Theoretical Study on the NOₓ Selective Catalytic Reduction on Single-Cu Sites and Brønsted Acid Sites in Cu-SSZ-13
2021
Goncalves, Tiago J. | Plessow, Philipp N. | Studt, Felix
The mechanism of the Cu-SSZ-13-catalyzed selective catalytic reduction (SCR) of NOₓ with NH₃ is investigated for single-Cu sites. Barriers are determined for all elementary steps and calculated with high accuracy using DLPNO-CCSD(T) single-point calculations on large 46T cluster models derived from periodic density functional theory (DFT) calculations. For standard SCR, NO oxidation to NO₂ is necessary, which requires barriers above 250 kJ/mol on single-Cu sites, indicating that they are not catalytically active for this process. Contrary, for fast SCR, the barriers are below 150 kJ/mol, indicating that single-Cu sites are active. Most of the elementary reactions, such as the required N–N bond formation between NO and NH₃ take place on the single-Cu sites. After the N–N bond formation, which yields H₂NNO, however, the intermediate is most easily decomposed into N₂ and H₂O on a Brønsted acid site.
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