Electron Paramagnetic Resonance Spestroscopy Studies of Eu Y and Coexchanged EuFe Y Zeolite

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

JOURNAL OF CATALYSIS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 1990 vol. 123 p. 195 - 205

0021-9517

Electron paramagnetic resonance (EPR) was used to probe the oxidation state of europium and the location of divalent europium cations in EuY and EuFeY zeolite samples. Europium was present as trivalent cations following treatment in O 2 at 770 K. Treatments in HZ or CO at 770 K led to formation of divalent cations, and perhaps also caused some reduction to lower oxidation states. Three EPR signals were observed for Eu 2+, giving rise to effective g values of 3, 4.9, and 6. The first and last signals are interpreted as being due to Euz+ cations at sites I and 11, respectively, while the latter signal is due to Euz+ cations at sites I′ and II′. The majority of the Eu 2+ cations are at site I, and the amount of Eu at this site can be increased by reducing the sample in Hz, compared with reduction in CO. The presence of europium in site I forces the Fe 2+ cations to occupy sites of lower coordination in the sodalite unit (sites I′ and II′) and in the supercages (sites II and III′).