WHAT IS MOLECULAR SIEVE?
The
Molecular Sieves are synthetic zeolites or metal alumino silicates, with a
porous tridimensional crystallized network. Molecular sieve have regular pore
sizes. Based on the pore size, they are called 3, 4, 5 or 10 A although the
real pore opening is somewhat inferior to these values.
By “
activation “ a highly active adsorbent is obtained. The activation aims to
desorb the zeolitic water contained in the adsorbent.
The
combination of a uniform porous structure with a high adsorption capacity,
enables the selective adsorption of the molecules.
“ Molecular
Sieves “, are so called because of their property of screening molecules at the
molecular scale. Molecular sieves differ from other adsorbents such as silica
gel or activated alumina, which have a very wide pore distribution.
A molecular
sieve is a material containing tiny pores of a precise and uniform size
that is used as anadsorbent for
gases and liquids.
Molecules small enough to pass through the pores are
adsorbed while larger molecules are not.
It isdifferent from a common filter in that it operates on a molecular level.
For instance, a water moleculemay be small enough to pass through while larger
molecules are not. Because of this, they oftenfunction as a desiccant. A
molecular sieve can adsorb water up to 22% of its own weight.
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, suchas 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 startingmaterials. The
mercury content of natural gas is
extremely harmful to the aluminum piping and otherparts 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.
The different
types of Molecular Sieves
1. 4 A is the basic
molecular sieve obtained by synthesis of type A zeolite.
2. 3 A is obtained
by replacing part of the sodium cations of the 4 A molecular sieve by potassium
cations.
3. 5 A is obtained
when potassium is replaced by calcium as the substitution cation.
4. 10 A ( type 13 x
or Siliporite G 5 ) is the basic molecular sieve obatained by synthesis of type
X Zeolite.
Adsorption
capabilities :
- · 3 A ( pore size 3 ångströms ) : adsorbs NH3, H20, , ( not C2H6 ), good for drying polar liquids.
- · 4 A ( pore size 4 ångströms ) : adsorbs H2O, CO2, H2S, C2H4, C2H6, C3H6, , EtOH. Will not adsorb C3H8, and higher hydrocarbons. Good for drying non polar liquids and gases.
- · 5 A ( pore size 5 ångströms ) : adsorbs normal ( linear ) hydrocarbons to n-C4H10, alcohol to C4H9OH, mercaptans to C4H9SH. Will not adsorb isocompounds or rings greater than C4.
- · 10 X ( pore size 8 ångströms ) : adsorbs branched hydrocarbons and aromatics. Useful for drying gases.
- · 13 X ( pore size 10 ångströms ) : adsorbs di-n-butylamine ( not tri-n-butylamine ). Useful for drying HMPA.
Next Topic : Bagaiman cara kerja Molsieve ?
For any further info and order please call me,
Michael Thang
Direct 02130338599, 085894436642 ( WA only )
michael@sanminglobe.com
Direct 02130338599, 085894436642 ( WA only )
michael@sanminglobe.com
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.