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| A molecular sieve is a material containing tiny pores of a precise
and uniform size that is used as an adsorbent for gases and liquids.
Molecules small enough to pass through the pores are absorbed while larger molecules are not. It is different from a common filter in that it operates on a molecular level. For instance, a water molecule may be small enough to pass through while larger molecules are not. Because of this, they often function as a desiccant. Molecular sieve can absorb water up to 22% of its own weight. Often they consist of aluminosilicate minerals or synthetic compounds that have open structures through which small molecules can diffuse, such as clays, porous glasses, microporous charcoals, active carbons etc... Molecular sieves are usually utilized in the petroleum industry, especially with purification of gas streams. The mercury content of natural gas is extremely harmful to the aluminum piping and other parts of the liquefaction apparatus - silica gel is used in this case. Methods for Regeneration of molecular sieves include by pressure change as in oxygen concentrators or by heating and purging with a carrier gas as when used in ethanol dehydration. Molecular sieves types:
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