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

Nitrogen oxides (NOx) are a type of reactive nitrogen (Nr) 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 NOx 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 NOx storage and reduction (NSR) process, applying a gas-switching operation between storage of NOx 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.