Catalytic removal of nitrogen oxides (NO, NO₂, N₂O) from ammonia-fueled combustion exhaust: A review of applicable technologies

Ammonia is an attractive fuel candidate that can reduce fossil fuel consumption and CO₂ emissions owing to its reliable combustion properties, amenability to mass production from renewable resources, and straightforward storage and transportation through existing commercial infrastructure. However, ammonia combustion releases considerable amounts of NO_x into the environment, causing significant air quality problems and health issues. Therefore, appropriate deNO_x techniques must be established to suppress environmental NO_x emissions. However, because ammonia combustion has not yet been commercialized, the composition of ammonia-fueled exhaust gas cannot be readily determined, and existing deNO_x technologies have not been proven to work successfully under practical conditions. Therefore, recent studies on mitigating the NO_x emissions from different ammonia combustion processes are explored in this review. Moreover, applicable catalytic deNO_x technologies, including selective catalytic reduction of NO_x and catalytic N₂O decomposition, are comprehensively scrutinized, with particular emphasis on catalytic materials and their reaction mechanisms. Furthermore, catalyst design considerations and options for each catalytic process are briefly analyzed. Finally, the current technical challenges in this field and future research directions are discussed.