Infrared Spectroscopy and Redox Studies of Co exchanged Europium and Iron in Y Zeolite

M. A, ULLA; L. APARICIO; J. DUMESIC; W. MILLMAN

JOURNAL OF CATALYSIS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 1989 vol. 117 p. 237 - 245

0021-9517

Carbon monoxide and nitric oxide chemisorption on europium-exchanged Y-zeolite and on Eu and Fe coexchanged Y-zeolite was studied using infrared spectroscopy. Redox studies were carried out gravimetrically to determine the extent of oxidation-reduction for the cations, the reactivity, and the average oxidation state under different ratios of oxidant and reductant. EuY was found to reduce with difficulty whereas EuFeY underwent a more facile reduction, yet not as easily as FeY. The EuFeY catalyst was found to operate at near its fully oxidized state under CO: O 2 ratios of 10:1. In contrast, the oxidation state of FeY is dictated by the overall stoichiometry of the gas phase. For example, a 2: 1 CO: O 2 ratio results in an average oxidation state of +2.5. The time dependence of the NO spectral areas upon exposure of reduced EuFeY to NO exhibits changes similar to those found for FeY, except for the initial exposure. These data are consistent with Eu forcing Fe into sites of higher accessibility. This phenomenon has also been seen for Fe in Y-zeolites with silicon-to-aluminum ratios larger than 2.5. The time dependence of the infrared bands upon exposure to NO is consistent with migration of the Fe into new sites, as was found earlier for FeY