With the appearance of small opaque pinkish beads, molecular sieves are synthetically produced, highly porous, crystalline metal-alumino silicates. They have many internal cavities that are linked by window openings of precise diameters. It is these diameters (measured in Ångstroms) that classify molecular sieves – 3A, 4A, 5A, and 10A (also known as 13X). Absorption occurs of molecules with smaller diameters than the cavity openings – larger molecules being excluded. This makes molecular sieves ideal for absorption of water from air and liquids, as water molecules are both polar and very small.
Molecular sieves are utilised in the petroleum industry especially for the purification of gas streams, and in the laboratory for separating compounds and drying reaction starting materials.
Molecular sieves differ from silica gel in a number of ways:
- They absorb water vapour more rapidly than silica gel.
- They reduce water vapour to much lower levels than silica gel being ideal for when a very dry product or atmosphere is required.
- They perform more effectively as moisture absorbers at higher temperatures (greater than 25°C).
We supply the following molecular sieve products: 3A, 4A, 5A, and 13X.