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 NOx into the environment, causing significant air quality problems and health issues. Therefore, appropriate deNOx techniques must be established to suppress environmental NOx emissions. However, because ammonia combustion has not yet been commercialized, the composition of ammonia-fueled exhaust gas cannot be readily determined, and existing deNOx technologies have not been proven to work successfully under practical conditions. Therefore, recent studies on mitigating the NOx emissions from different ammonia combustion processes are explored in this review. Moreover, applicable catalytic deNOx technologies, including selective catalytic reduction of NOx 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.