Preparation of iridium clusters in zeolite Y via cation exchange: EXAFS, xenon adsorption, and {sup 129}Xe NMR studies
- Korea Advanced Institute of Science and Technology, Taejon (Korea, Democratic People`s Republic of)
The conversion of [Ir(NH{sub 3}){sub 5}Cl]{sup 2+} and [Ir(NH{sub 3}){sub 5}(H{sub 2}O)]{sup 3+} to 1-nm Ir clusters entrapped in the supercages of NaY zeolite has been investigated by using {sup 129}Xe NMR spectroscopy, xenon adsorption, and extended X-ray absorption fine structure. The cation exchange with [Ir(NH{sub 3}){sub 5}Cl]{sup 2+} was achieved by slurring NaY in an aqueous solution of [Ir(NH{sub 3}){sub 5}Cl]Cl{sub 2} at room temperature. The cation exchange with [Ir(NH{sub 3}){sub 5}(H{sub 2}O)]{sup 3+} employed either an aqueous solution of [Ir(NH{sub 3}){sub 5}(H{sub 2}O)](ClO{sub 4}){sub 3} at room temperature of an aqueous solution of IrCl{sub 3} containing NH{sub 3} at a temperature of 330 K. This paper reports very distinctive pretreatment requirements for the transformation of these two ionic precursors to 1-nm Ir clusters in the zeolite supercages: activation in O{sub 2} flow at 573 K is required in the case of [Ir(NH{sub 3}){sub 5}(H{sub 2}O)]{sup 3+}, prior to the final reduction with H{sub 2}. This second method, which has not been previously described, provides a convenient route for the preparation described, provides a convenient route for the preparation of Ir clusters in zeolites without using an oxidative treatment, and avoiding Cl-containing species. Furthermore, results from {sup 129}Xe NMR and xenon adsorption measurements indicate that the cluster size is substantially smaller than that in the case of [Ir(NH{sub 3}){sub 5}Cl]{sup 2+}. 17 refs., 12 figs., 3 tabs.
- OSTI ID:
- 110977
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 149; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
Similar Records
Application of the xenon-adsorption method for the study of metal cluster formation and growth on Y zeolite
sup 129 Xe NMR of silver-exchanged X- and Y-type zeolites