![Author ORCID: We display the ORCID iD icon alongside authors names on our website to acknowledge that the ORCiD has been authenticated when entered by the user. To view the users ORCiD record click the icon. [opens in a new tab]](https://chemrxiv.org/engage/assets/public/chemrxiv/images/logos/orcid.png)
Abstract
Pd-loaded FER and SSZ-13 zeolites as
low-temperature passive NOx adsorbers (PNA) are compared under practically relevant
conditions. Vehicle cold-start exposes the material to CO under a range of concentrations,
necessitating a systematic exploration of the effect of CO on the performance
of isolated Pd ions for PNA. NO release temperature of both adsorbers decreases
gradually with the increase of CO concentration from a few hundred to a few
thousand ppm. This beneficial effect results from local nano-“hot spots”
formation during CO oxidation. Dissimilar to Pd/SSZ-13, increasing the CO
concentration above ~1,000 ppm improves the NOx storage significantly for
Pd/FER, attributed to the presence of a Pd ions in FER γ-site that is shielded from NOx. CO mobilizes
this Pd atom to the NOx accessible position where it becomes active
for PNA. This behavior explains the very high resistance of Pd/FER to
hydrothermal aging: Pd/FER materials survive hydrothermal aging at 800⁰C in 10% H2O
vapor for 16 hours with no deterioration in NOx uptake/release behavior. Thus,
by allocating Pd ions to the specific microporous pockets in FER, we have
produced very hydrothermally stable and active PNA materials with immediate practical
applications.
