What is Activated Alumina?
Activated alumina is a highly porous form of aluminum oxide (Al₂O₃) manufactured by dehydroxylating aluminum hydroxide (Al(OH)₃) at controlled temperatures between 300-600°C. The resulting γ-Al₂O₃ phase has an extremely high surface area (typically 200-400 m²/g) and a network of pores ranging from nanometers to tens of nanometers, making it one of the most effective and economical industrial desiccants.
Activated alumina is characterized by its high crush strength (≥130 N per bead), low attrition rate, and excellent water adsorption capacity (typically 20-30% by weight). Unlike silica gel, it does not swell or fragment when saturated, and unlike molecular sieves it is far more economical for bulk applications. Aluminaworld manufactures activated alumina in both spherical (ball) and powdered forms, with strict quality control on pore volume, surface area, and mechanical strength.
Technical Specifications
Activated Alumina Ball — Two Standard Grades
| Parameter | Standard Grade | High-Purity Grade |
|---|---|---|
| Al₂O₃ Content (%) | ≥92 | ≥93 |
| SiO₂ (%) | ≤0.10 | ≤0.05 |
| Fe₂O₃ (%) | ≤0.04 | ≤0.03 |
| Na₂O (%) | ≤0.45 | ≤0.30 |
| Surface Area (m²/g) | ≥300 | ≥320 |
| Pore Volume (ml/g) | ≥0.40 | ≥0.45 |
| Bulk Density (g/ml) | 0.70-0.80 | 0.72-0.85 |
| Crush Strength (N/颗) | ≥130 | ≥150 |
| Attrition Rate (wt%) | ≤0.4 | ≤0.3 |
| Water Adsorption (%) | ≥50 | ≥55 |
Standard Particle Sizes — Balls
- 1-3mm — Fine-grade for instrument air dryers and small desiccant beds
- 2-5mm — Most popular universal size for compressed air dryers
- 3-5mm — Standard for industrial air/gas drying towers
- 4-6mm — Large-bed drying, lower pressure drop
- 5-8mm — Very large drying columns, defluoridation filters
Activated Alumina Powder Specifications
| Parameter | Specification |
|---|---|
| Al₂O₃ Content (%) | ≥92 |
| Particle Size | 50-200 mesh (custom available) |
| Surface Area (m²/g) | ≥280 |
| Bulk Density (g/ml) | 0.55-0.70 |
| Color | White powder |
| Main Application | Catalyst preparation, polishing compound feedstock, desiccant in specialty applications |
Six Major Industrial Применение
1. Compressed Air Drying — Industry's Workhorse Desiccant
Activated alumina is the most widely used desiccant in industrial compressed air dryers, particularly twin-tower heatless regenerative dryers. It achieves pressure dew points of -40°C to -50°C, sufficient for most industrial pneumatic systems, instrumentation, and process air applications. Compared to molecular sieve, activated alumina is more economical and tolerant of feed air contamination.
2. Transformer Breathing — Protecting Electrical Insulation
Power transformers use silica-gel or activated alumina breathers to dry the air that enters the conservator tank during load cycling. Moisture ingress is the #1 cause of transformer failure worldwide. Activated alumina breathers protect millions of dollars of electrical equipment in power plants and substations. Typical replacement interval: 1-2 years depending on humidity.
3. Drinking Water Defluoridation — WHO-Recommended Solution
Activated alumina is the gold-standard adsorbent for removing excess fluoride from drinking water in communities where natural groundwater exceeds 1.5 mg/L. It reduces fluoride from 10 mg/L to below 0.5 mg/L, well within WHO guidelines. Capacity: approximately 1,800 bed volumes per cycle before regeneration with NaOH. Used in India, China, Africa, and rural USA.
4. Natural Gas Dehydration
Activated alumina is widely used in natural gas dehydration, particularly in smaller fields and wellhead applications. It reduces water content from saturated conditions to 10-50 ppm, sufficient for pipeline transport. While molecular sieve 4A is preferred for deep drying, activated alumina offers the best cost-performance ratio for medium-pressure applications.
5. Catalyst Carrier — Petrochemical Industry
Activated alumina spheres serve as premium catalyst carriers in numerous petrochemical processes: Claus sulfur recovery (Claus converters), H₂O₂ production (anthraquinone process), selective hydrogenation, FCC catalyst additives, and various oxidation reactions. High surface area, uniform pore structure, and thermal stability make it ideal for these demanding applications.
