Activated Alumina Adsorbents

Activated alumina is a hard, highly porous form of aluminum oxide (Al2O3 · nH2O), produced by heating aluminum hydroxide under controlled conditions so that water leaves the crystal and a network of fine pores is left behind. The finished spheres carry a very large internal surface area, and the hydroxyl groups on that surface have a strong affinity for water and other polar molecules, so the material draws moisture and polar contaminants out of air, gas, and liquid streams by physical adsorption. The same surface chemistry lets alumina take up acid gases, which is why this family includes a chloride adsorbent alongside the desiccant grades. Interra Global supplies activated alumina in bulk under the aSORB® product line and in the BASF-manufactured F200 grade.

Activated alumina is typically the desiccant of choice where the bed sees hard cycling, liquid water, or acid-bearing streams, and where the required outlet dew point does not call for molecular sieve. It tolerates contact with liquid water that would fracture silica gel, holds its crush strength through repeated thermal and pressure cycling, and generates little dust, which is why it is the standard desiccant in heat-regenerated and heatless compressed air dryers and a common choice for gas and liquid drying beds. Its water capacity at ambient temperature and high humidity is typically lower than silica gel's per pound, and its dryness limit sits above molecular sieve's, so deep drying and dew point critical service typically go to sieve, sometimes downstream of an alumina bed that removes the bulk water first.

GRADES AND WHAT THEY ARE FOR

aSORB Activated Alumina.

The house desiccant grade: smooth, high-crush-strength spheres for compressed air, gas, and process-stream drying in heat-regenerated and heatless dryers, and the grade Interra Global typically recommends when a specification is written to performance rather than to a manufacturer's product name. Properties and documents are on the product page; sphere size, packaging, and lead time are confirmed at quote.

BASF F200 Activated Alumina.

The BASF-manufactured desiccant sphere, supplied for buyers whose specifications call for F200 by name, in 1/8, 3/16, and 1/4 inch nominal sizes. BASF rates F200 for certain acid-containing gases and liquids, including carbon dioxide-containing streams, and as resistant to amine attack. Where a requirement is performance-based rather than restricted to the BASF product, aSORB is the alternative, evaluated against particle size, physical properties, operating conditions, equipment design, and qualification requirements.

aSORB DCL Promoted Chloride Adsorbent.

Activated alumina carrying a surface promoter that raises its capacity for hydrogen chloride and holds the chloride once adsorbed. It serves as a chloride guard on raw materials and process streams in propane dehydrogenation and catalytic reforming units, where HCl leaving chlorided catalysts would otherwise corrode downstream equipment and poison downstream catalysts, and it works across a wide operating temperature range.

WHERE ACTIVATED ALUMINA FITS AMONG INTERRA GLOBAL'S DESICCANTS

Interra Global supplies three regenerable desiccant families, and the choice typically follows the service conditions. Silica gel takes the largest moisture load at ambient temperature and moderate to high humidity and is the usual choice for static protection, packaging, and dryers operating near ambient conditions, but standard grades should not see liquid water. Activated alumina takes the wet and hard-cycling duty: it tolerates liquid water and repeated regeneration, its crush strength and low attrition suit tall beds and pneumatic loading, and in compressed air service it typically reaches dew points of -40°F and, with suitable dryer design, as low as -100°F. Molecular sieve holds its capacity at low humidity and elevated temperature and reaches far lower outlet moisture, so it takes deep drying and dew point critical service. Many dryer designs pair the materials, with gel or alumina taking the bulk water ahead of a sieve polishing layer.

Regeneration follows the same ladder. Silica gel regenerates at the lowest temperatures, activated alumina in a middle range, and molecular sieve highest. In heatless compressed air dryers, alumina is regenerated without heat at all, by a depressurized purge of dry product air, which is the duty where its cycling durability matters most.

TYPICAL APPLICATIONS

• Compressed air drying, in heat-regenerated and heatless dryers
• Gas dehydration and liquid drying, including hydrocarbon and solvent streams, in thermally regenerated and pressure swing beds
• Chloride removal from process streams in propane dehydrogenation and catalytic reforming units
• Acid and moisture control in refrigeration systems, where alumina takes up acids alongside a molecular sieve desiccant

SELECTING A GRADE

Selection typically starts with three questions: what the bed is asked to do (drying or chloride removal), whether a drying specification is written to performance or to a manufacturer's product name, and what sphere or mesh size the bed and the fluid phase call for, since liquid and mass-transfer-limited service typically favors smaller spheres while pressure drop favors larger ones. From there, bed design, regeneration method, and packaging narrow the choice, and each product page below carries the properties and documents for its grade. When the right grade is not obvious, Interra Global's technical staff review the service conditions and recommend a fit when called on. Every grade is supplied in bulk, from bag lots to full container loads, and unlisted sizes or grades are quoted on request.

FREQUENTLY ASKED QUESTIONS

What is activated alumina?

Activated alumina is a porous, high-surface-area form of aluminum oxide (Al2O3 · nH2O) used as a desiccant, an adsorbent, and a catalyst carrier. It is made by heating aluminum hydroxide under controlled conditions so that water leaves the crystal structure and a fine pore network forms; the result is a transitional alumina rather than the dense, chemically inert alpha alumina (corundum) used for abrasives and ceramics. Its internal surface has a strong affinity for water and other polar molecules, and it can be regenerated by heating and reused.

Is activated alumina the same as the alumina balls used for bed support?

No. Both are aluminum oxide, but inert alumina bed support balls are fired dense so that they adsorb as little as possible and simply carry the load, while activated alumina is made porous so that it adsorbs as much as possible. The two sit at opposite ends of the same bed: support balls beneath, activated alumina above. Interra Global supplies both; the inert bed support media page carries the support balls.

Can activated alumina get wet?

Activated alumina tolerates contact with liquid water far better than silica gel, which is one reason it is specified where condensate, carryover, or upsets can reach the bed. Wetting still costs capacity until the bed is regenerated, and a flooded bed is not drying anything, so dryer designs keep bulk liquid out of the vessel where they can.

How is activated alumina regenerated?

By driving off the adsorbed water. In heat-regenerated dryers a hot dry gas passes through the bed, and in heatless dryers a fraction of the dried product air is depressurized and purged back through the offline bed at near-ambient temperature. Each grade's product data sheet is the reference for regeneration limits, and overheating shortens service life.

What is promoted alumina, and what does a chloride guard bed do?

Promoted alumina is activated alumina treated with a promoter, typically an alkali component, that raises its capacity for hydrogen chloride and holds the chloride so it is not released downstream. A chloride guard bed sits ahead of the equipment and catalysts that HCl would corrode or poison, in units such as catalytic reformers and propane dehydrogenation plants where chloride leaves the catalyst with the process stream. aSORB DCL is the grade in this family.

When should I use activated alumina instead of silica gel or molecular sieve?

As a rule of thumb: silica gel for the largest moisture loads at ambient temperature and moderate to high humidity, activated alumina where liquid water, hard cycling, heatless regeneration, or acid-bearing streams are involved, and molecular sieve where the outlet has to be very dry. Many dryers pair the materials, with gel or alumina taking the bulk water ahead of a sieve polishing layer. The silica gel and molecular sieve family pages carry the same comparison from their sides.

Is activated alumina hazardous?

Plain activated alumina is chemically inert and non-hazardous under normal handling; the fine dust raised at loading should not be inhaled, and the safety data sheet for each grade governs. Spent material takes on whatever it adsorbed, so spent chloride adsorbent is handled and disposed of according to the process stream rather than the fresh product's sheet.