CA1148919A - Process for the production of finely-divided, low grit, zeolitic sodium aluminosilicates - Google Patents
Process for the production of finely-divided, low grit, zeolitic sodium aluminosilicatesInfo
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- CA1148919A CA1148919A CA000373952A CA373952A CA1148919A CA 1148919 A CA1148919 A CA 1148919A CA 000373952 A CA000373952 A CA 000373952A CA 373952 A CA373952 A CA 373952A CA 1148919 A CA1148919 A CA 1148919A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/20—Silicates
- C01B33/26—Aluminium-containing silicates, i.e. silico-aluminates
- C01B33/28—Base exchange silicates, e.g. zeolites
- C01B33/2807—Zeolitic silicoaluminates with a tridimensional crystalline structure possessing molecular sieve properties; Isomorphous compounds wherein a part of the aluminium ore of the silicon present may be replaced by other elements such as gallium, germanium, phosphorus; Preparation of zeolitic molecular sieves from molecular sieves of another type or from preformed reacting mixtures
- C01B33/2815—Zeolitic silicoaluminates with a tridimensional crystalline structure possessing molecular sieve properties; Isomorphous compounds wherein a part of the aluminium ore of the silicon present may be replaced by other elements such as gallium, germanium, phosphorus; Preparation of zeolitic molecular sieves from molecular sieves of another type or from preformed reacting mixtures of type A (UNION CARBIDE trade name; corresponds to GRACE's types Z-12 or Z-12L)
- C01B33/2823—Zeolitic silicoaluminates with a tridimensional crystalline structure possessing molecular sieve properties; Isomorphous compounds wherein a part of the aluminium ore of the silicon present may be replaced by other elements such as gallium, germanium, phosphorus; Preparation of zeolitic molecular sieves from molecular sieves of another type or from preformed reacting mixtures of type A (UNION CARBIDE trade name; corresponds to GRACE's types Z-12 or Z-12L) from aqueous solutions of an alkali metal aluminate and an alkali metal silicate excluding any other source of alumina or silica
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- Silicates, Zeolites, And Molecular Sieves (AREA)
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Abstract
ABSTRACT OF THE DISCLOSURE
An improvement in the process for the production of aqueous, alkaline suspensions of finely divided low grit, crystalline, zeolitic sodium aluminosilicate by continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presence of excess sodium hydroxide solution at elevated tempera-tures and subsequently crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, at an elevated temperature, the improvement consisting of conducting said first mixing step at a temperature not to exceed 50° C, introducing finely-dispersed steam into said aqueous, alkaline suspension of X-ray amorphous sodium aluminosilicate for a period of at least 15 minutes while stirring, to heat said suspen-sion to a temperature of from 85° to 95°C, and crystal-lizing at this temperature for a period of 20 to 60 minutes while stirring with multistage agitators at a circumferential agitator speed of from 5 to 10 meters per second. When following the above procedures, a finely-divided crystalline zeolytic sodium aluminosilicate is obtained with an extremely low grit content of 0.05% or less by weight.
-A-
An improvement in the process for the production of aqueous, alkaline suspensions of finely divided low grit, crystalline, zeolitic sodium aluminosilicate by continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presence of excess sodium hydroxide solution at elevated tempera-tures and subsequently crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, at an elevated temperature, the improvement consisting of conducting said first mixing step at a temperature not to exceed 50° C, introducing finely-dispersed steam into said aqueous, alkaline suspension of X-ray amorphous sodium aluminosilicate for a period of at least 15 minutes while stirring, to heat said suspen-sion to a temperature of from 85° to 95°C, and crystal-lizing at this temperature for a period of 20 to 60 minutes while stirring with multistage agitators at a circumferential agitator speed of from 5 to 10 meters per second. When following the above procedures, a finely-divided crystalline zeolytic sodium aluminosilicate is obtained with an extremely low grit content of 0.05% or less by weight.
-A-
Description
1~8~31~
The subject of the invention is a process for the preparation of an aqueous alkaline suspension of finely-divided, low-grit, crystalline, zeolitic sodium alumino-silicates by continuous mixing of an aqueous sodium aluminate solution with an aqueous sodium silicate solu-tion and subsequent intermittent crystallization of the aqueous alkaline suspension of the X-ray-amorphous sodium aluminosilicates formed.
X-ray amorphous sodium aluminosilicates are prepared as a rule by intermittent or continuous mixing of an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presenc~ of excess soda lye at elevated temperatures, that is, at temperatures in the range of 55 to 70C. The mixing and concentration ranges of the reaction partners used in the industry correspond generally to a mathematical total composition regarding the molar ratios of:
1.5 to 5 Na2O : 1 A12O3 : 1 to 4 SiO2 : 40 to 400 H2O-With these mixing ratios, a suspension of an X-ray amor-phous hydrous sodium aluminosilicate with a great excess of soda lye is always formed. After separating the mother liquor and washing out the excess alkali, corresponding X-ray amorphous products can be isolated from such a suspension, whose water content is determined to a great extent by the degree of dryness and whose silicate content is determined to a great extent by the SiO2/A12O3 molar ratio in the reaction mixture. For most technical purposes, however, such amorphous sod~um aluminosilicates --1-- ' l~B~
are not used, but their crystalline, preferably zeolitic secondary products are employed.
The so-called zeolites form a mineral class of crystalline, water-containing alkali metal aluminosili-cates with a defined pore and cavity structure of their aluminosilicate lattice. Synthetic zeolites have gained increasing technical importance and are used, for e~ample, as cation exchangers primarily for softening water, as catalyst substrates in chemical processes, as drying, separating and sorption agents for solvents and gases (molecular sieves), as well as heterogeneous inorganic builder substances in washing and cleaning agents.
Depending on their use, structurally different zeolite types are required, as well as different degrees of dry-ness and purity. Normally these zeolites are produced first in their sodium form and, if desired, converted subsequently by cation-exchange into other forms.
In view of the above-mentioned applications, the zeolitic sodium aluminosilicate of the NaA type has gained particular technical importance. The chemical composition of this zeolite corresponds substantially to the summation formula:
0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2.5 SiO2 : 0 to 6 H2O.
The characteristic X-ray diffraction diagram of zeolite NaA is described, for example, in U. S. Patent No. 2,882,243.
The con~ersion of amorphous sodium aluminosili-cates to the crystalline zeolitic forms is a crystalliza-tion process which depends on various parameters and which increases in speed with rising temperature. As a rule the suspension of the amorphous product obtained in the first :, . ~ ,. , : .
~ ~8~1~
stage, the mixing of the reaction partners, is kept at elevated temperatures for a certain period. Depending O]l the molar ratios of the reaction partners in the batch and on the temperature control, the formation of crystal-line products requires a period of several minutes to several days. For the production of zeolite NaA, this crystallization process is effected primarily under normal pressure and at temperatures between 70 and 100C.
