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Selective Catalytic Reduction of NO by NH 3 on Cu‐Faujasite Catalysts: An Experimental and Quantum Chemical Approach
Author(s) -
Delahay Gérard,
Ayala Villagomez Enrique,
Ducere JeanMarie,
Berthomieu Dorothée,
Goursot Annick,
Coq Bernard
Publication year - 2002
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/1439-7641(20020816)3:8<686::aid-cphc686>3.0.co;2-g
Subject(s) - faujasite , catalysis , redox , chemistry , lability , reaction rate constant , zeolite , adsorption , quantum yield , yield (engineering) , inorganic chemistry , reaction rate , quantum chemical , selective catalytic reduction , diffuse reflectance infrared fourier transform , photocatalysis , kinetics , materials science , molecule , organic chemistry , physics , quantum mechanics , metallurgy , fluorescence
The selective catalytic reduction (SCR) of NO by NH 3 in the presence of O 2 on Cu‐faujasite (Cu‐FAU) has been studied. Substitution of some Cu 2+ 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 Cu 2+ (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 H 2 O during the oxidation process.