Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1988-08-17
1992-03-03
Breneman, R. Bruce
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
23295G, 156600, 156603, 156621, 156623R, C01B 3334
Patent
active
050930958
DESCRIPTION:
BRIEF SUMMARY
t at about 20.degree. to 400.degree. C. for 1 hour to about 90 days.
The composition of a more specific reaction mixture is:
The reaction and crystallization are carried out at a temperature from about 100.degree. C. to about 200.degree. C.
For a reaction mixture of 2.55Na.sub.2 O-5.0TPABr-100SiO.sub.2 -2800H.sub.2 O, the reaction and crystallization are carried out preferably at about 175.degree. to 185.degree. C. For high yields of small uniform crystals, a gravitational force of about 50 G and a reaction time of about 12 hours to about 60 hours is preferred. For large crystals, a force of about 50 G and a reaction time of about 84 hours to about 144 hours is preferred. For a reaction mixture of 2.78Na.sub.2 O-Al.sub.2 O.sub.3 -2.0SiO.sub.2 -504H.sub.2 O, the reaction and crystallization temperature is about 90.degree. C. with a reaction time greater than about 4 days in a force greater than about 10 G.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic partial cross-sectional elevational view of a centrifuge oven.
FIG. 2 is a schematic partial cross sectional plan view of the centrifuge oven.
FIG. 3 is a photomicrograph at 50 X of the crystals obtained in a 1 G gravitational force after 120 hours according to the method of Example 1.
FIG. 4 is a photomicrograph at 50 X of crystals obtained in a 30 G gravitational force after 120 hours according to the method of Example 1.
DETAILED DESCRIPTION OF THE INVENTION AND BEST MODE FOR CARRYING OUT THE
PREFERRED EMBODIMENT
The present invention relates to a new method for producing enhanced crystals of larger size, higher quality, greater yield, and more uniform size using a force greater than 1 G. The method has wide applicability in the crystallization art and may be used for crystal growth from solvent media, amorphous solids, and gels where a gel can be an aqueous solution, a reactive solid, a colloidal sol or a glass. Crystal growth may be proceeded by or concurrent with a chemical reaction. Crystal growth can be initiated by use of seed crystals, a crystal growth template, or by spontaneous nucleation. Crystal growth techniques known in the art are applicable to the crystal growth methodology of this invention, i.e., crystal growth in forces of greater than 1 G.
One area of application is the growth of zeolite-type crystals. Zeolitic crystals are ordered, porous crystalline materials having a definite crystal structure within which there are a number of still smaller channels. These cavities and channels are precisely uniform in size within a specific zeolitic material. And since the dimensions of the pores are such as to accept certain size molecules while rejecting those of larger dimensions, zeolitic materials are known as "molecular sieves" and are used in a variety of ways to take advantage of the adsorbent properties of these compositions. Large size crystals, that is, crystals greater in size than 200 microns, are particularly useful in adsorbent systems. When such large size crystals are used, the zeolitic bed does not pack and channel as quickly as when fine size materials are used and, as a result, the adsorptive properties of the zeolitic material are maintained. Examples of zeolite-type crystals are: Zeolites A, X, Y, ZSM-5, ZSM-11, ZSM-12, ZSM-35, aluminophosphates, metal incorporated alumino-phosphates, pillared inter-layered compounds such as pillared clays and zirconium phosphates, and zeolites in which Si is replaced in whole or in part by Al, Ga, Ge, Be, B, Fe, Cr, P, or Mg or combinations thereof.
One general method for the preparation and crystallization of zeolites may be represented generally in the following fashion: ##STR1##
Zeolites may be prepared from silica sources such as sodium silicate, colloidal silica, silica hydrosol, silica gel, and silicic acid. The silicon may be replaced by one or more elements such as aluminum, gallium, germanium, beryllium, boron, iron, chromium, phosphorus, or magnesium. The preparation of molecular sieves is well-known in the art and is described more fully in the Kirk-Othmer Encyclopedi
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Hayhurst David T.
Kim Wha J.
Melling Peter J.
Battelle (Memorial Institute)
Breneman R. Bruce
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