6. Industrial Gas Drying (N₂, O₂, H₂, Ar)
Compressed industrial gases (especially air separation plants producing N₂ and O₂) require drying before cryogenic processing. Activated alumina provides cost-effective bulk water removal as a pre-dryer stage, often paired with molecular sieve 13X for deep polishing to sub-ppm levels.
Comparison vs Silica Gel and Molecular Sieve
| Property | Activated Alumina | Silica Gel | Molecular Sieve 4A |
|---|---|---|---|
| Dew Point Achievable | -50°C | -40°C | -90°C |
| Water Capacity (wt%) | 20-30% | 35-40% | 22% |
| Crush Strength (N/颗) | 130+ | 30-50 (low) | 30+ |
| Wear Rate | Very Low | High (fragments) | Low |
| Regeneration Temp | 180-250°C | 120-150°C | 200-300°C |
| Best For | Air drying, water, transformer | Bulk drying, food packaging | Deep drying, gas purification |
| Cost (relative) | Low-Medium | Low | Medium-High |
| Resistant to contamination | Good | Poor (swells) | Poor (clogs) |
Frequently Asked Questions
Q: What is activated alumina used for?
A: Activated alumina has four main industrial uses: (1) compressed air drying and desiccant in industrial gas dryers; (2) water defluoridation for drinking water purification; (3) transformer breathing - protecting electrical insulation from moisture; (4) catalyst carrier in petrochemical processes like Claus sulfur recovery and H₂O₂ production. Smaller applications include instrument air drying, desiccant in insulated windows, and specialty adsorption.
Q: What is the difference between activated alumina balls and powder?
A: Activated alumina balls (1-8mm diameter) are used in fixed-bed adsorption towers where gas or liquid passes through. Powder form (50-325 mesh) is used as raw material for catalyst preparation, polishing compounds, or as feedstock for further processing. Balls have better flow characteristics and lower pressure drop; powder has higher external surface area and faster adsorption kinetics.
Q: How is activated alumina regenerated?
A: For air/gas drying: heat to 180-250°C for 2-4 hours to drive off adsorbed water (TSA — Temperature Swing Adsorption). For water defluoridation: regenerate with dilute NaOH (1-2%) or Al₂(SO₄)₃ solution, followed by acid neutralization and water rinse. After 3-5 years of service, capacity declines significantly and replacement is recommended.
Q: What is the recommended particle size for air drying?
A: For compressed air dryers, 3-5mm or 5-8mm balls are most common — larger beads reduce pressure drop in tall towers. For instrument air and small dryers, 2-3mm or 4-6mm. For very deep drying (<-50°C dewpoint), smaller 1-2.5mm balls provide higher surface area but increase pressure drop. We can recommend optimal size based on your tower dimensions.
Q: Is activated alumina safe for drinking water treatment?
A: Yes. Activated alumina is NSF/ANSI 61 certified for drinking water treatment in the USA and approved under REACH in Europe. It effectively removes fluoride, arsenic, and selenium to below WHO guideline values. Standard grade uses Al₂O₃ ≥92%; high-purity grade uses ≥93%. Used in municipal water utilities across India, China, Africa, and rural USA.
Packaging & Delivery
- Standard: 25 kg kraft paper bags with PE inner liner (moisture-proof)
- Bulk: 500 kg / 1000 kg jumbo bags for full-container-load orders
- Sealed steel drums (200L) available for extreme moisture-sensitive applications
- Container loading: 20MT per 20'FCL with pallets, 24MT per 40'FCL bulk
- Lead time: 7-15 days for stock grades, 15-25 days for custom mesh or grade
- Documents: COA, MSDS, ISO 9001 certificate, REACH compliance, commercial invoice, packing list, B/L
- Shipping terms: FOB Qingdao / CIF / CFR / DDP available
How to Order
Tell us your application (air drying / water treatment / transformer / catalyst carrier), required Al₂O₃ grade (≥92% or ≥93%), particle size, monthly quantity, and delivery destination. Our engineers will recommend the right grade and provide a competitive quotation within 2 hours. Free 1-2 kg samples available for qualification testing.