What is molecular sieve
A molecular sieve is a material containing tiny pores of aprecise and uniform size that is used as an adsorbent for gases and liquids.
Molecules small enough to pass through thepores are adsorbed while larger molecules are not. It isdifferent from a common filter in that it operates on a molecularlevel and traps the adsorbed substance. For instance, a watermolecule may be small enough to pass through the pores while largermolecules are not, so water is forced into the pores which act as atrap for the penetrating water molecules which are retained withinthe pores. Because of this, they often function as a desiccant. A molecular sieve can adsorb waterup to 22% of its own weight.[1] Theprinciple of absorption to molecular sieve particles is somewhatsimilar to that of size exclusion chromatography except that without achanging solution composition the adsorbed product remains trappedbecause in the absence of other molecules able to penetrate thepore and fill the space, a vacuum would be created by desorption.
Often they consist of aluminosilicate minerals, clays, porous glasses, microporous charcoals, zeolites, active carbons, or synthetic compounds that have open structures through which small molecules, such as nitrogen and water can diffuse.
Molecular sieves are often utilized in the petroleum industry, especially for thepurification of gas streams and in the chemistry laboratory forseparating compounds and drying reaction starting materials. Themercury content of natural gas is extremelyharmful to the aluminium piping and other parts of the liquefactionapparatus - silica gel is used in this case.
Methods for regeneration of molecular sieves include pressurechange (as in oxygen concentrators), heating and purging with acarrier gas (as when used in ethanol dehydration), or heating under highvacuum.