Utilization of Reactive Nitrogen Compounds for Nitrogen Circular Economy.

Nitrogen oxides (NO) should be purified according to environmental regulations, being restricted increasingly year by year. A wide variety of denitration technologies, such as selective catalytic reduction (SCR) of NO to nitrogen (N) and NO storage reduction (NSR) to N by injecting reducing agents like ammonia (NH), has so far been developed practically. Sophisticated catalytic approaches are perhaps mandatory for the sustainability in energy including complete purification of NO. As one of the solutions to overcome problems for environment and resource simultaneously, this concept article focuses on the utilization of reactive nitrogen (N) compounds, mainly NO, for encouraging an opening to consider nitrogen circular economy. For the recycling of NO via NH, a challenging but rational catalytic technology can be proposed by an alternate switching the inlet gas between NO containing oxidative gas and H containing reductive one without an operation to change the reaction temperature. Considering the reactivity of NO higher than that of N, this kind of NO to NH (NTA) process is promising for synthesizing NH, being valuable not only as fertilizer but also as fuel in near future.