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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