Experimental Assessment of Different NO x Storage Catalysts for Transient Emission Management in DI H ₂ Fueled ICE

One of the emerging technologies to effectively decarbonize the transportation sector in the Heavy-Duty and Non-Road segment is the Hydrogen fueled Internal Combustion Engine (H₂-ICE). Although completely free of carbon content, and therefore CO₂, the H₂-ICE exhaust still releases NOx as harmful byproducts of the combustion process. Furthermore, it is well known that H₂-ICE NOx emissions are very sensitive to combustion air-to-fuel ratio (λ) and hence are much higher during load increase when λ is lowered (λ<2) to reach the target level of performance. Therefore, to comply with most stringent emission regulations, it is paramount to equip the H₂-ICE with an aftertreatment system capable to handle the NOx peaks generated during transient operations with extremely high efficiency. The present work provides indication for the transposition of catalyst formulations well-known for compression-ignited ICE to Direct Injection H₂-ICEs for effectively storing and converting NOx within their combustion boundaries. Different catalysts were characterized throughout a series of lab reactor tests where the gas species measured in the H₂-ICE exhaust stream were provided with defined combinations and assessed with respect to NOx storage capacity, NOx conversion efficiency, NH₃ production. This research work demonstrates the influence of the O₂/H₂ ratio in the gas mixture on the catalytic performance.