Abstract

The activated aluminas comprise a series of nonequilibrium forms of partially hydroxylated aluminum oxide, Al₂O₃. The chemical composition can be represented by (OH)_2x where x ranges from about 0 to 0.8. They are porous solids made by thermal treatment of aluminum hydroxide precursors and find application mainly as adsorbents, catalysts, and catalyst supports. Activated alumina, for purposes of this discussion, refers to thermal decomposition products (excluding -alumina) of aluminum trihydroxides, oxide hydroxides, and nonstoichiometric gelatinous hydroxides. The term “activation” is used to indicate a change in properties resulting from heating (calcining). In general, as a hydrous alumina precursor is heated, hydroxyl groups are driven off, leaving a porous solid structure of activated alumina. The physical properties of the material are set by the choice of precursor, the forming process, and the activation conditions. Activated alumina is a relatively innocuous material from a health and safety standpoint. It is nonflammable and nontoxic. Normal precautions associated with handling of nuisance dusts should be taken. Activated alumina is normally shipped in moisture-proof containers because of its strong desiccating action.