In this way, a highly crystalline zeolite NaA can generally be obtained from a corresponding composition of the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicates.
For most technical applications, a very finely-divided zeolite with a possibly narrow-banded particle size distribution and a mean grain size under lO~m is preferred. Particularly when zeolite NaA is used in washing and cleaning agents, its share of particles with a particle size above 50,um, hereafter called "grit", should not exceed 0.2% by weight and preferably be well ~elow this limit, and its cation exchanging capacity should be as high as possible.
In the intermittent reaction of the components and the subsequent intermittent crystallization, zeolites of type NaA were heretofore obtained under conventional reaction and crystallization conditions, which had grit values in the range of 0.05% to 0.3~ by weight. In the continuous mixing of the reaction partners and subsequent intermittent crystallization, however, zeolites with grit values between 0.1% and 0.2% by weight were obtained under the usual working conditions.
~ .
~8~319 An object of the present invention is to develop a process for the preparation of finely-divided zeolitic sodium aluminosilicates which leads to a zeolite NaA with a grit portion of less than 0.05% by weight, as well as a high cation exchanging capacity.
Another object of the present invention is the development of an improvement in the process for the production of aqueous, alkaline suspensions of finely divided low-grit, crystalline, zeolitic sodium alumino-silicates of the formula 0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 with a water content depending upon the degree of drying,and a high cation exchanging capacity comprising the steps of a) continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solu-tion in the presence of excess sodium hydroxide solution at elevated temperatures, and b~ subsequently batch crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, said suspension having a total composition of the molar ratios of 3.6 to 5 Na2O : 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
at an elevated temperature the same or-higher than the temperature in step a), : the improvement consisting essentially of c) conducting said mixing step a) at a tempera-ture above room temperature but not exceeding 50CI
d) introducing finely dispersed steam into . .,. , : ~ : ~
~8~9 said aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate for at least 15 minutes while stirring, e~ to heat said suspension to a crystallization temperature of from 85C to 95C, fl maintaining said crystallization temperature for a period of 20 to 60 minutes, and g) stirring said suspension during the course of steps d) to f) with multistage agitators having a high shearing effect at a circumferential agitator speed of from 5 to 10 meters per second, whereby said low-grit, crystalline, zeolitic sodium aluminosilicate is obtained having a particle size of at least 99.95~ by weight of less than 50~m and a high cation exchanging capacity.
These and other objects of the invention will become more apparent as the description thereof proceeds. -~
The above objects have been achieved by the process of the present invention. The subject matter of the invention is, therefore, a process for the preparation of an aqueous, alkaline suspension of finely-divided, low-grit, crystalline, zeolitic, sodium aluminosilicates of the composition:
0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 with a water content depending on the degree of drying where at least 99.95% by weight have a particle size of less than 50~m and having a high cation exchanging capacity by the process of ~5~
8~
a) continuous mixing of an aqueous sodium ~
aluminate solutdon with an aqueous sodium silicate sQlu-tion in the presence of excess sodium hydroxide solution a1; elevated temperature and b~ subsequent intermittent crystallizing of the aqueous alkaline suspension of the X-ray amorphous, sodium aluminosilicates formed, said suspension having a total composition corresponding to molar ratios of 3 6 to 5 Na2O 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
likewise at elevated temperature, which is characterized in that c) the two reaction components in stage a) are mixed with each other at a temperature not exceeding 50C, d) finely dispersed steam is introduced into the suspension in stage b) in the course of at least 15 minutes under stirring, e) the suspension is heated this way until crystallization temperature in the range of 85 to 95C
has been attained, f) the suspension is left at this crystalliza-tion temperature for a period of 20 to 60 minutes, and g) the suspension is stirred at the same time with multi-stage agitators having a high shearing effect at a circumferential agitator speed of 5 to lO m/s.
More particularly, the present invention relates to an improvement in the process for the production ;~ of aqueous, ~lkaline suspensions of finely divided low-grit, crystalline, zeolitic sodium aluminosilicates of the formula .,, ~ ; . .
0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 with a water content depending upon the degree of drying, and a high cation exchanging capacity comprising the steps of a) continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presence of excess sodium hydroxide solution at elevated temperatures, and . b) subsequently batch crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, said suspension having a total composition of the molar ratios of 3.6 to 5 Na2O : 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
at an elevated temperature the same or higher than the temperature in step a), the improvement consisting essentially of c) conducting said mixing step a) at a temperatur~ above room temperature but not exceeding 50C, d) introducing finely dispersed steam into said aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate for at least 15 minutes while : .
stirring, e) to heat said suspension to a crystallization temperature of from 85C to 95C, f) maintaining said crystallization temperature for a period of 20 to 60 minutes, and g) stirring said suspension during the course o~ steps d) to f) with multistage agitators having a high shearing effect at a circumferential agitator speed of ~`, msA~ .
~8~1~
from 5 to 10 meters per second, whereby said low-grit, crystalline, zeolitic sodium aluminosilicate is obtained having a particle size of at least 99.95% by weight of less than 50~m and a high cation exchanging capacity.
It was found,surprisingly,that maintaining the above-mentioned measures, in the continuous reaction stage, on the one hand, and in the intermittent or batch crystallization stage, on the other hand, leads to the formation of zeolitic sodium aluminosilicates type NaA
with the desired extremely low-grit content of less than 0.05% by weight. This objective is aahieved according to the invention by the cooperation of the parameters sub-stantially influencing the formation of finely-divided zeolite particles, as characterized above in the process features c) to g). In addition, the sodium alumino-silicates thus obtained have a high cation exchanging capacity.
For the first stage of the process according to the invention, hereafter called the precipitation stage, which leads to the formation of an aqueous alkaline suspen-sion of X-ray amorphous, sodium aluminosilicates, those methods generally are used which permit continuous mixing of the reaction partners, sodium aluminate solution and sodium silicate solution, in suitable reactors. Examples of such methods are, for example:
Mixing the components by means of suitable spray nozzles, whereby the reaction partners meet only in the spray jet, with formation of an X-ray amorphous product.
. ~ ~
~1~8~'319 Mixing the components in a mixing zone acting in stages, where one of the two reaction compo-nents is divid~d into sevexal partial currents, one of which is added directly and continuously to the total current of the other reaction com-ponent, and the othe partial currents are added, likewise, continuously downstream to the current of the reaction mixture formed. As a .
mixing zone acting in stages in the foregoing sense, particularly stirring ~essel cascades, stirrer columns with chambers separated by partitions, stepped differential worm mixers and tu~ular reactors, can be used.
The foregoing methods mentioned by way of example are described in detail in the;copending Canadian patent .. . . . . . . . .
applications,Serial No. 342,139 filed Dec mber 18, 1979, now Patent No. 1,109,638; Serial No. 347,661, filed March 14, 1980; and Serial No. 347,662, filed Maxch 14, 1980.
