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d
n
4
r
4
n
g
|
0
Figure 3.10 Proposed structure of the heterotrimetallic Ru/Mn
2
species on HT.
Cl
Ru
O
O
O
O
P
P
.
Structure of Ru
III
-hydroxyapatite (Ru-HAP).
Figure 3.11
Kaneda and co-workers developed a catalyst based on monomeric
ruthenium cations on the surface of hydroxyapatite (Ru-HAP) with the
formula (RuCl)
10
(PO
4
)
6
(OH)
2
, which could also be recycled and displayed a
reasonable substrate scope in aerobic oxidations, although a high loading of
ruthenium (17 mol%) was required for the success of the reaction.
96,97
Examinations of the structure by X-ray absorption near-edge structure
(XANES), k
3
-weighted extended X-ray absorption fine structure (EXAFS) and
other analytical techniques were conducted to estimate the environment of
Ru
III
on HAP (Figure 3.11).
The nanorod crystallites of ruthenium-grafted halogenous hydroxyapatite
(Ru-XAP, X
ΒΌ
F, Cl or Br) were developed as highly ecient catalysts for the
aerobic oxidation of alcohols and, compared with Ru-HAP, the existence of F,
Cl and Br in the hydroxyapatite dramatically enhanced the catalytic activity,
with a high selectivity of more than 99%.
98
In particular, the Ru-ClAP and
Ru-FAP catalysts showed excellent catalytic activity with TOFs of
333 and
210 h
1
, respectively, which were nearly three times higher than those with
Ru-HAP (Figure 3.12). The incorporation of a metal promoter in the HAP
matrix before the introduction of ruthenium dramatically improved the
B
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