A Useful Guide About Molecular Sieves

Carbon molecular sieve
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molecular sieves

A material with pores of uniform or equal size is called a molecular sieve. The diameter of these pores is almost similar to small-sized molecules. Molecules having a diameter large, as compared to the diameter of pores, cannot enter or be absorbed. The mixture of distinct-sized molecules passes via the sieve or the matrix. This happens so that molecules with higher molecular weight will leave the base first. Activating molecular sieves will separate the molecules based on their sizes. This is known as chromatography.

Molecular sieves are highly effective to remove water from gases and they are even more efficient than desiccants due to their crystalline composition. These can create virtually water-free products. They are instrumental in cryogenic operations when gas needs to be liquefied or prevented from freezing.

The main applications of molecular sieves consist of:

  • Drying gas stream in the petroleum industry
  • Drying solvents in the laboratory
  • Various catalytic applications.

They are also used for liquid purification assemblies and air interaction while removing impurities from liquid or gas is easy as compared to any other system. They can be designed as per the size of impurity one wishes to filter. The most crucial aspects that make molecular sieves a vital solution are:

  • Ease of use
  • Super efficiency

Types of Molecular Sieves:

There are different types of molecular sieves:

  • 3A
  • 4A
  • 5A
  • 13X

Each type has a different pore size dependent on the chemical formula. The uses of these molecular sieves are:

  • Molecular sieves 3A: it is used for drying polar liquids.
  • Molecular sieves 4A: it is used for static drying of gases and liquids.
  • Molecular Sieves 5A: It is used to refine oil and gas products.
  • Molecular sieves 13X: it is mainly used to separate oxygen and nitrogen from the air.

Applications of Molecular Sieve:

Industry of Petroleum:

In the petroleum industry, molecular sieves are used widely. The major application of molecular sieves is in the drying gas stream assemblies. Take an example of the liquid natural gas (LNG) industry, the content of water of gas must be less than one ppm. If the water content is more, the chance of blockages in the stream increases. This happens because of the ice.


Molecular sieves are used to dry the solvents in laboratories. These sieves are the best to any traditional drying technique, which is mostly desiccant.

Catalytic Operations:

Molecular sieves or zeolites are used in various catalytic operations and they are also used to catalyze processes like:

  • Isomerization
  • Alkylation
  • Epoxidation

Molecular sieves are used in large-scale industrial processes like fluid catalytic cracking and hydrocracking.

Air and Water Filtration Assemblies:

Molecular sieves are used in air and water supplies in the filtration apparatus. Let’s take an example of underwater masks used by drivers. In this kind of application, the air is supplied by an air compressor. Depending on the application, it is filled with activated carbon, molecular sieves, or both. These filters remove particulates and the compressor exhausts the products from the breathing air supply.

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