High-Temperature Reaction Mechanism of NH3-SCR over Cu-CHA: One or Two Copper Ions?
Journal article, 2024

Cu-exchanged chabazite (Cu-CHA) shows good performance for selective catalytic reduction of nitrogen oxides using NH3 as a reducing agent (NH3-SCR). The temperature dependence of the activity has a characteristic nonmonotonic behavior with a minimum in the range 300-350 °C. The minimum signals that different reaction mechanisms or active sites dominate at low and high temperatures. The low-temperature mechanism is believed to occur over a pair of mobile [Cu(NH3)2]+ complexes, whereas the high-temperature mechanism should proceed over framework-bound Cu ions. To explore the NH3-SCR reaction over framework-bound Cu ions, we use first-principles calculations combined with mean-field microkinetic simulations. We find that the reaction proceeds over a single framework-bound Cu ion and that the first step is NO and O2 coadsorption. The coadsorption competes with NH3 adsorption, and the NH3-SCR rate is largely determined by the adsorption energy of NH3. Combining the high-temperature kinetic model with our previous low-temperature model for NH3-SCR over pairs of mobile [Cu(NH3)2]+ complexes makes it possible to describe the nonmonotonic behavior of the reaction rate. The work provides a detailed mechanistic understanding of the role and transformation of different forms of Cu ions during low- and high-temperature standard SCR in Cu-CHA.

Author

Yingxin Feng

Chalmers, Physics, Chemical Physics

Ton Janssens

Umicore

Peter Vennestrøm

Umicore

Jonas Jansson

Volvo Group

Magnus Skoglundh

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Henrik Grönbeck

Chalmers, Physics, Chemical Physics

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 128 16 6689-6701

KCK - Kompetenscentrum Katalys 2022-2026

Preem (KCK2022-2026), 2022-01-01 -- 2026-12-31.

Johnson Matthey (2500123383), 2022-01-01 -- 2026-12-31.

Scania CV AB (Dnr:2021-036543Pnr:52689-1), 2022-01-01 -- 2026-12-31.

Umicore Denmark ApS (KCK2022-2026), 2022-01-01 -- 2026-12-31.

Volvo Group (PO:2435702-000), 2022-01-01 -- 2026-12-31.

Subject Categories

Inorganic Chemistry

Physical Chemistry

Atom and Molecular Physics and Optics

Materials Chemistry

DOI

10.1021/acs.jpcc.4c00554

More information

Latest update

5/11/2024