CATALYTIC PROPERTIES OF LOW-VALENT EUROPIUM INTRODUCED INTO Y-ZEOLITE

Europium was introduced into K+-exchanged Y-zeolite (K-Y) by impregnation from an ammoniacal solution of the metal. The catalytic properties of the zeolite were examined by the isomerization of 2,3-dimethylbut-1-ene to 2,3-dimethylbut-2-ene and the Michael reaction of cyclopent-2-enone with dimethyl malonate. The change in the chemical state of the Eu was investigated by IR and X-ray adsorption fine structure. IR spectrum showed the presence of Eu amide by evacuating the zeolite around 350 K. The amide decomposed successively to Eu imide around 420 K and to Eu nitride around 610 K. The Eu L(3)-edge X-ray absorption near-edge structure (XANES) spectrum showed that the oxidation states of Eu species are Eu2+ (Eu(II)) and Eu3+ (Eu(III)). The change of IR and XANES spectra, and that of the catalytic activity of Eu introduced into K-Y with the evacuation temperature suggest that the Eu(II) imide is the catalytically active species for the isomerization of 2,3-dimethylbut-1-ene and the Michael reaction of cyclopent-2-enone with dimethyl malonate, while the Eu(II) nitride is active species for the hydrogenation of ethene.