Experimental assessment of different NOx storage catalysts for transient emission management in DI H2 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 after-treatment 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.