Beyond that all corresponding continuous méthods for the production of X-ray amorphous sodium alumino-silicates can be used according to the invention, provided a precipitation or mixing temperature of not more than 50C is maintained in the precipitation stage. Particu-larly pxeferred in the sense of the invention is miY~ing the reaction components at a temperature in the range of 40 to 50~C.
In order to obtain a zeolitic sodium alumino-silicate type NaA, th?t i5, a zeolite ~ith a composition having the molar ratios of ~ . .
~1~8~9 0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 and a water content depending on the degree of drying, the dosage of the reaction components must be so selected in this precipitation stage that the aqueous alkaline suspension of the X-ray amorphous sodium aluminosilicates formed has a total composition corresponding to molar ratios of 3.6 to 5 Na2O : 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O-In the intermittent or batch crystallization stage following the continuous precipitation stage, the maintenance of additional parameters is of essential importance according to the invention.
The aqueous alkaline suspension of X-ray amorphous sodium aluminosilicates formed in the continuous precipi-tation stage i~ as a rule first transferred to one of several parallel connected crystallization vessels whose number and dimensions should preferably be so selected that they ensure the reception of the continuous suspension current flowing from the continuous precipitation stage.
The intermittent crystallization of the amorphous product then takes place in these crystallization vessels, which should be equipped according to the invention with multi-stage agitators having a high shearing action.
The crystallization process proper is started by heating the suspension, under constant stirring, to the required crystallization temperature. It is of essential importance that the suspension is not heated too fast.
According to the invention, the suspension is heated in the course of at least 15 minutes, preferably in the course of 20 to 30 minutes, until the crystallization ~ c~19 temperature is attained. Furthermore, the manner of heating is also important according to the invention.
It was found that best results are obtained by introducing finely-dispersed steam directly into the suspension in view of obtaining a low-grit content of the resulting crystalline product. The introduction of the finely-dispersed steam into the suspension can be effected,for example, by ring conduits arranged on the bottoms of the respective crystallization vessels and provided with many small orifices. However, other arrangements which ensure direct introduction of finely-dispersed steam into the suspension can also be used, According to the invention, the suspension is heated this way until a temperature of 85 to 95C, preferably 90 to 93C, is attained over the period of at least 15 minutes, preferably over 20 to 30 minutes. The heated suspension is left subsequently at this temperature for 20 to 60 minutes, preferably 30 to 40 minutes, during which time the amorphous product crystallizes to a zeo-litic sodium aluminosilicate, type NaA.
During the entire crystallization process, that is, from the start of heating, the suspension of the amorphous product or the forming crystalline product should be stirred vigorously by means of a multi-stage agitator with a high shearing power. According to the invention, the strength and the intensity of this agitator, that is, the circumferential agitator speed, is 5 to 10 meters per second, preferably to 6 to 8 meters per second.
Agitators that are suita~le for this purpose are, for example, turbines or turbine-like stirring apparatus with multi-stage propellers, which are characterized by a ,: :
strong shearing action. The number of stages of the agitator depends primarily on the geometric form of the selected crystallization vessel. Since the shearing action of these agitators is greatly influenced by the shape of the agitator, it was found particularly advanta-geous in the sense of the invention to stir the suspension with axially moving agitators with a high shearing action, particularly trapezoidal agitators with curved stirring blades.
If the essential features of the process accord-ing to the invention are maintained, particularly in the procedures characterized as preferred, a finely-divided, crystalline zeolitic sodium aluminosilicate, type NaA, is obtained after the crystallization, which is charac-terized by a grit portion of less than 0.05% by weight and high cation exchanging capacity.
For the identification of the crystallization product obtained, samples are filtered off, washed alkali-free, dried overnight in a vacuum drying cabinet at 100C
and identified on the basis of their X-ray diffraction diagram. The particle size distribution is measured as the % by volume distribution of the crystallized particles by means of a Coulter-Counte ~ , for example, model TA.
The grit portion in the crystallized product, that is, the portion of particles with a particle size above 50~um, is determined by a modified wet-screening method according to Mocker, where a weighed sample of the crystalline material suspended with water is placed in a testing apparatus by Mocker (DIN 53 580) on a test screen with a mesh aperture of 50,um (DIN 4188~ and whirled by means of water sprayed from rotating nozzles. The fine 3S~3~9 portions of the crystalline material are flushed this way without pressure through the screen, while the coarse portions (grit) remain on the screen. After 2 minutes, with a spray of 80 liters of water per hour, the test screen is dried in the drying cabinet at 110C and subse-quently, the screenings are determined by a differential weighing. The screenings result from the formula % by weight screenings = (a-b) .100 with a = weight of screen with screenings b = weight of screen without screenings E = weight of sample in gm based on the dry material.
The measure of the cation exchanging capacity of the crystalline zeolitic material i8 the calcium-binding power of 1 gm of sodium aluminosilicate (active sub-stances = AS] per liter in a liter of water with an initial hardness of 30dH (German hardness). For the determination of the calcium-binding power, 1 liter of an aqueous solution containing 0.594 gm of CaC12 (corres-ponding to 300 mg CaO/1=30dH) is adjusted with diluted sodium hydroxide solution to a pH value of 10 and mixed with 1 gm of aluminosilicate ~AS). The suspension formed is subsequently stirred vigorously for 15 minutes at a temperature of 22 + 2C. After the sodium alumino-silicate is filtered off, the residual hardness X in the filtrate is determined by complexometric titration by means of ethylenediamine tetraacetic acid. The calcium-binding power in mg CaO/gm~AS is calculated according to the formula: (30 - X) . 10.
~8~
The suspension of finely-divided, low-grit, crystalline zeolitic sodium aluminosilicates, type NaA, iis~ as a rule, further processed after the crystallization i'3 completed. To this end the crystalline solid substance is filtered off, washed and dried or prepared in any other way, depending on the desired application. Thus, an a~ue-ous suspension of the crystalline, sodium aluminosilicate can also be used, if necessary, for the production of wash-ing and cleaning agents. Mother liquor and wash liquor are preferably returned into the production process.
Due to the great cation-exchanging capacity of the zeolitic sodium aluminosilicate obtained, which mani-fests itself in a calcium-binding power of 150 to 200 mg CaO/gm AS, it is preferably used as a heterogeneous inor-ganic builder (phosphate su~stitute) in detergents, rinses and cleansers~
The f~llowing examples describe the procedure used in the process accoxding tQ the invention but are not limitative thereto.
For the continuous precipitation stage, a vértical agitator column with an effective volume of 188 liters was used, which was divided by partitions into a total of 28 chambers and which was equipped with the same number of MIG agitators. The shaft common to all agi-i tators was driven by means of a corresponding motor at a speed of 390 min 1. The~entire column cylinder was pro-vided with a heating jacket. The reaction components, which had been preheated to a precipitation temperature of 50C, were fed through suitable dosing devices, such as .. . . .
