AVS 57th International Symposium & Exhibition
    Surface Science Thursday Sessions
       Session SS-ThM

Invited Paper SS-ThM1
Adsorption and Reaction on Poorly Crystalline γ-Al2O3 Surfaces

Thursday, October 21, 2010, 8:00 am, Room Picuris

Session: Adsorption and Reactivity on Oxide Surfaces
Presenter: C.H.F. Peden, Pacific Northwest National Laboratory
Authors: J.H. Kwak, Pacific Northwest National Laboratory
D. Mei, Pacific Northwest National Laboratory
R.J. Rousseau, Pacific Northwest National Laboratory
J. Szanyi, Pacific Northwest National Laboratory
Y. Wang, Pacific Northwest National Laboratory
C.H.F. Peden, Pacific Northwest National Laboratory
Correspondent: Click to Email
γ‑alumina (γ‑Al2O3), one of the metastable ‘transition’ alumina structural polymorphs, is an important catalytic material both as an active phase and as a support for other catalytically active phases, with widespread applications ranging from petroleum refining to automotive emission control. As such, the bulk and surface structure of γ‑Al2O3, and its formation and thermal stability have been and continue to be the subject of a considerable research. However, due to the low crystallinity and very fine particle size of γ‑Al2O3, it is very difficult to apply well-established analytical techniques for determining its surface structures. Of particular importance for understanding the catalytic properties of γ‑alumina, relating its surface structure to the origin of Lewis and Brönsted acidity has been of considerable interest and has been studied by solid state NMR and FTIR spectroscopies, and most recently by theoretical calculations. In this presentation, we describe recent studies using ultra-high resolution NMR spectroscopy as an especially useful probe of the γ‑Al2O3 surface structure, and its relevance to catalytic behavior. In particular, we coorelate the NMR spectra with measurements of the adsorption and reaction of light alcohols. In this way, we demonstrate a strong dependence of this chemistry on the presence of specific 5-coordinate Al3+ ions. These sites, in turn are a function of the dehydration temperature of the alumina material before use. From these correlations, we are able to explain a considerable number of prior observed phenomena.