202
OPTICAL AND VIBRATIONAL SPECTROSCOPY
OH
Figure 8.8. FTlR spectra of a y-alumina nanopowder surfaces after activation at 600°C (tracing
a), and after subsequent deuteration (tracing b). [From M.4. Baraton, in Nalwa (2000), Vol. 2,
Chapter 2, p. 1 15.1
the surface. The differences between the y-alumina and the 6-alumina spectra of Fig.
8.9 provide evidence that the two aluminas differ in their allocations of Ai3+ to
octahedral and tetrahedral sites. In hrther work the adsorption of the heterocyclic
six-membered ring compound pyridine, C5H5N, on y-alumina provided FTIR
spectra of the pyridine coordinated to different Ai3+ Lewis acid sites. These infrared
spectral results help clarify the coordination state of aluminum ions in the surface
layer where Lewis acid sites play an important role in the catalytic activity.
3000 2900 2800 2700 2600 2500 2400 2300 2200
Wavenumber (cm-1)
Figure 8.9. Details of FTlR surface spectra in the deuterated hydroxyl (OD) absorption region of
y-Al2O3 (tracing a) and Q-A1203 (tracing b) nanopowders after activation at 500°C followed by
deuteration. [From M.4. Baraton, in Nalwa (2000), Vol. 2, Chapter 2 p. 11 7.1