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(380a) Towards Rational Synthesis and Molecular Level Understanding of Pd/Zeolite Passive NOx Adsorber (PNA) Materials

Authors: 
Khivantsev, K., Pacific Northwest National Laboratory
Jaegers, N., Pacific Northwest National Laboratory
Cui, Y., Pacific Northwest National Laboratory
Tao, F., The University of Kansas
Kovarik, L., Pacific Northwest National Laboratory
Aleksandrov, H. A., University of Sofia
Vayssilov, G. N., University of Sofia
Hanson, J. C., Brookhaven National Laboratory
Wang, Y., Pacific Northwest National Laboratory
Gao, F., Pacific Northwest National Laboratory
Szanyi, J., Pacific Northwest National Laboratory
Removal of criteria pollutant NOx species from diesel engine exhaust is a challenge for current lean NOx control technologies. Substantial decrease in the amount of released NOx has been achieved by the successful development and commercialization of NH3 selective catalytic reduction (SCR) technology. SCR catalysts rely on NH3 supply from urea transformation > 180 °C. Furthermore, they perform effectively at temperature > 250 °C. During cold start, most of NOx emissions escape into the atmosphere. To address this issue, Passive NOx adsorber (PNA) materials, capable of storing NOx at low temperature and releasing it > 200 °C, are being developed. Herein, we focus specifically on Pd/Zeolite PNA materials. We systematically study structure-storage performance relationships for a wide range of Pd/Zeolite materials and determine the important factors that govern their PNA activity and response to hydrothermal aging. Advanced spectroscopic and synchrotron characterization techniques coupled with DFT calculations allow us to gain molecular-level insight into various active PNA species. This provides a pathway to PNA materials with impressive performance under industrially relevant conditions.

Acknowledgements:

The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.