiscale model was developed by bridging the particle‐scale characteristics of catalysts and reactor performances, to fully comprehend the ammonia decomposition process. The effects of catalyst porosity and pore diameters on the reactor size, precious metal loading, and the profile of temperature and heat flux were systematically evaluated. An improved reactor design was further proposed by applying the segmented reactor packed with two‐stage egg‐shell‐type low‐temperature catalysts, which decreased the precious metal usage by 61.6% and the temperature drop by 42.9 K. This segmentation strategy balanced the reaction rate and heat flux, indicating a significant potential in highly efficient, economical, and reliable hydrogen production from ammonia.