4A 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 | ≥ 22.5 | ≥ 22.5 | ≥ 22.5 | ≥ 22.5 | RH 75%, 25 °C |
| Bulk density | g/ml | ≥ 0.74 | ≥ 0.72 | ≥ 0.66 | ≥ 0.66 | Tapped |
| Crush strength | N | ≥ 40 | ≥ 80 | ≥ 40 | ≥ 80 | Avg. of 25 beads |
| Loss on attrition | % wt | ≤ 0.10 | ≤ 0.10 | ≤ 0.20 | ≤ 0.30 | — |
| Loss on ignition | % wt | ≤ 1.5 | ≤ 1.5 | ≤ 1.5 | ≤ 1.5 | 550 °C, 1 h |
| Particle size ratio | % | ≥ 97 | ≥ 99 | — | — | In stated size range |
Where is 4A Molecular Sieve used?
4A molecular sieve is the standard desiccant for drying natural gas, air, refrigerants and solvents, and for removing low levels of CO₂ and H₂S.
Natural gas dehydration
Dries gas below 0.1 ppmv water ahead of LNG and NGL units.
Compressed air drying
Reaches −70 °C pressure dew point in desiccant dryers.
Air brake dryers
Keeps truck and rail air-brake systems free of moisture.
Refrigerant & solvent drying
Removes water from refrigerants, solvents and liquid hydrocarbons.
4A Molecular Sieve vs other adsorbents: which do you need?
Choose 4A for general drying; switch to 3A when product molecules such as ethanol or olefins would co-adsorb, and to 13X when H₂O and CO₂ must be removed together at higher capacity.
| Grade | Pore | Adsorbs | Typical use |
|---|---|---|---|
| 3A | 3 Å | H₂O only | Ethanol, olefins, insulating glass |
| 4A (this product) | 4 Å | H₂O, CO₂, H₂S | Natural gas, air, refrigerant drying |
| 5A | 5 Å | n-paraffins, CO, CO₂ | PSA hydrogen, paraffin separation |
| 13X | ≈ 10 Å | H₂O + CO₂ together, mercaptans | Gas sweetening, purification |
What is 4A Molecular Sieve?
4A molecular sieve is a synthetic sodium A-type zeolite (NaA) with a uniform 4 Å pore opening that adsorbs molecules smaller than 4 Å, above all water.
Type
Sodium A-type zeolite
Adsorbs
H₂O, CO₂, H₂S, NH₃, C₂H₆
Excludes
Propane and larger hydrocarbons
How does 4A Molecular Sieve work?
Water and other small polar molecules enter the 4 Å pores and are held by the sodium cations, while larger molecules pass through the bed.
- Wet feed enters the bed — gas or liquid flows through packed 4A beads or pellets.
- Water is adsorbed in the pores — outlet moisture falls to ppm level.
- Dry product leaves the bed — the bed is switched to regeneration before water breaks through.
When should you use 4A Molecular Sieve?
Use 4A whenever you need deep drying of a gas or liquid whose main components are larger than 4 Å and no special selectivity is required.
- Target dew point is below what glycol or refrigerated dryers can reach.
- Feed is natural gas, air, refrigerant or a solvent.
- Small amounts of CO₂ or H₂S should come out with the water.
How do you regenerate 4A Molecular Sieve?
Regenerate 4A by heating the bed with dry purge gas, typically at 250–290 °C, then cooling it before it returns to service; in heatless dryers it is regenerated by pressure swing.
Temperature
250–290 °C
Purge gas
Dry product gas or N₂
Bed life
3–5 years