.
~8~3~9 pumps and rotameters, into the bottom chambers of the agi-t:ator column. The movement of the reaction mixture from chamber to chamber was effected through staggered ring slots provided in the partitions, so that a continuously rising product flow was obtained in the column. The dos-ing of the reaction components was: 549 kg/h of sodium silicate solution, 1315 kg/h of sodium aluminate solution, as well as 1136 kg/h of alkaline mother liquor from one of the preceding crystallization stages, the composition of the reaction product formed corresponded to molar ratios of 4.2 Na2O : 1 A12O3 : 1.8 SiO2 : 95 H2O.
The suspension of the amorphous reaction product issuing continuously from the top of the agitator column was gradually transferred into three crystallization vessels with a volume of 6 cu. meters each, which were equipped with two-stage propeller agitators with a high shearing power. As soon as the bottom blade dipped com-pletely into the suspension, the respective agitator was start~ed with a circumferential agitator speed of 6.9 m.s 1. After a crystallization vessel was filled, finely-dispersed steam was injected directly into the suspension under a pressure of 4 bar through a ring conduit arranged on the bottom of each vessel, and the temperature of the suspension was thus increased within 20 minutes to 93C.
The suspension remained at this crystallization tempera-ture for a period of 40 minutes under constant stirring, at a circumferential agitator speed of 6.9 m.s 1.
Su~sequently, the contents of each crystallization vessel was transferred to a filter unit, where the crystalline products obtained were washed and dried, and the resulting .
- . .
mother liquor returned into the precipitation stage of the process.
The crystalline reaction products formed were according to the X-ray diffraction diagram type NaA zeo-lites. The particle size determined with the Coulter-Counter showed a maximum of the particle size distribution of 3 to 5~m. The calcium binding power was 175 mg CaO/gm AS. The grit portion was 0.02~ by weight.
The example was carried ~t in analogy to Example 1 with the following modification:
The molar composition of the reaction mixture was 4 Na2O : 1 A12O3 : 1.8 SiO2 : 105 H2O
A crystalline of type NaA zeolite with a calcium-binding power of 181 mg CaO/gm AS and a grit portion of 0.03% by we~ght, was obtained.
This example was carried out in analogy to Example 1 with the following modification:
The molar composition of the reaction mixture was 4.5 Na2O : 1 A12O3 : 1.8 SiO2 : 95 H2O.
A crystalline of type NaA zeolite with a calcium-binding power of 172 mg CaO/gm AS and a grit portion of 0.03~ by weight, was obtained.
The precipitation stage was carried out in analogy to Example 1. The crystallization stage was carried out in three crystallization vessels which were equipped with different agitators of different , ~ ' '' "-shearing action. In vessels A and B, the stirring was effected with straight-arm paddle agitators at a circum-i-erential speed of less than 5 m.s l. In vessel A, the stirring speed waS3.6 m.slandin vessel B, it was4.5 m.s l.
:[n vessel C, the stirring was effected with an axially moving trapezoidal agitator with curved blades at a circumferential speed of 7.1 m.s 1. The heating rate to the crystallization temperature of 90C was in all three vessels 25 minutes, the following stay period 30 minutes.
Otherwise, we proceeded as described in Example l. The NaA zeolites formed in all cases differed substantially in the following features:
Vessel A B
calciu~bi~ p~wer in mg CaO/gm AS177 171 172 grit portion in % by weight 0.720.08 0.01 The example was carried out as in Example 1 but under the following modified reaction conditions:
precipitation temperature: 44C; heating time: 26 minutes;
subsequent stay period: 30 minutes.
The type NaA zeolites formed had a calcium-binding power oi 169 mg CaO/gm ~S and a grit portion of 0.02% b~ weight.
The following comparison tests, where the criti-cal process features essential for the invention were not maintained, will likewise illustrate the impo~rtance of these features in the grit portion of the zeolites formed.
:
COMP~RISON EXAMPLE 1 This example was carried out as in Example 1 but the reaction components were mixed in the precipita-t:ion stage at a temperature of 65C. Type NaA zeolites were obtained which had a calcium-binding power of 178 mg CaO/gm AS and a grit portion of 0.2% by weight.
CO~PARISON EXAMPLE 2 This example was carried out likewise as in Example 1. The heating in the crystallization vessel of the suspension formed in the precipitation stage was effected, however, within 7 minutes by direct injection of steam by means of a steam lance. The resulting type NaA
zeolites had a calcium~binding power of 174 mg CaO/gm AS
and a grit portion of 0.34% by weight.
Comparison Example 2 was repeated, with the suspension in the crystallization vessel heated slower, within 28 minutes, but likewise ~y direct injection of steam by means of a steam lance. The resulting type NaA
zeolites had a calcium-binding power of 168 mg CaO/gm AS
and a grit portion of 0.2% by weight.
The first comparison tests show the importance of the relatively low precipitation temperature according to the invention. The other two comparison tests show clearly the determinant influence of the heating time, on the one hand, and the manner of heating, without finely-dispersed steam, on the other hand, on the grit content of the crystalline product.
. ~
:
~8~19 The preceding specific embodiments illustrate the practice of the invention. It is to be understood, however, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims.
--19-- :
The subject of the invention is a process for the preparation of an aqueous alkaline suspension of finely-divided, low-grit, crystalline, zeolitic sodium alumino-silicates by continuous mixing of an aqueous sodium aluminate solution with an aqueous sodium silicate solu-tion and subsequent intermittent crystallization of the aqueous alkaline suspension of the X-ray-amorphous sodium aluminosilicates formed.
X-ray amorphous sodium aluminosilicates are prepared as a rule by intermittent or continuous mixing of an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presenc~ of excess soda lye at elevated temperatures, that is, at temperatures in the range of 55 to 70C. The mixing and concentration ranges of the reaction partners used in the industry correspond generally to a mathematical total composition regarding the molar ratios of:
1.5 to 5 Na2O : 1 A12O3 : 1 to 4 SiO2 : 40 to 400 H2O-With these mixing ratios, a suspension of an X-ray amor-phous hydrous sodium aluminosilicate with a great excess of soda lye is always formed. After separating the mother liquor and washing out the excess alkali, corresponding X-ray amorphous products can be isolated from such a suspension, whose water content is determined to a great extent by the degree of dryness and whose silicate content is determined to a great extent by the SiO2/A12O3 molar ratio in the reaction mixture. For most technical purposes, however, such amorphous sod~um aluminosilicates --1-- ' l~B~
are not used, but their crystalline, preferably zeolitic secondary products are employed.
