Application of the xenon-adsorption method for the study of metal cluster formation and growth on Y zeolite
- Korea Advanced Inst. of Science and Technology, Taejon (Korea, Democratic People`s Republic of); and others
Supported metal clusters of Pt, Ir, Ru, Rh, and Pd were prepared in the supercage of Y zeolite by activating their ion-exchanged ammine complexes. Zenon adsorption isotherms obtained from these samples at temperatures ranging from 296 to 340 K and pressures up to 500 Torr, as well as the chemical shift data from the {sup 129}XeNMR study of the adsorbed xenon gas, indicate that the xenon adsorption can occur quite strongly, becoming saturated above ca. 50 Torr, on the metal cluster surface whereas the adsorption is so weak on the support that the adsorbed quantity increases linearly with pressure according to Henry`s law. An application of such a simple technique for the study of Pt cluster formation on NaY zeolite indicates that the size of the Pt cluster formed in the supercage does not change significantly as the metal content is changed from 2 to 10%. This xenon-adsorption method has also been very useful for the study of the formation and growth of the Ru cluster on NaY zeolite. There result indicates that very small Ru clusters are formed in the supercage by treating a precursor, which is prepared by heating NaY zeolite in an aqueous ammonia solution of RuCl{sub 3}, in vacuum at temperatures above 623 K. The clusters grow gradually at high temperatures both in H{sub 2} and under vacuum. The data also agree that an exposure of the supported Ru clusters in O{sub 2} at temperatures above 423 K causes excessive migration of the Ru species, resulting in large agglomeration. Another example, which can further promise wide applicability of the xenon adsorption method, is a study of the formation of Pd clusters in the supercage of various ion-exchanged Y and X zeolites. The result indicates that Ca{sup 2+}, Y{sup 3+}, and perhaps other multivalent cations residing in the supercage are necessary to obtain ca. 1-nm clusters whereas univalent cations give larger clusters.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 171656
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 1 Vol. 114; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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