Characterization of solid superbases prepared from γ-alumina and their catalytic activity

Solid superbases possessing basic sites stronger than H− = 37 have been prepared from γ-alumina by treatment with alkali metal hydroxides and subsequently with alkali metals. These solid superbases have been characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and X-ray absorption fine structure. Aluminate has been found to be formed on γ-alumina by treatment with alkali metal hydroxide and was supposed to have cationic vacancies. The alkali metal subsequently added to the aluminate is thought to occupy the cationic vacancies and be ionized, introducing electrons to the surface oxygen atoms. The oxygen atoms with increased negative charge are assumed to have an electron pair donating ability strong enough to exhibit superbasicity.