Effect of cobalt incorporation on the stability of ionic Pd in the presence of carbon monoxide over Pd/BEA passive NOx adsorbers

Condition‐dependent NOx adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

“…The peaks at 2140, 1650, and 1590 cm −1 that were observed over HBEA are also present during NO x ‐DRIFTS over Pd/BEA (Figure 3B). Two new peaks at 1877 and 1845 cm −1 were observed in NO x ‐DRIFTS over Pd/BEA compared to HBEA, which can be attributed to NO adsorption over ionic Pd species 38 . A decrease in the intensities of the P‐HAl(OH) (3782 cm −1 ) and Brønsted acid site (3731 and 3606 cm −1 ) peaks (Figure 3C) after NO x exposure over Pd/BEA suggests that Pd incorporation does not fully occupy the NO x adsorption sites (P‐HAl(OH) and Brønsted acid sites) on HBEA.…”

“…Two new peaks at 1877 and 1845 cm À1 were observed in NO x -DRIFTS over Pd/BEA compared to HBEA, which can be attributed to NO adsorption over ionic Pd species. 38 A decrease in the intensities of the P-HAl (OH) (3782 cm À1 ) and Brønsted acid site (3731 and 3606 cm À1 ) peaks (Figure 3C) after NO x exposure over Pd/BEA suggests that Pd incorporation does not fully occupy the NO x adsorption sites (P-HAl (OH) and Brønsted acid sites) on HBEA. Therefore, NO x can be adsorbed on ionic Pd and the P-HAl(OH), Brønsted acid sites of HBEA zeolite under the NO x -only condition over Pd/BEA.…”

Charge Shielding Effect of Sodium Ions in Improving The Hydrophobicity and Performance of Co/Na‐SSZ‐13 Zeolite for Passive NOx Adsorber

“…Subsequently, Kyriakidou et al found that Co can stabilize Pd 2+ ions and maintain the NO x adsorption/desorption efficiency of PdCo/BEA during consecutive NO x + CO adsorption/desorption cycles. [22] Okubo et al developed a novel Co/Zn-doped zeolitic imidazolate framework-derived carbon nanoparticles as PNAs and the highly dispersed Co species are considered as the active adsorption sites. [21] Besides, Badawi et al also present a screening approach based on density functional theory (DFT) calculations to evaluate the adsorption capability of NO x on FAU zeolites modified with alkali and alkali-earth metals (Li + , Na + , K + , etc.…”

“…found that Co can stabilize Pd 2+ ions and maintain the NO x adsorption/desorption efficiency of PdCo/BEA during consecutive NO x + CO adsorption/desorption cycles. [ 22 ] Okubo et al. developed a novel Co/Zn‐doped zeolitic imidazolate framework‐derived carbon nanoparticles as PNAs and the highly dispersed Co species are considered as the active adsorption sites.…”

Mechanistic insight in the propylene derived distinct NO uptake and release behaviors on Pd/SSZ-13 for low-temperature NO adsorption

“…To meet the increasingly stringent regulations, it is necessary to directly eliminate NO x from the exhaust at the low temperatures encountered during cold start. The temporary storage of NO x is a promising approach to control the cold start emissions below 150 • C [7,[9][10][11][12]. The stored NO x is released once the exhaust temperature has increased and is subsequently converted by the downstream catalysts.…”