A Complete Multisite Reaction Mechanism for Low-Temperature NH3-SCR over Cu-CHA
Journal article, 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.

NH3-SCR zeolites


reaction mechanism



Lin Chen

Competence Centre for Catalysis (KCK)

Chalmers, Physics, Chemical Physics

Ton V. W. Janssens


Peter N. R. Vennestrom


Jonas Jansson

Volvo Group

Magnus Skoglundh

Competence Centre for Catalysis (KCK)

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

Henrik Grönbeck

Competence Centre for Catalysis (KCK)

Chalmers, Physics, Chemical Physics

ACS Catalysis

2155-5435 (eISSN)

Vol. 10 10 5646-5656

Subject Categories

Inorganic Chemistry

Theoretical Chemistry

Organic Chemistry



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