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Table 5 Evaluation of EXAFS refinement of dehydrated VxOy/SBA-15.

From: Structural characterization of vanadium oxide catalysts supported on nanostructured silica SBA-15 using X-ray absorption spectroscopy

  

V2O5, procedure #1

V2O5, procedure #2

Hydrated VxOy-SBA-15

Type

N

Z

± z

F

Z

± z

F

Z

± z

F

V - O

1

1.58

0.05

0.3

1.58

0.011

0

1.65

0.014

0

σ2(V-O)

3(1)

0.011

0.0055

0.8

0.0104

0.0069

0

0.0126

0.0003

0

V - O

3(2)

1.87

0.06

0.3

1.88

0.014

 

1.92

0.018

0

σ2(V-O)

-(3)

0.0098

0.004

0.8

-

-

-

-

-

-

V - O

-(1)

1.93

0.03

0.5

-

-

-

-

-

-

V - V

2

3.12

0.006

0

3.11

0.003

0

3.08

0.0075

0

σ2(V-V)

3

0.0047

0.00032

0

0.0047

0.00035

0

0.013

0.0006

0

V - V

1

3.39

0.044

0

3.38

0.046

0

3.42

0.046

0.3

V - V

2

3.60

0.024

0

3.59

0.024

0

3.65

0.028

0

E0

-

0.38

17.0

0.9

-

-

-

-

-

-

  1. V K edge XAFS parameters (Z for distances R and disorder parameter σ2) obtained from two different procedures of fitting a model structure (i.e. V2O5) to the experimental XAFS FT(χ(k)*k3) of reference V2O5 and hydrated VxOy/SBA-15 (10.8 wt %) (details of fit given in Table 6) together with confidence limits (± z, referring to 95% of fit residual) and significance parameter F (details given in text). Fit residual 6.0 for V2O5 procedure #1, 6.3 for V2O5 procedure #2, and 13.6 for hydrated VxOy-SBA-15.
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BMC Chemistry

ISSN: 2661-801X

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