Nanocluster catalyst lives longer

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Nanocluster catalyst lives longer Chinese
chemists report a rhodium nanocluster catalyst
that demonstrates "unprecedented" lifetime and
activity in benzene hydrogenation under forcing
conditions (J. Am. Chem. Soc. 2005, 127, 9694).
The rhodium nanoclusters, which tend to coalesce
into bulk metal on their own, are stabilized by
the novel combination of a pyrrolidone-substituted
, ionic-liquidlike copolymer (shown) dissolved in
an imidazolium ionic liquid. The total turnovers
for the catalyst--a measure of catalytic
lifetime--exceeded 20,000 over five runs, which
is more than five times the previous record for
benzene hydrogenation by a nanocluster catalyst.
Yuan Kou and coworkers at Peking University
suggest that the high stability and activity of
the rhodium catalyst are due to the combined
stabilizing influences of the ionic liquid and
the pyrrolidone-substituted copolymer. The
stabilized rhodium nanoclusters, each roughly 3
nm across, were synthesized by hydrogenation of a
mixture of RhCl33H2O and the copolymer dissolved
in the ionic liquid.
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Rhodium Nanoparticles Stabilized by Ionic
Copolymers in Ionic Liquids Long Lifetime
Nanocluster Catalysts for Benzene Hydrogenation
Xin-dong Mu, Jian-qiang Meng, Zi-Chen Li, and
Yuan Kou,
J. Am. Chem. Soc. 2005, 127, 9694
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TTO (total turnovers)193000
(a catalytic lifetime record for olefin
hydrogenation by soluble nanoparticles)
(n-C4H9)4N5Na3(1,5-COD)Rh P2W15Nb3O62
Aiken, J. D. Finke, R. G. J. Am. Chem. Soc.
1999, 121, 8803-8810.
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TTO (total turnovers)2600
Widegren, J. A. Finke, R. G. Inorg. Chem. 2002,
41, 1558-1572.
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IrCl(cod)2 (cod 1,5-cyclooctadiene) /
BMIPF6 RhCl3 3H2O /
BMIPF6 Pt2(dba)3 / BMIPF6 Ru(cod)(cot)
(cot1,3,5-cyclooctatriene) / BMIPF6
TTO 3509 (32h) (a catalytic lifetime record for
arene hydrogenation by soluble nanoparticles)
4 atm
Fonseca, G. S. Fonseca, A. P. Teixeira, S. R.
Dupont, J. Chem.-Eur. J. 2003, 9, 3263-3269.
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a zwitterionic imidazolium sulfonate-terminated
thiol (zwitter-Au)
Tatumi, R. Fujihara, H. Chem. Commun. 2005,
83-85.
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Zhao, D. Fei, Z. Geldbach, T. J. Scopelliti,
R. Dyson, P. J. J. Am.Chem. Soc. 2004, 126,
15876-15882.
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Clement, N. D. Cavell, K. J. Jones, C.
Elsevier, C. J. Angew. Chem.,Int. Ed. 2004, 43,
1277-1279.
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1,10-phenanthroline
Huang, J. Jiang, T. Han, B. X. Gao, H. X.
Chang, Y. H. Zhao, G. Y. Wu, W. Z. Chem.
Commun. 2003, 14, 1654-1655.
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1-vinylimidazole
Soluble in BMIM ILs and MeOH
AIBN azobisisobutyronitrile
RX bromoethane butylchloride
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RhCl33H2O / copolymers dissolved in BMIBF4
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TTO
phen
4000
.
PVP
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Mercury poisoning experiments The ability of
Hg(0) to poison metal-particle heterogeneous
catalysts, by amalgamating the metal or
adsorbing on the metal surface.
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Conclsion
1. Containing imidazolium ionic liquidlike units
have been synthesized. Rhodium nanoparticles
stabilized by the ionic copolymer in ionic
liquids have been successfully obtained. 2.
The nanoparticles showed unprecedented lifetime
and activity in arene
hydrogenation under forcing conditions (a
temperature of 75 C and a hydrogen pressureof
40 bar) with a TTO of 20 000 (in five total
recycles of 4000 TTOs each) and a TOF of 250 h-1,
demonstrating that the combination of ionic
liquids with ionic liquidlike stabilizers is a
pathway towards highly stable and active
nanoparticle catalysts.