Activated Alumina vs. Ordinary Alumina
A brief comparison between activated alumina and ordinary alumina.
Activated Alumina vs. Ordinary Alumina
Although both activated alumina and ordinary alumina belong to the Al₂O₃ family, they differ fundamentally in crystal structure, physical properties, and applications.
Crystal Structure Differences
Ordinary alumina (α-Al₂O₃) is the most stable form of alumina, commonly known as corundum. Its crystal structure is dense, with aluminum and oxygen ions tightly packed together, and almost no porosity.
Activated alumina (γ-Al₂O₃, etc.) is a transition state alumina, obtained by dehydrating aluminum hydroxide at low temperatures. Its crystal structure is loose and porous, containing numerous irregular micropores and mesopores.
Comparison of Physical Properties
Characteristics | Ordinary alumina | Activated alumina |
Main crystalline phases | α-Al₂O₃ | γ-Al₂O₃ |
Specific surface area | <10 m²/g | 200-400 m²/g |
Porosity | Extremely small | 0.3-0.8 cm³/g |
Hardness | Mohs 9 | Medium |
Surface properties | Chemically inert | Rich in hydroxyl groups, highly reactive |
Heat resistance | Melting point approximately 2050℃ | transforms into the α phase at high temperatures, losing its activity. |
Application Areas Differences
The applications of ordinary alumina are mainly based on its high hardness, high heat resistance, and chemical stability:
Refractory materials: refractory bricks, crucibles
Grinding and polishing: grinding wheels, polishing powders
Electronic ceramics: circuit board substrates, high-voltage insulators
Synthetic gemstones: rubies, sapphires
The applications of activated alumina are mainly based on its high specific surface area and surface activity:
Adsorption and drying: compressed air drying, natural gas dehydration, reducing gas dew points to below -55℃
Catalyst carriers: petroleum hydrocracking, automotive exhaust purification
Water treatment: drinking water defluorination
Summary
Ordinary alumina focuses on high hardness and high-temperature resistance, suitable for structural materials; activated alumina focuses on adsorption and catalytic functions, suitable for finishing applications. Both have the same chemical composition, but their crystal structure and physical properties determine their respective applications. The correct material type should be selected based on actual needs. We are a Chinese activated alumina supplier. For more information, please contact us at annayu@169chem.net or WhatsApp +8618909016373.