A Complete Multisite Reaction Mechanism for Low-Temperature NH3-SCR over Cu-CHA
Artikel i vetenskaplig tidskrift, 2020

The dynamic character of the active centers has made it difficult to unravel the reaction path for NH3-assisted selective catalytic reduction (SCR) of nitrogen oxides over Cu-CHA. Herein, we use density functional theory calculations to suggest a complete reaction mechanism for low-temperature NH3-SCR The reaction is found to proceed in a multisite fashion over ammonia-solvated Cu cations Cu(NH3)(2+) and Bronsted acid sites. The activation of oxygen and the formation of the key intermediates HONO and H2NNO occur on the Cu sites, whereas the Bronsted acid sites facilitate the decomposition of HONO and H2NNO to N-2 and H2O. The activation and reaction of NO is found to proceed via the formation of nitrosonium (NO+) or nitrite (NO2-) intermediates. These low-temperature mechanisms take the dynamic character of Cu sites into account where oxygen activation requires pairs of Cu(NH3)(2+) complexes, whereas HO-NO and H3N-NO coupling may occur on single complexes. The formation and separation of Cu pairs is assisted by NH3 solvation. The complete reaction mechanism is consistent with measured kinetic data and provides a solid basis for future improvements of the low-temperature NH3-SCR reaction.

Cu-CHA

NH3-SCR zeolites

reaction mechanism

DFT

Författare

Lin Chen

Chalmers, Fysik, Kemisk fysik

Kompetenscentrum katalys (KCK)

Ton V. W. Janssens

Umicore Denmark ApS

Peter N. R. Vennestrom

Umicore Denmark ApS

Jonas Jansson

Volvo Group

Magnus Skoglundh

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

Kompetenscentrum katalys (KCK)

Henrik Grönbeck

Kompetenscentrum katalys (KCK)

Chalmers, Fysik, Kemisk fysik

ACS Catalysis

2155-5435 (eISSN)

Vol. 10 10 5646-5656

Ämneskategorier

Oorganisk kemi

Teoretisk kemi

Organisk kemi

DOI

10.1021/acscatal.0c00440

Mer information

Senast uppdaterat

2020-07-01