NOx Storage on BaTi0.8Cu0.2O3 Perovskite Catalysts: Addressing a Feasible Mechanism

The NOx storage mechanism on BaTi0.8Cu0.2O3 catalyst were studied using different techniques. The results obtained by XRD, ATR, TGA and XPS under NOx storage–regeneration conditions revealed that BaO generated on the catalyst by decomposition of Ba2TiO4 plays a key role in the NOx storage process. In situ DRIFTS experiments under NO/O2 and NO/N2 show that nitrites and nitrates are formed on the perovskite during the NOx storage process. Thus, it seems that, as for model NSR catalysts, the NOx storage on BaTi0.8Cu0.2O3 catalyst takes place by both “nitrite” and “nitrate” routes, with the main pathway being highly dependent on the temperature and the time on stream: (i) at T < 350 °C, NO adsorption leads to nitrites formation on the catalyst and (ii) at T > 350 °C, the catalyst activity for NO oxidation promotes NO2 generation and the nitrate formation.

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Combined Fixed-Bed Reactor and In Situ DRIFTS Tests of NO Adsorption on a NOx Storage-Reduction System Catalyst

Chemical Engineering & Technology ◽

10.1002/ceat.201300209 ◽

2013 ◽

Vol 37 (2) ◽

pp. 204-212 ◽

Cited By ~ 5

Author(s):

Dong L. Wu ◽

Valerie Tschamber ◽

Lionel Limousy ◽

Laure Michelin ◽

Alexandre Westermann ◽

...

Keyword(s):

Fixed Bed ◽

Nox Storage ◽

Fixed Bed Reactor ◽

No Adsorption ◽

In Situ Drifts ◽

Nox Storage Reduction ◽

Reduction System

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Elucidating the role of CO in NO storage mechanism on Pd/SSZ-13 with in situ DRIFTS

10.26434/chemrxiv-2021-43n1f ◽

2021 ◽

Author(s):

Inhak Song ◽

Konstantin Khivantsev ◽

Yong Wang ◽

Janos Szanyi

Keyword(s):

Alternative Pathway ◽

Vehicle Exhaust ◽

No Adsorption ◽

Practical Applications ◽

Storage Mechanism ◽

Adsorption Sites ◽

Nox Adsorption ◽

Dry Conditions

Pd ion exchanged zeolites emerged as promising materials for the adsorption and oxidation of air pollutants. For low-temperature vehicle exhaust, dispersed Pd ions are able to adsorb NOx even in H2O-rich exhaust in the presence of carbon monoxide. In order to understand this phenomenon, changes in Pd ligand environment have to be monitored in-situ. Herein, we directly observe the activation of hydrated Pd ion shielded by H2O into a carbonyl-nitrosyl complex Pd2+(NO)(CO) in SSZ-13 zeolite. The subsequent thermal desorption of ligands on Pd2+(NO)(CO) complex proceeds to nitrosyl Pd2+ rather than to carbonyl Pd2+ under various conditions. Thus, CO molecules act as additional ligands to provide alternative pathway through Pd2+(NO)(CO) complex with lower energy barrier for accelerating NO adsorption on hydrated Pd2+ ion, which is kinetically limited in the absence of CO. We further demonstrate that hydration of Pd ions in the zeolite is a prerequisite for CO-induced reduction of Pd ions to metallic Pd. The reduction of Pd ions by CO is limited under dry conditions even at a high temperature of 500°C, while water makes it possible at near RT. However, the primary NO adsorption sites are Pd2+ ions even in gases containing CO and water. These findings clarify additional mechanistic aspects of the passive NOx adsorption (PNA) process and will help extend the NOx adsorption chemistry in zeolite-based adsorbers to practical applications.

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