Ultrahigh Resolution STEM and NMR Studies of Poorly Crystalline γ–Al2O3 Surfaces: New Insights From Imaging and Spectroscopy

Abstract

γ-alumina, 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-alumina, and its formation and thermal stability, have been and continue to be the subject of a considerable amount of research [1]. However, due to the low crystallinity and very fine particle size of γ-alumina, 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 acidity has been of considerable interest and has been studied by solid state nuclear magnetic resonance (NMR) [2] and fourier transform infrared (FTIR) [3] spectroscopies, and most recently by theoretical calculations