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 adsorbed 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 not be small enough to pass through while the smaller molecules in the gas pass through. Because of this, they often function as a desiccant. A molecular sieve can adsorb water up to 22% of its own weight.[1]
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 the purification of gas streams and in the chemistry laboratory for separating compounds and drying reaction starting materials. 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 pressure change (as in oxygen concentrators), heating and purging with a carrier gas (as when used in ethanol dehydration), or heating under high vacuum.
Contents
Types of Molecular Sieve :
* 3A (pore size 3 Å): Adsorbs NH3, H2O, (not C2H6), good for drying polar liquids.
* 4A (pore size 4 Å): Adsorbs H2O, CO2, SO2, H2S, C2H4, C2H6, C3H6, EtOH. Will not adsorb C3H8 and higher hydrocarbons. Good for drying nonpolar liquids and gases.
* 5A (pore size 5 Å): Adsorbs normal (linear) hydrocarbons to n-C4H10, alcohols to C4H9OH, mercaptans to C4H9SH. Will not adsorb isocompounds or rings greater than C4.
* 10X (pore size 8 Å): Adsorbs branched hydrocarbons and aromatics. Useful for drying gases.
* 13X (pore size 10 Å): Adsorbs di-n-butylamine (not tri-n-butylamine). Useful for drying HMPA.
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3 comments:
kira-kira harga yang 3A berapa ya??
The purification zeolite or molecular sieve is often utilized in the petroleum industry, especially for the purification of gas streams and in the chemistry laboratory for separating compounds and drying reaction starting materials. For example, in the LNG industry, the water content of the gas needs to be reduced to very low values (less than 1ppmv)to prevent it from freezing (and causing blockages) in the cold section of LNG plants.
Molecular filter is a content containing small pores of a accurate and consistent size that is used as an adsorbent for gases and fluids. Internally, the structure has many oral cavaties inter-connected by small pores of a consistent dimension. These pores are only able to accept and pass to the cavaties molecules of the same and small dimension, hence the name molecular filter.For instance, a water molcule 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.
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