CA1099485A

CA1099485A - Process for preparing amorphous sodium aluminosilicate base exchange materials

Info

Publication number: CA1099485A
Application number: CA239,075A
Authority: CA
Inventors: Lloyd E. Williams; Robert K. Mays
Original assignee: JM Huber Corp
Current assignee: JM Huber Corp
Priority date: 1974-11-08
Filing date: 1975-11-05
Publication date: 1981-04-21
Also published as: NO148677B; NO147179B; FI62961B; DK495875A; FR2290396B1; FR2290396A1; NO753724L; IN143367B; GB1496977A; NL7512646A; DE2549659A1; BR7507303A; AT358534B; HU172661B; FI62961C; SE7512453L; DE2549659C2; IT1052170B; FI753112A; SE413769B

Abstract

ABSTRACT OF THE DISCLOSURE
A method for producing certain novel finely divided amorphous, precipitated alkali metal alumino silicates having increased ion exchange properties is disclosed. The products of the invention are produced by commingling and precipitating, under certain controlled conditions, dilute aqueous solutions of an alkali metal silicate and alkali metal aluminate.
Significant process variables include the chemical composition and concentration of the reactants, the precipitating tempera-tures, and pH, the sequence and rate of the addition of the reactants and the mixing intensity during the precipitation.
The amorphous products of the invention have base or ion exchange capacities equal and/or superior to known crystalline zeolitic base exchangers or adsorbents and such may be used for water softening. Their use in detergents is also disclosed.

Description

l~g9485 BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to the synthetic amorphous precipitated alumino silicates and more particularly to the production of amorphous sodium alumino silicates having increased ion or base exchange properties.

The Prior Art Cation exchangeable materials and their use, for example, in water softenings, are well known in the art. While many products are known to possess such properties, in general, a particularly suitable class of ion exchangers are the so-called zeolites, which occur naturally in nature or may be produced synthetically. Crystalline alumino silicate zeolites structur-ally consist basically of an open three-dimensional framework of ; SiO4 and AlO4 tetrahedra. Specific examples of synthetic zeolites, methods for their production as well as their use as . . .
ion exchangers, adsorbents and the like are disclosed in U.S.
patents 2,882,243; 3,008,803; 2,962,355; 2,996,358; 3,010,789;
3,Q12,853; and 3,130,007. Other known base exchange materials are base exchange gels which are granular products made by the - -reaction of sodium silicate and aluminum compounds. These products have to some extent been used for large-scale water softening to remove calcium and magnesium from water and may be regenerated by passing a solution of NaCl through a filter bed of the hard granules. In this regard see U.S. patents 1,586,764;
1,717,777; 1,848,127; and British patent 177,746.

109~485 In recent years a number of synthetic amorphous, precipitated sodium alumino-silicates, manufactured and sold under the trademark "Zeolex", have been prepared. Examples of these products, and methods for their preparation, are disclosed in U.S. 2,739,073 and 2,848,346.
Such products have been found to be useful in a wide range of applications such as fillers and reinforcing products for rubber compounds, plastics, paper and paper coating compositions, paints, adhesives, etc. While such amorphous sodium alumino-silicates have been found to be useful in such applications, their use as a base or ion exchange product has here-tofore been considered impractical because of their low exchange capabilities.
It is accordingly a general ob;ect of the invention to provide a novel amorphous sodium alumino silicate having increased ion or base exchange properties.
A further object is to provide a method for precipitating high ion exchange amorphous alumino-silicates by the reaction of alkali metal sllicates and alkali metal aluminates, under certain controlled process conditions.
Yet another ob~ect is to provide an amorphous sodium alumino silicate for use in water softening and which has further particular utility for use in detergents.
In summary, the present invention relates to the production of synthetic amorphous sodium alumino-silicates which have increased ion or base exchange properties or characteristics. As briefly noted above, while known amorphous alumino-silicate ion products, (as disclosed in U.S. 2,739,073) are known to possess ion exchange capabilities, the products of the invention are superior to the extent that they have an increase of from about 2 to 5 times the ion exchange capacity over known amorphous products and are equal or superior to known crystalline materials, such as the above-discussed zeolites.