The so-called zeolites form a mineral class of crystalline, water-containing alkali metal aluminosili-cates with a defined pore and cavity structure of their aluminosilicate lattice. Synthetic zeolites have gained increasing technical importance and are used, for e~ample, as cation exchangers primarily for softening water, as catalyst substrates in chemical processes, as drying, separating and sorption agents for solvents and gases (molecular sieves), as well as heterogeneous inorganic builder substances in washing and cleaning agents.
Depending on their use, structurally different zeolite types are required, as well as different degrees of dry-ness and purity. Normally these zeolites are produced first in their sodium form and, if desired, converted subsequently by cation-exchange into other forms.
In view of the above-mentioned applications, the zeolitic sodium aluminosilicate of the NaA type has gained particular technical importance. The chemical composition of this zeolite corresponds substantially to the summation formula:
0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2.5 SiO2 : 0 to 6 H2O.
The characteristic X-ray diffraction diagram of zeolite NaA is described, for example, in U. S. Patent No. 2,882,243.
The con~ersion of amorphous sodium aluminosili-cates to the crystalline zeolitic forms is a crystalliza-tion process which depends on various parameters and which increases in speed with rising temperature. As a rule the suspension of the amorphous product obtained in the first :, . ~ ,. , : .
~ ~8~1~
stage, the mixing of the reaction partners, is kept at elevated temperatures for a certain period. Depending O]l the molar ratios of the reaction partners in the batch and on the temperature control, the formation of crystal-line products requires a period of several minutes to several days. For the production of zeolite NaA, this crystallization process is effected primarily under normal pressure and at temperatures between 70 and 100C.
In this way, a highly crystalline zeolite NaA can generally be obtained from a corresponding composition of the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicates.
For most technical applications, a very finely-divided zeolite with a possibly narrow-banded particle size distribution and a mean grain size under lO~m is preferred. Particularly when zeolite NaA is used in washing and cleaning agents, its share of particles with a particle size above 50,um, hereafter called "grit", should not exceed 0.2% by weight and preferably be well ~elow this limit, and its cation exchanging capacity should be as high as possible.
In the intermittent reaction of the components and the subsequent intermittent crystallization, zeolites of type NaA were heretofore obtained under conventional reaction and crystallization conditions, which had grit values in the range of 0.05% to 0.3~ by weight. In the continuous mixing of the reaction partners and subsequent intermittent crystallization, however, zeolites with grit values between 0.1% and 0.2% by weight were obtained under the usual working conditions.
~ .
~8~319 An object of the present invention is to develop a process for the preparation of finely-divided zeolitic sodium aluminosilicates which leads to a zeolite NaA with a grit portion of less than 0.05% by weight, as well as a high cation exchanging capacity.
Another object of the present invention is the development of an improvement in the process for the production of aqueous, alkaline suspensions of finely divided low-grit, crystalline, zeolitic sodium alumino-silicates of the formula 0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 with a water content depending upon the degree of drying,and a high cation exchanging capacity comprising the steps of a) continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solu-tion in the presence of excess sodium hydroxide solution at elevated temperatures, and b~ subsequently batch crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, said suspension having a total composition of the molar ratios of 3.6 to 5 Na2O : 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
at an elevated temperature the same or-higher than the temperature in step a), : the improvement consisting essentially of c) conducting said mixing step a) at a tempera-ture above room temperature but not exceeding 50CI
d) introducing finely dispersed steam into . .,. , : ~ : ~
~8~9 said aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate for at least 15 minutes while stirring, e~ to heat said suspension to a crystallization temperature of from 85C to 95C, fl maintaining said crystallization temperature for a period of 20 to 60 minutes, and g) stirring said suspension during the course of steps d) to f) with multistage agitators having a high shearing effect at a circumferential agitator speed of from 5 to 10 meters per second, whereby said low-grit, crystalline, zeolitic sodium aluminosilicate is obtained having a particle size of at least 99.95~ by weight of less than 50~m and a high cation exchanging capacity.
These and other objects of the invention will become more apparent as the description thereof proceeds. -~
The above objects have been achieved by the process of the present invention. The subject matter of the invention is, therefore, a process for the preparation of an aqueous, alkaline suspension of finely-divided, low-grit, crystalline, zeolitic, sodium aluminosilicates of the composition:
0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 with a water content depending on the degree of drying where at least 99.95% by weight have a particle size of less than 50~m and having a high cation exchanging capacity by the process of ~5~
8~
a) continuous mixing of an aqueous sodium ~
aluminate solutdon with an aqueous sodium silicate sQlu-tion in the presence of excess sodium hydroxide solution a1; elevated temperature and b~ subsequent intermittent crystallizing of the aqueous alkaline suspension of the X-ray amorphous, sodium aluminosilicates formed, said suspension having a total composition corresponding to molar ratios of 3 6 to 5 Na2O 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
likewise at elevated temperature, which is characterized in that c) the two reaction components in stage a) are mixed with each other at a temperature not exceeding 50C, d) finely dispersed steam is introduced into the suspension in stage b) in the course of at least 15 minutes under stirring, e) the suspension is heated this way until crystallization temperature in the range of 85 to 95C
has been attained, f) the suspension is left at this crystalliza-tion temperature for a period of 20 to 60 minutes, and g) the suspension is stirred at the same time with multi-stage agitators having a high shearing effect at a circumferential agitator speed of 5 to lO m/s.
More particularly, the present invention relates to an improvement in the process for the production ;~ of aqueous, ~lkaline suspensions of finely divided low-grit, crystalline, zeolitic sodium aluminosilicates of the formula .,, ~ ; . .
0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 with a water content depending upon the degree of drying, and a high cation exchanging capacity comprising the steps of a) continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presence of excess sodium hydroxide solution at elevated temperatures, and . b) subsequently batch crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, said suspension having a total composition of the molar ratios of 3.6 to 5 Na2O : 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
at an elevated temperature the same or higher than the temperature in step a), the improvement consisting essentially of c) conducting said mixing step a) at a temperatur~ above room temperature but not exceeding 50C, d) introducing finely dispersed steam into said aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate for at least 15 minutes while : .
stirring, e) to heat said suspension to a crystallization temperature of from 85C to 95C, f) maintaining said crystallization temperature for a period of 20 to 60 minutes, and g) stirring said suspension during the course o~ steps d) to f) with multistage agitators having a high shearing effect at a circumferential agitator speed of ~`, msA~ .
~8~1~
from 5 to 10 meters per second, whereby said low-grit, crystalline, zeolitic sodium aluminosilicate is obtained having a particle size of at least 99.95% by weight of less than 50~m and a high cation exchanging capacity.
It was found,surprisingly,that maintaining the above-mentioned measures, in the continuous reaction stage, on the one hand, and in the intermittent or batch crystallization stage, on the other hand, leads to the formation of zeolitic sodium aluminosilicates type NaA
with the desired extremely low-grit content of less than 0.05% by weight. This objective is aahieved according to the invention by the cooperation of the parameters sub-stantially influencing the formation of finely-divided zeolite particles, as characterized above in the process features c) to g). In addition, the sodium alumino-silicates thus obtained have a high cation exchanging capacity.
