Significant Insights into the Gas-switching Process between NO_x Storage and Reduction to NH₃

Abstract

Nitrogen oxides (NO_x) are a type of reactive nitrogen (N_r) harmful to the human body and the environment and should be converted to harmless nitrogen (N₂) before release into the atmosphere. In recent years, the higher reactivity of NO_x compared to N₂ has resulted in occasional use as raw materials for the synthesis of valuable chemicals such as ammonia (NH₃). We are proposing a modified NO_x storage and reduction (NSR) process, applying a gas-switching operation between storage of NO_x in combustion gas and selective reduction by hydrogen (H₂), for the catalytic conversion to NH₃. This review describes significant insights on the functions of catalyst components (e.g., noble metal catalyst and metal oxide support) for the synthesis of NH₃ during the gas-switching NSR process using nanocomposite catalysts, which were identified with commercially available metal oxide supports.