lW94~35 In one broad aspect of this invention there is provided a pro-cess for producing a finely divided amorphous alkali metal alumino silicate having a substantially increased ion exchange capacity, said method compris-ing the steps of preparing an aqueous solution of an alkali metal silicate, said silicate having a SiO2/M20 mole ratio of from about 2.2 to 2.8 wherein M is an alkali metal, subjecting said solution to vigorous agitation which imparts to the reaction mass high shear and turbulence and a lineal velocity of 300-400 ft/min, and contacting said solution with a dilute solution of an alkali metal aluminate, said aluminate having a M20/A1203 mole ratio of from ~bo~Jt l.2 to 2.8, continuing the agitation of the reaction mas~ forn~ed by the addition of said alkali aluminate to said alkali metal silicate solution, and maintaining the pH of said reaction mass at a level of at least 10.5 to thereby precipitate a finely divided amorphous alkali metal alumino silicate having an ion exchange capacity equal to cry-; stalline zeolites having an oil absorption of at least 75 cc/100 gm;
a BET surface area of at least 50 m /g; a pack density greater than 10 pounds per cubic foot, a mercury intrusion void greater than 2.0 ; cc/gm, and a base exchange capacity of at least 200 mg CaC03/gm, and - an initial water softening rate of 2.7 grains per gallon per minute.
The process of the invention involves carefully controlled precipitation conditions and as such, is in direct contrast to known crystallization, digestion, and/or gelation techniques. Critical -precipitation conditions include the chemical COmpoSition and con-centration of the reactants, the precipitating temperature and pH, the sequence and rate of the addition of the reactants and the mixing intensity during the precipitation. As to the composition of the reactants, the alkali metal silicate should have a SiO2/M20 mol ratio of from 2.2 to 2.8 wherein M is an alkali metal. The composition and concentration of the aluminate, as will be discussed in more detail hereinafter, must be controlled to maintain maximum solubility and stability. The precipitating temperature is on the order of between from about 15 to 70C and preferably 20 to 40C. The pH of the precipi-~;~ tating mass must be maintained above about 10.5. In the practice of the '- ' ~ ' ' , ' :

1~3994~9S
invention, the sequence of the addition of the reactants is critical to the extent that the reactants may not be simply admixed, as in known crystalli-zation, digestion and gelation processes, but they must be commingled in a manner such that the proportions of the individual reactive ionic species in ; the reaction area or zone has a predetermined concentration range.
As indicated, the products of the invention have high and increased ion exchange capacities. As such they are particularly suitable for use in water softening and in detergents. In this regard, additional benefits'of the new products of the invention include more bulking (lighter product), conditioning of finished product by anti-caking, less deposition or entrap-ment of these products in fabrics, higher absorptivity for non-ionic surfact-ants and better suspension in carrying-off waters (less settling).
Thus by another aspect of this invention there is provided a finely divided amorphous alkali metal alumino silicate having an ion exchange capacity equal to crystalline zeolites, which has the following chemical composition: M20 A1203 2.0-3.8SiO2 XH20, wherein M is alkali metal and X
has a value of 2.5 to 6, said alumino-silicate having an oil absorption of at least 75 cc/100 gm; a BET surface area of at least 50 m2/g; a pack density greater than 10 pounds per cubic foot, a mercury intrusion void greater than

2.0 cc/gm; and a base exchange capacity of at least 200 mg CaC03/gm.
The manner in which the above and further objects of the invention are achieved will be better understood in view of the following detailed descrip-tion and drawings, which form a part of this specification and, wherein:
Figures 1, 2 and 5 are microphotographs of known crystalline zeolitic alumino silicate exchangers produced in accordance with the teachings of U.S.
Patent 2,882,243.
Figures 3, 4 and 6 are microphotographs of the amorphous precipitated sodium alumino silicates produced in accordance with the practice of the present invention.

