3A, 4A and 5A: Understanding Type A Molecular Sieves
Type A molecular sieves are zeolite adsorbents used for drying and purification. The names 3A, 4A and 5A refer to approximate pore openings of 3, 4 and 5 angstroms. Choosing a grade starts with identifying what must be removed and which components should stay in the stream.
3A for selective water removal
The small pore opening of 3A makes it a useful candidate when water needs to be removed while larger molecules are excluded from the pores. Ethanol dehydration is a common example. For liquid or vapor service, identify the inlet water content, target water content and expected operating temperature before evaluating the available grades.
4A for general drying duties
The larger opening of 4A allows it to admit more molecules than 3A. It is widely used for drying gases and liquids when the feed composition and potential co-adsorption are acceptable. If the stream contains compounds that may compete for adsorption, include their expected concentrations in the grade discussion, especially when they vary between normal and peak operation.
5A PSA-H for hydrogen purification
The 5A family has a wider effective opening. In hydrogen PSA, a 5A grade can form part of a layered adsorbent bed selected to remove impurities from a hydrogen-rich feed. The appropriate bed arrangement depends on feed composition, inlet pressure and target hydrogen purity. Haina offers 5A PSA-H for this type of application.
Compare the grades
| Grade | Approximate pore opening | Typical application |
|---|---|---|
| 3A | 3 Å | Selective drying, including ethanol dehydration |
| 4A | 4 Å | General gas or liquid drying, depending on feed composition |
| 5A PSA-H | 5 Å | Impurity removal in a hydrogen PSA adsorbent bed |
Pore opening helps narrow the choice. Feed composition, temperature, pressure and regeneration strategy also matter. Specify the required outlet dew point or impurity limit, normal and peak flow, and duty cycle. When replacing media, share the original grade, particle size and bed configuration so the candidate can be assessed against the existing equipment.
Find the right grade for the duty
See Haina’s available grades or share your process requirements with the team.