For the first stage of the process according to the invention, hereafter called the precipitation stage, which leads to the formation of an aqueous alkaline suspen-sion of X-ray amorphous, sodium aluminosilicates, those methods generally are used which permit continuous mixing of the reaction partners, sodium aluminate solution and sodium silicate solution, in suitable reactors. Examples of such methods are, for example:
Mixing the components by means of suitable spray nozzles, whereby the reaction partners meet only in the spray jet, with formation of an X-ray amorphous product.
. ~ ~
~1~8~'319 Mixing the components in a mixing zone acting in stages, where one of the two reaction compo-nents is divid~d into sevexal partial currents, one of which is added directly and continuously to the total current of the other reaction com-ponent, and the othe partial currents are added, likewise, continuously downstream to the current of the reaction mixture formed. As a .
mixing zone acting in stages in the foregoing sense, particularly stirring ~essel cascades, stirrer columns with chambers separated by partitions, stepped differential worm mixers and tu~ular reactors, can be used.
The foregoing methods mentioned by way of example are described in detail in the;copending Canadian patent .. . . . . . . . .
applications,Serial No. 342,139 filed Dec mber 18, 1979, now Patent No. 1,109,638; Serial No. 347,661, filed March 14, 1980; and Serial No. 347,662, filed Maxch 14, 1980.
Beyond that all corresponding continuous méthods for the production of X-ray amorphous sodium alumino-silicates can be used according to the invention, provided a precipitation or mixing temperature of not more than 50C is maintained in the precipitation stage. Particu-larly pxeferred in the sense of the invention is miY~ing the reaction components at a temperature in the range of 40 to 50~C.
In order to obtain a zeolitic sodium alumino-silicate type NaA, th?t i5, a zeolite ~ith a composition having the molar ratios of ~ . .
~1~8~9 0.8 to 1.3 Na2O : 1 A12O3 : 1.8 to 2 SiO2 and a water content depending on the degree of drying, the dosage of the reaction components must be so selected in this precipitation stage that the aqueous alkaline suspension of the X-ray amorphous sodium aluminosilicates formed has a total composition corresponding to molar ratios of 3.6 to 5 Na2O : 1 A12O3 : 1.8 to 2 SiO2 : 70 to 105 H2O-In the intermittent or batch crystallization stage following the continuous precipitation stage, the maintenance of additional parameters is of essential importance according to the invention.
The aqueous alkaline suspension of X-ray amorphous sodium aluminosilicates formed in the continuous precipi-tation stage i~ as a rule first transferred to one of several parallel connected crystallization vessels whose number and dimensions should preferably be so selected that they ensure the reception of the continuous suspension current flowing from the continuous precipitation stage.
The intermittent crystallization of the amorphous product then takes place in these crystallization vessels, which should be equipped according to the invention with multi-stage agitators having a high shearing action.
The crystallization process proper is started by heating the suspension, under constant stirring, to the required crystallization temperature. It is of essential importance that the suspension is not heated too fast.
According to the invention, the suspension is heated in the course of at least 15 minutes, preferably in the course of 20 to 30 minutes, until the crystallization ~ c~19 temperature is attained. Furthermore, the manner of heating is also important according to the invention.
It was found that best results are obtained by introducing finely-dispersed steam directly into the suspension in view of obtaining a low-grit content of the resulting crystalline product. The introduction of the finely-dispersed steam into the suspension can be effected,for example, by ring conduits arranged on the bottoms of the respective crystallization vessels and provided with many small orifices. However, other arrangements which ensure direct introduction of finely-dispersed steam into the suspension can also be used, According to the invention, the suspension is heated this way until a temperature of 85 to 95C, preferably 90 to 93C, is attained over the period of at least 15 minutes, preferably over 20 to 30 minutes. The heated suspension is left subsequently at this temperature for 20 to 60 minutes, preferably 30 to 40 minutes, during which time the amorphous product crystallizes to a zeo-litic sodium aluminosilicate, type NaA.
During the entire crystallization process, that is, from the start of heating, the suspension of the amorphous product or the forming crystalline product should be stirred vigorously by means of a multi-stage agitator with a high shearing power. According to the invention, the strength and the intensity of this agitator, that is, the circumferential agitator speed, is 5 to 10 meters per second, preferably to 6 to 8 meters per second.
Agitators that are suita~le for this purpose are, for example, turbines or turbine-like stirring apparatus with multi-stage propellers, which are characterized by a ,: :
strong shearing action. The number of stages of the agitator depends primarily on the geometric form of the selected crystallization vessel. Since the shearing action of these agitators is greatly influenced by the shape of the agitator, it was found particularly advanta-geous in the sense of the invention to stir the suspension with axially moving agitators with a high shearing action, particularly trapezoidal agitators with curved stirring blades.
If the essential features of the process accord-ing to the invention are maintained, particularly in the procedures characterized as preferred, a finely-divided, crystalline zeolitic sodium aluminosilicate, type NaA, is obtained after the crystallization, which is charac-terized by a grit portion of less than 0.05% by weight and high cation exchanging capacity.
For the identification of the crystallization product obtained, samples are filtered off, washed alkali-free, dried overnight in a vacuum drying cabinet at 100C
and identified on the basis of their X-ray diffraction diagram. The particle size distribution is measured as the % by volume distribution of the crystallized particles by means of a Coulter-Counte ~ , for example, model TA.
The grit portion in the crystallized product, that is, the portion of particles with a particle size above 50~um, is determined by a modified wet-screening method according to Mocker, where a weighed sample of the crystalline material suspended with water is placed in a testing apparatus by Mocker (DIN 53 580) on a test screen with a mesh aperture of 50,um (DIN 4188~ and whirled by means of water sprayed from rotating nozzles. The fine 3S~3~9 portions of the crystalline material are flushed this way without pressure through the screen, while the coarse portions (grit) remain on the screen. After 2 minutes, with a spray of 80 liters of water per hour, the test screen is dried in the drying cabinet at 110C and subse-quently, the screenings are determined by a differential weighing. The screenings result from the formula % by weight screenings = (a-b) .100 with a = weight of screen with screenings b = weight of screen without screenings E = weight of sample in gm based on the dry material.
The measure of the cation exchanging capacity of the crystalline zeolitic material i8 the calcium-binding power of 1 gm of sodium aluminosilicate (active sub-stances = AS] per liter in a liter of water with an initial hardness of 30dH (German hardness). For the determination of the calcium-binding power, 1 liter of an aqueous solution containing 0.594 gm of CaC12 (corres-ponding to 300 mg CaO/1=30dH) is adjusted with diluted sodium hydroxide solution to a pH value of 10 and mixed with 1 gm of aluminosilicate ~AS). The suspension formed is subsequently stirred vigorously for 15 minutes at a temperature of 22 + 2C. After the sodium alumino-silicate is filtered off, the residual hardness X in the filtrate is determined by complexometric titration by means of ethylenediamine tetraacetic acid. The calcium-binding power in mg CaO/gm~AS is calculated according to the formula: (30 - X) . 10.