.-:

` 1~994#S

DESCRIPTION OF PREFERRED EMBODIMENT(S) As discussed above, the present invention relates to the production of amorphous sodium alumino silicates hav-ing increased base or ion exchange characteristics. In the practice of the invention, the high ion exchange amorphous product is produced by preparing an aqueous solution of an alkali metal silicate and first introducing this solution into a reactor or vessel provided with agitation means.
Heating means such as a steam jacket is also providedO The silicate should be such that it has an SiO2/X20 mole ratio of from 2.2 to 2.8, wherein X is an alkali metal. The alkali silicate solution so used should be of about 4 molar or lower concentration. Thereafter a dilute solution of an alkali metal aluminate, such as sodium aluminate (if sodium silicate is employed) is introduced slowly into the silicate solution.
Prior to the introduction, the silicate solution is heated to a temperature of between from about 15 to 70C. This temperature is maintained during the precipitation. The concentration of the aluminate solution should be 2 molar or lower and preferably about 1 molar. The aluminate should have a X20/A1203 mole ratio (wherein X is alkali metal) of from about 1.2 to 2.8. In any event, the pH of the reaction - -mass must be maintained above about 10.5 during the precipitation and preferably on the order of from about 11 to 13.5. A high mixing intensity must be maintained throughout the reaction period with this being particularly significant during the addition of the dilute aluminate solution.

' :

4~5 Upon completion of the reaction procedure the pre-cipitated product is usually separated from the reaction liquid by filtration, but other means of separation such as centrifuging can be used as well. It generally is desirable to wash the freshly separated product with water to remove water soluble salts and the like, after which it may be dried to obtain a friable mass which easily disintegrates into a fine powder. The drying temperature used on the precipitated product is important, as excessive drying of the product will lower its exchange capacity.
Although a specific preferred embodiment of the present invention has been disclosed in the detailed descrip-tion above, this description is not intended to limit the invention to the particular forms and embodiments disclosed herein. The present description is to be recognized as illustrative rather than restrictive, and it will be obvious to those skilled in the art that the invention is not so limited. The invention is thus declared to all changes and modifications of the specific examples and embodiments of the invention herein disclosed for purposes of illustration, which do not constitute departures from the spirit and scope of the invention defined by the appended claims.
As discussed, water-soluble sodium silicates and potassium silicates can be used according to this invention, but the much less expensive sodium silicates naturally are preferred. They are effective in compositions in which the ratio of SiO2 to alkali metal oxide is from 1 to about 4, including the common alkali silicates ranging from the meta silicate Na2O SiO2 to water glass with a composition of about Na2O 3.3 SiO2.

1~994~3S

commercially available and well known in the art being dis-closed, for example, in U.S. 2,882,243 or can be prepared by the reaction of the alkali metal oxide with reactive aluminum oxides or hydroxides.
The products of the invention can be characterized by having a typical chemical composition of Na2O A12O3 2.0-

