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Article Dans Une Revue ChemPhysChem Année : 2002

Selective Catalytic Reduction of NO by NH3 on Cu-Faujasite Catalysts: An Experimental and Quantum Chemical Approach

Résumé

The selective catalytic reduction (SCR) of NO by NH3 in the presence of O2 on Cu-faujasite (Cu-FAU) has been studied. Substitution of some Cu2_ with H_ and Na_ cations, compensating for the negative charge of the zeolite framework, forms the various CuHNa-FAU studied. The amount of Cu was held constant and the proportion of H_ and Na_ varied in the sample. The substitution of Na_ for H_ increases sharply the SCR rate by lowering the temperature of reaction by about 150 K. It is proposed that the rate increase mainly comes from an unhindered migration of Cu from hidden to active sites and a modification of the redox properties of Cu species. The former was demonstrated by diffuse reflectance IR spectroscopy of adsorbed CO. The change in redox properties was demonstrated by a faster oxidation of Cu_ to Cu2_ (rate-determining step). Quantum chemical calculations on model clusters of CuHNa-FAU indicate that the faster rate of oxidation can be explained by a higher lability of protons in the absence of Na, which can be then removed from the catalyst more easily to yield H2O during the oxidation process.

Domaines

Catalyse

Dates et versions

hal-00178383 , version 1 (11-10-2007)

Identifiants

Citer

Gerard Delahay, Enrique Ayala Villagomez, Jean-Marie Ducéré, Dorothée Berthomieu, Annick Goursot, et al.. Selective Catalytic Reduction of NO by NH3 on Cu-Faujasite Catalysts: An Experimental and Quantum Chemical Approach. ChemPhysChem, 2002, 318, pp.686-692. ⟨10.1002/1439-7641(20020816)3:8<686::AID-CPHC686>3.0.CO;2-G⟩. ⟨hal-00178383⟩
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