~8~
The suspension of finely-divided, low-grit, crystalline zeolitic sodium aluminosilicates, type NaA, iis~ as a rule, further processed after the crystallization i'3 completed. To this end the crystalline solid substance is filtered off, washed and dried or prepared in any other way, depending on the desired application. Thus, an a~ue-ous suspension of the crystalline, sodium aluminosilicate can also be used, if necessary, for the production of wash-ing and cleaning agents. Mother liquor and wash liquor are preferably returned into the production process.
Due to the great cation-exchanging capacity of the zeolitic sodium aluminosilicate obtained, which mani-fests itself in a calcium-binding power of 150 to 200 mg CaO/gm AS, it is preferably used as a heterogeneous inor-ganic builder (phosphate su~stitute) in detergents, rinses and cleansers~
The f~llowing examples describe the procedure used in the process accoxding tQ the invention but are not limitative thereto.
For the continuous precipitation stage, a vértical agitator column with an effective volume of 188 liters was used, which was divided by partitions into a total of 28 chambers and which was equipped with the same number of MIG agitators. The shaft common to all agi-i tators was driven by means of a corresponding motor at a speed of 390 min 1. The~entire column cylinder was pro-vided with a heating jacket. The reaction components, which had been preheated to a precipitation temperature of 50C, were fed through suitable dosing devices, such as .. . . .
.
~8~3~9 pumps and rotameters, into the bottom chambers of the agi-t:ator column. The movement of the reaction mixture from chamber to chamber was effected through staggered ring slots provided in the partitions, so that a continuously rising product flow was obtained in the column. The dos-ing of the reaction components was: 549 kg/h of sodium silicate solution, 1315 kg/h of sodium aluminate solution, as well as 1136 kg/h of alkaline mother liquor from one of the preceding crystallization stages, the composition of the reaction product formed corresponded to molar ratios of 4.2 Na2O : 1 A12O3 : 1.8 SiO2 : 95 H2O.
The suspension of the amorphous reaction product issuing continuously from the top of the agitator column was gradually transferred into three crystallization vessels with a volume of 6 cu. meters each, which were equipped with two-stage propeller agitators with a high shearing power. As soon as the bottom blade dipped com-pletely into the suspension, the respective agitator was start~ed with a circumferential agitator speed of 6.9 m.s 1. After a crystallization vessel was filled, finely-dispersed steam was injected directly into the suspension under a pressure of 4 bar through a ring conduit arranged on the bottom of each vessel, and the temperature of the suspension was thus increased within 20 minutes to 93C.
The suspension remained at this crystallization tempera-ture for a period of 40 minutes under constant stirring, at a circumferential agitator speed of 6.9 m.s 1.
Su~sequently, the contents of each crystallization vessel was transferred to a filter unit, where the crystalline products obtained were washed and dried, and the resulting .
- . .
mother liquor returned into the precipitation stage of the process.
The crystalline reaction products formed were according to the X-ray diffraction diagram type NaA zeo-lites. The particle size determined with the Coulter-Counter showed a maximum of the particle size distribution of 3 to 5~m. The calcium binding power was 175 mg CaO/gm AS. The grit portion was 0.02~ by weight.
The example was carried ~t in analogy to Example 1 with the following modification:
The molar composition of the reaction mixture was 4 Na2O : 1 A12O3 : 1.8 SiO2 : 105 H2O
A crystalline of type NaA zeolite with a calcium-binding power of 181 mg CaO/gm AS and a grit portion of 0.03% by we~ght, was obtained.
This example was carried out in analogy to Example 1 with the following modification:
The molar composition of the reaction mixture was 4.5 Na2O : 1 A12O3 : 1.8 SiO2 : 95 H2O.
A crystalline of type NaA zeolite with a calcium-binding power of 172 mg CaO/gm AS and a grit portion of 0.03~ by weight, was obtained.
The precipitation stage was carried out in analogy to Example 1. The crystallization stage was carried out in three crystallization vessels which were equipped with different agitators of different , ~ ' '' "-shearing action. In vessels A and B, the stirring was effected with straight-arm paddle agitators at a circum-i-erential speed of less than 5 m.s l. In vessel A, the stirring speed waS3.6 m.slandin vessel B, it was4.5 m.s l.
:[n vessel C, the stirring was effected with an axially moving trapezoidal agitator with curved blades at a circumferential speed of 7.1 m.s 1. The heating rate to the crystallization temperature of 90C was in all three vessels 25 minutes, the following stay period 30 minutes.
Otherwise, we proceeded as described in Example l. The NaA zeolites formed in all cases differed substantially in the following features:
Vessel A B
calciu~bi~ p~wer in mg CaO/gm AS177 171 172 grit portion in % by weight 0.720.08 0.01 The example was carried out as in Example 1 but under the following modified reaction conditions:
precipitation temperature: 44C; heating time: 26 minutes;
subsequent stay period: 30 minutes.
The type NaA zeolites formed had a calcium-binding power oi 169 mg CaO/gm ~S and a grit portion of 0.02% b~ weight.
The following comparison tests, where the criti-cal process features essential for the invention were not maintained, will likewise illustrate the impo~rtance of these features in the grit portion of the zeolites formed.
:
COMP~RISON EXAMPLE 1 This example was carried out as in Example 1 but the reaction components were mixed in the precipita-t:ion stage at a temperature of 65C. Type NaA zeolites were obtained which had a calcium-binding power of 178 mg CaO/gm AS and a grit portion of 0.2% by weight.
CO~PARISON EXAMPLE 2 This example was carried out likewise as in Example 1. The heating in the crystallization vessel of the suspension formed in the precipitation stage was effected, however, within 7 minutes by direct injection of steam by means of a steam lance. The resulting type NaA
zeolites had a calcium~binding power of 174 mg CaO/gm AS
and a grit portion of 0.34% by weight.
Comparison Example 2 was repeated, with the suspension in the crystallization vessel heated slower, within 28 minutes, but likewise ~y direct injection of steam by means of a steam lance. The resulting type NaA
zeolites had a calcium-binding power of 168 mg CaO/gm AS
and a grit portion of 0.2% by weight.
The first comparison tests show the importance of the relatively low precipitation temperature according to the invention. The other two comparison tests show clearly the determinant influence of the heating time, on the one hand, and the manner of heating, without finely-dispersed steam, on the other hand, on the grit content of the crystalline product.
. ~
:
~8~19 The preceding specific embodiments illustrate the practice of the invention. It is to be understood, however, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims.
