3A Molecular Sieve specifications
| Property | Unit | Bead Ø1.6–2.5 mm | Bead Ø3.0–5.0 mm | Pellet 1/16" | Pellet 1/8" | Test condition |
|---|---|---|---|---|---|---|
| Static water adsorption | % wt | ≥ 21.5 | ≥ 21.5 | ≥ 21.5 | ≥ 21.5 | RH 75%, 25 °C |
| Bulk density | g/ml | ≥ 0.75 | ≥ 0.75 | ≥ 0.70 | ≥ 0.70 | Tapped |
| Crush strength | N | ≥ 35 | ≥ 100 | ≥ 40 | ≥ 90 | Average of 25 beads |
| Loss on attrition | % wt | ≤ 0.10 | ≤ 0.10 | ≤ 0.20 | ≤ 0.20 | — |
| Loss on ignition | % wt | ≤ 1.5 | ≤ 1.5 | ≤ 1.5 | ≤ 1.5 | 550 °C, 1 h |
| Particle size ratio | % | ≥ 98 | ≥ 98 | ≥ 98 | ≥ 98 | In stated size range |
Where is 3A Molecular Sieve used?
3A molecular sieve is used wherever water must be removed without adsorbing the main product: ethanol, cracked gas and olefins, insulating glass and refrigerants.
Cracked gas & olefins
Recommended: Bead 3.0–5.0 mm / Pellet 1/8″
Drying ethylene, propylene and butadiene without polymerisation.
Refrigerant drying
Recommended: Bead 1.6–2.5 mm / Pellet 1/16″
Filter-drier cores for refrigeration circuits.
3A Molecular Sieve vs other grades: which do you need?
Choose 3A when co-adsorption of your product must be avoided; choose 4A for general drying where only H₂O and CO₂ matter, 5A or 13X when you need larger molecules removed as well.
| Grade | Pore | Adsorbs | Typical use |
|---|---|---|---|
| 3A (this product) | 3 Å | H₂O, NH₃ | Ethanol, olefins, insulating glass |
| 4A | 4 Å | H₂O, CO₂, H₂S, C₂H₆ | Natural gas, air, refrigerant drying |
| 5A | 5 Å | n-paraffins, CO₂ | PSA hydrogen, n/iso-paraffin separation |
| 13X | ≈ 10 Å | H₂O + CO₂ together, mercaptans | Air pre-purification, gas sweetening |
What is 3A Molecular Sieve?
3A molecular sieve is a synthetic potassium A-type zeolite (KA) whose 3 Å pores let water in and keep almost every other molecule out. It is made by exchanging part of the sodium in 4A zeolite for potassium, which narrows the pore opening from 4 Å to about 3 Å.
Chemical type
Potassium A-type zeolite
≈ 0.6K₂O · 0.4Na₂O · Al₂O₃ · 2SiO₂
Adsorbs
H₂O, NH₃
Molecules smaller than 3 Å
Excludes
Ethanol, C₂H₄, C₃H₆, CO₂
Larger molecules pass through
How does 3A Molecular Sieve work?
3A molecular sieve works by size exclusion: a water molecule (≈ 2.8 Å) fits through the 3 Å pore and is held on the crystal surface, while ethanol (≈ 4.4 Å) and olefins are physically too large to enter.
- Wet stream enters the bed — gas or liquid flows through a packed column of 3A beads.
- Water is trapped in the pores — polar H₂O is adsorbed strongly; outlet moisture drops to below the target dew point.
- Product passes through untouched — no co-adsorption, so no product loss and no coke-forming polymerisation.
How is 3A Molecular Sieve manufactured?
We make 3A molecular sieve in six steps in our own plant, from 4A zeolite powder to sealed drums, and test every lot before it ships.
01Synthesis
Na-A (4A) zeolite crystallised from sodium silicate and aluminate.
02Potassium exchange
Na⁺ replaced with K⁺ — this sets the 3 Å pore.
03Forming
Blended with clay binder, rolled into beads or extruded into pellets.
04Activation
Dried and calcined in a rotary kiln at high temperature.
05Screening
Sieved to size range; fines and broken beads removed.
06Test & pack
Adsorption, crush strength and moisture tested; sealed hot.
When should you use 3A Molecular Sieve?
Use 3A molecular sieve whenever you must remove water from a stream whose main molecules are small or reactive enough that a 4A sieve would also adsorb them.
Ethanol dehydration
PSA drying of fuel ethanol to ≥ 99.5% — ethanol stays out of the pores.
Cracked gas & olefins
Drying ethylene, propylene and butadiene without polymerisation in the bed.
Insulating glass
Desiccant in spacer bars; takes up water, not the argon or air fill.
Polar liquids & refrigerants
Drying methanol and refrigerant circuits in filter-driers.
How do you regenerate 3A Molecular Sieve?
Regenerate 3A molecular sieve by heating the bed with a dry purge gas until the outlet dew point recovers; in PSA ethanol units it is regenerated by pressure swing instead.
Temperature
200–300 °C
Purge gas
Dry N₂ / product gas
Bed life
3–5 years
