Investigation of NOX reduction via NH3-SCR in aftertreatment systems for hydrogen internal combustion engines

Abstract

Hydrogen internal combustion engines (H2-ICEs) are gaining interest as a route to meet Euro 7 emission standards and carbon neutrality goals. However, their exhaust-rich in water vapor, oxygen, and hydrogen-poses challenges for NOx control. This study evaluates the NH3-SCR performance over a Cu/CHA catalyst under H2-ICE-relevant conditions (H2O:1-20 vol%, O2:1-14 vol%, and H2 0/500 ppm, 150-490 degrees C). NH3-TPD revealed reduced NH3 uptake with increasing water. NH3 oxidation and low-temperature SCR activity declined with higher H2O while high-temperature conversion improved. Above 250 degrees C, NOx conversion exceeded 99% regardless of water concentration at 60,000 h-1 GHSV. Increasing water concentration from 1 to 20 vol% resulted in lower NO conversion but with less transient NH3 inhibition behavior. H2 co-feed affected high-temperature deNOx efficiency but had minimal impact between 150 and 400 degrees C. A kinetic model was developed which captured Standard, Fast SCR and NH3 inhibition behavior under a wide range of water concentrations.