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Key Documents

334308

Sigma-Aldrich

Molecular sieves, 4 Å

pellets, 1.6 mm diameter

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About This Item

Linear Formula:
Na12[(AlO2)12(SiO2)12] · xH2O
CAS Number:
MDL number:
UNSPSC Code:
23201100
eCl@ss:
32110204
NACRES:
NB.24

form

pellets

Quality Level

diameter

1.6 mm

pore size

4 Å

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General description

Choosing a Molecular Sieve:
1. The preferential adsorption of one molecule over another depends upon pore diameter and mesh size.
2. The dynamic capacity of the silica gel for adsorbing a particular compound is governed by the internal surface area; the greater the surface area, the greater the dynamic capacity.
3. Rate of adsorption and sharpness of resolution are dependent chiefly on particle size and column packing; a fine particle size gives optimum sharpness of resolution.
4. Liquids are most readily adsorbed from solvents in which they are least soluble; a good solvent makes a good desorbing agent.
5. Highly polar liquids are readily adsorbed. Compounds having hydroxyl groups, or containing oxygen are strongly adsorbed.
6. For similar compounds, the higher the molecular weight the higher the selectivity.
7. For hydrocarbons of similar molecular weight, adsorptivity increases with the number of double bonds.
Regeneration or Activation:
A saturated molecular sieve can be restored to its original capacity by regeneration, the principle of which involves changing the conditions surrounding the adsorbent to correspond to a very low equilibrium capacity. In general, the greater the difference between the equilibrium capacities of adsorption and regeneration, the more rapid and complete the regeneration.
The sieve may be regenerated in one of four ways:
1. Thermal reactivation –The maximum regeneration temperature for Silica is 300°C.
2. Pressure reactivation
3. Passing an appropriate fluid through the gel bed at normal temperature and pressure.
4. Displacement of adsorbates by passing a high concentration of molecules in a fluid through the bed.

Storage Class

11 - Combustible Solids

wgk_germany

WGK 3

flash_point_f

Not applicable

flash_point_c

Not applicable


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