Microporous substance made of clay-like materials (such as crystalline alumino-silicates belonging to the zeolite class) which can be completely dried out without affecting their crystal structure
. They form millions
of regularly spaced pores (also called cages, cavities, or channels) with precisely the same diameter within a particular material
but varying among different materials generally between 3 to 10 Angstorm (Å) units. Like the pores of activated carbon
, these pores serve as a screen
(sieve) by allowing only the molecules of a certain diameter to be absorbed or pass through. Molecular sieves are used in drying and deodorizing, in cracking of petroleum
, and in filtering
water and other liquids and gases.
In some applications, they are loaded with chemicals that do not participate in a reaction
until forced out from the sieve by high temperature
or more readily absorbed substances.