3.8 SiO2 X H2O where X can have values of 2.5 to 6. The primary particles of the newly discovered amorphous product are spherical and generally in the 400-500 A diameter range.
The primary particles accrete into stable aggregates of irregular shapes and sizes. The aggregates can be described as similar in shape to "grape clusters" and the sizes range from 2000-5000A. The aggregates tend to form loosely struc-tured agglomerates which can easily be disrupted by mechanical forces.
As previously noted, the process for generating these products can be described as carefully controlled pre-cipitations as contrasted with the crystallization or digestion process that is associated with the preparation of crystalline products.
Distinguishing differences in the physical proper-ties of the various products are shown in Table I and perform-ance similarities are readily apparent in the data shown in Table II.
The utility of these products as water softening agents where their base exchange properties are evident can be evaluated by well known methods for calcium exchange capacity and exchange rates. For commercial application, the products should be able to exchange at least 250 mg.
CaCO3/g under the conditions of the test and should be able to deplete a 4.7 gr./gal. (calcium hardness) hard water to 2.0 gr./gal. in 1 minute and 1.0 gr./gal.in 10 minutes.
In this latter test, the base exchanger is added at a 0.06% level to mixed Ca-Mg hard water with 7.0 gr./gal. hardness. The results in Table II show that the amorphous and semi-crystalline products compare favorably with the crystalline product in performance.
Table III shows that excessive drying of the product from Examples I and II decreases the depletion and exchange capacity of this material. The % LOI includes bound H2O plus any moisture in the product.
The properties of the products of Examples III and IV are shown in Table IV. The effect of drying the product in terms of its exchange capacity is shown by using the product of ExampLe IV in the form of a wet cake.

1~)994i~S

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1~9948S

TABLE I I
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PERFORMANCE PROPERTIES
Min. Product of Product of Spec. Zeolite A Example I Example II
Ca Exchange Capacity 250 261 282 280 (mg. CaC03/g) Ca Depletion Rate, Residual Ca Hardness (gr./gal.) I 1 Minute <2.0 0.41 0.73 0.90 10 Minutes <1.0 0.1 0.22 0.20 1 :

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, 1099~8S

Product of Example I

CaCO3 Ca Depletion Rates Exchange CapacityResidual Ca Hardness % LOImg/g pigmen~ (Grains/Gallon) 1 mln. 10 min. I J
l9.Z 271 .62 .13 8.0 193 1.2 .74 .~ 1.4 141 2.4 1.6 Product _f Example II
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1(39~4~35 Additional benefits of these products are projected for more bulking (lighter product), conditioning of finished product by anti-caking, less deposition or entrapment of these products in fabrics, higher absorptivity for non-ionic surfactants and better suspension in carry-off waters (less settling).
As briefly noted above, the unique high ion exchange amorphous silicates of the invention have particular utility for use in liquid or dry detergent compositions or cleaning compounds. In this regard, the silicates of the invention may be used with any of the conventional detergent classes, i.e!, synthetic nonsoap anionic, nonionic and/or amphoteric surface active compounds which are suitable as cleansing agents. Anionic surface active compounds can be broadly described as compounds which contain hydrophilic or lyophilic groups in their molecular structure and which ionLze in an a~ueous medium to give anions containing the lyophilic group. These compounds include the sulfated or sulfonated alkyl, aryl and alkyl aryl hydrocarbons and alkali metal salts thereof, for example, sodium salts of long chain alkyl sulfates, sodium salts of alkyl naphthalene sulfonic acids, sodium salts of sulfonated abietenes, sodium salts of alkyl benzene sulfonic acids particularly those i4 which the alkyl group contains from 8-24 carbon atoms; sodium salts of sulfonated mineral oils and sodium salts of sulfo-succinic acid esters such as sodium dioctyl sulfosuccinate.
Advantageous anionic surfactants include the higher alkyl aryl sulfonic acids and their alkali metal and alkaline earth metal salts such as for ex~mple sodium dodecyl benzene sulfonate, sodium tridecyl sulfonate, magnesium dodecyl benzene sulfonate, potassium tetradecyl benzene sulfonate, ammonium 10994~35 dodecyl toluene sulfonate, lithium pentadecyl benzene sulfonate, sodium dioctyl benzene sulfonate, disodium dodecyl benzene disulfonate, disodium di-isopropyl naphthalene disulfonate and the like as well as the alkali metal salts of fatty alcohol esters of sulfuric and sulfonic acids, the alkali metal salts of alkyl aryl (sulfothioic acid) esters and the alkyl thiosulfuric acid, etc.
Nonionic surface active compounds can be broadly described as compounds which do not ionize but usually acquire hydrophilic characteristics from an oxygenated side chain, such as polyoxyethylene, while the lyophilic part of the molecule may come from fatty acids, phenols, alcohols, amides or amines.
Examples of nonionic surfactants include products formed by condensing one or more alkylene oxides of 2 to 4 carbon atoms, such as ethylene oxide or propylene oxide, preferably ethylene ! oxide alone or with other alkylene oxides, with a relatively hydrophobic compound such as a fatty alcohol, fatty acid, sterol, a fatty glyceride, a fatty amine, an aryl amine, a fatty mercaptan, tall oil, etc. Nonionic surface active agents also include those products produced by condensing one or more relatively lower alkyl alcohol amines (such as methanolamine, ethanolamine, propanolamine, etc.) with a fatty acid such as lauric acid, cetyl acid, tall oil fatty acid, abietic.acid, etc. to produce the corresponding amide.
Particularly advantageous nonionic surface active agents are condensation products of a hydrophobic compound having at least 1 active hydrogen atom and a lower alkylene oxide (for example the condensation product of an aliphatic alcohol containing from about 8 to about 18 carbon atoms) and from about 3 to about 30 mols of ethylene oxide per mol of the 1~3994~3S

