1.1 General Description
PORESPHERE™ Aktiv-AL is an activated alumina desiccant used for the adsorption of moisture and acidic gases in industrial applications. The material is produced by thermal treatment of aluminum hydroxide and is supplied as robust, spherical granules with a high specific surface area.
Due to its thermal stability and mechanical strength, PORESPHERE™ Aktiv-AL is suitable for applications such as compressed air drying, gas treatment, and PSA systems for oxygen generation. Under moderate relative humidity conditions, it can adsorb up to 25 wt.% water. The material is suitable for operation at temperatures up to 300 °C and can be used in heat-regenerated drying systems.
1.2 Microstructure & Pore Structure
PORESPHERE™ Aktiv-AL is a granular adsorption material with a high surface area and a defined pore structure. The thermal conversion of aluminum hydroxide into activated alumina results in spherical granules with a network of fine pores that enable water adsorption.
The material is abrasion-resistant and withstands temperature and pressure variations in industrial systems. Water is adsorbed via physical interactions at the surface. Due to its basic surface chemistry, acidic gases such as HF, HCl, and SO₂ can also be adsorbed, making the material suitable for applications requiring both moisture and acid gas removal.
1.3 Adsorption Behavior
Water adsorption occurs through physisorption at hydroxyl groups on the surface. At high relative humidity (>60 % RH), adsorption performance increases due to capillary condensation within the pores.
At low humidity (<20 % RH), adsorption capacity is reduced. In the range of 20–60 % RH, adsorption occurs through a combination of surface adsorption and pore filling. The relatively large pores allow fast water uptake but lead to a faster approach to adsorption equilibrium compared to silica gel.
1.4 Regeneration
PORESPHERE™ Aktiv-AL can be regenerated by thermal treatment at 100–300 °C, removing the adsorbed water and restoring adsorption capacity. Regeneration is typically performed using hot air or inert gases such as nitrogen or argon.
• Hot air regeneration is used in continuous systems. • Inert gas regeneration is suitable for applications involving flammable or sensitive process streams.
The material is suitable for more than 1000 regeneration cycles. Alternatively, vacuum regeneration can be applied to enable desorption at lower temperatures.
1.5 Applications
• Compressed air drying: Removal of water vapor from compressed air systems to reduce corrosion and operational issues.
• Gas treatment: Removal of acidic gases such as HF, HCl, and SO₂ to protect downstream equipment.
• Catalyst support: Use as a support material in refinery and exhaust gas treatment processes due to its surface area and mechanical stability.
