The [(NH<sub>3</sub>)<sub>4</sub>Cu<sub>2</sub>O<sub>2</sub>]<sup>2+</sup>‐Peroxo Complex as the Key Intermediate for NH<sub>3</sub>‐SCR Activity and Deactivation of Cu‐CHA Catalysts.
Ton V. W. Janssens, Elisa Borfecchia, Kirill A. Lomachenko, Henrik Grönbeck, Gloria Berlier
Abstract
Abstract In NH 3 ‐SCR over Cu‐CHA catalysts in the low‐temperature range 150–300 °C, the activation of oxygen occurs via oxidation of a pair of mobile (NH 3 ) 2 Cu I ‐complexes located in the cages of the zeolite. In this step, a reactive [(NH 3 ) 4 Cu 2 O 2 ] 2+ ‐peroxo complex (μ‐η 2 ,η 2 ‐peroxo diamino dicopper(II)‐complex) is formed. The chemistry of this complex determines several catalytic properties of the Cu‐CHA catalyst. The reaction of NO with the [(NH 3 ) 4 Cu 2 O 2 ] 2+ ‐peroxo complex governs the NH 3 ‐SCR activity. A reaction of the [(NH 3 ) 4 Cu 2 O 2 ] 2+ ‐peroxo complex with ammonia hinders the reaction of NO with the complex, thus leading to an inhibition of the NH 3 ‐SCR reaction. Finally, the deactivation in presence of SO 2 is due to a reaction of SO 2 with the [(NH 3 ) 4 Cu 2 O 2 ] 2+ ‐peroxo complex, leading to the formation of Cu−S compounds in the catalyst. In this review, the characterization and the reactions of the [(NH 3 ) 4 Cu 2 O 2 ] 2+ ‐peroxo complex with NO, NH 3 , and SO 2 , and mean‐field kinetic models based on first principles calculations for NH 3 ‐SCR activity and SO 2 poisoning are discussed.