Catalytic cracking of ammonia and combustion of cracked ammonia: An integrated system for industrial applications - Mini review

Abstract

Ammonia is increasingly recognised as a key enabler for achieving global low-emission targets, serving both as a hydrogen carrier and an energy vector suitable for long-distance transport. In the near term, it is expected to play an important transitional role until renewable hydrogen becomes cost-competitive. Within the ammonia energy value chain, catalytic decomposition (cracking) forms the core of the ammonia-to-hydrogen pathway, while direct combustion provides the ammonia-to-power pathway. Catalytic cracking typically operates at 500-800 degrees C and can generate hydrogen-rich mixtures with controllable cracking rates (CRs) of 20-80%, enabling partial decomposition to tailor fuel reactivity. Such hydrogen enrichment has been shown to increase laminar burning velocities by more than twofold compared with pure ammonia and to broaden flammability limits, while thermally integrated configurations can recover approximately 60-85% of combustion heat to supply the endothermic cracking demand. This review summarizes recent progress, challenges, and prospects of catalytic ammonia cracking and the combustion of cracked ammonia fuel blends, followed by system-level discussions of heat integration and performance trade-offs. Advances in cost-effective catalysts and reactor designs are examined alongside combustion characteristics, nitrogen oxide (NOx/N2O) formation mechanisms, and mitigation strategies. Finally, emerging integrated systems and commercial developments are highlighted, and key technical barriers-including heat matching, emissions control, and durability - are identified to guide future deployment of ammonia-based clean energy technologies.