Al2O3xH2O

Al2O3xH2O is a general designation for hydrated aluminum oxide compounds, representing materials with the empirical formula Al2O3·xH2O where x indicates variable water content. This class includes natural aluminum oxide hydrates as well as synthetic hydrates formed by hydrolysis or partial dehydration of alumina. Because the hydration level can vary, these compounds cover a range of structures from aluminum oxyhydroxides to aluminum hydroxides, before eventual conversion to anhydrous alumina (Al2O3) on heating.

Common natural and synthetic forms lie along this hydration spectrum. Boehmite (AlO(OH)) and diaspore (AlOOH) are widespread natural representatives often described as aluminum oxide monohydrates or related hydrates. Gibbsite (Al(OH)3) is a higher-hydration form. The exact molecular formula can be context-dependent, but the general idea is that water or hydroxyl groups are integrated into the solid lattice. Dehydration or calcination progressively removes water, ultimately yielding various phases of anhydrous alumina.

Structure and properties vary with hydration state. Hydrated forms typically exhibit layered or polymeric networks in which water molecules or hydroxyl groups are bonded within the structure. On heating, these hydrates release water and transform into alumina phases such as γ- or α-alumina, each with distinct stability and properties.

Production and occurrence: Hydrated aluminous minerals occur in bauxite and weathered aluminous rocks. Synthetic hydrates are prepared by controlled hydrolysis, precipitation from aluminum-bearing solutions, or aging of gels; subsequent drying and calcination produce alumina materials used in ceramics, catalysts, and harsh-environment applications.

Uses: Al2O3xH2O materials serve as precursors to alumina in catalysts, adsorbents, polishing powders, ceramics, and refractories. Their hydration state influences processing, phase evolution, and performance.