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Title: Size-Dependent Catalytic Activity fo Zeolite-Supported Iridium Clusters

Abstract

Iridium carbonyl clusters approximated as Ir{sub 2}(CO){sub 8}, Ir{sub 4}(CO){sub 12}, and Ir{sub 6}(CO){sub 16} were synthesized by carbonylation under various conditions of Ir(CO){sub 2}(acac) sorbed in the cages of zeolite NaY. These supported clusters were decarbonylated by treatment in helium and used to catalyze ethene hydrogenation at atmospheric pressure and temperatures up to 80 C. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to characterize the decarbonylated clusters, which are approximated as Ir{sub 2}, Ir{sub 4}, and Ir{sub 6}, respectively. The data are consistent with the inference that these clusters are the catalytically active species. The catalytic activities and apparent activation energies for ethene hydrogenation depend significantly on the cluster size, with the identity of the most active of the three catalysts depending on the temperature. There appears to be no simple explanation for the variation in catalytic performance with cluster size.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930304
Report Number(s):
BNL-81014-2008-JA
TRN: US200822%%1250
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry C; Journal Volume: 111; Journal Issue: 13
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRIDIUM COMPOUNDS; CARBONYLS; CATALYTIC EFFECTS; CATALYST SUPPORTS; ZEOLITES; ETHYLENE; HYDROGENATION; ACTIVATION ENERGY; national synchrotron light source

Citation Formats

Li,F., and Gates, B.. Size-Dependent Catalytic Activity fo Zeolite-Supported Iridium Clusters. United States: N. p., 2007. Web. doi:10.1021/jp0645521.
Li,F., & Gates, B.. Size-Dependent Catalytic Activity fo Zeolite-Supported Iridium Clusters. United States. doi:10.1021/jp0645521.
Li,F., and Gates, B.. Mon . "Size-Dependent Catalytic Activity fo Zeolite-Supported Iridium Clusters". United States. doi:10.1021/jp0645521.
@article{osti_930304,
title = {Size-Dependent Catalytic Activity fo Zeolite-Supported Iridium Clusters},
author = {Li,F. and Gates, B.},
abstractNote = {Iridium carbonyl clusters approximated as Ir{sub 2}(CO){sub 8}, Ir{sub 4}(CO){sub 12}, and Ir{sub 6}(CO){sub 16} were synthesized by carbonylation under various conditions of Ir(CO){sub 2}(acac) sorbed in the cages of zeolite NaY. These supported clusters were decarbonylated by treatment in helium and used to catalyze ethene hydrogenation at atmospheric pressure and temperatures up to 80 C. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to characterize the decarbonylated clusters, which are approximated as Ir{sub 2}, Ir{sub 4}, and Ir{sub 6}, respectively. The data are consistent with the inference that these clusters are the catalytically active species. The catalytic activities and apparent activation energies for ethene hydrogenation depend significantly on the cluster size, with the identity of the most active of the three catalysts depending on the temperature. There appears to be no simple explanation for the variation in catalytic performance with cluster size.},
doi = {10.1021/jp0645521},
journal = {Journal of Physical Chemistry C},
number = 13,
volume = 111,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}