Molecular sieve applications

THINGS TO KNOW WHEN PURCHASING MOLECULAR SIEVES.!

Molecular sieves are used commercially to purify gas streams and as desiccants to remove water or reduce humidity.

This article focuses chiefly on what you need to know when buying a desiccant dryer, although the basic principles may apply to other applications as well.

How a Molecular Sieve Works The material used in an industrial molecular sieve has small uniform pores. When other substances come in contact with the molecular sieve, the molecules that are the right size to fit in the pores will be adsorbed. The molecules that are too large to fit will not. Molecular sieves function at the microscopic level, therefore their sizes are measured in angstroms. Pore sizes 3Ă… and 4Ă… will adsorb water while larges sizes remove larger hydrocarbons.

Molecular Sieve Materials In a strictly scientific sense, many natural desiccant dehumidifiers like lime, clay and silica gel also work by sieving molecules of water vapor, but commercial molecular sieves are made of synthetic crystalline aluminosilicates.

Unlike desiccants found in nature, the control of pore size during manufacture produces selective adsorption characteristics.

The Advantages of Molecular Sieves Molecular sieves typically adsorb water much faster than other desiccant air dryers and they can reduce the humidity to much lower levels that the standard silica gel. They are also more effective than natural desiccants for applications that exceed normal room temperature. When properly used, they can be effective in reducing water molecules as low as 1ppm in specialized containers or to 10% relative humidity in packaging.

Regeneration and Reuse of Molecular Sieves While some molecular sieves that remove alcohols and aromatic hydrocarbons use pressure to regenerate the sieve, the molecular sieves that are used for water-adsorption are usually regenerated by heating. For most industrial purposes, these temperatures range from about 250° to 450°F, similar to baking temperature settings for a standard kitchen oven.

Disadvantages of Molecular Sieves Prices are higher than other forms of desiccant dehumidification; however, molecular sieves are also more efficient. The actual costs per unit and final value will depend upon other factors such as the volume to be dehumidified and level of dryness needed. Molecular sieves, while approved for use with pharmaceuticals in Europe, have not been approved by the FDA for either foodstuffs or pharmaceuticals in the US. Molecular sieves have excellent capacity for and rates of adsorption, even at elevated temperatures. They are the only desiccant that is selective for molecular size.

Applications of Molecular Sieves Packaging + Storage Molecular sieves physically adsorb water molecules, reducing water concentration levels to less than 1 ppm in many applications.

MOLSIV adsorbents are incorporated directly into plastics packaging and used in desiccant dehumidifiers (dry boxes) to protect moisture-sensitive contents.

Packaging: Molecular sieves are added to protect products such as pharmaceuticals, batteries, film, fuel propellants, machine parts and electronic components.

The selective adsorption characteristics of molecular sieves can be useful when it is necessary to dry a package without removing other desirable compounds from a system. Storage: Molecular sieve are used in cabinets and enclosures as desiccants to trap airborne moisture.

Common applications include the prevention and protection against oxidation (rust), growth of fungus on optics, the preservation

Air Drying Compressed air is dried for use with plastics processing, air brakes, sterile environments, sensitive instruments, packaging and other critical process operations.

UOP’s MOLSIV adsorbents play an essential role in these processes because of their high dew point depression and dynamic drying capacity. High strength and attrition resistant characteristics guarantee thousands of cycles under extreme conditions over a long lifetime.

Plastic Resin Drying Molecular sieves are used in desiccant dryers to dry hygroscopic plastic resins for applications such as PET preform molding, highvolume extrusion of sheet and film, or large part injection molding.

Because of their high affinity for moisture at very low dewpoints, molecular sieve desiccant dried air can produce dewpoints of -40°F and lower.

Instrument Air Drying • Molecular sieves are used in desiccant dryers to produce instrument grade air from compressor air.

Brake Air • Molecular sieves are used in heavy and medium-duty truck, bus, and train air brakes as selfrenewing dehydrators. Dehydrating the compressed air keeps the brake lines from freezing and corroding.

Specialty Air Applications Molecular sieves are used to dry air for use in pharmaceutical, electronic and food packaging applications

Industrial Gas Purification + Air Separation High purity industrial gases such as O2, N2, H2 and CO are produced in a variety of ways. UOP’s MOLSIV adsorbents play an essential role in these processes because of their high adsorption selectivity and capacity. In addition, UOP’s aluminas are often used for dehydration applications

• H2& CO Production: Molecular sieves remove water and CO2 to prevent freezing in downstream cryogenic separation processes • O2& N2 Production: Molecular sieves remove water and CO2 from compressed air to prevent freezing in downstream cryogenic separation processes.

• H2 Production: Molecular sieves remove impurities such as hydrocarbons, CO and N2 from gas phase H2 production.

Dehydration: Spherical activated aluminas are used for dehydration systems as in pressure swing adsorption systems.

MOLECULAR SIEVE CHARACTERISTICS

Reference Links • • • • • • • • • • • • • • • • • • • •

1.http://molecularsievedesiccants.com/ 2.http://molecularsievedesiccants.com/molecularsieve/3.http://molecularsievedesiccants.com/molecular-sieve-3a/ 4.http://molecularsievedesiccants.com/molecular-sieve-4a/ 5.http://molecularsievedesiccants.com/molecular-sieve-5a/ 6.http://molecularsievedesiccants.com/molecular-sieve-13x/ 7.http://molecularsievedesiccants.com/molecular-sieve-beads/ 8.http://molecularsievedesiccants.com/molecular-sieve-pellets/ 9.http://molecularsievedesiccants.com/molecular-sieve-for-ethanol-dehydration/ 10.http://molecularsievedesiccants.com/molecular-sieve-for-natural-gas-drying/ 11.http://molecularsievedesiccants.com/molecular-sieve-for-natural-gas-separation/ 12.http://molecularsievedesiccants.com/molecular-sieve-for-mercaptan-removal/ 13.http://molecularsievedesiccants.com/molecular-sieve-for-oxygen-purification/ 14.http://molecularsievedesiccants.com/molecular-sieve-for-hydrogen-purification/ 15.http://molecularsievedesiccants.com/molecular-sieve-powder/ 16.http://molecularsievedesiccants.com/molecular-sieve-13x/ 17.http://molecularsievedesiccants.com/molecular-sieve-5a/ 18.http://molecularsievedesiccants.com/molecular-sieve-beads/ 19.http://molecularsievedesiccants.com/molecular-sieve-for-ethanol-dehydration/ 20.http://molecularsievedesiccants.com/molecular-sieve-for-solvent-drying/ 21.http://molecularsievedesiccants.com/molecular-sieve-powder/"

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