Structure and Characterization of Supported Ruthenium--Cobalt Bimetallic Catalysts

Author： Guczi L. Sundararajan R. Koppany Z. Zsoldos Z. Schay Z. Mizukami F. Niwa S.

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.167, Iss.2, 1997-02, pp. : 482-494

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Abstract

Ruthenium, cobalt, and ruthenium-cobalt bimetallic samples, supported on SiO 2 , Al 2 O 3 , and NaY zeolite, were characterized by temperature-programmed reduction, CO chemisorption, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Temperature-programmed reduction revealed that the reducibility for cobalt increases in the order NaY < SiO 2 < Al 2 O 3 , while for ruthenium the sequence was Al 2 O 3 < NaY < SiO 2 . If Ru/NaY samples are calcined in oxygen, then ruthenium migrates to the external surface of NaY and agglomerates, while in the case of He-treated zeolite samples the ruthenium metal particles are stabilized in the supercage in the range of 1 to 3 nm average diameter, as measured by X-ray diffraction, CO chemisorption, and transmission electron microscopy. Cobalt ions are irreducible when they are exchanged alone or first in the NaY zeolite for the bimetallic sample Ru-Co/NaY[ I ]. Here the reduction of Ru 3+ ions is not affected by the presence of cobalt, whereas when Ru 3+ ions exchanged first into NaY (Ru-Co/NaY[ II ]), the cobalt ions are easily reduced and bimetallic particles are formed but the migration of ruthenium particles to the outer surface of NaY zeolite is hampered.