Molecular sieve arrangement and filtering method for removal of

Details Molecular sieve arrangement and filtering method for removal of Molecular sieve arrangement and filtering method for removal of

1989-09-06

1992-09-22

Dawson, Robert A.

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

55 75, 55389, 55524, 210263, 210266, 2105021, 210504, 210506, 210507, 210509, 210679, 502 60, 502 62, 502 64, 502 69, 502 87, B01D 6100, B01D 3900

Patent

active

051494353

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a molecular sieve arrangement.
Natural and synthetic zeolitic molecular sieves are suitable for the separation of mixtures of inorganic and organic substances and for the removal of undesired impurities from gases and liquids. One current field of application of molecular sieves is the drying of gases and liquids, for example, acetone, butane, toluene, etc.
Molecular sieves are also used for the removal of carbon monoxide, hydrocarbons, nitrogen, methane and so on from air. They are further used in ion exchangers.
Molecular sieves within the scope of the invention can consist of natural or synthetic zeolites. Synthetic zeolites frequently have the same crystal structure as natural zeolites. Natural zeolites may, for example, be aluminum silicates having the general formula ##EQU1## where Me denotes the alkali metal ion (n=1), mostly Na or K, or the alkaline earth metal (n=2) which is normally Ca and more seldom Ba, Sr and Mg. Most of the ad/absorbents are included in this category.
The mechanics of separating molecules from liquid or gaseous media by means of molecular sieves involves adsorption with the molecular sieve functioning as an adsorbent and influencing the adsorption through the magnitude and energy characteristics of its surface. The adsorption of ions, molecules or molecular agglomerates and the like--the adsorbates--is limited by the energy characteristics of the boundary layer between the two phases. The adsorbed molecules continuously coat the inner surface of the adsorbent and cover the same. Accordingly, saturation occurs after a certain amount of time and prevents further adsorption.
The known separating processes use only molecular sieves having a pore size of 3 Angstroms or greater than 3 Angstroms in order to permit the entry of molecules to be filtered out of gases or liquids, that is, in order to make the vast inner surface of the molecular sieve usable.
The zeolites of the natural analcite group, whose pores have a size of the order of 2.6 Angstroms, have not been used as molecular sieves because the molecules to be adsorbed or absorbed cannot, due to their size, penetrate into the primary pores of the analcite zeolite. The smallest molecule, which is the water molecule, measures only about 2.9 Angstroms (see "MOLEKULARSIEBE" by Otto Grubner, Pavel Jiru and Milos Ralek, VEB Deutscher Verlag der Wissenschaften, Berlin 1968, page 27).
The disadvantageous property of the known molecular sieves is that the inner surfaces thereof are directly loaded and, depending upon molecular sieve type, no further molecules can be taken up once the adsorbate proportion has increased to about 25%.
Loading of the inner surfaces of the conventional molecular sieves already occurs upon contact with the surrounding air and the water molecules contained therein. Accordingly, the capacity is reduced in two respects.


SUMMARY OF THE INVENTION

The invention here provides a remedy.
The invention, solves the problem of creating a molecular sieves arrangement which can filter molecules or microscopic particles from gases or liquids and in which the inner surfaces of the molecular sieve can be coated neither by water molecules nor by the filtered molecules.
A molecular sieve which is incorporated in a carrier material and has a pore size smaller than 3 Angstroms (primary pores) allows the molecules or particles to be filtered to be brought into the pore and channel structure of the carrier material; the inner surfaces of the molecular sieve having pores smaller than 3 Angstroms remain largely free and retain their static charge (Coulombic attraction).
The pore and channel structure of the carrier material can have cross sections which are larger than the pores of the molecular sieve by a factor of up to 1000 and more. Correspondingly larger quantities of particles to be filtered can be accumulated in these relatively vast inner cavities before the static attraction of the adsorbent is no longer sufficient to draw additional charged particles into th

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