Environmental Engineering Reference
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(C
2
-
)
g
W
= 2.004
g
W
= 2.011
g
W
= 2.001
(
c
)
g
1
= 1.981
Mn
2
-
3
rd
signal
Mn
2
-
4
th
signal
(
b
)
(
a
)
321
325
329
333
Magnetic ield / mT
Figure 8.15
EPR spectra showing the role of gold on the formation of paramagnetic
peroxo species on Au/Ti-SiO
2
catalyst surface: (a) Au/ Ti-SiO
2
fresh sample before
propylene epoxidation, (b) Ti-SiO
2
at er propylene epoxidation under C
3
H
6
/O
2
/H
2
/
Ar (1/1/1/7 in volume) for 270 min, (c) Au/Ti-SiO
2
at er propylene epoxidation under
C
3
H
6
/O
2
/ H
2
/Ar (1/1/1/7 in volume) for 270 min. Mn
2+
is used as an internal standard.
Reproduced with permission from [92].
H
H
2
H
2
O
2
H
H
O
O
-
O
O
O
O
2
H
2
O
2
Au
0
Ti
4+
Ti
4+
Ti
4+
Au
0
Au
+
O
O
EPR Active
O
UV/vis Active
Figure 8.16
Possible mechanistic model for the formation of hydroperoxo species on Au/
titanosilicate materials. Reproduced with permission from [92].
H
2
+
O
2
O
H
H
O
-
O
O
O
O
O
Si
Ti
Au
Ti
Si
O
O
O
O
O
O
O
O
O
O
Si
Si
Si
Si
Figure 8.17
Probable reaction mechanisms for propylene epoxidation.
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