Theoretical Study on the NO<i><sub>x</sub></i> Selective Catalytic Reduction on Single-Cu Sites and Brønsted Acid Sites in Cu-SSZ-13
Tiago J. Goncalves, Philipp N. Pleßow, Felix Studt
Abstract
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.