Chemistry of inorganic compounds – Zeolite – With change of synthesized zeolite morphology
Reexamination Certificate
2000-12-14
2004-02-03
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
With change of synthesized zeolite morphology
C423S712000, C423SDIG002, C423SDIG002
Reexamination Certificate
active
06685910
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to novel aluminosilicate zeolite structures useful as water softening materials. The unique zeolite materials of this invention can be used to form both regenerable as well as disposable static water softening devices.
BACKGROUND OF THE INVENTION
Water softening is a process of water treatment by which undesirable cations, in particular, calcium and magnesium, are removed. Water, which contains such cations, is considered hard, wherein hardness is usually expressed as calcium carbonate equivalents in parts per million. The presence of these cations in water is undesirable for household purposes, such as for bathing, cleaning, and laundry, as well as for industrial purposes, such as boiler feed, food processing and chemical processing, because of reactions which form soap scum, boiler scale, and unwanted byproducts. Hard waters have been softened by precipitation processes which involved the use of hydrated lime or cation-exchange processes which involved the use of sodium-cation exchangers such as aluminosilicate zeolites or hydrogen cation-exchangers such as in the form of resins in bead form.
Water softening with ion exchange material such as resin particles or the like is well-known in the art. During the softening process, or service cycle, the ion exchange resin particles acquire hardness inducing ions (Ca
2+
, M
g
2+
) from the water in exchange for soft ions, (H+, Na+, K+) which do not induce hardness. After prolonged contact of the resin particles with raw water, the ion exchange capacity of the resin is diminished considerably and periodic regeneration of the resin particles must be accomplished, conventionally by contacting the resin particles with a brine solution, i.e., an aqueous solution of sodium chloride or potassium chloride or the like.
The ion exchange process and the regeneration of the ion exchange material are accomplished in a softener or resin tank of well-known construction, while a separate brine tank is conventionally employed to manufacture brine for use during the regeneration cycle. When is initiated in the system, brine is drawn from the brine tank and passed through the bed of ion exchange material in the softener tank to reverse the exchange of ions and revitalize the bed by removing hardness inducing ions and replacing them with sodium ions, for example, from the brine solution.
In general, there has been a progression in the use of ion exchangers for water softening from initial uses of alumina-silica gels to specific aluminosilicate zeolite materials such as zeolite A to the prevalent use of ion exchange resins at the present time. Among the reasons for this progression is that the alumina-silica gels, although being rather inexpensive, were simply not adequate sequestering agents, having neither a rapid rate of sequestration, capacity or selectivity for the hardness ions to be universally effective water softening agents. Zeolite A eventually replaced the alumina-silica gels inasmuch as this particular zeolite had a fast sequestration rate and high capacity for the hardness ions. Zeolite A was a very effective water softening agent, in particular, for use in regenerable static beds which were regenerated by the addition of brine to the bed which displaced the hardness cations of calcium and magnesium with sodium which allowed the zeolite A bed to be reused. Unfortunately, there was found that with extended use of zeolite A, water turbidity became a problem due to the relatively low attrition resistance of the zeolite granules which broke down into minute particles. These minute particles eventually entered into the water stream. Accordingly, although zeolite A was the standard for fixed bed water softening applications for more than a decade, zeolite A has essentially been displaced by the more expensive organic ion exchange resins. The expense and relatively low capacity of these organic resin materials, however, has prompted a need for finding less expensive and improved hardness ion sequestrants so as to expand the use and market of water softening agents.
In commonly assigned U.S. Pat. No. 5,948,383, the present inventors disclosed the formation of hybrid zeolite-silicate compositions (HZSC) which demonstrate unusual and beneficial properties in complexing multivalent cations. These hybrid materials are prepared by crystallizing high aluminum zeolites from highly alkaline/high silica environments. Chemical analysis indicates that an excess of silica is present in these compositions beyond that inherent in the crystalline frameworks thereof. These hybrid materials demonstrate sequestration capacities for cations such as calcium which not only exceed the amount of zeolitic aluminum available for ion exchange, but, in fact, may exceed the theoretical limit possible for zeolite. While the hybrid zeolite-silicate compositions as disclosed in U.S. Pat. No. 5,948,383 are described as being preferably useful in detergent compositions, the patent also sets forth in very general terms that these hybrid compositions show extreme promise as water softening agents. U.S. Pat. No. 5,948,383 does not otherwise disclose the form that these hybrid zeolite-silicate compositions should take to be useful as water softening agents other than as a powdered composition useful in a detergent composition as a detergent builder. The entire content of U.S. Pat. No. 5,948,383, is herein incorporated by reference.
In commonly assigned U.S. application Ser. No. 09/533,771, filed Mar. 23, 2000, and now U.S. Pat. No. 6,451,283, issued Sep. 17, 2002, the present inventors have found that high aluminum zeolites, including the hybrid zeolite-silicate compositions of U.S. Pat. No. 5,948,383 could be formed into uniform aggregates of submicron zeolite microcrystals by an in-situ process where essentially all of the aggregate material is between 1 and 5 microns. The aggregates of the application are formed from a solid source of aluminum which is included into a high silica/high alkaline environment. The product of the reaction is the formation of submicron crystals grown in-situ into macroscopic aggregates. What has been found is that even though the materials exist as macroscopic aggregates, the ion exchange kinetics are extraordinarily rapid, reflecting the inherent rate of the substituent submicron crystals. The application states that the advantages of maintaining the substituent crystals as coherent macroscopic aggregates is both in the ease of handling when the aggregates are used as a substituent in manufacturing compounds such as detergent mixtures as well as in minimizing pressure drop in flow-through application such as water purification/softening filters. The application also discloses that surprisingly, the rate of sequestration for multivalent cations can be improved even if only low levels of occluded silicate remain the zeolite. The morphology of the zeolites produced appears to have a profound and advantageous effect on hardness removal. Thus, the morphology of the zeolite aggregate containing the submicron crystalline zeolites is crucial to the hardness removal performance and that even if all the silica can be removed, the sequestration rate for complexing multivalent cations can be enhanced over large crystal zeolites.
As further disclosed in U.S. Ser. No. 09/533,771, the elevation of electrolyte concentration in the high silica/high alkaline synthesis mixture used to form the aggregates enhances the water softening properties of the materials. The addition of soluble salts to the synthesis mixture results in the formation of smaller submicron crystals (as manifested by increased exterior surface area) without reduction of aggregate particlesize (typically 1-5 microns). The entire content of U.S. Ser. No. 09/533,771 is herein incorporated by reference.
It is a primary objective of the present invention to produce superior static water softening materials.
It is another object of the present invention to provide water softening materials having improved hardness ion sequest
Bell Valerie A.
Curran Jacqueline S.
Kuznicki Steven M.
Langner Tadeusz W.
Engelhard Corporation
Lindenfeldar Russell G.
Sample David
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