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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.