Hydrothermal aging effects on Cu-zeolite NH3-SCR catalyst

• Characterization of the catalyst material variations due to aging treatment.
• Construction of a kinetic model accounting for the impact of aging on NH3-SCR.
• Model validation on NH3-TPD experiments involving catalysts with different extents of aging.
• The evolution of the kinetic parameters with aging was found to be in agreement with the material evolution.

After-treatment systems for diesel vehicles face a challenge for upcoming emission regulations. Regarding the level of nitrogen oxides (NOx) and soot required, the global catalytic activity of the exhaust line needs to be improved. Hydrothermal aging conditions explored during particulate filter regeneration are very stringent for the deNOx catalyst and can strongly reduce its durability. Ammonia selective catalytic reduction (NH3-SCR) systems mainly based on copper or iron exchanged zeolite catalysts have emerged as effective technologies to reduce NOx emissions with their durability being continuously improved. In this work, we evaluated the impact of different hydrothermal treatments on a commercial copper-exchanged zeolite catalyst. The goal was to link the catalytic material property changes with catalytic performance changes as a function of both aging duration and temperature. The evolution of the zeolite structure as well as the changes of the copper state were experimentally investigated. Based on a detailed material properties analysis of Cu-zeolite, a semi-detailed kinetic model of has been built to quantitatively predict adsorption and desorption of NH3 as a function of hydrothermal aging conditions. This work is a first step to bridge the gap between lab analysis conclusions and global reactivity observed in real conditions.

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