The structures of bimetallic CuPt particles in freshly reduced and outgassed CuPt/NaY zeolites were characterized by extended X-ray absorption fine structure (EXAFS) at the Cu K-edge and Pt L3-edge. In order to understand the effect of copper on the coordinative environment of platinum, reduced Cu/NaY and Pt/NaY were also studied. It is found that the structure of CuPt bimetallic particles is dependent on the atomic ratio of Cu and Pt in the zeolites. At room temperature, some of the Cu atoms are oxidized, presumably by reacting with protons on the zeolite surface. By outgassing in helium at 500°C, additional Cu atoms were leached from the surface of the CuPt particles to expose more Pt atoms on the surface. Thus, an enhancement in the activity of toluene hydrogenation was observed. Due to the leaching of Cu atoms upon outgassing in helium or under vacuum, hydrogen chemisorption is not an appropriate method to estimate the number of surface Pt atoms in bimetallic CuPt particles supported in NaY.
Bimetallic copper-platinum particles supported in Y zeolite: structural characterization by EXAFS / Ming Sing, Tzou; Michiko, Kusunoki; Kiyotaka, Asakura; Haruo, Kuroda; Moretti, Giuliano; Wolfgang M. H., Sachtler. - In: THE JOURNAL OF PHYSICAL CHEMISTRY. - ISSN 0022-3654. - STAMPA. - 95:13(1991), pp. 5210-5215. [10.1021/j100166a054]
Bimetallic copper-platinum particles supported in Y zeolite: structural characterization by EXAFS
MORETTI, GIULIANO;
1991
Abstract
The structures of bimetallic CuPt particles in freshly reduced and outgassed CuPt/NaY zeolites were characterized by extended X-ray absorption fine structure (EXAFS) at the Cu K-edge and Pt L3-edge. In order to understand the effect of copper on the coordinative environment of platinum, reduced Cu/NaY and Pt/NaY were also studied. It is found that the structure of CuPt bimetallic particles is dependent on the atomic ratio of Cu and Pt in the zeolites. At room temperature, some of the Cu atoms are oxidized, presumably by reacting with protons on the zeolite surface. By outgassing in helium at 500°C, additional Cu atoms were leached from the surface of the CuPt particles to expose more Pt atoms on the surface. Thus, an enhancement in the activity of toluene hydrogenation was observed. Due to the leaching of Cu atoms upon outgassing in helium or under vacuum, hydrogen chemisorption is not an appropriate method to estimate the number of surface Pt atoms in bimetallic CuPt particles supported in NaY.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
