Different Types of Molecular Sieves and Their Uses
A widely-used industrial absorbent, molecular sieves are synthetic metal aluminosilicates that are comprised of a 3D interconnected alumina tetrahedra and silica network with pores of a uniform size and structure.
Molecular sieves come in different types for absorbing liquids and gases of varying polarity and molecular size. Over the course of this blog post, we’ll discuss the different types of molecular sieves and their industrial applications.
The Main Types of Molecular Sieves
While molecular sieves come in a multitude of varieties, we’ll discuss the three most commonly-used types: 5A, 4A, and 3A. The type is determined by the size of the diameter of the pores on the molecular sieves. Since they work at a molecular level, angstroms is the unit of measurement used for measuring the size of the sieves. For instance, 3Å molecular sieves come into contact with a substance, only the molecules that have a size equal to or smaller than 3Å will get absorbed.
Here’s are the four types of molecular sieves and applications.
3Å Molecular Sieves
3Å molecular sieves have a bulk density in the range of 0.60-0.68 g/ml. They’re mainly used in the petroleum industry for desiccating alkenes and purifying petroleum gas, as well as for selective H2O absorption in polyurethane and insulated glass.
4Å Molecular Sieves
Having a bulk density of 0.60 to 0.65 g/ml, 4A molecular sieves are used for the following industrial applications:
- Used by pharmaceutical companies in medical containers to protect the contents from moisture contamination.
- Used by food manufacturers as an additive (anti-caking agent)
- Used for static dehydration for closed gas or liquid systems, i.e. in drug packaging.
- Used for scavenging water in plastics and printing systems.
- Used for drying saturated hydrocarbon streams.
5Å Molecular Sieves
Like their 4A counterparts, 5Å molecular sieves have a bulk-density in the range of 0.60 to 0.65 g/ml as well. These are most comply used for:
- Purification and desiccation of air
- Desulfurization and dehydration of LPG (liquefied petroleum gas) and natural gas.
- Hydrogen and oxygen production through the PSA (pressure swing absorption) process.
- Used in oil refineries for separating hydrocarbons and alkenes.
- Used for adsorbing water in non-nitrogen sensitive polyurethane.
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