Air Purification

Natural zeolites are an adsorbent of choice for many cost effective air pollution control technologies treating the hazardous air pollutants (HAP) and listed volatile organic compounds (VOC).

The need for technologically improved air purification systems has been indicated by keen client interest in the use of zeolites in controlling indoor air pollutants or "sick building syndrome". Existing filtration systems typically contain activated carbon as the adsorbent media. Because most grades of activated carbon contain large internal pores, they tend to trap a wide variety of larger molecules.

Zeolites, on the other hand, contain very small internal pores, in all cases from 3 to 5 angstroms. For this reason zeolite is a highly selective adsorbent of specific gas-phase molecules and elements. Many of the identified indoor air pollutants, including formaldehyde, chloroform, ammonia and carbon monoxide, are in a size range that is most effectively sieved by zeolite. Many promising zeolite and zeolite/carbon air purification and odor controlling systems are being developed to meet the need. Beneficial qualities include selectivity for pollutant gases of concernInexpensive relative to other molecular sieves

Gas Separation

The properties of gas adsorption and molecular sieve are essential in utilizing the zeolites.They can remove volatile organic chemicals from air streams, separate isomers and mixtures of gases. The porous structure of zeolites can be used to "sieve" molecules having certain dimensions and allow them to enter the pores. This property can be fine tuned with variation of the structure by changing the size and number of cations around the pores. Adsorption of argon was investigated on some zeolites, especially on ion-exchanged forms of clinoptilolite.Clinoptilolite adsorbs sulfur dioxide and argon gases. The adsorption capacities for argon of Na-, K- and Ca-forms are compared with those of nitrogen.The relatively high capacity of the Na-form can be evidenced.

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Desiccants/Flow agents

ZeoStore™ Zeolite has low density and a large void capacity. Also, when dehydrated, zeolite maintains stability of its crystal structure. Due to its high cation exchange capacity, it absorbs gases, vapors and liquids as well as holding up to 70% of its weight in water.

This results in superior capability in preventing product caking and it is used as a natural preservative for many agricultural and chemical products. It has also been used as a desiccant for drying natural gas, carbon dioxide, Freon gas, and organic chemical streams such as transformer oil and xylene. Zeolites have the potential of providing precise and specific separation of gases including the removal of H2O, CO2 and SO2 from low-grade natural gas streams. Other separations include: noble gases, N2, O2, Freon and formaldehyde.

Catalysts and Petroleum Refining

Zeolites are extremely useful as catalysts for several important reactions involving organic molecules. The most important are cracking, isomerization and hydrocarbon synthesis. Zeolites can promote a diverse range of catalytic reactions including acid-base and metal induced reactions. They can also be acid catalysts and can be used as supports for active metals or reagents.

Zeolites can be shape-selective catalysts either by transition state selectivity or by exclusion of competing reactants on the basis of molecular diameter. They have also been used as oxidation catalysts. The reactions can take place within the pores of the zeolite, which allows a greater degree of product control.

The main industrial applications include the following:

• Petroleum refining
  
• Water and carbon dioxide removal from gaseous hydrocarbons
  
• Hydrochloric acid removal from gas streams
  
• Hydrogen or chlorine drying assistance
  
• Chlorinated and fluorinated hydrocarbon purification
  
• Catalysis and natural gas separation.
  
• Petrochemical production
  

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