Adsorption and reaction of alcohols on poorly crystalline Al₂O₃ surfaces

γ-alumina is an important catalytic material both as an active phase and as a support for other catalytically active phases, with applications ranging from petroleum refining to automotive emission control. Of particular importance for understanding the catalytic properties of γ-alumina, relating its surface structure to the origin of Lewis and Bronsted acidity has been of considerable interest and has been studied by solid state NMR and FTIR spectroscopies, and most recently by theoretical calculations. Here, we describe recent studies using ultra-high resolution NMR spectroscopy as an especially useful probe of the 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, demonstrating 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.