Pt Species in Zeolite X: Catalytic Activity in18O Exchange of O2with Zeolitic Oxygen,18O2–16O2Equilibration, H2–D2Equilibration, and the CO–NO Reaction
Pt Species in Zeolite X: Catalytic Activity in18O Exchange of O2with Zeolitic Oxygen,18O2–16O2Equilibration, H2–D2Equilibration, and the CO–NO Reaction
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DOI：
10.1006/jcat.1997.1534
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发表时间：
1997-03
影响因子：
7.3
通讯作者：
J. Nováková;L. Brabec
中科院分区：
文献类型：
--
作者：
J. Nováková;L. Brabec
Abstract Pt 0 , Pt 2+ and Pt ox were prepared by different treatments of platinum tetrammine complexes in alkali faujasites. The observed behavior of Pt, especially in TPR experiments, provided evidence that the decomposition of ammine complexes in an oxygen stream yields predominantly Pt cations, which following reduction by hydrogen leads to the formation of small metallic clusters, whose reoxidation gives Pt ox in zeolite cavities. The activity of both latter species was markedly higher than that of Pt 2+ in the reaction studied, i.e., in the isotopic exchange of gaseous oxygen with the oxygens of the zeolite framework, in the equilibration of hydrogen and oxygen molecules (D 2 +H 2 and 18 O 2 + 16 O 2 reaction, respectively), and in the NO reduction by CO. The catalytic reactions were studied over NaX and KX zeolites. Isotopic exchange of 18 O 2 with zeolitic oxygen occurred even below 400°C, oxygen activated on Pt centers (3Pt per unit cell) being spilled over to the oxygen of the zeolite skeleton. The equilibration of the gaseous oxygen molecules began above 300°C, while that of hydrogen molecules was easily measured at −78°C.