alcohol, or the condensation product of an alkyl phenol containing from about 8 to about 1~ carbon atoms in the alkyl group and from about 3 to about 30 mols of ethylene oxide per mol of alkyl phenol. Other nonionic detergents include condensation products or ethylene oxide with a hydrophobic compound formed by condensing propylene oxide with propylene glycol.
Amphoteric surface active compounds can be broadly described as compounds which have both anionic and cationic groups in the same molecule. Such compounds may be grouped into classes corresponding to the nature of the anionic-forming group, which is usually carboxy, sulfo and sulfato. Examples of such compounds include sodium N-coco beta amino propionate, sodium N-tallow beta amino dipropionate, sodium N-lauryl beta iminodipropionate and the like.
Other typical examples of these categories of the anionic, nonionic and/or amphoteric surface active agents are described in Schwartz and Perry "Surface Active Agents", Inter-science Publishers, New York (1949) and the Journal of American Oil Chemists Society, Volume 34, No. 4, pages 170-216 (April 1957) The amount of the exchange silicates necessary to be used with the surface active compound (active) may vary depending upon the end use, type of active employed, pH
conditions and the like. The optimum active/exchanger ratio depends upon the particular active employed and the end use for which the detergent composition is intended but most generally will fall within the range of active/silicate exchange weight ratio of about 3:1 to 1:6.
The following examples will serve to further illu-strate the invention but are not intended to limit it thereto.

109~4~35 EXAMPLE I
A 30 gallon baffled reactor was provided with a turbine type agitator having blades 6 inches in diameter rotatable at 250 R.P.M. A dilute alkali silicate solution was prepared by dissolving 4.45 lbs. of sodium silicate (Na2O~O.2.5 SiO2) in 5.54 gals. of water, and a dilute solution of sodium aluminate 1.6 Na2O/A12O3 was prepared by dissolving 10.5 lbs. thereof in 4.46 gals. of water. The reactor was charged with the silicate solution, and the agitator was started. The aluminate solution was then introduced, in a thin stream, so as to strike t~e surface of the vigorously agitated liquid near the wall of the reactor. The addition of the sodium aluminate solution was continued for 30 minutes. A total of 4.46 gals. of the solution was used. The temperature during the reaction was 50C. Agitation of the reaction material was continued for 5 minutes, and then the precipitate was separated by the filtration and thoroughly washed with water. The result-ing filter cake was dried at 110C. to obtain a friable cake -which disintegrated readily into a powder when squeezed. This cake was passed once through a screen mill with the screen removed, in order to convert the agglomerated mass completely into a fine powder. The yield was 7.75 lbs. The properties -of the product are shown in Tables I and II.
. .
EXAMPLE II
The same procedure of Example I was repeated except the agitation of the precipitated pigment was continued for 30 minutes before the product was separated by filtration and washing. Properties of this product are shown in Tables I and II.

