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The Operating Cycle of NO Adsorption and Desorption in Pd-Chabazite for Passive NOx Adsorbers
Journal article   Peer reviewed

The Operating Cycle of NO Adsorption and Desorption in Pd-Chabazite for Passive NOx Adsorbers

Marvi Kaushik, Gourav Shrivastav, Tuhin S. Khan, M. Ali Haider and Divesh Bhatia
Langmuir, v 37(47), pp 13799-13809
30 Nov 2021
PMID: 34766776

Abstract

Chemistry Chemistry, Multidisciplinary Chemistry, Physical Materials Science Materials Science, Multidisciplinary Physical Sciences Science & Technology Technology
Pd-doped chabazite (Pd/CHA) offers unique opportunities to adsorb and desorb NOx in the target temperature range for application as a passive NOx adsorber (PNA). The ability of Pd/CHA to trap NOx emissions at low temperatures (<200 degrees C) is facilitated by the binding of NOx species at various Pd sites available in the CHA framework. Density functional theory (DFT) simulations are performed to understand Pd speciation in CHA and the interaction of NO with Pd/CHA to explain the mechanisms of NO adsorption, oxidation, and desorption processes. The calculations are used to elucidate the important role of Pd1+ cationic species, anchored at 6MR-3NN, in providing a strong (E-b = -272 kJ/mol) NO adsorption site in Pd/CHA. For NO release, the redox transformation of Pd species comes into play and Pd1+ species are suggested to transform into cationic Pd2+, [PdOH](+), or [Pd-O-Pd](2+) species, all of which show significantly reduced NO binding (-116, -153, and -117 kJ/mol, respectively) as compared to Pd1+. This enables NO desorption at the operating temperature of a downstream catalyst for subsequent catalytic reduction.

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Domestic collaboration
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Web of Science research areas
Chemistry, Multidisciplinary
Chemistry, Physical
Materials Science, Multidisciplinary
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