--19-- :
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the process of the production of aqueous alkaline suspensions of finely divided low-grit, crystalline, zeolitic sodium aluminosilicates of the formula 0.8 to 1.3 Na2O : 1 Al2O3 : 1.8 to 2 SiO2 with a water content depending upon the degree of drying, and a high cation exchanging capacity comprising the steps of a) continuously mixing an aqueous sodium aluminate solution with an aqueous sodium silicate solution in the presence of excess sodium hydroxide solution at elevated temperatures, and b) subsequently batch crystallizing the aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate, so produced, said suspension having a total composition of the molar ratios of 3.6 to 5 Na2O : 1 Al2O3 : 1.8 to 2 SiO2 : 70 to 105 H2O
at an elevated temperature the same or higher than the temperature in step a), the improvement consisting essentially of c) conducting said mixing step a) at a temperature above room temperature but not exceeding 50°C, d) introducing finely dispersed steam into said aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate for at least 15 minutes while stirring, e) to heat said suspension to a crystallization temperature of from 85°C to 95°C, f) maintaining said crystallization temperature for a period of 20 to 60 minutes, and g) stirring said suspension during the course of steps d) to f) with multistage agitators having a high shearing effect at a circumferential agitator speed of from 5 to 10 meters per second, whereby said low-grit, crystalline, zeolitic sodium aluminosilicate is obtained having a particle size of at least 99.95% by weight of less than 50 µm and a high cation exchanging capacity.
.
at an elevated temperature the same or higher than the temperature in step a), the improvement consisting essentially of c) conducting said mixing step a) at a temperature above room temperature but not exceeding 50°C, d) introducing finely dispersed steam into said aqueous alkaline suspension of X-ray amorphous sodium aluminosilicate for at least 15 minutes while stirring, e) to heat said suspension to a crystallization temperature of from 85°C to 95°C, f) maintaining said crystallization temperature for a period of 20 to 60 minutes, and g) stirring said suspension during the course of steps d) to f) with multistage agitators having a high shearing effect at a circumferential agitator speed of from 5 to 10 meters per second, whereby said low-grit, crystalline, zeolitic sodium aluminosilicate is obtained having a particle size of at least 99.95% by weight of less than 50 µm and a high cation exchanging capacity.
.
2. The process of claim 1 wherein said reaction components in step c) are mixed at a temperature of from 40° to 50°C.
3. The process of claim 1 or 2 wherein said finely-dispersed steam in step d) is introduced over a period of 20 to 30 minutes.
4. The process of claim 1 or 2 wherein said suspension in step e) is heated to from 90° to 93°C.
5. The process of claim 1 or 2 wherein said crystallization temperature in step f) is maintained for from 30 to 40 minutes.
6. The process of claim 1 wherein said stirring in step g) is conducted at a circumferential agitator speed of from 6 to 8 meters per second.
7. The process of claim 6 wherein said multiple stage agitators having a high shearing effect in step g) are axially moving agitators.
8. The process of claim 7 wherein said axially moving agitators are trapezoidal agitators with curved blades.
9. The process of claim 1 wherein said intro-ducing finely dispersed steam is effected by introducing the steam through many small orifices.
10. The process of claim 9 wherein said many small orifices are arranged on a ring conduit at the bottom of said batch crystallizing suspension.
11. The process of claim 1 where said steps (d) to (g) are conducted over a period of from 35 to 90 minutes.
12. The process of claim 11 wherein said period is from 50 to 70 minutes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3011834.4 | 1980-03-27 | ||
| DE19803011834 DE3011834A1 (en) | 1980-03-27 | 1980-03-27 | METHOD FOR PRODUCING FINE-PARTICULATE ZEOLITHIC SODIUM ALUMINUM SILICATES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1148919A true CA1148919A (en) | 1983-06-28 |
Family
ID=6098504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000373952A Expired CA1148919A (en) | 1980-03-27 | 1981-03-26 | Process for the production of finely-divided, low grit, zeolitic sodium aluminosilicates |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0037018B1 (en) |
| JP (1) | JPS56155015A (en) |
| AT (1) | ATE19502T1 (en) |
| BR (1) | BR8101827A (en) |
| CA (1) | CA1148919A (en) |
| DE (2) | DE3011834A1 (en) |
| ES (1) | ES500736A0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5474753A (en) * | 1990-11-09 | 1995-12-12 | Laviosa Rhone-Poulenc | Preparation of crystalline 4A zeolites |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4309656A1 (en) * | 1993-03-25 | 1994-09-29 | Henkel Kgaa | Process for the production of very finely divided zeolitic alkali metal aluminum silicates |
| US5989518A (en) * | 1998-12-29 | 1999-11-23 | Uop Llc | Process for synthesizing and controlling the particle size and particle size distribution of a molecular sieve |
| US6656447B1 (en) | 1998-12-29 | 2003-12-02 | Uop Llc | Process for synthesizing and controlling the particle size and particle size distribution of a molecular sieve |
| DE10056362A1 (en) * | 2000-11-14 | 2002-05-29 | Thomas Bein | Synthesis and stabilization of nanoscale zeolite particles |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2447021C3 (en) * | 1974-10-02 | 1984-03-22 | Degussa Ag, 6000 Frankfurt | Type A crystalline zeolite powder and the process for its preparation |
-
1980
- 1980-03-27 DE DE19803011834 patent/DE3011834A1/en not_active Withdrawn
-
1981
- 1981-03-19 DE DE8181102056T patent/DE3174499D1/en not_active Expired
- 1981-03-19 EP EP81102056A patent/EP0037018B1/en not_active Expired
- 1981-03-19 AT AT81102056T patent/ATE19502T1/en not_active IP Right Cessation
- 1981-03-26 BR BR8101827A patent/BR8101827A/en not_active IP Right Cessation
- 1981-03-26 CA CA000373952A patent/CA1148919A/en not_active Expired
- 1981-03-26 ES ES500736A patent/ES500736A0/en active Granted
- 1981-03-27 JP JP4612081A patent/JPS56155015A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5474753A (en) * | 1990-11-09 | 1995-12-12 | Laviosa Rhone-Poulenc | Preparation of crystalline 4A zeolites |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0037018B1 (en) | 1986-04-30 |
| JPH0116769B2 (en) | 1989-03-27 |
| EP0037018A2 (en) | 1981-10-07 |
| DE3011834A1 (en) | 1981-10-01 |
| EP0037018A3 (en) | 1982-09-15 |
| ATE19502T1 (en) | 1986-05-15 |
| JPS56155015A (en) | 1981-12-01 |
| ES8201932A1 (en) | 1982-01-16 |
| BR8101827A (en) | 1981-09-29 |
| DE3174499D1 (en) | 1986-06-05 |
| ES500736A0 (en) | 1982-01-16 |
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