.

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1~)9~35 EXAMPLE III
This example was performed by use o-f the same equipment and procedure as described in Example I. The reactor was charged with a silicate solution prepared by dissolving 6.75 lbs. of a sodium silicate having the compo-sition Na2).2.4 SiO2 in 8.3 gallons of water and an alumin-ate solution was prepared by dissolving 20.8 lbs. of sodium aluminate 2.6 Na2O/A12O3 in 16.2 gallons of water. The precipitate then present was filtered off, dried, and pulverized as described in Example I. Properties of this product are shown in Table IV.
EXAMPLE IV
The procedure of Example III was repeated. The only change was that the reaction temperature was lowered to 25C.
EXAMPLE V
The general procedures of Examples I and II were repeated except that silicate and aluminate having SiO2/Na2O
mole ratios of from 2.2 to 2.8 and Na2O/A12O3 mole ratios of from 1.2 to 2.8, respectively, were substituted for the materials employed in Examples I and II. By varying the oxide mole ratios it was found that products having an oil absorption of at least 75 cc/100 gm and BET surface areas of at least 50 m2/g could be produced. Mercury intrusion voids were higher than 2.0 cc/gm. The base exchange capacities were at least 200 mg CaCO3/gm. Water softening rates were on the order of about 2.7 grains per gallon per minute.

1~39~4~S

As used herein, the term "product" is intended to refer to tlle ~inely divided, amorphous nature of the materials.
The magnifications of Figures 1 through 6 are 4,400X;
11,000X; 4,400X; 11,000X; 20,500X and 20,500X, respectively.
All test data was obtained by well known, standard and industry recognized test methods. For example, oil absorption values were obtained in accordance with ASTN-D281-31 (1966) Adopted 1931, reapproved 1966; pH by ASTN-E70-68 (1973); surface area by the method of Bruner, Emmett, Teller, Jor. of Am. Chem. Soc., 60, 309-16 (1938);
mercury intrusion by the method of 1958 ASTM Proc. Manual ASTM Bull.
(1959) TP-49-54; pack density by ASTM C493, 17, C373, 17; and the base exchange capacity and water softening rate in acco~dance with DOS 2412837 (31 October 1974).

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the production of a finely divided amorphous alkali metal aluminosilicate product which comprises the following steps:
(a) preparing an aqueous solution of an alkali metal silicate having a concentration of 4 molar or lower, said silicate having an SiO2/M2O mole ratio of 2.2 to 2.8, wherein M is an alkali metal;
(b) subjecting said aqueous solution to vigorous agitation which imparts to the reaction mass high shear and turbulence and a linear velocity of 300-400 feet per minute; and introducing slowly into said solution a dilute solution of an alkali metal aluminate, said aluminate solution having a concentration of 2 molar or lower and having an M2O/Al2O3 mole ratio of from 1.2 to 2.8, wherein M is alkali metal, and at a temperature of about 15° to 70°C;
(c) continuing the vigorous agitation of the reaction mass formed by the addition of said alkali metal aluminate to said alkali metal silicate solution while maintaining the pH of said reaction mass during the precipitation at a level at least above 10.5 to thereby precipitate the finely divided amorphous alkali metal aluminosilicate; and (d) recovering the alkali metal aluminosilicate.

2. A process according to claim 1 wherein the alkali metal M
is sodium.

3. The method in accordance with claim 1 wherein an alkali metal hydroxide is premixed with the alkali metal silicate solution or the alkali metal aluminate solution to provide an excess of Me2O present during the precipitation of the product, where M is an alkali metal.

4. A method according to claim 2 wherein the aqueous solution of sodium aluminate is slowly added to the aqueous solution of sodium silicate at a temperature of about 20 to 40°C.